Clarifying Procedures for Establishing BFD Sessions for MPLS Label Switched Paths (LSPs)
RFC 7726

Document Type RFC - Proposed Standard (January 2016; No errata)
Updates RFC 5884
Last updated 2016-01-29
Replaces draft-grmas-bfd-rfc5884-clarifications
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Jeffrey Haas
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IESG IESG state RFC 7726 (Proposed Standard)
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Responsible AD Alvaro Retana
Send notices to aretana@cisco.com
IANA IANA review state Version Changed - Review Needed
IANA action state No IC
Internet Engineering Task Force (IETF)                       V. Govindan
Request for Comments: 7726                                  K. Rajaraman
Updates: 5884                                              Cisco Systems
Category: Standards Track                                      G. Mirsky
ISSN: 2070-1721                                                 Ericsson
                                                                N. Akiya
                                                     Big Switch Networks
                                                               S. Aldrin
                                                                  Google
                                                            January 2016

        Clarifying Procedures for Establishing BFD Sessions for
                    MPLS Label Switched Paths (LSPs)

Abstract

   This document clarifies the procedures for establishing, maintaining,
   and removing multiple, concurrent BFD (Bidirectional Forwarding
   Detection) sessions for a given <MPLS LSP, FEC> as described in RFC
   5884.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7726.

Govindan, et al.             Standards Track                    [Page 1]
RFC 7726               Clarifications to RFC 5884           January 2016

Copyright Notice

   Copyright (c) 2016 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Theory of Operation . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Procedures for Establishment of Multiple BFD Sessions . .   3
     2.2.  Procedures for Maintenance of Multiple BFD Sessions . . .   4
     2.3.  Procedures for Removing BFD Sessions at the Egress LSR  .   4
     2.4.  Changing Discriminators for a BFD Session . . . . . . . .   5
   3.  Backwards Compatibility . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Background

   [RFC5884] defines the procedures to bootstrap and maintain BFD
   sessions for an <MPLS LSP, FEC> using a Label Switched Path (LSP)
   ping.  While Section 4 of [RFC5884] specifies that multiple BFD
   sessions can be established for an <MPLS LSP, FEC> tuple, the
   procedures to bootstrap and maintain multiple BFD sessions
   concurrently over an <MPLS LSP, FEC> are not clearly specified.
   Additionally, the procedures of removing BFD sessions bootstrapped on
   the egress Label Switching Router (LSR) are unclear.  This document
   provides those clarifications without deviating from the principles
   outlined in [RFC5884].

Govindan, et al.             Standards Track                    [Page 2]
RFC 7726               Clarifications to RFC 5884           January 2016

   The ability for an ingress LSR to establish multiple BFD sessions for
   an <MPLS LSP, FEC> tuple is useful in scenarios such as LSPs based on
   Segment Routing [SEG-ROUTING] or LSPs having Equal-Cost Multipath
   (ECMP).  The process used by the ingress LSR to determine the number
   of BFD session(s) to be bootstrapped for an <MPLS LSP, FEC> tuple and
   the mechanism used to construct those session(s) are outside the
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