rfc9764.original   rfc9764.txt 
Network Working Group J. Haas Internet Engineering Task Force (IETF) J. Haas
Internet-Draft Juniper Networks, Inc. Request for Comments: 9764 Juniper Networks, Inc.
Intended status: Standards Track A. Fu Category: Standards Track A. Fu
Expires: 19 July 2025 Bloomberg L.P. ISSN: 2070-1721 Bloomberg L.P.
15 January 2025 April 2025
BFD Encapsulated in Large Packets Bidirectional Forwarding Detection (BFD) Encapsulated in Large Packets
draft-ietf-bfd-large-packets-16
Abstract Abstract
The Bidirectional Forwarding Detection (BFD) protocol is commonly The Bidirectional Forwarding Detection (BFD) protocol is commonly
used to verify connectivity between two systems. BFD packets are used to verify connectivity between two systems. BFD packets are
typically very small. It is desirable in some circumstances to know typically very small. It is desirable in some circumstances to know
that not only is the path between two systems reachable, but also not only that the path between two systems is reachable, but also
that it is capable of carrying a payload of a particular size. This that it is capable of carrying a payload of a particular size. This
document specifies how to implement such a mechanism using BFD in document specifies how to implement such a mechanism using BFD in
Asynchronous mode. Asynchronous mode.
YANG modules for managing this mechanism are also defined in this YANG modules for managing this mechanism are also defined in this
document. These YANG modules augment the existing BFD YANG modules document. These YANG modules augment the existing BFD YANG modules
defined in RFC 9314. The YANG modules in this document conform to defined in RFC 9314. The YANG modules in this document conform to
the Network Management Datastore Architecture (NMDA) (RFC 8342). the Network Management Datastore Architecture (NMDA) (RFC 8342).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 19 July 2025. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9764.
Copyright Notice Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents
license-info) in effect on the date of publication of this document. (https://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. Code Components carefully, as they describe your rights and restrictions with respect
extracted from this document must include Revised BSD License text as to this document. Code Components extracted from this document must
described in Section 4.e of the Trust Legal Provisions and are include Revised BSD License text as described in Section 4.e of the
provided without warranty as described in the Revised BSD License. Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language
3. BFD Encapsulated in Large Packets . . . . . . . . . . . . . . 3 3. BFD Encapsulated in Large Packets
4. Implementation and Deployment Considerations . . . . . . . . 3 4. Implementation and Deployment Considerations
4.1. Implementations that do not support Large BFD Packets . . 4 4.1. Implementations That Do Not Support Large BFD Packets
4.2. Selecting MTU size to be detected . . . . . . . . . . . . 4 4.2. Selecting MTU Size To Be Detected
4.3. Detecting MTU Mismatches . . . . . . . . . . . . . . . . 5 4.3. Detecting MTU Mismatches
4.4. Detecting MTU Changes . . . . . . . . . . . . . . . . . . 5 4.4. Detecting MTU Changes
4.5. Equal Cost Multiple Paths (ECMP) or other Load Balancing 4.5. Equal-Cost Multipath (ECMP) or Other Load-Balancing
Considerations . . . . . . . . . . . . . . . . . . . . . 5 Considerations
4.6. S-BFD . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.6. S-BFD
5. BFD Encapsulated in Large Packets YANG Module . . . . . . . . 6 5. BFD Encapsulated in Large Packets YANG Module
5.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 6 5.1. Data Model Overview
5.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 7 5.2. YANG Module
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations
6.1. YANG Security Considerations . . . . . . . . . . . . . . 11 6.1. YANG Security Considerations
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations
7.1. The "IETF XML" Registry . . . . . . . . . . . . . . . . . 12 7.1. The "IETF XML" Registry
7.2. The "YANG Module Names" Registry . . . . . . . . . . . . 12 7.2. The "YANG Module Names" Registry
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 8. References
9. Normative References . . . . . . . . . . . . . . . . . . . . 13 8.1. Normative References
10. Informative References . . . . . . . . . . . . . . . . . . . 14 8.2. Informative References
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 Acknowledgments
Authors' Addresses
1. Introduction 1. Introduction
The Bidirectional Forwarding Detection (BFD) [RFC5880] protocol is The Bidirectional Forwarding Detection (BFD) [RFC5880] protocol is
commonly used to verify connectivity between two systems. However, commonly used to verify connectivity between two systems. However,
some applications may require that the Path MTU [RFC1191] between some applications may require that the Path MTU [RFC1191] between
those two systems meets a certain minimum criterion. When the Path those two systems meets a certain minimum criterion. When the Path
MTU decreases below the minimum threshold, those applications may MTU decreases below the minimum threshold, those applications may
wish to consider the path unusable. wish to consider the path unusable.
BFD may be encapsulated in a number of transport protocols. An BFD may be encapsulated in a number of transport protocols. An
example of this is single-hop BFD [RFC5881]. In that case, the link example is single-hop BFD [RFC5881]. In that case, the link MTU
MTU configuration is typically enough to guarantee communication configuration is typically enough to guarantee communication between
between the two systems for that size MTU. BFD Echo mode the two systems for that size MTU. BFD Echo mode (Section 6.4 of
(Section 6.4 of [RFC5880]) is sufficient to permit verification of [RFC5880]) is sufficient to permit verification of the Path MTU of
the Path MTU of such directly connected systems. Previous proposals such directly connected systems. Previous proposals (e.g.,
([I-D.haas-xiao-bfd-echo-path-mtu]) have been made for testing Path [BFD-ECHO-PATH-MTU]) have been made for testing Path MTU for such
MTU for such directly connected systems. However, in the case of directly connected systems. However, in the case of multihop BFD
multi-hop BFD [RFC5883], this guarantee does not hold. [RFC5883], this guarantee does not hold.
The encapsulation of BFD in multi-hop sessions is a simple UDP The encapsulation of BFD in multihop sessions is a simple UDP packet.
packet. The BFD elements of procedure (Section 6.8.6 of [RFC5880]) The BFD elements of procedure (Section 6.8.6 of [RFC5880]) cover
covers validating the BFD payload. However, the specification is validating the BFD payload. However, the specification is silent on
silent on the length of the encapsulation that is carrying the BFD the length of the encapsulation that is carrying the BFD PDU. While
PDU. While it is most common that the transport protocol payload it is most common that the transport protocol payload (i.e., UDP)
(i.e., UDP) length is the exact size of the BFD PDU, this is not length is the exact size of the BFD PDU, this is not required by the
required by the elements of procedure. This leads to the possibility elements of procedure. This leads to the possibility that the
that the transport protocol length may be larger than the contained transport protocol length may be larger than the contained BFD PDU.
BFD PDU.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. BFD Encapsulated in Large Packets 3. BFD Encapsulated in Large Packets
Support for BFD between two systems is typically configured, even if Support for BFD between two systems is typically configured, even if
the actual session may be dynamically created by a client protocol. the actual session may be dynamically created by a client protocol.
A new BFD variable is defined in this document: A new BFD variable is defined in this document:
bfd.PaddedPduSize bfd.PaddedPduSize
The BFD transport protocol payload size (in bytes) is increased to The BFD transport protocol payload size (in bytes) is increased to
this value. The contents of this additional payload MUST be zero. this value. The contents of this additional payload MUST be zero.
The contents of this additional payload SHOULD NOT be validated by The contents of this additional payload SHOULD NOT be validated by
the receiver. The minimum size of this variable MUST NOT be the receiver. The minimum size of this variable MUST NOT be
smaller than permitted by the element of BFD procedure; 24 or 26 - smaller than 24 or 26 bytes, as permitted by the element of BFD
see Section 6.8.6 of [RFC5880]. procedure; see Section 6.8.6 of [RFC5880].
The Don't Fragment bit (Section 2.3 of [RFC0791]) of the IP payload, The Don't Fragment bit (Section 2.3 of [RFC0791]) of the IP payload,
when using IPv4 encapsulation, MUST be set. when using IPv4 encapsulation, MUST be set.
4. Implementation and Deployment Considerations 4. Implementation and Deployment Considerations
4.1. Implementations that do not support Large BFD Packets
4.1. Implementations That Do Not Support Large BFD Packets
While this document proposes no change to the BFD protocol, While this document proposes no change to the BFD protocol,
implementations may not permit arbitrarily padded transport PDUs to implementations may not permit arbitrarily padded transport PDUs to
carry BFD packets. While Section 6 of [RFC5880] warns against carry BFD packets. While Section 6 of [RFC5880] warns against
excessive pedantry, implementations may not work with this mechanism excessive pedantry, implementations may not work with this mechanism
without additional support. without additional support.
[RFC5880], section 6.8.6, discusses the procedures for receiving BFD Section 6.8.6 of [RFC5880] discusses the procedures for receiving BFD
Control packets. The length of the BFD Control packet is validated Control packets. The length of the BFD Control packet is validated
to be less than or equal to the payload of the encapsulating to be less than or equal to the payload of the encapsulating
protocol. When a receiving implementation is incapable of processing protocol. When a receiving implementation is incapable of processing
Large BFD Packets, it could manifest in one of two possible ways: large BFD packets, it could manifest in one of two possible ways:
* A receiving BFD implementation is incapable of accepting Large BFD * A receiving BFD implementation is incapable of accepting large BFD
Packets. This is identical to the packet being discarded. packets. This is identical to the packet being discarded.
* A receiving BFD implementation is capable of accepting Large BFD * A receiving BFD implementation is capable of accepting large BFD
Packets, but the Control packet is improperly rejected during packets, but the Control packet is improperly rejected during
validation procedures. This is identical to the packet being validation procedures. This is identical to the packet being
discarded. discarded.
In each of these cases, the BFD state machine would behave as if it In each of these cases, the BFD state machine would behave as if it
were not receiving Control packets and the receiving implementation were not receiving Control packets, and the receiving implementation
would follow normal BFD procedures regarding not having received would follow normal BFD procedures regarding not having received
control packets. Control packets.
If Large BFD Packets is enabled on a session that is already in the If large BFD packets is enabled on a session that is already in the
Up state and the remote BFD system does not, or cannot support Up state and the remote BFD system does not (or cannot) support
receiving the padded BFD control packets, the session will go Down. receiving the padded BFD control packets, the session will go Down.
4.2. Selecting MTU size to be detected 4.2. Selecting MTU Size To Be Detected
Since the consideration is path MTU, BFD sessions using this feature Since the consideration is Path MTU, BFD sessions using this feature
only need to use an appropriate value of bfd.PaddedPduSize only need to use an appropriate value of bfd.PaddedPduSize to
appropriate to exercise the path MTU for the desired application. exercise the Path MTU for the desired application. This may be
This may be significantly smaller than the system's link MTU; e.g., significantly smaller than the system's link MTU, e.g., desired Path
desired path MTU is 1512 bytes while the interface MTU that BFD with MTU is 1512 bytes, while the interface MTU that BFD with large
large packets is running on is 9000 bytes. packets is running on is 9000 bytes.
In the case multiple BFD clients desire to test the same BFD In the case multiple BFD clients desire to test the same BFD
endpoints using different bfd.PaddedPduSize parameters, endpoints using different bfd.PaddedPduSize parameters,
implementations SHOULD select the largest bfd.PaddedPduSize parameter implementations SHOULD select the largest bfd.PaddedPduSize parameter
from the configured sessions. This is similar to how implementations from the configured sessions. This is similar to how implementations
of BFD select the most aggressive timing parameters for multiple of BFD select the most aggressive timing parameters for multiple
sessions to the same endpoint. Failure to select the largest size sessions to the same endpoint. Failure to select the largest size
will result in BFD sessions going to the Up state and dependent will result in BFD sessions going to the Up state and dependent
applications not having their MTU requirements satisfied. applications not having their MTU requirements satisfied.
4.3. Detecting MTU Mismatches 4.3. Detecting MTU Mismatches
The accepted MTU for an interface is impacted by packet encapsulation The accepted MTU for an interface is impacted by packet encapsulation
considerations at a given layer; e.g., layer 2, layer 3, tunnel, etc. considerations at a given layer, e.g., Layer 2, Layer 3, tunnel, etc.
A common misconfiguration of interface parameters is inconsistent A common misconfiguration of interface parameters is inconsistent
MTU. In the presence of inconsistent MTU, it is possible for MTU. In the presence of inconsistent MTU, it is possible for
applications to have unidirectional connectivity. applications to have unidirectional connectivity.
When it is necessary for an application using BFD with Large Packets When it is necessary for an application using BFD with Large Packets
to test the bi-directional Path MTU, it is necessary to configure the to test the bidirectional Path MTU, it is necessary to configure the
bfd.PaddedPduSize parameter on each side of the BFD session. E.g., bfd.PaddedPduSize parameter on each side of the BFD session. For
if the desire is to verify a 1500 byte MTU in both directions on an example, if the desire is to verify a 1512-byte MTU in both
Ethernet or point to point link, each side of the BFD session must directions on an Ethernet or point-to-point link, each side of the
have bfd.PaddedPduSize set to 1500. In the absence of such BFD session must have bfd.PaddedPduSize set to 1512. In the absence
consistent configuration, BFD with Large Packets may correctly of such consistent configuration, BFD with Large Packets may
determine unidirectional connectivity at the tested MTU, but bi- correctly determine unidirectional connectivity at the tested MTU,
directional MTU may not be properly validated. but bidirectional MTU may not be properly validated.
It should be noted that some interfaces may intentionally have It should be noted that some interfaces may intentionally have
different MTUs. Setting the bfd.PaddedPduSize appropriately for each different MTUs. Setting the bfd.PaddedPduSize appropriately for each
side of the BFD session supports such scenarios. side of the BFD session supports such scenarios.
4.4. Detecting MTU Changes 4.4. Detecting MTU Changes
Once BFD sessions using Large Packets has reached the Up state, Once BFD sessions using Large Packets has reached the Up state,
connectivity at the tested MTU(s) for the session is being validated. connectivity at the tested MTU(s) for the session is being validated.
If the path MTU tested by the BFD with Large Packets session falls If the Path MTU tested by the BFD with Large Packets session falls
below the tested MTU, the BFD session will go Down. below the tested MTU, the BFD session will go Down.
In the opposite circumstance where the path MTU increases, the BFD In the opposite circumstance (where the Path MTU increases), the BFD
session will continue without being impacted. BFD for Large Packets session will continue without being impacted. BFD for Large Packets
only ensures that the minimally acceptable MTU for the session can be only ensures that the minimally acceptable MTU for the session can be
used. used.
4.5. Equal Cost Multiple Paths (ECMP) or other Load Balancing 4.5. Equal-Cost Multipath (ECMP) or Other Load-Balancing Considerations
Considerations
Various mechanisms are utilized to increase throughput between two Various mechanisms are utilized to increase throughput between two
endpoints at various network layers. Such features include Link endpoints at various network layers. Such features include Link
Aggregate Groups (LAGs) or ECMP forwarding. Such mechanisms balance Aggregation Groups (LAGs) or ECMP forwarding. Such mechanisms
traffic across multiple physical links while hiding the details of balance traffic across multiple physical links while hiding the
that balancing from the higher networking layers. The details of details of that balancing from the higher networking layers. The
that balancing are highly implementation specific. details of that balancing are highly implementation specific.
In the presence of such load balancing mechanisms, it is possible to In the presence of such load-balancing mechanisms, it is possible to
have member links that are not properly forwarding traffic. In such have member links that are not properly forwarding traffic. In such
circumstances, this will result in dropped traffic when traffic is circumstances, this will result in dropped traffic when traffic is
chosen to be load balanced across those member links. chosen to be load balanced across those member links.
Such load balancing mechanisms may not permit all link members to be Such load-balancing mechanisms may not permit all link members to be
properly tested by BFD. This is because the BFD Control packets may properly tested by BFD. This is because the BFD Control packets may
be forwarded only along links that are up. BFD on LAG, [RFC7130], be forwarded only along links that are up. BFD on LAG interfaces,
was developed to help cover one such scenario. However, for testing [RFC7130], was developed to help cover one such scenario. However,
forwarding over multiple hops, there is no such specified general for testing forwarding over multiple hops, there is no such specified
purpose BFD mechanism for exercising all links in an ECMP. This may general-purpose BFD mechanism for exercising all links in an ECMP.
result in a BFD session being in the Up state while some traffic may This may result in a BFD session being in the Up state while some
be dropped or otherwise negatively impacted along some component traffic may be dropped or otherwise negatively impacted along some
links. component links.
Some BFD implementations utilize their internal understanding of the Some BFD implementations utilize their internal understanding of the
component links and their resultant forwarding to exercise BFD in 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 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 state to the health of that ECMP. Due to implementation-specific
load balancing, it is not possible to standardize such additional load balancing, it is not possible to standardize such additional
mechanisms for BFD. mechanisms for BFD.
Misconfiguration of some member MTUs may lead to Load Balancing that Misconfiguration of some member MTUs may lead to load balancing that
may have an inconsistent Path MTU depending on how the traffic is may have an inconsistent Path MTU depending on how the traffic is
balanced. While the intent of BFD with Large Packets is to verify balanced. While the intent of BFD with large packets is to verify
path MTU, it is subject to the same considerations above. Path MTU, it is subject to the same considerations above.
The above text also applies to most, if not all, BFD techniques. This section applies to most, if not all, BFD techniques.
4.6. S-BFD 4.6. S-BFD
This mechanism also can be applied to other forms of BFD, including This mechanism also can be applied to other forms of BFD, including
S-BFD [RFC7880]. Seamless BFD (S-BFD) [RFC7880].
5. BFD Encapsulated in Large Packets YANG Module 5. BFD Encapsulated in Large Packets YANG Module
5.1. Data Model Overview 5.1. Data Model Overview
This YANG module augments the "ietf-bfd" module to add a flag This YANG module augments the "ietf-bfd" module to add a flag
'padding' to enable this feature. The feature statement 'padding' 'padding' to enable this feature. The feature statement 'padding'
needs to be enabled to indicate that BFD Encapsulated in Large Packet needs to be enabled to indicate that BFD encapsulated in large
is supported by the implementation. packets is supported by the implementation.
Further, this YANG module augments the YANG modules for single-hop, Further, this YANG module augments the YANG modules for single-hop,
multi-hop, LAG, and MPLS to add the "pdu-size" parameter to those multihop, LAG, and MPLS to add the "pdu-size" parameter to those
session types to configure Large BFD packets. session types to configure large BFD packets.
Finally, similar to the grouping "client-cfg-parms" defined in Finally, similar to the grouping "client-cfg-parms" defined in
Section 2.1 of [RFC9314], this YANG module defines a grouping "bfd- Section 2.1 of [RFC9314], this YANG module defines a grouping "bfd-
large-common" that may be utilized by BFD clients using "client-cfg- large-common" that may be utilized by BFD clients using "client-cfg-
params" to uniformly add support for the feature defined in this RFC. params" to uniformly add support for the feature defined in this RFC.
module: ietf-bfd-large module: ietf-bfd-large
augment /rt:routing/rt:control-plane-protocols augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
skipping to change at page 7, line 28 skipping to change at line 303
+--rw pdu-size? padded-pdu-size {padding}? +--rw pdu-size? padded-pdu-size {padding}?
augment /rt:routing/rt:control-plane-protocols augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls /rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls
/bfd-mpls:session-groups/bfd-mpls:session-group: /bfd-mpls:session-groups/bfd-mpls:session-group:
+--rw pdu-size? padded-pdu-size {padding}? +--rw pdu-size? padded-pdu-size {padding}?
Figure 1 Figure 1
5.2. YANG Module 5.2. YANG Module
This YANG module imports A YANG Data Model for Routing [RFC8349], and This YANG module imports "A YANG Data Model for Routing Management
YANG Data Model for Bidirectional Forwading Detection (BFD) (NMDA Version)" [RFC8349] and "YANG Data Model for Bidirectional
[RFC9314]. Forwarding Detection (BFD)" [RFC9314].
<CODE BEGINS> file "ietf-bfd-large@2025-01-15.yang" <CODE BEGINS> file "ietf-bfd-large@2025-03-31.yang"
module ietf-bfd-large { module ietf-bfd-large {
yang-version 1.1; yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-large"; namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-large";
prefix "bfdl"; prefix bfdl;
import ietf-routing { import ietf-routing {
prefix rt; prefix rt;
reference reference
"RFC 8349: A YANG Data Model for Routing Management "RFC 8349: A YANG Data Model for Routing Management
(NMDA version)"; (NMDA version)";
} }
import ietf-bfd { import ietf-bfd {
prefix bfd; prefix bfd;
skipping to change at page 8, line 48 skipping to change at line 371
Authors: Jeffrey Haas (jhaas@juniper.net) Authors: Jeffrey Haas (jhaas@juniper.net)
Albert Fu (afu14@bloomberg.net)."; Albert Fu (afu14@bloomberg.net).";
description description
"This YANG module augments the base BFD YANG module to add "This YANG module augments the base BFD YANG module to add
attributes related to support for BFD Encapsulated in Large attributes related to support for BFD Encapsulated in Large
Packets. In particular, it adds a per-session parameter for the Packets. In particular, it adds a per-session parameter for the
BFD Padded PDU Size. BFD Padded PDU Size.
Copyright (c) 2024 IETF Trust and the persons identified as Copyright (c) 2025 IETF Trust and the persons identified as
authors of the code. All rights reserved. authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to without modification, is permitted pursuant to, and subject to
the license terms contained in, the Revised BSD License set the license terms contained in, the Revised BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents Relating to IETF Documents
(https://trustee.ietf.org/license-info). (https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX This version of this YANG module is part of RFC 9764
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself (https://www.rfc-editor.org/info/rfc9764); see the RFC itself
for full legal notices. for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as 'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here."; they appear in all capitals, as shown here.";
revision "2025-01-15" { revision 2025-03-31 {
description description
"Initial Version."; "Initial Version.";
reference reference
"RFC XXXX, BFD Encapsulated in Large Packets."; "RFC 9764, Bidirectional Forwarding Detection (BFD)
Encapsulated in Large Packets.";
} }
feature padding { feature padding {
description description
"If supported, the feature allows for BFD sessions to be "If supported, the feature allows for BFD sessions to be
configured with padded PDUs in support of BFD Encapsulated in configured with padded PDUs in support of BFD Encapsulated in
Large Packets."; Large Packets.";
} }
typedef padded-pdu-size { typedef padded-pdu-size {
type uint16 { type uint16 {
range "24..65535"; range "24..65535";
} }
units "bytes"; units "bytes";
description description
"The size of the padded and encapsulated BFD control packets "The size of the padded and encapsulated BFD control packets
to be transmitted at layer 3. The BFD minimum control packet to be transmitted at Layer 3. The BFD minimum control packet
size is 24 or 26 octets; see Section 6.8.6 of RFC 5880. 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 If the configured padded PDU size is smaller than the minimum
sized packet of a given BFD session, then the minimum sized sized packet of a given BFD session, then the minimum sized
packet for the session will be used. packet for the session will be used.
The maximum padded PDU size may be limited by the supported The maximum padded PDU size may be limited by the supported
interface MTU of the system."; interface MTU of the system.";
reference reference
"RFC XXXX, BFD Encapsulated in Large Packets."; "RFC 9764, Bidirectional Forwarding Detection (BFD)
Encapsulated in Large Packets.";
} }
grouping bfd-large-common { grouping bfd-large-common {
description description
"Common configuration and operational state for BFD "Common configuration and operational state for BFD
Encapsulated in Large Packets."; Encapsulated in Large Packets.";
reference reference
"RFC XXXX, BFD Encapsulated in Large Packets."; "RFC 9764, Bidirectional Forwarding Detection (BFD)
Encapsulated in Large Packets.";
leaf pdu-size { leaf pdu-size {
if-feature "padding"; if-feature "padding";
type padded-pdu-size; type padded-pdu-size;
description description
"If set, this configures the padded PDU size for the "If set, this configures the padded PDU size for the
Asynchronous mode BFD session. By default, no additional Asynchronous mode BFD session. By default, no additional
padding is added to such packets."; padding is added to such packets.";
} }
} }
augment "/rt:routing/rt:control-plane-protocols/" + augment "/rt:routing/rt:control-plane-protocols/"
"rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/" + + "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
"bfd-ip-sh:sessions/bfd-ip-sh:session" { + "bfd-ip-sh:sessions/bfd-ip-sh:session" {
uses bfd-large-common; uses bfd-large-common;
description description
"Augment the 'bfd' container to add attributes related to BFD "Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets."; Encapsulated in Large Packets.";
} }
augment "/rt:routing/rt:control-plane-protocols/" + augment "/rt:routing/rt:control-plane-protocols/"
"rt:control-plane-protocol/bfd:bfd/bfd-ip-mh:ip-mh/" + + "rt:control-plane-protocol/bfd:bfd/bfd-ip-mh:ip-mh/"
"bfd-ip-mh:session-groups/bfd-ip-mh:session-group" { + "bfd-ip-mh:session-groups/bfd-ip-mh:session-group" {
uses bfd-large-common; uses bfd-large-common;
description description
"Augment the 'bfd' container to add attributes related to BFD "Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets."; Encapsulated in Large Packets.";
} }
augment "/rt:routing/rt:control-plane-protocols/" + augment "/rt:routing/rt:control-plane-protocols/"
"rt:control-plane-protocol/bfd:bfd/bfd-lag:lag/" + + "rt:control-plane-protocol/bfd:bfd/bfd-lag:lag/"
"bfd-lag:sessions/bfd-lag:session" { + "bfd-lag:sessions/bfd-lag:session" {
uses bfd-large-common; uses bfd-large-common;
description description
"Augment the 'bfd' container to add attributes related to BFD "Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets."; Encapsulated in Large Packets.";
} }
augment "/rt:routing/rt:control-plane-protocols/" + augment "/rt:routing/rt:control-plane-protocols/"
"rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls/" + + "rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls/"
+ "bfd-mpls:session-groups/bfd-mpls:session-group" {
"bfd-mpls:session-groups/bfd-mpls:session-group" {
uses bfd-large-common; uses bfd-large-common;
description description
"Augment the 'bfd' container to add attributes related to BFD "Augment the 'bfd' container to add attributes related to BFD
Encapsulated in Large Packets."; Encapsulated in Large Packets.";
} }
} }
<CODE ENDS> <CODE ENDS>
Figure 2 Figure 2
skipping to change at page 11, line 31 skipping to change at line 499
On-path attackers that can selectively drop BFD packets, including On-path attackers that can selectively drop BFD packets, including
those with large MTUs, can cause BFD sessions to go Down. those with large MTUs, can cause BFD sessions to go Down.
The contents of the padding payload are set to zero. This avoids The contents of the padding payload are set to zero. This avoids
implementation issues where the local uninitialized data may be implementation issues where the local uninitialized data may be
leaked. leaked.
6.1. YANG Security Considerations 6.1. YANG Security Considerations
This section is modeled after the template described in Section 3.7 This section is modeled after the template described in Section 3.7
of [I-D.ietf-netmod-rfc8407bis]. of [YANG-GUIDELINES].
The "ietf-bfd-large" YANG module defines a data model that is The "ietf-bfd-large" YANG module defines a data model that is
designed to be accessed via YANG-based management protocols, such as designed to be accessed via YANG-based management protocols, such as
NETCONF [RFC6241] and RESTCONF [RFC8040]. These protocols have to NETCONF [RFC6241] and RESTCONF [RFC8040]. These protocols have to
use a secure transport layer (e.g., SSH [RFC4252], TLS [RFC8446], and use a secure transport layer (e.g., SSH [RFC4252], TLS [RFC8446], and
QUIC [RFC9000]) and have to use mutual authentication. QUIC [RFC9000]) and have to use mutual authentication.
The Network Configuration Access Control Model (NACM) [RFC8341] The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or
skipping to change at page 12, line 18 skipping to change at line 534
perhaps intentionally, if the session cannot accommodate such BFD perhaps intentionally, if the session cannot accommodate such BFD
control packets. Operators should be mindful that multiple BFD control packets. Operators should be mindful that multiple BFD
clients may rely on the status of a given BFD session when clients may rely on the status of a given BFD session when
changing this value. changing this value.
There are no particularly sensitive readable data nodes. There are no particularly sensitive readable data nodes.
There are no particularly sensitive RPC or action operations. There are no particularly sensitive RPC or action operations.
Modules that use the groupings that are defined in this document Modules that use the groupings that are defined in this document
should identify the corresponding security considerations. This should identify the corresponding security considerations. For
module defines one such grouping, "bfd-large-common", which contains example, reusing some of these groupings will expose privacy-related
the "pdu-size" data node whose security considerations are documented information (e.g., 'node-example'). This module defines one such
above. grouping, "bfd-large-common", which contains the "pdu-size" data node
whose security considerations are documented above.
7. IANA Considerations 7. IANA Considerations
7.1. The "IETF XML" Registry 7.1. The "IETF XML" Registry
This document registers one URIs in the "ns" subregistry of the "IETF IANA has registered the following URI in the "ns" subregistry of the
XML" registry [RFC3688]. Following the format in [RFC3688], the "IETF XML Registry" [RFC3688].
following registration is requested:
URI: urn:ietf:params:xml:ns:yang:ietf-bfd-large
Registrant Contact: The IESG
XML: N/A, the requested URI is an XML namespace.
Figure 3 URI: urn:ietf:params:xml:ns:yang:ietf-bfd-large
Registrant Contact: The IESG
XML: N/A; the requested URI is an XML namespace.
7.2. The "YANG Module Names" Registry 7.2. The "YANG Module Names" Registry
This document registers one YANG modules in the "YANG Module Names" IANA has registered the following YANG module in the "YANG Module
registry [RFC6020]. Following the format in [RFC6020], the following Names" registry [RFC6020].
registrations are requested:
name: ietf-bfd-large
namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-large
prefix: bfdl
reference: RFC XXXX
Figure 4
8. Acknowledgments Name: ietf-bfd-large
Maintained by IANA: N
Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-large
Prefix: bfdl
Reference: RFC 9764
The authors would like to thank Les Ginsberg, Mahesh Jethanandani, 8. References
Robert Raszuk, and Ketan Talaulikar, for their valuable feedback on
this proposal.
9. Normative References 8.1. Normative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981, DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>. <https://www.rfc-editor.org/info/rfc791>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 14, line 30 skipping to change at line 628
Routing Management (NMDA Version)", RFC 8349, Routing Management (NMDA Version)", RFC 8349,
DOI 10.17487/RFC8349, March 2018, DOI 10.17487/RFC8349, March 2018,
<https://www.rfc-editor.org/info/rfc8349>. <https://www.rfc-editor.org/info/rfc8349>.
[RFC9314] Jethanandani, M., Ed., Rahman, R., Ed., Zheng, L., Ed., [RFC9314] Jethanandani, M., Ed., Rahman, R., Ed., Zheng, L., Ed.,
Pallagatti, S., and G. Mirsky, "YANG Data Model for Pallagatti, S., and G. Mirsky, "YANG Data Model for
Bidirectional Forwarding Detection (BFD)", RFC 9314, Bidirectional Forwarding Detection (BFD)", RFC 9314,
DOI 10.17487/RFC9314, September 2022, DOI 10.17487/RFC9314, September 2022,
<https://www.rfc-editor.org/info/rfc9314>. <https://www.rfc-editor.org/info/rfc9314>.
10. Informative References 8.2. Informative References
[I-D.haas-xiao-bfd-echo-path-mtu]
Min, X. and J. Haas, "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] [BFD-ECHO-PATH-MTU]
Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for Min, X., Ed. and J. Haas, Ed., "Application of the BFD
Authors and Reviewers of Documents Containing YANG Data Echo function for Path MTU Verification or Detection",
Models", Work in Progress, Internet-Draft, draft-ietf- Work in Progress, Internet-Draft, draft-haas-xiao-bfd-
netmod-rfc8407bis-22, 14 January 2025, echo-path-mtu-01, 11 July 2011,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod- <https://datatracker.ietf.org/doc/html/draft-haas-xiao-
rfc8407bis-22>. bfd-echo-path-mtu-01>.
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, [RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
DOI 10.17487/RFC1191, November 1990, DOI 10.17487/RFC1191, November 1990,
<https://www.rfc-editor.org/info/rfc1191>. <https://www.rfc-editor.org/info/rfc1191>.
[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH) [RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252, Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, <https://www.rfc-editor.org/info/rfc4252>. January 2006, <https://www.rfc-editor.org/info/rfc4252>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
skipping to change at page 15, line 27 skipping to change at line 664
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based [RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000, Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021, DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>. <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 Authors' Addresses
Jeffrey Haas Jeffrey Haas
Juniper Networks, Inc. Juniper Networks, Inc.
1133 Innovation Way 1133 Innovation Way
Sunnyvale, CA 94089 Sunnyvale, CA 94089
United States of America United States of America
Email: jhaas@juniper.net Email: jhaas@juniper.net
Albert Fu Albert Fu
 End of changes. 63 change blocks. 
194 lines changed or deleted 192 lines changed or added

This html diff was produced by rfcdiff 1.48.