Internet-Draft BGP Cease Notification Subcode for BFD December 2022
Haas Expires 30 June 2023 [Page]
Inter-Domain Routing
Intended Status:
Standards Track
J. Haas
Juniper Networks

A BGP Cease Notification Subcode For Bidirectional Forwarding Detection (BFD)


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

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.

Table of Contents

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 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.


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.

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 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

Bradner, S. and RFC Publisher, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
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, , <>.
Katz, D., Ward, D., and RFC Publisher, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, , <>.
Katz, D., Ward, D., and RFC Publisher, "Generic Application of Bidirectional Forwarding Detection (BFD)", RFC 5882, DOI 10.17487/RFC5882, , <>.
Leiba, B. and RFC Publisher, "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
Patel, K., Fernando, R., Scudder, J., Haas, J., and RFC Publisher, "Notification Message Support for BGP Graceful Restart", RFC 8538, DOI 10.17487/RFC8538, , <>.

7.2. Informative References

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, , <>.
Haas, J., Ed., Hares, S., Ed., and RFC Publisher, "Definitions of Managed Objects for BGP-4", RFC 4273, DOI 10.17487/RFC4273, , <>.
Chen, E., Gillet, V., and RFC Publisher, "Subcodes for BGP Cease Notification Message", RFC 4486, DOI 10.17487/RFC4486, , <>.

Author's Address

Jeffrey Haas
Juniper Networks