RIFT Working Group A.
Internet Engineering Task Force (IETF) T. Przygienda, Ed.
Internet-Draft
Request for Comments: 9692 J. Head, Ed.
Intended status:
Category: Standards Track Juniper Networks
Expires: 24 November 2024
ISSN: 2070-1721 A. Sharma
Hudson River Trading
P. Thubert
Bruno.
B. Rijsman
Individual
Dmitry.
D. Afanasiev
Yandex
23 May
December 2024
RIFT: Routing in Fat Trees
draft-ietf-rift-rift-24
Abstract
This document defines a specialized, dynamic routing protocol for
Clos, fat tree, Fat Tree, and variants thereof. These topologies were
initially used within crossbar interconnects, interconnects and consequently router
and switch backplanes, but their characteristics make them ideal for
constructing IP fabrics as well. The protocol specified by this
document is optimized toward towards the minimization of control plane state
to support very large substrates as well as the minimization of
configuration and operational complexity to allow for a simplified
deployment of said topologies.
Status of This Memo
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This Internet-Draft will expire on 24 November 2024.
https://www.rfc-editor.org/info/rfc9692.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 8
2. A Reader's Digest . . . . . . . . . . . . . . . . . . . . . . 8
3. Reference Frame . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 10
3.2. Topology . . . . . . . . . . . . . . . . . . . . . . . . 16
4. RIFT: Routing in Fat Trees . . . . . . . . . . . . . . . . . 19
5. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.1. Properties . . . . . . . . . . . . . . . . . . . . . . . 19
5.2. Generalized Topology View . . . . . . . . . . . . . . . . 20
5.2.1. Terminology and Glossary . . . . . . . . . . . . . . 20
5.2.2. Clos as Crossed, Stacked Crossbars . . . . . . . . . 21
5.3. Fallen Leaf Problem . . . . . . . . . . . . . . . . . . . 31
5.4. Discovering Fallen Leaves . . . . . . . . . . . . . . . . 33
5.5. Addressing the Fallen Leaves Problem . . . . . . . . . . 34
6. Specification . . . . . . . . . . . . . . . . . . . . . . . . 35
6.1. Transport . . . . . . . . . . . . . . . . . . . . . . . . 36
6.2. Link (Neighbor) Discovery (LIE Exchange) . . . . . . . . 36
6.2.1. LIE Finite State Machine . . . . . . . . . . . . . . 42
6.3. Topology Exchange (TIE Exchange) . . . . . . . . . . . . 52
6.3.1. Topology Information Elements . . . . . . . . . . . . 52
6.3.2. Southbound and Northbound TIE Representation . . . . 53
6.3.3. Flooding . . . . . . . . . . . . . . . . . . . . . . 56
6.3.4. TIE Flooding Scopes . . . . . . . . . . . . . . . . . 65
6.3.5. RAIN: RIFT Adjacency Inrush Notification . . . . . . 70
6.3.6. Initial and Periodic Database Synchronization . . . . 70
6.3.7. Purging and Roll-Overs . . . . . . . . . . . . . . . 70 Rollovers
6.3.8. Southbound Default Route Origination . . . . . . . . 71
6.3.9. Northbound TIE Flooding Reduction . . . . . . . . . . 72
6.3.10. Special Considerations . . . . . . . . . . . . . . . 77
6.4. Reachability Computation . . . . . . . . . . . . . . . . 78
6.4.1. Northbound Reachability SPF . . . . . . . . . . . . . 79
6.4.2. Southbound Reachability SPF . . . . . . . . . . . . . 80
6.4.3. East-West Forwarding Within a non-ToF Non-ToF Level . . . . . 80
6.4.4. East-West Links Within a ToF Level . . . . . . . . . . 80
6.5. Automatic Disaggregation on Link & Node Failures . . . . 80
6.5.1. Positive, Non-transitive Non-Transitive Disaggregation . . . . . . . 80
6.5.2. Negative, Transitive Disaggregation for Fallen Leaves . . . . . . . . . . . . . . . . . . . . . . . 84
6.6. Attaching Prefixes . . . . . . . . . . . . . . . . . . . 86
6.7. Optional Zero Touch Provisioning (RIFT ZTP) . . . . . . . 94
6.7.1. Terminology . . . . . . . . . . . . . . . . . . . . . 95
6.7.2. Automatic System ID Selection . . . . . . . . . . . . 97
6.7.3. Generic Fabric Example . . . . . . . . . . . . . . . 97
6.7.4. Level Determination Procedure . . . . . . . . . . . . 98
6.7.5. RIFT ZTP FSM . . . . . . . . . . . . . . . . . . . . 100
6.7.6. Resulting Topologies . . . . . . . . . . . . . . . . 105
6.8. Further Mechanisms . . . . . . . . . . . . . . . . . . . 106
6.8.1. Route Preferences . . . . . . . . . . . . . . . . . . 106
6.8.2. Overload Bit . . . . . . . . . . . . . . . . . . . . 107
6.8.3. Optimized Route Computation on Leaves . . . . . . . . 107
6.8.4. Mobility . . . . . . . . . . . . . . . . . . . . . . 108
6.8.5. Key/Value (KV) Store . . . . . . . . . . . . . . . . 111
6.8.6. Interactions with BFD . . . . . . . . . . . . . . . . 112
6.8.7. Fabric Bandwidth Balancing . . . . . . . . . . . . . 113
6.8.8. Label Binding . . . . . . . . . . . . . . . . . . . . 116
6.8.9. Leaf to Leaf Leaf-to-Leaf Procedures . . . . . . . . . . . . . . . 116
6.8.10. Address Family and Multi Topology Multi-Topology Considerations . . 117
6.8.11. One-Hop Healing of Levels with East-West Links . . . 117
6.9. Security . . . . . . . . . . . . . . . . . . . . . . . . 117
6.9.1. Security Model . . . . . . . . . . . . . . . . . . . 117
6.9.2. Security Mechanisms . . . . . . . . . . . . . . . . . 119
6.9.3. Security Envelope . . . . . . . . . . . . . . . . . . 120
6.9.4. Weak Nonces . . . . . . . . . . . . . . . . . . . . . 124
6.9.5. Lifetime . . . . . . . . . . . . . . . . . . . . . . 125
6.9.6. Security Association Changes . . . . . . . . . . . . 125
7. Information Elements Schema . . . . . . . . . . . . . . . . . 125
7.1. Backwards-Compatible Extension of Schema . . . . . . . . 126
7.2. common.thrift . . . . . . . . . . . . . . . . . . . . . . 127
7.3. encoding.thrift . . . . . . . . . . . . . . . . . . . . . 133
8. Further Details on Implementation . . . . . . . . . . . . . . 140
8.1. Considerations for Leaf-Only Implementation . . . . . . . 140
8.2. Considerations for Spine Implementation . . . . . . . . . 141
9. Security Considerations . . . . . . . . . . . . . . . . . . . 141
9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 141
9.2. Time to Live and Hop Limit Values . . . . . . . . . . . . 142
9.3. Malformed Packets . . . . . . . . . . . . . . . . . . . . 142
9.4. RIFT ZTP . . . . . . . . . . . . . . . . . . . . . . . . 143
9.5. Lifetime . . . . . . . . . . . . . . . . . . . . . . . . 143
9.6. Packet Number . . . . . . . . . . . . . . . . . . . . . . 143
9.7. Outer Fingerprint Attacks . . . . . . . . . . . . . . . . 143
9.8. TIE Origin Fingerprint DoS Attacks . . . . . . . . . . . 144
9.9. Host Implementations . . . . . . . . . . . . . . . . . . 144
9.9.1. IPv4 Broadcast and IPv6 All Routers All-Routers Multicast
Implementations . . . . . . . . . . . . . . . . . . . 145
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 145
10.1. Requested Multicast and Port Numbers . . . . . . . . . . 145
10.2. Requested Registry for RIFT Security Algorithms . . . . 146
10.3. Requested Registries with Assigned Values for Schema Values . . . . . . . . . . . . . . . . . . . . . . . . . 147
10.3.1. RIFTVersions Registry RIFT/Versions . . . . . . . . . . . . . . . 148
10.3.2. RIFTCommonAddressFamilyType Registry RIFT/common/AddressFamilyType . . . . . . . 148
10.3.3. RIFTCommonHierarchyIndications Registry RIFT/common/HierarchyIndications . . . . . 149
10.3.4. RIFTCommonIEEE8021ASTimeStampType Registry RIFT/common/IEEE802_1ASTimeStampType . . . 149
10.3.5. RIFTCommonIPAddressType Registry RIFT/common/IPAddressType . . . . . . . . . 150
10.3.6. RIFTCommonIPPrefixType Registry RIFT/common/IPPrefixType . . . . . . . . . 150
10.3.7. RIFTCommonIPv4PrefixType Registry RIFT/common/IPv4PrefixType . . . . . . . . 151
10.3.8. RIFTCommonIPv6PrefixType Registry RIFT/common/IPv6PrefixType . . . . . . . . 151
10.3.9. RIFTCommonKVTypes Registry RIFT/common/KVTypes . . . . . . . . . . . . 152
10.3.10. RIFTCommonPrefixSequenceType Registry RIFT/common/PrefixSequenceType . . . . . . 152
10.3.11. RIFTCommonRouteType Registry RIFT/common/RouteType . . . . . . . . . . . 153
10.3.12. RIFTCommonTIETypeType Registry RIFT/common/TIETypeType . . . . . . . . . . 154
10.3.13. RIFTCommonTieDirectionType Registry RIFT/common/TieDirectionType . . . . . . . 155
10.3.14. RIFTEncodingCommunity Registry RIFT/encoding/Community . . . . . . . . . . 156
10.3.15. RIFTEncodingKeyValueTIEElement Registry RIFT/encoding/KeyValueTIEElement . . . . . 156
10.3.16. RIFTEncodingKeyValueTIEElementContent Registry RIFT/encoding/KeyValueTIEElementContent . . 157
10.3.17. RIFTEncodingLIEPacket Registry RIFT/encoding/LIEPacket . . . . . . . . . . 157
10.3.18. RIFTEncodingLinkCapabilities Registry RIFT/encoding/LinkCapabilities . . . . . . 160
10.3.19. RIFTEncodingLinkIDPair Registry RIFT/encoding/LinkIDPair . . . . . . . . . 161
10.3.20. RIFTEncodingNeighbor Registry RIFT/encoding/Neighbor . . . . . . . . . . 163
10.3.21. RIFTEncodingNodeCapabilities Registry RIFT/encoding/NodeCapabilities . . . . . . 163
10.3.22. RIFTEncodingNodeFlags Registry RIFT/encoding/NodeFlags . . . . . . . . . . 164
10.3.23. RIFTEncodingNodeNeighborsTIEElement Registry RIFT/encoding/NodeNeighborsTIEElement . . . 165
10.3.24. RIFTEncodingNodeTIEElement Registry RIFT/encoding/NodeTIEElement . . . . . . . 166
10.3.25. RIFTEncodingPacketContent Registry RIFT/encoding/PacketContent . . . . . . . . 167
10.3.26. RIFTEncodingPacketHeader Registry RIFT/encoding/PacketHeader . . . . . . . . 168
10.3.27. RIFTEncodingPrefixAttributes Registry RIFT/encoding/PrefixAttributes . . . . . . 169
10.3.28. RIFTEncodingPrefixTIEElement Registry RIFT/encoding/PrefixTIEElement . . . . . . 171
10.3.29. RIFTEncodingProtocolPacket Registry RIFT/encoding/ProtocolPacket . . . . . . . 171
10.3.30. RIFTEncodingTIDEPacket Registry RIFT/encoding/TIDEPacket . . . . . . . . . 171
10.3.31. RIFTEncodingTIEElement Registry RIFT/encoding/TIEElement . . . . . . . . . 172
10.3.32. RIFTEncodingTIEHeader Registry RIFT/encoding/TIEHeader . . . . . . . . . . 173
10.3.33. RIFTEncodingTIEHeaderWithLifeTime Registry RIFT/encoding/TIEHeaderWithLifeTime . . . . 174
10.3.34. RIFTEncodingTIEID Registry RIFT/encoding/TIEID . . . . . . . . . . . . 175
10.3.35. RIFTEncodingTIEPacket Registry RIFT/encoding/TIEPacket . . . . . . . . . . 175
10.3.36. RIFTEncodingTIREPacket Registry RIFT/encoding/TIREPacket . . . . . . . . . 176
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 176
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 177
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 178
13.1.
11.1. Normative References . . . . . . . . . . . . . . . . . . 178
13.2.
11.2. Informative References . . . . . . . . . . . . . . . . . 180
Appendix A. Sequence Number Binary Arithmetic . . . . . . . . . 183
Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 184
B.1. Normal Operation . . . . . . . . . . . . . . . . . . . . 184
B.2. Leaf Link Failure . . . . . . . . . . . . . . . . . . . . 186
B.3. Partitioned Fabric . . . . . . . . . . . . . . . . . . . 187
B.4. Northbound Partitioned Router and Optional East-West Links . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Acknowledgments
Contributors
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 189
1. Introduction
Clos [CLOS] topologies have gained prominence in today's networking,
primarily as a result of the paradigm shift towards a centralized
data-center
data center architecture that is poised to deliver a majority of
computation and storage services in the future. Such networks are
called
commonly called a fat tree/network Fat Tree / network in modern IP fabric
considerations [VAHDAT08] as a homonym to the original definition of
the term [FATTREE]. In most generic terms, and disregarding
exceptions like horizontal shortcuts, those networks are all
variations of a structured design isomorphic to a ranked lattice
where the least upper bound is the "top of the fabric" and links
closer to the top may be "fatter" to guarantee non-blocking bi-sectional
bisectional capacity.
Many builders of such IP fabrics desire a protocol that auto-
configures
autoconfigures itself and deals with failures and mis-configurations misconfigurations
with a minimum amount of human intervention. Such a solution would
allow local IP fabric bandwidth to be consumed in a 'standard component' "standard
component" fashion,
i.e. i.e., provision it much faster and operate it at
much lower costs than today, much like compute or storage is consumed
already.
In looking at the problem through the lens of such IP fabric
requirements, RIFT (Routing Routing in Fat Trees) Trees (RIFT) addresses those challenges
not through an incremental modification of either a link-state
(distributed computation) or distance-vector (diffused computation)
techniques
technique but rather a mixture of both, briefly described as "link-
state towards the spines" and "distance vector towards the leaves".
In other words, "bottom" levels are flooding their link-state
information in the "northern" direction while each node generates
under normal conditions a "default route" and floods it in the
"southern" direction. This type of protocol naturally supports
highly desirable address aggregation. Alas, such aggregation could
drop traffic in cases of misconfiguration or while failures are being
resolved or even cause persistent network partitioning and this has
to be addressed by some adequate mechanism. The approach RIFT takes
is described in Section 6.5 and is based on automatic, sufficient
disaggregation of prefixes in case of link and node failures.
The protocol further provides:
* optional fully automated construction of fat tree Fat Tree topologies based
on detection of links without any configuration (Section 6.7), 6.7)
while allowing for conventional configuration methods or an
arbitrary mix of both,
* the minimum amount of routing state held by nodes,
* automatic pruning and load balancing of topology flooding
exchanges over a sufficient subset of links (Section 6.3.9),
* automatic address aggregation (Section 6.3.8) and consequently
automatic disaggregation (Section 6.5) of prefixes on link and
node failures to prevent traffic loss and suboptimal routing,
* loop-free non-ECMP forwarding due to its inherent valley-free
nature,
* fast mobility (Section 6.8.4),
* re-balancing rebalancing of traffic towards the spines based on bandwidth
available (Section 6.8.7.1), and finally
* mechanisms to synchronize a limited key-value data-store datastore
(Section 6.8.5.1) that can be used after protocol convergence to
e.g. to,
e.g., bootstrap higher levels of functionality on nodes.
Figure 1 illustrates a simplified, conceptual view of a RIFT fabric
with its routing tables and topology databases using IPv4 as the
address family. The top of the fabric's link-state database holds
information about the nodes below it and the routes to them. When
referring to Figure 1, /32 notation corresponds to each node's IPv4
loopback address (e.g. (e.g., A/32 is node A's loopback, etc.) and 0/0
indicates a default IPv4 route. The first row of database
information represents the nodes for which full topology information
is available. The second row of database information indicates that
partial information of other nodes in the same level is also
available. Such information will be needed to perform certain
algorithms necessary for correct protocol operation. When the
"bottom" (or in other words leaves) of the fabric is considered, the
topology is basically empty and, under normal conditions, the leaves
hold a load balanced load-balanced default route to the next level.
The remainder of this document fills in the protocol specification
details.
[A,B,C,D]
[E]
+---------+ +---------+ A/32 @ [C,D]
| E | | F | B/32 @ [C,D]
+-+-----+-+ +-+-----+-+ C/32 @ C
| | | | D/32 @ D
| | | |
| | +--+ |
| | | |
| +---------)--+ |
| | | |
| | | |
| +---------+ | |
| | | |
[A,B] +-+-----+-+ +-+-----+-+ [A,B]
[D] | C | | D | [C]
+-+-----+-+ +-+-----+-+
0/0 @ [E,F] | | | | 0/0 @ [E,F]
A/32 @ [A] | | | | A/32 @ A
B/32 @ [B] | | +--+ | B/32 @ B
| | | |
| +---------)--+ |
| | | |
| +---------+ | |
| | | |
+-+-----+-+ +-+-----+-+
0/0 @ [C,D] | A | | B | 0/0 @ [C,D]
+---------+ +---------+
Figure 1: RIFT Information Distribution
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. A Reader's Digest
This section is an initial guided tour through the document in order
to convey the necessary information for different readers, depending
on their level of interest. The authors recommend reading the HTML
or PDF versions of this document due to the inherent limitation of
text version to represent complex figures.
The Terminology "Terminology" (Section 3.1) section should be used as a
supporting reference as the document is read.
The indications of direction (i.e. (i.e., "top", "bottom", etc.) referenced
in Section 1 are of paramount importance. RIFT requires a topology
with a sense of top and bottom in order to properly achieve a sorted
topology. Clos, Fat Tree, and other similarly structured networks
are conducive to such requirements. Where RIFT does allow allows for further
relaxation of these constraints, this constraints will be mentioned later in this
section.
Several of the images in this document are annotated with "northern
view" or "southern view" to indicate perspective to the reader. A
"northern view" should be interpreted as "from the top of the fabric
looking down", whereas "southern view" should be interpreted as "from
the bottom looking up".
Operators and implementors alike must decide whether multi-plane IP
fabrics are of interest for them. Section 3.2 illustrates an example
of both single-plane in Figure 2 and multi-plane fabric in Figure 3.
Multi-plane fabrics require understanding of additional RIFT concepts
(e.g.
(e.g., negative disaggregation in Section 6.5.2) that are unnecessary
in the context of fabrics consisting of a single-plane only. The
Overview
"Overview" (Section 5) and Section 5.2 "Generalized Topology View" (Section 5.2)
aim to provide enough context to determine if multi-plane fabrics are
of interest to the reader. The
Fallen "Fallen Leaf part Problem" (Section 5.3), 5.3) and
additionally Section Sections 5.4 and
Section 5.5 describe further considerations
that are specific to multi-plane fabrics.
The fundamental protocol concepts are described starting in the
specification part
"Specification" (Section 6), but some sub-sections subsections are less relevant
unless the protocol is being implemented. The protocol transport
(Section 6.1) is of particular importance for two reasons. First, it
introduces RIFT's packet format content in the form of a normative
Thrift [thrift] model given in Section 7.3 7.3, which is carried in an
according security envelope as described in Section 6.9.3. Second,
the Thrift model component is a prerequisite to understanding the
RIFT's inherent security features as defined in both security
models part "Security"
(Section 6.9) and the security segment "Security Considerations" (Section 9). The
normative schema defining the Thrift model can be found in
Section Sections
7.2 and Section 7.3. Furthermore, while a detailed understanding of Thrift
[thrift] and the models model is not required unless implementing RIFT, they
may provide additional useful information for other readers.
If implementing RIFT to support multi-plane topologies topologies, Section 6
should be reviewed in its entirety in conjunction with the previously
mentioned Thrift schemas. Sections not relevant to single-plane
implementations will be noted later in this section.
All readers dealing with implementation of the protocol should pay
special attention to the Link Information Element (LIE) definitions
part
(Section 6.2) as it not only outlines basic neighbor discovery and
adjacency formation, formation but also provides necessary context for RIFT's
optional Zero Touch Provisioning (ZTP) (Section 6.7) and mis-
cabling miscabling
detection capabilities that allow it to automatically detect and
build the underlay topology with basically no configuration. These
specific capabilities are detailed in Section 6.7.
For other readers, the following sections provide a more detailed
understanding of the fundamental properties and highlight some
additional benefits of RIFT RIFT, such as link state link-state packet formats,
efficient flooding, synchronization, loop-free path computation computation, and
link-state database maintenance - Section (see Sections 6.3, Section 6.3.2,
Section 6.3.3, Section
6.3.4, Section 6.3.6, Section 6.3.7,
Section 6.3.8, Section 6.4, Section 6.4.1, Section 6.4.2,
Section 6.4.3, Section 6.4.4. and 6.4.4).
RIFT's ability to perform weighted unequal-cost load balancing of
traffic across all available links is outlined in Section 6.8.7 with
an accompanying example.
Section 6.5 is the place where the single-plane vs. multi-plane
requirement is explained in more detail. For those interested in
single-plane fabrics, only Section 6.5.1 is required. For the multi-
plane interested reader Section
plane-interested reader, Sections 6.5.2, Section 6.5.2.1,
Section 6.5.2.2, and Section
6.5.2.3 are also mandatory. Section 6.6 is especially important for
any multi-plane interested multi-plane-interested reader as it outlines how the RIB (Routing Routing
Information Base) Base (RIB) and FIB (Forwarding Forwarding Information Base) Base (FIB) are
built via the disaggregation mechanisms, mechanisms but also illustrates how they
prevent defective routing decisions that cause traffic loss in both single
single-plane or multi-plane topologies.
Appendix B contains a set of comprehensive examples that show how
RIFT contains the impact of failures to only the required set of
nodes. It should also help cement some of RIFT's core concepts in
the reader's mind.
Last,
Last but not least, RIFT has other optional capabilities. One
example is the key-value data-store, datastore, which enables RIFT to advertise
data post-convergence in order to bootstrap higher levels of
functionality (e.g. (e.g., operational telemetry). Those are covered in
Section 6.8.
More information related to RIFT can be found in the "RIFT
Applicability" [APPLICABILITY] document, which discusses alternate
topologies upon which RIFT may be deployed, describes use cases where
it is applicable, and presents operational considerations that
complement this document. The RIFT DayOne "RIFT Day One" [DayOne] book covers some
practical details of existing RIFT implementations and deployment
details.
3. Reference Frame
3.1. Terminology
This section presents the terminology used in this document.
Bandwidth Adjusted Distance (BAD):
Each RIFT node can calculate the amount of northbound bandwidth
available towards a node compared to other nodes at the same level
and can modify the route distance accordingly to allow for the
lower level to adjust their load balancing towards spines.
Bi-directional
Bidirectional Adjacency:
Bidirectional adjacency is an adjacency where nodes of both sides
of the adjacency advertised it in the Node TIEs with the correct
levels and System IDs. Bi-directionality Bidirectionality is used to check in
different algorithms whether the link should be included.
Bow-tying:
Traffic patterns in fully converged IP fabrics traverse normally traverse
the shortest route based on hop count toward towards their destination
(e.g., leaf, spine, leaf). Some failure scenarios with partial
routing information cause nodes to lose the required downstream
reachability to a destination and force traffic to utilize routes
that traverse higher levels in the fabric in order to turn south
again using a different route to resolve reachability (e.g., leaf,
spine-1, super-spine, spine-2, leaf).
Clos/Fat
Clos / Fat Tree:
This document uses the terms Clos "Clos" and Fat Tree "Fat Tree" interchangeably
where it always refers to a folded spine-and-leaf topology with
possibly multiple Points of Delivery (PoDs) and one or multiple
Top of Fabric (ToF) planes. Several modifications such as leaf-
2-leaf
to-leaf shortcuts and multiple level shortcuts that span multiple levels are
possible and described further in the document.
Cost:
A natural number without a unit associated with two entities. The
usual natural numbers algebra can be applied to costs. A cost may
be associated with either a single link or prefix prefix, or it may
represent the sum of costs (distance) of links in the path between
two nodes.
Crossbar:
Physical arrangement of ports in a switching matrix without
implying any further scheduling or buffering disciplines.
Directed Acyclic Graph (DAG):
A finite directed graph with no directed cycles (loops). If links
in a Clos are considered as either being all directed towards the
top or vice versa, each of such two such graphs is a DAG.
Disaggregation:
Process
The process in which a node decides to advertise more specific
prefixes Southwards, southwards, either positively to attract the
corresponding traffic, traffic or negatively to repel it. Disaggregation
is performed to prevent traffic loss and suboptimal routing to the
more specific prefixes.
Distance:
The sum of costs (bound by the infinite cost constant) between two
nodes. A distance is primarily used to express separation between
two entities and can be used again as cost in another context.
East-West (E-W) Link:
A link between two nodes at the same level. East-West links are
normally not part of Clos or "fat tree" Fat Tree topologies.
Flood Repeater (FR):
A node can designate one or more northbound neighbor nodes to be
flood repeaters. The flood repeaters are responsible for flooding
northbound TIEs further north. The document sometimes calls them
flood leaders as well.
Folded Spine-and-Leaf:
In case the Clos fabric input and output stages are equivalent,
the fabric can be "folded" to build a "superspine" or top top, which
is called the ToF in this document.
Interface:
A layer 3 entity over which RIFT control packets are exchanged.
Key Value (KV) TIE:
A TIE that is carrying a set of key value pairs [DYNAMO]. It can
be used to distribute non topology related non-topology-related information within the
protocol.
Leaf-to-Leaf Shortcuts (L2L): (L2L) Shortcuts:
East-West links at leaf level will need to be differentiated from
East-West links at other levels.
Leaf:
A node without southbound adjacencies. Level 0 implies a leaf in
RIFT
RIFT, but a leaf does not have to be level 0.
Level:
Clos and Fat Tree networks are topologically partially ordered
graphs
graphs, and 'level' "level" denotes the set of nodes at the same height in
such a network. Nodes at the top level (i.e., ToF) are at the
level with the highest value and count down to the nodes at the
bottom level (i.e., leaf) with the lowest value. A node will have
links to nodes one level down and/or one level up. In some
circumstances, a node may have links to other nodes at the same
level. A leaf node may also have links to nodes multiple levels
higher. In RIFT, Level level 0 always indicates that a node is a leaf, leaf
but does not have to be level 0. Level values can be configured
manually or automatically derived via as described in Section 6.7. As a final
footnote: Clos terminology often uses the concept of "stage", but
due to the folded nature of the Fat Tree Tree, it is not used from this
point on to prevent misunderstandings.
LIE:
This is an acronym for a "Link Information Element" exchanged on
all the system's links running RIFT to form _ThreeWay_ adjacencies
and carry information used to perform RIFT Zero Touch Provisioning
(ZTP) of levels.
Metric:
Used interchangeably with cost. "cost".
Neighbor:
Once a _ThreeWay_ adjacency has been formed formed, a neighborship
relationship contains the neighbor's properties. Multiple
adjacencies can be formed to a remote node via parallel point-to-
point interfaces interfaces, but such adjacencies are *not* sharing a
neighbor structure. Saying "neighbor" is thus equivalent to
saying "a _ThreeWay_ adjacency".
Node TIE:
This stands as is an acronym for a "Node Topology Information Element",
which contains all adjacencies the node discovered and information
about the node itself. Node TIE should not be confused with a
North TIE since "node" defines the type of TIE rather than its
direction. Consequently, North Node TIEs and South Node TIEs
exist.
North SPF (N-SPF):
A reachability calculation that is progressing northbound, as
example for
example, SPF that is using South Node TIEs only. Normally it
progresses by only a single hop only and installs default routes.
Northbound Link:
A link to a node one level up or or, in other words, one level
further north.
Northbound representation:
Subset Representation:
The subset of topology information flooded towards higher levels
of the fabric.
Overloaded:
Applies to a node advertising the _overload_ attribute as set.
Overload
The overload attribute is carried in the _NodeFlags_ object of the
encoding schema.
Point of Delivery (PoD):
A self-contained vertical slice or subset of a Clos or Fat Tree
network containing normally containing only level 0 and level 1 nodes. A
node in a PoD communicates with nodes in other PoDs via the ToF
nodes. PoDs are numbered to distinguish them them, and PoD value 0
(defined later in the encoding schema as _common.default_pod_) is
used to denote "undefined" or "any" PoD.
Prefix TIE:
This is an acronym for a "Prefix Topology Information Element" Element",
and it contains all prefixes directly attached to this node in
case of a North TIE and in case of South TIE the necessary default routes the node
advertises southbound. southbound in case of a South TIE.
Radix:
A radix of a switch is the number of switching ports it provides.
It's sometimes called fanout "fanout" as well.
Routing on the Host (RotH):
Modern
A modern data center architecture variant where servers/leaves are
multi-homed
multihomed and consequently participate in routing.
Security Envelope:
RIFT packets are flooded within an authenticated security envelope
that allows to protect the integrity of information a node accepts
if any of the mechanisms in Section 10.2 is are used. This is
further described in Section 6.9.3.
Shortest-Path
Shortest Path First (SPF):
A well-known graph algorithm attributed to Dijkstra [DIJKSTRA]
that establishes a tree of shortest paths from a source to
destinations on the graph. The SPF acronym is used due to its
familiarity as a general term for the node reachability
calculations RIFT can employ to ultimately calculate routes routes, of
which Dijkstra Dijkstra's algorithm is a possible one.
South Reflection:
Often abbreviated just as "reflection", it defines a mechanism
where South Node TIEs are "reflected" from the level south back up
north to allow nodes in the same level without E-W links to be
aware of each other's node Topology Information Elements (TIEs).
South SPF (S-SPF):
A reachability calculation that is progressing southbound, as
example for
example, SPF that is using North Node TIEs only.
South/Southbound and North/Northbound (Direction):
When describing protocol elements and procedures, in different
situations
situations, the directionality of the compass is used. used, i.e.,
'lower', 'south' or 'southbound'
"lower", "south", and "southbound" mean moving towards the bottom
of the Clos or Fat Tree network and 'higher', 'north' "higher", "north", and
'northbound'
"northbound" mean moving towards the top of the Clos or Fat Tree
network.
Southbound Link:
A link to a node one level down or or, in other words, one level
further south.
Southbound representation:
Subset Representation:
The subset of topology information sent towards a lower level.
Spine:
Any nodes north of leaves and south of ToF nodes. Multiple layers
of spines in a PoD are possible.
Superspine, Aggregation/Spine Aggregation/Spine, and Edge/Leaf Switches:" Switches:
Traditional level names in 5-stages 5 stages folded Clos for Level levels 2, 1 1,
and
0 0, respectively (counting up from the bottom). We normalize
this language to talk about ToF, Top-of-Pod (ToP) (ToP), and leaves.
System ID:
RIFT nodes identify themselves with a unique network-wide number
when trying to build adjacencies or describe their topology. RIFT
System IDs can be auto-derived or configured.
ThreeWay Adjacency:
RIFT tries to form a unique adjacency between two nodes over a
point-to-point interface and exchange local configuration and
necessary RIFT ZTP information. An adjacency is only advertised
in Node TIEs and used for computations after it achieved
_ThreeWay_ state, i.e. i.e., both routers reflected each other in LIEs LIEs,
including relevant security information. Nevertheless, LIEs
before _ThreeWay_ state is reached may already carry RIFT ZTP related information already.
related to RIFT ZTP.
TIDE:
The Topology Information Description Element carrying carries descriptors
of the TIEs stored in the node.
TIE:
This is an acronym for a "Topology Information Element". TIEs are
exchanged between RIFT nodes to describe parts of a network such
as links and address prefixes. A TIE has always has a direction and a
type. North TIEs (sometimes abbreviated as N-TIEs) are used when
dealing with TIEs in the northbound representation representation, and South-TIEs
are used (sometimes abbreviated as S-TIEs) for the southbound
equivalent. TIEs have different types types, such as node and prefix
TIEs.
TIEDB:
The database holding the newest versions of all TIE headers (and
the corresponding TIE content if it is available).
TIRE:
The Topology Information Request Element carrying carries a set of TIDE
descriptors. It can both confirm received and request missing
TIEs.
Top of Fabric (ToF):
The set of nodes that provide inter-PoD communication and have no
northbound adjacencies, i.e. i.e., are at the "very top" of the fabric.
ToF nodes do not belong to any PoD and are assigned the
_common.default_pod_ PoD value to indicate the equivalent of "any"
PoD.
Top of PoD (ToP):
The set of nodes that provide intra-PoD communication and have
northbound adjacencies outside of the PoD, i.e. i.e., are at the "top"
of the PoD.
ToF Plane or Partition:
In large fabrics fabrics, ToF switches may not have enough ports to
aggregate all switches south of them them, and with that, the ToF is
'split'
"split" into multiple independent planes. Section 5.2 explains
the concept in more detail. A plane is a subset of ToF nodes that
are aware of each other through south reflection or E-W links.
Valid LIE:
LIEs undergo different checks to determine their validity. The
term "valid LIE" is used to describe a LIE that can be used to
form or maintain an adjacency. The amount of checking itself
depends on the FSM (Finite Finite State Machine) Machine (FSM) involved and its state.
A "minimally valid LIE" is a LIE that passes checks necessary on
any FSM in any state. A "ThreeWay valid LIE" is a LIE that
successfully underwent further checks with a LIE FSM in _ThreeWay_
state. Minimally A minimally valid LIE is a subcategory of a _ThreeWay_
valid LIE.
RIFT Zero Touch Provisioning (abbreviated as RIFT ZTP or just
ZTP):
Optional
An optional RIFT mechanism which that allows the automatic derivation of
node levels based on minimum configuration configuration, as detailed in
Section 6.7. Such a mininum minimum configuration consists solely of ToFs
being configured as such. RIFT ZTP contains a recommendation for
automatic collision-free derivation of the System ID as well.
Additionally, when the specification refers to elements of packet
encoding or the constants provided in the Section 7 7, a special emphasis
is used, e.g. e.g., _invalid_distance_. The same convention is used when
referring to finite state machine states or events outside the
context of the machine itself, e.g., _OneWay_.
3.2. Topology
^ N +--------+ +--------+
Level 2 | |ToF 21| |ToF 22|
W <-*-> E ++-+--+-++ ++-+--+-++
| | | | | | | | |
S v P111/2 P121/2 | | | |
^ ^ ^ ^ | | | |
| | | | | | | |
+--------------+ | +-----------+ | | | +---------------+
| | | | | | | |
South +-----------------------------+ | | ^
| | | | | | | All
0/0 0/0 0/0 +-----------------------------+ TIEs
v v v | | | | |
| | +-+ +<-0/0----------+ | |
| | | | | | | |
+-+----++ optional +-+----++ ++----+-+ ++-----++
Level 1 | | E/W link | | | | | |
|Spin111+----------+Spin112| |Spin121| |Spin122|
+-+---+-+ ++----+-+ +-+---+-+ ++---+--+
| | | South | | | |
| +---0/0--->-----+ 0/0 | +----------------+ |
0/0 | | | | | | |
| +---<-0/0-----+ | v | +--------------+ | |
v | | | | | | |
+-+---+-+ +--+--+-+ +-+---+-+ +---+-+-+
Level 0 | | (L2L) | | | | | |
|Leaf111+~~~~~~~~~~+Leaf112| |Leaf121| |Leaf122|
+-+-----+ +-+---+-+ +--+--+-+ +-+-----+
+ + \ / + +
Prefix111 Prefix112 \ / Prefix121 Prefix122
multi-homed
multihomed
Prefix
+---------- PoD 1 ---------+ +---------- PoD 2 ---------+
Figure 2: A Three Level Three-Level Spine-and-Leaf Topology
____________________________________________________________________________
| [Plane A] . [Plane B] . [Plane C] . [Plane D] |
|..........................................................................|
| +-+ . +-+ . +-+ . +-+ |
| |n| . |n| . |n| . |n| |
| +++ . +++ . +++ . +++ |
| . | | . . | | . . | | . . | | |
| . | | . . | | . . | | . . | | |
| +-+ | | . +-+ | | . +-+ | | . +-+ | | |
| |1| +-+ | . |1| +-+ | . |1| +-+ | . |1| +-+ | |
| +++ | | . +++ | | . +++ | | . +++ | | |
| || | | . || | | . || | | . || | | |
| || | | . || | | . || | | . || | | |
| |+--|--+| . |+--|--+| . |+--|--+| . |+--|----+ |
| | | || . | | || . | | || . | | || |
| | | || . | | || . | | || . | | +|---+ |
=====|===|==||=========|===|==||=========|===|==||=========|===|====|===|=== |
/ | | | || . | | || . | | || . | | / | | / |
/ | | | || . | | || . | | || . | | / ++---++ / |
/ | | | || . | | || . | | || . | | / | n | / |
/ | | | || . | | || . | | || . | | / +++-+++ / |
/ | ++---++ || . ++---++ || . ++---++ || . ++---++/ / |
/ | | 1 | || . | 2 | || . | 3 | || . | 4 |/ / |
/ | +++-+++ || . +++-+++ || . +++-+++ || . +++-+++/ / |
/ | || || || . || || || . || || || . || || / / |
/ \__||_||_____________||_||_____________||_||_____________||_||_/_________/_/
/ || || || || || || || || / || || /
/ || || +-----------+| || || || || || / || || /
/ || || |+-----------|-||-------------+| || || || / || || /
/ || || ||+----------|-||--------------|-||-------------+| || / || || /
/ || || ||| | || | || +-------+ || / || || /
/ || || ||| | |+--------------|-||------|---+ || / || || /
/ || || ||| | | | || | | +-+| / || || /
/ || || ||| | +-----------+ | || | | | | / || || /
/ || +|-|||----------|------------+| | |+------|---|---|-+| / || || /
/ || +-|||----------|------------||---|-|-------|-+ | | || / || || /
/ || ||| | +------||---+ | | | | | || / || || /
/ |+----|||-----+ | |+-----||-----|-------+ | | | || / || || /
/ | ||| | | || || | | | | || / || || /
/ | ||| | | || || | +----|-|---+ || / || || /
/ | ||| | | || || | | | | || / || || /
/ |+----+|| | | || || | | | | || / || || /
/ || +---+| | | +---+| |+---+ | | | +---+ || / +++-+++ /
/ || |+---+ +---+| |+---+ +---+| |+---+ +----+| || / | n | /
/ || || || || || || || || / +++-+++ /
/ +++-+++ +++-+++ +++-+++ +++-+++/=========/
/ | 1 | | 2 + | 3 | . . . | n |/ ^^
/ +++-+++ +-----+ +-----+ +-----+/ //
/ / PoDs
================================================================== //
Figure 3: Topology with Multiple Planes
The topology in Figure 2 is referred to in all further
considerations. This figure depicts a generic "single plane fat
tree" Fat
Tree" and the concepts explained using three levels apply by
induction to further levels and higher degrees of connectivity.
Further, this document will deal also deal with designs that provide only
sparser connectivity and "partitioned spines" spines", as shown in Figure 3
and explained further in Section 5.2.
4. RIFT: Routing in Fat Trees
The remainder of this document presents the detailed specification of
the RIFT protocol, which in the most abstract terms has many
properties of a modified link-state protocol when distributing
information northbound and a distance vector distance-vector protocol when
distributing information southbound. While this is an unusual
combination, it does quite naturally exhibit desired properties.
5. Overview
5.1. Properties
The most singular property of RIFT is that it only floods link-state
information northbound only so that each level obtains the full topology
of levels south of it. Link-State information is, with some
exceptions, not flooded East-West nor back South south again. Exceptions
like south reflection is explained in detail in Section 6.5.1 6.5.1, and
east-west flooding at the ToF level in multi-plane fabrics is
outlined in Section 5.2. In the southbound direction, the necessary
routing information required (normally just a default route as per
Section 6.3.8) only propagates one hop south. Those nodes then
generate their own routing information and flood it south to avoid
the overhead of building an update per adjacency. For the moment moment,
describing the East-West direction is left out until later in the
document.
Those information flow constraints create not only an anisotropic
protocol (i.e. (i.e., the information is not distributed "evenly" or
"clumped" but summarized along the N-S north-south gradient) but also a
"smooth" information propagation where nodes do not receive the same
information from multiple directions at the same time. Normally,
accepting the same reachability on any link, without understanding
its topological significance, forces tie-breaking on some kind of
distance function. And such tie-breaking leads ultimately leads to hop-by-
hop forwarding by shortest paths only. In contrast to that, RIFT,
under normal conditions, does not need to tie-break the same
reachability information from multiple directions. Its computation
principles (south forwarding direction is always preferred) leads lead to
valley-free [VFR] forwarding behavior. In the shortest terms, valley
free
valley-free paths allow reversal of direction at most once from a packet heading
northbound to southbound while permitting traversal of horizontal
links in the northbound phase. phase at most once. Those principles
guarantee loop-free forwarding and with that can take advantage of
all such feasible paths on a fabric. This is another highly
desirable property if available bandwidth should be utilized to the
maximum extent possible.
To account for the "northern" and the "southern" information split split,
the link state database is partitioned accordingly into "north
representation" and "south representation" Topology Information
Elements (TIEs). In the simplest terms terms, the North TIEs contain a link
state
link-state topology description of lower levels and South TIEs carry simply
carry a node description of the level above and default routes
pointing north. This oversimplified view will be refined gradually
in the following sections while introducing protocol procedures and
state machines at the same time.
5.2. Generalized Topology View
This section and resulting Section 6.5.2 are dedicated to multi-plane fabrics,
in contrast with the single plane designs where all ToF nodes are
topologically equal and initially connected to all the switches at
the level below them.
Multi-plane
The multi-plane design is effectively a multi-dimensional multidimensional switching
matrix. To make that easier to visualize, this document introduces a
methodology depicting the connectivity in two-dimensional pictures.
Further, it can be leveraged that what is under consideration here
are is
basically stacked crossbar fabrics where ports align "on top of each
other" in a regular fashion.
A word of caution to the reader; at reader: At this point point, it should be observed
that the language used to describe Clos variations, especially in
multi-plane designs, varies widely between sources. This description
follows the terminology introduced in Section 3.1. This terminology
is needed to follow the rest of this section correctly.
5.2.1. Terminology and Glossary
This section describes the terminology and abbreviations used in the
rest of the text. Though the glossary may not be clear on a first
read, the following sections will introduce the terms in their proper
context.
P:
Denotes the number of PoDs in a topology.
S:
Denotes the number of ToF nodes in a topology.
K:
To simplify the visual aids, notations notations, and further
considerations, the assumption is made that the switches are
symmetrical, i.e., they have an equal number of ports pointing
northbound and southbound. With that simplification, K denotes
half of the radix of a symmetrical switch, meaning that the switch
has K ports pointing north and K ports pointing south. K_LEAF (K
of a leaf) thus represents both the number of access ports in a
leaf Node node and the maximum number of planes in the fabric, whereas
K_TOP (K of a ToP) represents the number of leaves in the PoD and
the number of ports pointing north in a ToP Node towards a higher
spine level and thus the number of ToF nodes in a plane.
ToF Plane:
Set of ToFs that are aware of each other by means of south
reflection. Planes are designated by capital letters, e.g. e.g., plane
A.
N:
Denotes the number of independent ToF planes in a topology.
R:
Denotes a redundancy factor, i.e., the number of connections a
spine has towards a ToF plane. In a single plane design design, K_TOP is
equal to R.
Fallen Leaf:
A fallen leaf in a plane Z is a switch that lost all connectivity
northbound to Z.
5.2.2. Clos as Crossed, Stacked Crossbars
The typical topology for which RIFT is defined is built of P number
of PoDs and connected together by S number of ToF nodes. A PoD node
has K number of ports. From here on on, half of them (K=Radix/2) are
assumed to connect host devices from the south, and the other half is
assumed to connect to interleaved PoD Top-Level top-level switches to the
north. The K ratio can be chosen differently without loss of
generality when port speeds differ or the fabric is oversubscribed oversubscribed,
but K=Radix/2 allows for more readable representation whereby there
are as many ports facing north as south on any intermediate node. A
node is hence represented in a schematic fashion with ports "sticking
out" to its north and south south, rather than by the usual real-world
front faceplate designs of the day.
Figure 4 provides a view of a leaf node as seen from the north, i.e. i.e.,
showing ports that connect northbound. For lack of a better symbol,
the document chooses to use the "o" as ASCII visualisation visualization of a
single port. In this example, K_LEAF has 6 ports. Observe that the
number of PoDs is not related to the Radix unless the ToF Nodes nodes are
constrained to be the same as the PoD nodes in a particular
deployment.
Top view View
+---+
| |
| O o | e.g., Radix = 12, K_LEAF = 6
| |
| O o |
| | -------------------------
| o <------ Physical Port (Ethernet) ----+
| | ------------------------- |
| O o | |
| | |
| O o | |
| | |
| O o | |
| | |
+---+ v
|| || || || || || ||
+----+ +------------------------------------------------+
| | | |
+----+ +------------------------------------------------+
|| || || || || || ||
Side views Views
Figure 4: A Leaf Node, K_LEAF=6
The Radix of a PoD's top node may be different than that of the leaf
node. Though, more often than not, a same type of node is used for
both, effectively forming a square (K*K). In the general case,
switches at the top of the PoD with K_TOP southern ports not
necessarily equal to K_LEAF could be considered . For instance, in
the representations below, we pick a 6 port 6-port K_LEAF and an 8 port 8-port
K_TOP. In order to form a crossbar, K_TOP Leaf Nodes leaf nodes are necessary
as illustrated in Figure 5.
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| | | | | | | | | | | | | | | |
| O | | O | | O | | O | | O | | O | | O | | O |
| | | | | | | | | | | | | | | |
| O | | O | | O | | O | | O | | O | | O | | O |
| | | | | | | | | | | | | | | |
| O | | O | | O | | O | | O | | O | | O | | O |
| | | | | | | | | | | | | | | |
| O | | O | | O | | O | | O | | O | | O | | O |
| | | | | | | | | | | | | | | |
| O | | O | | O | | O | | O | | O | | O | | O |
| | | | | | | | | | | | | | | |
| O | | O | | O | | O | | O | | O | | O | | O |
| | | | | | | | | | | | | | | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
Figure 5: Southern View of Leaf Nodes of a PoD, K_TOP=8
As further visualized in Figure 6 6, the K_TOP Leaf Nodes leaf nodes are fully
interconnected with the K_LEAF ToP nodes, providing connectivity that
can be represented as a crossbar when "looked at" from the north.
The result is that, in the absence of a failure, a packet entering
the PoD from the north on any port can be routed to any port in the
south of the PoD and vice versa. And that is precisely why it makes
sense to talk about a "switching matrix".
W <---*---> E
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| | | | | | | | | | | | | | | |
+--------------------------------------------------------+
| o o o o o o o o |
+--------------------------------------------------------+
+--------------------------------------------------------+
| o o o o o o o o |
+--------------------------------------------------------+
+--------------------------------------------------------+
| o o o o o o o o |
+--------------------------------------------------------+
+--------------------------------------------------------+
| o o o o o o o o |
+--------------------------------------------------------+
+--------------------------------------------------------+
| o o o o o o o o |<--+
+--------------------------------------------------------+ |
+--------------------------------------------------------+ |
| o o o o o o o o | |
+--------------------------------------------------------+ |
| | | | | | | | | | | | | | | | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ |
^ |
| |
| ---------- ----------------------- |
+----- Leaf Node Top-of-PoD Node (Spine) --+
---------- -----------------------
Figure 6: Northern View of a PoD's Spines, K_TOP=8
Side views of this PoD is illustrated in Figure Figures 7 and Figure 8.
Connecting to Spine Nodes
|| || || || || || || ||
+----------------------------------------------------------------+ N
| Top-of-PoD Node (Sideways) | ^
+----------------------------------------------------------------+ |
|| || || || || || || || *
+----+ +----+ +----+ +----+ +----+ +----+ +----+ +----+ |
|Leaf| |Leaf| |Leaf| |Leaf| |Leaf| |Leaf| |Leaf| |Leaf| v
|Node| |Node| |Node| |Node| |Node| |Node| |Node| |Node| S
+----+ +----+ +----+ +----+ +----+ +----+ +----+ +----+
|| || || || || || || ||
Connecting to Client Nodes
Figure 7: Side View of a PoD, K_TOP=8, K_LEAF=6
Connecting to Spine Nodes
|| || || || || ||
+----+ +----+ +----+ +----+ +----+ +----+ N
|ToP | |ToP | |ToP | |ToP | |ToP | |ToP | ^
|Node| |Node| |Node| |Node| |Node| |Node| |
+----+ +----+ +----+ +----+ +----+ +----+ *
|| || || || || || |
+------------------------------------------------+ v
| Leaf Node (Sideways) | S
+------------------------------------------------+
Connecting to Client Nodes
Figure 8: Other Side View of a PoD, K_TOP=8, K_LEAF=6, 90-Degree
Turn in E-W Plane from the Previous Figure
As a next step, observe that a resulting PoD can be abstracted as a
bigger node with a number K of K_POD= K_POD = K_TOP * K_LEAF, and the design
can recurse.
It will be critical at this point that, before progressing further,
the concept and the picture of "crossed crossbars" is understood.
Else, the following considerations might be difficult to comprehend.
To continue, the PoDs are interconnected with each other through a
ToF node at the very top or the north edge of the fabric. The
resulting ToF is *not* partitioned if, if and only if (IIF), (IIF) every PoD
top level
top-level node (spine) is connected to every ToF Node. node. This topology
is also referred to as a single plane configuration and is quite
popular due to its simplicity. In order to reach a 1:1 connectivity
ratio between the ToF and the leaves, it results that there There are K_TOP ToF nodes, nodes and K_LEAF
ToP nodes because each port of a ToP node connects to a different ToF node, and K_LEAF ToP nodes for the same reason.
node. Consequently, it will take at least (P P * K_LEAF) K_LEAF ports on a ToF
node to connect to each of the K_LEAF ToP nodes of the P PoDs.
Figure 9 illustrates this, looking at P=3 PoDs from above and 2
sides. The large view is the one from above, with the 8 ToF of 3*6 3 * 6
ports each interconnecting the PoDs, PoDs and every ToP Node being
connected to every ToF node.
[ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] <-----+
| | | | | | | | |
[=================================] | --------------
| | | | | | | | +----- ToF
[ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] +----- Node ---+
| -------------- |
| v
+-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ <-----+ +-+
| | | | | | | | | | | | | | | | | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] ------------------------- | |
[ |o| |o| |o| |o| |o| |o| |o| |o<--- Physical Port (Ethernet) | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] ------------------------- | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | |
| | | | | | | | | | | | | | | | | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] ---------- | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] <--- ToP Node --------+ | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] (Spine) | | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] ---------- | | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | | |
| | | | | | | | | | | | | | | | -+ +- +-+ v | |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | | --| |--[ ]--| |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | ----- | --| |--[ ]--| |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] +--- PoD ---+ --| |--[ ]--| |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | ----- | --| |--[ ]--| |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | | --| |--[ ]--| |
[ |o| |o| |o| |o| |o| |o| |o| |o| ] | | --| |--[ ]--| |
| | | | | | | | | | | | | | | | -+ +- +-+ | |
+-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
Figure 9: Fabric Spines and TOFs ToFs in Single Plane Design, 3 PoDs
The top view can be collapsed into a third dimension where the hidden
depth index is representing the PoD number. One PoD can be shown
then as a class of PoDs and hence save one dimension in the
representation. The Spine Node spine node expands in the depth and the vertical
dimensions, whereas the PoD top level Nodes top-level nodes are constrained, constrained in the
horizontal dimension. A port in the 2-D representation represents effectively
represents the class of all the ports at the same position in all the
PoDs that are projected in its position along the depth axis. This
is shown in Figure 10.
/ / / / / / / / / / / / / / / /
/ / / / / / / / / / / / / / / /
/ / / / / / / / / / / / / / / /
/ / / / / / / / / / / / / / / / ]
+-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+ ]]
| | | | | | | | | | | | | | | | ] -----------------------
[ |o| |o| |o| |o| |o| |o| |o| |o| ] <-- Top of PoD Node (Spine)
[ |o| |o| |o| |o| |o| |o| |o| |o| ] -----------------------
[ |o| |o| |o| |o| |o| |o| |o| |o| ]]]]
[ |o| |o| |o| |o| |o| |o| |o| |o| ]]] ^^
[ |o| |o| |o| |o| |o| |o| |o| |o| ]] // PoDs
[ |o| |o| |o| |o| |o| |o| |o| |o| ] // (depth)
| |/| |/| |/| |/| |/| |/| |/| |/ //
+-+ +-+ +-+/+-+/+-+ +-+ +-+ +-+ //
^
| --------
+----- ToF Node
--------
Figure 10: Collapsed Northern View of a Fabric for Any Number of PoDs
As simple as a single plane deployment is, it introduces a limit due
to the bound on the available radix of the ToF nodes that has to be
at least P * K_LEAF. Nevertheless, it will become clear that a
distinct advantage of a connected or non-partitioned ToF is that all
failures can be resolved by simple, non-transitive, positive
disaggregation (i.e., nodes advertising more specific prefixes with
the default to the level below them that is, however, is not propagated further
down the fabric) as described in Section 6.5.1 . 6.5.1. In other words, non-partitioned non-
partitioned ToF nodes can always reach nodes below or withdraw the
routes from PoDs they cannot reach unambiguously. And with this,
positive disaggregation can heal all failures and still allow all the
ToF nodes to be aware of each other via south reflection.
Disaggregation will be explained in further detail in Section 6.5.
In order to scale beyond the "single plane limit", the ToF can be
partitioned into N number of identically wired planes where N is an
integer divider of K_LEAF. The 1:1 ratio and the desired symmetry
are still served, this time with (K_TOP * N) (K_TOP*N) ToF nodes, each of (P *
K_LEAF / N)
(P*K_LEAF/N) ports. N=1 represents a non-partitioned Spine Spine, and
N=K_LEAF is a maximally partitioned Spine. Further, if R is any
integer divisor of K_LEAF, then N=K_LEAF/R is a feasible number of
planes and R is a redundancy factor that denotes the number of
independent paths between 2 leaves within a plane. It proves
convenient for deployments to use a radix for the leaf nodes that is
a power of 2 so they can pick a number of planes that is a lower
power of 2. The example in Figure 11 splits the Spine in 2 planes
with a redundancy factor of R=3, meaning that there are 3 non-
intersecting paths between any leaf node and any ToF node. A ToF
node must have, in this case, at least 3*P ports, ports and be directly
connected to 3 of the 6 ToP nodes (spines) in each PoD. The ToP
nodes are represented horizontally with K_TOP=8 ports northwards
each.
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
+-| |--| |--| |--| |--| |--| |--| |--| |-+
| | O | | O | | O | | O | | O | | O | | O | | O | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+
+-| |--| |--| |--| |--| |--| |--| |--| |-+
| | O | | O | | O | | O | | O | | O | | O | | O | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+
+-| |--| |--| |--| |--| |--| |--| |--| |-+
| | O | | O | | O | | O | | O | | O | | O | | O | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
Plane 1
----------- . ------------ . ------------ . ------------ . --------
Plane 2
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
+-| |--| |--| |--| |--| |--| |--| |--| |-+
| | O | | O | | O | | O | | O | | O | | O | | O | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+
+-| |--| |--| |--| |--| |--| |--| |--| |-+
| | O | | O | | O | | O | | O | | O | | O | | O | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+
+-| |--| |--| |--| |--| |--| |--| |--| |-+
| | O | | O | | O | | O | | O | | O | | O | | O | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
^
|
| ---------------------
+----- ToF Node Across Depth
---------------------
Figure 11: Northern View of a Multi-Plane ToF Level, K_LEAF=6, N=2
At the extreme end of the spectrum spectrum, it is even possible to fully
partition the spine with N = K_LEAF N=K_LEAF and R=1, R=1 while maintaining
connectivity between each leaf node and each ToF node. In that case case,
the ToF node connects to a single Port port per PoD, so it appears as a
single port in the projected view represented in Figure 12. The
number of ports required on the Spine Node spine node is more than or equal to
P, i.e., the number of PoDs.
Plane 1
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ -+
+-| |--| |--| |--| |--| |--| |--| |--| |-+ |
| | O | | O | | O | | O | | O | | O | | O | | O | | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ |
----------- . ------------------- . ------------ . ------- |
Plane 2 |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ |
| | O | | O | | O | | O | | O | | O | | O | | O | | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ |
----------- . ------------ . ---- . ------------ . ------- |
Plane 3 |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ |
| | O | | O | | O | | O | | O | | O | | O | | O | | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ |
----------- . ------------ . ------------------- . --------+<-+
Plane 4 | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ | |
| | O | | O | | O | | O | | O | | O | | O | | O | | | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ | |
----------- . ------------ . ------------ . ---- . ------- | |
Plane 5 | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ | |
| | O | | O | | O | | O | | O | | O | | O | | O | | | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ | |
----------- . ------------ . ------------ . -------------- | |
Plane 6 | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ | |
| | O | | O | | O | | O | | O | | O | | O | | O | | | |
+-| |--| |--| |--| |--| |--| |--| |--| |-+ | |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ -+ |
^ |
| |
| ---------------- ------------- |
+----- ToF Node Class of PoDs ---+
---------------- -------------
Figure 12: Northern View of a Maximally Partitioned ToF Level, R=1
5.3. Fallen Leaf Problem
As mentioned earlier, RIFT exhibits an anisotropic behavior tailored
for fabrics with a North / South north-south orientation and a high level of
interleaving paths. A non-partitioned fabric makes a total loss of
connectivity between a ToF node at the north and a leaf node at the
south a very rare but yet possible occasion that is fully healed by
positive disaggregation as described in Section 6.5.1. In large
fabrics or fabrics built from switches with a low radix, the ToF may
often become partitioned in planes planes, which makes the occurrence of
having it more likely that a
given leaf being is only reachable from a subset of the ToF
nodes more likely to happen. nodes. This
makes some further considerations necessary.
A "Fallen Leaf" is a leaf that can be reached by only a subset of ToF
nodes due to missing connectivity. If R is the redundancy factor,
then it takes at least R breakages to reach a "Fallen Leaf"
situation.
In a maximally partitioned fabric, the redundancy factor is R=1, so
any breakage in the fabric will cause one or more fallen leaves in
the affected plane. R=2 guarantees that a single breakage will not
cause a fallen leaf. However, not all cases require disaggregation.
The following cases do not require particular action:
* If a southern link on a node goes down, then connectivity through
that node is lost for all nodes south of it. There is no need to
disaggregate since the connectivity to this node is lost for all
spine nodes in a the same fashion.
* If a ToF Node node goes down, then northern traffic towards it is
routed via alternate ToF nodes in the same plane and there is no
need to disaggregate routes.
In a general manner, the mechanism of non-transitive non-transitive, positive
disaggregation is sufficient when the disaggregating ToF nodes
collectively connect to all the ToP nodes in the broken plane. This
happens in the following case:
* If the breakage is the last northern link from a ToP node to a ToF
node going down, then the fallen leaf problem affects only that
ToF node, and the connectivity to all the nodes in the PoD is lost
from that ToF node. This can be observed by other ToF nodes
within the plane where the ToP node is located and positively
disaggregated within that plane.
On the other hand, there is a need to disaggregate the routes to
Fallen Leaves within the plane in a transitive fashion, that is, all
the way to the other leaves, in the following cases:
* If the breakage is the last northern link from a leaf node within
a plane (there is only one such link in a maximally partitioned
fabric) that goes down, then connectivity to all unicast prefixes
attached to the leaf node is lost within the plane where the link
is located. Southern Reflection by a leaf node, e.g., between ToP
nodes, if the PoD has only 2 levels, happens in between planes,
allowing the ToP nodes to detect the problem within the PoD where
it occurs and positively disaggregate. The breakage can be
observed by the ToF nodes in the same plane through the North north
flooding of TIEs from the ToP nodes. The nodes However, the ToF nodes however need to
be aware of all the affected prefixes for the negative, possibly transitive
transitive, disaggregation to be fully effective (i.e., a node
advertising in the control plane that it cannot reach a certain
more specific prefix than default default, whereas such disaggregation must in
the extreme condition propagate must be propagated further down southbound).
The problem can also be observed by the ToF nodes in the other
planes through the flooding of North TIEs from the affected leaf
nodes, together with non-node North TIEs TIEs, which indicate the
affected prefixes. To be effective in that case, the positive
disaggregation must reach down to the nodes that make the plane
selection, which are typically the ingress leaf nodes. The
information is not useful for routing in the intermediate levels.
* If the breakage is a ToP node in a maximally partitioned fabric
(in which case it is the only ToP node serving the plane in that
PoD that goes down), then the connectivity to all the nodes in the
PoD is lost within the plane where the ToP node is located.
Consequently, all leaves of the PoD fall in this plane. Since the
Southern Reflection between the ToF nodes happens only within a
plane, ToF nodes in other planes cannot discover fallen leaves in
a different plane. They also cannot determine beyond their local
plane whether a leaf node that was initially reachable has become
unreachable. As the breakage can be observed by the ToF nodes in
the plane where the breakage happened, the ToF nodes in the plane
need to be aware of all the affected prefixes for the negative
disaggregation to be fully effective. The problem can also be
observed by the ToF nodes in the other planes through the flooding
of North TIEs from the affected leaf nodes, nodes if there are only 3
levels and the failing ToP nodes are node
is directly connected to the its leaf nodes,
and then again it which can detect the link
going down. Then again, the knowledge of the failure at the ToF
level can only be effective useful if it is propagated transitively to all
the leaf, and leaves; it is useless above that level. level since the decision of
placing a packet in a plane happens at the leaf that injects the
packet in the fabric.
These abstractions are rolled back into a simplified example that
shows that in Figure 3 the loss of the link between spine node 3 and
leaf node 3 will make leaf node 3 a fallen leaf for ToF nodes in
plane C. Worse, if the cabling was never present in the first place,
plane C will not even be able to know that such a fallen leaf exists. Hence
Hence, partitioning without further treatment results in two grave
problems:
*
1. Leaf node 1 trying to route to leaf node 3 must not choose spine
node 3 in plane C as its next hop since it will inevitably drop
the packet when forwarding using default routes or do excessive
bow-tying. This information must be in its routing table.
*
2. A path computation trying to deal with the problem by
distributing host routes may only form paths through leaves. The
flooding of information about leaf node 3 would have to go up to
ToF nodes in planes A, B, and D and then "loopback" over other
leaves to ToF C C, leading in extreme cases to traffic for leaf
node 3 when presented to plane C taking an "inverted fabric" path
where leaves start to serve as ToFs, at least for the duration of
a protocol's convergence.
5.4. Discovering Fallen Leaves
When aggregation is used, RIFT deals with fallen leaves by ensuring
that all the ToF nodes share the same north topology database. This
happens naturally in single plane single-plane design by the means of northbound
flooding and south reflection but needs additional considerations in
multi-plane fabrics. To enable routing to fallen leaves in multi-
plane designs, RIFT requires additional interconnection across planes
between the ToF nodes, e.g., using rings as illustrated in Figure 13.
Other solutions are possible possible, but they either need more cabling or
end up having much longer flooding paths and/or single points of
failure.
In detail, by reserving at least two ports on each ToF node node, it is
possible to connect them together by interplane bi-directional bidirectional rings
as illustrated in Figure 13. The rings will be used to exchange full
north topology information between planes. All ToFs having the same
north topology allows allows, by the means of transitive, negative
disaggregation described in Section 6.5.2 6.5.2, to efficiently fix any
possible fallen leaf scenario. Somewhat as a side effect, the
exchange of information fulfills the requirement for a full view of
the fabric topology at the ToF level, level without the need to collate it
from multiple points.
____________________________________________________________________________
| [Plane A] . [Plane B] . [Plane C] . [Plane D] |
|..........................................................................|
| +-------------------------------------------------------------+ |
| | +---+ . +---+ . +---+ . +---+ | |
| +-+ n +-------------+ n +-------------+ n +-------------+ n +-+ |
| +--++ . +-+++ . +-+++ . +--++ |
| || . || . || . || |
| +---------||---------------||----------------||---------------+ || |
| | +---+ || . +---+ || . +---+ || . +---+ | || |
| +-+ 1 +---||--------+ 1 +--||---------+ 1 +--||---------+ 1 +-+ || |
| +--++ || . +-+++ || . +-+++ || . +-+++ || |
| || || . || || . || || . || || |
| || || . || || . || || . || || |
Figure 13: Using rings Rings to bring all planes Bring All Planes and Bind Them at the ToF bind them
5.5. Addressing the Fallen Leaves Problem
One consequence of the "Fallen Leaf" problem is that some prefixes
attached to the fallen leaf become unreachable from some of the ToF
nodes. RIFT defines two methods to address this issue issue, denoted as
positive disaggregation and negative disaggregation. Both methods
flood corresponding types of South TIEs to advertise the impacted
prefix(es).
When used for the operation of disaggregation, a positive South TIE,
as usual, indicates reachability to a prefix of given length and all
addresses subsumed by it. In contrast, a negative route
advertisement indicates that the origin cannot route to the
advertised prefix.
The positive disaggregation is originated by a router that can still
reach the advertised prefix, and the operation is not transitive. In
other words, the receiver does *not* generate its own TIEs or flood
them south as a consequence of receiving positive disaggregation
advertisements from a higher level higher-level node. The effect of a positive
disaggregation is that the traffic to the impacted prefix will follow
the longest match and will be limited to the northbound routers that
advertised the more specific route.
In contrast, the negative disaggregation can be transitive, transitive and is
propagated south when all the possible routes have been advertised as
negative exceptions. A negative route advertisement is only
actionable when the negative prefix is aggregated by a positive route
advertisement for a shorter prefix. In such case, the negative
advertisement "punches out a hole" in the positive route in the
routing table, making the positive prefix reachable through the
originator with the special consideration of the negative prefix
removing certain next hop next-hop neighbors. The specific procedures will be are
explained in detail in Section 6.5.2.3.
When the ToF switches are not partitioned into multiple planes, the
resulting southbound flooding of the positive disaggregation by the
ToF nodes that can still reach the impacted prefix is in general generally
enough to cover all the switches at the next level south, typically
the ToP nodes. If all those switches are aware of the
disaggregation, they collectively create a ceiling that intercepts
all the traffic north and forwards it to the ToF nodes that
advertised the more specific route. In that case, the positive
disaggregation alone is sufficient to solve the fallen leaf problem.
On the other hand, when the fabric is partitioned in planes, the
positive disaggregation from ToF nodes in different planes do not
reach the ToP switches in the affected plane and cannot solve the
fallen leaves problem. In other words, a breakage in a plane can
only be solved in that plane. Also, the selection of the plane for a
packet typically occurs at the leaf level and the disaggregation must
be transitive and reach all the leaves. In that case, the negative
disaggregation is necessary. The details on the RIFT approach to
deal with fallen leaves in an optimal way are specified in
Section 6.5.2.
6. Specification
This section specifies the protocol in a normative fashion by either
prescriptive procedures or behavior defined by Finite State Machines
(FSM).
(FSMs).
The FSMs, as usual, are presented as states a neighbor can assume,
events that can occur, and the corresponding actions performed when
transitioning between states on event processing.
Actions are performed before the end state is assumed.
The FSMs can queue events against itself themselves to chain actions or
against other FSMs in the specification. Events are always processed
in the sequence they have been queued.
Consequently, "On Entry" actions for an FSM state are performed every
time and right before the corresponding state is entered, i.e., after
any transitions from previous state.
"On Exit" actions are performed every time and immediately when a
state is exited, i.e., before any transitions towards the target
state are performed.
Any attempt to transition from a state towards another on reception
of an event where no action is specified MUST be considered an
unrecoverable error error, and the protocol MUST reset all adjacencies and
discard all the state states (i.e., force the FSM back to _OneWay_ and
flush all of the queues holding flooding information).
The data structures and FSMs described in this document are
conceptual and do not have to be implemented precisely as described
here, i.e., an implementation is considered conforming as long as it
supports the described functionality and exhibits externally
observable behavior equivalent to the behavior of the standardized
FSMs.
The FSMs can use "timers" for different situations. Those timers are
started through actions actions, and their expiration leads to queuing of
corresponding events to be processed.
The term "holdtime" is used often as short-hand shorthand for "holddown timer"
and signifies either the length of the holding down period or the
timer used to expire after such period. Such timers are used to
"hold down" the state within an FSM that is cleaned if the machine
triggers a _HoldtimeExpired_ event.
6.1. Transport
All normative RIFT packet structures and their contents are defined
in the Thrift [thrift] models in Section 7. The packet structure
itself is defined in _ProtocolPacket_ _ProtocolPacket_, which contains the packet
header in _PacketHeader_ and the packet contents in _PacketContent_.
_PacketContent_ is a union of the LIE, TIE, TIDE, and TIRE packets packets,
which are subsequently defined in _LIEPacket_, _TIEPacket_,
_TIDEPacket_, and _TIREPacket_ _TIREPacket_, respectively.
Further, in terms of bits on the wire, it is the _ProtocolPacket_
that is serialized and carried in an envelope defined in
Section 6.9.3 within a UDP frame that provides security and allows
validation/modification of several important fields without Thrift
de-serialization
deserialization for performance and security reasons. Security
model
models and procedures are further explained in Section 9.
6.2. Link (Neighbor) Discovery (LIE Exchange)
RIFT LIE exchange auto-discovers neighbors, negotiates RIFT ZTP
parameters
parameters, and discovers miscablings. The formation progresses
under normal conditions from _OneWay_ to _TwoWay_ and then _ThreeWay_ state
state, at which point it is ready to exchange TIEs per as described in
Section 6.3. The adjacency exchanges RIFT ZTP information
(Section 6.7) in any of the states, i.e. i.e., it is not necessary to
reach _ThreeWay_ for zero-touch
provisioning ZTP to operate.
RIFT supports any combination of IPv4 and IPv6 addressing, including
link-local scope, on the fabric to form adjacencies with the
additional capability for forwarding paths that are capable of
forwarding IPv4 packets in the presence of IPv6 addressing only.
IPv4 LIE exchange happens by default over well-known administratively
locally scoped and configured or otherwise well-known IPv4 multicast
address [RFC2365]. For IPv6 [RFC8200] [RFC8200], exchange is performed over
the link-local multicast scope [RFC4291] address address, which is configured
or otherwise well-known. In both cases cases, a destination UDP port
defined in the schema Section 7.2 (Section 7.2) is used unless configured
otherwise. LIEs MUST be sent with an IPv4 Time to Live (TTL) or an
IPv6 Hop Limit (HL) of either 1 or 255 to prevent RIFT information
reaching beyond a single L3 next-hop Layer 3 (L3) next hop in the topology.
Observe that that, for the allocated link-local scope IP multicast address
address, the TTL value of 1 is a more logical choice since the TTL
value of 255 may may, in some environment environments, lead to an early drop due to
the suspicious TTL value for a packet addressed to such a
destination. LIEs SHOULD be sent with network control precedence
unless an implementation is prevented from doing so [RFC2474].
Any LIE packet received on an address that is neither the well-known
nor configured multicast or a broadcast address MUST be discarded.
The originating port of the LIE has no further significance significance, other
than identifying the origination point. LIEs are exchanged over all
links running RIFT.
An implementation may listen and send LIEs on IPv4 and/or IPv6
multicast addresses. A node MUST NOT originate LIEs on an address
family if it does not process received LIEs on that family. LIEs on
the same link are considered part of the same LIE FSM independent of
the address family they arrive on. The LIE source address may not
identify the peer uniquely in unnumbered or link-local address cases
so the response transmission MUST occur over the same interface the
LIEs have been received on. A node may use any of the adjacency's
source addresses it saw in LIEs on the specific interface during
adjacency formation to send TIEs (Section 6.3.3). That implies that
an implementation MUST be ready to accept TIEs on all addresses it
used as source sources of LIE frames.
A simplified version MAY be implemented on platforms with limited
multicast support (e.g. IoT (e.g., Internet of Things (IoT) devices) by sending
and receiving LIE frames on IPv4 subnet broadcast addresses or IPv6 all routers
all-routers multicast address. addresses. However, this technique is less
optimal and presents a wider attack surface from a security
perspective and should hence be used only as a last resort.
A _ThreeWay_ adjacency (as defined in the glossary) over any address
family implies support for IPv4 forwarding if the
_ipv4_forwarding_capable_ flag in _LinkCapabilities_ is set to true.
In the absence of IPv4 LIEs with _ipv4_forwarding_capable_ set to
true, a node MUST forward IPv4 packets using gateways discovered on
IPv6-only links advertising this capability. The mechanism to
discover the corresponding IPv6 gateway is out of scope for this
specification and may be implementation specific. implementation-specific. It is expected
that the whole fabric supports the same type of forwarding of address
families on all the links, links; any other combination is outside the scope
of this specification. If IPv4 forwarding is supported on an
interface, _ipv4_forwarding_capable_ MUST be set to true for all LIEs
advertised from that interface. If IPv4 and IPv6 LIEs indicate
contradicting information, protocol behavior is unspecified. A node
sending IPv4 LIEs MUST set the _ipv4_forwarding_capable_ flag to true
on all LIEs advertised from that interface.
Operation of a fabric where only some of the links are supporting
forwarding on an address family or have an address in a family and
others do not is outside the scope of this specification.
Any attempt to construct IPv6 forwarding over IPv4 only IPv4-only adjacencies
is outside the scope of this specification.
Table 1 outlines protocol behavior pertaining to LIE exchange over
different address family combinations. Table 2 outlines the way in
which neighbors forward traffic as it pertains to the
_ipv4_forwarding_capable_ flag setting across the same address family
combinations. The table is symmetric, i.e. i.e., the local and remote
columns can be exchanged to construct the remaining combinations.
The specific forwarding implementation to support the described
behavior is out of scope for this document.
+==========+==========+==========================================+
| Local | Remote | LIE Exchange Behavior |
| Neighbor | Neighbor | |
| AF | AF | |
+==========+==========+==========================================+
| IPv4 | IPv4 | LIEs and TIEs are exchanged over IPv4 |
| | | only. The local neighbor receives TIEs |
| | | from remote neighbors on any of the LIE |
| | | source addresses. |
+----------+----------+------------------------------------------+
| IPv6 | IPv6 | LIEs and TIEs are exchanged over IPv6 |
| | | only. The local neighbor receives TIEs |
| | | from remote neighbors on any of the LIE |
| | | source addresses. |
+----------+----------+------------------------------------------+
| IPv4, | IPv6 | The local neighbor sends LIEs for both |
| IPv6 | | IPv4 and IPv6 IPv6, while the remote neighbor |
| | | only sends LIEs for IPv6. The resulting |
| | | adjacency will exchange TIEs over IPv6 |
| | | on any of the IPv6 LIE source addresses. |
+----------+----------+------------------------------------------+
| IPv4, | IPv4, | LIEs and TIEs are exchanged over IPv6 |
| IPv6 | IPv6 | and IPv4. TIEs are received on any of |
| | | the IPv4 or IPv6 LIE source addresses. |
| | | The local neighbor receives TIEs from |
| | | the remote neighbors on any of the IPv4 |
| | | or IPv6 LIE source addresses. |
+----------+----------+------------------------------------------+
| IPv4, | IPv4 | The local neighbor sends LIEs for both |
| IPv6 | | IPv4 and IPv6 IPv6, while the remote neighbor |
| | | only sends LIEs for IPv4. The resulting |
| | | adjacency will exchange TIEs over IPv4 |
| | | on any of the IPv4 LIE source addresses. |
+----------+----------+------------------------------------------+
Table 1: Control Plane Behavior for Neighbor AF Combinations
+==========+==========+==========================================+
| Local | Remote | Forwarding Behavior |
| Neighbor | Neighbor | |
| AF | AF | |
+==========+==========+==========================================+
| IPv4 | IPv4 | Only IPv4 traffic can be forwarded. |
+----------+----------+------------------------------------------+
| IPv6 | IPv6 | If either neighbor sets |
| | | _ipv4_forwarding_capable_ to false, only |
| | | IPv6 traffic can be forwarded. If both |
| | | neighbors set _ipv4_forwarding_capable_ |
| | | to true, IPv4 traffic is also forwarded |
| | | via IPv6 gateways. |
+----------+----------+------------------------------------------+
| IPv4, | IPv6 | If the remote neighbor sets |
| IPv6 | | _ipv4_forwarding_capable_ to false, only |
| | | IPv6 traffic can be forwarded. If both |
| | | neighbors set _ipv4_forwarding_capable_ |
| | | to true, IPv4 traffic is also forwarded |
| | | via IPv6 gateways. |
+----------+----------+------------------------------------------+
| IPv4, | IPv4, | IPv4 and IPv6 traffic can be forwarded. |
| IPv6 | IPv6 | If IPv4 and IPv6 LIEs advertise |
| | | conflicting _ipv4_forwarding_capable_ |
| | | flags, the behavior is unspecified. |
+----------+----------+------------------------------------------+
| IPv4, | IPv4 | IPv4 traffic can be forwarded. |
| IPv6 | | |
+----------+----------+------------------------------------------+
Table 2: Forwarding Behavior for Neighbor AF Combinations
The protocol does *not* support selective disabling of address
families after adjacency formation, disabling IPv4 forwarding
capability
capability, or any local address changes in _ThreeWay_ state, i.e. i.e.,
if a link has entered ThreeWay IPv4 and/or IPv6 with a neighbor on an
adjacency and it wants to stop supporting one of the families or families, change
any of its local addresses addresses, or stop IPv4 forwarding, it MUST tear
down and rebuild the adjacency. It MUST also remove any state it
stored about the remote side of the adjacency such as associated LIE
source addresses.
Unless RIFT ZTP is used as described in Section 6.7 is used, 6.7, each node is
provisioned with the level at which it is operating and advertises it
in the _level_ of the _PacketHeader_ schema element. It MAY be also be
provisioned with its PoD. If the level is not provisioned, it is not
present in the optional _PacketHeader_ schema element and established
by ZTP procedures procedures, if feasible. If PoD is not provisioned, it is
governed by the _LIEPacket_ schema element assuming the
_common.default_pod_ value. This means that switches except ToF do
not need to be configured at all. Necessary information to configure
all values is exchanged in the _LIEPacket_ and _PacketHeader_ or
derived by the node automatically.
Further definitions of leaf flags are found in Section 6.7 given they
have implications in terms of level and adjacency forming here. Leaf
flags are carried in _HierarchyIndications_.
A node MUST form a _ThreeWay_ adjacency if if, at a minimum minimum, the
following first order logic conditions are satisfied on a LIE packet packet,
as specified by the _LIEPacket_ schema element and received on a link
(such a LIE is considered a "minimally valid" LIE). Observe that that,
depending on the FSM involved and its state further further, conditions may
be
checked checked, and even a minimally valid LIE can be considered
ultimately invalid if any of the additional conditions fail. fail:
1. the neighboring node is running the same major schema version as
indicated in the _major_version_ element in _PacketHeader_ *and* _PacketHeader_;
2. the neighboring node uses a valid System ID (i.e. (i.e., a value
different from _IllegalSystemID_) in the _sender_ element in _PacketHeader_
*and*
_PacketHeader_;
3. the neighboring node uses a different System ID than the node
itself *and*
itself;
4. (the the advertised MTU values in the _LiePacket_ element match on
both sides sides, while a missing MTU in the _LiePacket_ element is
interpreted as _default_mtu_size_) *and* _default_mtu_size_;
5. both nodes advertise defined level values in the _level_ element
in
_PacketHeader_ _PacketHeader_, *and*
6. [
i) either:
a. the node is at the _leaf_level_ value and has no _ThreeWay_
adjacencies already to nodes at Highest Adjacency _ThreeWay_
(HAT
(HAT), as defined later in Section 6.7.1) 6.7.1, with the level
different than the adjacent node *or*
ii) node;
b. the node is not at the _leaf_level_ value and the neighboring
node is at the _leaf_level_ value *or*
iii) value;
c. both nodes are at the _leaf_level_ values *and* both indicate
support for that described in Section 6.8.9 6.8.9; *or*
iv)
d. neither node is at the _leaf_level_ value and the neighboring
node is is, at most most, one level difference away
]. away.
LIEs arriving with IPv4 Time to Live (TTL) or an IPv6 Hop Limit (HL)
different than 1 or 255 MUST be ignored.
6.2.1. LIE Finite State Machine
This section specifies the precise, normative LIE FSM FSM, which is given
as well also
shown in Figure 14. Additionally, some sets of actions often repeat
and are hence summarized into well-known procedures.
Events generated are fairly fine grained, especially when indicating
problems in adjacency forming adjacency-forming conditions to simplify tracking of
problems in deployment.
Initial
The initial state is _OneWay_.
The machine sends LIEs proactively on several transitions to
accelerate adjacency bring-up without waiting for the corresponding
timer tic.
Enter
|
V
+-----------+
| OneWay |<----+
| | | TimerTick
| | | LevelChanged
| | | HALChanged
| | | HATChanged
| | | HALSChanged
| | | LieRcvd
| | | NeighborDroppedReflection
| | | NeighborChangedLevel
| | | NeighborChangedAddress
| | | UnacceptableHeader
| | | MTUMismatch
| | | NeighborChangedMinorFields
| | | HoldtimeExpired
| | | FloodLeadersChanged
| | | SendLie
| | | UpdateZTPOffer
| |-----+
| |
| |<--------------------- (ThreeWay)
| |--------------------->
| | ValidReflection
| |
| |---------------------> (Multiple
| | MultipleNeighbors Neighbors
+-----------+ Wait)
^ |
| |
| | NewNeighbor
| V
(TwoWay)
(OneWay)
| ^
| | NeighborChangedLevel
| | NeighborChangedAddress
| | UnacceptableHeader
| | MTUMismatch
| | HoldtimeExpired
| |
V |
+-----------+
| TwoWay |<----+
| | | TimerTick
| | | LevelChanged
| | | HALChanged
| | | HATChanged
| | | HALSChanged
| | | LieRcvd
| | | FloodLeadersChanged
| | | SendLie
| | | UpdateZTPOffer
| |-----+
| |
| |<----------------------
| |----------------------> (Multiple
| | NewNeighbor Neighbors
| | Wait)
| | MultipleNeighbors
+-----------+
^ |
| | ValidReflection
| V
(ThreeWay)
(TwoWay) (OneWay)
^ | ^
| | | LevelChanged
| | | NeighborChangedLevel
| | | NeighborChangedAddress
| | | UnacceptableHeader
| | | MTUMismatch
| | | HoldtimeExpired
NeighborDropped- | | |
Reflection | | |
| V |
+-----------+ |
| ThreeWay |-----+
| |
| |<----+
| | | TimerTick
| | | HALChanged
| | | HATChanged
| | | HALSChanged
| | | LieRcvd
| | | ValidReflection
| | | FloodLeadersChanged
| | | SendLie
| | | UpdateZTPOffer
| |-----+
| |----------------------> (Multiple
| | MultipleNeighbors Neighbors
+-----------+ Wait)
(TwoWay) (ThreeWay)
| |
V V
+------------+
| Multiple |<----+
| Neighbors | | TimerTick
| Wait | | HALChanged
| | | HATChanged
| | | HALSChanged
| | | LieRcvd
| | | ValidReflection
| | | NeighborDroppedReflection
| | | NeighborChangedBFDCapability
| | | NeighborChangedAddress
| | | UnacceptableHeader
| | | MTUMismatch
| | | HoldtimeExpired
| | | MultipleNeighbors
| | | FloodLeadersChanged
| | | SendLie
| | | UpdateZTPOffer
| |-----+
| |
| |<---------------------------
| |---------------------------> (OneWay)
| | LevelChanged
+------------+ MultipleNeighborsDone
Figure 14: LIE FSM
The following words are used for well-known procedures:
* PUSH Event: queues an event to be executed by the FSM upon exit of
this action
* CLEANUP: The FSM *conceptually* holds a `current neighbor` "current neighbor"
variable that contains information received in the remote node's
LIE that is processed against LIE validation rules. In the event
that the LIE is considered to be invalid, the existing state held
by `current neighbor` a "current neighbor" MUST be deleted.
* SEND_LIE: create and send a new LIE packet
1. reflecting the _neighbor_ element as described in
ValidReflection and
ValidReflection,
2. setting the necessary _not_a_ztp_offer_ variable if the level
was derived from the last known last-known neighbor on this interface interface,
and
3. setting the _you_are_flood_repeater_ variable to the computed
value
value.
* PROCESS_LIE:
1. if LIE has a major version not equal to this node's major
version *or* System ID equal to (this this node's System ID or
_IllegalSystemID_)
_IllegalSystemID_, then CLEANUP CLEANUP, else
2. if both sides advertise Layer 2 MTU values and the MTU in the
received LIE does not match the MTU advertised by the local
system *or* at least one of the nodes does not advertise an
MTU value and the advertising node's LIE does not match the
_default_mtu_size_ of the system not advertising an MTU MTU, then
CLEANUP, PUSH UpdateZTPOffer, and PUSH MTUMismatch MTUMismatch, else
3. if the LIE has an undefined level *or* this node's level is
undefined *or* this node is a leaf and the remote level is
lower than HAT *or* (the the LIE's level is not leaf *and* its
difference is more than one from this node's level) level, then
CLEANUP, PUSH UpdateZTPOffer, and PUSH UnacceptableHeader UnacceptableHeader,
else
4. PUSH UpdateZTPOffer, construct a temporary new neighbor
structure with values from LIE, if no current neighbor exists exists,
then set current neighbor to new neighbor, PUSH NewNeighbor
event, CHECK_THREE_WAY CHECK_THREE_WAY, else
1.
a. if the current neighbor System ID differs from LIE's
System ID ID, then PUSH MultipleNeighbors MultipleNeighbors, else
2.
b. if the current neighbor stored level differs from LIE's level
level, then PUSH NeighborChangedLevel NeighborChangedLevel, else
3.
c. if the current neighbor stored IPv4/v6 address differs
from LIE's address address, then PUSH NeighborChangedAddress NeighborChangedAddress, else
4.
d. if any of the neighbor's flood address port, name, or
local LinkID changed changed, then PUSH NeighborChangedMinorFields
5.
e. CHECK_THREE_WAY
* CHECK_THREE_WAY: if the current state is _OneWay_ _OneWay_, do nothing nothing,
else
1. if LIE packet does not contain a neighbor then and if the current
state is _ThreeWay_ _ThreeWay_, then PUSH NeighborDroppedReflection NeighborDroppedReflection, else
2. if the packet reflects this system's System ID and local port and the
state is _ThreeWay_ _ThreeWay_, then PUSH event the ValidReflection event, else
PUSH event the MultipleNeighbors event.
States:
* OneWay: The initial state the FSM is starting from. In this state
state, the router did not receive any valid LIEs from a neighbor.
* TwoWay: that This state is entered when a node has received a minimally
valid LIE from a neighbor but not a ThreeWay valid LIE.
* ThreeWay: this This state signifies that _ThreeWay_ valid LIEs from a
neighbor have been received. On achieving this state state, the link
can be advertised in the _neighbors_ element in _NodeTIEElement_.
* MultipleNeighborsWait: occurs Occurs normally when more than two nodes
become aware of each other on the same link or a remote node is
quickly reconfigured or rebooted without regressing to _OneWay_
first. Each occurrence of the event SHOULD generate a
notification to help operational deployments.
Events:
* TimerTick: one-second One-second timer tick, i.e., the event is provided to
the FSM once a second by an implementation-specific mechanism that
is outside the scope of this specification. This event is quietly
ignored if the relevant transition does not exist.
* LevelChanged: node's Node's level has been changed by ZTP or
configuration. This is provided by the ZTP FSM.
* HALChanged: best Best HAL computed by ZTP has changed. This is
provided by the ZTP FSM.
* HATChanged: HAT computed by ZTP has changed. This is provided by
the ZTP FSM.
* HALSChanged: set Set of HAL offering systems computed by ZTP has
changed. This is provided by the ZTP FSM.
* LieRcvd: received Received LIE on the interface.
* NewNeighbor: new New neighbor is present in the received LIE.
* ValidReflection: received Received valid reflection of this node from the
neighbor, i.e. i.e., all elements in the _neighbor_ element in
_LiePacket_ have values corresponding to this link.
* NeighborDroppedReflection: lost Lost previously held reflection from
the neighbor, i.e. i.e., the _neighbor_ element in _LiePacket_ does not
correspond to this node or is not present.
* NeighborChangedLevel: neighbor Neighbor changed the advertised level from
the previously held one.
* NeighborChangedAddress: neighbor Neighbor changed the IP address, i.e. i.e., the
LIE has been received from an address different from previous
LIEs. Those changes will influence the sockets used to listen to
TIEs, TIREs, and TIDEs.
* UnacceptableHeader: Unacceptable header received.
* MTUMismatch: MTU mismatched.
* NeighborChangedMinorFields: minor Minor fields changed in the neighbor's
LIE.
* HoldtimeExpired: adjacency Adjacency holddown timer expired.
* MultipleNeighbors: more More than one neighbor is present on interface the
interface.
* MultipleNeighborsDone: multiple neighbors timer Multiple neighbors' timers expired.
* FloodLeadersChanged: node's Node's election algorithm determined new set
of flood leaders.
* SendLie: send Send a LIE out.
* UpdateZTPOffer: update Update this node's ZTP offer. This is sent to the
ZTP FSM.
Actions:
* on HATChanged in _OneWay_ finishes in OneWay: store HAT
* on FloodLeadersChanged in _OneWay_ finishes in OneWay: update
_you_are_flood_repeater_ LIE elements based on the flood leader
election results
* on UnacceptableHeader in _OneWay_ finishes in OneWay: no action
* on NeighborChangedMinorFields in _OneWay_ finishes in OneWay: no
action
* on SendLie in _OneWay_ finishes in OneWay: SEND_LIE
* on HALSChanged in _OneWay_ finishes in OneWay: store the HALS
* on MultipleNeighbors in _OneWay_ finishes in
MultipleNeighborsWait: start multiple neighbors timer neighbors' timers with the
interval _multiple_neighbors_lie_holdtime_multipler_ *
_default_lie_holdtime_
* on NeighborChangedLevel in _OneWay_ finishes in OneWay: no action
* on LieRcvd in _OneWay_ finishes in OneWay: PROCESS_LIE
* on MTUMismatch in _OneWay_ finishes in OneWay: no action
* on ValidReflection in _OneWay_ finishes in ThreeWay: no action
* on LevelChanged in _OneWay_ finishes in OneWay: update the level
with the event value, PUSH the SendLie event
* on HALChanged in _OneWay_ finishes in OneWay: store the new HAL
* on HoldtimeExpired in _OneWay_ finishes in OneWay: no action
* on NeighborChangedAddress in _OneWay_ finishes in OneWay: no
action
* on NewNeighbor in _OneWay_ finishes in TwoWay: PUSH the SendLie
event
* on UpdateZTPOffer in _OneWay_ finishes in OneWay: send the offer
to the ZTP FSM
* on NeighborDroppedReflection in _OneWay_ finishes in OneWay: no
action
* on TimerTick in _OneWay_ finishes in OneWay: PUSH SendLie event
* on FloodLeadersChanged in _TwoWay_ finishes in TwoWay: update
_you_are_flood_repeater_ LIE elements based on the flood leader
election results
* on UpdateZTPOffer in _TwoWay_ finishes in TwoWay: send the offer
to the ZTP FSM
* on NewNeighbor in _TwoWay_ finishes in MultipleNeighborsWait: PUSH
the SendLie event
* on ValidReflection in _TwoWay_ finishes in ThreeWay: no action
* on LieRcvd in _TwoWay_ finishes in TwoWay: PROCESS_LIE
* on UnacceptableHeader in _TwoWay_ finishes in OneWay: no action
* on HALChanged in _TwoWay_ finishes in TwoWay: store the new HAL
* on HoldtimeExpired in _TwoWay_ finishes in OneWay: no action
* on LevelChanged in _TwoWay_ finishes in TwoWay: update the level
with the event value
* on TimerTick in _TwoWay_ finishes in TwoWay: PUSH SendLie event,
if last valid LIE was received more than _holdtime_ ago as
advertised by neighbor the neighbor, then PUSH the HoldtimeExpired event
* on HATChanged in _TwoWay_ finishes in TwoWay: store HAT
* on NeighborChangedLevel in _TwoWay_ finishes in OneWay: no action
* on HALSChanged in _TwoWay_ finishes in TwoWay: store the HALS
* on MTUMismatch in _TwoWay_ finishes in OneWay: no action
* on NeighborChangedAddress in _TwoWay_ finishes in OneWay: no
action
* on SendLie in _TwoWay_ finishes in TwoWay: SEND_LIE
* on MultipleNeighbors in _TwoWay_ finishes in
MultipleNeighborsWait: start multiple neighbors timer neighbors' timers with the
interval _multiple_neighbors_lie_holdtime_multipler_ *
_default_lie_holdtime_
* on TimerTick in _ThreeWay_ finishes in ThreeWay: PUSH the SendLie
event, if the last valid LIE was received more than _holdtime_ ago
as advertised by neighbor the neighbor, then PUSH the HoldtimeExpired event
* on LevelChanged in _ThreeWay_ finishes in OneWay: update the level
with the event value
* on HATChanged in _ThreeWay_ finishes in ThreeWay: store HAT
* on MTUMismatch in _ThreeWay_ finishes in OneWay: no action
* on UnacceptableHeader in _ThreeWay_ finishes in OneWay: no action
* on MultipleNeighbors in _ThreeWay_ finishes in
MultipleNeighborsWait: start multiple neighbors timer neighbors' timers with the
interval _multiple_neighbors_lie_holdtime_multipler_ *
_default_lie_holdtime_
* on NeighborChangedLevel in _ThreeWay_ finishes in OneWay: no
action
* on HALSChanged in _ThreeWay_ finishes in ThreeWay: store the HALS
* on LieRcvd in _ThreeWay_ finishes in ThreeWay: PROCESS_LIE
* on FloodLeadersChanged in _ThreeWay_ finishes in ThreeWay: update
_you_are_flood_repeater_ LIE elements based on the flood leader
election results, PUSH the SendLie event
* on NeighborDroppedReflection in _ThreeWay_ finishes in TwoWay: no
action
* on HoldtimeExpired in _ThreeWay_ finishes in OneWay: no action
* on ValidReflection in _ThreeWay_ finishes in ThreeWay: no action
* on UpdateZTPOffer in _ThreeWay_ finishes in ThreeWay: send the
offer to the ZTP FSM
* on NeighborChangedAddress in _ThreeWay_ finishes in OneWay: no
action
* on HALChanged in _ThreeWay_ finishes in ThreeWay: store the new
HAL
* on SendLie in _ThreeWay_ finishes in ThreeWay: SEND_LIE
* on MultipleNeighbors in MultipleNeighborsWait finishes in
MultipleNeighborsWait: start multiple neighbors timer neighbors' timers with the
interval _multiple_neighbors_lie_holdtime_multipler_ *
_default_lie_holdtime_
* on FloodLeadersChanged in MultipleNeighborsWait finishes in
MultipleNeighborsWait: update _you_are_flood_repeater_ LIE
elements based on the flood leader election results
* on TimerTick in MultipleNeighborsWait finishes in
MultipleNeighborsWait: check MultipleNeighbors timer, if the timer
expired
expired, PUSH MultipleNeighborsDone
* on ValidReflection in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on UpdateZTPOffer in MultipleNeighborsWait finishes in
MultipleNeighborsWait: send the offer to the ZTP FSM
* on NeighborDroppedReflection in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on LieRcvd in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on UnacceptableHeader in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on NeighborChangedAddress in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on LevelChanged in MultipleNeighborsWait finishes in OneWay:
update the level with the event value
* on HATChanged in MultipleNeighborsWait finishes in
MultipleNeighborsWait: store HAT
* on MTUMismatch in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on HALSChanged in MultipleNeighborsWait finishes in
MultipleNeighborsWait: store the HALS
* on HALChanged in MultipleNeighborsWait finishes in
MultipleNeighborsWait: store the new HAL
* on HoldtimeExpired in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on SendLie in MultipleNeighborsWait finishes in
MultipleNeighborsWait: no action
* on MultipleNeighborsDone in MultipleNeighborsWait finishes in
OneWay: no action
* on Entry into OneWay: CLEANUP
6.3. Topology Exchange (TIE Exchange)
6.3.1. Topology Information Elements
Topology and reachability information in RIFT is conveyed by TIEs.
The TIE exchange mechanism uses the port indicated by each node in
the LIE exchange as _flood_port_ in _LIEPacket_ and the interface on
which the adjacency has been formed as the destination. TIEs MUST be
sent with an IPv4 Time to Live (TTL) or an IPv6 Hop Limit (HL) of
either 1 or 255 and also MUST be ignored if received with values
different than 1 or 255. This helps to protect RIFT information from
being accepted beyond a single L3 next-hop next hop in the topology. TIEs
SHOULD be sent with network control precedence unless an
implementation is prevented from doing so [RFC2474].
TIEs contain sequence numbers, lifetimes, and a type. Each type has
ample identifying number space space, and information is spread across
multiple TIEs with the same TIEElement type (this is true for all TIE
types).
More information about the TIE structure can be found in the schema
in Section 7 7, starting with _TIEPacket_ root.
6.3.2. Southbound and Northbound TIE Representation
A central concept of RIFT is that each node represents itself
differently
differently, depending on the direction in which it is advertising
information. More precisely, a spine node represents two different
databases over its adjacencies adjacencies, depending on whether it advertises
TIEs to the north or to the south/east-west. Those differing TIE
databases are called either south- southbound or northbound (South TIEs and
North TIEs) TIEs), depending on the direction of distribution.
The North TIEs hold all of the node's adjacencies and local prefixes prefixes,
while the South TIEs hold only all of the node's adjacencies, the default
prefix with necessary disaggregated prefixes prefixes, and local prefixes.
Section 6.5 explains further details.
All TIE types are mostly symmetrical in both directions. The
(Section 7.3) Section 7.3
defines the TIE types (i.e., the TIETypeType element) and their
directionality (i.e., _direction_ within the _TIEID_ element).
As an example illustrating a database holding both representations,
the topology in Figure 2 with the optional link between spine 111 and
spine 112 (so that the flooding on an East-West link can be shown) is
shown below. Unnumbered interfaces are implicitly assumed and and, for
simplicity, the key value elements elements, which may be included in their
South TIEs or North TIEs TIEs, are not shown. First, in Figure 15 are shows the
TIEs generated by some nodes.
ToF 21 South TIEs:
Node South TIE:
NodeTIEElement(level=2,
neighbors(
(Spine 111, level 1, cost 1, links(...)),
(Spine 112, level 1, cost 1, links(...)),
(Spine 121, level 1, cost 1, links(...)),
(Spine 122, level 1, cost 1, links(...))
)
)
Prefix South TIE:
PrefixTIEElement(prefixes(0/0, metric 1), (::/0, metric 1))
Spine 111 South TIEs:
Node South TIE:
NodeTIEElement(level=1,
neighbors(
(ToF 21, level 2, cost 1, links(...)),
(ToF 22, level 2, cost 1, links(...)),
(Spine 112, level 1, cost 1, links(...)),
(Leaf111, level 0, cost 1, links(...)),
(Leaf112, level 0, cost 1, links(...))
)
)
Prefix South TIE:
PrefixTIEElement(prefixes(0/0, metric 1), (::/0, metric 1))
Spine 111 North TIEs:
Node North TIE:
NodeTIEElement(level=1,
neighbors(
(ToF 21, level 2, cost 1, links(...)),
(ToF 22, level 2, cost 1, links(...)),
(Spine 112, level 1, cost 1, links(...)),
(Leaf111, level 0, cost 1, links(...)),
(Leaf112, level 0, cost 1, links(...))
)
)
Prefix North TIE:
PrefixTIEElement(prefixes(Spine 111.loopback)
Spine 121 South TIEs:
Node South TIE:
NodeTIEElement(level=1,
neighbors(
(ToF 21, level 2, cost 1, links(...)),
(ToF 22, level 2, cost 1, links(...)),
(Leaf121, level 0, cost 1, links(...)),
(Leaf122, level 0, cost 1, links(...))
)
)
Prefix South TIE:
PrefixTIEElement(prefixes(0/0, metric 1), (::/0, metric 1))
Spine 121 North TIEs:
Node North TIE:
NodeTIEElement(level=1,
neighbors(
(ToF 21, level 2, cost 1, links(...)),
(ToF 22, level 2, cost 1, links(...)),
(Leaf121, level 0, cost 1, links(...)),
(Leaf122, level 0, cost 1, links(...))
)
)
Prefix North TIE:
PrefixTIEElement(prefixes(Spine 121.loopback)
Leaf112 North TIEs:
Node North TIE:
NodeTIEElement(level=0,
neighbors(
(Spine 111, level 1, cost 1, links(...)),
(Spine 112, level 1, cost 1, links(...))
)
)
Prefix North TIE:
PrefixTIEElement(prefixes(Leaf112.loopback, Prefix112, Prefix_MH))
Figure 15: Example TIEs Generated in a 2 Level 2-Level Spine-and-Leaf
Topology
It may not be obvious here as to why the Node South TIEs contain all
the adjacencies of the corresponding node. This will be necessary
for algorithms further elaborated on in Section Sections 6.3.9 and
Section 6.8.7.
For Node TIEs to carry more adjacencies than fit into an MTU-sized
packet, the element _neighbors_ element may contain a different set of
neighbors in each TIE. Those disjointed sets of neighbors MUST be
joined during corresponding computation. However, if the following
occurs across multiple Node TIEs TIEs:
1. _capabilities_ do not match *or* match,
2. _flags_ values do not match match, *or*
3. the same neighbor repeats in multiple TIEs with different values values.
The implementation is expected to use the value of any of the valid
TIEs it received received, as it cannot control the arrival order of those
TIEs.
The _miscabled_links_ element SHOULD be included in every Node TIE,
otherwise TIE;
otherwise, the behavior is undefined.
A ToF node MUST include information on all other ToFs it is aware of
through reflection. The _same_plane_tofs_ element is used to carry
this information. To prevent MTU overrun problems, multiple Node
TIEs can carry disjointed sets of ToFs ToFs, which MUST be joined to form
a single set.
Different TIE types are carried in _TIEElement_. Schema enum
`common.TIETypeType`
'common.TIETypeType' in _TIEID_ indicates which elements MUST be
present in the _TIEElement_. In case of a mismatch between the _TIETypeType_
in the _TIEID_ and the present element, the unexpected elements MUST
be ignored. In case of the lack of an expected element in the
TIE TIE,
an error MUST be reported and the TIE MUST be ignored. The
element
_positive_disaggregation_prefixes_ and
_positive_external_disaggregation_prefixes_ elements MUST be
advertised southbound only and ignored in North TIEs. The element
_negative_disaggregation_prefixes_ element MUST be propagated propagated,
according to Section 6.5.2 6.5.2, southwards towards lower levels to heal
pathological upper-level partitioning, otherwise partitioning; otherwise, traffic loss may
occur in
multiplane multi-plane fabrics. It MUST NOT be advertised within a
North TIE and MUST be ignored otherwise.
6.3.3. Flooding
As described before, TIEs themselves are transported over UDP with
the ports indicated in the LIE exchanges and using use the destination
address on which the LIE adjacency has been formed.
TIEs are uniquely identified by the _TIEID_ schema element. The _TIEID_
induces a total order achieved by comparing the elements in sequence
defined in the element and comparing each value as an unsigned
integer of corresponding length. The _TIEHeader_ element contains a
_seq_nr_ element to distinguish newer versions of the same TIE.
The
_TIEHeader_ can also carry an _origination_time_ schema element (for
fabrics that utilize precision timing) which that contains the absolute
timestamp of when the TIE was generated and an _origination_lifetime_
to indicate the original lifetime when the TIE was generated. When
carried, they can be used for debugging or security purposes (e.g. (e.g.,
to prevent lifetime modification attacks). Clock synchronization is
considered in more detail in Section 6.8.4.
_remaining_lifetime_ counts down to 0 from _origination_lifetime_.
TIEs with lifetimes differing by less than _lifetime_diff2ignore_
MUST be considered EQUAL (if all other fields are equal). This
constant MUST be larger than _purge_lifetime_ to avoid
retransmissions.
This normative ordering methodology is described in Figure 16 and
MUST be used by all implementations.
function Compare(X: TIEHeader, Y: TIEHeader) returns Ordering:
seq_nr of a TIEHeader = TIEHeader.seq_nr
TIEID of a TIEHeader = TIEHeader.TIEID
direction of a TIEID = TIEID.direction
# System ID
originator of a TIEID = TIEID.originator
# is of type TIETypeType
tietype of a TIEID = TIEID.tietype
tie_nr of a TIEID = TIEID.tie_nr
if X.direction > Y.direction:
return X is larger
else if X.direction < Y.direction:
return Y is larger
else if X.originator > Y.originator:
return X is larger
else if X.originator < Y.originator:
return Y is larger
else:
if X.tietype == Y.tietype:
if X.tie_nr == Y.tie_nr:
if X.seq_nr == Y.seq_nr:
X.lifetime_left = X.remaining_lifetime
- time since TIE was received
Y.lifetime_left = Y.remaining_lifetime
- time since TIE was received
if absolute_value_of(X.lifetime_left -
Y.lifetime_left) <= common.lifetime_diff2ignore:
return Both are Equal
else:
return TIEHeader with larger lifetime_left is
larger
else:
return return TIEHeader with larger seq_nr is larger
else:
return TIEHeader with larger tie_nr is larger
else:
return TIEHeader with larger TIEType is larger
Figure 16: TIEHeader Comparison Function
All valid TIE types are defined in _TIETypeType_. This enum
indicates what TIE type the TIE is carrying. In case the value is
not known to the receiver, the TIE MUST be re-flooded reflooded with the scope
identical to the scope of a prefix TIE. This allows for future
extensions of the protocol within the same major schema with types
opaque to some nodes with some restrictions defined in Section 7.
6.3.3.1. Normative Flooding Procedures
On reception of a TIE with an undefined level value in the packet
header
header, the node MUST issue a warning and discard the packet.
This section specifies the precise, normative flooding mechanism and
can be omitted unless the reader is pursuing an implementation of the
protocol or looks for a deep understanding of underlying information
distribution mechanism.
Flooding Procedures procedures are described in terms of the flooding state of
an adjacency adjacency, and resulting operations on it are driven by packet
arrivals. Implementations MUST implement a behavior that is
externally indistinguishable from the FSMs and normative procedures
given here.
RIFT does not specify any kind of flood rate limiting. To help with
adjustment of flooding speeds speeds, the encoded packets provide hints to
react accordingly to losses or overruns via
_you_are_sending_too_quickly_ in the _LIEPacket_ and `Packet Number` "Packet Number"
in the security envelope described in Section 6.9.3. Flooding of all
corresponding topology exchange elements SHOULD be performed at the
highest feasible rate rate, but the rate of transmission MUST be throttled
by reacting to packet elements and features of the system system, such as
e.g.
queue lengths or congestion indications in the protocol packets.
A node SHOULD NOT send out any topology information elements if the
adjacency is not in a "ThreeWay" _ThreeWay_ state. No further tightening of
this rule is possible. For example, link buffering may cause both
LIEs and TIEs/TIDEs/TIREs to be re-ordered. reordered.
A node MUST drop any received TIEs/TIDEs/TIREs unless it is in the
_ThreeWay_ state.
TIEs generated by other nodes MUST be re-flooded. reflooded. TIDEs and TIREs
MUST NOT be re-flooded. reflooded.
6.3.3.1.1. FloodState Structure per Adjacency
The
For each adjacency, the structure contains conceptually for each adjacency contains the following
elements. The word "collection" or "queue" indicates a set of
elements that can be iterated over: over the following:
TIES_TX:
Collection containing all the TIEs to transmit on the adjacency.
TIES_ACK:
Collection containing all the TIEs that have to be acknowledged on
the adjacency.
TIES_REQ:
Collection containing all the TIE headers that have to be
requested on the adjacency.
TIES_RTX:
Collection containing all TIEs that need retransmission with the
corresponding time to retransmit.
FILTERED_TIEDB:
A filtered view of TIEDB, which retains for consideration only
those headers permitted by is_tide_entry_filtered and which either
have a lifetime left > 0 or have no content.
Following
The following words are used for well-known elements and procedures
operating on this structure:
TIE:
Describes
describes either a full RIFT TIE or just the _TIEHeader_ or
_TIEID_ equivalent equivalent, as defined in Section 7.3. The corresponding
meaning is unambiguously contained in the context of each
algorithm.
is_flood_reduced(TIE):
returns whether a TIE can be flood reduced flood-reduced or not.
is_tide_entry_filtered(TIE):
returns whether a header should be propagated in TIDE according to
flooding scopes.
is_request_filtered(TIE):
returns whether a TIE request should be propagated to the neighbor
or
not not, according to flooding scopes.
is_flood_filtered(TIE):
returns whether a TIE requested be flooded to the neighbor or not not,
according to flooding scopes.
try_to_transmit_tie(TIE):
A.
if not is_flood_filtered(TIE) is_flood_filtered(TIE), then
1. remove the TIE from TIES_RTX if present
2. if the TIE with same key is found on TIES_ACK TIES_ACK, then
a. if the TIE is the same as or newer than TIE TIE, do nothing nothing,
else
b. remove the TIE from TIES_ACK and add TIE to TIES_TX
3. else insert the TIE into TIES_TX TIES_TX.
ack_tie(TIE):
remove the TIE from all collections and then insert the TIE into
TIES_ACK.
tie_been_acked(TIE):
remove the TIE from all collections.
remove_from_all_queues(TIE):
same as _tie_been_acked_.
request_tie(TIE):
if not is_request_filtered(TIE) is_request_filtered(TIE), then remove_from_all_queues(TIE)
and add to TIES_REQ.
move_to_rtx_list(TIE):
remove the TIE from TIES_TX and then add to TIES_RTX TIES_RTX, using the
TIE retransmission interval.
clear_requests(TIEs):
remove all TIEs from TIES_REQ.
bump_own_tie(TIE):
for a self-originated TIE TIE, originate an empty or re-generate regenerate with
the version number higher than the one in the TIE.
The collection SHOULD be served with the following priorities if the
system cannot process all the collections in real time:
1. Elements on TIES_ACK should be processed with highest priority
2. TIES_TX
3. TIES_REQ and TIES_RTX should be processed with lowest priority
6.3.3.1.2. TIDEs
_TIEID_ and _TIEHeader_ space forms spaces form a strict total order (modulo
incomparable sequence numbers (found in `TIEHeader.seq_nr`) "TIEHeader.seq_nr"), as
explained in Appendix A A, in the very unlikely event that can occur if a TIE is
"stuck" in a part of a network while the originator reboots and
reissues TIEs many times to the point its sequence# sequence number rolls over
and forms an incomparable distance to the "stuck" copy) copy), which
implies that a comparison relation is possible between two elements.
With
that that, it is implicitly possible to compare TIEs, TIEHeaders TIEHeaders, and
TIEIDs to each other other, whereas the shortest viable key is always
implied.
6.3.3.1.2.1. TIDE Generation
As given by the timer constant, periodically generate TIDEs by:
NEXT_TIDE_ID: ID of the next TIE to be sent in the TIDE.
a.
1. NEXT_TIDE_ID = MIN_TIEID
b.
2. while NEXT_TIDE_ID is not equal to MAX_TIEID MAX_TIEID, do
1. the following:
a. HEADERS = Exactly TIRDEs_PER_PKT headers from FILTERED_TIEDB
starting at NEXT_TIDE_ID, unless fewer than TIRDEs_PER_PKT
remain, in which case all remaining headers.
2.
b. if HEADERS is empty empty, then START = MIN_TIEID MIN_TIEID, else START =
first element in HEADERS
3.
c. if HEADERS' size is less than TIRDEs_PER_PKT TIRDEs_PER_PKT, then END =
MAX_TIEID
MAX_TIEID, else END = last element in HEADERS
4.
d. send *sorted* HEADERS the as TIDE TIDE, setting START and END as
its range
5.
e. NEXT_TIDE_ID = END
The constant _TIRDEs_PER_PKT_ SHOULD be computed per interface and
used by the implementation to limit the amount of TIE headers per
TIDE so the sent TIDE PDU does not exceed the interface of MTU.
TIDE PDUs SHOULD be spaced on sending to prevent packet drops.
The algorithm will intentionally enter the loop once and send a
single TIDE TIDE, even when the database is empty, otherwise empty; otherwise, no TIDEs
would be sent for in case of an empty database and break the intended
synchronization.
6.3.3.1.2.2. TIDE Processing
On reception of TIDEs TIDEs, the following processing is performed:
TXKEYS: Collection of TIE Headers headers to be sent after processing of the
packet
REQKEYS: Collection of TIEIDs to be requested after processing of
the packet
CLEARKEYS: Collection of TIEIDs to be removed from flood state
queues
LASTPROCESSED: Last processed TIEID in the TIDE
DBTIE: TIE in the Link State Database (LSDB) (LSDB), if found
a.
1. LASTPROCESSED = TIDE.start_range
b. for
2. For every HEADER in TIDE the TIDE, do
1. the following:
a. DBTIE = find HEADER in the current LSDB
2.
b. if HEADER < LASTPROCESSED LASTPROCESSED, then report the error and reset
the adjacency and return
3.
c. put all TIEs in LSDB LSDB, where (TIE.HEADER TIE.HEADER > LASTPROCESSED and
TIE.HEADER < HEADER) HEADER, into TXKEYS
4.
d. LASTPROCESSED = HEADER
5.
e. if DBTIE is not found found, then
I)
i. if originator is this node, then bump_own_tie
II)
ii. else put HEADER into REQKEYS
6.
f. if DBTIE.HEADER < HEADER HEADER, then
I)
i. if the originator is this node node, then bump_own_tie bump_own_tie, else
i.
1. if this is a North TIE header from a northbound
neighbor
neighbor, then override DBTIE in LSDB with HEADER
ii.
2. else put HEADER into REQKEYS
7.
g. if DBTIE.HEADER > HEADER HEADER, then put DBTIE.HEADER into TXKEYS
8.
h. if DBTIE.HEADER = HEADER HEADER, then
I)
i. if DBTIE has content already already, then put DBTIE.HEADER into
CLEARKEYS
II)
CLEARKEYS, else
ii. put HEADER into REQKEYS
c.
3. put all TIEs in LSDB LSDB, where (TIE.HEADER TIE.HEADER > LASTPROCESSED and
TIE.HEADER <= TIDE.end_range) TIDE.end_range, into TXKEYS
d.
4. for all TIEs in TXKEYS TXKEYS, try_to_transmit_tie(TIE)
e.
5. for all TIEs in REQKEYS REQKEYS, request_tie(TIE)
f.
6. for all TIEs in CLEARKEYS CLEARKEYS, remove_from_all_queues(TIE)
6.3.3.1.3. TIREs
6.3.3.1.3.1. TIRE Generation
Elements from both TIES_REQ and TIES_ACK MUST be collected and sent
out as fast as feasible as TIREs. When sending TIREs with elements
from TIES_REQ TIES_REQ, the _remaining_lifetime_ field in
_TIEHeaderWithLifeTime_ MUST be set to 0 to force reflooding from the
neighbor even if the TIEs seem to be the same.
6.3.3.1.3.2. TIRE Processing
On reception of TIREs TIREs, the following processing is performed:
TXKEYS: Collection of TIE Headers headers to be sent after processing of the
packet
REQKEYS: Collection of TIEIDs to be requested after processing of
the packet
ACKKEYS: Collection of TIEIDs that have been acked acknowledged
DBTIE: TIE in the LSDB LSDB, if found
a.
1. for every HEADER in TIRE TIRE, do
1. the following:
a. DBTIE = find HEADER in the current LSDB
2.
b. if DBTIE is not found found, then do nothing
3.
c. if DBTIE.HEADER < HEADER HEADER, then put HEADER into REQKEYS
4.
d. if DBTIE.HEADER > HEADER HEADER, then put DBTIE.HEADER into TXKEYS
5.
e. if DBTIE.HEADER = HEADER HEADER, then put DBTIE.HEADER into ACKKEYS
b.
2. for all TIEs in TXKEYS TXKEYS, try_to_transmit_tie(TIE)
c.
3. for all TIEs in REQKEYS REQKEYS, request_tie(TIE)
d.
4. for all TIEs in ACKKEYS ACKKEYS, tie_been_acked(TIE)
6.3.3.1.4. TIEs Processing on Flood State Adjacency
On reception of TIEs TIEs, the following processing is performed:
ACKTIE: TIE to acknowledge
TXTIE: TIE to transmit
DBTIE: TIE in the LSDB LSDB, if found
a.
1. DBTIE = find TIE in the current LSDB
b.
2. if DBTIE is not found found, then
1.
a. if the originator is this node node, then bump_own_tie with a
short remaining lifetime
2. lifetime, else
b. insert TIE into LSDB and ACKTIE = TIE
else
1.
a. if DBTIE.HEADER = TIE.HEADER TIE.HEADER, then
i. if DBTIE has content already already, then ACKTIE = TIE
ii. TIE, else
ii. process like the "DBTIE.HEADER < TIE.HEADER" case
2.
b. if DBTIE.HEADER < TIE.HEADER TIE.HEADER, then
i. if the originator is this node node, then bump_own_tie
ii. bump_own_tie, else
ii. insert TIE into LSDB and ACKTIE = TIE
3.
c. if DBTIE.HEADER > TIE.HEADER TIE.HEADER, then
i. if DBTIE has content already already, then TXTIE = DBTIE
ii. DBTIE, else
ii. ACKTIE = DBTIE
c.
3. if TXTIE is set set, then try_to_transmit_tie(TXTIE)
d.
4. if ACKTIE is set set, then ack_tie(TIE)
6.3.3.1.5. Sending TIEs
On a periodic basis basis, all TIEs with a lifetime left of > 0 left MUST be
sent out on the adjacency, removed from the TIES_TX list list, and
requeued onto TIES_RTX list. The specific period is out of scope for
this document.
6.3.3.1.6. TIEs Processing In in LSDB
The Link State Database (LSDB) holds the most recent copy of TIEs
received via flooding from according peers. Consecutively, after
version tie-breaking by LSDB, a peer receives from the LSDB the
newest versions of TIEs received by other peers and processes them
(without any filtering) just like receiving TIEs from its remote
peer. Such a publisher model can be implemented in several ways,
either in a single thread of execution or in multiple parallel
threads.
LSDB can be logically considered as the entity aging out TIEs, i.e. i.e.,
being responsible to discard TIEs that are stored longer than
_remaining_lifetime_ on their reception.
LSDB is also expected to periodically re-originate reoriginate the node's own
TIEs. Originating at an interval significantly shorter than
_default_lifetime_ is RECOMMENDED to prevent TIE expiration by other
nodes in the network network, which can lead to instabilities.
6.3.4. TIE Flooding Scopes
In a somewhat analogous fashion to link-local, area area, and domain
flooding scopes, RIFT defines several complex "flooding scopes" scopes",
depending on the direction and type of TIE propagated.
Every North TIE is flooded northbound, providing a node at a given
level with the complete topology of the Clos or Fat Tree network that
is reachable southwards of it, including all specific prefixes. This
means that a packet received from a node at the same or lower level
whose destination is covered by one of those specific prefixes will
be routed directly towards the node advertising that prefix prefix, rather
than sending the packet to a node at a higher level.
A node's Node South TIEs, consisting of all node's adjacencies and
prefix South TIEs limited to those related to default IP prefix and
disaggregated prefixes, are flooded southbound in order to inform
nodes one level down of connectivity of the higher level as well as
reachability to the rest of the fabric. In order to allow an E-W
disconnected node in a given level to receive the South TIEs of other
nodes at its level, every *NODE* Node South TIE is "reflected" northbound to
the level from which it was received. It should be noted that
East-West East-
West links are included in South TIE flooding (except at the ToF
level); those TIEs need to be flooded to satisfy the algorithms
described in Section 6.4. In that way way, nodes at same level can learn
about each other using without using a lower level except in case of leaf
level. The precise, normative flooding scopes are given in Table 3.
Those rules also govern what SHOULD be included in TIDEs on the
adjacency. Again, East-West flooding scopes are identical to South
southern flooding
scopes scopes, except in case of ToF East-West links (rings)
(rings), which are basically performing northbound flooding.
Node South TIE "south reflection" enables support of positive
disaggregation on failures failures, as described in Section 6.5 6.5, and flooding
reduction
reduction, as described in Section 6.3.9.
+===========+======================+==============+=================+
| Type / | South | North | East-West |
| Direction | | | |
+===========+======================+==============+=================+
| Node | flood if the level of | flood if the | flood only if |
| South TIE | of the originator is | level of the | this node is |
| | is equal to this | originator | not ToF |
| | node | is higher | |
| | | than this | |
| | | node | |
+-----------+----------------------+--------------+-----------------+
| non-Node | flood self- | flood only | flood only if |
| South TIE | originated only | if neighbor the | self-originated it is self- |
| | | neighbor is | originated and |
| | | the | this node is |
| | | originator | is not ToF |
| | | of TIE | |
+-----------+----------------------+--------------+-----------------+
| all North | never flood | flood always | flood only if |
| TIEs | | | this node is |
| | | | ToF |
+-----------+----------------------+--------------+-----------------+
| TIDE | include at least | include at | if this node is |
| | all non-self non-self- | least all | ToF ToF, then |
| | originated North | Node South | include all |
| | TIE headers and | TIEs and all | North TIEs, TIEs; |
| | self-originated | South TIEs | otherwise otherwise, only |
| | South TIE headers | originated | self-originated include self- |
| | and Node South TIEs | by a peer and | originated TIEs |
| | TIEs of nodes at same | and all North | |
| | same level | North TIEs | |
+-----------+----------------------+--------------+-----------------+
| TIRE as | request all North | request all | if this node is |
| Request | TIEs and all peer's | South TIEs | ToF ToF, then apply |
| | peer's self- self-originated | | North north scope |
| | originated TIEs | | rules, |
| | and all Node | | otherwise South rules; |
| | South TIEs | | otherwise, |
| | | | apply south |
| | | | scope rules |
+-----------+----------------------+--------------+-----------------+
| TIRE as | Ack all received | Ack all | Ack all |
| Ack | TIEs | received | received TIEs |
| | | TIEs | |
+-----------+----------------------+--------------+-----------------+
Table 3: Normative Flooding Scopes
If the TIDE includes additional TIE headers beside the ones
specified, the receiving neighbor must apply the corresponding filter
to the received TIDE strictly and MUST NOT request the extra TIE
headers that were not allowed by the flooding scope rules in its
direction.
To illustrate these rules, consider using the topology in Figure 2,
with the optional link between spine 111 and spine 112, and the
associated TIEs given in Figure 15. The flooding from particular
nodes of the TIEs is given in Table 4.
+============+==========+===========================================+
| Local | Neighbor | TIEs Flooded from Local to Neighbor Node |
| Node | Node | |
+============+==========+===========================================+
| Leaf111 | Spine | Leaf111 North TIEs, Spine 111 Node South |
| | 112 | TIE |
+------------+----------+-------------------------------------------+
| Leaf111 | Spine | Leaf111 North TIEs, Spine 112 Node South |
| | 111 | TIE |
+------------+----------+-------------------------------------------+
| ... | ... | ... |
+------------+----------+-------------------------------------------+
| Spine | Leaf111 | Spine 111 South TIEs |
| 111 | | |
+------------+----------+-------------------------------------------+
| Spine | Leaf112 | Spine 111 South TIEs |
| 111 | | |
+------------+----------+-------------------------------------------+
| Spine | Spine | Spine 111 South TIEs |
| 111 | 112 | |
+------------+----------+-------------------------------------------+
| Spine | ToF 21 | Spine 111 North TIEs, Leaf111 North TIEs, |
| 111 | | Leaf112 North TIEs, ToF 22 Node South TIE |
+------------+----------+-------------------------------------------+
| Spine | ToF 22 | Spine 111 North TIEs, Leaf111 North TIEs, |
| 111 | | Leaf112 North TIEs, ToF 21 Node South TIE |
+------------+----------+-------------------------------------------+
| ... | ... | ... |
+------------+----------+-------------------------------------------+
| ToF 21 | Spine | ToF 21 South TIEs |
| | 111 | |
+------------+----------+-------------------------------------------+
| ToF 21 | Spine | ToF 21 South TIEs |
| | 112 | |
+------------+----------+-------------------------------------------+
| ToF 21 | Spine | ToF 21 South TIEs |
| | 121 | |
+------------+----------+-------------------------------------------+
| ToF 21 | Spine | ToF 21 South TIEs |
| | 122 | |
+------------+----------+-------------------------------------------+
| ... | ... | ... |
+------------+----------+-------------------------------------------+
Table 4: Flooding some Some TIEs from example topology Example Topology
6.3.5. RAIN: RIFT Adjacency Inrush Notification
The optional RIFT Adjacency Inrush Notification (RAIN) mechanism
helps to prevent adjacencies from being overwhelmed by flooding on
restart or bring-up with many southbound neighbors. A In its LIEs, a
node MAY set
in its LIEs the corresponding _you_are_sending_too_quickly_ flag to
indicate to the neighbor that it SHOULD flood Node TIEs with normal
speed and significantly slow down the flooding of any other TIEs.
The flag SHOULD be set only in the southbound direction. The
receiving node SHOULD accommodate the request to lessen the flooding
load on the affected node if it is south of the sender and should
ignore the indication if it is north of the sender.
The distribution of Node TIEs at normal speed speed, even at high load load,
guarantees correct behavior of algorithms like disaggregation or
default route origination. Furthermore though, the use of this bit
presents an inherent trade-off between processing load and
convergence speed since significantly slowing down flooding of
northbound prefixes from neighbors for an extended time will lead to
traffic losses.
6.3.6. Initial and Periodic Database Synchronization
The initial exchange of RIFT includes periodic TIDE exchanges that
contain description descriptions of the link state database and TIREs TIREs, which
perform the function of requesting unknown TIEs as well as confirming
the reception of flooded TIEs. The content of TIDEs and TIREs is
governed by Table 3.
6.3.7. Purging and Roll-Overs Rollovers
When a node exits in the network, if "unpurged", residual stale TIEs
may exist in the network until their lifetimes expire (which in case
of RIFT is by default a rather long period to prevent ongoing re-
origination
reorigination of TIEs in very large topologies). RIFT does not have
a "purging mechanism" based on sending specialized "purge" packets.
In other routing protocols protocols, such a mechanism has proven to be complex
and fragile based on many years of experience. RIFT simply issues a
new, i.e., higher sequence number, empty version of the TIE with a
short lifetime given by the _purge_lifetime_ constant and relies on
each node to age out and delete each TIE copy independently.
Abundant amounts of memory are available today today, even on low-end platforms
platforms, and
hence hence, keeping those relatively short-lived extra
copies for a while is acceptable. The information will age out and and,
in the meantime meantime, all computations will deliver correct results if a
node leaves the network due to the new information distributed by its
adjacent nodes breaking bi-directional bidirectional connectivity checks in
different computations.
Once a RIFT node issues a TIE with an ID, it SHOULD preserve the ID
as long as feasible (also when the protocol restarts), even if the
TIE looses all content. The re-advertisement of an empty TIE
fulfills the purpose of purging any information advertised in
previous versions. The originator is free to not re-originate reoriginate the
corresponding empty TIE again or originate an empty TIE with a
relatively short lifetime to prevent a large number of long-lived
empty stubs polluting the network. Each node MUST time out and clean
up the corresponding empty TIEs independently.
Upon restart restart, a node MUST be prepared to receive TIEs with its own
System ID and supersede them with equivalent, newly generated, empty
TIEs with a higher sequence number. As above, the lifetime can be
relatively short since it only needs to exceed the necessary
propagation and processing delay by all the nodes that are within the
TIE's flooding scope.
TIE sequence numbers are rolled over using the method described in
Appendix A . First The first sequence number of any spontaneously
originated TIE (i.e. (i.e., not originated to override a detected older
copy in the network) MUST be a reasonably unpredictable random number
(for
example example, [RFC4086]) in the interval [0, 2^30-1] 2^30-1], which will
prevent otherwise identical TIE headers to remain "stuck" in the
network with content different from the TIE originated after reboot.
In traditional link-state protocols protocols, this is delegated to a 16-bit
checksum on packet content. RIFT avoids this design due to the CPU
burden presented by computation of such checksums and additional
complications tied to the fact that the checksum must be "patched"
into the packet after the generation of the content, which is a
difficult proposition in binary binary, hand-crafted formats already and
highly incompatible with model-
based, model-based, serialized formats. The
sequence number space is hence consciously chosen to be 64-bits wide
to make the occurrence of a TIE with the same sequence number but
different content as much or even more unlikely than the checksum
method. To emulate the "checksum
behavior" behavior", an implementation could
choose to compute a 64-bit checksum or hash function over the TIE
content and use that as part of the first sequence number after
reboot.
6.3.8. Southbound Default Route Origination
Under certain conditions conditions, nodes issue a default route in their South
Prefix TIEs with costs as computed in Section 6.8.7.1.
A node X that
1. is *not* overloaded *and*
2. has southbound or East-West adjacencies
SHOULD originate such a default route in its south prefix TIE such a default route if and
only if
1. all other nodes at X's' level are overloaded *or* overloaded,
2. all other nodes at X's' level have NO northbound adjacencies adjacencies,
*or*
3. X has computed reachability to a default route during N-SPF.
The term "all other nodes at X's' level" describes level " obviously describes just
the nodes at the same level in the PoD with a viable lower level
(otherwise
(otherwise, the Node South TIEs cannot be reflected. The reflected; the nodes in PoD
1 and PoD 2 are "invisible" to each other).
A node originating a southbound default route SHOULD install a
default discard route if it did not compute a default route during
N-SPF. This basically means that the top of the fabric will drop
traffic for unreachable addresses.
6.3.9. Northbound TIE Flooding Reduction
RIFT chooses only a subset of northbound nodes to propagate flooding
and
and, with that that, both balances it (to prevent 'hot' "hot" flooding links)
across the fabric as well as reduces its volume. The solution is
based on several principles:
1. a node MUST flood self-originated North TIEs to all the reachable
nodes at the level above above, which is called the node's "parents";
2. it is typically not necessary that all parents reflood the North
TIEs to achieve a complete flooding of all the reachable nodes
two levels above above, which we call the node's "grandparents";
3. to control the volume of its flooding two hops North north and yet keep
it robust enough, it is advantageous for a node to select a
subset of its parents as "Flood Repeaters" (FRs), which when
combined, deliver two or more copies of its flooding to all of
its parents, i.e. i.e., the originating node's grandparents;
4. nodes at the same level do *not* have to agree on a specific
algorithm to select the FRs, but overall load balancing should be
achieved so that different nodes at the same level should tend to
select different parents as FRs (consideration of possible
strategies in an unrelated but similar field can be found in
[RFC2991]);
5. there are usually many solutions to the problem of finding a set
of FRs for a given node; the problem of finding the minimal set
is (similar to) a an NP-Complete problem problem, and a globally optimal
set may not be the minimal one if load-balancing load balancing with other nodes
is an important consideration;
6. it is expected that there will often exist sets of equivalent nodes at a level L, L will
often exist, defined as having a common set of parents at L+1.
Applying this observation at both L and L+1, an algorithm may
attempt to split the larger problem in a sum of smaller smaller, separate
problems; and
7. it is expected that there will be from time to time a broken link between a parent
and a grandparent, grandparent from time to time, and in that case case, the parent
is probably a poor FR due to its lower reliability. An algorithm
may attempt to eliminate parents with broken northbound
adjacencies first in order to reduce the number of FRs. Albeit
it could be argued that relying on higher fanout FRs will slow
flooding due to higher replication, load reliability of FR's
links is likely a more pressing concern.
In a fully connected Clos Network, network, this means that a node selects one
arbitrary parent as the FR and then a second one for redundancy. The
computation can be relatively simple and completely distributed
without any need for synchronization among nodes. In a "PoD"
structure, where the Level level L+2 is partitioned into silos of
equivalent grandparents that are only reachable from respective
parents, this means treating each silo as a fully connected Clos
Network
network and solving the problem within the silo.
In terms of signaling, a node has enough information to select its
set of FRs; this information is derived from the node's parents' Node
South TIEs, which indicate the parent's reachable northbound
adjacencies to its own parents (the node's grandparents). A node may
send a LIE to a northbound neighbor with the optional boolean field
_you_are_flood_repeater_ set to false, false to indicate that the northbound
neighbor is not a flood repeater for the node that sent the LIE. In
that case case, the northbound neighbor SHOULD NOT reflood northbound TIEs
received from the node that sent the LIE. If the
_you_are_flood_repeater_ is absent or if _you_are_flood_repeater_ is set
to true, then the northbound neighbor is a flood repeater for the
node that sent the LIE and MUST reflood northbound TIEs received from
that node. The element _you_are_flood_repeater_ MUST be ignored if
received from a northbound adjacency.
This specification provides a simple default algorithm that SHOULD be
implemented and used by default on every RIFT node.
* let |NA(Node) be the set of Northbound northbound adjacencies of node Node
and CN(Node) be the cardinality of |NA(Node);
* let |SA(Node) be the set of Southbound southbound adjacencies of node Node
and CS(Node) be the cardinality of |SA(Node);
* let |P(Node) be the set of node Node's parents;
* let |G(Node) be the set of node Node's grandparents. Observe
that |G(Node) = |P(|P(Node));
* let N be the child node at level L computing a set of FR; FRs;
* let P be a node at level L+1 and a parent node of N, i.e. bi-
directionally i.e.,
bidirectionally reachable over adjacency ADJ(N, P);
* let G be a grandparent node of N, reachable transitively via a
parent P over adjacencies ADJ(N, P) and ADJ(P, G). Observe that N
does not have enough information to check bidirectional
reachability of ADJ(P, G);
* let R be a redundancy constant integer; a value of 2 or higher for
R is RECOMMENDED;
* let S be a similarity similarly constant integer; a value in range 0 .. 2 for
S is RECOMMENDED, and the value of 1 SHOULD be used. Two
cardinalities are considered as equivalent if their absolute
difference is less than or equal to S, i.e. |a-b|<=S. i.e., |a-b|<=S; and
* let RND be a 64-bit random number (for example example, as described in
[RFC4086]) generated by the system once on startup.
The algorithm consists of the following steps:
1. Derive a 64-bits 64-bit number by XOR'ing 'N's XORing N's System ID with RND.
2. Derive a 16-bits 16-bit pseudo-random unsigned integer PR(N) from the
resulting 64-bits 64-bit number by splitting it in 16-bits-long into 16-bit-long words
W1, W2, W3, W4 (where W1 are the least significant 16 bits of the
64-bits
64-bit number, and W4 are the most significant 16 bits) and then
XOR'ing
XORing the circularly shifted resulting words together:
A.
(W1<<1) xor (W2<<2) xor (W3<<3) xor (W4<<4); where << is the
circular shift operator.
3. Sort the parents by decreasing number of northbound adjacencies
(using decreasing System ID of the parent as a tie-breaker):
sort |P(N) by decreasing CN(P), for all P in |P(N), as the
ordered array |A(N)
4. Partition |A(N) in subarrays |A_k(N) of parents with equivalent
cardinality of northbound adjacencies (in other words words, with
equivalent number of grandparents they can reach):
A.
a. set k=0; // k is the ID of the subarrray
B. subarray
b. set i=0;
C.
c. while i < CN(N) do
i) the following:
i. set j=i;
ii)
ii. while i < CN(N) and CN(|A(N)[j]) - CN(|A(N)[i]) <= S
a. S:
1. place |A(N)[i] in |A_k(N) // abstract action, maybe
noop
b.
2. set i=i+1;
iii)
iii. /* At this point point, j is the index in |A(N) of the first
member of |A_k(N) and (i-j) is C_k(N) defined as the
cardinality of |A_k(N) |A_k(N). */
set k=k+1; k=k+1.
/* At this point point, k is the total number of subarrays, initialized
for the shuffling operation below below. */
5. shuffle individually Shuffle each subarrays |A_k(N) of cardinality C_k(N) within |A(N)
individually using the Durstenfeld variation of the Fisher-Yates
algorithm that depends on N's System ID:
A.
a. while k > 0 do
i) the following:
i. for i from C_k(N)-1 to 1 decrementing by 1 1, do
a. the
following:
1. set j to PR(N) modulo i;
b.
2. exchange |A_k[j] and |A_k[i];
ii)
ii. set k=k-1; k=k-1.
6. For each grandparent G, initialize a counter c(G) with the number
of its south-bound southbound adjacencies to elected flood repeaters (which
is initially zero):
A.
a. for each G in |G(N) |G(N), set c(G) = 0; 0.
7. Finally Finally, only keep as FRs only as parents that are needed to maintain the
number of adjacencies between the FRs and any grandparent G equal
or above the redundancy constant R:
A.
a. for each P in reshuffled |A(N);
i) |A(N):
i. if there exists an adjacency ADJ(P, G) in |NA(P) such
that c(G) < R R, then
a.
1. place P in FR set;
b.
2. for all adjacencies ADJ(P, G') in |NA(P) increment
c(G')
B.
8. If any c(G) is still < R, it was not possible to elect a set of
FRs that covers all grandparents with redundancy R
Additional rules for flooding reduction:
1. The algorithm MUST be re-evaluated by a node on every change of
local adjacencies or reception of a parent South TIE with changed
adjacencies. A node MAY apply a hysteresis to prevent an
excessive amount of computation during periods of network
instability just like in the case of reachability computation.
2. Upon a change of the flood repeater set, a node SHOULD send out
LIEs that grant flood repeater status to newly promoted nodes
before it sends LIEs that revoke the status to the nodes that
have been newly demoted. This is done to prevent transient
behavior where the full coverage of grandparents is not
guaranteed. Such a condition is sometimes unavoidable in case of
lost LIEs LIEs, but it will correct itself though at possible transient
reduction in flooding propagation speeds. The election can use
the LIE FSM _FloodLeadersChanged_ event to notify LIE FSMs of the
necessity to update the sent LIEs.
3. A node MUST always flood its self-originated TIEs to all its
neighbors.
4. A node receiving a TIE originated by a node for which it is not a
flood repeater SHOULD NOT reflood such TIEs to its neighbors neighbors,
except for the rules described in Section 6.3.9, Paragraph 10,
Item 6.
5. The indication of flood reduction capability MUST be carried in
the Node TIEs in the _flood_reduction_ element and MAY be used to
optimize the algorithm to account for nodes that will flood
regardless.
6. A node generates TIDEs as usual usual, but when receiving TIREs or
TIDEs resulting in requests for a TIE of which the newest
received copy came on an adjacency where the node was not a flood repeater
repeater, it SHOULD ignore such requests on first and only first
request. Normally, the nodes that received the TIEs as flooding
repeaters should satisfy the requesting node and and, with that that, no
further TIREs for such TIEs will be generated. Otherwise, the
next set of TIDEs and TIREs MUST lead to flooding independent of
the flood repeater status. This solves a very difficult incast "incast"
problem on nodes restarting with a very wide fanout, especially
northbound. To retrieve the full database database, they often end up
processing many
in-rushing copies inrushing copies, whereas this approach load-balances load
balances the incoming database between adjacent nodes and flood
repeaters and should guarantee that two copies are sent by
different nodes to ensure against any losses.
6.3.10. Special Considerations
First, due to the distributed, asynchronous nature of ZTP, it can
create temporary convergence anomalies where nodes at higher levels
of the fabric temporarily become lower than where they ultimately
belong. Since flooding can begin before ZTP is "finished" and in
fact must do so given there is no global termination criteria for the
unsychronized
unsynchronized ZTP algorithm, information may temporarily end up temporarily in
wrong layers. A special clause when changing level takes care of
that.
More difficult is a condition where a node (e.g. (e.g., a leaf) floods a
TIE north towards its grandparent, then its parent reboots,
partitioning the grandparent from the leaf directly directly, and then the
leaf itself reboots. That can leave the grandparent holding the
"primary copy" of the leaf's TIE. Normally Normally, this condition is
resolved easily by the leaf
re-originating reoriginating its TIE with a higher
sequence number than it notices in the northbound TIEs, TIEs; here however,
when the parent comes back back, it won't be able to obtain the leaf's
North TIE from the grandparent easily easily, and with that that, the leaf may
not issue the TIE with a higher sequence number that can reach the
grandparent for a long time. Flooding procedures are extended to
deal with the problem by the means of special clauses that override
the database of a lower level with headers of newer TIEs received in
TIDEs coming from the north. Those headers are then propagated
southbound towards the leaf to cause it to originate a higher
sequence number of the TIE TIE, effectively refreshing it all the way up
to ToF.
6.4. Reachability Computation
A node has three possible sources of relevant information for
reachability computation. A node knows the full topology south of it
from the received North Node TIEs or alternately north of it from the
South Node TIEs. A node has the set of prefixes with their
associated distances and bandwidths from corresponding prefix TIEs.
To compute prefix reachability, a node runs conceptually runs a northbound
and a southbound SPF. Here, N-SPF and S-SPF notation denotes here the
direction in which the computation front is progressing.
Since neither computation can "loop", it is possible to compute non-
equal-cost
equal costs or even k-shortest paths [EPPSTEIN] and "saturate" the
fabric to the extent desired. This specification however uses
simple, familiar SPF algorithms and concepts as example examples due to their
prevalence in today's routing.
For reachability computation purposes, RIFT considers all parallel
links between two nodes to be of the same cost advertised in the
_cost_ element of _NodeNeighborsTIEElement_. In case the neighbor has
multiple parallel links at different cost, costs, the largest distance
(highest numerical value) MUST be advertised. Given the range of
thrift
Thrift encodings, _infinite_distance_ is defined as the largest non-
negative _MetricType_. Any link with a metric larger than that (i.e. (i.e.,
the negative MetricType) MUST be ignored in computations. Any link
with the metric set to _invalid_distance_ MUST also be ignored in
computation. In case of a negatively distributed prefix prefix, the metric
attribute MUST be set to _infinite_distance_ by the originator originator, and
it MUST be ignored by all nodes during computation computation, except for the
purpose of determining transitive propagation and building the
corresponding routing table.
A prefix can carry the _directly_attached_ attribute to indicate that
the prefix is directly attached, i.e., should be routed to even if
the node is in overload. In case of a negatively distributed prefix prefix,
this attribute MUST NOT be included by the originator originator, and it MUST be
ignored by all nodes during SPF computation. If a prefix is locally
originated
originated, the attribute _from_link_ can indicate the interface to
which the address belongs to. In case of a negatively distributed
prefix
prefix, this attribute MUST NOT be included by the originator originator, and it
MUST be ignored by all nodes during computation. A prefix can also
carry the _loopback_ attribute to indicate the said property.
Prefixes are carried in different types of TIEs indicating their
type. For the same prefix being included in different TIE types tie-
breaking types,
tie-breaking is performed according to Section 6.8.1. If the same
prefix is included multiple times in multiple TIEs of the same type
originating at the same node node, the resulting behavior is unspecified.
6.4.1. Northbound Reachability SPF
N-SPF MUST use exclusively northbound and East-West adjacencies in
the computing node's node North TIEs (since if the node is a leaf leaf, it
may not have generated a Node South TIE) when starting SPF. Observe
that N-SPF is really just a one hop one-hop variety since Node South TIEs are
not re-flooded reflooded southbound beyond a single level (or East-West) East-West), and
with that that, the computation cannot progress beyond adjacent nodes.
Once progressing, the computation uses the next higher level's Node
South TIEs to find corresponding adjacencies to verify backlink
connectivity. Two unidirectional links MUST be associated to confirm
bidirectional connectivity, a process often known as `backlink
check`. "backlink
check". As part of the check, both Node TIEs MUST contain the
correct System IDs *and* expected levels.
The default route found when crossing an E-W link SHOULD be used if
and only if if:
1. the node itself does *not* have any northbound adjacencies *and*
2. the adjacent node has one or more northbound adjacencies
This rule forms a "one-hop default route split-horizon" and prevents
looping over default routes while allowing for "one-hop protection"
of nodes that lost all northbound adjacencies adjacencies, except at the ToF
where the links are used exclusively to flood topology information in
multi-plane designs.
Other south prefixes found when crossing E-W link links MAY be used if and
only if
1. no north neighbors are advertising the same or a supersuming non-
default prefix *and*
2. the node does not originate a non-default supersuming prefix
itself.
I.e.,
That is, the E-W link can be used as a gateway of last resort for a
specific prefix only. Using south prefixes across an E-W link can be
beneficial
beneficial, e.g., on automatic disaggregation in pathological fabric
partitioning scenarios.
A detailed example can be found in Appendix B.4.
6.4.2. Southbound Reachability SPF
S-SPF MUST use the southbound adjacencies in the Node South TIEs
exclusively, i.e. i.e., progresses towards nodes at lower levels. Observe
that E-W adjacencies are NEVER used in this computation. This
enforces the requirement that a packet traversing in a southbound
direction must never change its direction.
S-SPF MUST use northbound adjacencies in node North TIEs to verify
backlink connectivity by checking for the presence of the link beside
the correct System ID and level.
6.4.3. East-West Forwarding Within a non-ToF Non-ToF Level
Using south prefixes over horizontal links MAY occur if the N-SPF
includes East-West adjacencies in computation. It can protect
against pathological fabric partitioning cases that leave only paths
to destinations that would necessitate multiple changes of the
forwarding direction between north and south.
6.4.4. East-West Links Within a ToF Level
E-W ToF links behave in terms of flooding scopes defined in
Section 6.3.4 like northbound links and MUST be used exclusively for
control plane information flooding. Even though a ToF node could be
tempted to use those links during southbound SPF and carry traffic
over them them, this MUST NOT be attempted since it may, in anycast cases,
lead to routing loops. An implementation MAY try to resolve the
looping problem by following on the ring strictly tie-broken
shortest-paths only only, but the details are outside this specification.
And even then, the problem of proper capacity provisioning of such
links when they become traffic-bearing in case of failures is vexing vexing,
and when used for forwarding purposes, they defeat statistical non-
blocking guarantees that Clos is providing normally.
6.5. Automatic Disaggregation on Link & Node Failures
6.5.1. Positive, Non-transitive Non-Transitive Disaggregation
Under normal circumstances, a node's South TIEs contain just the
adjacencies and a default route. However, if a node detects that its
default IP prefix covers one or more prefixes that are reachable
through it but not through one or more other nodes at the same level,
then it MUST explicitly advertise those prefixes in a South TIE.
Otherwise, some percentage of the northbound traffic for those
prefixes would be sent to nodes without corresponding reachability,
causing it to be dropped. Even when traffic is not being dropped,
the resulting forwarding could 'backhaul' "backhaul" packets through the higher higher-
level spines, clearly an undesirable condition affecting the blocking
probabilities of the fabric.
This specification refers to the process of advertising additional
prefixes southbound as 'positive disaggregation'. "positive disaggregation". Such
disaggregation is non-transitive, i.e., its effects are always
constrained to a single level of the fabric. Naturally, multiple
node or link failures can lead to several independent instances of
positive disaggregation necessary to prevent looping or bow-tying the
fabric.
A node determines the set of prefixes needing disaggregation using
the following steps:
1. A DAG computation in the southern direction is performed first.
The North TIEs are used to find all of the prefixes it can reach
and the set of next-hops next hops in the lower level for each of them.
Such a computation can be easily performed on a Fat Tree by
setting all link costs in the southern direction to 1 and all
northern directions to infinity. We term The set of those prefixes |R, and is
referred to as |R; for each prefix, r, prefix r in |R, its set of next-hops next hops
is defined to be |H(r).
2. The node uses reflected South TIEs to find all nodes at the same
level in the same PoD and the set of southbound adjacencies for
each. The set of nodes at the same level is termed |N |N, and for
each node, n, in |N, its set of southbound adjacencies is defined
to be |A(n).
3. For a given r, if the intersection of |H(r) and |A(n), for any n,
is empty empty, then that prefix r must be explicitly advertised by the
node in a South TIE.
4. Identical An identical set of disaggregated prefixes is flooded on each of
the node's southbound adjacencies. In accordance with the normal
flooding rules for a South TIE, a node at the lower level that
receives this South TIE SHOULD NOT propagate it south-bound southbound or
reflect the disaggregated prefixes back over its adjacencies to
nodes at the level from which it was received.
To summarize the above in simplest terms: if If a node detects that its
default route encompasses prefixes for which one of the other nodes
in its level has no possible next-hops next hops in the level below, it has to
disaggregate it to prevent traffic loss or suboptimal routing through
such nodes. Hence, a node X needs to determine if it can reach a
different set of south neighbors than other nodes at the same level,
which are connected to it via at least one common south neighbor. If
it can, then prefix disaggregation may be required. If it can't,
then no prefix disaggregation is needed. An example of
disaggregation is provided in Appendix B.3.
Finally, a possible algorithm is described here:
1. Create partial_neighbors = (empty), a set of neighbors with
partial connectivity to the node X's level from X's perspective.
Each entry in the set is a south neighbor of X and a list of
nodes of X.level that can't reach that neighbor.
2. A node X determines its set of southbound neighbors
X.south_neighbors.
3. For each South TIE originated from a node Y that X has has, which is
at X.level, if Y.south_neighbors is not the same as
X.south_neighbors but the nodes share at least one southern
neighbor, for each neighbor N in X.south_neighbors but not in
Y.south_neighbors, add (N, (Y)) to partial_neighbors if N isn't
there or add Y to the list for N.
4. If partial_neighbors is empty, then node X does not disaggregate
any prefixes. If node X is advertising disaggregated prefixes in
its South TIE, X SHOULD remove them and re-advertise its South
TIEs.
A node X computes reachability to all nodes below it based upon the
received North TIEs first. This results in a set of routes, each
categorized by (prefix, path_distance, next-hop set). Alternately,
for clarity in the following procedure, these can be organized by a
next-hop set as ((next-hops), {(prefix, path_distance)}). If
partial_neighbors isn't empty, then the procedure in Figure 17
describes how to identify prefixes to disaggregate.
disaggregated_prefixes = { empty }
nodes_same_level = { empty }
for each South TIE
if (South TIE.level == X.level and
X shares at least one S-neighbor with X)
add South TIE.originator to nodes_same_level
end if
end for
for each next-hop-set NHS
isolated_nodes = nodes_same_level
for each NH in NHS
if NH in partial_neighbors
isolated_nodes =
intersection(isolated_nodes,
partial_neighbors[NH].nodes)
end if
end for
if isolated_nodes is not empty
for each prefix using NHS
add (prefix, distance) to disaggregated_prefixes
end for
end if
end for
copy disaggregated_prefixes to X's South TIE
if X's South TIE is different
schedule South TIE for flooding
end if
Figure 17: Computation of Disaggregated Prefixes
Each disaggregated prefix is sent with the corresponding
path_distance. This allows a node to send the same South TIE to each
south neighbor. The south neighbor which that is connected to that prefix
will thus have a shorter path.
Finally, to summarize the less obvious points partially omitted in
the algorithms to keep them more tractable:
1. all All neighbor relationships MUST perform backlink checks.
2. The overload flag as introduced in Section 6.8.2 and carried in
the _overload_ schema element have has to be respected during the
computation. Nodes advertising themselves as overloaded MUST NOT
be transited in reachability computation but MUST be used as
terminal nodes with prefixes they advertise being reachable.
3. all All the lower-level nodes are flooded to the same disaggregated
prefixes since RIFT does not build a South TIE per node node, which
would complicate things unnecessarily. The lower-level node that
can compute a southbound route to the prefix will prefer it to
the disaggregated route anyway based on route preference rules.
4. positively Positively disaggregated prefixes do *not* have to propagate to
lower levels. With that that, the disturbance in terms of new
flooding is contained to a single level experiencing failures.
5. disaggregated Disaggregated Prefix South TIEs are not "reflected" by the lower
level. Nodes within the same level do *not* need to be aware of
which node computed the need for disaggregation.
6. The fabric is still supporting maximum load balancing properties
while not trying to send traffic northbound unless necessary.
In case positive disaggregation is triggered and due to the very
stable but un-synchronized unsynchronized nature of the algorithm algorithm, the nodes may
issue the necessary disaggregated prefixes at different points in
time. This can lead for For a short time time, this can lead to an "incast" behavior where
the first advertising router based on the nature of the longest
prefix match will attract all the traffic. Different implementation
strategies can be used to lessen that effect, but those are outside
the scope of this specification.
It is worth observing that, in a single plane ToF, this
disaggregation prevents traffic loss up to (K_LEAF * P) link failures
in terms of Section 5.2 or, in other terms, it takes at minimum that
many link failures to partition the ToF into multiple planes.
6.5.2. Negative, Transitive Disaggregation for Fallen Leaves
As explained in Section 5.3 5.3, failures in multi-plane ToF or more than
(K_LEAF * P) links failing in single plane design can generate fallen
leaves. Such scenario cannot be addressed by positive disaggregation
only and needs a further mechanism.
6.5.2.1. Cabling of Multiple ToF Planes
Returning in this section to designs with multiple planes as shown
originally in Figure 3, Figure 18 highlights how the ToF is cabled in
case of two planes by the means of dual-rings to distribute all the
North TIEs within both planes.
____________________________________________________________________________
| [Plane A] . [Plane B] . [Plane C] . [Plane D] |
|..........................................................................|
| +-------------------------------------------------------------+ |
| | +---+ . +---+ . +---+ . +---+ | |
| +-+ n +-------------+ n +-------------+ n +-------------+ n +-+ |
| +--++ . +-+++ . +-+++ . +--++ |
| || . || . || . || |
| +---------||---------------||----------------||---------------+ || |
| | +---+ || . +---+ || . +---+ || . +---+ | || |
| +-+ 1 +---||--------+ 1 +--||---------+ 1 +--||---------+ 1 +-+ || |
| +--++ || . +-+++ || . +-+++ || . +-+++ || |
| || || . || || . || || . || || |
| || || . || || . || || . || || |
Figure 18: Topologically Connected Planes
Section 5.3 already describes how failures in multi-plane fabrics can
lead to traffic loss that normal positive disaggregation cannot fix.
The mechanism of negative, transitive disaggregation incorporated in
RIFT provides the corresponding solution solution, and the next section
explains the involved mechanisms in more detail.
6.5.2.2. Transitive Advertisement of Negative Disaggregates
A ToF node discovering that it cannot reach a fallen leaf SHOULD
disaggregate all the prefixes of that leaf. It uses for For that purpose purpose, it
uses negative prefix South TIEs that are, as usual, flooded
southwards with the scope defined in Section 6.3.4.
Transitively, a node explicitly loses connectivity to a prefix when
none of its children advertises it and when the prefix is negatively
disaggregated by all of its parents. When that happens, the node
originates the negative prefix further down south. Since the
mechanism applies recursively south south, the negative prefix may
propagate transitively all the way down to the leaf. This is
necessary since leaves connected to multiple planes by means of
disjointed paths may have to choose the correct plane at the very
bottom of the fabric to make sure that they don't send traffic
towards another leaf using a plane where it is "fallen" "fallen", which would
make traffic loss unavoidable.
When connectivity is restored, a node that disaggregated a prefix
withdraws the negative disaggregation by the usual mechanism of re-
advertising TIEs omitting the negative prefix.
6.5.2.3. Computation of Negative Disaggregates
Negative prefixes can in fact be advertised due to two different
triggers. This will be described consecutively.
The first origination reason is a computation that uses all the node
North TIEs to build the set of all reachable nodes by reachability
computation over the complete graph and graph, including horizontal ToF links.
The computation uses the node itself as the root. This is compared
with the result of the normal southbound SPF as described in
Section 6.4.2. The difference differences are the fallen leaves and all their
attached prefixes are advertised as negative prefixes southbound if
the node does not consider the prefix to be reachable within the
southbound SPF.
The second origination reason hinges on the understanding of how the
negative prefixes are used within the computation as described in
Figure 19. When attaching the negative prefixes at a certain point
in time time, the negative prefix may find itself with all the viable
nodes from the shorter match nexthop next hop being pruned. In other words,
all its northbound neighbors provided a negative prefix
advertisement. This is the trigger to advertise this negative prefix
transitively south and is normally caused by the node being in a
plane where the prefix belongs to a fabric leaf that has "fallen" in
this plane. Obviously, when one of the northbound switches withdraws
its negative advertisement, the node has to withdraw its transitively
provided negative prefix as well.
6.6. Attaching Prefixes
After an SPF is run, it is necessary to attach the resulting
reachability information in the form of prefixes. For S-SPF,
prefixes from a North TIE are attached to the originating node with
that node's next-hop set and a distance equal to the prefix's cost
plus the node's minimized path distance. The RIFT route database, a
set of (prefix, prefix-type, attributes, path_distance, next-hop
set), accumulates these results.
N-SPF prefixes from each South TIE need to also be added to the RIFT
route database. The N-SPF is really just a stub so the computing
node needs simply needs to determine, for each prefix in a South TIE that
originated from adjacent node, what next-hops next hops to use to reach that
node. Since there may be parallel links, the next-hops next hops to use can be
a set; the presence of the computing node in the associated Node
South TIE is sufficient to verify that at least one link has
bidirectional connectivity. The set of minimum cost next-hops next hops from
the computing node X to the originating adjacent node is determined.
Each prefix has its cost adjusted before being added into the RIFT
route database. The cost of the prefix is set to the cost received
plus the cost of the minimum distance next-hop next hop to that neighbor while
considering its attributes such as mobility per Section 6.8.4. Then
each prefix can be added into the RIFT route database with the next-
hop set; ties are broken based upon type first and then distance and
further on _PrefixAttributes_. Only the best combination is used for
forwarding. RIFT route preferences are normalized by the enum
_RouteType_ in the Thrift [thrift] model given in Section 7.
An example implementation for node X follows:
for each South TIE
if South TIE.level > X.level
next_hop_set = set of minimum cost links to the
South TIE.originator
next_hop_cost = minimum cost link to
South TIE.originator
end if
for each prefix P in the South TIE
P.cost = P.cost + next_hop_cost
if P not in route_database:
add (P, P.cost, P.type,
P.attributes, next_hop_set) to route_database
end if
if (P in route_database):
if route_database[P].cost > P.cost or
route_database[P].type > P.type:
update route_database[P] with (P, P.type, P.cost,
P.attributes,
next_hop_set)
else if route_database[P].cost == P.cost and
route_database[P].type == P.type:
update route_database[P] with (P, P.type,
P.cost, P.attributes,
merge(next_hop_set, route_database[P].next_hop_set))
else
// Not preferred route so ignore
end if
end if
end for
end for
Figure 19: Adding Routes from South TIE Positive and Negative
Prefixes
After the positive prefixes are attached and tie-broken, negative
prefixes are attached and used in case of northbound computation,
ideally from the shortest length to the longest. The nexthop next-hop
adjacencies for a negative prefix are inherited from the longest
positive prefix that aggregates it, and subsequently adjacencies to
nodes that advertised negative for this prefix are removed.
The rule of inheritance MUST be maintained when the nexthop next-hop list for
a prefix is modified, as the modification may affect the entries for
matching negative prefixes of immediate longer prefix length. For
instance, if a nexthop next hop is added, then by inheritance inheritance, it must be
added to all the negative routes of immediate longer prefixes length
unless it is pruned due to a negative advertisement for the same next
hop. Similarly, if a nexthop next hop is deleted for a given prefix, then it
is deleted for all the immediately aggregated negative routes. This
will recurse in the case of nested negative prefix aggregations.
The rule of inheritance MUST also be maintained when a new prefix of
intermediate length is inserted, inserted or when the immediately aggregating
prefix is deleted from the routing table, making an even shorter
aggregating prefix the one from which the negative routes now inherit
their adjacencies. As the aggregating prefix changes, all the
negative routes MUST be recomputed, and then again again, the process may
recurse in case of nested negative prefix aggregations.
Although these operations can be computationally expensive, the
overall load on devices in the network is low because these
computations are not run very often, as positive route advertisements
are always preferred over negative ones. This prevents recursion in
most cases because positive reachability information never inherits
next hops.
To make the negative disaggregation less abstract and provide an
example ToP node node, T1 with 4 ToF parents S1..S4 as represented in
Figure 20 are considered further:
+----+ +----+ +----+ +----+ N
| S1 | | S2 | | S3 | | S4 | ^
+----+ +----+ +----+ +----+ W< + >E
| | | | v
|+--------+ | | S
||+-----------------+ |
|||+----------------+---------+
||||
+----+
| T1 |
+----+
Figure 20: A ToP Node with 4 Parents
If all ToF nodes can reach all the prefixes in the network; network, with
RIFT, they will normally advertise a default route south. An
abstract Routing Information Base (RIB), more commonly known as a
routing table, stores all types of maintained routes routes, including the
negative ones and "tie-breaks" for the best one, whereas an abstract
Forwarding
forwarding table (FIB) retains only the ultimately computed
"positive" routing instructions. In T1, those tables would look as
illustrated in Figure 21:
+---------+
| Default |
+---------+
|
| +--------+
+---> | Via S1 |
| +--------+
|
| +--------+
+---> | Via S2 |
| +--------+
|
| +--------+
+---> | Via S3 |
| +--------+
|
| +--------+
+---> | Via S4 |
+--------+
Figure 21: Abstract RIB
In case T1 receives a negative advertisement for prefix 2001:db8::/32
from S1 S1, a negative route is stored in the RIB (indicated by a ~ "~"
sign), while the more specific routes to the complementing ToF nodes
are installed in FIB. RIB and FIB in T1 now look as illustrated in
Figure
Figures 22 and Figure 23, respectively:
+---------+ +-----------------+
| Default | <-------------- | ~2001:db8::/32 |
+---------+ +-----------------+
| |
| +--------+ | +--------+
+---> | Via S1 | +---> | Via S1 |
| +--------+ +--------+
|
| +--------+
+---> | Via S2 |
| +--------+
|
| +--------+
+---> | Via S3 |
| +--------+
|
| +--------+
+---> | Via S4 |
+--------+
Figure 22: Abstract RIB after After Negative 2001:db8::/32 from S1
The negative 2001:db8::/32 prefix entry inherits from ::/0, so the
positive
positive, more specific routes are the complements to S1 in the set
of
next-hops next hops for the default route. That entry is composed of S2,
S3, and S4, or, or in other words, it uses all entries in the default
route with a "hole punched" for S1 into them. These are the next
hops that are still available to reach 2001:db8::/32, 2001:db8::/32 now that S1
advertised that it will not forward 2001:db8::/32 anymore.
Ultimately, those resulting next-hops next hops are installed in FIB for the
more specific route to 2001:db8::/32 as illustrated below:
+---------+ +---------------+
| Default | | 2001:db8::/32 |
+---------+ +---------------+
| |
| +--------+ |
+---> | Via S1 | |
| +--------+ |
| |
| +--------+ | +--------+
+---> | Via S2 | +---> | Via S2 |
| +--------+ | +--------+
| |
| +--------+ | +--------+
+---> | Via S3 | +---> | Via S3 |
| +--------+ | +--------+
| |
| +--------+ | +--------+
+---> | Via S4 | +---> | Via S4 |
+--------+ +--------+
Figure 23: Abstract FIB after After Negative 2001:db8::/32 from S1
To illustrate matters further further, consider T1 receiving a negative
advertisement for prefix 2001:db8:1::/48 from S2, which is stored in
RIB again. After the update, the RIB in T1 is illustrated in
Figure 24:
+---------+ +----------------+ +------------------+
| Default | <----- | ~2001:db8::/32 | <------ | ~2001:db8:1::/48 |
+---------+ +----------------+ +------------------+
| | |
| +--------+ | +--------+ |
+---> | Via S1 | +---> | Via S1 | |
| +--------+ +--------+ |
| |
| +--------+ | +--------+
+---> | Via S2 | +---> | Via S2 |
| +--------+ +--------+
|
| +--------+
+---> | Via S3 |
| +--------+
|
| +--------+
+---> | Via S4 |
+--------+
Figure 24: Abstract RIB after After Negative 2001:db8:1::/48 from S2
Negative 2001:db8:1::/48 inherits from 2001:db8::/32 now, so the
positive
positive, more specific routes are the complements to S2 in the set
of next hops for 2001:db8::/32, which are S3 and S4, or, or in other
words, all entries of the parent with the negative holes "punched in"
again. After the update, the FIB in T1 shows as illustrated in
Figure 25:
+---------+ +---------------+ +-----------------+
| Default | | 2001:db8::/32 | | 2001:db8:1::/48 |
+---------+ +---------------+ +-----------------+
| | |
| +--------+ | |
+---> | Via S1 | | |
| +--------+ | |
| | |
| +--------+ | +--------+ |
+---> | Via S2 | +---> | Via S2 | |
| +--------+ | +--------+ |
| | |
| +--------+ | +--------+ | +--------+
+---> | Via S3 | +---> | Via S3 | +---> | Via S3 |
| +--------+ | +--------+ | +--------+
| | |
| +--------+ | +--------+ | +--------+
+---> | Via S4 | +---> | Via S4 | +---> | Via S4 |
+--------+ +--------+ +--------+
Figure 25: Abstract FIB after After Negative 2001:db8:1::/48 from S2
Further, assume that S3 stops advertising its service as a default
gateway. The entry is removed from RIB as usual. In order to update
the FIB, it is necessary to eliminate the FIB entry for the default
route, as well as all the FIB entries that were created for negative
routes pointing to the RIB entry being removed (::/0). This is done
recursively for 2001:db8::/32 and then for, for 2001:db8:1::/48. The
related FIB entries via S3 are removed, removed as illustrated in Figure 26.
+---------+ +---------------+ +-----------------+
| Default | | 2001:db8::/32 | | 2001:db8:1::/48 |
+---------+ +---------------+ +-----------------+
| | |
| +--------+ | |
+---> | Via S1 | | |
| +--------+ | |
| | |
| +--------+ | +--------+ |
+---> | Via S2 | +---> | Via S2 | |
| +--------+ | +--------+ |
| | |
| | |
| | |
| | |
| | |
| +--------+ | +--------+ | +--------+
+---> | Via S4 | +---> | Via S4 | +---> | Via S4 |
+--------+ +--------+ +--------+
Figure 26: Abstract FIB after After Loss of S3
Say that at that time, S4 would also disaggregate prefix
2001:db8:1::/48. This would mean that the FIB entry for
2001:db8:1::/48 becomes a discard route, and that would be the signal
for T1 to disaggregate prefix 2001:db8:1::/48 negatively in a
transitive fashion with its own children.
Finally, the case occurs where S3 becomes available again as a
default gateway, and a negative advertisement is received from S4
about prefix 2001:db8:2::/48 as opposed to 2001:db8:1::/48. Again, a
negative route is stored in the RIB, and the more specific route to
the complementing ToF nodes are is installed in FIB. Since
2001:db8:2::/48 inherits from 2001:db8::/32, the positive FIB routes
are chosen by removing S4 from S2, S3, S4. The abstract FIB in T1
now shows as illustrated in Figure 27:
+-----------------+
| 2001:db8:2::/48 |
+-----------------+
|
+---------+ +---------------+ +-----------------+
| Default | | 2001:db8::/32 | | 2001:db8:1::/48 |
+---------+ +---------------+ +-----------------+
| | | |
| +--------+ | | | +--------+
+---> | Via S1 | | | +---> | Via S2 |
| +--------+ | | | +--------+
| | | |
| +--------+ | +--------+ | | +--------+
+---> | Via S2 | +---> | Via S2 | | +---> | Via S3 |
| +--------+ | +--------+ | +--------+
| | |
| +--------+ | +--------+ | +--------+
+---> | Via S3 | +---> | Via S3 | +---> | Via S3 |
| +--------+ | +--------+ | +--------+
| | |
| +--------+ | +--------+ | +--------+
+---> | Via S4 | +---> | Via S4 | +---> | Via S4 |
+--------+ +--------+ +--------+
Figure 27: Abstract FIB after After Negative 2001:db8:2::/48 from S4
6.7. Optional Zero Touch Provisioning (RIFT ZTP)
Each RIFT node can operate in zero touch provisioning Zero Touch Provisioning (ZTP) mode,
i.e.
i.e., it has no RIFT specific RIFT-specific configuration (unless it is a ToF or it
is explicitly configured to operate in the overall topology as a leaf
and/or support leaf-2-leaf procedures) leaf-to-leaf procedures), and it will fully fully,
automatically derive necessary RIFT parameters itself after being
attached to the topology. Manually configured nodes and nodes
operating using RIFT ZTP can be mixed freely and will form a valid
topology if achievable.
The derivation of the level of each node happens based on offers
received from its neighbors neighbors, whereas each node (with the possible
exception of nodes configured as leaves) tries to attach at the
highest possible point in the fabric. This guarantees that even if
the diffusion front of offers reaches a node from "below" faster than
from "above", it will greedily abandon an already negotiated level
derived from nodes topologically below it and properly peer with
nodes above.
The fabric is very consciously numbered from the top down to allow
for PoDs of different heights and to minimize the number of
configuration
configurations necessary, in this case case, just a TOP_OF_FABRIC flag on
every node at the top of the fabric.
This section describes the necessary concepts and procedures of the
RIFT ZTP operation.
6.7.1. Terminology
The interdependencies between the different flags and the configured
level can be somewhat vexing at first first, and it may take multiple reads
of the glossary to comprehend them.
Automatic Level Derivation:
Procedures which that allow nodes without a level configured to derive
it automatically. Only applied if CONFIGURED_LEVEL is undefined.
UNDEFINED_LEVEL:
A "null" value that indicates that the level has not been
determined and has not been configured. Schemas normally indicate
that by a missing optional value without an available defined
default.
LEAF_ONLY:
An optional configuration flag that can be configured on a node to
make sure it never leaves the "bottom of the hierarchy". The
TOP_OF_FABRIC flag and CONFIGURED_LEVEL cannot be defined at the
same time as this flag. It implies a CONFIGURED_LEVEL value of
_leaf_level_. It is indicated in the _leaf_only_ schema element.
TOP_OF_FABRIC:
A configuration flag that MUST be provided on all ToF nodes.
LEAF_FLAG and CONFIGURED_LEVEL cannot be defined at the same time
as this flag. It implies a CONFIGURED_LEVEL value. In fact, it
is basically a shortcut for configuring the same level at all ToF
nodes
nodes, which is unavoidable since an initial 'seed' "seed" is needed for
other ZTP nodes to derive their level in the topology. The flag
plays an important role in fabrics with multiple planes to enable
successful negative disaggregation (Section 6.5.2). It is carried
in the _top_of_fabric_ schema element. A standards conforming standards-conforming
RIFT implementation implies a CONFIGURED_LEVEL value of
_top_of_fabric_level_ in case of TOP_OF_FABRIC. This value is
kept reasonably low to allow for fast ZTP re-convergence reconvergence on
failures.
CONFIGURED_LEVEL:
A level value provided manually. When this is defined (i.e. (i.e., it
is not an UNDEFINED_LEVEL) UNDEFINED_LEVEL), the node is not participating in ZTP
in the sense of deriving its own level based on other nodes'
information. The TOP_OF_FABRIC flag is ignored when this value is
defined. LEAF_ONLY can be set only if this value is undefined or
set to _leaf_level_.
DERIVED_LEVEL:
Level value computed via automatic level derivation when
CONFIGURED_LEVEL is equal to UNDEFINED_LEVEL.
LEAF_2_LEAF:
An optional flag that can be configured on a node to make sure it
supports procedures defined in Section 6.8.9. It is a capability
that implies LEAF_ONLY and the corresponding restrictions. The
TOP_OF_FABRIC flag is ignored when set at the same time as this
flag. It is carried in the _leaf_only_and_leaf_2_leaf_procedures_
schema flag.
LEVEL_VALUE:
With ZTP, the original definition of "level" in Section 3.1 is
both extended and relaxed. First, the level is defined now as
LEVEL_VALUE and is the first defined value of CONFIGURED_LEVEL
followed by DERIVED_LEVEL. Second, it is possible for nodes to be
more than one level apart to form adjacencies if any of the nodes
is at least LEAF_ONLY.
Valid Offered Level (VOL):
A neighbor's level received in a valid LIE (i.e. (i.e., passing all
checks for adjacency formation while disregarding all clauses
involving level values) persisting for the duration of the
holdtime interval on the LIE. Observe that offers from nodes
offering the level value of _leaf_level_ do not constitute VOLs
(since no valid DERIVED_LEVEL can be obtained from those and
consequently the _not_a_ztp_offer_ flag MUST be ignored). Offers
from LIEs with _not_a_ztp_offer_ being true are not VOLs either.
If a node maintains parallel adjacencies to the neighbor, VOL on
each adjacency is considered as equivalent, i.e. i.e., the newest VOL
from any such adjacency updates the VOL received from the same
node.
Highest Available Level (HAL):
Highest defined
Highest-defined level value received from all VOLs received.
Highest Available Level Systems (HALS):
Set of nodes offering HAL VOLs.
Highest Adjacency ThreeWay (HAT):
Highest neighbor level of all the formed _ThreeWay_ adjacencies
for the node.
6.7.2. Automatic System ID Selection
RIFT nodes require a 64-bit System ID which that SHOULD be derived as
EUI-64 MA-L derive MAC Address Block Large (MA-L) according to [EUI64]. The
organizationally governed portion of this ID (24 bits) can be used to
generate multiple IDs if required to indicate more than one RIFT
instance.
As matter of operational concern, the router MUST ensure that such
identifier is not changing very frequently (or at least not without
sending all its TIEs with fairly short lifetimes, i.e. i.e., purging them)
since otherwise the network may otherwise be left with large amounts of stale
TIEs in other nodes (though this is not necessarily a serious problem
if the procedures described in Section 9 are implemented).
6.7.3. Generic Fabric Example
ZTP forces considerations of an incorrectly or unusually cabled
fabric and how such a topology can be forced into a "lattice"
structure which that a fabric represents (with further restrictions). A
necessary and sufficient physical cabling is shown in Figure 28. The
assumption here is that all nodes are in the same PoD.
+---+
| A | s = TOP_OF_FABRIC
| s | L = LEAF_ONLY
++-++ L2L = LEAF_2_LEAF
| |
+--+ +--+
| |
+--++ ++--+
| E | | F |
| +-+ | +-----------+
++--+ | ++-++ |
| | | | |
| +-------+ | |
| | | | |
| | +----+ | |
| | | | |
++-++ ++-++ |
| I +-----+ J | |
| | | +-+ |
++-++ +--++ | |
| | | | |
+---------+ | +------+ |
| | | | |
+-----------------+ | |
| | | | |
++-++ ++-++ |
| X +-----+ Y +-+
|L2L| | L |
+---+ +---+
Figure 28: Generic ZTP Cabling Considerations
First, RIFT must anchor the "top" of the cabling and that's what the
TOP_OF_FABRIC flag at node A is for. Then Then, things look smooth until
the protocol has to decide whether node Y is at the same level as I,
J (and as consequence, X is south of it) it), or at the same level as X. This is unresolvable
here until we "nail down the bottom" of the topology. To achieve that
that, the protocol chooses to use in this
example the leaf flags in X and Y. Y in this
example. In the case where Y would does not have a leaf flag flag, it will try
to elect the highest level offered and end up being in same level as
I and J.
6.7.4. Level Determination Procedure
A node starting up with UNDEFINED_VALUE (i.e. (i.e., without a
CONFIGURED_LEVEL or any leaf or TOP_OF_FABRIC flag) MUST follow those these
additional procedures:
1. It advertises its LEVEL_VALUE on all LIEs (observe that this can
be UNDEFINED_LEVEL UNDEFINED_LEVEL, which in terms of the schema schema, is simply an
omitted optional value).
2. It computes HAL as the numerically highest available level in all
VOLs.
3. It Then, it chooses then MAX(HAL-1,0) as its DERIVED_LEVEL. The node
then starts to advertise this derived level.
4. A node that lost all adjacencies with the HAL value MUST hold
down computation of the new DERIVED_LEVEL for at least one second
unless it has no VOLs from southbound adjacencies. After the
holddown timer expired, it MUST discard all received offers,
recompute
DERIVED_LEVEL DERIVED_LEVEL, and announce it to all neighbors.
5. A node MUST reset any adjacency that has changed the level it is
offering and is in _ThreeWay_ state.
6. A node that changed its defined level value MUST readvertise re-advertise its
own TIEs (since the new _PacketHeader_ will contain a different
level than before). The sequence number of each TIE MUST be
increased.
7. After a level has been derived derived, the node MUST set the
_not_a_ztp_offer_ on LIEs towards all systems offering a VOL for
HAL.
8. A node that changed its level SHOULD flush from its link state
database TIEs of all other nodes, otherwise
nodes from its link state database; otherwise, stale information
may persist on "direction reversal", i.e., nodes that seemed
south are now north or east-west. This will not prevent the
correct operation of the protocol but could be slightly confusing
operationally.
A node starting with LEVEL_VALUE being 0 (i.e., it assumes a leaf
function by being configured with the appropriate flags or has a
CONFIGURED_LEVEL of 0) MUST follow those this additional procedures: procedure:
1. It computes HAT per the procedures above but does *not* use it to
compute DERIVED_LEVEL. HAT is used to limit adjacency formation
per Section 6.2.
It MAY also follow this modified procedures: procedure:
1. It may pick a different strategy to choose VOL, e.g. e.g., use the VOL
value with highest number of VOLs. Such strategies are only
possible since the node always remains "at the bottom of the
fabric"
fabric", while another layer could "invert" the fabric by picking
its preferred VOL in a different fashion rather than always
trying to achieve the highest viable level.
6.7.5. RIFT ZTP FSM
This section specifies the precise, normative ZTP FSM and can be
omitted unless the reader is pursuing an implementation of the
protocol. For additional clarity clarity, a graphical representation of the
ZTP FSM is depicted in Figure 29. It may also be helpful to refer to
the normative schema in Section 7.
Initial
The initial state is ComputeBestOffer.
Enter
|
v
+------------------+
| ComputeBestOffer |
| |<----+
| | | BetterHAL
| | | BetterHAT
| | | ChangeLocalConfiguredLevel
| | | ChangeLocalHierarchyIndications
| | | LostHAT
| | | NeighborOffer
| | | ShortTic
| |-----+
| |
| |<---------------------
| |---------------------> (UpdatingClients)
| | ComputationDone
+------------------+
^ |
| | LostHAL
| V
(HoldingDown)
(ComputeBestOffer)
| ^
| | ChangeLocalConfiguredLevel
| | ChangeLocalHierarchyIndications
| | HoldDownExpired
V |
+------------------+
| HoldingDown |
| |<----+
| | | BetterHAL
| | | BetterHAT
| | | ComputationDone
| | | LostHAL
| | | LostHat
| | | NeighborOffer
| | | ShortTic
| |-----+
+------------------+
^
|
(UpdatingClients)
(ComputeBestOffer)
| ^
| | BetterHAL
| | BetterHAT
| | LostHAT
| | ChangeLocalHierarchyIndications
| | ChangeLocalConfiguredLevel
V |
+------------------+
| UpdatingClients |
| |<----+
| | |
| | | NeighborOffer
| | | ShortTic
| |-----+
+------------------+
|
| LostHAL
V
(HoldingDown)
Figure 29: RIFT ZTP FSM
The following words terms are used for well-known procedures:
* PUSH Event: queues an event to be executed by the FSM upon exit of
this action
* COMPARE_OFFERS: checks whether whether, based on current offers and held
last results, the events BetterHAL/LostHAL/BetterHAT/LostHAT are
necessary and returns them
* UPDATE_OFFER: store current offer with adjacency holdtime as
lifetime and COMPARE_OFFERS, then PUSH corresponding events
* LEVEL_COMPUTE: compute best offered or configured level and HAL/
HAT, if anything changed changed, PUSH ComputationDone
* REMOVE_OFFER: remove the corresponding offer and COMPARE_OFFERS,
PUSH corresponding events
* PURGE_OFFERS: REMOVE_OFFER for all held offers, COMPARE OFFERS,
PUSH corresponding events
* PROCESS_OFFER:
1. if no level offered is offered, then REMOVE_OFFER
2. else
1.
a. if offered level > leaf leaf, then UPDATE_OFFER
2.
b. else REMOVE_OFFER
States:
* ComputeBestOffer: processes Processes received offers to derive ZTP
variables
variables.
* HoldingDown: holding Holding down while receiving updates updates.
* UpdatingClients: updates Updates other FSMs on the same node with
computation results results.
Events:
* ChangeLocalHierarchyIndications: node Node locally configured with new
leaf flags.
* ChangeLocalConfiguredLevel: node Node locally configured with a defined
level
level.
* NeighborOffer: a A new neighbor offer with optional level and
neighbor state.
* BetterHAL: better Better HAL computed internally.
* BetterHAT: better Better HAT computed internally.
* LostHAL: lost Lost last HAL in computation.
* LostHAT: lost Lost HAT in computation.
* ComputationDone: computation Computation performed.
* HoldDownExpired: holddown Holddown timer expired.
* ShortTic: one-second One-second timer tick. This event is provided to the
FSM once a second by an implementation-specific mechanism that is
outside the scope of this specification. This event is quietly
ignored if the relevant transition does not exist.
Actions:
* on ChangeLocalConfiguredLevel in HoldingDown finishes in
ComputeBestOffer: store configured level
* on BetterHAT in HoldingDown finishes in HoldingDown: no action
* on ShortTic in HoldingDown finishes in HoldingDown: remove expired
offers
offers, and if holddown timer expired expired, PUSH_EVENT HoldDownExpired
* on NeighborOffer in HoldingDown finishes in HoldingDown:
PROCESS_OFFER
* on ComputationDone in HoldingDown finishes in HoldingDown: no
action
* on BetterHAL in HoldingDown finishes in HoldingDown: no action
* on LostHAT in HoldingDown finishes in HoldingDown: no action
* on LostHAL in HoldingDown finishes in HoldingDown: no action
* on HoldDownExpired in HoldingDown finishes in ComputeBestOffer:
PURGE_OFFERS
* on ChangeLocalHierarchyIndications in HoldingDown finishes in
ComputeBestOffer: store leaf flags
* on LostHAT in ComputeBestOffer finishes in ComputeBestOffer:
LEVEL_COMPUTE
* on NeighborOffer in ComputeBestOffer finishes in ComputeBestOffer:
PROCESS_OFFER
* on BetterHAT in ComputeBestOffer finishes in ComputeBestOffer:
LEVEL_COMPUTE
* on ChangeLocalHierarchyIndications in ComputeBestOffer finishes in
ComputeBestOffer: store leaf flags and LEVEL_COMPUTE
* on LostHAL in ComputeBestOffer finishes in HoldingDown: if any
southbound adjacencies present present, then update holddown timer to
normal duration duration, else fire holddown timer immediately
* on ShortTic in ComputeBestOffer finishes in ComputeBestOffer:
remove expired offers
* on ComputationDone in ComputeBestOffer finishes in
UpdatingClients: no action
* on ChangeLocalConfiguredLevel in ComputeBestOffer finishes in
ComputeBestOffer: store configured level and LEVEL_COMPUTE
* on BetterHAL in ComputeBestOffer finishes in ComputeBestOffer:
LEVEL_COMPUTE
* on ShortTic in UpdatingClients finishes in UpdatingClients: remove
expired offers
* on LostHAL in UpdatingClients finishes in HoldingDown: if any
southbound adjacencies are present present, then update holddown timer to
normal duration duration, else fire holddown timer immediately
* on BetterHAT in UpdatingClients finishes in ComputeBestOffer: no
action
* on BetterHAL in UpdatingClients finishes in ComputeBestOffer: no
action
* on ChangeLocalConfiguredLevel in UpdatingClients finishes in
ComputeBestOffer: store configured level
* on ChangeLocalHierarchyIndications in UpdatingClients finishes in
ComputeBestOffer: store leaf flags
* on NeighborOffer in UpdatingClients finishes in UpdatingClients:
PROCESS_OFFER
* on LostHAT in UpdatingClients finishes in ComputeBestOffer: no
action
* on Entry into ComputeBestOffer: LEVEL_COMPUTE
* on Entry into UpdatingClients: update all LIE FSMs with
computation results
6.7.6. Resulting Topologies
The procedures defined in Section 6.7.4 will lead to the RIFT
topology and levels depicted in Figure 30.
+---+
| A |
| 24|
++-++
| |
+--+ +--+
| |
+--++ ++--+
| E | | F |
| 23+-+ | 23+-----------+
++--+ | ++-++ |
| | | | |
| +-------+ | |
| | | | |
| | +----+ | |
| | | | |
++-++ ++-++ |
| I +-----+ J | |
| 22| | 22| |
++--+ +--++ |
| | |
+---------+ | |
| | |
++-++ +---+ |
| X | | Y +-+
| 0 | | 0 |
+---+ +---+
Figure 30: Generic ZTP Topology Autoconfigured
In the case where the LEAF_ONLY restriction on Y is removed removed, the
outcome would be very different however and result in Figure 31.
This
demonstrates basically demonstrates that auto configuration autoconfiguration makes miscabling
detection hard and and, with that that, can lead to undesirable effects in
cases where leaves are not "nailed" by the appropriately configured
flags and arbitrarily cabled.
+---+
| A |
| 24|
++-++
| |
+--+ +--+
| |
+--++ ++--+
| E | | F |
| 23+-+ | 23+-------+
++--+ | ++-++ |
| | | | |
| +-------+ | |
| | | | |
| | +----+ | |
| | | | |
++-++ ++-++ +-+-+
| I +-----+ J +-----+ Y |
| 22| | 22| | 22|
++-++ +--++ ++-++
| | | | |
| +-----------------+ |
| | |
+---------+ | |
| | |
++-++ |
| X +--------+
| 0 |
+---+
Figure 31: Generic ZTP Topology Autoconfigured
6.8. Further Mechanisms
6.8.1. Route Preferences
Since RIFT distinguishes between different route types types, such as e.g.
external routes from other protocols protocols, and additionally advertises
special types of routes on disaggregation, the protocol MUST tie-
break internally different types on a clear preference scale to
prevent traffic loss or loops. The preferences are given in the
schema type _RouteType_.
Table 5 contains the route type as derived from the TIE type carrying
it. Entries are sorted from the most preferred route type to the
least preferred route type.
+==================================+======================+
| TIE Type | Resulting Route Type |
+==================================+======================+
| None | Discard |
+----------------------------------+----------------------+
| Local Interface | LocalPrefix |
+----------------------------------+----------------------+
| S-PGP | South PGP |
+----------------------------------+----------------------+
| N-PGP | North PGP |
+----------------------------------+----------------------+
| North Prefix | NorthPrefix |
+----------------------------------+----------------------+
| North External Prefix | NorthExternalPrefix |
+----------------------------------+----------------------+
| South Prefix and South Positive | SouthPrefix |
| Disaggregation | |
+----------------------------------+----------------------+
| South External Prefix and South | SouthExternalPrefix |
| Positive External Disaggregation | |
+----------------------------------+----------------------+
| South Negative Prefix | NegativeSouthPrefix |
+----------------------------------+----------------------+
Table 5: TIEs and Contained Route Types
6.8.2. Overload Bit
Overload
The overload attribute is specified in the packet encoding schema
(Section 7) in the _overload_ flag.
The overload flag MUST be respected by all necessary SPF
computations. A node with the overload flag set SHOULD advertise all
locally hosted prefixes prefixes, both northbound and southbound, southbound; all other
southbound prefixes SHOULD NOT be advertised.
Leaf nodes SHOULD set the overload attribute on all originated Node
TIEs. If spine nodes were to forward traffic not intended for the
local node, the leaf node would not be able to prevent routing/
forwarding loops as it does not have the necessary topology
information to do so.
6.8.3. Optimized Route Computation on Leaves
Leaf nodes only have visibility to directly connected nodes and
therefore are not required to run "full" SPF computations. Instead,
prefixes from neighboring nodes can be gathered to run a "partial"
SPF computation in order to build the routing table.
Leaf nodes SHOULD only hold their own N-TIEs, and N-TIEs and, in cases of L2L
implementations, the N-TIEs of their East/West East-West neighbors. Leaf nodes
MUST hold all S-TIEs from their neighbors.
Normally, a full network graph is created based on local N-TIEs and
remote S-TIEs that it receives from neighbors, at which time,
necessary SPF computations are performed. Instead, leaf nodes can
simply compute the minimum cost and next-hop set of each leaf
neighbor by examining its local adjacencies. Associated N-TIEs are
used to determine bi-directionality bidirectionality and derive the next-hop set.
Cost The
cost is then derived from the minimum cost of the local adjacency to
the neighbor and the prefix cost.
Leaf nodes would then attach necessary prefixes as described in
Section 6.6.
6.8.4. Mobility
The RIFT control plane MUST maintain the real time status of every
prefix, to which port it is attached, and to which leaf node that
port belongs. This is still true in cases of IP mobility where the
point of attachment may change several times a second.
There are two classic approaches to explicitly maintain this
information, "timestamp" and "sequence counter" counter", which are defined as
follows:
timestamp:
With this method, the infrastructure SHOULD record the precise
time at which the movement is observed. One key advantage of this
technique is that it has no dependency on the mobile device. One
drawback is that the infrastructure MUST be precisely synchronized
in order to be able to compare timestamps as the points of
attachment change. This could be accomplished by utilizing the
Precision Time Protocol (PTP) IEEE (IEEE Std. 1588 [IEEEstd1588] or
802.1AS [IEEEstd8021AS] [IEEEstd8021AS]), which is designed for bridged LANs.
Both the precision of the synchronization protocol and the
resolution of the timestamp must beat the shortest possible
roaming time on the fabric. Another drawback is that the presence
of a mobile device may only be observed asynchronously, such as
when it starts using an IP protocol like ARP [RFC0826], IPv6
Neighbor Discovery [RFC4861], IPv6 Stateless Address Configuration
[RFC4862], DHCP [RFC2131], or DHCPv6 [RFC8415].
sequence counter:
With this method, a mobile device notifies its point of attachment
on arrival with a sequence counter that is incremented upon each
movement. On the positive side, this method does not have a
dependency on a precise sense of time, since the sequence of
movements is kept in order by the mobile device. The disadvantage
of this approach is the need for support for protocols that may be
used by the mobile device to register its presence to the leaf
node with the capability to provide a sequence counter. Well-
known issues with sequence counters counters, such as wrapping and
comparison rules rules, MUST be addressed properly. Sequence numbers
MUST be compared by a single homogenous source to make operation
feasible. Sequence number comparison from multiple heterogeneous
sources would be extremely difficult to implement.
RIFT supports a hybrid approach by using an optional
'PrefixSequenceType' attribute (that (which is also called a
_monotonic_clock_ in the schema) that consists of a timestamp and
optional sequence number field. In case of a negatively distributed
prefix
prefix, this attribute MUST NOT be included by the originator and it
MUST be ignored by all nodes during computation. When this attribute
is present (observe that per data schema schema, the attribute itself is
optional
optional, but in case it is included included, the 'timestamp' "timestamp" field is
required):
* The leaf node MAY advertise a timestamp of the latest sighting of
a prefix, e.g., by snooping IP protocols or the node using the
time at which it advertised the prefix. RIFT transports the
timestamp within the desired Prefix North TIEs as the
[IEEEstd1588] timestamp.
* RIFT MAY interoperate with "Registration Extensions for 6LoWPAN
Neighbor Discovery" [RFC8505], which provides a method for
registering a prefix with a sequence number called a Transaction
ID (TID). In such cases, RIFT SHOULD transport the derived TID
without modification.
* RIFT also defines an abstract negative clock (ASNC) (also called
an 'undefined' "undefined" clock). The ASNC MUST be considered older than any
other defined clock. By default, when a node receives a Prefix
North TIE that does not contain a 'PrefixSequenceType' attribute,
it MUST interpret the absence as the ASNC.
* Any prefix present on the fabric in multiple nodes that have the
*same* clock is considered as anycast.
* The RIFT specification assumes that all nodes are being
synchronized within at least 200 milliseconds or less. This is
achievable through the use of NTP [RFC5905]. An implementation
MAY provide a way to reconfigure a domain to a different value, value and
provides for
this purpose a variable called MAXIMUM_CLOCK_DELTA. MAXIMUM_CLOCK_DELTA for this purpose.
6.8.4.1. Clock Comparison
All monotonic clock values MUST be compared to each other using the
following rules:
1. The ASNC is older than any other value except ASNC *and* ASNC,
2. Clocks with timestamp timestamps differing by more than MAXIMUM_CLOCK_DELTA
are comparable by using the timestamps only *and* only,
3. Clocks with timestamps differing by less than MAXIMUM_CLOCK_DELTA
are comparable by using their TIDs only only, *and*
4. An undefined TID is always older than any other TID TID, *and*
5. TIDs are compared using rules of [RFC8505].
6.8.4.2. Interaction between Time Stamps Between Timestamps and Sequence Counters
For attachment changes that occur less frequently (e.g., once per
second), the timestamp that the RIFT infrastructure captures should
be enough to determine the most current discovery. If the point of
attachment changes faster than the maximum drift of the time stamping timestamping
mechanism (i.e., MAXIMUM_CLOCK_DELTA), then a sequence number SHOULD
be used to enable necessary precision to determine currency.
The sequence counter in [RFC8505] is encoded as one octet and wraps
around using Appendix A.
Within the resolution of MAXIMUM_CLOCK_DELTA, sequence counter values
captured during 2 sequential iterations of the same timestamp SHOULD
be comparable. This means that with default values, a node may move
up to 127 times in a 200-millisecond period and the clocks will
remain comparable. This allows the RIFT infrastructure to explicitly
assert the most up-to-date advertisement.
6.8.4.3. Anycast vs. Unicast
A unicast prefix can be attached to at most one leaf, leaf at most, whereas an
anycast prefix may be reachable via more than one leaf.
If a monotonic clock attribute is provided on the prefix, then the
prefix with the *newest* clock value is strictly preferred. An
anycast prefix does not carry a clock clock, or all clock attributes MUST
be the same under the rules of Section 6.8.4.1.
It
In mobility events, it is important that in mobility events the leaf is re-flooding reflooding as
quickly as possible to communicate the absence of the prefix that
moved.
Without support for [RFC8505] [RFC8505], movements on the fabric within
intervals smaller than 100msec 100 msec will be interpreted as anycast.
6.8.4.4. Overlays and Signaling
RIFT is agnostic to any overlay technologies and their associated
control and transports that run on top of it (e.g. VXLAN). (e.g., Virtual
eXtensible Local Area Network (VXLAN)). It is expected that leaf
nodes and possibly ToF nodes can perform necessary data plane
encapsulation.
In the context of mobility, overlays provide another possible
solution to avoid injecting mobile prefixes into the fabric as well
as improving scalability of the deployment. It makes sense to
consider overlays for mobility solutions in IP fabrics. As an
example, a mobility protocol such as LISP the Locator/ID Separation
Protocol (LISP) [RFC9300] [RFC9301] may inform the ingress leaf of
the location of the egress leaf in real time.
Another possibility is to consider that mobility as is an underlay
service and support it in RIFT to an extent. The load on the fabric
increases with the amount of mobility obviously since a move forces flooding
and computation on all nodes in the scope of the move so tunneling
from the leaf to the ToF may be desired to speed up convergence
times.
6.8.5. Key/Value (KV) Store
6.8.5.1. Southbound
RIFT supports the southbound distribution of key-value pairs that can
be used to distribute information to facilitate higher levels of
functionality (e.g. (e.g., distribution of configuration information). KV
South TIEs may arrive from multiple nodes and therefore MUST execute
the following tie-breaking rules for each key:
1. Only KV TIEs received from nodes to which a bi-directional bidirectional
adjacency exists MUST be considered.
2. For each valid KV South TIEs that contains the same key, the
value within the South TIE with the highest level will be
preferred. If the levels are identical, the highest originating
System ID will be preferred. In the case of overlapping keys in
the winning South TIE, the behavior is undefined.
Consider that if a node goes down, nodes south of it will lose
associated adjacencies adjacencies, causing them to disregard corresponding KVs.
New KV South TIEs are advertised to prevent stale information being
used by nodes that are further south. KV advertisements southbound
are not a result of independent computation by every node over the
same set of South TIEs, TIEs but a diffused computation.
6.8.5.2. Northbound
Certain use cases necessitate distribution of essential KV
information that is generated by the leaves in the northbound
direction. Such information is flooded in KV North TIEs. Since the
originator of the KV North TIEs is preserved during flooding, the
corresponding mechanism will define, if necessary, tie-breaking rules
depending on the semantics of the information.
Only KV TIEs from nodes that are reachable via multiplane multi-plane
reachability computation mentioned in Section 6.5.2.3 SHOULD be
considered.
6.8.6. Interactions with BFD
RIFT MAY incorporate BFD Bidirectional Forwarding Detection (BFD)
[RFC5881] to react quickly to link failures. In such case, the
following procedures are introduced:
1. After RIFT _ThreeWay_ hello adjacency convergence convergence, a BFD session
MAY be formed automatically between the RIFT endpoints without
further configuration using the exchanged discriminators that are
equal to the _local_id_ in the _LIEPacket_. The capability of the
remote side to support BFD is carried in the LIEs in
_LinkCapabilities_.
2. In case an established BFD session goes Down down after it was Up, up,
RIFT adjacency SHOULD be re-initialized and subsequently started
from Init after it receives a consecutive BFD Up.
3. In case of parallel links between nodes nodes, each link MAY run its
own independent BFD session or they MAY share a session. The
specific manner in which this is implemented is outside the scope
of this document.
4. If link identifiers or BFD capabilities change, both the LIE and
any BFD sessions SHOULD be brought down and back up again. In
case only the advertised capabilities change, the node MAY choose
to persist the BFD session.
5. Multiple RIFT instances MAY choose to share a single BFD session, session;
in such cases cases, the behavior for which discriminators are used is
undefined. However, RIFT MAY advertise the same link ID for the
same interface in multiple instances to "share" discriminators.
6. The BFD TTL follows [RFC5082].
6.8.7. Fabric Bandwidth Balancing
A well understood problem in fabrics is that, in case of link
failures, it would be ideal to rebalance how much traffic is sent to
switches in the next level based on the available ingress and egress
bandwidth.
RIFT supports a light-weight mechanism that can deal with the problem
based on the fact that RIFT is loop-free.
6.8.7.1. Northbound Direction
Every RIFT node SHOULD compute the amount of northbound bandwidth
available through neighbors at a higher level and modify the distance
received on the default route from these neighbors. The bandwidth is
advertised in the _NodeNeighborsTIEElement_ element element, which represents
the sum of the bandwidths of all the parallel links to a neighbor.
Default routes with differing distances SHOULD be used to support
weighted ECMP forwarding. Such a distance is called Bandwidth
Adjusted Distance (BAD). This is best illustrated by a simple
example.
100 x 100 100 MBits Mbit/s
| x | |
+-+---+-+ +-+---+-+
| | | |
|Spin111| |Spin112|
+-+---+++ ++----+++
|x || || ||
|| |+---------------+ ||
|| +---------------+| ||
|| || || ||
|| || || ||
-----All Links 10 MBit------- Mbit/s-----
|| || || ||
|| || || ||
|| +------------+| || ||
|| |+------------+ || ||
|x || || ||
+-+---+++ +--++-+++
| | | |
|Leaf111| |Leaf112|
+-------+ +-------+
Figure 32: Balancing Bandwidth
Figure 32 depicts an example topology where links between leaf and
spine nodes are 10 MBit/s Mbit/s and links from spine nodes northbound are
100 MBit/s. Mbit/s. It includes parallel link failure between Leaf 111 and
Spine 111 111, and as a result, Leaf 111 wants to forward more traffic
toward
towards Spine 112. Additionally, it includes as well an uplink failure on
Spine 111.
The local modification of the received default route distance from
the upper level is achieved by running a relatively simple algorithm
where the bandwidth is weighted exponentially, while the distance on
the default route represents a multiplier for the bandwidth weight
for easy operational adjustments.
On a node, L, use Node TIEs to compute from each non-overloaded
northbound neighbor N to compute 3 values:
1. L_N_u: sum of the bandwidth available from L to N (to account for
parallel links)
2. N_u: sum of the uplink bandwidth available on N
3. T_N_u: L_N_u * OVERSUBSCRIPTION_CONSTANT + N_u
For all T_N_u T_N_u, determine the corresponding M_N_u as
log_2(next_power_2(T_N_u)) and determine MAX_M_N_u as the maximum
value of all such M_N_u values.
For each advertised default route from a node N N, modify the
advertised distance D to BAD = D * (1 + MAX_M_N_u - M_N_u) and use
BAD instead of distance D to weight balance the weight of the default
forwarding towards N.
For the example above, a simple table of values will help in
understanding of the concept. The implicit assumption here is that all
default route distances are advertised with D=1 and that
OVERSUBSCRIPTION_CONSTANT = 1.
OVERSUBSCRIPTION_CONSTANT=1.
+=========+===========+=======+=======+=====+
| Node | N | T_N_u | M_N_u | BAD |
+=========+===========+=======+=======+=====+
| Leaf111 | Spine 111 | 110 | 7 | 2 |
+---------+-----------+-------+-------+-----+
| Leaf111 | Spine 112 | 220 | 8 | 1 |
+---------+-----------+-------+-------+-----+
| Leaf112 | Spine 111 | 120 | 7 | 2 |
+---------+-----------+-------+-------+-----+
| Leaf112 | Spine 112 | 220 | 8 | 1 |
+---------+-----------+-------+-------+-----+
Table 6: BAD Computation
If a calculation produces a result exceeding the range of the type,
e.g.
e.g., bandwidth, the result is set to the highest possible value for
that type.
BAD SHOULD only be computed for default routes. A node MAY compute
and use BAD for any disaggregated prefixes or other RIFT routes. A
node MAY use a different algorithm to weight northbound traffic based
on the bandwidth. If a different algorithm is used, its successful
behavior MUST NOT depend on uniformity of the algorithm or
synchronization of BAD computations across the fabric. E.g. For example,
it is conceivable that leaves could use real time link loads gathered
by analytics to change the amount of traffic assigned to each default
route next hop.
A change in available bandwidth will only affect, at most, two levels
down in the fabric, i.e., the blast radius of bandwidth adjustments
is constrained no matter the fabric's height.
6.8.7.2. Southbound Direction
Due to its loop free loop-free nature, during South SPF, a node MAY account for
the maximum available bandwidth on nodes in lower levels and modify
the amount of traffic offered to the next level's southbound nodes.
It is worth considering that such computations may be more effective
if they are standardized, but they do not have to be. As long as a
packet continues to flow southbound, it will take some viable, loop-free loop-
free path to reach its destination.
6.8.8. Label Binding
A
In its LIEs, a node MAY advertise in its LIEs, a locally significant, downstream downstream-
assigned, interface specific interface-specific label. One use of such a label is a
hop-by-hop encapsulation allowing forwarding planes to be easily
distinguished among multiple RIFT instances.
6.8.9. Leaf to Leaf Leaf-to-Leaf Procedures
RIFT implementations SHOULD support special East-West adjacencies
between leaf nodes. Leaf nodes supporting these procedures MUST:
1. advertise the LEAF_2_LEAF flag in its node capabilities *and* capabilities,
2. set the overload flag on all leaf's Node TIEs *and* TIEs,
3. flood only a node's own north North and south South TIEs over E-W leaf
adjacencies *and*
adjacencies,
4. always use E-W leaf adjacency in all SPF computations *and* computations,
5. install a discard route for any advertised aggregate routes in a
leaf's TIE TIE, *and*
6. never form southbound adjacencies.
This will allow the E-W leaf nodes to exchange traffic strictly for
the prefixes advertised in each other's north prefix TIEs since the
southbound computation will find the reverse direction in the other
node's TIE and install its north prefixes.
6.8.10. Address Family and Multi Topology Multi-Topology Considerations
Multi-Topology (MT)[RFC5120] (MT) [RFC5120] and Multi-Instance (MI)[RFC8202] (MI) [RFC8202]
concepts are used today in link-state routing protocols to support
several domains on the same physical topology. RIFT supports this
capability by carrying transport ports in the LIE protocol exchanges.
Multiplexing of LIEs can be achieved by either choosing varying
multicast addresses or ports on the same address.
BFD interactions in Section 6.8.6 are implementation dependent implementation-dependent when
multiple RIFT instances run on the same link.
6.8.11. One-Hop Healing of Levels with East-West Links
Based on the rules defined in Section 6.4, Section Sections 6.4 and 6.3.8 and given the
presence of E-W links, RIFT can provide a one-hop protection for
nodes that have lost all their northbound links. This can also be
applied to multi-plane designs where complex link set failures occur
at the ToF when links are exclusively used for flooding topology
information. Appendix B.4 outlines this behavior.
6.9. Security
6.9.1. Security Model
An inherent property of any security and ZTP architecture is the
resulting trade-off in regard to integrity verification of the
information distributed through the fabric vs. provisioning and auto-
configuration
autoconfiguration requirements. At a minimum minimum, the security of an
established adjacency should be ensured. The stricter the security
model
model, the more provisioning must take over the role of ZTP.
RIFT supports the following security models to allow for flexible
control by the operator. operator:
* The most security conscious security-conscious operators may choose to have control
over which ports interconnect between a given pair of nodes, such
a model is called the "Port-Association Model" (PAM). This is
achievable by configuring each pair of directly connected ports
with a designated shared key or public/private key pair.
* In physically secure data center locations, operators may choose
to control connectivity between entire nodes, called here the
"Node-Association Model" (NAM). A benefit of this model is that
it allows for simplified port sparing.
* In the most relaxed environments, an operator may only choose to
control which nodes join a particular fabric. This is denoted as
the "Fabric-Association Model" (FAM). This is achievable by using
a single shared secret across the entire fabric. Such flexibility
makes sense when servers are considered as leaf devices, as those
are replaced more often than network nodes. In addition, this
model allows for simplified node sparing.
* These models may be mixed throughout the fabric depending upon
security requirements at various levels of the fabric and
willingness to accept increased provisioning complexity.
In order to support the cases mentioned above, RIFT implementations
supports, through operator control, mechanisms that allow for:
a.
* a specification of the appropriate level in the fabric,
b.
* discovery and reporting of missing connections,
c. and
* discovery and reporting of unexpected connections while preventing
them from forming insecure adjacencies.
Operators may only choose to configure the level of each node, node but not
explicitly configure which connections are allowed. In this case,
RIFT will only allow adjacencies to establish between nodes that are
in adjacent levels. Operators with the lowest security requirements
may not use any configuration to specify which connections are
allowed. Nodes in such fabrics could rely fully on ZTP and only
established adjacencies between nodes in adjacent levels. Figure 33
illustrates inherent tradeoffs trade-offs between the different security
models.
Some level of link quality verification may be required prior to an
adjacency being used for forwarding. For example, an implementation
may require that a BFD session comes up before advertising the
adjacency.
For the cases outlined above, RIFT has two approaches to enforce that
a local port is connected to the correct port on the correct remote
node. One approach is to piggy-back piggyback on RIFT's authentication
mechanism. Assuming the provisioning model (e.g. (e.g., YANG) is flexible
enough, operators can choose to provision a unique authentication key
for the following conceptual models:
a.
* each pair of ports in "port-association model" or
b.
* each pair of switches in "node-association model" model", or
c.
* the entire fabric in "fabric-association model".
The other approach is to rely on the System ID, port-id port-id, and level
fields in the LIE message to validate an adjacency against the
expected cabling topology, topology and optionally introduce some new rules in
the FSM to allow the adjacency to come up if the expectations are
met.
^ /\ |
/|\ / \ |
| / \ |
| / PAM \ |
Increasing / \ Increasing
Integrity +----------+ Flexibility
& / NAM \ &
Increasing +--------------+ Less
Provisioning / FAM \ Configuration
| / \ |
| +--------------------+ \|/
| / Zero Configuration \ v
+------------------------+
Figure 33: Security Model
6.9.2. Security Mechanisms
RIFT Security security goals are to ensure:
1. authentication
2.
* authentication,
* message integrity
3. integrity,
* the prevention of replay attacks
4. attacks,
* low processing overhead
5. overhead, and
* efficient messaging
unless no security is deployed by means of using
`undefined_securitykey_id`
'undefined_securitykey_id' as key identifiers.
Message confidentiality is a non-goal.
The model in the previous section allows a range of security key
types that are analogous to the various security association models.
PAM and NAM allow security associations at the port or node level
using symmetric or asymmetric keys that are pre-installed. preinstalled. FAM argues
for security associations to be applied only at a group level or to
be refined once the topology has been established. RIFT does not
specify how security keys are installed or updated, though it does
specify how the key can be used to achieve security goals.
The protocol has provisions for "weak" nonces to prevent replay
attacks and includes authentication mechanisms comparable to those
described in [RFC5709] and [RFC7987].
6.9.3. Security Envelope
A serialized schema _ProtocolPacket_ MUST be carried in a secure
envelope as illustrated in Figure 34. The _ProtocolPacket_ MUST be
serialized using the default Thrift's Binary Protocol. binary protocol. Any value in
the packet following a security fingerprint MUST be used by a
receiver only after the fingerprint generated based on acceptable,
advertised key ID has been validated against the data covered by it
bare exceptions arising from operational exigencies where, based on
local configuration, a node MAY allow for the envelope's integrity
checks to be skipped and for behavior specified in Section 6.9.6.
This means that for all packets, in case the node is configured to
validate the outer fingerprint based on a key ID, an unexpected key
ID or fingerprint not validating against the expected key ID will
lead to packet rejection. Further, in case of reception of a TIE, TIE and
the receiver being configured to validate the originator by checking
the TIE Origin Security Envelope Header fingerprint against a key ID,
an incorrect key ID or inner fingerprint not validating against the
key ID will lead to the rejection of the packet.
For reasons of clarity clarity, it is important to observe that the
specification uses the word fingerprint words "fingerprint" and signature "signature"
interchangeably since the specific properties of the fingerprint part
of the envelope depend on the algorithms used to insure the payload
integrity. Moreover, any security chosen never implies encryption
due to performance impact involved but only fingerprint or signature
generation and validation.
An implementation MUST implement at least both sending and receiving
HMAC-SHA256 fingerprints as defined in Section 10.2 to ensure
interoperability but MAY use `undefined_securitykey_id` 'undefined_securitykey_id' by default.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
UDP Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port | RIFT destination port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Outer Security Envelope Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RIFT MAGIC | Packet Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | RIFT Major | Outer Key ID | Fingerprint |
| | Version | | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Security Fingerprint covers all following content ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weak Nonce Local | Weak Nonce Remote |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remaining TIE Lifetime (all 1s in case of LIE) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TIE Origin Security Envelope Header:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TIE Origin Key ID | Fingerprint |
| | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Security Fingerprint covers all following content ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Serialized RIFT Model Object
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Serialized RIFT Model Object ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 34: Security Envelope
RIFT MAGIC: 16 bits. bits
Constant value of 0xA1F7 that allows easy classification of RIFT
packets independent of the UDP port used.
Packet Number: 16 bits. bits
An optional, per adjacency, per packet per-adjacency, per-packet type number set using the
sequence number arithmetic defined in Appendix A. If the
arithmetic in Appendix A is not used used, the node MUST set the value
to _undefined_packet_number_. This number can be used to detect
losses and misordering in flooding for either operational purposes
or in implementation to adjust flooding behavior to current link
or buffer quality. This number MUST NOT be used to discard or
validate the correctness of packets. Packet numbers are
incremented on each interface and within that for each type of
packet independently. This allows parallelizing packet generation
and processing for different types within an implementation implementation, if so
desired.
RIFT Major Version: 8 bits. bits
This value MUST be set to `protocol_major_version` "protocol_major_version", which is
defined in the schema and used to serialize the object contained.
It allows checking whether protocol versions are compatible on
both sides, i.e., which schema version is necessary to decode the
serialized object. An implementation MUST drop packets with
unexpected values and MAY report a problem. The specification of
how an implementation may negotiate the schema's major version is
outside the scope of this document.
Outer Key ID: 8 bits. bits
A simple, unstructured value acting as indirection into a
structure holding an algorithm and any related secrets necessary
to validate any provided outer security fingerprint or signature.
Value
The value _undefined_securitykey_id_ means that no valid
fingerprint was computed or is provided, otherwise provided; otherwise, one of the
algorithms in Section 10.2 MUST be used to compute the
fingerprint. This Key key ID scope is local to the nodes on both ends
of the adjacency.
TIE Origin Key ID: 24 bits. bits
A simple, unstructured value acting as indirection into a
structure holding an algorithm and any related secrets necessary
to validate any provided inner security fingerprint or signature.
Value
The value _undefined_securitykey_id_ means that no valid
fingerprint was computed, otherwise computed; otherwise, one of the algorithms in
Section 10.2 MUST be used to compute the fingerprint.. fingerprint. This Key key ID
scope is global to the RIFT instance since it may imply the
originator of the TIE so the contained object does not have to be de-serialized
deserialized to obtain the originator.
Length of Fingerprint:
Fingerprint Length: 8 bits. bits
Length in 32-bit multiples of the following fingerprint (not
including lifetime or weak nonces). It allows the structure to be
navigated when an unknown key type is present. To clarify, a
common corner case when this value is set to 0 is when it
signifies an empty (0 bytes long) security fingerprint.
Security Fingerprint: 32 bits * Length of Fingerprint. Fingerprint Length.
This is a signature that is computed over all data following after
it. If the significant bits of the fingerprint are fewer than the 32 bits
32-bit padded length length, then the significant bits MUST be left
aligned and the remaining bits on the right are padded with 0s.
When using PKI (Public Public Key
Infrastructure) Infrastructure (PKI), the Security security
fingerprint originating node uses its private key to create the
signature. The original packet can then be verified verified, provided the
public key is shared and current. Methodology to negotiate,
distribute, or roll over rollover keys are is outside the scope of this
document.
Remaining TIE Lifetime: 32 bits. bits
In case of anything but TIEs TIEs, this field MUST be set to all ones
and the Origin Security Envelope Header MUST NOT be present in the
packet. For TIEs TIEs, this field represents the remaining lifetime of
the TIE and the Origin Security Envelope Header MUST be present in
the packet.
Weak Nonce Local: 16 bits. bits
Local Weak Nonce of the adjacency adjacency, as advertised in LIEs.
Weak Nonce Remote: 16 bits. bits
Remote Weak Nonce of the adjacency adjacency, as received in LIEs.
TIE Origin Security Envelope Header: It MUST be present if and only
if the Remaining TIE Lifetime field is *not* all ones. It carries
through the originators Key originator's key ID and corresponding fingerprint of
the object to protect TIE from modification during flooding. This
ensures origin validation and integrity (but does not provide
validation of a chain of trust).
Observe that that, due to the schema migration rules per Section 7 7, the
contained model can be always be decoded if the major version matches
and the envelope integrity has been validated. Consequently,
description of the TIE is available to flood it properly properly, including
unknown TIE types.
6.9.4. Weak Nonces
The protocol uses two 16-bit nonces to salt generated signatures.
The term "nonce" is used a bit loosely since RIFT nonces are not
being changed in every packet as often packet, which is common in cryptography. For
efficiency purposes purposes, they are changed at a high enough frequency to
dwarf practical replay attack attempts. And hence, such nonces are
called from this point on "weak" nonces.
Any implementation using a different outer key ID different from
`undefined_securitykey_id`
'undefined_securitykey_id' MUST generate and wrap around local nonces
properly and SHOULD do it even if not using any algorithm in from
Section 10.2. When a nonce increment leads to the _undefined_nonce_
value, the value MUST be incremented again immediately. All
implementations MUST reflect the neighbor's nonces. An
implementation SHOULD increment a chosen nonce on every LIE FSM
transition that ends up in a different state from the previous one
and MUST increment its nonce at least every
_nonce_regeneration_interval_ if using any algorithm in Section 10.2
(such considerations allow for efficient implementations without
opening a significant security risk). When flooding TIEs, the
implementation MUST use recent (i.e. (i.e., within allowed difference)
nonces reflected in the LIE exchange. The schema specifies in
_maximum_valid_nonce_delta_ the maximum allowable nonce value
difference on a packet compared to reflected nonces in the LIEs. Any
packet received with nonces deviating more than the allowed delta
MUST be discarded without further computation of signatures to
prevent computation load attacks. The delta is either a negative or
positive difference that a mirrored nonce can deviate from the local
value to be considered valid. If nonces are not changed on every
packet
packet, but at the maximum interval on both sides sides, this opens
statistically a _maximum_valid_nonce_delta_/2 window for identical
LIEs, TIE TIE, and TI(x)E replays. The interval cannot be too small
since LIE FSM may change states fairly quickly during ZTP without
sending
LIEs LIEs, and additionally, UDP can both loose as well as
misorder packets.
In cases where a secure implementation does not receive signatures or
receives undefined nonces from a neighbor (indicating that it does
not support or verify signatures), it is a matter of local policy as
to how those packets are treated. A secure implementation MAY refuse
forming an adjacency with an implementation that is not advertising
signatures or valid nonces, or it MAY continue signing local packets
while accepting a neighbor's packets without further security
validation.
As a necessary exception, an implementation MUST advertise the remote
nonce value as _undefined_nonce_ when the FSM is not in _TwoWay_ or
_ThreeWay_ state and accept an _undefined_nonce_ for its local nonce
value on packets in any other state than _ThreeWay_.
As an optional optimization, an implementation MAY send one LIE with
a previously negotiated neighbor's nonce to try to speed up a
neighbor's transition from _ThreeWay_ to _OneWay_ and MUST revert to
sending _undefined_nonce_ after that.
6.9.5. Lifetime
Reflooding the same TIE version quickly with small variations in its
lifetime may lead to an excessive number of security fingerprint
computations. To avoid this, the application generating the
fingerprints for flooded TIEs MAY round the value down to the next
_rounddown_lifetime_interval_ on the packet header to reuse previous
computation results. TIEs flooded with such rounded lifetimes only will
only limit the amount of computations necessary during transitions
that lead to advertisement of the same TIEs with the same information
within a short period of time.
6.9.6. Security Association Changes
No mechanism is specified to convert a security envelope for the same
Key
key ID from one algorithm to another once the envelope is
operational. The recommended procedure to change to a new algorithm
is to take the adjacency down, make the necessary changes to the
secret and algorithm used by the according key ID, and bring the
adjacency back up. Obviously, an implementation MAY choose to stop
verifying the security envelope for the duration of the algorithm
change to keep the adjacency up up, but since this introduces a security
vulnerability window, such roll-over rollover SHOULD NOT be recommended. Other
approaches, such as accepting multiple algorithms for same key ID for
a configured time window window, are possible but in the realm of
implementation choices rather than protocol specification.
7. Information Elements Schema
This section introduces the schema for information elements. The IDL
is Thrift [thrift].
On schema changes that
1. change field numbers *or* numbers,
2. add new *required* fields *or* fields,
3. remove any fields *or* fields.
4. change lists into sets, sets and unions into structures *or* structures,
5. change the multiplicity of fields *or* fields,
6. changes change the type or name of any field *or* field,
7. change data types of the type of any field *or* field,
8. adds, changes add, change, or removes remove a default value of any *existing* field
*or* field,
9. removes remove or changes change any defined constant or constant value *or* value,
10. changes change any enumeration type except extending
`common.TIETypeType`
'common.TIETypeType' (use of enumeration types is generally
discouraged) *or*
discouraged), or
11. adds add a new TIE type to _TIETypeType_ with the flooding scope
different from the prefix TIE flooding scope
the major version of the schema MUST increase. All other changes
MUST increase the minor version within the same major.
Introducing an optional field does not cause a major version increase
even if the fields inside the structure are optional with defaults.
All signed integer integers, as forced by Thrift [thrift] support support, must be
cast for internal purposes to equivalent unsigned values without
discarding the signedness bit. An implementation SHOULD try to avoid
using the signedness bit when generating values.
The schema is normative.
7.1. Backwards-Compatible Extension of Schema
The set of rules in Section 7 guarantees that every decoder can
process serialized content generated by a higher minor version of the
schema
schema, and with that that, the protocol can progress without a 'flag-day'. 'flag-
day'. Contrary to that, content serialized using a major version X
is *not* expected to be decodable by any implementation using a
decoder for a model with a major version lower than X. Schema
negotiation and translation within RIFT is outside the scope of this
document.
Additionally, based on the propagated minor version in encoded
content and added optional node capabilities capabilities, new TIE types or even
de-facto
de facto mandatory fields can be introduced without progressing the
major version version, albeit only nodes supporting such new extensions would
decode them. Given the model is encoded at the source and never re-
encoded
encoded, flooding through nodes not understanding any new extensions
will preserve the corresponding fields. However, it is important to
understand that a higher minor version of a schema does *not*
guarantee that capabilities introduced in lower minors of the same
major are supported. The _node_capabilities_ field is used to
indicate which capabilities are supported.
Specifically, the schema SHOULD add elements to the
_NodeCapabilities_
field field's future capabilities to indicate whether it
will support interpretation of schema extensions on the same major
revision if they are present. Such fields MUST be optional and have
an implicit or explicit false default value. If a future capability
changes route selection or generates conditions that cause packet
loss if some nodes are not supporting it it, then a major version
increment will be however unavoidable. _NodeCapabilities_ shown in LIE MUST
match the capabilities shown in the Node TIEs, otherwise TIEs; otherwise, the
behavior is unspecified. A node detecting the mismatch SHOULD
generate a notification.
Alternately or additionally, new optional fields can be introduced
into e.g. _NodeTIEElement_
into, e.g., _NodeTIEElement_, if a special field is chosen to
indicate via its presence that an optional feature is enabled (since
capability to support a feature does not necessarily mean that the
feature is actually configured and operational).
To support new TIE types without increasing the major version
enumeration
enumeration, _TIEElement_ can be extended with new optional elements
for new `common.TIETypeType` 'common.TIETypeType' values as long the scope of the new TIE
matches the prefix TIE scope. In case it is necessary to understand
whether all nodes can parse the new TIE type type, a node capability MUST
be added in _NodeCapabilities_ to prevent a non-homogenous network.
7.2. common.thrift
/**
Thrift file with common definitions for RIFT
*/
namespace py common
/** @note MUST be interpreted in implementation as unsigned 64 bits.
*/
typedef i64 SystemIDType
typedef i32 IPv4Address
typedef i32 MTUSizeType
/** @note MUST be interpreted in implementation as unsigned
rolling over number */
typedef i64 SeqNrType
/** @note MUST be interpreted in implementation as unsigned */
typedef i32 LifeTimeInSecType
/** @note MUST be interpreted in implementation as unsigned */
typedef i8 LevelType
typedef i16 PacketNumberType
/** @note MUST be interpreted in implementation as unsigned */
typedef i32 PodType
/** @note MUST be interpreted in implementation as unsigned.
/** this has to be long enough to accomodate accommodate prefix */
typedef binary IPv6Address
/** @note MUST be interpreted in implementation as unsigned */
typedef i16 UDPPortType
/** @note MUST be interpreted in implementation as unsigned */
typedef i32 TIENrType
/** @note MUST be interpreted in implementation as unsigned
This is carried in the security envelope and must
hence fit into 8 bits. */
typedef i8 VersionType
/** @note MUST be interpreted in implementation as unsigned */
typedef i16 MinorVersionType
/** @note MUST be interpreted in implementation as unsigned */
typedef i32 MetricType
/** @note MUST be interpreted in implementation as unsigned
and unstructured */
typedef i64 RouteTagType
/** @note MUST be interpreted in implementation as unstructured
label value */
typedef i32 LabelType
/** @note MUST be interpreted in implementation as unsigned */
typedef i32 BandwithInMegaBitsType BandwidthInMegaBitsType
/** @note Key Value Key key ID type */
typedef i32 KeyIDType
/** node local, unique identification for a link (interface/tunnel (interface/tunnel/
* etc. Basically etc., basically anything RIFT runs on). This is kept
* at 32 bits so it aligns with BFD [RFC5880] (RFC 5880) discriminator size.
*/
typedef i32 LinkIDType
/** @note MUST be interpreted in implementation as unsigned,
especially since we have the /128 IPv6 case. */
typedef i8 PrefixLenType
/** timestamp in seconds since the epoch */
typedef i64 TimestampInSecsType
/** security nonce.
@note MUST be interpreted in implementation as rolling
over unsigned value */
typedef i16 NonceType
/** LIE FSM holdtime type */
typedef i16 TimeIntervalInSecType
/** Transaction ID type for prefix mobility as specified by RFC6550, RFC 6550,
value MUST be interpreted in implementation as unsigned */
typedef i8 PrefixTransactionIDType
/** Timestamp per IEEE 802.1AS, all values MUST be interpreted in
implementation as unsigned. */
struct IEEE802_1ASTimeStampType {
1: required i64 AS_sec;
2: optional i32 AS_nsec;
}
/** generic counter type */
typedef i64 CounterType
/** Platform Interface Index type, i.e. i.e., index of interface on hardware,
can be used e.g. used, e.g., with RFC5837 RFC 5837 */
typedef i32 PlatformInterfaceIndex
/** Flags indicating node configuration in case of ZTP.
*/
enum HierarchyIndications {
/** forces level to `leaf_level` 'leaf_level' and enables according procedures */
leaf_only = 0,
/** forces level to `leaf_level` 'leaf_level' and enables according procedures */
leaf_only_and_leaf_2_leaf_procedures = 1,
/** forces level to `top_of_fabric` 'top_of_fabric' and enables according
procedures */
top_of_fabric = 2,
}
const PacketNumberType undefined_packet_number = 0
/** used when node is configured as top of fabric in ZTP.*/
const LevelType top_of_fabric_level = 24
/** default bandwidth on a link */
const BandwithInMegaBitsType BandwidthInMegaBitsType default_bandwidth = 100
/** fixed leaf level when ZTP is not used */
const LevelType leaf_level = 0
const LevelType default_level = leaf_level
const PodType default_pod = 0
const LinkIDType undefined_linkid = 0
/** invalid key for key value */
const KeyIDType invalid_key_value_key = 0
/** default distance used */
const MetricType default_distance = 1
/** any distance larger than this will be considered infinity */
const MetricType infinite_distance = 0x7FFFFFFF
/** represents invalid distance */
const MetricType invalid_distance = 0
const bool overload_default = false
const bool flood_reduction_default = true
/** default LIE FSM LIE TX internval interval time */
const TimeIntervalInSecType default_lie_tx_interval = 1
/** default LIE FSM holddown time */
const TimeIntervalInSecType default_lie_holdtime = 3
/** multipler for default_lie_holdtime to hold down multiple neighbors */
const i8 multiple_neighbors_lie_holdtime_multipler = 4
/** default ZTP FSM holddown time */
const TimeIntervalInSecType default_ztp_holdtime = 1
/** by default LIE levels are ZTP offers */
const bool default_not_a_ztp_offer = false
/** by default everyone is repeating flooding */
const bool default_you_are_flood_repeater = true
/** 0 is illegal for SystemID System IDs */
const SystemIDType IllegalSystemID = 0
/** empty set of nodes */
const set<SystemIDType> empty_set_of_nodeids = {}
/** default lifetime of TIE is one week */
const LifeTimeInSecType default_lifetime = 604800
/** default lifetime when TIEs are purged is 5 minutes */
const LifeTimeInSecType purge_lifetime = 300
/** optional round down interval when TIEs are sent with security signatures
to prevent excessive computation. **/
const LifeTimeInSecType rounddown_lifetime_interval = 60
/** any `TieHeader` 'TieHeader' that has a smaller lifetime difference
than this constant is equal (if other fields equal). */
const LifeTimeInSecType lifetime_diff2ignore = 400
/** default UDP port to run LIEs on */
const UDPPortType default_lie_udp_port = 914
/** default UDP port to receive TIEs on, that which can be peer specific */
const UDPPortType default_tie_udp_flood_port = 915
/** default MTU link size to use */
const MTUSizeType default_mtu_size = 1400
/** default link being BFD capable */
const bool bfd_default = true
/** type used to target nodes with key value */
typedef i64 KeyValueTargetType
/** default target for key value are all nodes. */
const KeyValueTargetType keyvaluetarget_default = 0
/** value for _all leaves_ addressing. Represented by all bits set. */
const KeyValueTargetType keyvaluetarget_all_south_leaves = -1
/** undefined nonce, equivalent to missing nonce */
const NonceType undefined_nonce = 0;
/** outer security Key key ID, MUST be interpreted as in implementation
as unsigned */
typedef i8 OuterSecurityKeyID
/** security Key key ID, MUST be interpreted as in implementation
as unsigned */
typedef i32 TIESecurityKeyID
/** undefined key */
const TIESecurityKeyID undefined_securitykey_id = 0;
/** Maximum delta (negative or positive) that a mirrored nonce can
deviate from local value to be considered valid. */
const i16 maximum_valid_nonce_delta = 5;
const TimeIntervalInSecType nonce_regeneration_interval = 300;
/** Direction of TIEs. */
enum TieDirectionType {
Illegal = 0,
South = 1,
North = 2,
DirectionMaxValue = 3,
}
/** Address family type. */
enum AddressFamilyType {
Illegal = 0,
AddressFamilyMinValue = 1,
IPv4 = 2,
IPv6 = 3,
AddressFamilyMaxValue = 4,
}
/** IPv4 prefix type. */
struct IPv4PrefixType {
1: required IPv4Address address;
2: required PrefixLenType prefixlen;
}
/** IPv6 prefix type. */
struct IPv6PrefixType {
1: required IPv6Address address;
2: required PrefixLenType prefixlen;
}
/** IP address type. */
union IPAddressType {
/** Content is IPv4 */
1: optional IPv4Address ipv4address;
/** Content is IPv6 */
2: optional IPv6Address ipv6address;
}
/** Prefix advertisement.
@note: for For interface
addresses
addresses, the protocol can propagate the address part beyond
the subnet mask and on reachability computation that has to
be normalized. The non-significant bits can be used
for operational purposes.
*/
union IPPrefixType {
1: optional IPv4PrefixType ipv4prefix;
2: optional IPv6PrefixType ipv6prefix;
}
/** Sequence of a prefix in case of move.
*/
struct PrefixSequenceType {
1: required IEEE802_1ASTimeStampType timestamp;
/** Transaction ID set by the client in e.g. in in, e.g., 6LoWPAN. */
2: optional PrefixTransactionIDType transactionid;
}
/** Type of TIE.
*/
enum TIETypeType {
Illegal = 0,
TIETypeMinValue = 1,
/** first legal value */
NodeTIEType = 2,
PrefixTIEType = 3,
PositiveDisaggregationPrefixTIEType = 4,
NegativeDisaggregationPrefixTIEType = 5,
PGPrefixTIEType = 6,
KeyValueTIEType = 7,
ExternalPrefixTIEType = 8,
PositiveExternalDisaggregationPrefixTIEType = 9,
TIETypeMaxValue = 10,
}
/** RIFT route types.
@note: The only purpose of those values is to introduce an
ordering
ordering, whereas an implementation can choose internally choose
any other values as long the ordering is preserved preserved.
*/
enum RouteType {
Illegal = 0,
RouteTypeMinValue = 1,
/** First legal value. */
/** Discard routes are most preferred */
Discard = 2,
/** Local prefixes are directly attached prefixes on the
* system system, such as e.g. interface routes.
*/
LocalPrefix = 3,
/** Advertised in S-TIEs */
SouthPGPPrefix = 4,
/** Advertised in N-TIEs */
NorthPGPPrefix = 5,
/** Advertised in N-TIEs */
NorthPrefix = 6,
/** Externally imported north */
NorthExternalPrefix = 7,
/** Advertised in S-TIEs, either normal prefix or positive
disaggregation */
SouthPrefix = 8,
/** Externally imported south */
SouthExternalPrefix = 9,
/** Negative, transitive prefixes are least preferred */
NegativeSouthPrefix = 10,
RouteTypeMaxValue = 11,
}
enum KVTypes {
Experimental = 1,
WellKnown = 2,
OUI = 3,
}
7.3. encoding.thrift
/**
Thrift file for packet encodings for RIFT
*/
include "common.thrift"
namespace py encoding
/** Represents protocol encoding schema major version */
const common.VersionType protocol_major_version = 8
/** Represents protocol encoding schema minor version */
const common.MinorVersionType protocol_minor_version = 0
/** Common RIFT packet header. */
struct PacketHeader {
/** Major version of protocol. */
1: required common.VersionType major_version =
protocol_major_version;
/** Minor version of protocol. */
2: required common.MinorVersionType minor_version =
protocol_minor_version;
/** Node sending the packet, in case of LIE/TIRE/TIDE
also the originator of it. */
3: required common.SystemIDType sender;
/** Level of the node sending the packet, required on everything
except LIEs. Lack of presence on LIEs indicates
UNDEFINED_LEVEL and is used in ZTP procedures.
*/
4: optional common.LevelType level;
}
/** Prefix community. */
struct Community {
/** Higher order bits */
1: required i32 top;
/** Lower order bits */
2: required i32 bottom;
}
/** Neighbor structure. */
struct Neighbor {
/** System ID of the originator. */
1: required common.SystemIDType originator;
/** ID of remote side of the link. */
2: required common.LinkIDType remote_id;
}
/** Capabilities the node supports. */
struct NodeCapabilities {
/** Must advertise supported minor version dialect that way. */
1: required common.MinorVersionType protocol_minor_version =
protocol_minor_version;
/** indicates that node supports flood reduction. */
2: optional bool flood_reduction =
common.flood_reduction_default;
/** indicates place in hierarchy, i.e. top-of-fabric i.e., top of fabric or
leaf only (in ZTP) or support for leaf-2-leaf leaf-to-leaf
procedures. */
3: optional common.HierarchyIndications hierarchy_indications;
}
/** Link capabilities. */
struct LinkCapabilities {
/** Indicates that the link is supporting BFD. */
1: optional bool bfd =
common.bfd_default;
/** Indicates whether the interface will support IPv4
forwarding. */
2: optional bool ipv4_forwarding_capable =
true;
}
/** RIFT LIE Packet.
@note: this This node's level is already included on the packet header header.
*/
struct LIEPacket {
/** Node or adjacency name. */
1: optional string name;
/** Local link ID. */
2: required common.LinkIDType local_id;
/** UDP port to which we can receive flooded TIEs. */
3: required common.UDPPortType flood_port =
common.default_tie_udp_flood_port;
/** Layer 2 MTU, used to discover mismatch. */
4: optional common.MTUSizeType link_mtu_size =
common.default_mtu_size;
/** Local link bandwidth on the interface. */
5: optional common.BandwithInMegaBitsType common.BandwidthInMegaBitsType
link_bandwidth = common.default_bandwidth;
/** Reflects the neighbor once received to provide
3-way connectivity. */
6: optional Neighbor neighbor;
/** Node's PoD. */
7: optional common.PodType pod =
common.default_pod;
/** Node capabilities supported. */
10: required NodeCapabilities node_capabilities;
/** Capabilities of this link. */
11: optional LinkCapabilities link_capabilities;
/** Required holdtime of the adjacency, i.e. i.e., for how long a
period should adjacency should be kept up without valid LIE
reception. */
12: required common.TimeIntervalInSecType
holdtime = common.default_lie_holdtime;
/** Optional, unsolicited, downstream assigned locally significant
label value for the adjacency. */
13: optional common.LabelType label;
/** Indicates that the level on the LIE must not be used
to derive a ZTP level by the receiving node. */
21: optional bool not_a_ztp_offer =
common.default_not_a_ztp_offer;
/** Indicates to northbound neighbor that it should
be reflooding TIEs received from this node to achieve flood
reduction and balancing for northbound flooding. */
22: optional bool you_are_flood_repeater =
common.default_you_are_flood_repeater;
/** Indicates to neighbor to flood node TIEs only and slow down
all other TIEs. Ignored when received from southbound
neighbor. */
23: optional bool you_are_sending_too_quickly =
false;
/** Instance name in case multiple RIFT instances running on same
interface. */
24: optional string instance_name;
/** It provides the optional ID of the Fabric fabric configured. This
MUST match the information advertised on the node element. */
35: optional common.FabricIDType fabric_id =
common.default_fabric_id;
}
/** LinkID pair describes one of parallel links between two nodes. */
struct LinkIDPair {
/** Node-wide unique value for the local link. */
1: required common.LinkIDType local_id;
/** Received remote link ID for this link. */
2: required common.LinkIDType remote_id;
/** Describes the local interface index of the link. */
10: optional common.PlatformInterfaceIndex
platform_interface_index;
/** Describes the local interface name. */
11: optional string platform_interface_name;
/** Indicates whether the link is secured, i.e. i.e., protected by
outer key, absence of this element means no indication,
undefined outer key means not secured. */
12: optional common.OuterSecurityKeyID
trusted_outer_security_key;
/** Indicates whether the link is protected by established
BFD session. */
13: optional bool bfd_up;
/** Optional indication which address families are up on the
interface */
14: optional set<common.AddressFamilyType>
address_families;
}
/** Unique ID of a TIE. */
struct TIEID {
/** direction of TIE */
1: required common.TieDirectionType direction;
/** indicates originator of the TIE */
2: required common.SystemIDType originator;
/** type of the tie */
3: required common.TIETypeType tietype;
/** number of the tie */
4: required common.TIENrType tie_nr;
}
/** Header of a TIE. */
struct TIEHeader {
/** ID of the tie. */
2: required TIEID tieid;
/** Sequence number of the tie. */
3: required common.SeqNrType seq_nr;
/** Absolute timestamp when the TIE was generated. */
10: optional common.IEEE802_1ASTimeStampType origination_time;
/** Original lifetime when the TIE was generated. */
12: optional common.LifeTimeInSecType origination_lifetime;
}
/** Header of a TIE as described in TIRE/TIDE.
*/
struct TIEHeaderWithLifeTime {
1: required TIEHeader header;
/** Remaining lifetime. */
2: required common.LifeTimeInSecType remaining_lifetime;
}
/** TIDE with *sorted* TIE headers. */
struct TIDEPacket {
/** First TIE header in the tide TIDE packet. */
1: required TIEID start_range;
/** Last TIE header in the tide TIDE packet. */
2: required TIEID end_range;
/** _Sorted_ list of headers. */
3: required list<TIEHeaderWithLifeTime>
headers;
}
/** TIRE packet */
struct TIREPacket {
1: required set<TIEHeaderWithLifeTime>
headers;
}
/** neighbor of a node */
struct NodeNeighborsTIEElement {
/** level of neighbor */
1: required common.LevelType level;
/** Cost to neighbor. Ignore anything equal/larger than `infinite_distance`
'infinite_distance' or equal `invalid_distance` 'invalid_distance' */
3: optional common.MetricType cost
= common.default_distance;
/** can carry description of multiple parallel links in a TIE */
4: optional set<LinkIDPair>
link_ids;
/** total bandwith bandwidth to neighbor as sum of all parallel links */
5: optional common.BandwithInMegaBitsType common.BandwidthInMegaBitsType
bandwidth = common.default_bandwidth;
}
/** Indication flags of the node. */
struct NodeFlags {
/** Indicates that node is in overload, do not transit traffic
through it. */
1: optional bool overload = common.overload_default;
}
/** Description of a node. */
struct NodeTIEElement {
/** Level of the node. */
1: required common.LevelType level;
/** Node's neighbors. Multiple node TIEs can carry disjoint sets
of neighbors. */
2: required map<common.SystemIDType,
NodeNeighborsTIEElement> neighbors;
/** Capabilities of the node. */
3: required NodeCapabilities capabilities;
/** Flags of the node. */
4: optional NodeFlags flags;
/** Optional node name for easier operations. */
5: optional string name;
/** PoD to which the node belongs. */
6: optional common.PodType pod;
/** optional Optional startup time of the node */
7: optional common.TimestampInSecsType startup_time;
/** If any local links are miscabled, this indication is
flooded. */
10: optional set<common.LinkIDType>
miscabled_links;
/** ToFs in the same plane. Only carried by ToF. Multiple Node
TIEs can carry disjoint sets of ToFs
which that MUST be joined to
form a single set. */
12: optional set<common.SystemIDType>
same_plane_tofs;
/** It provides the optional ID of the Fabric fabric configured */
20: optional common.FabricIDType fabric_id =
common.default_fabric_id;
}
/** Attributes of a prefix. */
struct PrefixAttributes {
/** Distance of the prefix. */
2: required common.MetricType metric
= common.default_distance;
/** Generic unordered set of route tags, can be redistributed
to other protocols or use used within the context of real time
analytics. */
3: optional set<common.RouteTagType>
tags;
/** Monotonic clock for mobile addresses. */
4: optional common.PrefixSequenceType monotonic_clock;
/** Indicates if the prefix is a node loopback. */
6: optional bool loopback = false;
/** Indicates that the prefix is directly attached. */
7: optional bool directly_attached = true;
/** link Link to which the address belongs to. */
10: optional common.LinkIDType from_link;
/** Optional, per prefix per-prefix significant label. */
12: optional common.LabelType label;
}
/** TIE carrying prefixes */
struct PrefixTIEElement {
/** Prefixes with the associated attributes. */
1: required map<common.IPPrefixType, PrefixAttributes> prefixes;
}
/** Defines the targeted nodes and the value carried. */
struct KeyValueTIEElementContent {
1: optional common.KeyValueTargetType targets =
common.keyvaluetarget_default;
2: optional binary value;
}
/** Generic key value pairs. */
struct KeyValueTIEElement {
1: required map<common.KeyIDType, KeyValueTIEElementContent>
keyvalues;
}
/** Single element in a TIE. */
union TIEElement {
/** Used in case of enum common.TIETypeType.NodeTIEType. */
1: optional NodeTIEElement node;
/** Used in case of enum common.TIETypeType.PrefixTIEType. */
2: optional PrefixTIEElement prefixes;
/** Positive prefixes (always southbound). */
3: optional PrefixTIEElement positive_disaggregation_prefixes;
/** Transitive, negative prefixes (always southbound) */
5: optional PrefixTIEElement negative_disaggregation_prefixes;
/** Externally reimported prefixes. */
6: optional PrefixTIEElement external_prefixes;
/** Positive external disaggregated prefixes (always
southbound). */
7: optional PrefixTIEElement
positive_external_disaggregation_prefixes;
/** Key-Value store elements. */
9: optional KeyValueTIEElement keyvalues;
}
/** TIE packet */
struct TIEPacket {
1: required TIEHeader header;
2: required TIEElement element;
}
/** Content of a RIFT packet. */
union PacketContent {
1: optional LIEPacket lie;
2: optional TIDEPacket tide;
3: optional TIREPacket tire;
4: optional TIEPacket tie;
}
/** RIFT packet structure. */
struct ProtocolPacket {
1: required PacketHeader header;
2: required PacketContent content;
}
8. Further Details on Implementation
8.1. Considerations for Leaf-Only Implementation
RIFT can and is intended to be stretched to the lowest level in the
IP fabric to integrate ToRs or even servers. Since those entities
would run as leaves only, it is worth it to observe that a leaf only leaf-only
version is significantly simpler to implement and requires much less
resources:
1. Leaf nodes only need to maintain a multipath default route under
normal circumstances. However, in cases of catastrophic
partitioning, leaf nodes SHOULD be capable of accommodating all
the leaf routes in their own PoD to prevent traffic loss.
2. Leaf nodes hold only hold their own North TIEs and the South TIEs of
Level
level 1 nodes they are connected to.
3. Leaf nodes do not have to support any type of disaggregation
computation or propagation.
4. Leaf nodes are not required to support the overload flag.
5. Leaf nodes do not need to originate S-TIEs unless optional leaf-
2-leaf
to-leaf features are desired.
8.2. Considerations for Spine Implementation
Nodes that do not act as ToF are not required to discover fallen
leaves by comparing reachable destinations with peers and therefore
do not need to run the computation of disaggregated routes based on
that discovery. On the other hand, non-ToF nodes need to respect
disaggregated routes advertised from the north. In the case of
negative disaggregation, spines nodes need to generate southbound
disaggregated routes when all parents are lost for a fallen leaf.
9. Security Considerations
9.1. General
One can consider attack vectors where a router may reboot many times
while changing its System ID and pollute the network with many stale
TIEs or TIEs that are sent with very long lifetimes and not cleaned
up when the routes vanish. Those attack vectors are not unique to
RIFT. Given large memory footprints available today today, those attacks
should be relatively benign. Otherwise, a node SHOULD implement a
strategy of discarding contents of all TIEs that were not present in
the SPF tree over a certain, configurable period of time. Since the
protocol is self-stabilizing and will advertise the presence of such
TIEs to its neighbors, they can be re-requested again if a
computation finds that it has an adjacency formed towards the System
ID of the discarded TIEs.
The inner protection configured based on any of the mechanisms in
Section 10.2 guarantees the integrity of TIE content content, and when
combined with the outer part of the envelope envelope, using any of the
mechanisms in Section 10.2 10.2, guarantees protection against replay
attacks as well. If only outer protection (i.e., an outer key ID
different from
`undefined_securitykey_id`) 'undefined_securitykey_id') is applied to an adjacency
by the means of any mechanism in Section 10.2 10.2, the integrity of the
packet and replay protection is guaranteed only over the adjacency
involved in any of the configured directions. Further considerations
can be found in Section Sections 9.7 and Section 9.8.
9.2. Time to Live and Hop Limit Values
RIFT explicitly requires the use of a TTL/HL value of 1 *or* 255 when
sending/receiving LIEs and TIEs so that implementors have a choice
between the two.
Using a TTL/HL value of 255 does come with security concerns, but
those risks are addressed in [RFC5082]. However, this approach may
still have difficulties with some forwarding implementations (e.g. (e.g.,
incorrectly processing TTL/HL, loops within the forwarding plane
itself, etc.).
It is for this reason that RIFT also allows implementations to use a
TTL/HL of 1. Attacks that exploit this by spoofing it from several
hops away are indeed possible, possible but are exceptionally difficult to
engineer. Replay attacks are another potential attack vector, but as
described in the subsequent security sections, RIFT is well protected
against such attacks if any of the mechanisms in Section 10.2 is are
applied. Additionally, for link-local scoped multicast addresses
used for LIE LIE, the value of 1 presents a more consistent choice.
9.3. Malformed Packets
The protocol protects packets extensively through optional signatures
and nonces nonces, so if the possibility of maliciously injected malformed
or replayed packets exist in a deployment deployment, algorithms in Section 10.2
must be applied.
Even with the security envelope, since RIFT relies on Thrift encoders
and decoders generated automatically from IDL IDL, it is conceivable that
errors in such encoders/decoders could be discovered and lead to
delivery of corrupted packets or reception of packets that cannot be
decoded. Misformatted packets lead normally lead to the decoder returning
an error condition to the caller caller, and with that that, the packet is
basically unparsable with no other choice but to discard it. Should
the unlikely scenario occur of the decoder being forced to abort the
protocol
protocol, this is neither better nor worse than today's behavior of
other protocols.
9.4. RIFT ZTP
Section 6.7 presents many attack vectors in untrusted environments,
starting with nodes that oscillate their level offers to the
possibility of nodes offering a _ThreeWay_ adjacency with the highest
possible level value and a very long holdtime trying to put itself
"on top of the lattice" lattice", thereby allowing it to gain access to the
whole southbound topology. Session authentication mechanisms are
necessary in environments where this is possible possible, and RIFT provides
the security envelope to ensure this this, if so desired desired, if any mechanism
in Section 10.2 is deployed.
9.5. Lifetime
RIFT removes lifetime modification and replay attack vectors by
protecting the lifetime behind a signature computed over it and
additional nonce combination combination, which results in the inability of an
attacker to artificially shorten the _remaining_lifetime_. This only
applies if any mechanism in Section 10.2 is used.
9.6. Packet Number
An
A packet number is an optional defined value number that is carried
in the security envelope without any fingerprint protection and is
hence vulnerable to replay and modification attacks. Contrary to
nonces, this number must change on every packet and would present a
very high cryptographic load if signed. The attack vector packet
number present is relatively benign. Changing the packet number by a man-
in-the-middle
man-in-the-middle attack will only affect operational validation
tools and possibly some performance optimizations on flooding. It is
expected that an implementation detecting too many "fake losses" or
"misorderings" due to the attack on the packet number would simply
suppress its further processing.
9.7. Outer Fingerprint Attacks
Even when a mechanism in Section 10.2 is enabled to generate outer
fingerprints
fingerprints, further attack considerations apply.
A node can try to inject LIE packets observing a conversation on the
wire by using the observed outer Key ID key ID, albeit it cannot generate
valid signatures in case it changes the integrity of the message message, so
the only possible attack is DoS due to excessive LIE validation if
any mechanism in Section 10.2 is used.
A node can try to replay previous LIEs with a changed state that it
recorded
recorded, but the attack is hard to replicate since the nonce
combination must match the ongoing exchange and is then limited to
only a single flap only since both nodes will advance their nonces in case
the adjacency state changed. Even in the most unlikely case case, the
attack length is limited due to both sides periodically increasing
their nonces.
Generally, since weak nonces are not changed on every packet for
performance reasons reasons, a conceivable attack vector by a man-in-the- man in the
middle is to flood a receiving node with the maximum bandwidth of
recently observed packets, both LIEs as well as TIEs. In a scenario
where such attacks are likely likely, _maximum_valid_nonce_delta_ can be
implemented as configurable, small value and
_nonce_regeneration_interval_ configured to very small value as well.
This will likely present a significant computational load on large
fabrics under normal operation.
9.8. TIE Origin Fingerprint DoS Attacks
Even when a mechanism in Section 10.2 is enabled to generate inner
fingerprints or signatures signatures, further attack considerations apply.
In case the inner fingerprint could be generated by a compromised
node in the network other than the originator based on shared secrets
secrets, the deployment must fall back on use of signatures that can
be validated but not generated by any other node but except the
originator.
A compromised node in the network can attempt to brute force "fake
TIEs" using other nodes' TIE origin key identifiers without
possessing the necessary secrets. Albeit the ultimate validation of
the origin signature will fail in such scenarios and not progress
further than immediately peering nodes, the resulting denial of
service DoS attack
seems unavoidable since the TIE origin Key key ID is only protected by
the (here assumed to be compromised) node.
9.9. Host Implementations
It can be reasonably expected that with the proliferation of RotH servers,
rather than dedicated networking devices, will represent a
significant amount of RIFT devices. Given their normally far wider
software envelope and access granted to them, such servers are also
far more likely to be compromised and present an attack vector on the
protocol. Hijacking of prefixes to attract traffic is a trust
problem and cannot be easily addressed within the protocol if the
trust model is breached, i.e. i.e., the server presents valid credentials
to form an adjacency and issue TIEs. In an even more devious way,
the servers can present DoS (or even DDoS) vectors of from issuing too
many LIE packets, flooding large amounts of North TIEs, and
attempting similar resource overrun attacks. A prudent
implementation forming adjacencies to leaves should implement
thresholds
threshold mechanisms and raise warnings when, e.g., a leaf is
advertising an excess number of TIEs or prefixes. Additionally, such
implementation could refuse any topology information except the
node's own TIEs and authenticated, reflected South Node TIEs at their
own level.
To isolate possible attack vectors on the leaf to the largest
possible extent extent, a dedicated leaf-only implementation could run
without any configuration by hard-coding a well-known adjacency key
(which can be always rolled-over rolled over by the means of, e.g., a well-known
key-value
key value distributed from the top of the fabric), leaf level value
and always setting overload flag. All other values can be derived by
automatic means as described above.
9.9.1. IPv4 Broadcast and IPv6 All Routers All-Routers Multicast Implementations
Section 6.2 describes an optional implementation that supports LIE
exchange over IPv4 broadcast addresses and/or the IPv6 all routers all-routers
multicast address. It is important to consider that if an
implementation supports this, the attack surface widens as LIEs may
be propagated to devices outside of the intended RIFT topology. This
may leave RIFT nodes more susceptible to the various attack vectors
already described in this section.
10. IANA Considerations
This specification requests
As detailed below, multicast address assignments addresses and standard port numbers. numbers have
been assigned. Additionally, registries for the schema are
requested and suggested have been
created with initial values provided that reflect the numbers
allocated in the given schema. assigned.
10.1. Requested Multicast and Port Numbers
This document requests allocation in
In the 'IPv4 "IPv4 Multicast Address
Space' registry Space" registry, the suggested value of
224.0.0.121 as
'ALL_V4_RIFT_ROUTERS' and in has been assigned for 'ALL_V4_RIFT_ROUTERS'. In the 'IPv6
"IPv6 Multicast Address Space'
registry Space" registry, the suggested value of ff02::a1f7 as has
been assigned for 'ALL_V6_RIFT_ROUTERS'.
This document requests the
The following allocations from assignments have been made in the "Service Name and
Transport Protocol Port Number Registry":
_RIFT LIE Port_
Service Name: rift-lies
Port Number: 914
Transport Protocol(s): UDP
Assignee: Tony Przygienda (prz@juniper.net)
Contact: Jordan Head (jhead@juniper.net) Protocol: udp
Description: Routing in Fat Trees Link Information Element
Assignee: IESG (iesg@ietf.org)
Contact: IETF Chair (chair@ietf.org)
Reference: This Document
Port Number: 914 RFC 9692
_RIFT TIE Port_
Service Name: rift-ties
Port Number: 915
Transport Protocol(s): UDP Protocol: udp
Assignee: Tony Przygienda (prz@juniper.net) IESG (iesg@ietf.org)
Contact: Jordan Head (jhead@juniper.net) IETF Chair (chair@ietf.org)
Description: Routing in Fat Trees Topology Information Element
Reference: This Document
Port Number: 915 RFC 9692
10.2. Requested Registry for RIFT Security Algorithms
This section requests generation of a
A new registry holding has been created to hold the allowed RIFT Security Algorithms. security
algorithms. No particular enumeration values are necessary since
RIFT uses a key ID abstraction on packets without disclosing any
information about the algorithm or secrets used and only carries the
resulting fingerprint or signature protecting the integrity of the
data.
The registry applies the "Specification Required" policy per
[RFC5226].
[RFC8126]. The designated expert should ensure that the algorithms
suggested represent the state of the art at a given point in time and
avoid introducing algorithms which that do not represent enhanced security
properties or ensure such properties at a lower cost as compared to
existing registry entries.
+==========================+===========+==========================+
+==========================+============+==========================+
| Name | Reference | Recommendation |
+==========================+===========+==========================+
+==========================+============+==========================+
| HMAC-SHA256 | [SHA-2] | Simplest way to ensure |
| | and | integrity of |
| | [RFC2104] | transmissions across |
| | | adjacencies when used as |
| | | outer key and integrity |
| | | of TIEs when used as |
| | | inner keys. Recommended |
| | | for most interoperable |
| | | security protection. |
+--------------------------+-----------+--------------------------+
+--------------------------+------------+--------------------------+
| HMAC-SHA512 | [SHA-2] | Same as HMAC-SHA256 with |
| | and | stronger protection. |
| | [RFC2104] | |
+--------------------------+-----------+--------------------------+
+--------------------------+------------+--------------------------+
| SHA256-RSASSA-PKCS1-v1_5 | [RFC8017] [RFC8017], | Recommended for high |
| | Section | security applications |
| | 8.2 | where private keys are |
| | | protected by according |
| | | nodes. Recommended as |
| | | well in case not only |
| | | integrity but origin |
| | | validation is necessary |
| | | for TIEs. Recommended |
| | | when adjacencies must be |
| | | protected without |
| | | disclosing the secrets |
| | | on both sides of the |
| | | adjacency. |
+--------------------------+-----------+--------------------------+
+--------------------------+------------+--------------------------+
| SHA512-RSASSA-PKCS1-v1_5 | [RFC8017] | Same as SHA256-RSASSA- |
| | | PKCS1-v1_5 with stronger |
| | | protection. |
+--------------------------+-----------+--------------------------+
+--------------------------+------------+--------------------------+
Table 7
10.3. Requested Registries with Assigned Values for Schema Values
This section requests registries that help govern the schema via the
usual IANA registry procedures. A top-level The registry group named 'RIFT'
should hold the corresponding registries requested "Routing in Fat
Trees (RIFT)" holds the following
sections with their pre-defined values. registries. Registry values are
stored with their minimum and maximum version in which they are
available. All values not provided as are to be considered `Unassigned`.
"Unassigned". The range of every registry is a 16-bit integer.
Allocation of new values is performed via `Expert Review` "Expert Review" action only
in the case of major or minor Change changes per the rules in Section 7. Any All other allocation is
allocations are performed via
'Specification Required'.
The "Specification Required".
In some cases, the registries do not contain in some cases necessary information
such as whether the fields are optional or required, what units are
used
used, or what datatype is involved. This information is encoded in
the normative schema itself by the means of IDL syntax or necessary
type definitions and their names.
10.3.1. RIFTVersions Registry RIFT/Versions
This registry stores all RIFT protocol schema major and minor
versions
versions, including the reference to the document introducing the
version. This also means as well that that, if multiple documents extend rift
schema
schema, they have to serialize using this registry to increase the
minor or major versions sequentially.
+================+===================================+
+================+=====================+
| Schema Version | Reference |
+================+===================================+
+================+=====================+
| 8.0 | https://datatracker.ietf.org/doc/ |
| | draft-ietf-rift-rift/ RFC 9692, Section 7 |
+----------------+-----------------------------------+
+----------------+---------------------+
Table 8
10.3.2. RIFTCommonAddressFamilyType Registry RIFT/common/AddressFamilyType
The name of the
This registry should be RIFTCommonAddressFamilyType.
Address family type.
+=======================+=======+=============+=========+=========+
| Name has the following initial values.
+=======+=======================+=============+=========+=========+
| Value | Name | Min. Schema | Max. | Comment |
| | | Version | Schema | |
| | | | Version | |
+=======================+=======+=============+=========+=========+
| Illegal
+=======+=======================+=============+=========+=========+
| 0 | 8.0 Illegal | 8.0 | |
+-----------------------+-------+-------------+---------+---------+ | AddressFamilyMinValue
+-------+-----------------------+-------------+---------+---------+
| 1 | 8.0 AddressFamilyMinValue | 8.0 | |
+-----------------------+-------+-------------+---------+---------+ | IPv4
+-------+-----------------------+-------------+---------+---------+
| 2 | 8.0 IPv4 | 8.0 | |
+-----------------------+-------+-------------+---------+---------+ | IPv6
+-------+-----------------------+-------------+---------+---------+
| 3 | 8.0 IPv6 | 8.0 | |
+-----------------------+-------+-------------+---------+---------+ | AddressFamilyMaxValue
+-------+-----------------------+-------------+---------+---------+
| 4 | AddressFamilyMaxValue | 8.0 | | |
+-----------------------+-------+-------------+---------+---------+
+-------+-----------------------+-------------+---------+---------+
Table 9 9: Address Family Type
10.3.3. RIFTCommonHierarchyIndications Registry RIFT/common/HierarchyIndications
The name of the
This registry should be RIFTCommonHierarchyIndications.
Flags indicating node configuration in case of ZTP. has the following initial values.
+====================================+=====+=======+=======+=======+
|Name |Value| Min.| Max.|Comment| |Value|Min. |Max. |Comment|
| | |Schema |Schema | Schema| Schema| |
| | |Version|Version| |
+====================================+=====+=======+=======+=======+
|leaf_only |0 |8.0 | 0| 8.0| | |
+------------------------------------+-----+-------+-------+-------+
|leaf_only_and_leaf_2_leaf_procedures| 1| 8.0|
|leaf_only_and_leaf_2_leaf_procedures|1 |8.0 | | |
+------------------------------------+-----+-------+-------+-------+
|top_of_fabric |2 |8.0 | 2| 8.0| | |
+------------------------------------+-----+-------+-------+-------+
Table 10 10: Flags Indicating Node Configuration in Case of ZTP
10.3.4. RIFTCommonIEEE8021ASTimeStampType Registry RIFT/common/IEEE802_1ASTimeStampType
The name of the
This registry should be RIFTCommonIEEE8021ASTimeStampType.
Timestamp has the following initial values.
The timestamp is per IEEE 802.1AS, 802.1AS; all values MUST be interpreted in
implementation as unsigned.
+==========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+==========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------------------+-------------+---------+
| AS_sec | 1 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
| AS_nsec | 2 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
Table 11
10.3.5. RIFTCommonIPAddressType Registry RIFT/common/IPAddressType
The name of the
This registry should be RIFTCommonIPAddressType.
IP address type. has the following initial values.
+=============+=======+=====================+=============+=========+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+=============+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-------------+-------+---------------------+-------------+---------+
| ipv4address | 1 | 8.0 | | Content |
| | | | | is ipv4 IPv4 |
+-------------+-------+---------------------+-------------+---------+
| ipv6address | 2 | 8.0 | | Content |
| | | | | is ipv6 IPv6 |
+-------------+-------+---------------------+-------------+---------+
Table 12 12: IP Address Type
10.3.6. RIFTCommonIPPrefixType Registry RIFT/common/IPPrefixType
The name of the
This registry should be RIFTCommonIPPrefixType.
Prefix advertisement.
@note: for has the following initial values.
Note: For interface addresses addresses, the protocol can propagate the address
part beyond the subnet mask and on reachability computation that has
to be normalized. The non-significant bits can be used for
operational purposes.
+============+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+============+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+------------+-------+---------------------+-------------+---------+
| ipv4prefix | 1 | 8.0 | | |
+------------+-------+---------------------+-------------+---------+
| ipv6prefix | 2 | 8.0 | | |
+------------+-------+---------------------+-------------+---------+
Table 13 13: Prefix Advertisement
10.3.7. RIFTCommonIPv4PrefixType Registry RIFT/common/IPv4PrefixType
The name of the
This registry should be RIFTCommonIPv4PrefixType.
IPv4 prefix type. has the following initial values.
+===========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+===========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-----------+-------+---------------------+-------------+---------+
| address | 1 | 8.0 | | |
+-----------+-------+---------------------+-------------+---------+
| prefixlen | 2 | 8.0 | | |
+-----------+-------+---------------------+-------------+---------+
Table 14 14: IPv4 Prefix Type
10.3.8. RIFTCommonIPv6PrefixType Registry RIFT/common/IPv6PrefixType
The name of the
This registry should be RIFTCommonIPv6PrefixType.
IPv6 prefix type. has the following initial values.
+===========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+===========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-----------+-------+---------------------+-------------+---------+
| address | 1 | 8.0 | | |
+-----------+-------+---------------------+-------------+---------+
| prefixlen | 2 | 8.0 | | |
+-----------+-------+---------------------+-------------+---------+
Table 15 15: IPv6 Prefix Type
10.3.9. RIFTCommonKVTypes Registry RIFT/common/KVTypes
The name of the
This registry should be RIFTCommonKVTypes. has the following initial values.
+==============+=======+=============+=============+=========+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+==============+=======+=============+=============+=========+
| Unassigned | 0 | | | |
+--------------+-------+-------------+-------------+---------+
| Experimental | 1 | 8.0 | | |
+--------------+-------+-------------+-------------+---------+
| WellKnown | 2 | 8.0 | | |
+--------------+-------+-------------+-------------+---------+
| OUI | 3 | 8.0 | | |
+--------------+-------+-------------+-------------+---------+
Table 16
10.3.10. RIFTCommonPrefixSequenceType Registry RIFT/common/PrefixSequenceType
The name of the
This registry should be RIFTCommonPrefixSequenceType.
Sequence of a prefix in case of move.
+===============+=======+=============+==========+==================+ has the following initial values.
+===============+=======+=========+==========+===================+
| Name | Value | Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+===============+=======+=============+==========+==================+
+===============+=======+=========+==========+===================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+---------------+-------+-------------+----------+------------------+
+---------------+-------+---------+----------+-------------------+
| timestamp | 1 | 8.0 | | |
+---------------+-------+-------------+----------+------------------+
+---------------+-------+---------+----------+-------------------+
| transactionid | 2 | 8.0 | | Transaction id ID |
| | | | | set by client in in, |
| | | | | e.g. in 6lowpan. e.g., 6LoWPAN. |
+---------------+-------+-------------+----------+------------------+
+---------------+-------+---------+----------+-------------------+
Table 17 17: Sequence of a Prefix in Case of Move
10.3.11. RIFTCommonRouteType Registry RIFT/common/RouteType
The name of the
This registry should be RIFTCommonRouteType.
RIFT route types. @note: has the following initial values.
Note: The only purpose of those these values is to introduce an ordering ordering,
whereas an implementation can choose internally choose any other values as
long the ordering is preserved preserved.
+=====================+=======+=============+=============+=========+
| Name | Value | Min. Schema | Max. | Comment |
| | | Version | Schema | |
| | | | Version | |
+=====================+=======+=============+=============+=========+
| Illegal | 0 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| RouteTypeMinValue | 1 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| Discard | 2 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| LocalPrefix | 3 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| SouthPGPPrefix | 4 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| NorthPGPPrefix | 5 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| NorthPrefix | 6 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| NorthExternalPrefix | 7 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| SouthPrefix | 8 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| SouthExternalPrefix | 9 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| NegativeSouthPrefix | 10 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
| RouteTypeMaxValue | 11 | 8.0 | | |
+---------------------+-------+-------------+-------------+---------+
Table 18 18: RIFT Route Types
10.3.12. RIFTCommonTIETypeType Registry RIFT/common/TIETypeType
The name of the
This registry should be RIFTCommonTIETypeType.
Type of TIE.
+===========================================+=====+=======+=======+=======+ has the following initial values.
+===================================+=====+=======+=======+=======+
|Name |Value| Min.| Max.|Comment| |Value|Min. |Max. |Comment|
| | |Schema |Schema | Schema| Schema| |
| | |Version|Version| |
+===========================================+=====+=======+=======+=======+
+===================================+=====+=======+=======+=======+
|Illegal |0 |8.0 | 0| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
+-----------------------------------+-----+-------+-------+-------+
|TIETypeMinValue |1 |8.0 | 1| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
+-----------------------------------+-----+-------+-------+-------+
|NodeTIEType |2 |8.0 | 2| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
+-----------------------------------+-----+-------+-------+-------+
|PrefixTIEType |3 |8.0 | 3| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
|PositiveDisaggregationPrefixTIEType
+-----------------------------------+-----+-------+-------+-------+
|PositiveDisaggregationPrefixTIEType|4 |8.0 | 4| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
|NegativeDisaggregationPrefixTIEType
+-----------------------------------+-----+-------+-------+-------+
|NegativeDisaggregationPrefixTIEType|5 |8.0 | 5| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
+-----------------------------------+-----+-------+-------+-------+
|PGPrefixTIEType |6 |8.0 | 6| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
+-----------------------------------+-----+-------+-------+-------+
|KeyValueTIEType |7 |8.0 | 7| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
+-----------------------------------+-----+-------+-------+-------+
|ExternalPrefixTIEType |8 |8.0 | | 8| 8.0| |
+-----------------------------------+-----+-------+-------+-------+
|PositiveExternalDisaggregation |9 |8.0 |
+-------------------------------------------+-----+-------+-------+-------+
|PositiveExternalDisaggregationPrefixTIEType| 9| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
|PrefixTIEType | | | | |
+-----------------------------------+-----+-------+-------+-------+
|TIETypeMaxValue |10 |8.0 | 10| 8.0| | |
+-------------------------------------------+-----+-------+-------+-------+
+-----------------------------------+-----+-------+-------+-------+
Table 19 19: Type of TIE
10.3.13. RIFTCommonTieDirectionType Registry RIFT/common/TieDirectionType
The name of the
This registry should be RIFTCommonTieDirectionType.
Direction of TIEs. has the following initial values.
+===================+=======+=============+=============+=========+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+===================+=======+=============+=============+=========+
| Illegal | 0 | 8.0 | | |
+-------------------+-------+-------------+-------------+---------+
| South | 1 | 8.0 | | |
+-------------------+-------+-------------+-------------+---------+
| North | 2 | 8.0 | | |
+-------------------+-------+-------------+-------------+---------+
| DirectionMaxValue | 3 | 8.0 | | |
+-------------------+-------+-------------+-------------+---------+
Table 20 20: Direction of TIEs
10.3.14. RIFTEncodingCommunity Registry RIFT/encoding/Community
The name of the
This registry should be RIFTEncodingCommunity.
Prefix community. has the following initial values.
+==========+=======+=====================+=============+============+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+==========+=======+=====================+=============+============+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------------------+-------------+------------+
| top | 1 | 8.0 | | Higher |
| | | | | order bits |
+----------+-------+---------------------+-------------+------------+
| bottom | 2 | 8.0 | | Lower |
| | | | | order bits |
+----------+-------+---------------------+-------------+------------+
Table 21 21: Prefix Community
10.3.15. RIFTEncodingKeyValueTIEElement Registry RIFT/encoding/KeyValueTIEElement
The name of the
This registry should be RIFTEncodingKeyValueTIEElement.
Generic key value pairs. has the following initial values.
+===========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+===========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-----------+-------+---------------------+-------------+---------+
| keyvalues | 1 | 8.0 | | |
+-----------+-------+---------------------+-------------+---------+
Table 22 22: Generic Key Value Pairs
10.3.16. RIFTEncodingKeyValueTIEElementContent Registry RIFT/encoding/KeyValueTIEElementContent
The name of the
This registry should be
RIFTEncodingKeyValueTIEElementContent.
Defines has the following initial values. It defines the
targeted nodes and the value carried.
+==========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+==========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------------------+-------------+---------+
| targets | 1 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
| value | 2 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
Table 23
10.3.17. RIFTEncodingLIEPacket Registry RIFT/encoding/LIEPacket
The name of the
This registry should be RIFTEncodingLIEPacket.
RIFT LIE Packet.
@note: this has the following initial values.
Note: This node's level is already included on the packet header
+=============================+=====+=======+========+=============+ header.
+=============================+=====+=======+========+==============+
| Name |Value| Min.| Max.|Comment |Value|Min. |Max. |Comment |
| | |Schema |Schema | | Schema| Schema|
| | |Version|Version | |Version| Version| |
+=============================+=====+=======+========+=============+
+=============================+=====+=======+========+==============+
| Reserved |0 |8.0 |All | 0| 8.0| All| |
| | | |Versions| |
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| name |1 |8.0 | 1| 8.0| |Node or | Node or|
| | | | |adjacency | adjacency|
| | | | |name. | name.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| local_id |2 |8.0 | 2| 8.0| |Local link | Local link|
| | | | |ID. | id.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| flood_port |3 |8.0 | 3| 8.0| | Udp |UDP port to| to |
| | | | which |which we can| can |
| | | | |receive | receive|
| | | | |flooded ties.|
+-----------------------------+-----+-------+--------+-------------+ ties. | link_mtu_size
+-----------------------------+-----+-------+--------+--------------+
| 4| 8.0| link_mtu_size |4 |8.0 | Layer |Layer 2 mtu,| MTU, |
| | | | used to| |used to |
| | | | |discover | discover|
| | | | |mismatch. | mismatch.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| link_bandwidth |5 |8.0 | 5| 8.0| |Local link | Local link|
| | | | |bandwidth on | bandwidth on|
| | | | |the | the|
| | | | |interface. | interface.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| neighbor |6 |8.0 | 6| 8.0| |Reflects the | Reflects the|
| | | | |neighbor once| once |
| | | | received to| |received to |
| | | | |provide 3-way| 3-way |
| | | | |connectivity.|
+-----------------------------+-----+-------+--------+-------------+ |connectivity. |
+-----------------------------+-----+-------+--------+--------------+
| pod |7 |8.0 | 7| 8.0| |Node's PoD. | Node's pod.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| node_capabilities |10 |8.0 | 10| 8.0| |Node | Node|
| | | | |capabilities | capabilities|
| | | | |supported. | supported.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| link_capabilities |11 |8.0 | 11| 8.0| |Capabilities | Capabilities|
| | | | |of this link.|
+-----------------------------+-----+-------+--------+-------------+ link. | holdtime
+-----------------------------+-----+-------+--------+--------------+
| 12| 8.0| holdtime |12 |8.0 | Required| |Required |
| | | | holdtime of| |holdtime of |
| | | | the| |the |
| | | | adjacency,| |adjacency, |
| | | | i.e. |i.e., for how| how |
| | | | |long a period| period |
| | | | should| |adjacency |
| | | | adjacency be| |should be |
| | | | kept up| |kept up |
| | | | |without valid| valid |
| | | | lie| |LIE |
| | | | reception.|
+-----------------------------+-----+-------+--------+-------------+ |reception. |
+-----------------------------+-----+-------+--------+--------------+
| label |13 |8.0 | 13| 8.0| |Optional, | Optional,|
| | | | |unsolicited, | unsolicited,|
| | | | |downstream | downstream|
| | | | |assigned | assigned|
| | | | |locally | locally|
| | | | |significant | significant|
| | | | |label value | label value|
| | | | |for the | for the|
| | | | |adjacency. | adjacency.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| not_a_ztp_offer |21 |8.0 | 21| 8.0| | Indicates| |Indicates |
| | | | that the| |that the |
| | | | level |level on the| the |
| | | | lie |lie must not| not |
| | | | be |be used to| to |
| | | | derive |derive a ztp| ZTP |
| | | | level |level by the| the |
| | | | |receiving | receiving|
| | | | |node. | node.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
| you_are_flood_repeater |22 |8.0 | |Indicates to |
| 22| 8.0| | Indicates to| | | |the |
| | northbound| | | |northbound |
| | | | |neighbor that| that |
| | | | it |it should be| be |
| | | | reflooding| |reflooding |
| | | | |ties received| received |
| | | | from this| |from this |
| | | | node to| |node to |
| | | | |achieve flood| flood |
| | | | |reduction and| and |
| | | | |balancing for| for |
| | | | northbound| |northbound |
| | | | flooding.|
+-----------------------------+-----+-------+--------+-------------+ |flooding. | you_are_sending_too_quickly
+-----------------------------+-----+-------+--------+--------------+
| 23| 8.0| you_are_sending_too_quickly |23 |8.0 | Indicates to| |Indicates to |
| | | | |the neighbor to| |
| | | | |to flood node| node |
| | | | |ties only and| and |
| | | | |slow down all| all |
| | | | other ties.| |other ties. |
| | | | ignored when| |Ignored when |
| | | | |received from| from |
| | | | |the |
| | | | southbound| |southbound |
| | | | neighbor.|
+-----------------------------+-----+-------+--------+-------------+ |neighbor. |
+-----------------------------+-----+-------+--------+--------------+
| instance_name |24 |8.0 | 24| 8.0| |Instance name| name |
| | | | in case| |in case |
| | | | |multiple rift| rift |
| | | | instances| |instances |
| | | | running on| |running on |
| | | | same| |same |
| | | | interface.|
+-----------------------------+-----+-------+--------+-------------+ |interface. | fabric_id
+-----------------------------+-----+-------+--------+--------------+
| 35| 8.0| fabric_id |35 |8.0 | It provides| |It provides |
| | | | the optional| |the optional |
| | | | id |ID of the| the |
| | | | fabric| |fabric |
| | | | configured.| |configured. |
| | | | this must| |This must |
| | | | match the| |match the |
| | | | |information | information|
| | | | |advertised on| on |
| | | | the node| |the node |
| | | | |element. | element.|
+-----------------------------+-----+-------+--------+-------------+
+-----------------------------+-----+-------+--------+--------------+
Table 24 24: RIFT LIE Packet
10.3.18. RIFTEncodingLinkCapabilities Registry RIFT/encoding/LinkCapabilities
The name of the
This registry should be RIFTEncodingLinkCapabilities.
Link capabilities. has the following initial values.
+=========================+=====+=========+==========+==============+
| Name |Value| Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+=========================+=====+=========+==========+==============+
| Reserved |0 | 0| 8.0 | All | |
| | | | Versions | |
+-------------------------+-----+---------+----------+--------------+
| bfd |1 | 1| 8.0 | | Indicates |
| | | | | that the |
| | | | | link is |
| | | | | supporting |
| | | | | bfd. BFD. |
+-------------------------+-----+---------+----------+--------------+
| ipv4_forwarding_capable |2 | 2| 8.0 | | Indicates |
| | | | | whether the |
| | | | | interface |
| | | | | will |
| | | | | support |
| | | | | ipv4 IPv4 |
| | | | | forwarding. |
+-------------------------+-----+---------+----------+--------------+
Table 25 25: Link Capabilities
10.3.19. RIFTEncodingLinkIDPair Registry RIFT/encoding/LinkIDPair
The name of the registry should be RIFTEncodingLinkIDPair. LinkID pair describes one of the parallel links between two
nodes.
+============================+=====+=======+========+===============+
This registry has the following initial values.
+============================+=====+=======+========+==============+
| Name |Value| Min.| Max.| |Value|Min. |Max. | Comment |
| | |Schema |Schema | | Schema| Schema|
| | |Version|Version | |Version| Version| |
+============================+=====+=======+========+===============+
+============================+=====+=======+========+==============+
| Reserved |0 |8.0 |All | 0| 8.0| All| |
| | | |Versions| |
+----------------------------+-----+-------+--------+---------------+
+----------------------------+-----+-------+--------+--------------+
| local_id |1 |8.0 | 1| 8.0| | Node-wide |
| | | | | unique value |
| | | | | for the |
| | | | | local link. |
+----------------------------+-----+-------+--------+---------------+
+----------------------------+-----+-------+--------+--------------+
| remote_id |2 |8.0 | 2| 8.0| | Received the |
| | | | | remote link |
| | | | | id ID for this |
| | | | | link. |
+----------------------------+-----+-------+--------+---------------+
+----------------------------+-----+-------+--------+--------------+
| platform_interface_index |10 |8.0 | 10| 8.0| | Describes |
| | | | | the local |
| | | | | interface |
| | | | | index of the |
| | | | | link. |
+----------------------------+-----+-------+--------+---------------+
+----------------------------+-----+-------+--------+--------------+
| platform_interface_name |11 |8.0 | 11| 8.0| | Describes |
| | | | | the local |
| | | | | interface |
| | | | | name. |
+----------------------------+-----+-------+--------+---------------+
+----------------------------+-----+-------+--------+--------------+
| trusted_outer_security_key |12 |8.0 | 12| 8.0| | Indicates |
| | | | | whether the |
| | | | | link is |
| | | | | secured, |
| | | | | i.e. i.e., |
| | | | | protected by |
| | | | | outer key, |
| | | | | absence of |
| | | | | this element |
| | | | | means no |
| | | | | indication, |
| | | | | undefined |
| | | | | outer key |
| | | | | means not |
| | | | | secured. |
+----------------------------+-----+-------+--------+---------------+
+----------------------------+-----+-------+--------+--------------+
| bfd_up |13 |8.0 | 13| 8.0| | Indicates |
| | | | | whether the |
| | | | | link is |
| | | | | protected by |
| | | | | established an |
| | | | | bfd session. established |
+----------------------------+-----+-------+--------+---------------+
| address_families | 14| 8.0| | Optional | | BFD session. |
+----------------------------+-----+-------+--------+--------------+
| address_families |14 |8.0 | | indication Optional |
| | | | | which indication |
| | | | | that address |
| | | | | families are |
| | | | | up on the |
| | | | | interface. |
+----------------------------+-----+-------+--------+---------------+
+----------------------------+-----+-------+--------+--------------+
Table 26
10.3.20. RIFTEncodingNeighbor Registry RIFT/encoding/Neighbor
The name of the
This registry should be RIFTEncodingNeighbor.
Neighbor structure. has the following initial values.
+============+=======+=============+=============+=================+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+============+=======+=============+=============+=================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+------------+-------+-------------+-------------+-----------------+
| originator | 1 | 8.0 | | System id ID of |
| | | | | the originator. |
+------------+-------+-------------+-------------+-----------------+
| remote_id | 2 | 8.0 | | Id ID of remote |
| | | | | side of the |
| | | | | link. |
+------------+-------+-------------+-------------+-----------------+
Table 27 27: Neighbor Structure
10.3.21. RIFTEncodingNodeCapabilities Registry RIFT/encoding/NodeCapabilities
The name of the
This registry should be RIFTEncodingNodeCapabilities.
Capabilities has the node supports.
+========================+=====+=======+==========+=================+ following initial values.
+========================+=====+=========+==========+==============+
| Name |Value| Min.| Min. | Max. | Comment |
| | | Schema| Schema | Schema | |
| | | |Version| Version | Version | |
+========================+=====+=======+==========+=================+
+========================+=====+=========+==========+==============+
| Reserved |0 | 8.0 | 0| 8.0| All | |
| | | | Versions | |
+------------------------+-----+-------+----------+-----------------+
+------------------------+-----+---------+----------+--------------+
| protocol_minor_version |1 | 8.0 | 1| 8.0| | Must |
| | | | | advertise |
| | | | | supported |
| | | | | minor |
| | | | | version |
| | | | | dialect that |
| | | | | way. |
+------------------------+-----+-------+----------+-----------------+
+------------------------+-----+---------+----------+--------------+
| flood_reduction |2 | 8.0 | 2| 8.0| | Indicates that |
| | | | | that node |
| | | | | supports |
| | | | | flood |
| | | | | reduction. |
+------------------------+-----+-------+----------+-----------------+
+------------------------+-----+---------+----------+--------------+
| hierarchy_indications |3 | 8.0 | 3| 8.0| | Indicates |
| | | | | place in |
| | | | | hierarchy, |
| | | | | i.e. top-of- i.e., top of |
| | | | | fabric or leaf |
| | | | | leaf only (in ztp) |
| | | | | (in ZTP) or |
| | | | | support for |
| | | | | leaf-2-leaf leaf-to-leaf |
| | | | | procedures. |
+------------------------+-----+-------+----------+-----------------+
+------------------------+-----+---------+----------+--------------+
Table 28 28: Capabilities the Node Supports
10.3.22. RIFTEncodingNodeFlags Registry RIFT/encoding/NodeFlags
The name of the
This registry should be RIFTEncodingNodeFlags.
Indication flags of has the node. following initial values.
+==========+=======+=========+==========+===========================+
| Name | Value | Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+==========+=======+=========+==========+===========================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------+----------+---------------------------+
| overload | 1 | 8.0 | | Indicates that node |
| | | | | is in overload, overload; do |
| | | | | not transit traffic |
| | | | | through it. |
+----------+-------+---------+----------+---------------------------+
Table 29
10.3.23. Registry RIFT/encoding/NodeNeighborsTIEElement
The name 29: Indication Flags of the Node
10.3.23. RIFTEncodingNodeNeighborsTIEElement Registry
This registry should be
RIFTEncodingNodeNeighborsTIEElement.
neighbor of a node
+===========+=======+=========+==========+==========================+ has the following initial values.
+===========+=======+=========+==========+======================+
| Name | Value | Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+===========+=======+=========+==========+==========================+
+===========+=======+=========+==========+======================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-----------+-------+---------+----------+--------------------------+
+-----------+-------+---------+----------+----------------------+
| level | 1 | 8.0 | | Level of neighbor. |
+-----------+-------+---------+----------+--------------------------+
+-----------+-------+---------+----------+----------------------+
| cost | 3 | 8.0 | | Cost to neighbor. |
| | | | | ignore Ignore anything |
| | | | | equal or larger than |
| | | | | `infinite_distance` 'infinite_distance' |
| | | | | and equal to |
| | | | | `invalid_distance`. 'invalid_distance'. |
+-----------+-------+---------+----------+--------------------------+
+-----------+-------+---------+----------+----------------------+
| link_ids | 4 | 8.0 | | Carries description |
| | | | | of multiple parallel |
| | | | | links in a tie. |
+-----------+-------+---------+----------+--------------------------+
+-----------+-------+---------+----------+----------------------+
| bandwidth | 5 | 8.0 | | Total bandwith bandwidth to |
| | | | | neighbor as sum of |
| | | | | all parallel links. |
+-----------+-------+---------+----------+--------------------------+
+-----------+-------+---------+----------+----------------------+
Table 30 30: Neighbor of a Node
10.3.24. RIFTEncodingNodeTIEElement Registry RIFT/encoding/NodeTIEElement
The name of the
This registry should be RIFTEncodingNodeTIEElement.
Description of a node. has the following initial values.
+=================+=======+=========+==========+====================+
| Name | Value | Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+=================+=======+=========+==========+====================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-----------------+-------+---------+----------+--------------------+
| level | 1 | 8.0 | | Level of the |
| | | | | node. |
+-----------------+-------+---------+----------+--------------------+
| neighbors | 2 | 8.0 | | Node's neighbors. |
| | | | | multiple Multiple node |
| | | | | ties can carry |
| | | | | disjoint sets of |
| | | | | neighbors. |
+-----------------+-------+---------+----------+--------------------+
| capabilities | 3 | 8.0 | | Capabilities of |
| | | | | the node. |
+-----------------+-------+---------+----------+--------------------+
| flags | 4 | 8.0 | | Flags of the |
| | | | | node. |
+-----------------+-------+---------+----------+--------------------+
| name | 5 | 8.0 | | Optional node |
| | | | | name for easier |
| | | | | operations. |
+-----------------+-------+---------+----------+--------------------+
| pod | 6 | 8.0 | | Pod to which the |
| | | | | node belongs. |
+-----------------+-------+---------+----------+--------------------+
| startup_time | 7 | 8.0 | | Optional startup |
| | | | | time of the node node. |
+-----------------+-------+---------+----------+--------------------+
| miscabled_links | 10 | 8.0 | | If any local |
| | | | | links are |
| | | | | miscabled, this |
| | | | | indication is |
| | | | | flooded. |
+-----------------+-------+---------+----------+--------------------+
| same_plane_tofs | 12 | 8.0 | | Tofs ToFs in the same |
| | | | | plane. only Only |
| | | | | carried by tof. ToF. |
| | | | | multiple Multiple node |
| | | | | ties can carry |
| | | | | disjoint sets of |
| | | | | tofs which ToFs that must be |
| | | | | be joined to form a |
| | | | | a single set. |
+-----------------+-------+---------+----------+--------------------+
| fabric_id | 20 | 8.0 | | It provides the |
| | | | | optional id ID of |
| | | | | the fabric |
| | | | | configured configured. |
+-----------------+-------+---------+----------+--------------------+
Table 31 31: Description of a Node
10.3.25. RIFTEncodingPacketContent Registry RIFT/encoding/PacketContent
The name of the
This registry should be RIFTEncodingPacketContent.
Content of a RIFT packet. has the following initial values.
+==========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+==========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------------------+-------------+---------+
| lie | 1 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
| tide | 2 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
| tire | 3 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
| tie | 4 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
Table 32 32: Content of a RIFT Packet
10.3.26. RIFTEncodingPacketHeader Registry RIFT/encoding/PacketHeader
The name of the
This registry should be RIFTEncodingPacketHeader.
Common RIFT packet header. has the following initial values.
+===============+=======+=========+==========+===================+
| Name | Value | Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+===============+=======+=========+==========+===================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+---------------+-------+---------+----------+-------------------+
| major_version | 1 | 8.0 | | Major version of |
| | | | | protocol. |
+---------------+-------+---------+----------+-------------------+
| minor_version | 2 | 8.0 | | Minor version of |
| | | | | protocol. |
+---------------+-------+---------+----------+-------------------+
| sender | 3 | 8.0 | | Node sending the |
| | | | | packet, in case |
| | | | | of lie/tire/tide LIE/TIRE/TIDE |
| | | | | also the |
| | | | | originator of it. |
+---------------+-------+---------+----------+-------------------+
| level | 4 | 8.0 | | Level of the node |
| | | | | sending the |
| | | | | packet, required |
| | | | | on everything |
| | | | | except lies. lack LIEs. |
| | | | | Lack of presence on |
| | | | | lies on LIEs indicates |
| | | | | undefined_level |
| | | | | and is used in |
| | | | | ztp ZTP procedures. |
+---------------+-------+---------+----------+-------------------+
Table 33 33: Common RIFT Packet Header
10.3.27. RIFTEncodingPrefixAttributes Registry RIFT/encoding/PrefixAttributes
The name of the
This registry should be RIFTEncodingPrefixAttributes.
Attributes of a prefix. has the following initial values.
+===================+=======+=========+==========+==================+
| Name | Value | Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+===================+=======+=========+==========+==================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-------------------+-------+---------+----------+------------------+
| metric | 2 | 8.0 | | Distance of the |
| | | | | prefix. |
+-------------------+-------+---------+----------+------------------+
| tags | 3 | 8.0 | | Generic |
| | | | | unordered set |
| | | | | of route tags, |
| | | | | can be |
| | | | | redistributed |
| | | | | to other |
| | | | | protocols or |
| | | | | use used within the |
| | | | | context of real |
| | | | | time analytics. |
+-------------------+-------+---------+----------+------------------+
| monotonic_clock | 4 | 8.0 | | Monotonic clock |
| | | | | for mobile |
| | | | | addresses. |
+-------------------+-------+---------+----------+------------------+
| loopback | 6 | 8.0 | | Indicates if |
| | | | | the prefix is a |
| | | | | node loopback. |
+-------------------+-------+---------+----------+------------------+
| directly_attached | 7 | 8.0 | | Indicates that |
| | | | | the prefix is |
| | | | | directly |
| | | | | attached. |
+-------------------+-------+---------+----------+------------------+
| from_link | 10 | 8.0 | | Link to which |
| | | | | the address |
| | | | | belongs to. |
+-------------------+-------+---------+----------+------------------+
| label | 12 | 8.0 | | Optional, per per- |
| | | | | prefix |
| | | | | significant |
| | | | | label. |
+-------------------+-------+---------+----------+------------------+
Table 34 34: Attributes of a Prefix
10.3.28. RIFTEncodingPrefixTIEElement Registry RIFT/encoding/PrefixTIEElement
The name of the
This registry should be RIFTEncodingPrefixTIEElement.
TIE carrying prefixes has the following initial values.
+==========+=======+=============+=============+================+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+==========+=======+=============+=============+================+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+-------------+-------------+----------------+
| prefixes | 1 | 8.0 | | Prefixes with |
| | | | | the associated |
| | | | | attributes. |
+----------+-------+-------------+-------------+----------------+
Table 35 35: TIE Carrying Prefixes
10.3.29. RIFTEncodingProtocolPacket Registry RIFT/encoding/ProtocolPacket
The name of the
This registry should be RIFTEncodingProtocolPacket.
RIFT packet structure. has the following initial values.
+==========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+==========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------------------+-------------+---------+
| header | 1 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
| content | 2 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
Table 36 36: RIFT Packet Structure
10.3.30. RIFTEncodingTIDEPacket Registry RIFT/encoding/TIDEPacket
The name of the
This registry should be RIFTEncodingTIDEPacket.
TIDE with *sorted* TIE headers. has the following initial values.
+=============+=======+=============+=============+===============+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+=============+=======+=============+=============+===============+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+-------------+-------+-------------+-------------+---------------+
| start_range | 1 | 8.0 | | First tie TIE |
| | | | | header in the |
| | | | | tide TIDE packet. |
+-------------+-------+-------------+-------------+---------------+
| end_range | 2 | 8.0 | | Last tie TIE |
| | | | | header in the |
| | | | | tide TIDE packet. |
+-------------+-------+-------------+-------------+---------------+
| headers | 3 | 8.0 | | _sorted_ list |
| | | | | of headers. |
+-------------+-------+-------------+-------------+---------------+
Table 37 37: TIDE with Sorted TIE Headers
10.3.31. RIFTEncodingTIEElement Registry RIFT/encoding/TIEElement
The name of the
This registry should be RIFTEncodingTIEElement.
Single element in a TIE.
+=========================================+=====+=======+========+=================================+ has the following initial values.
+========================+=====+=======+========+===================+
|Name |Value| Min.| Max.|Comment |Value|Min. |Max. |Comment |
| | |Schema |Schema | | Schema| Schema|
| | |Version|Version | |Version| Version| |
+=========================================+=====+=======+========+=================================+
+========================+=====+=======+========+===================+
|Reserved |0 |8.0 |All | 0| 8.0| All| |
| | | |Versions| |
+-----------------------------------------+-----+-------+--------+---------------------------------+
+------------------------+-----+-------+--------+-------------------+
|node |1 |8.0 | 1| 8.0| | Used |Used in case of enum| |
| | | | common.tietypetype.nodetietype.|
+-----------------------------------------+-----+-------+--------+---------------------------------+
|prefixes |enum | 2| 8.0|
| Used | | | |common.tietypetype.|
| | | | |nodetietype. |
+------------------------+-----+-------+--------+-------------------+
|prefixes |2 |8.0 | |Used in case of enum| |
| | | |common.tietypetype.prefixtietype.|
+-----------------------------------------+-----+-------+--------+---------------------------------+
|positive_disaggregation_prefixes | 3| 8.0| |enum | Positive
| | | | |common.tietypetype.|
| | | | |prefixtietype. |
+------------------------+-----+-------+--------+-------------------+
|positive_disaggregation_|3 |8.0 | |Positive prefixes (always| |
|prefixes | | | |(always | southbound).|
+-----------------------------------------+-----+-------+--------+---------------------------------+
|negative_disaggregation_prefixes
| 5| 8.0| | Transitive, negative prefixes| | | |southbound). |
+------------------------+-----+-------+--------+-------------------+
|negative_disaggregation_|5 |8.0 | |Transitive, | (always
|prefixes | | | |negative prefixes |
| | | | |(always southbound)|
+-----------------------------------------+-----+-------+--------+---------------------------------+
+------------------------+-----+-------+--------+-------------------+
|external_prefixes |6 |8.0 | 6| 8.0| |Externally | Externally reimported prefixes.|
+-----------------------------------------+-----+-------+--------+---------------------------------+
|positive_external_disaggregation_prefixes| 7| 8.0|
| Positive | | | |reimported |
| | | | |prefixes. |
+------------------------+-----+-------+--------+-------------------+
|positive_external_ |7 |8.0 | |Positive external disaggregated| |
|disaggregation_prefixes | | | |disaggregated | prefixes (always southbound).|
+-----------------------------------------+-----+-------+--------+---------------------------------+
| | | | |prefixes |
| | | | |(always |
| | | | |southbound). |
+------------------------+-----+-------+--------+-------------------+
|keyvalues |9 |8.0 | 9| 8.0| |Key-value | Key-value store elements.|
+-----------------------------------------+-----+-------+--------+---------------------------------+
| | | | |store elements. |
+------------------------+-----+-------+--------+-------------------+
Table 38 38: Single Element in a TIE
10.3.32. RIFTEncodingTIEHeader Registry RIFT/encoding/TIEHeader
The name of the
This registry should be RIFTEncodingTIEHeader.
Header of a TIE. has the following initial values.
+======================+=======+=========+==========+==============+
| Name | Value | Min. | Max. | Comment |
| | | Schema | Schema | |
| | | Version | Version | |
+======================+=======+=========+==========+==============+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------------------+-------+---------+----------+--------------+
| tieid | 2 | 8.0 | | Id ID of tie. TIE. |
+----------------------+-------+---------+----------+--------------+
| seq_nr | 3 | 8.0 | | Sequence |
| | | | | number of |
| | | | | tie. TIE. |
+----------------------+-------+---------+----------+--------------+
| origination_time | 10 | 8.0 | | Absolute |
| | | | | timestamp |
| | | | | when tie TIE was |
| | | | | generated. |
+----------------------+-------+---------+----------+--------------+
| origination_lifetime | 12 | 8.0 | | Original |
| | | | | lifetime |
| | | | | when tie TIE was |
| | | | | generated. |
+----------------------+-------+---------+----------+--------------+
Table 39
10.3.33. Registry RIFT/encoding/TIEHeaderWithLifeTime
The name of the registry should be RIFTEncodingTIEHeaderWithLifeTime. 39: Header of a TIE as described in TIRE/TIDE.
10.3.33. RIFTEncodingTIEHeaderWithLifeTime Registry
This registry has the following initial values.
+====================+=======+=============+==========+===========+
| Name | Value | Min. Schema | Max. | Comment |
| | | Version | Schema | |
| | | | Version | |
+====================+=======+=============+==========+===========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+--------------------+-------+-------------+----------+-----------+
| header | 1 | 8.0 | | |
+--------------------+-------+-------------+----------+-----------+
| remaining_lifetime | 2 | 8.0 | | Remaining |
| | | | | lifetime. |
+--------------------+-------+-------------+----------+-----------+
Table 40 40: Header of a TIE as Described in TIRE/TIDE
10.3.34. RIFTEncodingTIEID Registry RIFT/encoding/TIEID
The name of the
This registry should be RIFTEncodingTIEID.
Unique ID of a TIE. has the following initial values.
+============+=======+=============+=============+============+
| Name | Value | Min. Schema | Max. Schema | Comment |
| | | Version | Version | |
+============+=======+=============+=============+============+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+------------+-------+-------------+-------------+------------+
| direction | 1 | 8.0 | | Direction |
| | | | | of tie. TIE. |
+------------+-------+-------------+-------------+------------+
| originator | 2 | 8.0 | | Indicates |
| | | | | originator |
| | | | | of tie. TIE. |
+------------+-------+-------------+-------------+------------+
| tietype | 3 | 8.0 | | Type of |
| | | | | tie. TIE. |
+------------+-------+-------------+-------------+------------+
| tie_nr | 4 | 8.0 | | Number of |
| | | | | tie. TIE. |
+------------+-------+-------------+-------------+------------+
Table 41 41: Unique ID of a TIE
10.3.35. RIFTEncodingTIEPacket Registry RIFT/encoding/TIEPacket
The name of the
This registry should be RIFTEncodingTIEPacket.
TIE packet has the following initial values.
+==========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+==========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------------------+-------------+---------+
| header | 1 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
| element | 2 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
Table 42 42: TIE Packet
10.3.36. RIFTEncodingTIREPacket Registry RIFT/encoding/TIREPacket
The name of the
This registry should be RIFTEncodingTIREPacket.
TIRE packet has the following initial values.
+==========+=======+=====================+=============+=========+
| Name | Value | Min. Schema Version | Max. Schema | Comment |
| | | | Version | |
+==========+=======+=====================+=============+=========+
| Reserved | 0 | 8.0 | All | |
| | | | Versions | |
+----------+-------+---------------------+-------------+---------+
| headers | 1 | 8.0 | | |
+----------+-------+---------------------+-------------+---------+
Table 43 43: TIRE Packet
11. Acknowledgments
A new routing protocol in its complexity is not a product of a parent
but of a village as the author list shows already. However, many
more people provided input, fine-combed the specification based on
their experience in design, implementation or application of
protocols in IP fabrics. This section will make an inadequate
attempt in recording their contribution.
Many thanks to Naiming Shen for some of the early discussions around
the topic of using IGPs for routing in topologies related to Clos.
Russ White to be especially acknowledged for the key conversation on
epistemology that allowed to tie current asynchronous distributed
systems theory results to a modern protocol design presented in this
scope. Adrian Farrel, Joel Halpern, Jeffrey Zhang, Krzysztof
Szarkowicz, Nagendra Kumar, Melchior Aelmans, Kaushal Tank, Will
Jones, Moin Ahmed, Sandy Zhang, Donald Eastlake provided thoughtful
comments that improved the readability of the document and found good
amount of corners where the light failed to shine. Kris Price was
first to mention single router, single arm default considerations.
Jeff Tantsura helped out with some initial thoughts on BFD
interactions while Jeff Haas corrected several misconceptions about
BFD's finer points and helped to improve the security section around
leaf considerations. Artur Makutunowicz pointed out many possible
improvements and acted as sounding board in regard to modern protocol
implementation techniques RIFT is exploring. Barak Gafni formalized
first time clearly the problem of partitioned spine and fallen leaves
on a (clean) napkin in Singapore that led to the very important part
of the specification centered around multiple ToF planes and negative
disaggregation. Igor Gashinsky and others shared many thoughts on
problems encountered in design and operation of large-scale data
center fabrics. Xu Benchong found a delicate error in the flooding
procedures and a schema datatype size mismatch.
Too many people to mention provided reviews from many directions in
IETF, often pointing to critical defects, sometimes asking for things
again that have been removed by one the previous reviewers as
objectionable or superfluous, and many times claiming the document
being somewhere on the extremes between too crowded with the obvious
and omitting introduction to cryptic concepts everywhere. The result
is the best editors could do to find a balance of a document guiding
the reader by Section 2 into a specification tight enough to result
in interoperable implementations while at the same time introducing
enough operational context of IP routable fabrics to guarantee a
concise, common language when facing unaccustomed concepts the
protocol relies on. In the process it was important to not end up
carrying Aesop's donkey of course so while the result may not be
perceived as perfect by everyone it should be practically speaking
more than sufficient for everyone that ends up using it in the
future.
Last but not least, Alvaro Retana, John Scudder, Andrew Alston and
Jim Guichard guided the undertaking as ADs by asking many necessary
procedural and technical questions which did not only improve the
content but did also lay out the track towards publication. And
Roman Danyliw is mentioned very last but not least either for his
painstakingly detailed review and improvement of security aspects of
the specification.
12. Contributors
This work is a product of a list of individuals which are all to be
considered major contributors independent of the fact whether their
name made it to the limited boilerplate author's list or not.
+======================+===+==================+===+================+
+======================+===+==================+===+================+
| Tony Przygienda, Ed. | | | | | | Pascal Thubert |
+----------------------+---+------------------+---+----------------+
| Juniper | | | | | | Cisco |
+----------------------+---+------------------+---+----------------+
| Bruno Rijsman | | | Jordan Head, Ed. | | | Dmitry |
| | | | | Afanasiev |
+----------------------+---+------------------+---+----------------+
| Individual | | | Juniper | | | Individual |
+----------------------+---+------------------+---+----------------+
| Don Fedyk | | | Alia Atlas | | | John Drake |
+----------------------+---+------------------+---+----------------+
| LabN | | | Individual | | | Individual |
+----------------------+---+------------------+---+----------------+
| Ilya Vershkov | | | | | | | | |
+----------------------+---+------------------+---+----------------+
| NVidia | | | | | | | | |
+----------------------+---+------------------+---+----------------+
Table 44: RIFT Authors
13. References
13.1.
11.1. Normative References
[EUI64] IEEE, "Guidelines for Use of Extended Unique Identifier
(EUI), Organizationally Unique Identifier (OUI), and
Company ID (CID)", IEEE EUI,
<http://standards.ieee.org/develop/regauth/tut/eui.pdf>. <https://standards-support.ieee.org/hc/
en-us/articles/4888705676564-Guidelines-for-Use-of-
Extended-Unique-Identifier-EUI-Organizationally-Unique-
Identifier-OUI-and-Company-ID-CID>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
RFC 2365, DOI 10.17487/RFC2365, July 1998,
<https://www.rfc-editor.org/info/rfc2365>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<https://www.rfc-editor.org/info/rfc5082>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, DOI 10.17487/RFC5709, October
2009, <https://www.rfc-editor.org/info/rfc5709>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[RFC7987] Ginsberg, L., Wells, P., Decraene, B., Przygienda, T., and
H. Gredler, "IS-IS Minimum Remaining Lifetime", RFC 7987,
DOI 10.17487/RFC7987, October 2016,
<https://www.rfc-editor.org/info/rfc7987>.
[RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch,
"PKCS #1: RSA Cryptography Specifications Version 2.2",
RFC 8017, DOI 10.17487/RFC8017, November 2016,
<https://www.rfc-editor.org/info/rfc8017>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8202] Ginsberg, L., Previdi, S., and W. Henderickx, "IS-IS
Multi-Instance", RFC 8202, DOI 10.17487/RFC8202, June
2017, <https://www.rfc-editor.org/info/rfc8202>.
[RFC8505] Thubert, P., Ed., Nordmark, E., Chakrabarti, S., and C.
Perkins, "Registration Extensions for IPv6 over Low-Power
Wireless Personal Area Network (6LoWPAN) Neighbor
Discovery", RFC 8505, DOI 10.17487/RFC8505, November 2018,
<https://www.rfc-editor.org/info/rfc8505>.
[RFC9300] Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
Cabellos, Ed., "The Locator/ID Separation Protocol
(LISP)", RFC 9300, DOI 10.17487/RFC9300, October 2022,
<https://www.rfc-editor.org/info/rfc9300>.
[RFC9301] Farinacci, D., Maino, F., Fuller, V., and A. Cabellos,
Ed., "Locator/ID Separation Protocol (LISP) Control
Plane", RFC 9301, DOI 10.17487/RFC9301, October 2022,
<https://www.rfc-editor.org/info/rfc9301>.
[SHA-2] National Institute of Standards and Technology, NIST, "Secure Hash Standard, Standard (SHS)", FIPS PUB 180-3", 2008. 180-4,
DOI 10.6028/NIST.FIPS.180-4, July 2015,
<https://csrc.nist.gov/pubs/fips/180-4/upd1/final>.
[thrift] Apache Software Foundation, "Thrift Language
Implementation and "Apache Thrift Documentation",
<https://github.com/apache/thrift/tree/0.15.0/doc>.
13.2.
<https://thrift.apache.org/docs/>.
11.2. Informative References
[APPLICABILITY]
Wei, Y., Zhang, Z., Afanasiev, D., Thubert, P., and T.
Przygienda, "RIFT Applicability", Applicability and Operational
Considerations", Work in Progress, Internet-Draft, draft-ietf-rift-applicability-15, 13 May draft-
ietf-rift-applicability-17, 17 June 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
rift-applicability-15>.
<https://datatracker.ietf.org/doc/html/draft-ietf-rift-
applicability-17>.
[CLOS] Yuan, X., "On Nonblocking Folded-Clos Networks in Computer
Communication Environments", 2011 IEEE International
Parallel & Distributed Processing Symposium, 2011.
DOI 10.1109/IPDPS.2011.27, 2011,
<https://ieeexplore.ieee.org/document/6012836>.
[DayOne] Aelmans, M., Vandezande, O., Rijsman, B., Head, J., Graf,
C., Alberro, L., Mali, H., and O. Steudler, "Day One:
Routing in Fat Trees (RIFT)", Juniper DayOne . Network Books,
ISBN 978-1-7363160-0-9, December 2020.
[DIJKSTRA] Dijkstra, E. W., "A Note on Two Problems in Connexion with
Graphs", Journal Numer. Math. , 1959. Numerische Mathematik, vol. 1, pp. 269-271,
DOI 10.1007/BF01386390, December 1959,
<https://link.springer.com/article/10.1007/BF01386390>.
[DYNAMO] De Candia et al., Candia, G., Hastorun, D., Jampani, M., Kakulpati, G.,
Lakshman, A., Pilchin, A., Sivasubramanian, S., Vosshall,
P., and W. Vogels, "Dynamo: amazon's highly available
key-value key-
value store", ACM SIGOPS symposium on Operating
systems principles (SOSP '07), 2007. Systems Review, vol.
41, no. 6, pp. 205-220, DOI 10.1145/1323293.1294281, 2007,
<https://dl.acm.org/doi/10.1145/1323293.1294281>.
[EPPSTEIN] Eppstein, D., "Finding the k-Shortest k Shortest Paths", 1997. 1997,
<https://ics.uci.edu/~eppstein/pubs/Epp-SJC-98.pdf>.
[FATTREE] Leiserson, C. E., "Fat-Trees: Universal Networks for
Hardware-Efficient Supercomputing", 1985. IEEE Transactions on
Computers, vol. C-34, no. 10, pp. 892-901,
DOI 10.1109/TC.1985.6312192, October 1985,
<https://ieeexplore.ieee.org/document/6312192>.
[IEEEstd1588]
IEEE, "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
IEEE Standard 1588, Std 1588-2008, DOI 10.1109/IEEESTD.2008.4579760, July
2008, <https://ieeexplore.ieee.org/document/4579760/>.
[IEEEstd8021AS]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks - Timing and Synchronization for Time-Sensitive
Applications in Bridged Local Area Networks", IEEE Standard 802.1AS, Std
802.1AS-2011, DOI 10.1109/IEEESTD.2011.5741898, March
2011, <https://ieeexplore.ieee.org/document/5741898/>.
[RFC0826] Plummer, D., "An Ethernet Address Resolution Protocol: Or
Converting Network Protocol Addresses to 48.bit Ethernet
Address for Transmission on Ethernet Hardware", STD 37,
RFC 826, DOI 10.17487/RFC0826, November 1982,
<https://www.rfc-editor.org/info/rfc826>.
[RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
DOI 10.17487/RFC1982, August 1996,
<https://www.rfc-editor.org/info/rfc1982>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997,
<https://www.rfc-editor.org/info/rfc2104>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC2991] Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
Multicast Next-Hop Selection", RFC 2991,
DOI 10.17487/RFC2991, November 2000,
<https://www.rfc-editor.org/info/rfc2991>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<https://www.rfc-editor.org/info/rfc4862>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
[RFC5837] Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed., Shen,
N., and JR. Rivers, "Extending ICMP for Interface and
Next-Hop Identification", RFC 5837, DOI 10.17487/RFC5837,
April 2010, <https://www.rfc-editor.org/info/rfc5837>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC6550] Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
Low-Power and Lossy Networks", RFC 6550,
DOI 10.17487/RFC6550, March 2012,
<https://www.rfc-editor.org/info/rfc6550>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
[VAHDAT08] Al-Fares, M., Loukissas, A., and A. Vahdat, "A Scalable,
Commodity Data Center Network Architecture", ACM SIGCOMM ,
2008.
Computer Communication Review, vol. 38, no. 4, pp. 63-74,
DOI 10.1145/1402946.1402967, August 2008,
<https://dl.acm.org/doi/10.1145/1402946.1402967>.
[VFR] Giotsas, V. and S. Zhou, "Valley-free violation in
Internet routing - Analysis based on BGP Community data",
2012 IEEE International Conference on Communications
(ICC) , 2012.
(ICC), DOI 10.1109/ICC.2012.6363987, 2012,
<https://ieeexplore.ieee.org/document/6363987>.
Appendix A. Sequence Number Binary Arithmetic
This section defines a variant of sequence number arithmetic related
to [RFC1982] explained over two complement arithmetic arithmetic, which is easy
to implement.
Assuming straight two complement's subtractions on the bit-width bit width of
the sequence numbers, the corresponding >: and =: relations are
defined as:
* U_1, U_2 are 12-bits aligned unsigned version number
* D_f is ( U_1 - U_2 ) interpreted as two complement signed 12-bits
* D_b is ( U_2 - U_1 ) interpreted as two complement signed 12-bits
* U_1 >: U_2 IIF D_f > 0 *and* D_b < 0
* U_1 =: U_2 IIF D_f = 0
The >: relationship is anti-symmetric but not transitive. Observe
that this leaves >: of the numbers having maximum two complement
distance, e.g. e.g., ( 0 and 0x800 ) undefined in the 12-bits case since
D_f and D_b are both -0x7ff.
A simple example of the relationship in case of 3-bit arithmetic
follows as table indicating D_f/D_b values and then the relationship
of U_1 to U_2:
+=========+=====+=====+=====+=====+=====+=====+=====+=====+
| U2 / U1 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
+=========+=====+=====+=====+=====+=====+=====+=====+=====+
| 0 | +/+ | +/- | +/- | +/- | -/- | -/+ | -/+ | -/+ |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
| 1 | -/+ | +/+ | +/- | +/- | +/- | -/- | -/+ | -/+ |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
| 2 | -/+ | -/+ | +/+ | +/- | +/- | +/- | -/- | -/+ |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
| 3 | -/+ | -/+ | -/+ | +/+ | +/- | +/- | +/- | -/- |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
| 4 | -/- | -/+ | -/+ | -/+ | +/+ | +/- | +/- | +/- |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
| 5 | +/- | -/- | -/+ | -/+ | -/+ | +/+ | +/- | +/- |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
| 6 | +/- | +/- | -/- | -/+ | -/+ | -/+ | +/+ | +/- |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
| 7 | +/- | +/- | +/- | -/- | -/+ | -/+ | -/+ | +/+ |
+---------+-----+-----+-----+-----+-----+-----+-----+-----+
Table 44
+=========+===+===+===+===+===+===+===+===+
| U2 / U1 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
+=========+===+===+===+===+===+===+===+===+
| 0 | = | > | > | > | ? | < | < | < |
+---------+---+---+---+---+---+---+---+---+
| 1 | < | = | > | > | > | ? | < | < |
+---------+---+---+---+---+---+---+---+---+
| 2 | < | < | = | > | > | > | ? | < |
+---------+---+---+---+---+---+---+---+---+
| 3 | < | < | < | = | > | > | > | ? |
+---------+---+---+---+---+---+---+---+---+
| 4 | ? | < | < | < | = | > | > | > |
+---------+---+---+---+---+---+---+---+---+
| 5 | > | ? | < | < | < | = | > | > |
+---------+---+---+---+---+---+---+---+---+
| 6 | > | > | ? | < | < | < | = | > |
+---------+---+---+---+---+---+---+---+---+
| 7 | > | > | > | ? | < | < | < | = |
+---------+---+---+---+---+---+---+---+---+
Table 45
Appendix B. Examples
B.1. Normal Operation
^ N +--------+ +--------+
Level 2 | |ToF 21| |ToF 22|
E <-*-> W ++-+--+-++ ++-+--+-++
| | | | | | | | |
S v P111/2 |P121/2 | | | |
^ ^ ^ ^ | | | |
| | | | | | | |
+--------------+ | +-----------+ | | | +---------------+
| | | | | | | |
South +-----------------------------+ | | ^
| | | | | | | All
0/0 0/0 0/0 +-----------------------------+ TIEs
v v v | | | | |
| | +-+ +<-0/0----------+ | |
| | | | | | | |
+-+----++ +-+----++ ++----+-+ ++-----++
Level 1 | | | | | | | |
|Spin111| |Spin112| |Spin121| |Spin122|
+-+---+-+ ++----+-+ +-+---+-+ ++---+--+
| | | South | | | |
| +---0/0--->-----+ 0/0 | +----------------+ |
0/0 | | | | | | |
| +---<-0/0-----+ | v | +--------------+ | |
v | | | | | | |
+-+---+-+ +--+--+-+ +-+---+-+ +---+-+-+
Level 0 | | | | | | | |
|Leaf111| |Leaf112| |Leaf121| |Leaf122|
+-+-----+ +-+---+-+ +--+--+-+ +-+-----+
+ + \ / + +
Prefix111 Prefix112 \ / Prefix121 Prefix122
multi-homed
multihomed
Prefix
+---------- PoD 1 ---------+ +---------- PoD 2 ---------+
Figure 35: Normal Case Topology
This section describes RIFT deployment in the example topology given
in Figure 35 without any node or link failures. The scenario
disregards flooding reduction for simplicity's sake and compresses
the node names in some cases to fit them into the picture better.
First, the following bi-directional bidirectional adjacencies will be established:
1. ToF 21 (PoD 0) to Spine 111, Spine 112, Spine 121, and Spine 122
2. ToF 22 (PoD 0) to Spine 111, Spine 112, Spine 121, and Spine 122
3. Spine 111 to Leaf 111, 111 and Leaf 112
4. Spine 112 to Leaf 111, 111 and Leaf 112
5. Spine 121 to Leaf 121, 121 and Leaf 122
6. Spine 122 to Leaf 121, 121 and Leaf 122
Leaf 111 and Leaf 112 originate N-TIEs for Prefix 111 and Prefix 112
(respectively) to both Spine 111 and Spine 112 (Leaf 112 also
originates an N-TIE for the multi-homed multihomed prefix). Spine 111 and Spine
112 will then originate their own N-TIEs, as well as flood the N-TIEs
received from Leaf 111 and Leaf 112 to both ToF 21 and ToF 22.
Similarly, Leaf 121 and Leaf 122 originate North TIEs for Prefix 121
and Prefix 122 (respectively) to Spine 121 and Spine 122 (Leaf 121
also originates a North TIE for the multi-homed multihomed prefix). Spine 121
and Spine 122 will then originate their own North TIEs, as well as
flood the North TIEs received from Leaf 121 and Leaf 122 to both ToF
21 and ToF 22.
Spines hold only North TIEs of level 0 for their PoD, while leaves
only hold their own North TIEs while, at this point, both ToF 21 and
ToF 22 (as well as any northbound connected controllers) would have
the complete network topology.
ToF 21 and ToF 22 would then originate and flood South TIEs
containing any established adjacencies and a default IP route to all
spines. Spine 111, Spine 112, Spine 121, and Spine 122 will reflect
all Node South TIEs received from ToF 21 to ToF 22, 22 and all Node South
TIEs from ToF 22 to ToF 21. South TIEs will not be re-
propagated re-propagated
southbound.
South TIEs containing a default IP route are then originated by both
Spine 111 and Spine 112 toward towards Leaf 111 and Leaf 112. Similarly,
South TIEs containing a default IP route are originated by Spine 121
and Spine 122 toward towards Leaf 121 and Leaf 122.
At this point point, IP connectivity across the maximum number of viable
paths has been established for all leaves, with routing information
constrained to only the minimum amount that allows for normal
operation and redundancy.
B.2. Leaf Link Failure
| | | |
+-+---+-+ +-+---+-+
| | | |
|Spin111| |Spin112|
+-+---+-+ ++----+-+
| | | |
| +---------------+ X
| | | X Failure
| +-------------+ | X
| | | |
+-+---+-+ +--+--+-+
| | | |
|Leaf111| |Leaf112|
+-------+ +-------+
+ +
Prefix111 Prefix112
Figure 36: Single Leaf Link Failure
In the event of a link failure between Spine 112 and Leaf 112, both
nodes will originate new Node TIEs that contain their connected
adjacencies, except for the one that just failed. Leaf 112 will send
a North Node TIE to Spine 111. Spine 112 will send a North Node TIE
to ToF 21 and ToF 22 as well as a new Node South TIE to Leaf 111 that
will be reflected to Spine 111. Necessary SPF recomputation will
occur, resulting in Spine 112 no longer being in the forwarding path
for Prefix 112.
Spine 111 will also disaggregate Prefix 112 by sending new Prefix
South TIE to Leaf 111 and Leaf 112. Though disaggregation is covered
in more detail in the following section, it is worth mentioning in
this example as it further illustrates RIFT's mechanism to mitigate
traffic loss. Consider that Leaf 111 has yet to receive the more
specific (disaggregated) route from Spine 111. In such a scenario,
traffic from Leaf 111 toward towards Prefix 112 may still use Spine 112's
default route, causing it to traverse ToF 21 and ToF 22 back down via
Spine 111. While this behavior is suboptimal, it is transient in
nature and preferred to dropping traffic.
B.3. Partitioned Fabric
+--------+ +--------+
Level 2 |ToF 21| |ToF 22|
++-+--+-++ ++-+--+-++
| | | | | | | |
| | | | | | | 0/0
| | | | | | | |
| | | | | | | |
+--------------+ | +--- XXXXXX + | | | +---------------+
| | | | | | | |
| +-----------------------------+ | | |
0/0 | | | | | | |
| 0/0 0/0 +- XXXXXXXXXXXXXXXXXXXXXXXXX -+ |
| 1.1/16 | | | | | |
| | +-+ +-0/0-----------+ | |
| | | 1.1./16 | | | |
+-+----++ +-+-----+ ++-----0/0 ++----0/0
Level 1 | | | | | 1.1/16 | 1.1/16
|Spin111| |Spin112| |Spin121| |Spin122|
+-+---+-+ ++----+-+ +-+---+-+ ++---+--+
| | | | | | | |
| +---------------+ | | +----------------+ |
| | | | | | | |
| +-------------+ | | | +--------------+ | |
| | | | | | | |
+-+---+-+ +--+--+-+ +-+---+-+ +---+-+-+
Level 3 | | | | | | | |
|Leaf111| |Leaf112| |Leaf121| |Leaf122|
+-+-----+ ++------+ +-----+-+ +-+-----+
+ + + +
Prefix111 Prefix112 Prefix121 Prefix122
1.1/16
Figure 37: Fabric Partition
Figure 37 shows one of more catastrophic scenarios scenario where ToF 21 is completely
severed from access to Prefix 121 due to a double link failure. If
only default routes existed, this would result in 50% of traffic from
Leaf 111 and Leaf 112 toward towards Prefix 121 being dropped.
The mechanism to resolve this scenario hinges on ToF 21's South TIEs
being reflected from Spine 111 and Spine 112 to ToF 22. Once ToF 22
is informed that Prefix 121 cannot be reached from ToF 21, it will
begin to disaggregate Prefix 121 by advertising a more specific route
(1.1/16)
(1.1/16), along with the default IP prefix route to all spines (ToF
21 still only sends a default route). The result is Spine 111 and
Spine112
Spine 112 using the more specific route to Prefix 121 via ToF 22.
All other prefixes continue to use the default IP prefix route toward
towards both ToF 21 and ToF 22.
The more specific route for Prefix 121 being advertised by ToF 22
does not need to be propagated further south to the leaves, as they
do not benefit from this information. Spine 111 and Spine 112 are
only required to reflect the new South Node TIEs received from ToF 22
to ToF 21. In short, only the relevant nodes received the relevant
updates, thereby restricting the failure to only the partitioned
level rather than burdening the whole fabric with the flooding and
recomputation of the new topology information.
To finish this example, the following table list shows sets computed by ToF
22 using notation introduced in Section 6.5:
|R
* R = Prefix 111, Prefix 112, Prefix 121, Prefix 122
|H
* H (for r=Prefix 111) = Spine 111, Spine 112
|H
* H (for r=Prefix 112) = Spine 111, Spine 112
|H
* H (for r=Prefix 121) = Spine 121, Spine 122
|H
* H (for r=Prefix 122) = Spine 121, Spine 122
|A
* A (for ToF 21) = Spine 111, Spine 112
With that and |H (for r=Prefix 121) and |H (for r=Prefix 122) being
disjoint from |A (for ToF 21), ToF 22 will originate a South TIE with
Prefix 121 and Prefix 122, which will be flooded to all spines.
B.4. Northbound Partitioned Router and Optional East-West Links
+ + +
X N1 | N2 | N3
X | |
+--+----+ +--+----+ +--+-----+
| |0/0> <0/0| |0/0> <0/0| |
| A01 +----------+ A02 +----------+ A03 | Level 1
++-+-+--+ ++--+--++ +---+-+-++
| | | | | | | | |
| | +----------------------------------+ | | |
| | | | | | | | |
| +-------------+ | | | +--------------+ |
| | | | | | | | |
| +----------------+ | +-----------------+ |
| | | | | | | | |
| | +------------------------------------+ | |
| | | | | | | | |
++-+-+--+ | +---+---+ | +-+---+-++
| | +-+ +-+ | |
| L01 | | L02 | | L03 | Level 0
+-------+ +-------+ +--------+
Figure 38: North Partitioned Router
Figure 38 shows a part of a fabric where level 1 is horizontally
connected and A01 lost its only northbound adjacency. Based on N-SPF
rules in Section 6.4.1 6.4.1, A01 will compute northbound reachability by
using the link A01 to A02. However, A02 however, will *not* use this link
during N-SPF. The result is A01 utilizing the horizontal link for
default route advertisement and unidirectional routing.
Furthermore, if A02 also loses its only northbound adjacency (N2),
the situation evolves. A01 will no longer have northbound
reachability while it receives A03's northbound adjacencies in South
Node TIEs reflected by nodes south of it. As a result, A01 will no
longer advertise its default route in accordance with Section 6.3.8.
Acknowledgments
A new routing protocol in its complexity is not a product of a parent
but of a village, as the author list already shows. However, many
more people provided input and fine-combed the specification based on
their experience in design, implementation, or application of
protocols in IP fabrics. This section will make an inadequate
attempt in recording their contribution.
Many thanks to Naiming Shen for some of the early discussions around
the topic of using IGPs for routing in topologies related to Clos.
Russ White is especially acknowledged for the key conversation on
epistemology that tied the current asynchronous distributed systems
theory results to a modern protocol design presented in this scope.
Adrian Farrel, Joel Halpern, Jeffrey Zhang, Krzysztof Szarkowicz,
Nagendra Kumar, Melchior Aelmans, Kaushal Tank, Will Jones, Moin
Ahmed, Zheng (Sandy) Zhang, and Donald Eastlake provided thoughtful
comments that improved the readability of the document and found a
good amount of corners where the light failed to shine. Kris Price
was first to mention single router, single arm default
considerations. Jeff Tantsura helped out with some initial thoughts
on BFD interactions while Jeff Haas corrected several misconceptions
about BFD's finer points and helped to improve the security section
around leaf considerations. Artur Makutunowicz pointed out many
possible improvements and acted as a sounding board in regard to
modern protocol implementation techniques RIFT is exploring. Barak
Gafni formalized the problem of partitioned spine and fallen leaves
for the first time clearly on a (clean) napkin in Singapore that led
to the very important part of the specification centered around
multiple ToF planes and negative disaggregation. Igor Gashinsky and
others shared many thoughts on problems encountered in design and
operation of large-scale data center fabrics. Xu Benchong found a
delicate error in the flooding procedures and a schema datatype size
mismatch.
Too many people to mention provided reviews from many directions in
IETF, often pointing to critical defects, sometimes asking for things
again that have been removed by one of the previous reviewers as
objectionable or superfluous, and many times claiming the document
being somewhere on the extremes between too crowded with the obvious
and omitting introduction to cryptic concepts everywhere. The result
is the best editors could do to find a balance of a document guiding
the reader by Section 2 into a specification tight enough to result
in interoperable implementations while at the same time introducing
enough operational context of IP routable fabrics to guarantee a
concise, common language when facing unaccustomed concepts the
protocol relies on. In the process, it was important to not end up
carrying Aesop's donkey of course, so while the result may not be
perceived as perfect by everyone, it should be practically speaking
more than sufficient for everyone that ends up using it in the
future.
Last but not least, Alvaro Retana, John Scudder, Andrew Alston, and
Jim Guichard guided the undertaking as ADs by asking many necessary
procedural and technical questions that did not only improve the
content but also laid out the track towards publication. And Roman
Danyliw is mentioned very last but not least for both his
painstakingly detailed review and improvement of security aspects of
the specification.
Contributors
This work is a product of a list of individuals who are all to be
considered major contributors, independent of the fact whether or not
their name made it to the limited author list.
Tony Przygienda, Ed.
Juniper
Pascal Thubert
Cisco
Bruno Rijsman
Individual
Jordan Head, Ed.
Juniper
Dmitry Afanasiev
Individual
Don Fedyk
LabN
Alia Atlas
Individual
John Drake
Individual
Ilya Vershkov
Nvidia
Authors' Addresses
Tony Przygienda (editor)
Juniper Networks
1137 Innovation Way
Sunnyvale, CA 94089
United States of America
Email: prz@juniper.net
Jordan Head (editor)
Juniper Networks
1137 Innovation Way
Sunnyvale, CA 94089
United States of America
Email: jhead@juniper.net
Alankar Sharma
Hudson River Trading
United States of America
Email: as3957@gmail.com
Pascal Thubert
Individual
France
Email: pascal.thubert@gmail.com
Bruno Rijsman
Individual
Email: brunorijsman@gmail.com
Dmitry Afanasiev
Yandex
Email: fl0w@yandex-team.ru