Internet DRAFT - draft-haas-idr-bfd-subcode
draft-haas-idr-bfd-subcode
Inter-Domain Routing J. Haas
Internet-Draft Juniper Networks
Intended status: Standards Track 5 January 2022
Expires: 9 July 2022
BGP Cease Notification Subcode For BFD
draft-haas-idr-bfd-subcode-00
Abstract
The Bidirectional Forwarding Detection protocol (BFD) is used to
detect loss of connectivity between two forwarding elements,
typically with low latency. BFD is leveraged by routing protocols,
including the Border Gateway Protocol (BGP), to use that detection of
loss of connectivity to bring down the 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
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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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 9 July 2022.
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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
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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 . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 4
7.2. Informative References . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Bidirectional Forwarding Detection protocol (BFD) [RFC5880] is
used to detect loss of connectivity between two forwarding elements,
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 action when a BFD session goes
down [RFC5882]. This is typically used by the clients to take faster
action in terminating their connections than the native protocol
timers might allow.
The Border Gateway Protocol, Version 4 (BGP) [RFC4271] uses a Hold
Timer to terminate sessions when the implementation does not receive
a BGP message within the negotiated Hold Time interval. The minimum
Hold Time interval supported by the protocol is three seconds. The
Hold Timer may be optionally negotiated to being disabled with a Hold
Time interval of zero.
If a BGP implementation desires to have its sessions terminate faster
than the supported BGP Hold Timer can accommodate upon loss of
connectivity, BFD is used to supply that faster detection. When the
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BFD session goes Down, the BGP implementation terminates the session.
BGP will send a NOTIFICATION message, if possible, and then close the
TCP connection for the session.
2. BFD Cease NOTIFICATION Subcode
The value (TBD) has been allocated by IANA for the "BFD Down" Cease
NOTIFICATION message Subcode.
When a BGP session 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 sessions make choices for what BFD timers are used based on a
variety of inputs for stability vs. fast failure depending on the
role BGP is playing for the deployment.
In the event of a BGP session 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 the BGP NOTIFICATION
message with the BFD Down Subcode. The receiving BGP Speaker will
then have an understanding that the session is being terminated
because of a BFD-detected issue and not an issue with the BGP
implementation.
When there is a total loss of connectivity between two BGP Speakers,
it may not be possible for the NOTIFICATION message to have been
sent. Even so, BGP implementations may provide this reason as part
of their operational state; e.g. bgpPeerLastError in the BGP MIB.
[RFC4273].
When the procedures in [RFC8538] for sending a NOTIFICATION message
with a Cease Code and Hard Reset Subcode, and the session 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
IANA is requested to allocate a new value from the BGP Cease
NOTIFICATION message subcodes registry with the Name "BFD Down", and
a Reference of this document.
6. Acknowledgments
TBD
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>.
7.2. Informative References
[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>.
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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>.
Author's Address
Jeffrey Haas
Juniper Networks
Email: jhaas@juniper.net
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