Network Working Group M. Jethanandani
Internet-Draft Arrcus
Intended status: Experimental A. Mishra
Expires: 18 October 2025 Aalyria Technologies
A. Saxena
Ciena Corporation
M. Bhatia
Google
J. Haas
Juniper Networks
16 April 2025
Optimizing BFD Authentication
draft-ietf-bfd-optimizing-authentication-24
Abstract
This document describes an optimization to BFD Authentication as
described in Section 6.7 of BFD RFC 5880. It provides procedure
where only important BFD state transitions require strong
authentication and permits the majority of BFD Control Packets to use
a less computationally intensive authentication mechanism. This
enables BFD to scale better when there is a desire to use strong
authentication.
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 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
and may be updated, replaced, or obsoleted by other documents 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 18 October 2025.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (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
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
1.2. Note to RFC Editor . . . . . . . . . . . . . . . . . . . 5
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Authentication Mode . . . . . . . . . . . . . . . . . . . . . 6
3. Signaling Optimized Authentication . . . . . . . . . . . . . 7
3.1. Receipt Using Optimized Authentication . . . . . . . . . 8
4. Optimized Authentication Operations . . . . . . . . . . . . . 9
5. Optimizing Authentication YANG Model . . . . . . . . . . . . 9
5.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 10
5.2. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 10
5.3. The YANG Model . . . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1. Auth Type . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2. IETF XML Registry . . . . . . . . . . . . . . . . . . . . 15
6.3. The YANG Module Names Registry . . . . . . . . . . . . . 15
6.4. Updated IANA Module . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Updated BFD IANA Module . . . . . . . . . . . . . . 20
Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 24
B.1. Single Hop BFD Configuration . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
Authenticating every BFD [RFC5880] control packet with MD5
Message-Digest Algorithm [RFC1321], or Secure Hash Algorithm (SHA-1)
is a computationally intensive process. This makes it difficult, if
not impossible, to authenticate every packet - particularly at faster
rates. Also, the recent escalating series of attacks on MD5 and
SHA-1 described in Finding Collisions in the Full SHA-1
[SHA-1-attack1] and New Collision Search for SHA-1 [SHA-1-attack2]
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raise concerns about their remaining useful lifetime as outlined in
Updated Security Considerations for the MD5 Message-Digest and the
HMAC-MD5 Algorithm [RFC6151] and Security Considerations for the
SHA-0 and SHA-1 Message-Digest Algorithm [RFC6194]. If replaced by
stronger algorithms the computational overhead will make the task of
authenticating every packet even more difficult to achieve.
This document describes an experimental update to BFD [RFC5880].
This experiment is intended to provide additional insights into what
happens when the optimized authentication method defined in this
document is used. Here are the reasons why this document is on the
Experimental track:
* In the initial stages of the document, there were significant
participation and reviews from the working group. Since then,
there has been considerable changes to the document, e.g. the use
of ISAAC, allowing for ISAAC bootstrapping when a BFD session
comes up and use of a single Auth Type to indicate use of
optimized authentication etc. These changes did not get
significant review from the working group and therefore does not
meet the bar set in Section 4.1.1 of [RFC2026]
* There are no known implementations (even proof-of-concept) or
implementation plans. As a result, we do not currently know if
there will be interop issues with legacy implementations or what
exactly are the performance benefits of the optimization method.
* The work in this document could become very valuable in the
future, especially if the need for deploying BFD authentication at
scale becomes a reality.
This document is classified as Experimental and is not part of the
IETF Standards Track. Implementations based on this document should
not be considered as compliant with BFD [RFC5880].
This document proposes that BFD control packets that signal a state
change, a change in demand mode (D bit), or a poll sequence (P or F
bit change) be categorized as a "significant change". Control
packets that do not require a poll sequence, such as a change in
bfd.RequiredMinRxInterval or bfd.RequiredMinTxInterval, are also
considered as a significant change.
Such significant changes are intended to be protected by a "strong"
authentication mechanism, such as those already defined for use with
BFD. For example, MD5 and SHA1. (Section 6.7 of [RFC5880])
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The majority of packets exchanged on a BFD session in the Up state
are not significant changes. This document proposes a new optimized
authentication mode where packets that are not significant changes
may use a less computationally intensive authentication mechanism.
The intention of these optimized procedures is to permit strong
authentication for BFD state changes and utilize the less
computationally intensive authentication mechanisms to provide
protection for the session in the Up state while performing less
overall work. Such procedures will aid BFD session scaling without
compromising BFD session security.
Once the session has reached the Up state, the session can choose a
less computationally intensive Auth Type. Currently, this includes:
* Meticulous Keyed ISAAC authentication as described in
[I-D.ietf-bfd-secure-sequence-numbers]. This authentication type
protects the BFD session when BFD Up packets do not change,
because only the paired devices know the shared secret, key, and
sequence number to select the ISAAC result.
When using the less computationally intensive authentication
mechanism, BFD should periodically test the session using the strong
authentication mechanism. Strong authentication is tested using a
Poll sequence. To test strong authentication, a Poll sequence SHOULD
be initiated by the sender using the strong authentication mode
rather than the less computationally intensive mechanism. If a
control packet with the Final (F) bit is not received within the
Detect Interval, the session has been compromised, and MUST be
brought down.
This "strong reauthentication interval" for performing such periodic
tests using the strong authentication mechanism can be configured
depending on the capability of the system.
Most packets transmitted on a BFD session are BFD Up packets.
Strongly authenticating a small subset of these packets with a Poll
sequence as described above, for example every one minute,
significantly reduces the computational demand for the system while
maintaining security of the session across the configured strong
reauthentication interval.
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1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD 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.
1.2. Note to RFC Editor
This document uses several placeholder values throughout the
document. Please replace them as follows and remove this note before
publication.
RFC XXXX, where XXXX is the number assigned to this document at the
time of publication.
2025-04-16 with the actual date of the publication of this document.
1.3. Terminology
The following terms used in this document have been defined in BFD
[RFC5880].
* Auth Type
* Detect Multiplier
* Detection Time
The following terms are introduced in this document.
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+==================+==============================================+
| Term | Meaning |
+==================+==============================================+
| significant | State change, a demand mode change (to D |
| change | bit) or a poll sequence change (P or F bit). |
| | Changes to BFD control packets that do not |
| | require a poll sequence, such as |
| | bfd.RequiredMinRxInterval, |
| | bfd.RequiredMinTxInterval, or bfd.DetectMult |
| | are also considered as a significant change. |
+------------------+----------------------------------------------+
| configured | Interval at which BFD control packets are |
| strong | retried with strong authentication. |
| reauthentication | |
| interval | |
+------------------+----------------------------------------------+
Table 1
2. Authentication Mode
The cryptographic authentication mechanisms specified in Section 6.7
of BFD [RFC5880] describes enabling and disabling of authentication
as a one time operation. As a security precaution, it mentions that
authentication state be allowed to change at most once. Once
enabled, every packet must have Authentication Bit set and the
associated Authentication Type appended. In addition, it states that
an implementation SHOULD NOT allow the authentication state to be
changed based on the receipt of a BFD control packet.
This document proposes that an "optimized" authentication mode that
permits both a strong authentication mode and a less computationally
intensive mode to be used within the same BFD session. This pairing
of a strong and an less computationally intensive mode of
authentication is carried in new BFD authentication types
representing a given optimized authentication type pairing.
This document defines which BFD control packets are required to be
strongly authenticated. A BFD control packet that fails
authentication is discarded, or a BFD control packet that was
supposed to be strongly authenticated, but was not; e.g. a
significant change packet, is discarded. However, there is no change
to the state machine for BFD, as the decision of a significant change
is still decided by how many valid consecutive packets were received.
In this specification, the contents of an Up packet MUST NOT change
aside from the Authentication Section without strong authentication.
The full procedure is documented in the following sections.
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3. Signaling Optimized Authentication
When the Authentication Present (A) bit is set and the Auth Type is a
type supporting Optimized BFD Authentication (Section 6.1), the Auth
Type signals a pairing of a strong authentication type and a less
computationally intensive authentication type. This pairing is
advertised in a single Auth Type value in order to permit
implementations to be aware that:
* Optimized BFD procedures will be in use.
* The pairing of the strong and less computationally intensive
authentication mechanisms will be used for that session.
* The requirement to carry a Sequence Number.
* The current strong or less computationally intensive mode will be
carried as described below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Auth Type | Auth Len | Auth Key ID | Opt. Mode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication Specific Data ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Common BFD Authentication Section
The Meticulous Keyed MD5, Meticulous Keyed SHA-1, and Meticulous
Keyed ISAAC Authentication Sections define the fourth octet as
"Reserved". This document repurposes the "Reserved" field as the
"Optimized Authentication Mode" field when used for authentication
types for optimized BFD procedures.
The values of the Optimized Authentication Mode field are:
1. When using the strong authentication type for optimized BFD Auth
Types.
2. When using the less computationally intensive authentication type
for optimized BFD Auth Types.
Authentication Specific Data: When using the strong authentication
type, the remainder of the Authentication Section carries that type's
data.
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For example, for Auth Type "Optimized MD5 Meticulous Keyed ISAAC
Authentication" (type TBD):
When Optimized Authentication Mode is 1, the format of the
authentication section is the same as Section 4.3 of [RFC5880],
excepting that Auth Type is still TBD and that Reserved is set to 1.
When Optimized Authentication Mode is 2, the format of the
authentication section is the same as Section 5 of
[I-D.ietf-bfd-secure-sequence-numbers], excepting that Auth Type is
still TBD and that Reserved is set to 2.
3.1. Receipt Using Optimized Authentication
The procedures for authenticating BFD Control packets using Optimized
Authentication is similar to the existing procedures covered in
Section 6.7 of [RFC5880]. Optimized Authentication modes have common
procedural requirements for authentication regardless of which strong
and less computationally intensive authentication modes are used.
The required value of the Auth Len field for a given Optimized
Authentication mode is defined in the respective specifications for
the strong mode and less computationally intensive mode.
The following common procedures apply to authenticating BFD Control
packets utilizing Optimized Authentication:
If the received BFD Control packet does not contain an Authentication
Section ([RFC5880], Section 4.1), or the Auth Type is not a supported
Optimized Authentication Auth Type, then the received packet MUST be
discarded.
If the received BFD Control packet contains an optimized
authentication type using these procedures and the Optimized
Authentication Mode field is not 1 or 2, then the received packet
MUST be discarded.
If the Auth Len field is not equal to a value appropriate for the
Optimized Authentication Mode field, the packet MUST be discarded.
If bfd.AuthSeqKnown is 1, examine the Sequence Number field. If the
sequence number lies outside of the range of bfd.RcvAuthSeq+1 to
bfd.RcvAuthSeq+(3*Detect Mult) inclusive (when treated as an unsigned
32-bit circular number space) the received packet MUST be discarded.
Otherwise (bfd.AuthSeqKnown is 0), bfd.AuthSeqKnown MUST be set to 1,
bfd.RcvAuthSeq MUST be set to the value of the received Sequence
Number field, and the received packet MUST be accepted.
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For the specified Auth Type and Optimized Authentication Mode,
perform the appropriate authentication procedures. If authentication
succeeds, the received packet MUST be accepted. Otherwise, the
received packet MUST be discarded.
4. Optimized Authentication Operations
As noted in Section 2, when using optimized BFD procedures, strong
authentication is used in the BFD state machine to bring a BFD
session to the Up state or to make any change of the BFD parameters
as carried in the BFD Control packet when in the Up state.
Once the BFD session has reached the Up state, the BFD Up state MUST
be signaled to the remote BFD system using the strong authentication
mode for an interval that is at least the Detection Time before
switching to the less computationally intensive authentication mode.
This is to permit mechanisms such as Meticulous Keyed ISAAC for BFD
Authentication [I-D.ietf-bfd-secure-sequence-numbers] to be
bootstrapped before switching to the less computationally intensive
mode.
It is RECOMMENDED that when using optimized authentication that
implementations switch from strong authentication to the less
computationally intensive authentication mode after an interval that
is at least the Detection Time. In the circumstances where a BFD
session successfully reaches the Up state with strong authentication,
but there are problems with the optimized authentication, this will
permit the remote system to tear down the session as quickly as
possible.
BFD sessions using optimized authentication that succeed in reaching
the Up state using strong authentication and fail using the optimized
authentication SHOULD bring the issue to the attention of the
operator. Further, implementations MAY wish to throttle session
restarts.
It is further RECOMMENDED that BFD implementations using optimized
authentication defer notifying their client that the session has
reached the Up state until it has transitioned to using the optimized
authentication mode. In the event where optimized authentication is
failing in the protocol, this avoids propagating the failed
transitions to the optimized mode to their clients.
5. Optimizing Authentication YANG Model
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5.1. Data Model Overview
The YANG 1.1 [RFC7950] model defined in this document augments the
"ietf-bfd" module to add configuration relevant to the management of
the feature defined in this document. In particular, it adds crypto
algorithms that are described in this model, and in Meticulous Keyed
ISAAC for BFD Authentication [I-D.ietf-bfd-secure-sequence-numbers].
It adds a feature statement to enable optimized authentication.
Finally, it adds an interval value that specifies how often the BFD
session should be re-authenticated once it is in the Up state.
5.2. Tree Diagram
The tree diagram for the YANG modules defined in this document use
annotations defined in YANG Tree Diagrams. [RFC8340].
module: ietf-bfd-opt-auth
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
/bfd-ip-sh:authentication:
+--rw reauth-interval? uint32
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
/bfd-ip-mh:authentication:
+--rw reauth-interval? uint32
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-lag:lag
/bfd-lag:sessions/bfd-lag:session/bfd-lag:authentication:
+--rw reauth-interval? uint32
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls
/bfd-mpls:session-groups/bfd-mpls:session-group
/bfd-mpls:authentication:
+--rw reauth-interval? uint32
5.3. The YANG Model
This YANG module imports YANG Key Chain [RFC8177], A YANG Data Model
for Routing Management (NMDA version) [RFC8349], and YANG Data Model
for Bidirectional Forwarding Detection (BFD) [RFC9314].
Implementations supporting the optimization procedures defined in
this document enable optimization by using one of the newly defined
key-chain crypto-algorithms defined in this YANG module.
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<CODE BEGINS> file "ietf-bfd-opt-auth@2025-04-16.yang"
module ietf-bfd-opt-auth {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-opt-auth";
prefix "bfdoa";
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 (BFD).";
}
import ietf-bfd-ip-sh {
prefix bfd-ip-sh;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection (BFD).";
}
import ietf-bfd-ip-mh {
prefix bfd-ip-mh;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection (BFD).";
}
import ietf-bfd-lag {
prefix bfd-lag;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection (BFD).";
}
import ietf-bfd-mpls {
prefix bfd-mpls;
reference
"RFC 9314: YANG Data Model for Bidirectional
Forwarding Detection (BFD).";
}
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import ietf-key-chain {
prefix key-chain;
reference
"RFC 8177: YANG Data Model for Key Chains.";
}
organization
"IETF BFD Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/bfd>
WG List: <rtg-bfd@ietf.org>
Authors: Mahesh Jethanandani (mjethanandani@gmail.com)
Ashesh Mishra (mishra.ashesh@gmail.com)
Ankur Saxena (ankurpsaxena@gmail.com)
Manav Bhatia (mnvbhatia@google.com).";
description
"This YANG module augments the base BFD YANG model to add
attributes related to BFD Optimized Authentication.
Copyright (c) 2025 IETF Trust and the persons identified as
authors of the code. All rights reserved.
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); 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 "2025-04-16" {
description
"Initial Version.";
reference
"RFC XXXX: Optimizing BFD Authentication.";
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}
feature optimized-auth {
description
"When enabled, this implementation supports optimized
authentication as described in this document.";
}
identity optimized-md5-meticulous-keyed-isaac {
base key-chain:crypto-algorithm;
description
"BFD Optimized Authentication using Meticulous Keyed MD5 as the
strong authentication and Meticulous Keyed ISAAC Keyed as the
less computationally intensive authentication.";
reference
"RFC XXXX: Meticulous Keyed ISAAC for BFD Authentication.";
}
identity optimized-sha1-meticulous-keyed-isaac {
base key-chain:crypto-algorithm;
description
"BFD Optimized Authentication using Meticulous Keyed SHA-1 as
the strong authentication and Meticulous Keyed ISAAC Keyed as
the less computationally intensive authentication.";
reference
"RFC XXXX: Meticulous Keyed ISAAC for BFD Authentication.";
}
grouping bfd-opt-auth-config {
description
"Grouping for BFD Optimized Authentication Parameters.";
leaf reauth-interval {
type uint32;
units "seconds";
default "60";
description
"Interval of time after which strong authentication
should be utilized to prevent an on-path-attacker attack.
Default is 1 minute.
A value of zero means that we do not do periodic
reauthentication using the strong authentication method.
This value SHOULD have jitter applied to it to avoid
self-synchronization during expensive authentication
operations.";
}
}
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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" +
"/bfd-ip-sh:authentication" {
uses bfd-opt-auth-config;
description
"Augment the 'authentication' container for single hop BFD
module to add attributes related to BFD optimized
authentication.";
}
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/" +
"bfd-ip-mh:authentication" {
uses bfd-opt-auth-config;
description
"Augment the 'authentication' container for multi-hop BFD
module to add attributes related to BFD optimized
authentication.";
}
augment "/rt:routing/rt:control-plane-protocols/" +
"rt:control-plane-protocol/bfd:bfd/bfd-lag:lag/" +
"bfd-lag:sessions/bfd-lag:session/" +
"bfd-lag:authentication" {
uses bfd-opt-auth-config;
description
"Augment the 'authentication' container for BFD over LAG
module to add attributes related to BFD optimized
authentication.";
}
augment "/rt:routing/rt:control-plane-protocols/" +
"rt:control-plane-protocol/bfd:bfd/bfd-mpls:mpls/" +
"bfd-mpls:session-groups/bfd-mpls:session-group/" +
"bfd-mpls:authentication" {
uses bfd-opt-auth-config;
description
"Augment the 'authentication' container for BFD over MPLS
module to add attributes related to BFD optimized
authentication.";
}
}
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<CODE ENDS>
6. IANA Considerations
This documents requests the assignment of two new authentication
types, one URI, one YANG model, and an update to an existing IANA
YANG model.
6.1. Auth Type
This document requests an update to the registry titled "BFD
Authentication Types". IANA is requested to assign two new BFD
AuthType:
* Optimized MD5 Meticulous Keyed ISAAC Authentication
[I-D.ietf-bfd-secure-sequence-numbers] (Part
meticulous-keyed-isaac-authentication), with a suggested value of
7.
* Optimized SHA-1 Meticulous Keyed ISAAC Authentication
[I-D.ietf-bfd-secure-sequence-numbers] (Part
meticulous-keyed-isaac-authentication), with a suggested value of
8.
6.2. IETF XML Registry
This document registers one URIs in the "ns" subregistry of the "IETF
XML" registry [RFC3688]. Following the format in [RFC3688], the
following registration is requested:
URI: urn:ietf:params:xml:ns:yang:ietf-bfd-opt-auth
Registrant Contact: The IESG
XML: N/A, the requested URI is an XML namespace.
6.3. The YANG Module Names Registry
This document registers one YANG modules in the "YANG Module Names"
registry [RFC6020]. Following the format in [RFC6020], the following
registrations are requested:
name: ietf-bfd-opt-auth
namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-opt-auth
prefix: bfdoa
reference: RFC XXXX
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6.4. Updated IANA Module
This document also requests an update to an existing IANA YANG module
described in Updated BFD IANA Module (Appendix A).
7. Security Considerations
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC8446]. The NETCONF 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 are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., config true, which is the
default). These data nodes may be considered sensitive or vulnerable
in some network environments. Write operations (e.g., edit-config)
to these data nodes without proper protection can have a negative
effect on network operations. Some of the subtrees and data nodes
and their sensitivity/vulnerability are described here.
* 'reauth-interval' specifies the interval in Up state, after which
a strong authentication SHOULD be performed to prevent a Person-
In-The-Middle (PITM) attack. If this interval is set very low,
the utility of these optimization procedures is lessened. If this
interval is set very high, attacks detected by the strong
authentication mechanisms may happen overly late.
Some of the readable data nodes in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control read access (e.g., via get, get-config, or
notification) to these data nodes.
There are no read-only data nodes defined in this model.
Some of the RPC operations in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control access to these operations.
There are no RPC operations defined in this model.
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The approach described in this document enhances the ability to
authenticate a BFD session by taking away the onerous requirement
that every BFD control packet be strongly authenticated. By strongly
authenticating packets that affect the state of the session, the
security of the BFD session is maintained. In this mode, packets
that are a significant change but are not strongly authenticated, are
dropped by the system. Therefore, a malicious user that tries to
inject a non-authenticated packet; e.g. with a Down state to take a
session down will fail. That combined with the proposal of using
sequence number defined in Meticulous Keyed ISAAC for BFD
Authentication [I-D.ietf-bfd-secure-sequence-numbers] further
enhances the security of BFD sessions.
8. Contributors
The authors of this document would like to acknowledge Reshad Rahman
as a contributor to this document.
9. Acknowledgments
The authors would like to thank Qiufang Ma and Stephen Farrell for
providing directorate review of this document.
10. References
10.1. Normative References
[I-D.ietf-bfd-secure-sequence-numbers]
DeKok, A., Jethanandani, M., Agarwal, S., Mishra, A., and
A. Saxena, "Meticulous Keyed ISAAC for BFD
Authentication", Work in Progress, Internet-Draft, draft-
ietf-bfd-secure-sequence-numbers-18, 21 October 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-bfd-
secure-sequence-numbers-18>.
[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>.
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[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>.
[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>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[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>.
[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>.
[RFC8177] Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
Zhang, "YANG Data Model for Key Chains", RFC 8177,
DOI 10.17487/RFC8177, June 2017,
<https://www.rfc-editor.org/info/rfc8177>.
[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>.
[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>.
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[RFC9127] Rahman, R., Ed., Zheng, L., Ed., Jethanandani, M., Ed.,
Pallagatti, S., and G. Mirsky, "YANG Data Model for
Bidirectional Forwarding Detection (BFD)", RFC 9127,
DOI 10.17487/RFC9127, October 2021,
<https://www.rfc-editor.org/info/rfc9127>.
[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>.
10.2. Informative References
[I-D.ietf-bfd-stability]
Mishra, A., Jethanandani, M., Saxena, A., Pallagatti, S.,
and M. Chen, "BFD Stability", Work in Progress, Internet-
Draft, draft-ietf-bfd-stability-18, 7 April 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-bfd-
stability-18>.
[RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
DOI 10.17487/RFC1321, April 1992,
<https://www.rfc-editor.org/info/rfc1321>.
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, DOI 10.17487/RFC2026, October 1996,
<https://www.rfc-editor.org/info/rfc2026>.
[RFC6151] Turner, S. and L. Chen, "Updated Security Considerations
for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
RFC 6151, DOI 10.17487/RFC6151, March 2011,
<https://www.rfc-editor.org/info/rfc6151>.
[RFC6194] Polk, T., Chen, L., Turner, S., and P. Hoffman, "Security
Considerations for the SHA-0 and SHA-1 Message-Digest
Algorithms", RFC 6194, DOI 10.17487/RFC6194, March 2011,
<https://www.rfc-editor.org/info/rfc6194>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[SHA-1-attack1]
Wang, X., Yin, Y., and H. Yu, "Finding Collisions in the
Full SHA-1", 2005.
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[SHA-1-attack2]
Wang, X., Yao, A., and F. Yao, "New Collision Search for
SHA-1", 2005.
Appendix A. Updated BFD IANA Module
This section carries the updated IANA BFD Module, iana-bfd-types.yang
module, first defined in YANG Data Model for Bidirectional Forward
Detection (BFD) [RFC9127]. The updated module carries three new
authentication type enum definitions, 'null' with a suggested value
of 6, and 'optimized-md5-meticulous-keyed-isaac' with a suggested
value of 7, and 'optimized-sha1-meticulous-keyed-isaac' with a
suggested value of 8. Note, the null enum type is used by BFD
Stability [I-D.ietf-bfd-stability] only, but is being defined here to
make sure changes to this YANG module do not cause a conflict. This
module should replace the version that currently exists in the IANA
registry.
<CODE BEGINS> file "iana-bfd-types@2025-04-16.yang"
module iana-bfd-types {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:iana-bfd-types";
prefix iana-bfd-types;
organization
"IANA";
contact
"Internet Assigned Numbers Authority
Postal: ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094-2536
United States of America
Tel: +1 310 301 5800
<mailto:iana@iana.org>";
description
"This module defines YANG data types for IANA-registered
BFD parameters.
This YANG module is maintained by IANA and reflects the
'BFD Diagnostic Codes' and 'BFD Authentication Types'
registries.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
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the license terms contained in, the Simplified 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).
The initial version of this YANG module is part of RFC 9127;
see the RFC itself for full legal notices.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
revision 2025-04-16 {
description
"Add NULL and Meticulous ISAAC authentication type.";
reference
"RFC XXXX: Optimizing BFD Authentication,
I-D.ietf-bfd-stability: BFD Stability.";
}
revision 2021-10-21 {
description
"Initial revision.";
reference
"RFC 9127: YANG Data Model for Bidirectional Forwarding
Detection (BFD)";
}
/*
* Type definitions
*/
typedef diagnostic {
type enumeration {
enum none {
value 0;
description
"No Diagnostic.";
}
enum control-expiry {
value 1;
description
"Control Detection Time Expired.";
}
enum echo-failed {
value 2;
description
"Echo Function Failed.";
}
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enum neighbor-down {
value 3;
description
"Neighbor Signaled Session Down.";
}
enum forwarding-reset {
value 4;
description
"Forwarding Plane Reset.";
}
enum path-down {
value 5;
description
"Path Down.";
}
enum concatenated-path-down {
value 6;
description
"Concatenated Path Down.";
}
enum admin-down {
value 7;
description
"Administratively Down.";
}
enum reverse-concatenated-path-down {
value 8;
description
"Reverse Concatenated Path Down.";
}
enum mis-connectivity-defect {
value 9;
description
"Mis-connectivity defect.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)
RFC 6428: Proactive Connectivity Verification, Continuity
Check, and Remote Defect Indication for the MPLS
Transport Profile";
}
}
description
"BFD diagnostic codes as defined in RFC 5880. Values are
maintained in the 'BFD Diagnostic Codes' IANA registry.
Range is 0 to 31.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD)";
}
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typedef auth-type {
type enumeration {
enum reserved {
value 0;
description
"Reserved.";
}
enum simple-password {
value 1;
description
"Simple Password.";
}
enum keyed-md5 {
value 2;
description
"Keyed MD5.";
}
enum meticulous-keyed-md5 {
value 3;
description
"Meticulous Keyed MD5.";
}
enum keyed-sha1 {
value 4;
description
"Keyed SHA1.";
}
enum meticulous-keyed-sha1 {
value 5;
description
"Meticulous Keyed SHA1.";
}
enum null {
value 6;
description
"NULL Auth. Used for stability measurement.";
}
enum optimized-md5-meticulous-keyed-isaac {
value 7;
description
"BFD Optimized Authentication using Meticulous Keyed
MD5 as the strong authentication and Meticulous Keyed
ISAAC as the 'optimized' authentication.";
}
enum optimized-sha1-meticulous-keyed-isaac {
value 8;
description
"BFD Optimized Authentication using Meticulous Keyed
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SHA-1 as the strong authentication and Meticulous Keyed
ISAAC as the 'optimized' authentication.";
}
}
description
"BFD authentication type as defined in RFC 5880. Values are
maintained in the 'BFD Authentication Types' IANA registry.
Range is 0 to 255.";
reference
"RFC 5880: Bidirectional Forwarding Detection (BFD),
I-D.ietf-bfd-optimizing-authentication:
Optimizing BFD Authentication,
I-D.ietf-bfd-stability: BFD Stability.";
}
}
<CODE ENDS>
Appendix B. Examples
This section tries to show some examples in how the model can be
configured.
B.1. Single Hop BFD Configuration
This example demonstrates how a Single Hop BFD session can be
configured for optimized authentication.
=============== NOTE: '\' line wrapping per RFC 8792 ===============
<?xml version="1.0" encoding="UTF-8"?>
<key-chains
xmlns="urn:ietf:params:xml:ns:yang:ietf-key-chain">
<key-chain>
<name>bfd-auth-config</name>
<description>"An example for BFD Optimized Auth configuration."\
</description>
<key>
<key-id>55</key-id>
<lifetime>
<send-lifetime>
<start-date-time>2017-01-01T00:00:00Z</start-date-time>
<end-date-time>2017-02-01T00:00:00Z</end-date-time>
</send-lifetime>
<accept-lifetime>
<start-date-time>2016-12-31T23:59:55Z</start-date-time>
<end-date-time>2017-02-01T00:00:05Z</end-date-time>
</accept-lifetime>
</lifetime>
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<crypto-algorithm xmlns:opt-auth=
"urn:ietf:params:xml:ns:yang:ietf-bfd-opt-auth">opt-auth:opti\
mized-sha1-meticulous-keyed-isaac</crypto-algorithm>
<key-string>
<keystring>testvector</keystring>
</key-string>
</key>
</key-chain>
</key-chains>
<interfaces
xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
xmlns:if-type="urn:ietf:params:xml:ns:yang:iana-if-type">
<interface>
<name>eth0</name>
<type>if-type:ethernetCsmacd</type>
</interface>
</interfaces>
<routing
xmlns="urn:ietf:params:xml:ns:yang:ietf-routing"
xmlns:bfd-types="urn:ietf:params:xml:ns:yang:ietf-bfd-types"
xmlns:iana-bfd-types="urn:ietf:params:xml:ns:yang:iana-bfd-type\
s"
xmlns:opt-auth="urn:ietf:params:xml:ns:yang:ietf-bfd-opt-auth">
<control-plane-protocols>
<control-plane-protocol>
<type>bfd-types:bfdv1</type>
<name>name:BFD</name>
<bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
<ip-sh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh">
<sessions>
<session>
<interface>eth0</interface>
<dest-addr>2001:db8:0:113::101</dest-addr>
<desired-min-tx-interval>10000</desired-min-tx-interv\
al>
<required-min-rx-interval>
10000
</required-min-rx-interval>
<authentication>
<key-chain>bfd-auth-config</key-chain>
<opt-auth:reauth-interval>30</opt-auth:reauth-inter\
val>
</authentication>
</session>
</sessions>
</ip-sh>
</bfd>
</control-plane-protocol>
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</control-plane-protocols>
</routing>
Authors' Addresses
Mahesh Jethanandani
Arrcus
United States of America
Email: mjethanandani@gmail.com
Ashesh Mishra
Aalyria Technologies
Email: ashesh@aalyria.com
Ankur Saxena
Ciena Corporation
3939 N 1st Street
San Jose, CA 95134
United States of America
Email: ankurpsaxena@gmail.com
Manav Bhatia
Google
Doddanekkundi
Bangalore 560048
India
Email: mnvbhatia@google.com
Jeffrey Haas
Juniper Networks
Email: jhaas@pfrc.org
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