Internet DRAFT - draft-ietf-idr-bfd-subcode
draft-ietf-idr-bfd-subcode
Inter-Domain Routing J. Haas
Internet-Draft Juniper Networks
Intended status: Standards Track 27 December 2022
Expires: 30 June 2023
A BGP Cease Notification Subcode For Bidirectional Forwarding Detection
(BFD)
draft-ietf-idr-bfd-subcode-05
Abstract
The Bidirectional Forwarding Detection (BFD) protocol [RFC 5880] is
used to detect loss of connectivity between two forwarding engines,
typically with low latency. BFD is leveraged by routing protocols,
including the Border Gateway Protocol (BGP), to bring down routing
protocol connections faster than the native protocol timers.
This document defines a Subcode for the BGP Cease NOTIFICATION
message [RFC4271], Section 6.7, for when a BGP connection is being
closed due to a BFD session going down.
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.
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 30 June 2023.
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Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BFD Cease NOTIFICATION Subcode . . . . . . . . . . . . . . . 3
3. Operational Considerations . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Bidirectional Forwarding Detection (BFD) protocol [RFC5880] is
used to detect loss of connectivity between two forwarding engines,
typically with low latency. BFD is utilized as a service for various
clients, including routing protocols, to provide an advisory
mechanism for those clients to take appropriate actions when a BFD
session goes down [RFC5882]. This is typically used by the clients
to trigger closure of their connections more quickly than the native
protocol timers might allow.
The Border Gateway Protocol, Version 4 (BGP) [RFC4271] terminates its
connections upon Hold Timer expiration when the speaker does not
receive a BGP message within the negotiated Hold Time interval. As
per Section 4.2 and Section 4.4 of [RFC4271], the minimum Hold Time
interval is at least three seconds, unless KEEPALIVE processing has
been disabled by negotiating the distinguished Hold Time of zero.
If a BGP speaker desires to have its connections terminate more
quickly than the negotiated BGP Hold Timer can accommodate upon loss
of connectivity with a neighbor, the BFD protocol can be relied upon
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by BGP speakers to supply that faster detection. When the BFD
session state changes to Down, the BGP speaker terminates the
connection with a Cease NOTIFICATION message sent to the neighbor, if
possible, and then closes the TCP connection for the session.
This document defines a subcode, "BFD Down", to be sent with the
Cease NOTIFICATION message that indicates the reason for this type of
connection termination.
2. BFD Cease NOTIFICATION Subcode
The value 10 has been allocated by IANA for the "BFD Down" Cease
NOTIFICATION message Subcode.
When a BGP connection is terminated due to a BFD session going into
the Down state, the BGP speaker SHOULD send a NOTIFICATION message
with the Error Code Cease and the Error Subcode "BFD Down".
3. Operational Considerations
A BFD session may go Down when there is only a partial loss of
connectivity between two BGP speakers. Operators using BFD for their
BGP connections make choices for what BFD timers are used based upon
a variety of criteria; for example, stability vs. fast failure.
In the event of a BGP connection being terminated due to a BFD Down
event from partial loss of connectivity as detected by BFD, the
remote BGP speaker might be able to receive a BGP Cease NOTIFICATION
message with the BFD Down Subcode. The receiving BGP speaker will
then have an understanding that the connection is being terminated
because of a BFD-detected issue and not an issue with the BGP
speaker.
When there is a total loss of connectivity between two BGP speakers,
it may not have been possible for the Cease NOTIFICATION message to
have been sent. Even so, BGP speakers SHOULD provide this reason as
part of their operational state. Examples include bgpPeerLastError
in the BGP MIB [RFC4273], and "last-error" in
[I-D.ietf-idr-bgp-model].
When the procedures in [RFC8538] for sending a NOTIFICATION message
with a Cease Code and Hard Reset Subcode are required, and the BGP
connection is being terminated because BFD has gone Down, the BFD
Down Subcode SHOULD be encapsulated in the Hard Reset's data portion
of the NOTIFICATION message.
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4. Security Considerations
Similar to [RFC4486], this document defines a subcode for the BGP
Cease NOTIFICATION message that provides information to aid network
operators in correlating network events and diagnosing BGP peering
issues. This subcode is purely informational and has no impact on
the BGP Finite State Machine beyond that already documented by
[RFC4271], Section 6.7.
5. IANA Considerations
NOTE TO IANA and the RFC Editor: IANA is requested to make the
temporary allocation below permanent. The RFC Editor is requested to
delete this note to IANA prior to publication.
IANA has assigned the value 10 from the BGP Cease NOTIFICATION
message subcodes registry (https://www.iana.org/assignments/bgp-
parameters/bgp-parameters.xhtml#bgp-parameters-8) with the Name "BFD
Down", and a Reference to this document.
6. Acknowledgments
Thanks to Jeff Tantsura, and Dale Carder for their comments on the
draft.
Mohamed Boucadair provided feedback as part of Routing Directorate
review of this document.
Bruno Rijsman had a substantively similar proposal to this document
in 2006; draft-rijsman-bfd-down-subcode. That draft did not progress
in IDR at that time. The author of this draft was unaware of Bruno's
prior work when creating this proposal.
7. References
7.1. Normative References
[RFC2119] Bradner, S. and RFC Publisher, "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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., Hares, S., Ed., and RFC
Publisher, "A Border Gateway Protocol 4 (BGP-4)",
RFC 4271, DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
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[RFC5880] Katz, D., Ward, D., and RFC Publisher, "Bidirectional
Forwarding Detection (BFD)", RFC 5880,
DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5882] Katz, D., Ward, D., and RFC Publisher, "Generic
Application of Bidirectional Forwarding Detection (BFD)",
RFC 5882, DOI 10.17487/RFC5882, June 2010,
<https://www.rfc-editor.org/info/rfc5882>.
[RFC8174] Leiba, B. and RFC Publisher, "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>.
[RFC8538] Patel, K., Fernando, R., Scudder, J., Haas, J., and RFC
Publisher, "Notification Message Support for BGP Graceful
Restart", RFC 8538, DOI 10.17487/RFC8538, March 2019,
<https://www.rfc-editor.org/info/rfc8538>.
7.2. Informative References
[I-D.ietf-idr-bgp-model]
Jethanandani, M., Patel, K., Hares, S., and J. Haas, "BGP
YANG Model for Service Provider Networks", Work in
Progress, Internet-Draft, draft-ietf-idr-bgp-model-15, 13
October 2022, <https://www.ietf.org/archive/id/draft-ietf-
idr-bgp-model-15.txt>.
[RFC4273] Haas, J., Ed., Hares, S., Ed., and RFC Publisher,
"Definitions of Managed Objects for BGP-4", RFC 4273,
DOI 10.17487/RFC4273, January 2006,
<https://www.rfc-editor.org/info/rfc4273>.
[RFC4486] Chen, E., Gillet, V., and RFC Publisher, "Subcodes for BGP
Cease Notification Message", RFC 4486,
DOI 10.17487/RFC4486, April 2006,
<https://www.rfc-editor.org/info/rfc4486>.
Author's Address
Jeffrey Haas
Juniper Networks
Email: jhaas@juniper.net
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