A BGP Cease Notification Subcode For Bidirectional Forwarding Detection (BFD)
draft-ietf-idr-bfd-subcode-04

Inter-Domain Routing                                             J. Haas
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                         13 October 2022
Expires: 16 April 2023

A BGP Cease Notification Subcode For Bidirectional Forwarding Detection
                                 (BFD)
                     draft-ietf-idr-bfd-subcode-04

Abstract

   The Bidirectional Forwarding Detection (BFD) protocol 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 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", "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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 16 April 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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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  BFD Cease NOTIFICATION Subcode  . . . . . . . . . . . . . . .   3
   3.  Operational Considerations  . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   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 quickly trigger closure of their connections 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 of [RFC4271], the minimum Hold Time interval
   supported by the protocol must be either zero, or at least three
   seconds.

   If a BGP speaker desires to have its connections terminate faster
   than the negotiated BGP Hold Timer can accommodate upon loss of
   connectivity with a neighbor, the BGP speakers can rely upon BFD is

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   used to supply that faster detection.  When the BFD session state
   changes to Down, the BGP speaker terminates the connection with a
   NOTIFICATION message sent to the neighbor, if possible, and then
   close the TCP connection for the connection.

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 be 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, 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.

4.  Security Considerations

   This document introduces no additional BGP security considerations.

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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 with the Name "BFD Down", and a Reference
   of 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., "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., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [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>.

   [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>.

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   [RFC8538]  Patel, K., Fernando, R., Scudder, J., and J. Haas,
              "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-14, 3
              July 2022, <https://www.ietf.org/archive/id/draft-ietf-
              idr-bgp-model-14.txt>.

   [RFC4273]  Haas, J., Ed. and S. Hares, Ed., "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. and V. Gillet, "Subcodes for BGP Cease
              Notification Message", RFC 4486, DOI 10.17487/RFC4486,
              April 2006, <https://www.rfc-editor.org/info/rfc4486>.

   [RFC5882]  Katz, D. and D. Ward, "Generic Application of
              Bidirectional Forwarding Detection (BFD)", RFC 5882,
              DOI 10.17487/RFC5882, June 2010,
              <https://www.rfc-editor.org/info/rfc5882>.

Author's Address

   Jeffrey Haas
   Juniper Networks
   Email: jhaas@juniper.net

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