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For this RFC, original HTML is available from the RFC-Editor: RFC8796

PROPOSED STANDARD

Internet Engineering Task Force (IETF)                        M. Taillon
Request for Comments: 8796                           Cisco Systems, Inc.
Updates: 4090                                               T. Saad, Ed.
Category: Standards Track                               Juniper Networks
ISSN: 2070-1721                                                R. Gandhi
                                                     Cisco Systems, Inc.
                                                             A. Deshmukh
                                                        Juniper Networks
                                                                 M. Jork
                                                          128 Technology
                                                               V. Beeram
                                                        Juniper Networks
                                                               July 2020


 RSVP-TE Summary Fast Reroute Extensions for Label Switched Path (LSP)
                                Tunnels

Abstract

   This document updates RFC 4090 for the Resource Reservation Protocol
   (RSVP) Traffic Engineering (TE) procedures defined for facility
   backup protection.  The updates include extensions that reduce the
   amount of signaling and processing that occurs during Fast Reroute
   (FRR); as a result, scalability when undergoing FRR convergence after
   a link or node failure is improved.  These extensions allow the RSVP
   message exchange between the Point of Local Repair (PLR) and the
   Merge Point (MP) nodes to be independent of the number of protected
   Label Switched Paths (LSPs) traversing between them when facility
   bypass FRR protection is used.  The signaling extensions are fully
   backwards compatible with nodes that do not support them.

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/rfc8796.

Copyright Notice

   Copyright (c) 2020 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
   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
   2.  Conventions Used in This Document
     2.1.  Terminology
     2.2.  Acronyms and Abbreviations
   3.  Extensions for Summary FRR Signaling
     3.1.  B-SFRR-Ready Extended ASSOCIATION Object
       3.1.1.  IPv4 B-SFRR-Ready Extended Association ID
       3.1.2.  IPv6 B-SFRR-Ready Extended Association ID
       3.1.3.  Processing Rules for B-SFRR-Ready Extended ASSOCIATION
               Object
     3.2.  B-SFRR-Active Extended ASSOCIATION Object
       3.2.1.  IPv4 B-SFRR-Active Extended Association ID
       3.2.2.  IPv6 B-SFRR-Active Extended Association ID
     3.3.  Signaling Procedures prior to Failure
       3.3.1.  PLR Signaling Procedure
       3.3.2.  MP Signaling Procedure
     3.4.  Signaling Procedures Post-Failure
       3.4.1.  PLR Signaling Procedure
       3.4.2.  MP Signaling Procedure
     3.5.  Refreshing Summary FRR Active LSPs
   4.  Backwards Compatibility
   5.  Security Considerations
   6.  IANA Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Acknowledgments
   Contributors
   Authors' Addresses

1.  Introduction

   The Fast Reroute (FRR) procedures defined in [RFC4090] describe the
   mechanisms for the Point of Local Repair (PLR) to reroute traffic and
   signaling of a protected RSVP-TE Label Switched Path (LSP) onto the
   bypass tunnel in the event of a TE link or node failure.  Such
   signaling procedures are performed individually for each affected
   protected LSP.  This may eventually lead to control-plane scalability
   and latency issues on the PLR and/or the Merge Point (MP) nodes due
   to limited memory and CPU processing resources.  This condition is
   exacerbated when the failure affects a large number of protected LSPs
   that traverse the same PLR and MP nodes.

   For example, in a large-scale deployment of RSVP-TE LSPs, a single
   Label Switching Router (LSR) acting as a PLR node may host tens of
   thousands of protected RSVP-TE LSPs egressing the same protected link
   and also act as an MP node for a similar number of LSPs that ingress
   on the same link.  In the event of the failure of the link or
   neighbor node, the RSVP-TE control plane of the node (when acting as
   a PLR node) becomes busy rerouting protected LSPs over the bypass
   tunnel(s) in one direction and (when acting as an MP node) becomes
   busy merging RSVP states from signaling received over bypass tunnels
   for one or more LSPs in the reverse direction.  Subsequently, the
   head-end Label Edge Routers (LERs) that are notified of the local
   repair at any downstream LSRs will attempt to (re)converge the
   affected RSVP-TE LSPs onto newly computed paths -- possibly
   traversing the same previously affected LSR(s).  As a result, the
   RSVP-TE control plane becomes overwhelmed (1) by the amount of FRR
   RSVP-TE processing overhead following the link or node failure and
   (2) due to other control-plane protocols (e.g., IGP) that undergo
   convergence on the same node at the same time.

   Today, each protected RSVP-TE LSP is signaled individually over the
   bypass tunnel after FRR.  The changes introduced in this document
   allow the PLR node to assign multiple protected LSPs to a bypass
   tunnel group and to communicate this assignment to the MP, such that
   upon failure, the signaling over the bypass tunnel happens on one or
   more bypass tunnel groups.  This document defines new extensions that

   1.  update the procedures defined in [RFC4090] for facility backup
       protection, to enable the MP node to become aware of the PLR
       node's bypass tunnel assignment group or groups.

   2.  allow FRR procedures between the PLR and the MP nodes to be
       signaled and processed on one or more per-bypass tunnel groups.

   As defined in [RFC2961], summary refresh procedures use MESSAGE_ID to
   refresh the RSVP Path and Resv states to help with scaling.  The
   Summary FRR procedures introduced in this document build on those
   concepts to allow the MESSAGE_ID(s) to be exchanged on one or more
   per-bypass tunnel assignment groups and continue to use summary
   refresh procedures while reducing the amount of messaging that occurs
   after rerouting signaling over the bypass tunnel post-FRR.

2.  Conventions Used in This Document

2.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "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.

2.2.  Acronyms and Abbreviations

   It is assumed that the reader is familiar with the terms and
   abbreviations used in [RFC3209] and [RFC4090].

   The following abbreviations are also used in this document:

   LSR:  Label Switching Router

   LER:  Label Edge Router

   MPLS:  Multiprotocol Label Switching

   LSP:  Label Switched Path

   MP:  Merge Point node as defined in [RFC4090]

   PLR:  Point of Local Repair node as defined in [RFC4090]

   FRR:  Fast Reroute as defined in [RFC4090]

   B-SFRR-Ready:  Bypass Summary FRR Ready Extended ASSOCIATION object.
      Added by the PLR node for each LSP protected by the bypass tunnel

   B-SFRR-Active:  Bypass Summary FRR Active Extended ASSOCIATION
      object.  Used to notify the MP node that one or more groups of
      protected LSPs have been rerouted over the associated bypass
      tunnel

   MTU:  Maximum Transmission Unit

3.  Extensions for Summary FRR Signaling

   The RSVP ASSOCIATION object is defined in [RFC4872] as a means to
   associate LSPs with each other.  For example, in the context of one
   or more GMPLS-controlled LSPs, the ASSOCIATION object is used to
   associate a recovery LSP with the LSP(s) it is protecting.  The
   Extended ASSOCIATION object is introduced in [RFC6780] to expand on
   the possible usage of the ASSOCIATION object and generalize the
   definition of the Extended Association ID field.

   This document defines the use of the Extended ASSOCIATION object to
   carry the Summary FRR information and associate the protected LSP or
   LSPs with the bypass tunnel that protects them.  Two new Association
   Types for the Extended ASSOCIATION object, and new Extended
   Association IDs, are defined in this document to describe the Bypass
   Summary FRR Ready (B-SFRR-Ready) and Bypass Summary FRR Active
   (B-SFRR-Active) associations.

   The PLR node creates and manages the Summary FRR LSP groups
   (identified by Bypass_Group_Identifiers) and shares the group
   identifiers with the MP via signaling.

   A PLR node SHOULD assign the same Bypass_Group_Identifier to all
   protected LSPs provided that the protected LSPs:

   *  share the same outgoing protected interface,

   *  are protected by the same bypass tunnel, and

   *  are assigned the same tunnel sender address that is used for
      backup path identification after FRR as described in [RFC4090].

   This minimizes the number of bypass tunnel Summary FRR groups and
   optimizes the amount of signaling that occurs between the PLR and the
   MP nodes after FRR.

   A PLR node that supports Summary FRR procedures adds an Extended
   ASSOCIATION object with a B-SFRR-Ready Extended Association ID in the
   RSVP Path message of the protected LSP.  The PLR node adds the
   protected LSP Bypass_Group_Identifier, information from the assigned
   bypass tunnel, and a MESSAGE_ID object into the B-SFRR-Ready Extended
   Association ID.  The MP uses the information contained in the
   received B-SFRR-Ready Extended Association ID to refresh and merge
   the protected LSP Path state after FRR occurs.

   An MP node that supports Summary FRR procedures adds the B-SFRR-Ready
   Extended ASSOCIATION object and respective Extended Association ID in
   the RSVP Resv message of the protected LSP to acknowledge the PLR's
   bypass tunnel assignment and provide the MESSAGE_ID object that the
   MP node will use to refresh the protected LSP Resv state after FRR
   occurs.

   The MP maintains the PLR node group assignments learned from
   signaling and acknowledges the group assignments to the PLR node via
   signaling.  Once the PLR node receives the group assignment
   acknowledgment from the MP, the FRR signaling can proceed based on
   Summary FRR procedures as described in this document.

   The B-SFRR-Active Extended ASSOCIATION object with Extended
   Association ID is sent by the PLR node after activating the Summary
   FRR procedures.  The B-SFRR-Active Extended ASSOCIATION object with
   Extended Association ID is sent within the RSVP Path message of the
   bypass tunnel to inform the MP node that one or more groups of
   protected LSPs protected by the bypass tunnel are now being rerouted
   over the bypass tunnel.

3.1.  B-SFRR-Ready Extended ASSOCIATION Object

   The Extended ASSOCIATION object is populated using the rules defined
   below to associate a protected LSP with the bypass tunnel that is
   protecting it when Summary FRR procedures are enabled.

   The Association Type, Association ID, and Association Source MUST be
   set as defined in [RFC4872] for the ASSOCIATION object.  More
   specifically:

   Association Source:
      The Association Source is set to an address of the PLR node.

   Association Type:
      A new Association Type is defined for B-SFRR-Ready as follows:

      +=======+=====================================================+
      | Value | Type                                                |
      +=======+=====================================================+
      | 5     | Bypass Summary FRR Ready Association (B-SFRR-Ready) |
      +-------+-----------------------------------------------------+

                 Table 1: The B-SFRR-Ready Association Type

   The Extended ASSOCIATION object's Global Association Source MUST be
   set according to the rules defined in [RFC6780].

   The B-SFRR-Ready Extended Association ID is populated by the PLR node
   when performing Bypass Summary FRR Ready association for a protected
   LSP.  The rules governing its population are described in the
   subsequent sections.

3.1.1.  IPv4 B-SFRR-Ready Extended Association ID

   The IPv4 Extended Association ID for the B-SFRR-Ready Association
   Type is carried inside the IPv4 Extended ASSOCIATION object and 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Bypass_Tunnel_ID      |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Bypass_Source_IPv4_Address                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Bypass_Destination_IPv4_Address                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Bypass_Group_Identifier                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                MESSAGE_ID                                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 1: The IPv4 Extended Association ID for B-SFRR-Ready

   Bypass_Tunnel_ID:  16 bits

      The bypass tunnel identifier.

   Reserved:  16 bits

      Reserved for future use.  MUST be set to zero when sending and
      ignored on receipt.

   Bypass_Source_IPv4_Address:  32 bits

      The bypass tunnel source IPv4 address.

   Bypass_Destination_IPv4_Address:  32 bits

      The bypass tunnel destination IPv4 address.

   Bypass_Group_Identifier:  32 bits

      The bypass tunnel group identifier that is assigned to the LSP.

   MESSAGE_ID:  A MESSAGE_ID object as defined by [RFC2961].

3.1.2.  IPv6 B-SFRR-Ready Extended Association ID

   The IPv6 Extended Association ID for the B-SFRR-Ready Association
   Type is carried inside the IPv6 Extended ASSOCIATION object and 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Bypass_Tunnel_ID      |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                Bypass_Source_IPv6_Address                     +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                Bypass_Destination_IPv6_Address                +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Bypass_Group_Identifier                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                MESSAGE_ID                                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 2: The IPv6 Extended Association ID for B-SFRR-Ready

   Bypass_Tunnel_ID:  16 bits

      The bypass tunnel identifier.

   Reserved:  16 bits

      Reserved for future use.  MUST be set to zero when sending and
      ignored on receipt.

   Bypass_Source_IPv6_Address:  128 bits

      The bypass tunnel source IPv6 address.

   Bypass_Destination_IPv6_Address:  128 bits

      The bypass tunnel destination IPv6 address.

   Bypass_Group_Identifier:  32 bits

      The bypass tunnel group identifier that is assigned to the LSP.

   MESSAGE_ID:  A MESSAGE_ID object as defined by [RFC2961].

3.1.3.  Processing Rules for B-SFRR-Ready Extended ASSOCIATION Object

   A PLR node assigns a bypass tunnel and Bypass_Group_Identifier for
   each protected LSP.  The same Bypass_Group_Identifier is used for the
   set of protected LSPs that share the same bypass tunnel, traverse the
   same egress link, and are not already rerouted.  The PLR node MUST
   generate a MESSAGE_ID object with Epoch and Message_Identifier set
   according to [RFC2961].  The MESSAGE_ID object Flags MUST be cleared
   when transmitted by the PLR node and ignored when received at the MP
   node.

   A PLR node MUST generate a new Message_Identifier each time the
   contents of the B-SFRR-Ready Extended Association ID change (e.g.,
   when the PLR node changes the bypass tunnel assignment).

   A PLR node notifies the MP node of the bypass tunnel assignment via
   adding a B-SFRR-Ready Extended ASSOCIATION object and Extended
   Association ID in the RSVP Path message for the protected LSP, using
   the procedures described in Section 3.3.

   An MP node acknowledges the assignment to the PLR node by signaling
   the B-SFRR-Ready Extended ASSOCIATION object and Extended Association
   ID within the RSVP Resv message of the protected LSP.  With the
   exception of the MESSAGE_ID object, all other fields from the
   received B-SFRR-Ready Extended Association ID in the RSVP Path
   message are copied into the B-SFRR-Ready Extended Association ID to
   be added in the Resv message.  The MESSAGE_ID object is set according
   to [RFC2961].  The MESSAGE_ID object Flags MUST be cleared when
   transmitted by the MP node and ignored when received at the PLR node.
   A new Message_Identifier MUST be used to acknowledge an updated PLR
   node's assignment.

   A PLR node considers the protected LSP as Summary FRR capable only if
   all the fields in the B-SFRR-Ready Extended Association ID that are
   sent in the RSVP Path message match the fields received in the RSVP
   Resv message (with the exception of the MESSAGE_ID).  If the fields
   do not match or if the B-SFRR-Ready Extended ASSOCIATION object is
   absent in a subsequent refresh, the PLR node MUST consider the
   protected LSP as not Summary FRR capable.

   A race condition may arise for a previously Summary FRR-capable
   protected LSP when the MP node triggers a refresh that does not
   contain the B-SFRR-Ready Extended ASSOCIATION object, while at the
   same time the PLR triggers Summary FRR procedures due to a fault
   occurring concurrently.  In this case, it is possible that the PLR
   triggers Summary FRR procedures on the protected LSP before it can
   receive and process the refresh from the MP node.  As a result, the
   MP will receive an Srefresh with a Message_Identifier that is not
   associated with any state.  As per [RFC2961], this results in the MP
   generating an Srefresh NACK for this Message_Identifier and sending
   it back to the PLR.  The PLR processes the Srefresh NACK, replays the
   full Path state associated with the Message_Identifier, and
   subsequently recovers from this condition.

3.2.  B-SFRR-Active Extended ASSOCIATION Object

   The Extended ASSOCIATION object for the B-SFRR-Active Association
   Type is populated by a PLR node to indicate to the MP node (the
   bypass tunnel destination) that one or more groups of Summary
   FRR-capable protected LSPs that are being protected by the bypass
   tunnel are being rerouted over the bypass tunnel.

   The B-SFRR-Active Extended ASSOCIATION object is carried in the RSVP
   Path message of the bypass tunnel and signaled downstream towards the
   MP (the bypass tunnel destination).

   The Association Type, Association ID, and Association Source MUST be
   set as defined in [RFC4872] for the ASSOCIATION object.  More
   specifically:

   Association Source:
      The Association Source is set to an address of the PLR node.

   Association Type:
      A new Association Type is defined for B-SFRR-Active as follows:

     +=======+=======================================================+
     | Value | Type                                                  |
     +=======+=======================================================+
     | 6     | Bypass Summary FRR Active Association (B-SFRR-Active) |
     +-------+-------------------------------------------------------+

                Table 2: The B-SFRR-Active Association Type

   Extended Association ID for B-SFRR-Active:
      The B-SFRR-Active Extended Association ID is populated by the PLR
      node for the Bypass Summary FRR Active association.  The rules to
      populate the Extended Association ID in this case are described
      below.

3.2.1.  IPv4 B-SFRR-Active Extended Association ID

   The IPv4 Extended Association ID for the B-SFRR-Active Association
   Type is carried inside the IPv4 Extended ASSOCIATION object and 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Num-BGIDs          |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Bypass_Group_Identifier                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               :                               |
      //                              :                              //
      |                               :                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Bypass_Group_Identifier                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                      RSVP_HOP_Object                        //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                      TIME_VALUES                            //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       IPv4 tunnel sender address              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 3: The IPv4 Extended Association ID for B-SFRR-Active

   Num-BGIDs:  16 bits

      Number of Bypass_Group_Identifier fields.

   Reserved:  16 bits

      Reserved for future use.

   Bypass_Group_Identifier:  32 bits each

      A Bypass_Group_Identifier that was previously signaled by the PLR
      using the Extended ASSOCIATION object in the B-SFRR-Ready Extended
      Association ID.  One or more Bypass_Group_Identifiers MAY be
      included.

   RSVP_HOP_Object:  Class 3, as defined by [RFC2205]

      Replacement RSVP_HOP object to be applied to all LSPs associated
      with each of the following Bypass_Group_Identifiers.  This
      corresponds to C-Type = 1 for IPv4 RSVP_HOP.

   TIME_VALUES object:  Class 5, as defined by [RFC2205]

      Replacement TIME_VALUES object to be applied to all LSPs
      associated with each of the preceding Bypass_Group_Identifiers
      after receiving the B-SFRR-Active Extended ASSOCIATION object.

   IPv4 tunnel sender address:
      The IPv4 address that the PLR node sets to identify one or more
      backup paths as described in Section 6.1.1 of [RFC4090].  This
      address is applicable to all groups identified by any
      Bypass_Group_Identifiers carried in the B-SFRR-Active Extended
      Association ID.

3.2.2.  IPv6 B-SFRR-Active Extended Association ID

   The IPv6 Extended Association ID for the B-SFRR-Active Association
   Type is carried inside the IPv6 Extended ASSOCIATION object and 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Num-BGIDs          |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Bypass_Group_Identifier                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                               :                               |
      //                              :                              //
      |                               :                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Bypass_Group_Identifier                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                      RSVP_HOP_Object                        //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      //                      TIME_VALUES                            //
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                                                               |
      +                       IPv6 tunnel sender address              +
      |                                                               |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 4: The IPv6 Extended Association ID for B-SFRR-Active

   Num-BGIDs:  16 bits

      Number of Bypass_Group_Identifier fields.

   Reserved:  16 bits

      Reserved for future use.

   Bypass_Group_Identifier:  32 bits each

      A Bypass_Group_Identifier that was previously signaled by the PLR
      using the Extended ASSOCIATION object in the B-SFRR-Ready Extended
      Association ID.  One or more Bypass_Group_Identifiers MAY be
      included.

   RSVP_HOP_Object:  Class 3, as defined by [RFC2205]

      Replacement RSVP_HOP object to be applied to all LSPs associated
      with each of the following Bypass_Group_Identifiers.  This
      corresponds to C-Type = 2 for IPv6 RSVP_HOP.

   TIME_VALUES object:  Class 5, as defined by [RFC2205]

      Replacement TIME_VALUES object to be applied to all LSPs
      associated with each of the following Bypass_Group_Identifiers
      after receiving the B-SFRR-Active Extended ASSOCIATION object.

   IPv6 tunnel sender address:
      The IPv6 address that the PLR node sets to identify one or more
      backup paths as described in Section 6.1.1 of [RFC4090].  This
      address is applicable to all groups identified by any
      Bypass_Group_Identifiers carried in the B-SFRR-Active Extended
      Association ID.

3.3.  Signaling Procedures prior to Failure

   Before Summary FRR procedures can be used, a handshake MUST be
   completed between the PLR and MP nodes.  This handshake is performed
   using the Extended ASSOCIATION object that carries the B-SFRR-Ready
   Extended Association ID in both the RSVP Path and Resv messages of
   the protected LSP.

   The facility backup method introduced in [RFC4090] takes advantage of
   MPLS label stacking (the PLR node imposes additional MPLS labels
   post-FRR) to allow rerouting of protected traffic over the backup
   path.  The backup path may have stricter MTU requirements; due to
   label stacking at the PLR node, the protected traffic may exceed the
   backup path MTU.  It is assumed that the operator engineers their
   network to allow rerouting of protected traffic and the additional
   label stacking at the PLR node in order to not exceed the backup path
   MTU.

   When using the procedures defined in this document, the PLR node MUST
   ensure that the bypass tunnel assignment can satisfy the protected
   LSP MTU requirements post-FRR.  This prevents any packets from being
   dropped due to exceeding the MTU size of the backup path after
   traffic is rerouted onto the bypass tunnel post-failure.  Section 2.6
   of [RFC3209] describes a mechanism to determine whether a node needs
   to fragment or drop a packet when it exceeds the path MTU discovered
   using RSVP signaling on the primary LSP path.  A PLR can leverage the
   RSVP-discovered path MTU on the backup and primary LSP paths to
   ensure that the MTU is not exceeded before or after rerouting the
   protected traffic onto the bypass tunnel.

3.3.1.  PLR Signaling Procedure

   The B-SFRR-Ready Extended ASSOCIATION object is added by each PLR
   node in the RSVP Path message of the protected LSP to record the
   bypass tunnel assignment.  This object is updated every time the PLR
   node updates the bypass tunnel assignment.  This results in
   triggering an RSVP Path change message.

   Upon receiving an RSVP Resv message with a B-SFRR-Ready Extended
   ASSOCIATION object, the PLR node checks to see if the expected
   subobjects from the B-SFRR-Ready Extended Association ID are present.
   If present, the PLR node determines if the MP has acknowledged the
   current PLR node's assignment.

   To be a valid acknowledgment, the received B-SFRR-Ready Extended
   Association ID contents within the RSVP Resv message of the protected
   LSP MUST match the latest B-SFRR-Ready Extended ASSOCIATION object
   and Association ID contents that the PLR node had sent within the
   RSVP Path message (with the exception of the MESSAGE_ID).

   Note that when forwarding an RSVP Resv message upstream, the PLR node
   SHOULD remove any/all B-SFRR-Ready Extended ASSOCIATION objects whose
   Bypass_Source_IPv4_Address or Bypass_Source_IPv6_Address field
   matches any of the PLR node addresses.

3.3.2.  MP Signaling Procedure

   Upon receiving an RSVP Path message with a B-SFRR-Ready Extended
   ASSOCIATION object, an MP node processes all (there may be multiple
   PLR nodes for a single MP node) B-SFRR-Ready Extended ASSOCIATION
   objects that have the MP node address as the bypass destination
   address in the Extended Association ID.

   The MP node first ensures the existence of the bypass tunnel and that
   the Bypass_Group_Identifier is not already FRR Active.  That is, an
   LSP cannot join a group that is already FRR rerouted.

   The MP node builds a mirrored Summary FRR group database per PLR node
   by associating the Bypass_Source_IPv4_Address or
   Bypass_Source_IPv6_Address that is carried in the IPv4 or IPv6
   B-SFRR-Ready Extended Association IDs, respectively.

   The MESSAGE_ID is extracted and recorded for the protected LSP Path
   state.  The MP node signals a B-SFRR-Ready Extended ASSOCIATION
   object and Extended Association ID in the RSVP Resv message of the
   protected LSP.  With the exception of the MESSAGE_ID objects, all
   other fields of the received B-SFRR-Ready Extended ASSOCIATION object
   in the RSVP Path message are copied into the B-SFRR-Ready Extended
   ASSOCIATION object to be added in the Resv message.  The MESSAGE_ID
   object is set according to [RFC2961] with the Flags cleared.

   Note that an MP may receive more than one RSVP Path message with the
   B-SFRR-Ready Extended ASSOCIATION object from one or more different
   upstream PLR nodes.  In this case, the MP node is expected to save
   all the received MESSAGE_IDs received from the different upstream PLR
   nodes.  After a failure, the MP node determines and activates the
   state(s) associated with the Bypass_Group_Identifier(s) received in
   the RSVP Path message containing the B-SFRR-Active Extended
   ASSOCIATION object that is signaled over the bypass tunnel from the
   PLR node, as described in Section 3.4.

   When forwarding an RSVP Path message downstream, the MP node SHOULD
   remove any/all B-SFRR-Ready Extended ASSOCIATION objects whose
   Bypass_Destination_IPv4_Address or Bypass_Destination_IPv6_Address
   field matches any of the MP node addresses.

3.4.  Signaling Procedures Post-Failure

   Upon detection of a fault (egress link or node failure), the PLR node
   will first perform the object modification procedures described by
   Section 6.4.3 of [RFC4090] for all affected protected LSPs.  For the
   Summary FRR-capable LSPs that are assigned to the same bypass tunnel,
   a common RSVP_HOP and SENDER_TEMPLATE MUST be used.

   The PLR node MUST signal non-Summary FRR-capable LSPs over the bypass
   tunnel before signaling the Summary FRR-capable LSPs.  This is needed
   to allow for the case where the PLR node recently changed a bypass
   assignment and the MP has not processed the change yet.

   The B-SFRR-Active Extended ASSOCIATION object is sent within the RSVP
   Path message of the bypass tunnel to reroute the RSVP state of
   Summary FRR-capable LSPs.

3.4.1.  PLR Signaling Procedure

   After a failure event, when using the Summary FRR path signaling
   procedures, an individual RSVP Path message is not signaled for each
   Summary FRR LSP.  Instead, to reroute Summary FRR LSPs via the bypass
   tunnel, the PLR node adds the B-SFRR-Active Extended ASSOCIATION
   object in the RSVP Path message of the RSVP session of the bypass
   tunnel.

   The RSVP_HOP_Object field in the B-SFRR-Active Extended Association
   ID is set to a common object that will be applied to all LSPs
   associated with the Bypass_Group_Identifiers that are carried in the
   B-SFRR-Active Extended Association ID.

   The PLR node adds the Bypass_Group_Identifier(s) of any group or
   groups that have common group attributes, including the tunnel sender
   address, to the same B-SFRR-Active Extended Association ID.  Note
   that multiple ASSOCIATION objects, each carrying a B-SFRR-Active
   Extended Association ID, can be carried within a single RSVP Path
   message of the bypass tunnel and sent towards the MP as described in
   [RFC6780].

   Any previously received MESSAGE_IDs from the MP are activated on the
   PLR.  As a result, the PLR starts sending Srefresh messages
   containing the specific Message_Identifier(s) for the states to be
   refreshed.

3.4.2.  MP Signaling Procedure

   Upon receiving an RSVP Path message with a B-SFRR-Active Extended
   ASSOCIATION object, the MP performs normal merge point processing for
   each protected LSP associated with each Bypass_Group_Identifier, as
   if it had received an individual RSVP Path message for that LSP.

   For each Summary FRR-capable LSP that is being merged, the MP first
   modifies the Path state as follows:

   1.  The RSVP_HOP object is copied from the RSVP_HOP_Object field in
       the B-SFRR-Active Extended Association ID.

   2.  The TIME_VALUES object is copied from the TIME_VALUES field in
       the B-SFRR-Active Extended Association ID.  The TIME_VALUES
       object contains the refresh period of the PLR node, and it is
       used to generate periodic refreshes.  The TIME_VALUES object
       carried in the B-SFRR-Active Extended Association ID matches the
       one that would have been exchanged in a full Path message sent to
       the MP after the failure when no Summary FRR procedures are used.

   3.  The tunnel sender address field in the SENDER_TEMPLATE object is
       copied from the tunnel sender address field of the B-SFRR-Active
       Extended Association ID.

   4.  The Explicit Route Object (ERO) is modified as per Section 6.4.4
       of [RFC4090].  Once the above modifications are completed, the MP
       node performs merge processing as per [RFC4090].

   5.  Any previously received MESSAGE_IDs from the PLR node are
       activated.  The MP is allowed to send Srefresh messages
       containing the specific Message_Identifier(s) for the states to
       be refreshed.

   A failure during merge processing of any individual rerouted LSP MUST
   result in an RSVP PathErr message.

   An individual RSVP Resv message for each successfully merged Summary
   FRR LSP is not signaled.  The MP node SHOULD immediately use summary
   refresh procedures to refresh the protected LSP Resv state.

3.5.  Refreshing Summary FRR Active LSPs

   The refreshing of Summary FRR Active LSPs is performed using summary
   refresh as defined by [RFC2961].

4.  Backwards Compatibility

   The (Extended) ASSOCIATION object is defined in [RFC4872] with a
   class number in the form 11bbbbbb, where b=0 or 1.  This ensures
   compatibility with nodes that do not provide support, in accordance
   with the procedures specified in Section 3.10 of [RFC2205] regarding
   unknown-class objects.  Such nodes will ignore the object and forward
   it without any modification.

5.  Security Considerations

   This document updates an existing RSVP object -- the Extended
   ASSOCIATION object as described in Section 3.  Thus, in the event of
   the interception of a signaling message, slightly more information
   could be deduced about the state of the network than was previously
   the case.

   When using the procedures defined in this document, FRR signaling for
   rerouting of the states of one or more protected LSPs onto the bypass
   tunnel can be performed on a group of protected LSPs with a single
   RSVP message.  This allows an intruder to potentially impact and
   manipulate a set of protected LSPs that are assigned to the same
   bypass tunnel group.  Note that such an attack is possible even
   without the mechanisms defined in this document, albeit at an extra
   cost resulting from the excessive per-LSP signaling that will occur.

   Existing mechanisms for maintaining the integrity and authenticity of
   RSVP messages [RFC2747] can be applied.  Other considerations
   mentioned in [RFC4090] and [RFC5920] also apply.

6.  IANA Considerations

   IANA maintains the "Generalized Multi-Protocol Label Switching
   (GMPLS) Signaling Parameters" registry.  The "Association Type"
   subregistry is included in this registry.

   This registry has been updated with the new Association Types for the
   Extended ASSOCIATION objects defined in this document as follows:

            +=======+===========================+=============+
            | Value | Name                      | Reference   |
            +=======+===========================+=============+
            | 5     | B-SFRR-Ready Association  | Section 3.1 |
            +-------+---------------------------+-------------+
            | 6     | B-SFRR-Active Association | Section 3.2 |
            +-------+---------------------------+-------------+

                  Table 3: New Extended ASSOCIATION Object
                             Association Types

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>.

   [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
              September 1997, <https://www.rfc-editor.org/info/rfc2205>.

   [RFC2747]  Baker, F., Lindell, B., and M. Talwar, "RSVP Cryptographic
              Authentication", RFC 2747, DOI 10.17487/RFC2747, January
              2000, <https://www.rfc-editor.org/info/rfc2747>.

   [RFC2961]  Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
              and S. Molendini, "RSVP Refresh Overhead Reduction
              Extensions", RFC 2961, DOI 10.17487/RFC2961, April 2001,
              <https://www.rfc-editor.org/info/rfc2961>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC4090]  Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
              Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
              DOI 10.17487/RFC4090, May 2005,
              <https://www.rfc-editor.org/info/rfc4090>.

   [RFC4872]  Lang, J.P., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
              Ed., "RSVP-TE Extensions in Support of End-to-End
              Generalized Multi-Protocol Label Switching (GMPLS)
              Recovery", RFC 4872, DOI 10.17487/RFC4872, May 2007,
              <https://www.rfc-editor.org/info/rfc4872>.

   [RFC6780]  Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP
              ASSOCIATION Object Extensions", RFC 6780,
              DOI 10.17487/RFC6780, October 2012,
              <https://www.rfc-editor.org/info/rfc6780>.

   [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

   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
              <https://www.rfc-editor.org/info/rfc5920>.

Acknowledgments

   The authors would like to thank Alexander Okonnikov, Loa Andersson,
   Lou Berger, Eric Osborne, Gregory Mirsky, and Mach Chen for reviewing
   and providing valuable comments on this document.

Contributors

   Nicholas Tan
   Arista Networks

   Email: ntan@arista.com


Authors' Addresses

   Mike Taillon
   Cisco Systems, Inc.

   Email: mtaillon@cisco.com


   Tarek Saad (editor)
   Juniper Networks

   Email: tsaad@juniper.net


   Rakesh Gandhi
   Cisco Systems, Inc.

   Email: rgandhi@cisco.com


   Abhishek Deshmukh
   Juniper Networks

   Email: adeshmukh@juniper.net


   Markus Jork
   128 Technology

   Email: mjork@128technology.com


   Vishnu Pavan Beeram
   Juniper Networks

   Email: vbeeram@juniper.net


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