wdiff rfc9764.original rfc9764.txt

Network Working Group

Internet Engineering Task Force (IETF) J. Haas
Internet-Draft
Request for Comments: 9764 Juniper Networks, Inc.
Intended status:
Category: Standards Track A. Fu
Expires: 19 July 2025
ISSN: 2070-1721 Bloomberg L.P.
15 January
April 2025

BFD

Bidirectional Forwarding Detection (BFD) Encapsulated in Large Packets
draft-ietf-bfd-large-packets-16

Abstract

The Bidirectional Forwarding Detection (BFD) protocol is commonly
used to verify connectivity between two systems. BFD packets are
typically very small. It is desirable in some circumstances to know
that
not only is that the path between two systems is reachable, but also
that it is capable of carrying a payload of a particular size. This
document specifies how to implement such a mechanism using BFD in
Asynchronous mode.

YANG modules for managing this mechanism are also defined in this
document. These YANG modules augment the existing BFD YANG modules
defined in RFC 9314. The YANG modules in this document conform to
the Network Management Datastore Architecture (NMDA) (RFC 8342).

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.

This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
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 six months RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be updated, replaced, or obsoleted by other documents obtained at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on 19 July 2025.
https://www.rfc-editor.org/info/rfc9764.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info)
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Revised BSD License text as described in Section 4.e of the
Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. BFD Encapsulated in Large Packets . . . . . . . . . . . . . . 3
4. Implementation and Deployment Considerations . . . . . . . . 3
4.1. Implementations that do not support That Do Not Support Large BFD Packets . . 4
4.2. Selecting MTU size to be detected . . . . . . . . . . . . 4 Size To Be Detected
4.3. Detecting MTU Mismatches . . . . . . . . . . . . . . . . 5
4.4. Detecting MTU Changes . . . . . . . . . . . . . . . . . . 5
4.5. Equal Cost Multiple Paths Equal-Cost Multipath (ECMP) or other Load Balancing Other Load-Balancing
Considerations . . . . . . . . . . . . . . . . . . . . . 5
4.6. S-BFD . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. BFD Encapsulated in Large Packets YANG Module . . . . . . . . 6
5.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 6
5.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6.1. YANG Security Considerations . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. The "IETF XML" Registry . . . . . . . . . . . . . . . . . 12
7.2. The "YANG Module Names" Registry . . . . . . . . . . . . 12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
9. References
8.1. Normative References . . . . . . . . . . . . . . . . . . . . 13
10.
8.2. Informative References . . . . . . . . . . . . . . . . . . . 14
Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15

1. Introduction

The Bidirectional Forwarding Detection (BFD) [RFC5880] protocol is
commonly used to verify connectivity between two systems. However,
some applications may require that the Path MTU [RFC1191] between
those two systems meets a certain minimum criterion. When the Path
MTU decreases below the minimum threshold, those applications may
wish to consider the path unusable.

BFD may be encapsulated in a number of transport protocols. An
example of this is single-hop BFD [RFC5881]. In that case, the link MTU
configuration is typically enough to guarantee communication between
the two systems for that size MTU. BFD Echo mode (Section 6.4 of
[RFC5880]) is sufficient to permit verification of the Path MTU of
such directly connected systems. Previous proposals
([I-D.haas-xiao-bfd-echo-path-mtu]) (e.g.,
[BFD-ECHO-PATH-MTU]) have been made for testing Path MTU for such
directly connected systems. However, in the case of
multi-hop multihop BFD
[RFC5883], this guarantee does not hold.

The encapsulation of BFD in multi-hop multihop sessions is a simple UDP packet.
The BFD elements of procedure (Section 6.8.6 of [RFC5880])
covers cover
validating the BFD payload. However, the specification is silent on
the length of the encapsulation that is carrying the BFD PDU. While
it is most common that the transport protocol payload (i.e., UDP)
length is the exact size of the BFD PDU, this is not required by the
elements of procedure. This leads to the possibility that the
transport protocol length may be larger than the contained BFD PDU.

2. 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.

3. BFD Encapsulated in Large Packets

Support for BFD between two systems is typically configured, even if
the actual session may be dynamically created by a client protocol.
A new BFD variable is defined in this document:

bfd.PaddedPduSize
The BFD transport protocol payload size (in bytes) is increased to
this value. The contents of this additional payload MUST be zero.
The contents of this additional payload SHOULD NOT be validated by
the receiver. The minimum size of this variable MUST NOT be
smaller than 24 or 26 bytes, as permitted by the element of BFD
procedure; 24 or 26 - see Section 6.8.6 of [RFC5880].

The Don't Fragment bit (Section 2.3 of [RFC0791]) of the IP payload,
when using IPv4 encapsulation, MUST be set.

4. Implementation and Deployment Considerations

4.1. Implementations that do not support That Do Not Support Large BFD Packets

While this document proposes no change to the BFD protocol,
implementations may not permit arbitrarily padded transport PDUs to
carry BFD packets. While Section 6 of [RFC5880] warns against
excessive pedantry, implementations may not work with this mechanism
without additional support.

[RFC5880], section 6.8.6,

Section 6.8.6 of [RFC5880] discusses the procedures for receiving BFD
Control packets. The length of the BFD Control packet is validated
to be less than or equal to the payload of the encapsulating
protocol. When a receiving implementation is incapable of processing
Large
large BFD Packets, packets, it could manifest in one of two possible ways:

* A receiving BFD implementation is incapable of accepting Large large BFD
Packets.
packets. This is identical to the packet being discarded.

* A receiving BFD implementation is capable of accepting Large large BFD
Packets,
packets, but the Control packet is improperly rejected during
validation procedures. This is identical to the packet being
discarded.

In each of these cases, the BFD state machine would behave as if it
were not receiving Control packets packets, and the receiving implementation
would follow normal BFD procedures regarding not having received
control
Control packets.

If Large large BFD Packets packets is enabled on a session that is already in the
Up state and the remote BFD system does not, or cannot not (or cannot) support
receiving the padded BFD control packets, the session will go Down.

4.2. Selecting MTU size to be detected Size To Be Detected

Since the consideration is path Path MTU, BFD sessions using this feature
only need to use an appropriate value of bfd.PaddedPduSize
appropriate to
exercise the path Path MTU for the desired application. This may be
significantly smaller than the system's link MTU; MTU, e.g., desired path Path
MTU is 1512 bytes bytes, while the interface MTU that BFD with large
packets is running on is 9000 bytes.

In the case multiple BFD clients desire to test the same BFD
endpoints using different bfd.PaddedPduSize parameters,
implementations SHOULD select the largest bfd.PaddedPduSize parameter
from the configured sessions. This is similar to how implementations
of BFD select the most aggressive timing parameters for multiple
sessions to the same endpoint. Failure to select the largest size
will result in BFD sessions going to the Up state and dependent
applications not having their MTU requirements satisfied.

4.3. Detecting MTU Mismatches

The accepted MTU for an interface is impacted by packet encapsulation
considerations at a given layer; layer, e.g., layer Layer 2, layer Layer 3, tunnel, etc.
A common misconfiguration of interface parameters is inconsistent
MTU. In the presence of inconsistent MTU, it is possible for
applications to have unidirectional connectivity.

When it is necessary for an application using BFD with Large Packets
to test the bi-directional bidirectional Path MTU, it is necessary to configure the
bfd.PaddedPduSize parameter on each side of the BFD session. E.g., For
example, if the desire is to verify a 1500 byte 1500-byte MTU in both
directions on an Ethernet or point to point point-to-point link, each side of the
BFD session must have bfd.PaddedPduSize set to 1500. In the absence
of such consistent configuration, BFD with Large Packets may
correctly determine unidirectional connectivity at the tested MTU,
but bi-
directional bidirectional MTU may not be properly validated.

It should be noted that some interfaces may intentionally have
different MTUs. Setting the bfd.PaddedPduSize appropriately for each
side of the BFD session supports such scenarios.

4.4. Detecting MTU Changes

Once BFD sessions using Large Packets has reached the Up state,
connectivity at the tested MTU(s) for the session is being validated.
If the path Path MTU tested by the BFD with Large Packets session falls
below the tested MTU, the BFD session will go Down.

In the opposite circumstance where (where the path Path MTU increases, increases), the BFD
session will continue without being impacted. BFD for Large Packets
only ensures that the minimally acceptable MTU for the session can be
used.

4.5. Equal Cost Multiple Paths Equal-Cost Multipath (ECMP) or other Load Balancing Other Load-Balancing Considerations

Various mechanisms are utilized to increase throughput between two
endpoints at various network layers. Such features include Link
Aggregate
Aggregation Groups (LAGs) or ECMP forwarding. Such mechanisms
balance traffic across multiple physical links while hiding the
details of that balancing from the higher networking layers. The
details of that balancing are highly implementation specific.

In the presence of such load balancing load-balancing mechanisms, it is possible to
have member links that are not properly forwarding traffic. In such
circumstances, this will result in dropped traffic when traffic is
chosen to be load balanced across those member links.

Such load balancing load-balancing mechanisms may not permit all link members to be
properly tested by BFD. This is because the BFD Control packets may
be forwarded only along links that are up. BFD on LAG, LAG interfaces,
[RFC7130], was developed to help cover one such scenario. However,
for testing forwarding over multiple hops, there is no such specified general
purpose
general-purpose BFD mechanism for exercising all links in an ECMP.
This may result in a BFD session being in the Up state while some
traffic may be dropped or otherwise negatively impacted along some
component links.

Some BFD implementations utilize their internal understanding of the
component links and their resultant forwarding to exercise BFD in
such a way to better test the ECMP members and to tie the BFD session
state to the health of that ECMP. Due to the implementation specific implementation-specific
load balancing, it is not possible to standardize such additional
mechanisms for BFD.

Misconfiguration of some member MTUs may lead to Load Balancing load balancing that
may have an inconsistent Path MTU depending on how the traffic is
balanced. While the intent of BFD with Large Packets large packets is to verify
path
Path MTU, it is subject to the same considerations above.

The above text also applies to most, if not all, BFD techniques.

4.6. S-BFD

This mechanism also can be applied to other forms of BFD, including
S-BFD
Seamless BFD (S-BFD) [RFC7880].

5. BFD Encapsulated in Large Packets YANG Module

5.1. Data Model Overview

This YANG module augments the "ietf-bfd" module to add a flag
'padding' to enable this feature. The feature statement 'padding'
needs to be enabled to indicate that BFD Encapsulated encapsulated in Large Packet large
packets is supported by the implementation.

Further, this YANG module augments the YANG modules for single-hop,
multi-hop,
multihop, LAG, and MPLS to add the "pdu-size" parameter to those
session types to configure Large large BFD packets.

Finally, similar to the grouping "client-cfg-parms" defined in
Section 2.1 of [RFC9314], this YANG module defines a grouping "bfd-
large-common" that may be utilized by BFD clients using "client-cfg-
params" to uniformly add support for the feature defined in this RFC.

module: ietf-bfd-large

augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
/bfd-ip-sh:sessions/bfd-ip-sh:session:
+--rw pdu-size? padded-pdu-size {padding}?
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-mh:ip-mh
/bfd-ip-mh:session-groups/bfd-ip-mh:session-group:
+--rw pdu-size? padded-pdu-size {padding}?
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-lag:lag
/bfd-lag:sessions/bfd-lag:session:
+--rw pdu-size? padded-pdu-size {padding}?
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls
/bfd-mpls:session-groups/bfd-mpls:session-group:
+--rw pdu-size? padded-pdu-size {padding}?

Figure 1

5.2. YANG Module

This YANG module imports A "A YANG Data Model for Routing [RFC8349], Management
(NMDA Version)" [RFC8349] and
YANG "YANG Data Model for Bidirectional Forwading
Forwarding Detection (BFD) (BFD)" [RFC9314].

<CODE BEGINS> file "ietf-bfd-large@2025-01-15.yang" "ietf-bfd-large@2025-03-31.yang"
module ietf-bfd-large {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-large";
prefix "bfdl"; bfdl;

import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA version)";
}

import ietf-bfd {
prefix bfd;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection.";
}

import ietf-bfd-ip-sh {
prefix bfd-ip-sh;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection.";
}

import ietf-bfd-ip-mh {
prefix bfd-ip-mh;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection.";
}

import ietf-bfd-lag {
prefix bfd-lag;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection.";
}

import ietf-bfd-mpls {
prefix bfd-mpls;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection.";
}

organization
"IETF BFD Working Group";

contact
"WG Web: <https://datatracker.ietf.org/wg/bfd>
WG List: <rtg-bfd@ietf.org>

Authors: Jeffrey Haas (jhaas@juniper.net)
Albert Fu (afu14@bloomberg.net).";

description
"This YANG module augments the base BFD YANG module to add
attributes related to support for BFD Encapsulated in Large
Packets. In particular, it adds a per-session parameter for the
BFD Padded PDU Size.

Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Revised BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).

This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); 9764
(https://www.rfc-editor.org/info/rfc9764); see the RFC itself
for full legal notices.

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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";

revision "2025-01-15" 2025-03-31 {
description
"Initial Version.";
reference
"RFC XXXX, BFD 9764, Bidirectional Forwarding Detection (BFD)
Encapsulated in Large Packets.";
}

feature padding {
description
"If supported, the feature allows for BFD sessions to be
configured with padded PDUs in support of BFD Encapsulated in
Large Packets.";
}

typedef padded-pdu-size {
type uint16 {
range "24..65535";
}
units "bytes";
description
"The size of the padded and encapsulated BFD control packets
to be transmitted at layer Layer 3. The BFD minimum control packet
size is 24 or 26 octets; see Section 6.8.6 of RFC 5880.

If the configured padded PDU size is smaller than the minimum
sized packet of a given BFD session, then the minimum sized
packet for the session will be used.

The maximum padded PDU size may be limited by the supported
interface MTU of the system.";
reference
"RFC XXXX, BFD 9764, Bidirectional Forwarding Detection (BFD)
Encapsulated in Large Packets.";
}

grouping bfd-large-common {
description
"Common configuration and operational state for BFD
Encapsulated in Large Packets.";
reference
"RFC XXXX, BFD 9764, Bidirectional Forwarding Detection (BFD)
Encapsulated in Large Packets.";
leaf pdu-size {
if-feature "padding";
type padded-pdu-size;
description
"If set, this configures the padded PDU size for the
Asynchronous mode BFD session. By default, no additional
padding is added to such packets.";
}
}

augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
+ "bfd-ip-sh:sessions/bfd-ip-sh:session" {
uses bfd-large-common;
description
"Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets.";
}

augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-ip-mh:ip-mh/"
+ "bfd-ip-mh:session-groups/bfd-ip-mh:session-group" {
uses bfd-large-common;
description
"Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets.";
}

augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-lag:lag/"
+ "bfd-lag:sessions/bfd-lag:session" {
uses bfd-large-common;
description
"Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets.";
}

augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls/"
+ "bfd-mpls:session-groups/bfd-mpls:session-group" {
uses bfd-large-common;
description
"Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets.";
}
}
<CODE ENDS>

Figure 2

6. Security Considerations

This document does not change the underlying security considerations
of the BFD protocol or its encapsulations.

On-path attackers that can selectively drop BFD packets, including
those with large MTUs, can cause BFD sessions to go Down.

The contents of the padding payload are set to zero. This avoids
implementation issues where the local uninitialized data may be
leaked.

6.1. YANG Security Considerations

This section is modeled after the template described in Section 3.7
of [I-D.ietf-netmod-rfc8407bis]. [YANG-GUIDELINES].

The "ietf-bfd-large" YANG module defines a data model that is
designed to be accessed via YANG-based management protocols, such as
NETCONF [RFC6241] and RESTCONF [RFC8040]. These protocols have to
use a secure transport layer (e.g., SSH [RFC4252], TLS [RFC8446], and
QUIC [RFC9000]) and have to use mutual authentication.

The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.

There is one data node defined in this YANG module that is
writable/creatable/deletable (i.e., "config true", which is the
default). All writable data nodes are likely to be reasonably
sensitive or vulnerable in some network environments. Write
operations (e.g., edit-config) and delete operations to these data
nodes without proper protection or authentication can have a negative
effect on network operations. The data node has particular
sensitivities/vulnerabilities:

* 'pdu-size' specifies the targeted size of BFD control packets
encapsulated according to this proposal. Changing this value for
a session in the Up state may cause the session to go down,
perhaps intentionally, if the session cannot accommodate such BFD
control packets. Operators should be mindful that multiple BFD
clients may rely on the status of a given BFD session when
changing this value.

There are no particularly sensitive readable data nodes.

There are no particularly sensitive RPC or action operations.

Modules that use the groupings that are defined in this document
should identify the corresponding security considerations. This
module defines one such grouping, "bfd-large-common", which contains
the "pdu-size" data node whose security considerations are documented
above.

7. IANA Considerations

7.1. The "IETF XML" Registry

This document registers one URIs

IANA has registered the following URI in the "ns" subregistry of the
"IETF
XML" registry XML Registry" [RFC3688]. Following the format in [RFC3688], the
following registration is requested:

URI: urn:ietf:params:xml:ns:yang:ietf-bfd-large
Registrant Contact: The IESG
XML: N/A, N/A; the requested URI is an XML namespace.

Figure 3

7.2. The "YANG Module Names" Registry

This document registers one

IANA has registered the following YANG modules module in the "YANG Module
Names" registry [RFC6020]. Following the format in [RFC6020], the following
registrations are requested:

name:

Name: ietf-bfd-large
namespace:
Maintained by IANA: N
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-large
prefix:
Prefix: bfdl
reference:
Reference: RFC XXXX

Figure 4 9764

8. Acknowledgments

The authors would like to thank Les Ginsberg, Mahesh Jethanandani,
Robert Raszuk, and Ketan Talaulikar, for their valuable feedback on
this proposal.

9. References

8.1. Normative References

[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.

[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>.

[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.

[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>.

[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>.

[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
June 2010, <https://www.rfc-editor.org/info/rfc5883>.

[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.

[RFC7130] Bhatia, M., Ed., Chen, M., Ed., Boutros, S., Ed.,
Binderberger, M., Ed., and J. Haas, Ed., "Bidirectional
Forwarding Detection (BFD) on Link Aggregation Group (LAG)
Interfaces", RFC 7130, DOI 10.17487/RFC7130, February
2014, <https://www.rfc-editor.org/info/rfc7130>.

[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
Pallagatti, "Seamless Bidirectional Forwarding Detection
(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
<https://www.rfc-editor.org/info/rfc7880>.

[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>.

[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.

[RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
Routing Management (NMDA Version)", RFC 8349,
DOI 10.17487/RFC8349, March 2018,
<https://www.rfc-editor.org/info/rfc8349>.

[RFC9314] Jethanandani, M., Ed., Rahman, R., Ed., Zheng, L., Ed.,
Pallagatti, S., and G. Mirsky, "YANG Data Model for
Bidirectional Forwarding Detection (BFD)", RFC 9314,
DOI 10.17487/RFC9314, September 2022,
<https://www.rfc-editor.org/info/rfc9314>.

10.

8.2. Informative References

[I-D.haas-xiao-bfd-echo-path-mtu]

[BFD-ECHO-PATH-MTU]
Min, X. X., Ed. and J. Haas, Ed., "Application of the BFD
Echo function for Path MTU Verification or Detection",
Work in Progress, Internet-Draft, draft-haas-xiao-bfd-
echo-path-mtu-01, 11 July 2011, <https://datatracker.ietf.org/doc/html/draft-
haas-xiao-bfd-echo-path-mtu-01>.

[I-D.ietf-netmod-rfc8407bis]
Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
Authors and Reviewers of Documents Containing YANG Data
Models", Work in Progress, Internet-Draft, draft-ietf-
netmod-rfc8407bis-22, 14 January 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
rfc8407bis-22>.
<https://datatracker.ietf.org/doc/html/draft-haas-xiao-
bfd-echo-path-mtu-01>.

[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/info/rfc1191>.

[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, <https://www.rfc-editor.org/info/rfc4252>.

[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.

[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.

[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.

[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.

[YANG-GUIDELINES]
Bierman, A., Boucadair, M., Ed., and Q. Wu, "Guidelines
for Authors and Reviewers of Documents Containing YANG
Data Models", Work in Progress, Internet-Draft, draft-
ietf-netmod-rfc8407bis-22, 14 January 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
rfc8407bis-22>.

Acknowledgments

The authors would like to thank Les Ginsberg, Mahesh Jethanandani,
Robert Raszuk, and Ketan Talaulikar, for their valuable feedback on
this proposal.

Authors' Addresses

Jeffrey Haas
Juniper Networks, Inc.
1133 Innovation Way
Sunnyvale, CA 94089
United States of America
Email: jhaas@juniper.net

Albert Fu
Bloomberg L.P.
731 Lexington Avenue
New York, NY 10022
United States of America
Email: afu14@bloomberg.net