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Versions: (draft-gandhishah-teas-assoc-corouted-bidir) 00 01 02 03 04 05 06 07

TEAS Working Group                                        R. Gandhi, Ed.
Internet-Draft                                       Cisco Systems, Inc.
Intended Status: Standards Track                                 H. Shah
Expires: November 25, 2017                                         Ciena
                                                            J. Whittaker
                                                                 Verizon
                                                            May 24, 2017


                      Fast Reroute Procedures for
          Associated Bidirectional Label Switched Paths (LSPs)
               draft-ietf-teas-assoc-corouted-bidir-frr-01


Abstract

   Resource Reservation Protocol (RSVP) association signaling can be
   used to bind two unidirectional 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
   describes Fast Reroute (FRR) procedures for both single-sided and
   double-sided provisioned associated bidirectional LSPs.  The FRR
   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 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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   time.  It is inappropriate to use Internet-Drafts as reference
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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   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 . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
     2.1.  Key Word Definitions . . . . . . . . . . . . . . . . . . .  4
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
       2.2.1.  Forward Unidirectional LSPs  . . . . . . . . . . . . .  4
       2.2.2.  Reverse Co-routed Unidirectional LSPs  . . . . . . . .  4
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Fast Reroute Bypass Tunnel Assignment  . . . . . . . . . .  5
     3.2.  Node Protection Bypass Tunnels . . . . . . . . . . . . . .  6
     3.3.  Bidirectional LSP Association At Mid-Points  . . . . . . .  7
   4.  Signaling Procedure  . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Bidirectional LSP Fast Reroute . . . . . . . . . . . . . .  8
       4.1.1.  Re-corouting with Node Protection Bypass Tunnels . . .  9
       4.1.2.  Unidirectional Link Failures . . . . . . . . . . . . .  9
       4.1.3.  Revertive Behavior After Fast Reroute  . . . . . . . .  9
       4.1.4.  Bypass Tunnel Provisioning . . . . . . . . . . . . . . 10
     4.2.  Bidirectional LSP Association At Mid-points  . . . . . . . 10
   5.  Message and Object Definitions . . . . . . . . . . . . . . . . 10
     5.1.  Extended ASSOCIATION Object  . . . . . . . . . . . . . . . 10
   6.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . . . 12
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15










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1.  Introduction

   The Resource Reservation Protocol (RSVP) (Extended) ASSOCIATION
   Object is specified in [RFC6780] which can be used generically to
   associate (G)Multi-Protocol Label Switching (MPLS) Traffic
   Engineering (TE) Label Switched Paths (LSPs).  [RFC7551] defines
   mechanisms for binding two point-to-point unidirectional LSPs
   [RFC3209] into an associated bidirectional LSP.  There are two models
   described in [RFC7551] for provisioning an associated bidirectional
   LSP, single-sided and double-sided.  In both models, the reverse LSP
   of the bidirectional LSP may or may not be co-routed and follow the
   same path as its forward LSP.

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.
    The Stateful PCE allows stateful control of the MPLS TE LSPs which
   may be initiated by the PCE or a PCC.  As defined in [PCE-ASSOC-
   BIDIR], a Stateful PCE can be employed to initiate single-sided and
   double-sided associated bidirectional LSPs on PCC(s).

   In packet transport networks, there are requirements where the
   reverse LSP of a bidirectional LSP needs to follow the same path as
   its forward LSP [RFC6373].  The MPLS Transport Profile (TP) [RFC6370]
   architecture facilitates the co-routed bidirectional LSP by using the
   GMPLS extensions [RFC3473] to achieve congruent paths.  However, the
   RSVP association signaling allows to enable co-routed bidirectional
   LSPs without having to deploy GMPLS extensions in the existing
   networks.  The association signaling also allows to take advantage of
   the existing TE and Fast Reroute (FRR) mechanisms in the network.

   [RFC4090] defines FRR extensions for MPLS TE LSPs and those are also
   applicable to the associated bidirectional LSPs.  [GMPLS-FRR] defines
   FRR procedure for GMPLS signaled bidirectional LSPs, such as, co-
   ordinate bypass tunnel assignments in the forward and reverse
   directions of the LSP.  The mechanisms defined in [GMPLS-FRR] are
   also useful for the FRR of associated bidirectional LSPs.

   This document describes FRR procedures for both single-sided and
   double-sided provisioned associated bidirectional LSPs.  The FRR
   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.

1.1.  Assumptions and Considerations

   The following assumptions and considerations apply to this document:




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   o  The FRR procedure to co-ordinate the bypass tunnel assignment
      defined in this document may be used for non-corouted associated
      bidirectional protected LSPs but requires that the downstream PLR
      and MP pair of the forward LSP matches the upstream MP and PLR
      pair of the reverse LSP.

   o  The FRR procedure when using the unidirectional bypass tunnels is
      defined in [RFC4090] and is not modified by this document.

   o  This document assumes that the FRR bypass tunnels used for
      associated bidirectional protected LSPs are also bidirectional.

   o  The FRR bypass tunnels used for co-routed associated bidirectional
      protected LSPs are assumed to be co-routed.


2.  Conventions Used in This Document

2.1.  Key Word Definitions

   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 RFC 2119 [RFC2119].

2.2.  Terminology

   The reader is assumed to be familiar with the terminology defined in
   [RFC2205], [RFC3209], [RFC4090], [RFC7551], and [GMPLS-FRR].

2.2.1.  Forward Unidirectional LSPs

   Two reverse unidirectional point-to-point (P2P) LSPs are setup in the
   opposite directions between a pair of source and destination nodes to
   form an associated bidirectional LSP.  In the case of single-sided
   provisioned LSP, the originating LSP with REVERSE_LSP Object is
   identified as a forward unidirectional LSP.  In the case of double-
   sided provisioned LSP, the LSP originating from the higher node
   address (as source) and terminating on the lower node address (as
   destination) is identified as a forward unidirectional LSP.

2.2.2.  Reverse Co-routed Unidirectional LSPs

   Two reverse unidirectional point-to-point (P2P) LSPs are setup in the
   opposite directions between a pair of source and destination nodes to
   form an associated bidirectional LSP.  A reverse unidirectional LSP
   originates on the same node where the forward unidirectional LSP
   terminates, and it terminates on the same node where the forward
   unidirectional LSP originates.  A reverse co-routed unidirectional



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   LSP traverses along the same path as the forward direction
   unidirectional LSP in the opposite direction.


3.  Overview

   As specified in [RFC7551], in the single-sided provisioning case, the
   RSVP TE tunnel is configured only on one endpoint node of the
   bidirectional LSP.  An LSP for this tunnel is initiated by the
   originating endpoint with (Extended) ASSOCIATION Object containing
   Association Type set to "single-sided associated bidirectional LSP"
   and REVERSE_LSP Object inserted in the RSVP Path message.  The remote
   endpoint then creates the corresponding reverse TE tunnel and signals
   the reverse LSP in response using the information from the
   REVERSE_LSP Object and other objects present in the received RSVP
   Path message.  As specified in [RFC7551], in the double-sided
   provisioning case, the RSVP TE tunnel is configured on both endpoint
   nodes of the bidirectional LSP.  Both forward and reverse LSPs are
   initiated independently by the two endpoints with (Extended)
   ASSOCIATION Object containing Association Type set to "double-sided
   associated bidirectional LSP".  With both single-sided and double-
   sided provisioned bidirectional LSPs, the reverse LSP may or may not
   be congruent (i.e. co-routed) and follow the same path as its forward
   LSP.

   Both single-sided and double-sided associated bidirectional LSPs
   require solutions to the following issues for fast reroute to ensure
   co-routedness after a failure event.

3.1.  Fast Reroute Bypass Tunnel Assignment

   In order to ensure that the traffic flows on a co-routed path after a
   link or node failure on the co-routed protected LSP path, the mid-
   point Point of Local Repair (PLR) nodes need to assign matching
   bidirectional bypass tunnels for fast reroute.  Such bypass
   assignment requires co-ordination between the forward and reverse
   direction PLR nodes when more than one bypass tunnels are present on
   a PLR node.













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                      <-- Bypass N -->
                  +-----+         +-----+
                  |  H  +---------+  I  |
                  +--+--+         +--+--+
                     |               |
                     |               |
          LSP1 -->   |   LSP1 -->    |   LSP1 -->       LSP1 -->
   +-----+        +--+--+         +--+--+        +-----+        +-----+
   |  A  +--------+  B  +----X----+  C  +--------+  D  +--------+  E  |
   +-----+        +--+--+         +--+--+        +-----+        +-----+
          <-- LSP2   |    <-- LSP2   |   <-- LSP2       <-- LSP2
                     |               |
                     |               |
                  +--+--+         +--+--+
                  |  F  +---------+  G  |
                  +-----+         +-----+
                      <-- Bypass S -->

            Figure 1: Multiple Bidirectional Bypass Tunnels

   As shown in Figure 1, there are two bypass tunnels available, Bypass
   tunnel N (on path B-H-I-C) and Bypass tunnel S (on path B-F-G-C).
   The mid-point PLR nodes B and C need to co-ordinate bypass tunnel
   assignment to ensure that traffic in both directions flow through
   either on the Bypass tunnel N (on path B-H-I-C) or the Bypass tunnel
   S (on path B-F-G-C), after the link B-C failure.

3.2.  Node Protection Bypass Tunnels

   When using a node protection bypass tunnel with a bidirectional
   protected LSP, after a link failure, the forward and reverse LSP
   traffic can flow on different node protection bypass tunnels in the
   upstream and downstream directions.


              <-- Bypass N -->
   +-----+                        +-----+
   |  H  +------------------------+  I  |
   +--+--+                        +--+--+
      |      <-- Rerouted-LSP2       |
      |                              |
      |                              |
      |   LSP1 -->       LSP1 -->    |   LSP1 -->       LSP1 -->
   +--+--+        +-----+         +--+--+        +-----+        +-----+
   |  A  +--------+  B  +----X----+  C  +--------+  D  +--------+  E  |
   +-----+        +--+--+         +-----+        +--+--+        +-----+
          <-- LSP2   |    <-- LSP2       <-- LSP2   |   <-- LSP2
                     |                              |



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                     |                              |
                     |       Rerouted-LSP1 -->      |
                  +--+--+                        +--+--+
                  |  F  +------------------------+  G  |
                  +-----+                        +-----+
                             <-- Bypass S -->

                 Figure 2: Node Protection Bypass Tunnels

   As shown in Figure 2, after the link B-C failure, the downstream PLR
   node B reroutes the protected forward LSP1 traffic over the bypass
   tunnel S (on path B-F-G-D) to reach downstream MP node D whereas the
   upstream PLR node C reroute the protected reverse LSP2 traffic over
   the bypass tunnel N (on path C-I-H-A) to reach the upstream MP node
   A.  As a result, the traffic in the forward and revere directions
   flows on different bypass tunnels and this can cause the co-routed
   bidirectional LSP to become non-corouted.  However, unlike GMPLS
   LSPs, the asymmetry of paths in the forward and reverse directions
   does not result in RSVP soft-state time-out with the associated
   bidirectional LSPs.

3.3.  Bidirectional LSP Association At Mid-Points

   In packet transport networks, a restoration LSP is signaled after a
   link failure on the protected LSP path and the protected LSP may or
   may not be torn down [RFC8131].  In this case, multiple forward and
   reverse LSPs of a co-routed bidirectional LSP may be present at mid-
   point nodes with identical (Extended) ASSOCIATION Objects.  This
   creates an ambiguity at mid-point nodes to identify the correct
   associated LSP pair for fast reroute bypass assignment (e.g. during
   the recovery phase of RSVP graceful restart procedure).


          LSP3 -->                       LSP3 -->       LSP3 -->
          LSP1 -->       LSP1 -->        LSP1 -->       LSP1 -->
   +-----+        +-----+         +-----+        +-----+        +-----+
   |  A  +--------+  B  +----X----+  C  +--------+  D  +--------+  E  |
   +-----+        +--+--+         +--+--+        +-----+        +-----+
          <-- LSP2   |    <-- LSP2   |   <-- LSP2       <-- LSP2
          <-- LSP4   |               |   <-- LSP4       <-- LSP4
                     |               |
                     |   LSP3 -->    |
                  +--+--+         +--+--+
                  |  F  +---------+  G  |
                  +-----+         +-----+
                      <-- Bypass S -->
                          <-- LSP4




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          Figure 3: Restoration LSP Set-up After Link Failure

   As shown in Figure 3, the protected LSPs LSP1 and LSP2 are an
   associated LSP pair, similarly the restoration LSPs LSP3 and LSP4 are
   an associated LSP pair, both pairs belong to the same associated
   bidirectional LSP and carry identical (Extended) ASSOCIATION Objects.
    In this example, the mid-point node D may mistakenly associate LSP1
   with the reverse LSP4 instead of the reverse LSP3 due to the matching
   (Extended) ASSOCIATION Objects.  This may cause the co-routed
   bidirectional LSP to become non-corouted.  Since the bypass
   assignment needs to be co-ordinated between the forward and reverse
   LSPs, this can also lead to undesired bypass tunnel assignments.


4.  Signaling Procedure

4.1.  Bidirectional LSP Fast Reroute

   For both single-sided and double-sided associated bidirectional LSPs,
   the fast reroute procedure specified in [RFC4090] is used.  In
   addition, the mechanisms defined in [GMPLS-FRR] are used as
   following.

   o  The BYPASS_ASSIGNMENT subobject defined in [GMPLS-FRR] is used to
      co-ordinate bypass tunnel assignment between the forward and
      reverse direction PLR nodes (see Figure 1).  The BYPASS_ASSIGNMENT
      and Node-ID address [RFC4561] subobjects MUST be added by the
      downstream PLR node in the RECORD_ROUTE Object (RRO) of the RSVP
      Path message of the forward LSP to indicate the bypass tunnel
      assignment.  The upstream PLR node MUST NOT add the
      BYPASS_ASSIGNMENT subobject in the RRO of the RSVP Path message of
      the reverse LSP.

   o  The downstream PLR node always initiates the bypass tunnel
      assignment for the forward LSP.  The upstream PLR (forward
      direction LSP MP) node simply reflects the bypass tunnel
      assignment for the reverse direction LSP.  The upstream PLR node
      MUST NOT initiate the bypass tunnel assignment.

   o  If the bypass tunnel is not found, the upstream PLR SHOULD send a
      Notify message [RFC3473] with Error-code - "FRR Bypass Assignment
      Error" and Sub-code - "Bypass Tunnel Not Found" [GMPLS-FRR] to the
      downstream PLR.

   o  If the bypass tunnel can not be used due to a local policy as
      described in Section 4.5.3 in [GMPLS-FRR], the upstream PLR SHOULD
      send a Notify message [RFC3473] with Error-code - "FRR Bypass
      Assignment Error" and Sub-code - "Bypass Assignment Cannot Be



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      Used" [GMPLS-FRR] to the downstream PLR.

   o  After a link or node failure, the PLR nodes in both forward and
      reverse directions trigger fast reroute independently using the
      procedures defined in [RFC4090] and send the forward and reverse
      LSP RSVP Path messages and traffic over the bypass tunnel.

4.1.1.  Re-corouting with Node Protection Bypass Tunnels

   After fast reroute, the downstream MP node assumes the role of
   upstream PLR and reroutes the reverse LSP RSVP Path messages and
   traffic over the bypass tunnel on which the forward LSP RSVP Path
   messages and traffic are received.  This is defined as re-corouting
   procedure in [GMPLS-FRR].  This procedure is used to ensure that both
   forward and reverse LSP signaling and traffic flow on the same
   bidirectional bypass tunnel after fast reroute.

   As shown in Figure 2, when using a node protection bypass tunnel with
   co-routed protected LSPs, asymmetry of paths can occur in the forward
   and reverse directions after a link failure [GMPLS-FRR].  In order to
   restore co-routedness, the downstream MP node D (acting as an
   upstream PLR) SHOULD trigger re-coroute procedure and reroute the
   reverse protected LSP2 RSVP Path messages and traffic over the bypass
   tunnel S (on path D-G-F-B) to the upstream MP node B.  The upstream
   PLR node C stops receiving the RSVP Path messages and traffic for the
   reverse LSP2 from node D and it stops sending the RSVP Path messages
   for the reverse LSP2 on the bypass tunnel N (on path C-I-H-A).

4.1.2.  Unidirectional Link Failures

   The unidirectional link failures can cause co-routed bidirectional
   LSPs to become non-corouted after fast reroute with both link
   protection and node protection bypass tunnels.  The asymmetry of
   forward and reverse LSP paths due to the unidirectional link failure
   in the downstream direction can be corrected by using the
   re-corouting procedure specified in Section 4.1.1 of this document.
   In any case, the unidirectional link failures in the upstream and/or
   downstream directions do not result in RSVP soft-state time-out with
   the associated bidirectional LSPs.

4.1.3.  Revertive Behavior After Fast Reroute

   When the revertive behavior is desired for a protected LSP after the
   link is restored, the procedure defined in [RFC4090], Section 6.5.2,
   is followed.

   o  The upstream and downstream PLR nodes independently start sending
      the RSVP Path messages and traffic flow of the protected LSP over



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      the restored link and stop sending them over the bypass tunnel
      [RFC4090].

   o  In case of node protection bypass tunnels (see Figure 2), after
      re-corouting, the upstream PLR node D SHOULD start sending RSVP
      Path messages and traffic for the reverse LSP over the original
      link (D-C) when it receives the RSVP Path messages and traffic for
      the forward LSP over it and stops sending them over the bypass
      tunnel S.

4.1.4.  Bypass Tunnel Provisioning

   Fast reroute bidirectional bypass tunnels can be single-sided or
   double-sided associated tunnels.  For both single-sided and double-
   sided associated bypass tunnels, the fast reroute assignment policies
   need to be configured on the downstream PLR nodes of the protected
   LSPs that initiate the bypass tunnel assignments.  For single-sided
   associated bypass tunnels, these nodes are the originating nodes of
   their signaling.


4.2.  Bidirectional LSP Association At Mid-points

   In order to associate the LSPs unambiguously at a mid-point node (see
   Figure 3), the endpoint node MUST signal Extended ASSOCIATION Object
   and add unique Extended Association ID for each associated forward
   and reverse LSP pair forming the bidirectional LSP.  As an example,
   an endpoint node MAY set the Extended Association ID to the value
   specified in Section 5.1 of this document.

   o  For single-sided provisioned bidirectional LSPs [RFC7551], the
      originating endpoint signals the Extended ASSOCIATION Object with
      a unique Extended Association ID.  The remote endpoint copies the
      contents of the received Extended ASSOCIATION Object including the
      Extended Association ID in the RSVP Path message of the reverse
      LSP's Extended ASSOCIATION Object.

   o  For double-sided provisioned bidirectional LSPs [RFC7551], both
      endpoints need to ensure that the bidirectional LSP has a unique
      Extended ASSOCIATION Object for each forward and reverse LSP pair
      by selecting appropriate unique Extended Association IDs signaled
      by them.


5.  Message and Object Definitions

5.1.  Extended ASSOCIATION Object




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   The Extended Association ID in the Extended ASSOCIATION Object
   [RFC6780] can be set to the value specified as following to uniquely
   identify associated forward and reverse LSP pair of a bidirectional
   LSP.

   IPv4 Extended Association ID format is shown below:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    IPv4 LSP Source Address                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Reserved            |            LSP-ID             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     :                                                               :
     :                      Variable Length ID                       :
     :                                                               :
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 4: IPv4 Extended Association ID Format

   LSP Source Address

      IPv4 source address of the forward LSP [RFC3209].

   LSP-ID

      16-bits LSP-ID of the forward LSP [RFC3209].

   Variable Length ID

      Variable length ID inserted by the endpoint node of the associated
      bidirectional LSP [RFC6780].



   IPv6 Extended Association ID format is shown below:

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +                                                               +
     |                    IPv6 LSP Source Address                    |
     +                                                               +
     |                          (16 bytes)                           |
     +                                                               +
     |                                                               |



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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Reserved            |            LSP-ID             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     :                                                               :
     :                      Variable Length ID                       :
     :                                                               :
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 5: IPv6 Extended Association ID Format

   LSP Source Address

      IPv6 source address of the forward LSP [RFC3209].

   LSP-ID

      16-bits LSP-ID of the forward LSP [RFC3209].

   Variable Length ID

      Variable length ID inserted by the endpoint node of the associated
      bidirectional LSP [RFC6780].


6.  Compatibility

   This document describes the procedures for fast reroute for
   associated bidirectional LSPs.  Operators wishing to use this
   function SHOULD ensure that it is supported on the nodes on the LSP
   path.


7.  Security Considerations

   This document uses the signaling mechanisms defined in [RFC7551] and
   [GMPLS-FRR] and does not introduce any additional security
   considerations other than those already covered in [RFC7551], [GMPLS-
   FRR] and the MPLS/GMPLS security framework [RFC5920].


8.  IANA Considerations

   This document does not require any IANA actions.








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9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2205]  Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, September 1997.

   [RFC4090]  Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
              Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              May 2005.

   [RFC4561]  Vasseur, J.P., Ed., Ali, Z., and S. Sivabalan, "Definition
              of a Record Route Object (RRO) Node-Id Sub-Object", RFC
              4561, June 2006.

   [RFC6780]  Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP
              Association Object Extensions", RFC 6780, October 2012.

   [RFC7551]  Zhang, F., Ed., Jing, R., and Gandhi, R., Ed., "RSVP-TE
              Extensions for Associated Bidirectional LSPs", RFC 7551,
              May 2015.

   [GMPLS-FRR]  Taillon, M., Saad, T., Ed., Gandhi, R., Ed., Ali, Z.,
              and M. Bhatia, "Extensions to Resource Reservation
              Protocol For Fast Reroute of Traffic Engineering GMPLS
              LSPs", draft-ietf-teas-gmpls-lsp-fastreroute (work in
              progress).

9.2.  Informative References

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, December 2001.

   [RFC3473]  Berger, L., "Generalized Multi-Protocol Label Switching
              (GMPLS) Signaling Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.

   [RFC5920]  Fang, L., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

   [RFC6370]  Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
              Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.




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   [RFC6373]  Andersson, L., Berger, L., Fang, L., Bitar, N., and E.
              Gray, "MPLS Transport Profile (MPLS-TP) Control Plane
              Framework", RFC 6373, September 2011.

   [RFC8131]  Zhang, X., Zheng, H., Ed., Gandhi, R., Ed., Ali, Z.,
              Brzozowski, P., "RSVP-TE Signaling Procedure for End-to-
              End GMPLS Restoration and Resource Sharing", RFC 8131,
              March 2017.

   [PCE-ASSOC-BIDIR]  Barth, C., Gandhi, R., and B. Wen, "PCEP
              Extensions for Associated Bidirectional Label Switched
              Paths (LSPs)", draft-barth-pce-association-bidir (work in
              progress).






































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Acknowledgments

   A special thanks to the authors of [GMPLS-FRR], this document uses
   the mechanisms defined in that document.


Authors' Addresses

   Rakesh Gandhi (editor)
   Cisco Systems, Inc.

   Email: rgandhi@cisco.com


   Himanshu Shah
   Ciena

   Email: hshah@ciena.com


   Jeremy Whittaker
   Verizon

   Email: jeremy.whittaker@verizon.com



























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