wdiff rfc9703.original rfc9703.txt

Routing area

Internet Engineering Task Force (IETF) S. Hegde
Internet-Draft
Request for Comments: 9703 M. Srivastava
Intended status:
Category: Standards Track Juniper Networks Inc.
Expires: 29 January 2025
ISSN: 2070-1721 K. Arora
Individual Contributor
S. Ninan
Ciena
X. Xu
China Mobile
28 July
December 2024

Label Switched Path (LSP) Ping/Traceroute for Segment Routing (SR)
Egress Peer Engineering (EPE) Segment Identifiers (SIDs) with MPLS Data Plane
draft-ietf-mpls-sr-epe-oam-19
Planes

Abstract

Egress Peer Engineering (EPE) is an application of Segment Routing to
solve
(SR) that solves the problem of egress peer selection. The Segment Routing
based SR-based
BGP-EPE solution allows a centralized controller, e.g. e.g., a
Software Software-
Defined Network (SDN) controller controller, to program any egress peer. The
EPE solution requires the node or the SDN controller to program 1)
the PeerNode Segment Identifier(SID) Identifier (SID) describing a session between
two nodes, 2) the PeerAdj SID describing the link (one or more) links that is are
used by the sessions between peer nodes, and 3) the PeerSet SID
describing any connected interface to any peer in the related group.
This document provides new sub-TLVs for EPE Segment Identifiers (SID) EPE-SIDs that would be are used in the
MPLS Target stack TLV (Type 1), 1) in MPLS Ping and Traceroute
procedures.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents an Internet Standards Track document.

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(IETF). Note that other groups may also distribute
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Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid the IETF community. It has
received public review and has been approved for a maximum publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of six months this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
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This Internet-Draft will expire on 29 January 2025.
https://www.rfc-editor.org/info/rfc9703.

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in the Revised BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
4. FEC Definitions . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. PeerNode SID Sub-TLV . . . . . . . . . . . . . . . . . . 5
4.2. PeerAdj SID Sub-TLV . . . . . . . . . . . . . . . . . . . 7
4.3. PeerSet SID Sub-TLV . . . . . . . . . . . . . . . . . . . 9
5. EPE-SID FEC validation . . . . . . . . . . . . . . . . . . . 11 Validation
5.1. EPE-SID FEC validiation . . . . . . . . . . . . . . . . . 11 Validation
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 14
8.1. Juniper Networks . . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1.
8.1. Normative References . . . . . . . . . . . . . . . . . . 15
10.2.
8.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. APPENDIX . . . . . . . . . . . . . . . . . . . . . . 17 Appendix
Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18

1. Introduction

Egress Peer Engineering (EPE) (EPE), as defined in [RFC9087] [RFC9087], is an
effective mechanism that is used to select the egress peer link based
on different criteria. In this scenario, egress peers may belong to
a completely different ownership. The EPE-SIDs provide the means to
represent egress peer nodes, links, sets of links links, and sets of nodes.
Many network deployments have built their networks consisting of
multiple Autonomous Systems, Systems (ASes) either for the ease of operations
or as a result of network mergers and acquisitions. The inter-AS
links connecting any two Autonomous Systems ASes could be traffic-engineered using EPE-SIDs EPE-
SIDs in this case, where there is single ownership but different AS
numbers. It is important to validate the control plane to forwarding
plane synchronization for these SIDs so that any anomaly can be
detected
easily detected by the network operator. EPE-SIDs may also be used
in an ingress SR Segment Routing (SR) policy [RFC9256]to [RFC9256] to choose exit
points where the remote AS belongs to has a completely different ownership.
This scenario is out of scope of for this document.

+---------+ +------+
| | | |
| H B------D G
| | +---/| AS 2 AS2 |\ +------+
| |/ +------+ \ | |---L/8
A AS1 C---+ \| |
| |\\ \ +------+ /| AS 4 AS4 |---M/8
| | \\ +-E |/ +------+
| X | \\ | K
| | +===F AS 3 AS3 |
+---------+ +------+

Figure 1: Reference Diagram

In this reference diagram, Figure 1, EPE-SIDs are configured on AS1 towards AS2 and AS3 and
advertised in BGP-LS the Border Gateway Protocol - Link State (BGP-LS)
[RFC9086]. In certain cases cases, the EPE-SIDs advertised by the control
plane may not be in synchronization with the label programmed in the
data plane. For example, on C C, a PeerAdj SID could be advertised to
indicate it is for the link C->D. Due to some software anomaly, the
actual data forwarding on this PeerAdj SID could be happening over
the C->E link. If E had relevant data paths for further forwarding
the packet, this kind of anomaly will would go unnoticed by the network
operator. A detailed example of a correctly programmed state and an
incorrectly programmed state along with a description of how the
incorrect state can be detected is described in Appendix A. A FEC
Forwarding Equivalence Class (FEC) definition for the EPE-SIDs will define the details of
detail the control plane association of the SID. The data plane
validation of the SID will be done during the MPLS traceroute
procedure. When there is a multi-hop EBGP External BGP (EBGP) session
between the ASBRs, a PeerNode SID is advertised, and the traffic MAY
be load-balanced between the interfaces connecting the two nodes. In the reference diagram,
Figure 1, C and F could have a PeerNode- PeerNode SID advertised. When the OAM
Operations, Administration, and Maintenance (OAM) packet is received
on F, it needs to be validated that the packet came from one of the
two interfaces connected to C.

This document provides Target Forwarding Equivalence Class (FEC)
stack
Stack TLV definitions for EPE-SIDs. This solution requires that the node
constructing the target FEC stack can to determine the type types of the SIDs
along the path of the LSP. Other procedures for MPLS Ping and
Traceroute
Traceroute, as defined in [RFC8287] section Section 7 of [RFC8287] and clarified by
[RFC8690] in
[RFC8690], are applicable for EPE-SIDs as well.

2. Theory of Operation

[RFC9086] provides mechanisms to advertise the EPE-SIDs in BGP-LS.
These EPE-SIDs may be used to build Segment Routing SR paths as described in [I-D.ietf-idr-segment-routing-te-policy]
[SR-TE-POLICY] or using Path Computation Element Protocol (PCEP)
extensions as defined in [RFC8664]. Data plane monitoring for such
paths which that consist of EPE-SIDs will use extensions defined in this
document to build the Target FEC stack TLV. The MPLS Ping and
Traceroute procedures MAY be initiated by the head-end of the Segment Routing SR path
or a centralized topology-aware data plane monitoring system system, as
described in [RFC8403]. The extensions in
[I-D.ietf-idr-segment-routing-te-policy] [SR-TE-POLICY] and
[RFC8664] do not define how to carry the details of the SID that can
be used to construct the FEC. Such extensions are out of the scope for
this document. The node initiating the data plane monitoring may
acquire the details of EPE-SIDs through BGP-LS advertisements advertisements, as
described in [RFC9086]. There may be other possible mechanisms that
can be used to learn the definition of the SID from the controller.
Details of such mechanisms are out of scope for this document.

The EPE-SIDs are advertised for inter-AS links which that run EBGP
sessions. [RFC9086] does not define the detailed procedures of how
to operate EBGP sessions in a scenario with unnumbered interfaces.
Therefore, these scenarios are out of scope for this document.
Anycast and multicast addresses are not in the scope of this
document. During the AS migration scenario scenario, procedures described in
[RFC7705] may be in force. In these scenarios, if the local and
remote AS fields in the FEC as (as described in Section 4 carries 4) carry the
globally configured ASN Access Service Network (ASN) and not the "local
AS" as (as defined in
[RFC7705], [RFC7705]), then the FEC validation procedures may
fail.

As described in Section 1, this document defines FEC stack TLVs for
EPE-SIDs,
EPE-SIDs that can be used in detecting MPLS data plane failures
[RFC8029]. This mechanism applies to paths created across across ASes of co-operating
cooperating administrations. If the ping or traceroute packet enters
a non co-operating non-cooperating AS domain, it might be dropped by the routers in
the non co-operating non-cooperating domain. Although a complete path validation
cannot be done across, non co-operating across non-cooperating domains, it still provides
useful information that the ping/traceroute ping or traceroute packet entered a
non co-operating non-
cooperating domain.

3. 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.

4. FEC Definitions

Three

In this document, three new sub-TLVs are defined for the Target FEC
Stack TLV (Type 1), the Reverse-Path Target FEC Stack TLV (Type 16),
and the Reply Path TLV (Type 21).

+==========+==============+
| Sub-Type | Sub-TLV Name
-------- ---------------
TBD1 |
+==========+==============+
| 38 | PeerAdj SID Sub-TLV
TBD2 |
+----------+--------------+
| 39 | PeerNode SID Sub-TLV
TBD3 |
+----------+--------------+
| 40 | PeerSet SID Sub-TLV

Figure 2: |
+----------+--------------+

Table 1: New sub-TLV types Sub-TLV Types

4.1. PeerNode SID Sub-TLV

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = TBD2 39 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local BGP router Router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: 2: PeerNode SID Sub-TLV
Type :

Type: 2 octets

Value:TBD2

Length :

Value: 39

Length: 2 octets

Value: 16

Local AS Number : Number: 4 octets octets. The unsigned integer representing the AS
number [RFC6793] of the AS to which the PeerNode SID advertising
node belongs. If Confederations [RFC5065] are in use, and if the
remote node is a member of a different Member-AS within the local
Confederation, this is the Member-AS Number inside the
Confederation and not the Confederation Identifier.

Remote AS Number : Number: 4 octets octets. The unsigned integer representing the
AS number [RFC6793] of the AS of the remote node for which the
PeerNode SID is advertised. If Confederations [RFC5065] are in
use, and if the remote node is a member of a different Member-AS
within the local Confederation, this is the Member-AS Number
inside the Confederation and not the Confederation Identifier.

Local BGP Router ID : ID: 4 octets

unsigned octets. Unsigned integer representing the
BGP Identifier of the PeerNode SID advertising node as defined in
[RFC4271] and [RFC6286].

Remote BGP Router ID : ID: 4 octets

unsigned octets. Unsigned integer representing the
BGP Identifier of the remote node as defined in [RFC4271] and
[RFC6286].

When there is a multi-hop EBGP session between two ASBRs, a PeerNode
SID is advertised for this session session, and traffic can be load balanced load-balanced
across these interfaces. An EPE controller that does performs bandwidth
management for these links should be aware of the links on which the
traffic will be load-balanced. As per [RFC8029], the node
advertising the EPE SIDs EPE-SIDs will send a Downstream Detailed Mapping
(DDMAP) TLV
(DDMAP TLV) specifying the details of nexthop the next-hop interfaces, e.g,
when the OAM packet will be sent out. Based on this information information, the
controller MAY choose to verify the actual forwarding state with the
topology information that the controller has. On the router, the
validation procedures will include, include the received DDMAP validation validation, as
specified in [RFC8029] [RFC8029], to verify the control state and the
forwarding state synchronization on the two routers. Any
discrepancies between the controller's state and the forwarding state
will not be detected by the procedures described in the this document.

4.2. PeerAdj SID Sub-TLV

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = TBD1 38 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adj-Type | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local BGP router Router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface address Address (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface address Address (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: 3: PeerAdj SID Sub-TLV

Type :

Type: 2 octets

Value: TBD1

Length : 38

Length: 2 octets

Value: variable Variable based on the IPv4/IPv6 interface address. Length
excludes the length of the Type and Length fields.For fields. For IPv4
interface
addresses addresses, the length will be 28 octets. In the case of
an IPv6 address address, the length will be 52 octets.

Adj-Type :

Adj-Type: 1 octet

Value: Set to 1 when the Adjacency Segment is IPv4 IPv4. Set to 2 when
the Adjacency Segment is IPv6
RESERVED : IPv6.

RESERVED: 3 octets. MUST be zero when sending, sending and ignored on
receiving.

Local AS Number : Number: 4 octets octets. The unsigned integer representing the AS
number [RFC6793] of the AS to which the PeerAdj SID advertising
node belongs. If Confederations [RFC5065] are in use, and if the
remote node is a member of a different Member-AS within the local
Confederation, this is the Member-AS Number inside the
Confederation and not the Confederation Identifier.

Remote AS Number : Number: 4 octets octets. The unsigned integer representing the
AS number[RFC6793] of the AS number [RFC6793] of the remote node node's AS for which the PeerAdj
SID is advertised. If Confederations [RFC5065] are in use, and if
the remote node is a member of a different Member-AS within the
local Confederation, this is the Member-AS Number inside the
Confederation and not the Confederation Identifier.

Local BGP Router ID : ID: 4 octets octets. The unsigned integer representing
the BGP Identifier of the PeerAdj SID advertising node as defined
in [RFC4271] and [RFC6286].

Remote BGP Router ID : ID: 4 octets

unsigned octets. Unsigned integer representing the
BGP Identifier of the remote node as defined in [RFC4271] and
[RFC6286].

Local Interface Address :4 octets/16 Address: 4 octets or 16 octets. In the case of
PeerAdj SID, the Local interface address corresponding to the
PeerAdj SID should be specified in this field. For IPv4,this IPv4, this
field is 4 octets; for IPv6, this field is 16 octets. Link-local
IPv6 addresses are not in the scope of this document.

Remote Interface Address :4 octets/16 Address: 4 octets or 16 octets. In the case of
PeerAdj SID SID, the Remote interface address corresponding to the
PeerAdj SID should be apecified specified in this field. For IPv4, this
field is 4 octets; for IPv6, this field is 16 octets. Link-local
IPv6 addresses are not in the scope of this document.. document.

[RFC9086] mandates sending a local interface ID and remote interface
ID in the Link Descriptors and allows a value of 0 in the remote
descriptors. It is useful to validate the incoming interface for an
OAM packet and packet, but if the remote descriptor is 0 0, this validation is not
possible. [RFC9086] allows optional Optional link descriptors of local and remote interface
addresses are allowed as described in section 4.2. This
document RECOMMENDs sending Section 4.2 of [RFC9086]. In
this document, it is RECOMMENDED to send these optional descriptors
and using use them to validate incoming interface. interfaces. When these local and
remote interface addresses are not available, an ingress node can
send 0 in the local and/or remote interface address field. The
receiver SHOULD skip the validation for the incoming interface if the
address field contains 0.

4.3. PeerSet SID Sub-TLV

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type = TBD3 40 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local BGP router Router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| No.of elements in set | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++

One element in set consists of below the details below
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++

Figure 5: 4: PeerSet SID Sub-TLV
Type :

Type: 2 octets

Value: TBD3

Length : 40

Length: 2 octets

Value: Expressed in octets and variable based on the number of
elements in the set. The length field does not include the length
of Type and Length fields.

Local AS Number :4 octets Number: 4 octets. The unsigned integer representing the AS
number [RFC6793] of the AS to which the PeerSet SID advertising
node belongs. If Confederations [RFC5065] are in use, and if the
remote node is a member of a different Member-AS within the local
Confederation, this is the Member-AS Number inside the
Confederation and not the Confederation Identifier.

Local BGP Router ID : ID: 4 octets octets. The unsigned integer representing
the BGP Identifier of the PeerSet SID advertising node node, as defined
in [RFC4271] and [RFC6286].

No.of elements in set: 2 octets octets. The number of remote ASes over
which the set SID performs load
balancing.

Reserved : load-balancing.

Reserved: 2 octets. MUST be zero when sent and ignored when
received.

Remote AS Number : Number: 4 octets octets. The unsigned integer representing the
AS number [RFC6793] of the AS
of the remote node node's AS for which the PeerSet
SID is advertised. If Confederations [RFC5065] are in use, and if
the remote node is a member of a different Member-AS within the
local Confederation, this is the Member-AS Number inside the
Confederation and not the Confederation Identifier.

Remote BGP Router ID : ID: 4 octets octets. The unsigned integer representing
the BGP Identifier of the remote node as defined in [RFC4271] and
[RFC6286].

PeerSet SID may be associated with a number of PeerNode SIDs and
PeerAdj SIDs. The remote AS number and the Router ID of each of
these PeerNode SIDs and PeerAdj SIDs MUST be included in the FEC.

5. EPE-SID FEC validation Validation

When a remote ASBR of the EPE-SID advertisement receives the MPLS OAM
packet with the top FEC being the EPE-SID, it MUST perform validity
checks on the content of the EPE-SID FEC sub-TLV. The basic length
check should be performed on the received FEC.

PeerAdj SID
-----------
if
If Adj type = 1 1, Length should be 28 octets
If Adj type =2 = 2, Length should be 52 octets

PeerNode SID
-------------
Length = ( 20 (20 + No.of IPv4 interface pairs * 8 +
No.of IPv6 interface pairs * 32 ) 32) octets

PeerSet SID
-----------
Length = (9 + No.of elements in the set *
(8 + No.of IPv4 interface pairs * 8 +
No.of IPv6 interface pairs * 32)) 32) octets

Figure 6: 5: Length Validation

If a malformed FEC sub-TLV is received, then a return code of 1,
"Malformed echo request received" received", as defined in [RFC8029] MUST be
sent. The below section below is appended to the procedure given in step
4a of Section 7.4 point 4a of [RFC8287].

5.1. EPE-SID FEC validiation Validation

Segment Routing IGP-Prefix, IGP-Adjacency SID SID, and EPE-SID Validation
:
Validation: Receiving node term used in this section implies the node
that receives OAM message with the FEC stack TLV.

Else, if the Label-stack-depth is 0 and the Target FEC Stack sub-TLV
at FEC-stack-depth is TBD1 38 (PeerAdj SID sub-TLV), {

Set the Best-return-code to 10, "Mapping for this FEC is not
the given label at stack-depth if stack-depth". If any below conditions fail:

- Validate that the receiving node's BGP Local AS matches
with the remote AS field in the received PeerAdj SID
FEC sub-TLV.

- Validate that the receiving node's BGP Router-ID
matches with the Remote Router ID field in the
received PeerAdj SID FEC.

- Validate that there is a an EBGP session with a peer
having a local AS number and BGP Router-ID as
specified in the Local AS number and Local Router-ID
field in the received PeerAdj SID FEC sub-TLV.

If the Remote interface address is not zero, validate the
incoming interface. Set the Best-return-code to 35 35,
"Mapping for this FEC is not associated with the incoming
interface" [RFC8287] if [RFC8287]. If any below conditions fail:

- Validate that the incoming interface on which the
OAM packet was receieved, received matches with the remote
interface specified in the PeerAdj SID FEC sub-TLV sub-TLV.

If all above validations have passed, set the return code to 3 3,
"Replying router is an egress for the FEC at stack-depth" stack-depth".
}

Else, if the Target FEC sub-TLV at FEC-stack-depth is TBD2 39
(PeerNode SID sub-TLV), {

Set the Best-return-code to 10, "Mapping for this FEC is not
the given label at stack-depth if stack-depth". If any below conditions
fail:

- Validate that the receiving node's BGP Local AS matches
with the remote AS field in the received PeerNode SID
FEC sub-TLV.

- Validate that the receiving node's BGP Router-ID matches
with the Remote Router ID field in the received
PeerNode SID FEC.

- Validate that there is a an EBGP session with a peer
having a local AS number and BGP Router-ID as
specified in the Local AS number and Local Router-ID
field in the received PeerNode SID FEC sub-TLV.

If all above validations have passed, set the return code to 3 3,
"Replying router is an egress for the FEC at stack-depth".
}
Else, if the Target FEC sub-TLV at FEC-stack-depth is TBD3 40
(PeerSet SID sub-TLV), {

Set the Best-return-code to 10, "Mapping for this FEC is not
the given label at stack-depth" if stack-depth". If any below conditions
fail:

- Validate that the Receiving Node BGP Local AS matches
with one of the remote AS field fields in the received
PeerSet SID FEC sub-TLV.

- Validate that the Receiving Node BGP Router-ID matches
with one of the Remote Router ID field fields in the
received PeerSet SID FEC sub-TLV.

- Validate that there is a an EBGP session with a peer having
a local AS number and BGP Router-ID as specified in the
Local AS number and Local Router-ID
field fields in the received
PeerSet SID FEC sub-TLV.

If all above validations have passed, set the return code to 3 3,
"Replying router is an egress for the FEC at stack-depth" stack-depth".
}

6. IANA Considerations

IANA is requested to allocate has allocated three new Target FEC stack sub-TLVs
from in the "Sub-TLVs "Sub-
TLVs for TLV types 1,16 Types 1, 16, and 21" subregistry in registry within the "TLVs" registry
of the "Multi-Protocol "Multiprotocol Label switching Switching (MPLS) Label Switched Paths
(LSPs) Ping parameters" namespace. Parameters" registry group.

+==========+==============+
| Sub-Type | Sub-TLV Name |
+==========+==============+
| 38 | PeerAdj SID Sub-TLV : TBD1 |
+----------+--------------+
| 39 | PeerNode SID Sub-TLV: TBD2 |
+----------+--------------+
| 40 | PeerSet SID Sub-TLV : TBD3

The three lowest free values from the Standard Tracks range should be
allocated if possible. |
+----------+--------------+

Table 2: Sub-TLVs for
TLV Types 1, 16, and 21
Registry

7. Security Considerations

The EPE-SIDs are advertised for egress links for Egress Peer
Engineering EPE purposes or for
inter-AS links between co-operating cooperating ASes. When co-operating cooperating domains
are involved, they can allow the packets arriving on trusted
interfaces to reach the control plane and get be processed.

When EPE-SIDs are created for egress TE links where the neighbor AS
is an independent entity, it may not allow the packets arriving from
the external world to reach the control plane. In such deployments deployments,
the MPLS OAM packets will be dropped by the neighboring AS that
receives the MPLS OAM packet.

In MPLS traceroute applications, when the AS boundary is crossed with
the EPE-SIDs, the FEC stack is changed. [RFC8287] does not mandate
that the initiator initiator, upon receiving an MPLS Echo Reply message that
includes the FEC Stack Change TLV with one or more of the original
segments being popped popped, remove a the corresponding FEC(s) from the
Target FEC Stack TLV in the next (TTL+1) traceroute request.

If an initiator does not remove the FECs belonging to the previous AS
that has traversed, it may expose the internal AS information to the
following AS being traversed in the traceroute.

8. Implementation Status

This section is to be removed before publishing as an RFC.

RFC-Editor: Please clean up the references cited by this section
before publication.

This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.

8.1. Juniper Networks

Juniper networks reported a prototype implementation of this draft.

9. Acknowledgments

Thanks to Loa Andersson, Dhruv Dhody, Ketan Talaulikar, Italo Busi
and Alexander Vainshtein, Deepti Rathi for careful review and
comments. Thanks to Tarek Saad for providing the example described
in Appendix section.

10. References

10.1.

8.1. Normative References

[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>.

[RFC6793] Vohra, Q. and E. Chen, "BGP Support for Four-Octet
Autonomous System (AS) Number Space", RFC 6793,
DOI 10.17487/RFC6793, December 2012,
<https://www.rfc-editor.org/info/rfc6793>.

[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.

[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>.

[RFC8287] Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya,
N., Kini, S., and M. Chen, "Label Switched Path (LSP)
Ping/Traceroute for Segment Routing (SR) IGP-Prefix and
IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data
Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017,
<https://www.rfc-editor.org/info/rfc8287>.

[RFC8690] Nainar, N., Pignataro, C., Iqbal, F., and A. Vainshtein,
"Clarification of Segment ID Sub-TLV Length for RFC 8287",
RFC 8690, DOI 10.17487/RFC8690, December 2019,
<https://www.rfc-editor.org/info/rfc8690>.

[RFC9086] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Patel, K.,
Ray, S., and J. Dong, "Border Gateway Protocol - Link
State (BGP-LS) Extensions for Segment Routing BGP Egress
Peer Engineering", RFC 9086, DOI 10.17487/RFC9086, August
2021, <https://www.rfc-editor.org/info/rfc9086>.

10.2.

8.2. Informative References

[I-D.ietf-idr-segment-routing-te-policy]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
D. Jain, "Advertising Segment Routing Policies in BGP",
Work in Progress, Internet-Draft, draft-ietf-idr-segment-
routing-te-policy-26, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-26>.

[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.

[RFC5065] Traina, P., McPherson, D., and J. Scudder, "Autonomous
System Confederations for BGP", RFC 5065,
DOI 10.17487/RFC5065, August 2007,
<https://www.rfc-editor.org/info/rfc5065>.

[RFC6286] Chen, E. and J. Yuan, "Autonomous-System-Wide Unique BGP
Identifier for BGP-4", RFC 6286, DOI 10.17487/RFC6286,
June 2011, <https://www.rfc-editor.org/info/rfc6286>.

[RFC7705] George, W. and S. Amante, "Autonomous System Migration
Mechanisms and Their Effects on the BGP AS_PATH
Attribute", RFC 7705, DOI 10.17487/RFC7705, November 2015,
<https://www.rfc-editor.org/info/rfc7705>.

[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.

[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>.

[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.

[RFC9087] Filsfils, C., Ed., Previdi, S., Dawra, G., Ed., Aries, E.,
and D. Afanasiev, "Segment Routing Centralized BGP Egress
Peer Engineering", RFC 9087, DOI 10.17487/RFC9087, August
2021, <https://www.rfc-editor.org/info/rfc9087>.

[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.

[SR-TE-POLICY]
Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
D. Jain, "Advertising Segment Routing Policies in BGP",
Work in Progress, Internet-Draft, draft-ietf-idr-segment-
routing-te-policy-26, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
segment-routing-te-policy-26>.

Appendix A. APPENDIX Appendix

This section describes an example examples of both a correctly programmed state and an
incorrectly programmed state and provides details on how the new sub-
TLVs described in this document can be used to validate the
correctness. Consider the diagram from Figure 1, 1.

Correctly programed programmed state:

•

* C assigns label 16001 and binds it to adjacency C->E

•

* C signals that label 16001 is bound to adjacency C->E (e.g. (e.g., via BGP-
LS)

• Controller/Ingress
BGP-LS)

* The controller/ingress programs an SR path that has SID/label
16001 to steer the packet on the exit point from C onto adjacency
C->E

•

* Using MPLS trace procedures defined in this document, the PeerAdj
SID Sub-TLV is populates populated with entities to be validated by C when
the OAM packet reaches it.

• it

* C receives the OAM packet, it packet and validates that the top label (16001)
is indeed corresponding to the entities populated in the PeerAdj
SID Sub-TLV

Incorrectly programed programmed state:

•

* C assigns label 16001 and binds it to adjacency C->D

•

* The controller learns of that PeerAdj SID label 16001 is bound to
adjacency C->E (e.g. (e.g., via BGP-LS) – -- this could be a software bug
on C or on the controller
• Controller/Ingress

* The controller/ingress programs an SR path that has SID/label
16001 to steer the packet on the exit point from C onto adjacency
C->E

•

* Using MPLS trace procedures defined in this document, the PeerAdj
SID Sub-TLV is populates populated with entities to be validated by C
(including a local/remote interface address of C->E) when the OAM
packet reaches it.

• it

* C receives the OAM packet, it packet and validates that the top label (16001)
is NOT bound to C->E as populated in the PeerAdj SID Sub-TLV and can
respond
then responds with the respective error code

Acknowledgments

Thanks to Loa Andersson, Dhruv Dhody, Ketan Talaulikar, Italo Busi,
Alexander Vainshtein, and Deepti Rathi for careful reviews and
comments. Thanks to Tarek Saad for providing the example described
in Appendix A.

Authors' Addresses

Shraddha Hegde
Juniper Networks Inc.
Exora Business Park
Bangalore 560103
KA
Karnataka
India
Email: shraddha@juniper.net

Mukul Srivastava
Juniper Networks Inc.
Email: msri@juniper.net

Kapil Arora
Individual Contributor
Email: kapil.it@gmail.com

Samson Ninan
Ciena
Email: samson.cse@gmail.com

Xiaohu Xu
China Mobile
Beijing
China
Email: xuxiaohu_ietf@hotmail.com