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Versions: (draft-tsaad-ccamp-rsvpte-bidir-lsp-fastreroute) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 8271

TEAS Working Group                                            M. Taillon
Internet-Draft                                              T. Saad, Ed.
Intended Status: Standards Track                          R. Gandhi, Ed.
Expires: January 29, 2016                                         Z. Ali
                                                   (Cisco Systems, Inc.)
                                                               M. Bhatia
                                                                  L. Jin

                                                           July 28, 2015


    Extensions to Resource Reservation Protocol For Fast Reroute of
                  Traffic Engineering GMPLS LSPs
            draft-ietf-teas-gmpls-lsp-fastreroute-03


Abstract

   This document defines Resource Reservation Protocol - Traffic
   Engineering (RSVP-TE) signaling extensions to support Fast Reroute
   (FRR) of Packet Switched Capable (PSC) Generalized Multi-Protocol
   Label Switching (GMPLS) Label Switched Paths (LSPs).  These signaling
   extensions allow the coordination of bidirectional bypass tunnel
   assignment protecting a common facility in both forward and reverse
   directions of a co-routed bidirectional LSP.  In addition, these
   extensions enable the re-direction of bidirectional traffic and
   signaling onto bypass tunnels that ensure co-routedness of data and
   signaling paths in the forward and reverse directions after FRR to
   avoid RSVP soft-state timeout.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html




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   The list of Internet-Draft Shadow Directories can be accessed at
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Copyright and License Notice

   Copyright (c) 2015 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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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions Used in This Document  . . . . . . . . . . . . . .  4
     2.1.  Key Word Definitions . . . . . . . . . . . . . . . . . . .  4
     2.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Fast Reroute For Unidirectional GMPLS LSPs . . . . . . . . . .  5
   4.  Bypass Tunnel Assignment for Bidirectional GMPLS LSPs  . . . .  5
     4.1.  Merge Point Labels . . . . . . . . . . . . . . . . . . . .  5
     4.2.  Merge Point Addresses  . . . . . . . . . . . . . . . . . .  6
     4.3.  RRO IPv4/IPv6 Subobject Flags  . . . . . . . . . . . . . .  6
     4.4.  Bypass Tunnel Assignment Co-ordination . . . . . . . . . .  6
       4.4.1.  Bypass Tunnel Assignment Signaling Procedure . . . . .  6
       4.4.2.  Bypass Tunnel Assignment Policy  . . . . . . . . . . .  7
       4.4.3.  BYPASS_ASSIGNMENT Subobject  . . . . . . . . . . . . .  8
   5.  Link Protection Bypass Tunnels for Bidirectional GMPLS LSPs  .  9
     5.1.  Behavior Post Link Failure After FRR . . . . . . . . . . . 10
     5.2.  Revertive Behavior Post Link Failure After FRR . . . . . . 10
   6.  Node Protection Bypass Tunnels for Bidirectional GMPLS LSPs  . 10
     6.1.  Behavior Post Link Failure After FRR . . . . . . . . . . . 11
     6.2.  Behavior Post Link Failure To Re-coroute . . . . . . . . . 11
     6.3.  Revertive Behavior Post Link Failure . . . . . . . . . . . 13
   7.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . . . 13
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   10.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 14
     10.1.  Normative References  . . . . . . . . . . . . . . . . . . 14
     10.2.  Informative References  . . . . . . . . . . . . . . . . . 14
   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 15



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   Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16


1.  Introduction

   Packet Switched Capable (PSC) Traffic Engineering (TE) tunnels are
   signaled using Generalized Multi-Protocol Label Switching (GMPLS)
   signaling procedures specified in [RFC3473] for both unidirectional
   and bidirectional LSPs.  Fast Reroute (FRR) [RFC4090] has been widely
   deployed in the packet TE networks today and is preferred for TE
   GMPLS tunnels.  Using FRR methods also allows to leverage existing
   mechanisms for failure detection and restoration in the deployed
   networks.

   FRR procedures defined in [RFC4090] describe the behavior of the
   Point of Local Repair (PLR) to reroute traffic and signaling onto the
   bypass tunnel in the event of a failure for unidirectional LSPs.
   These procedures are applicable to unidirectional protected LSPs
   signaled using either RSVP-TE [RFC3209] or GMPLS procedures
   [RFC3473], however don't address issues that arise when employing FRR
   for bidirectional co-routed GMPLS Label Switched Paths (LSPs).

   When bidirectional bypass tunnels are used to locally protect
   bidirectional co-routed GMPLS LSPs, the upstream and downstream PLRs
   may independently assign different bidirectional bypass tunnels in
   the forward and reverse directions.  There is no mechanism in FRR
   procedures defined in [RFC4090] to coordinate the bidirectional
   bypass tunnel selection between the downstream and upstream PLRs.

   When using FRR procedures with bidirectional co-routed GMPLS LSPs, it
   is possible in some cases (e.g. when using node protection bypass
   tunnels post a link failure event and when RSVP signaling is sent
   in-fiber and in-band with data), the RSVP signaling refreshes may
   stop reaching some nodes along the primary bidirectional LSP path
   after the PLRs complete rerouting traffic and signaling onto the
   bypass tunnels.  This is caused by the asymmetry of paths that may be
   taken by the bidirectional LSP's signaling in the forward and reverse
   directions after FRR reroute.  In such cases, the RSVP soft-state
   timeout eventually causes the protected bidirectional LSP to be
   destroyed, and consequently impacts protected traffic flow after FRR.

   Protection State Coordination Protocol [RFC6378] is applicable to FRR
   [RFC4090] for local protection of bidirectional co-routed LSPs in
   order to minimize traffic disruptions in both directions.  However,
   this does not address the above mentioned problem of RSVP soft-state
   timeout in control plane.




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   This document proposes solutions to the above mentioned problems by
   providing mechanisms in the control plane to complement FRR
   procedures of [RFC4090] in order to maintain the RSVP soft-state for
   bidirectional co-routed protected GMPLS LSPs and achieve symmetry in
   the paths followed by the traffic and signaling in the forward and
   reverse directions post FRR.  The document further extends RSVP
   signaling so that the bidirectional bypass tunnel selected by the
   upstream PLR matches the one selected by the downstream PLR node for
   a bidirectional co-routed LSP.

   Unless otherwise specified in this document, fast reroute procedures
   defined in [RFC4090] are not modified for GMPLS signaled tunnels.

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 in
   [RFC2205] and [RFC3209].

   LSR: An MPLS Label-Switch Router.

   LSP: An MPLS Label-Switched Path.

   Local Repair: Techniques used to repair LSP tunnels quickly when a
   node or link along the LSP's path fails.

   PLR: Point of Local Repair.  The head-end LSR of a bypass tunnel or a
   detour LSP.

   PSC: Packet Switched Capable.

   Protected LSP: An LSP is said to be protected at a given hop if it
   has one or multiple associated bypass tunnels originating at that
   hop.

   Bypass Tunnel: An LSP that is used to protect a set of LSPs passing
   over a common facility.

   NHOP Bypass Tunnel: Next-Hop Bypass Tunnel.  A bypass tunnel that
   bypasses a single link of the protected LSP.




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   NNHOP Bypass Tunnel: Next-Next-Hop Bypass Tunnel.  A bypass tunnel
   that bypasses a single node of the protected LSP.

   MP: Merge Point. The LSR where one or more bypass tunnels rejoin the
   path of the protected LSP downstream of the potential failure.  The
   same LSR may be both an MP and a PLR simultaneously.

   Downstream PLR: A PLR that locally detects a fault and reroutes
   traffic in the same direction of the protected bidirectional LSP RSVP
   Path signaling.  A downstream PLR has a corresponding downstream MP.

   Upstream PLR: A PLR that locally detects a fault and reroutes traffic
   in the opposite direction of the protected bidirectional LSP RSVP
   Path signaling.  An upstream PLR has a corresponding upstream MP.

   Point of Remote Repair (PRR): An upstream PLR that triggers reroute
   of traffic and signaling based on procedures described in this
   document.


3.  Fast Reroute For Unidirectional GMPLS LSPs

   FRR procedures defined in [RFC4090] are applicable to unidirectional
   protected LSPs signaled using either RSVP-TE or GMPLS procedures and
   are not modified by the extensions defined in this document.  These
   FRR procedures also apply to bidirectional associated GMPLS LSPs
   where two unidirectional GMPLS LSPs are bound together by using
   association signaling [RFC7551].

4.  Bypass Tunnel Assignment for Bidirectional GMPLS LSPs

   This section describes signaling procedures for bidirectional bypass
   tunnel assignment for GMPLS signaled PSC bidirectional co-routed TE
   LSPs.

4.1.  Merge Point Labels

   To correctly reroute data traffic over a node protection bypass
   tunnel, the downstream and upstream PLRs have to know, in advance,
   the downstream and upstream Merge Point (MP) labels so that data in
   the forward and reverse directions can be tunneled through the bypass
   tunnel post FRR respectively.

   [RFC4090] defines procedures for the downstream PLR to obtain the
   protected LSP's downstream MP label from recorded labels in the RRO
   of the RSVP Resv message received at the downstream PLR.

   To obtain the upstream MP label, existing methods [RFC4090] to record



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   upstream MP label are used in the RRO of the RSVP Path message.  The
   upstream PLR can obtain the upstream MP label from the recorded label
   in the RRO of the received RSVP Path message.

4.2.  Merge Point Addresses

   To correctly assign a bidirectional bypass tunnel, the downstream and
   upstream PLRs have to know, in advance, the downstream and upstream
   Merge Point (MP) addresses.  [RFC4561] defines procedures for the PLR
   to obtain the protected LSP's merge point address in multi-domain
   routing networks where a domain is defined as an Interior Gateway
   Protocol (IGP) area or an Autonomous System (AS).

   [RFC4561] defines procedures for the downstream PLR to obtain the
   protected LSP's downstream merge point address from the recorded
   node-IDs in the RRO of the RSVP Resv message received at the
   downstream PLR.

   To obtain the upstream MP address, existing methods [RFC4561] to
   record upstream MP node-ID are used in the RRO of the RSVP Path
   message.  The upstream PLR can obtain the upstream MP address from
   the recorded node-IDs in the RRO of the received RSVP Path message.

4.3.  RRO IPv4/IPv6 Subobject Flags

   RRO IPv4/IPv6 subobject flags are defined in [RFC4090], Section 4.4
   and are applicable to the FRR procedure for the bidirectional GMPLS
   tunnels.

   [RFC4090] defined procedure is used by the downstream PLR
   independently to signal the Ipv4/IPv6 subobject flags in the RRO of
   the RSVP Path message.  Similarly, this procedure is used by the
   upstream PLR independently to signal the IPv4/IPv6 subobject flags in
   the RRO of the RSVP Resv message.

4.4.  Bypass Tunnel Assignment Co-ordination

   This document defines signaling procedure and a new BYPASS_ASSIGNMENT
   subobject in RSVP RECORD_ROUTE object used to co-ordinate the
   bidirectional bypass tunnel selection between the downstream and
   upstream PLRs.

4.4.1.  Bypass Tunnel Assignment Signaling Procedure

   It is desirable to coordinate the bidirectional bypass tunnel
   selected at the downstream and upstream PLRs so that rerouted traffic
   and signaling flow on co-routed paths post FRR.  To achieve this, a
   new RSVP subobject is defined for RECORD_ROUTE object (RRO) that



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   identifies a bidirectional bypass tunnel that is assigned at a
   downstream PLR to protect a bidirectional LSP.

   The BYPASS_ASSIGNMENT subobject is added by each downstream PLR in
   the RSVP Path RECORD_ROUTE message of the GMPLS signaled
   bidirectional primary LSP to record the downstream bidirectional
   bypass tunnel assignment.  This subobject is sent in the RSVP Path
   RECORD_ROUTE message every time the downstream PLR assigns or updates
   the bypass tunnel assignment so the upstream PLR may reflect the
   assignment too.

   When the BYPASS_ASSIGNMENT subobject is added in the RECORD_ROUTE
   object:

     o The BYPASS_ASSIGNMENT subobject MUST be added prior to the node-
   ID subobject containing the node's address.

     o The Node-ID subobject MUST also be added.

     o The IPv4 or IPv6 subobject MUST also be added.

   In the absence of BYPASS_ASSIGNMENT subobject, the upstream PLR
   SHOULD NOT assign a bypass tunnel in the reverse direction.  This
   allows the downstream PLR to always initiate the bypass assignment
   and upstream PLR to simply reflect the bypass assignment.

   The upstream PLR (downstream MP) that detects a BYPASS_ASSIGNMENT
   subobject, whose bypass tunnel and the node-ID subobject when used as
   a "bypass tunnel source" terminates locally, assigns the matching
   bidirectional bypass tunnel in the reverse direction, and forwards
   the RSVP Path message downstream.  Otherwise, the bypass tunnel
   assignment subobject is simply forwarded downstream along in the RSVP
   Path message.

   Bypass assignment co-ordination procedure described above can be used
   for both one-to-one backup described in Section 3.1 of [RFC4090] and
   facility backup described in Section 3.2 of [RFC4090].

4.4.2.  Bypass Tunnel Assignment Policy

   In the case of upstream PLR receiving multiple BYPASS_ASSIGNMENT
   subobjects from multiple downstream PLRs, the decision of selecting a
   bypass tunnel in the reverse direction can be based on a local
   policy, for example, prefer link protection versus node protection
   bypass tunnel, or prefer the most upstream versus least upstream node
   protection bypass tunnel.  However, it is recommended that nodes
   along the LSP path employ identical policy for bypass tunnel
   assignment.



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   When different policies are used for bypass tunnel assignment on the
   LSP path, it may result in some links in the reverse direction not
   assigned bypass protection as shown in examples below.

   As shown in Example 1, node A assigns a node protection bypass tunnel
   in the forward direction but node C does not assign a node protection
   bypass tunnel in the reverse direction for a protected bidirectional
   GMPLS LSP.  Both nodes B and C assign a link protection bypass
   tunnel.  As a result, there is no fast reroute protection available
   in the reverse direction for link A-B for this LSP.


                      +------->>------+
                     /          +->>-+ \
                    /          /      \ \
                   /          /        \ \
                  A -------- B --------- C
                              \        /
                               \      /
                                +-<<-+

         Example 1: An example of different bypass assignment policy


   As shown in Example 2, nodes A and C assign a node protection bypass
   tunnel for a protected bidirectional GMPLS LSP.  Node B assigns a
   link protection bypass tunnel but node C does not assign a reverse
   link protection bypass tunnel.  As a result, there is no fast reroute
   protection available in the reverse direction for link A-B for this
   LSP.


                      +------>>------+
                     /          +->>-+ \
                    /          /      \ \
                   /          /        \ \
                  A -------- B --------- C
                   \                     /
                    \                   /
                     \                 /
                      +------<<-------+

         Example 2: An example of different bypass assignment policy


4.4.3.  BYPASS_ASSIGNMENT Subobject

   The BYPASS_ASSIGNMENT subobject is used to inform the MP of the



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   bypass tunnel being assigned by the PLR.  This can be used to
   coordinate the bypass tunnel assignment for the protected LSP by the
   downstream and upstream PLRs in the forward and reverse directions
   respectively prior or post the failure occurrence.  This subobject
   SHOULD only be inserted into the RSVP Path message by the downstream
   PLR and MUST NOT be changed by downstream LSRs.

   The BYPASS_ASSIGNMENT subobject in RRO has the following format:

          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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |       Type    |      Length   |      Bypass Tunnel ID         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type

            Downstream Bypass Assignment.

      Length

            The Length contains the total length of the subobject in
       bytes, including the Type and Length fields.

      Bypass Tunnel ID

            The bypass tunnel identifier (16 bits).


5.  Link Protection Bypass Tunnels for Bidirectional GMPLS LSPs

   When a bidirectional link protection bypass tunnel is used, after a
   link failure, downstream PLR reroutes RSVP Path and traffic over
   bypass tunnel using procedures defined in [RFC4090].  Upstream PLR
   may reroute traffic and RSVP Resv upon detecting the link failure or
   upon receiving RSVP Path message over a bidirectional bypass tunnel.
   This allows both traffic and RSVP signaling to flow on symmetric
   paths in the forward and reverse directions of a bidirectional
   tunnel.

                                                <-RESV
            [R1]---[R2]----[R3]------x-----[R4]-----[R5]
               -> PATH       \              /
                              +<<-------->>+
                                    T3
                                -> PATH
                                   RESV <-



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            Protected LSP:  {R1-R2-R3-R4-R5}
            R3's Bypass T3: {R3-R4}

         Figure 1: Flow of RSVP signaling post FRR after link failure

   Consider the Traffic Engineered (TE) network shown in Figure 1.
   Assume every link in the network is protected with a link protection
   bypass tunnel (e.g. bypass tunnel T3).  For the protected
   bidirectional co-routed LSP whose (active) head-end is on router R1
   and (passive) tail-end is on router R5, each traversed router (a
   potential PLR) assigns a link protection bidirectional co-routed
   bypass tunnel.

5.1.  Behavior Post Link Failure After FRR

   Consider a link R3-R4 on the protected LSP path fails.  The
   downstream PLR R3 and upstream PLR R4 independently trigger fast
   reroute procedures to redirect traffic onto bypass tunnels T3 in the
   forward and reverse directions.  The downstream PLR R3 also reroutes
   RSVP Path state onto the bypass tunnel T3 using procedures described
   in [RFC4090].  The upstream PLR R4 reroutes RSVP Resv onto the
   reverse bypass tunnel T3 upon receiving RSVP Path message over bypass
   tunnel T3.

5.2.  Revertive Behavior Post Link Failure After FRR

   Revertive behavior as defined in [RFC4090], Section 6.5.2, is
   applicable to the link protection of GMPLS bidirectional LSPs.  When
   using the local revertive mode, when downstream MP receives Path
   messages over the restored path, it starts sending Resv over the
   restored path and stops sending Resv over the reverse bypass tunnel.
   No additional procedure other than that specified in [RFC4090] is
   introduced for revertive behavior by this document.


6.  Node Protection Bypass Tunnels for Bidirectional GMPLS LSPs


                            T1
                       +<<--------->>+
                      /               \       <-RESV
            [R1]---[R2]----[R3]--x--[R4]---[R5]---[R6]
               -> PATH       \               /
                              +<<--------->>+
                                     T2


            Protected LSP:  {R1-R2-R3-R4-R5-R6}



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            R3's Bypass T2: {R3-R5}
            R4's Bypass T1: {R4-R2}

       Figure 2: Flow of RSVP signaling post FRR after link failure

   Consider the Traffic Engineered (TE) network shown in Figure 2.
   Assume every link in the network is protected with a node protection
   bypass tunnel.  For the protected bidirectional co-routed LSP whose
   (active) head-end is on router R1 and (passive) tail-end is on router
   R6, each traversed router (a potential PLR) assigns a node protection
   bidirectional co-routed bypass tunnel.

   The proposed solution introduces two phases to invoking FRR
   procedures by the PLR post the link failure.  The first phase
   comprises of FRR procedures to fast reroute data traffic onto bypass
   tunnels in the forward and reverse directions.  The second phase
   re-coroutes the data and signaling in the forward and reverse
   directions after the first phase.

6.1.  Behavior Post Link Failure After FRR

   Consider a link R3-R4 on the protected LSP path fails.  The
   downstream PLR R3 and upstream PLR R4 independently trigger fast
   reroute procedures to redirect traffic onto respective bypass tunnels
   T2 and T1 in the forward and reverse directions.  The downstream PLR
   R3 also reroutes RSVP Path state onto the bypass tunnel T2 using
   procedures described in [RFC4090].  Note, at this point, router R4
   stops receiving RSVP Path refreshes for the protected bidirectional
   LSP while primary protected traffic continues to flow over bypass
   tunnels.

6.2.  Behavior Post Link Failure To Re-coroute

   The downstream Merge Point (MP) R5 that receives rerouted protected
   LSP RSVP Path message through the bypass tunnel, in addition to the
   regular MP processing defined in [RFC4090], gets promoted to a Point
   of Remote Repair (PRR role) and performs the following actions to
   re-coroute signaling and data traffic over the same path in both
   directions:

      o Finds the bypass tunnel in the reverse direction
        that terminates on the Downstream PLR R3.  Note: the Downstream
        PLR R3's address is extracted from the "IPV4 tunnel sender
        address" in the SENDER_TEMPLATE object.

      o If reverse bypass tunnel is found and the primary LSP traffic
        and signaling are not already rerouted over the found bypass
        tunnel, the PRR R5 activates FRR reroute procedures to direct



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        traffic and RSVP Resv over the found bypass tunnel T2 in the
        reverse direction.

      o If reverse bypass tunnel is not found, the PRR R5 signals a new
        reverse bypass tunnel that terminates on the downstream PLR R3
        and activates FRR reroute procedures over the new bypass tunnel
        to direct traffic and RSVP Resv in the reverse direction.

      o If reverse bypass tunnel can not be successfully signaled,
        the PRR R5 immediately tears down the primary LSP.


   If downstream MP R5 receives multiple RSVP Path messages through
   multiple bypass tunnels (e.g. as a result of multiple failures), the
   PRR SHOULD identify a bypass tunnel that terminates on the farthest
   downstream PLR along the protected LSP path (closest to the primary
   bidirectional tunnel head-end) and activate the reroute procedures
   mentioned above.

                                              <- RESV
            [R1]---[R2]----[R3]--X--[R4]---[R5]---[R6]
              PATH ->        \             /
                              +<<------->>+
                             Bypass Tunnel T2
                            traffic + signaling

                 Protected LSP:  {R1-R2-R3-R4-R5-R6}
                 R3's Bypass T2: {R3-R5}

        Figure 3: Flow of RSVP signaling post FRR after re-corouted


   Figure 3 describes the path taken by the traffic and signaling after
   completing re-coroute of data and signaling in the forward and
   reverse paths described earlier.

   The downstream MP MAY optionally support re-corouting in data plane
   as follows.  If the downstream MP is pre-configured with
   bidirectional bypass tunnel, as soon as the MP node receives the
   primary tunnel packets on this bypass tunnel, it MAY switch the
   upstream traffic on to this bypass tunnel.  In order to identify the
   primary tunnel packets through this bypass tunnel, Penultimate Hop
   Popping (PHP) of the bypass tunnel MUST be disabled.  The signaling
   procedure described above in this Section will still apply, and MP
   checks whether the primary tunnel traffic and signaling is already
   rerouted over the found bypass tunnel, if not, perform the above
   signaling procedure.




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6.3.  Revertive Behavior Post Link Failure

   Revertive behavior as defined in [RFC4090], Section 6.5.2, is
   applicable to node protection of GMPLS bidirectional LSPs.  When
   using the local revertive mode, when downstream MP (R4) (before
   re-corouting) and PRR (R5) (after re-corouting) receive Path messages
   over the restored path, they start sending Resv over the restored
   path and stop sending Resv over the reverse bypass tunnel.  No
   additional procedure other than that specified in [RFC4090] is
   introduced for revertive behavior by this document.

7.  Compatibility

   New RSVP subobject BYPASS_ASSIGNMENT is defined for RECORD_ROUTE
   Object in this document.  Per [RFC2205], nodes not supporting this
   subobject will ignore the subobject but forward it without
   modification.

8.  Security Considerations

   This document introduces one new RSVP subobject that is carried in a
   signaling message.  Thus in the event of the interception of a
   signaling message, slightly more information about the state of the
   network could be deduced than was previously the case.  This is
   judged to be a very minor security risk as this information is
   already available by other means.

   Otherwise, this document introduces no additional security
   considerations.  For general discussion on MPLS and GMPLS related
   security issues, see the MPLS/GMPLS security framework [RFC5920].

9.  IANA Considerations

   IANA manages the "RSVP PARAMETERS" registry located at
   <http://www.iana.org/assignments/rsvp-parameters>.  IANA is requested
   to assign a value for the new BYPASS_ASSIGNMENT subobject in the
   "Class Type 21 ROUTE_RECORD - Type 1 Route Record" registry.

   This document introduces a new RECORD_ROUTE subobject:

   +--------+-------------------+---------+---------+---------------+
   | Value  | Description       | Carried | Carried | Reference     |
   |        |                   | in Path | in Resv |               |
   +--------+-------------------+---------+---------+---------------+
   | TBA By | BYPASS_ASSIGNMENT | Yes     | No      | This document |
   | IANA   | subobject         |         |         |               |
   +--------+-------------------+---------+---------+---------------+




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10.  References

10.1.  Normative References


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

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

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

   [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.

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



10.2.  Informative References

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

   [RFC6378]  Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and
              A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear
              Protection", RFC 6378, October 2011.








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Acknowledgements

   Authors would like to thank George Swallow for his detailed and
   useful comments and suggestions.  Authors would also like to thank
   Nobo Akiya, Loa Andersson and Gregory Mirsky for reviewing this
   document.


Contributors


   Frederic Jounay
   Orange CH

   EMail: frederic.jounay@orange.ch




































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Authors' Addresses

   Mike Taillon
   Cisco Systems, Inc.

   EMail: mtaillon@cisco.com


   Tarek Saad (editor)
   Cisco Systems, Inc.

   EMail: tsaad@cisco.com


   Rakesh Gandhi (editor)
   Cisco Systems, Inc.

   EMail: rgandhi@cisco.com


   Zafar Ali
   Cisco Systems, Inc.

   EMail: zali@cisco.com


   Manav Bhatia
   India

   EMail: manav@ionosnetworks.com


   Lizhong Jin
   Shanghai, China

   EMail: lizho.jin@gmail.com















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