Updates to the Fast Reroute Procedures for Co-routed Associated Bidirectional Label Switched Paths (LSPs)
RFC 8537

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Internet Engineering Task Force (IETF)                    R. Gandhi, Ed.
Request for Comments: 8537                           Cisco Systems, Inc.
Updates: 4090, 7551                                              H. Shah
Category: Standards Track                                          Ciena
ISSN: 2070-1721                                             J. Whittaker
                                                                 Verizon
                                                           February 2019

    Updates to the Fast Reroute Procedures for Co-routed Associated
               Bidirectional Label Switched Paths (LSPs)

Abstract

   Resource Reservation Protocol (RSVP) association signaling can be
   used to bind two unidirectional Label Switched Paths (LSPs) into an
   associated bidirectional LSP.  When an associated bidirectional LSP
   is co-routed, the reverse LSP follows the same path as its forward
   LSP.  This document updates the fast reroute procedures defined in
   RFC 4090 to support both single-sided and double-sided provisioned
   associated bidirectional LSPs.  This document also updates the
   procedure for associating two reverse LSPs defined in RFC 7551 to
   support co-routed bidirectional LSPs.  The fast reroute procedures
   can ensure that, for the co-routed LSPs, traffic flows on co-routed
   paths in the forward and reverse directions after a failure event.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8537.

Gandhi, et al.               Standards Track                    [Page 1]
RFC 8537        Associated Bidirectional LSP Fast Reroute  February 2019

Copyright Notice

   Copyright (c) 2019 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/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. Introduction ....................................................3
      1.1. Assumptions and Considerations .............................4
   2. Conventions Used in This Document ...............................4
      2.1. Key Word Definitions .......................................4
      2.2. Terminology ................................................4
           2.2.1. Forward Unidirectional LSPs .........................5
           2.2.2. Reverse Co-routed Unidirectional LSPs ...............5
   3. Problem Statement ...............................................5
      3.1. Fast Reroute Bypass Tunnel Assignment ......................6
      3.2. Node Protection Bypass Tunnels .............................6
      3.3. Bidirectional LSP Association at Midpoints .................7
   4. Signaling Procedure .............................................8
      4.1. Associated Bidirectional LSP Fast Reroute ..................8
           4.1.1. Restoring Co-routing with Node Protection
                  Bypass Tunnels ......................................9
           4.1.2. Unidirectional Link Failures .......................10
           4.1.3. Revertive Behavior after Fast Reroute ..............10
           4.1.4. Bypass Tunnel Provisioning .........................10
           4.1.5. One-to-One Bypass Tunnel ...........................11
      4.2. Bidirectional LSP Association at Midpoints ................11
   5. Compatibility ..................................................11
   6. Security Considerations ........................................12
   7. IANA Considerations ............................................12
   8. References .....................................................12
      8.1. Normative References ......................................12
      8.2. Informative References ....................................13
   Appendix A.  Extended Association ID ..............................14
   Acknowledgments ...................................................16
   Authors' Addresses ................................................16

Gandhi, et al.               Standards Track                    [Page 2]