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RFC 4872 - RSVP-TE Extensions in Support of End-to-End Generaliz


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Network Working Group                                     J.P. Lang, Ed.
Request for Comments: 4872                                         Sonos
Updates: 3471                                            Y. Rekhter, Ed.
Category: Standards Track                                        Juniper
                                                   D. Papadimitriou, Ed.
                                                                 Alcatel
                                                                May 2007

              RSVP-TE Extensions in Support of End-to-End
      Generalized Multi-Protocol Label Switching (GMPLS) Recovery

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document describes protocol-specific procedures and extensions
   for Generalized Multi-Protocol Label Switching (GMPLS) Resource
   ReSerVation Protocol - Traffic Engineering (RSVP-TE) signaling to
   support end-to-end Label Switched Path (LSP) recovery that denotes
   protection and restoration.  A generic functional description of
   GMPLS recovery can be found in a companion document, RFC 4426.

Table of Contents

  1. Introduction .....................................................3
   2. Conventions Used in This Document ...............................5
   3. Relationship to Fast Reroute (FRR) ..............................5
   4. Definitions .....................................................6
      4.1. LSP Identification .........................................6
      4.2. Recovery Attributes ........................................7
           4.2.1. LSP Status ..........................................7
           4.2.2. LSP Recovery ........................................8
      4.3. LSP Association ............................................9
   5. 1+1 Unidirectional Protection ...................................9
      5.1. Identifiers ...............................................10

   6. 1+1 Bidirectional Protection ...................................10
      6.1. Identifiers ...............................................11
      6.2. End-to-End Switchover Request/Response ....................11
   7. 1:1 Protection with Extra-Traffic ..............................13
      7.1. Identifiers ...............................................14
      7.2. End-to-End Switchover Request/Response ....................15
      7.3. 1:N (N > 1) Protection with Extra-Traffic .................16
   8. Rerouting without Extra-Traffic ................................17
      8.1. Identifiers ...............................................19
      8.2. Signaling Primary LSPs ....................................19
      8.3. Signaling Secondary LSPs ..................................19
   9. Shared-Mesh Restoration ........................................20
      9.1. Identifiers ...............................................22
      9.2. Signaling Primary LSPs ....................................22
      9.3. Signaling Secondary LSPs ..................................23
   10. LSP Preemption ................................................23
   11. (Full) LSP Rerouting ..........................................25
      11.1. Identifiers ..............................................25
      11.2. Signaling Reroutable LSPs ................................26
   12. Reversion .....................................................26
   13. Recovery Commands .............................................29
   14. PROTECTION Object .............................................31
      14.1. Format ...................................................31
      14.2. Processing ...............................................33
   15. PRIMARY_PATH_ROUTE Object .....................................33
      15.1. Format ...................................................34
      15.2. Subobjects ...............................................34
      15.3. Applicability ............................................35
      15.4. Processing ...............................................36
   16. ASSOCIATION Object ............................................37
      16.1. Format ...................................................37
      16.2. Processing ...............................................38
   17. Updated RSVP Message Formats ..................................39
   18. Security Considerations .......................................40
   19. IANA Considerations ...........................................41
   20. Acknowledgments ...............................................43
   21. References ....................................................43
      21.1. Normative References .....................................43
      21.2. Informative References ...................................44
   22. Contributors ..................................................45

1.  Introduction

   Generalized Multi-Protocol Label Switching (GMPLS) extends MPLS to
   include support for Layer-2 Switch Capable (L2SC), Time-Division
   Multiplex (TDM), Lambda Switch Capable (LSC), and Fiber Switch
   Capable (FSC) interfaces.  GMPLS recovery uses control plane
   mechanisms (i.e., signaling, routing, and link management mechanisms)
   to support data plane fault recovery.  Note that the analogous (data
   plane) fault detection mechanisms are required to be present in
   support of the control plane mechanisms.  In this document, the term
   "recovery" is generically used to denote both protection and
   restoration; the specific terms "protection" and "restoration" are
   only used when differentiation is required.  The subtle distinction
   between protection and restoration is made based on the resource
   allocation done during the recovery phase (see [RFC4427]).

   A functional description of GMPLS recovery is provided in [RFC4426]
   and should be considered as a companion document.  The present
   document describes the protocol-specific procedures for GMPLS RSVP-
   TE (Resource ReSerVation Protocol - Traffic Engineering) signaling
   (see [RFC3473]) to support end-to-end recovery.  End-to-end recovery
   refers to the recovery of an entire LSP from its head-end (ingress
   node endpoint) to its tail-end (egress node endpoint).  With end-to-
   end recovery, working LSPs are assumed to be resource-disjoint (where
   a resource is a link, node, or Shared Risk Link Group (SRLG)) in the
   network so that they do not share any failure probability, but this
   is not mandatory.  With respect to a given set of network resources,
   a pair of working/protecting LSPs SHOULD be resource disjoint in case
   of dedicated recovery type (see below).  On the other hand, in case
   of shared recovery (see below), a group of working LSPs SHOULD be
   mutually resource-disjoint in order to allow for a (single and
   commonly) shared protecting LSP, itself resource-disjoint from each
   of the working LSPs.  Note that resource disjointness is a necessary
   (but not sufficient) condition to ensure LSP recoverability.

   The present document addresses four types of end-to-end LSP recovery:
   1) 1+1 (unidirectional/bidirectional) protection, 2) 1:N (N >= 1) LSP
   protection with extra-traffic, 3) pre-planned LSP rerouting without
   extra-traffic (including shared mesh), and 4) full LSP rerouting.

   1) The simplest notion of end-to-end LSP protection is 1+1
      unidirectional protection.  Using this type of protection, a
      protecting LSP is signaled over a dedicated resource-disjoint
      alternate path to protect an associated working LSP.  Normal
      traffic is simultaneously sent on both LSPs and a selector is used
      at the egress node to receive traffic from one of the LSPs.  If a
      failure occurs along one of the LSPs, the egress node selects the

      traffic from the valid LSP.  No coordination is required between
      the end nodes when a failure/switchover occurs.

      In 1+1 bidirectional protection, a protecting LSP is signaled over
      a dedicated resource-disjoint alternate path to protect the
      working LSP.  Normal traffic is simultaneously sent on both LSPs
      (in both directions), and a selector is used at both
      ingress/egress nodes to receive traffic from the same LSP.  This
      requires coordination between the end-nodes when switching to the
      protecting LSP.

   2) In 1:N (N >= 1) protection with extra-traffic, the protecting LSP
      is a fully provisioned and resource-disjoint LSP from the N
      working LSPs, that allows for carrying extra-traffic.  The N
      working LSPs MAY be mutually resource-disjoint.  Coordination
      between end-nodes is required when switching from one of the
      working LSPs to the protecting LSP.  As the protecting LSP is
      fully provisioned, default operations during protection switching
      are specified for a protecting LSP carrying extra-traffic, but
      this is not mandatory.  Note that M:N protection is out of scope
      of this document (though mechanisms it defines may be extended to
      cover it).

   3) Pre-planned LSP rerouting (or restoration) relies on the
      establishment between the same pair of end-nodes of a working LSP
      and a protecting LSP that is link/node/SRLG disjoint from the
      working one.  Here, the recovery resources for the protecting LSP
      are pre-reserved but explicit action is required to activate
      (i.e., commit resource allocation at the data plane) a specific
      protecting LSP instantiated during the (pre-)provisioning phase.
      Since the protecting LSP is not "active" (i.e., fully
      instantiated), it cannot carry any extra-traffic.  This does not
      mean that the corresponding resources cannot be used by other
      LSPs.  Therefore, this mechanism protects against working LSP(s)
      failure(s) but requires activation of the protecting LSP after
      working LSP failure occurrence.  This requires restoration
      signaling along the protecting path.  "Shared-mesh" restoration
      can be seen as a particular case of pre-planned LSP rerouting that
      reduces the recovery resource requirements by allowing multiple
      protecting LSPs to share common link and node resources.  The
      recovery resources are pre-reserved but explicit action is
      required to activate (i.e., commit resource allocation at the data
      plane) a specific protecting LSP instantiated during the (pre-)
      provisioning phase.  This procedure requires restoration signaling
      along the protecting path.

      Note that in both cases, bandwidth pre-reserved for a protecting
      (but not activated) LSP can be made available for carrying extra
      traffic.  LSPs for extra-traffic (with lower holding priority than
      the protecting LSP) can then be established using the bandwidth
      pre-reserved for the protecting LSP.  Also, any lower priority LSP
      that use the pre-reserved resources for the protecting LSP(s) must
      be preempted during the activation of the protecting LSP.

   4) Full LSP rerouting (or restoration) switches normal traffic to an
      alternate LSP that is not even partially established until after
      the working LSP failure occurs.  The new alternate route is
      selected at the LSP head-end node, it may reuse resources of the
      failed LSP at intermediate nodes and may include additional
      intermediate nodes and/or links.

   Crankback signaling (see [CRANK]) and LSP segment recovery (see
   [RFC4873]) are further detailed in dedicated companion documents.

2.  Conventions Used in This Document

   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 [RFC2119].

   In addition, the reader is assumed to be familiar with the
   terminology used in [RFC3945], [RFC3471], [RFC3473] and referenced as
   well as in [RFC4427] and [RFC4426].

3.  Relationship to Fast Reroute (FRR)

   There is no impact to RSVP-TE Fast Reroute (FRR) [RFC4090] introduced
   by end-to-end GMPLS recovery i.e., it is possible to use either
   method defined in FRR with end-to-end GMPLS recovery.

   The objects used and/or newly introduced by end-to-end recovery will
   be ignored by [RFC4090] conformant implementations, and FRR can
   operate on a per LSP basis as defined in [RFC4090].

4.  Definitions

4.1.  LSP Identification

   This section reviews terms previously defined in [RFC2205],
   [RFC3209], and [RFC3473].  LSP tunnels are identified by a
   combination of the SESSION and SENDER_TEMPLATE objects (see also
   [RFC3209]).  The relevant fields are as follows:

   IPv4 (or IPv6) tunnel endpoint address

        IPv4 (or IPv6) address of the egress node for the tunnel.

   Tunnel ID

        A 16-bit identifier used in the SESSION that remains constant
        over the life of the tunnel.

   Extended Tunnel ID

        A 32-bit (or 16-byte) identifier used in the SESSION that
        remains constant over the life of the tunnel.  Normally set to
        all zeros.  Ingress nodes that wish to narrow the scope of a
        SESSION to the ingress-egress pair MAY place their IPv4 (or
        IPv6) address here as a globally unique identifier.

   IPv4 (or IPv6) tunnel sender address

        IPv4 (or IPv6) address for a sender node.

   LSP ID

        A 16-bit identifier used in the SENDER_TEMPLATE and FILTER_SPEC
        that can be changed to allow a sender to share resources with
        itself.

   The first three fields are carried in the SESSION object (Path and
   Resv message) and constitute the basic identification of the LSP
   tunnel.

   The last two fields are carried in the SENDER_TEMPLATE (Path message)
   and FILTER_SPEC objects (Resv message).  The LSP ID is used to
   differentiate LSPs that belong to the same LSP Tunnel (as identified
   by its Tunnel ID).

4.2.  Recovery Attributes

   The recovery attributes include all the parameters that determine the
   status of an LSP within the recovery scheme to which it is
   associated.  These attributes are part of the PROTECTION object
   introduced in Section 14.

4.2.1.  LSP Status

   The following bits are used in determining resource allocation and
   status of the LSP within the group of LSPs forming the protected
   entity:

   - S (Secondary) bit: enables distinction between primary and
     secondary LSPs.  A primary LSP is a fully established LSP for which
     the resource allocation has been committed at the data plane (i.e.,
     full cross-connection has been performed).  Both working and
     protecting LSPs can be primary LSPs.  A secondary LSP is an LSP
     that has been provisioned in the control plane only, and for which
     resource selection MAY have been done but for which the resource
     allocation has not been committed at the data plane (for instance,
     no cross-connection has been performed).  Therefore, a secondary
     LSP is not immediately available to carry any traffic (thus
     requiring additional signaling to be available).  A secondary LSP
     can only be a protecting LSP.  The (data plane) resources allocated
     for a secondary LSP MAY be used by other LSPs until the primary LSP
     fails over to the secondary LSP.

   - P (Protecting) bit: enables distinction between working and
     protecting LSPs.  A working LSP must be a primary LSP whilst a
     protecting LSP can be either a primary or a secondary LSP.  When
     protecting LSP(s) are associated with working LSP(s), one also
     refers to the latter as protected LSPs.

   Note: The combination "secondary working" is not valid (only
   protecting LSPs can be secondary LSPs).  Working LSPs are always
   primary LSPs (i.e., fully established) whilst primary LSPs can be
   either working or protecting LSPs.

   - O (Operational) bit: this bit is set when a protecting LSP is
     carrying the normal traffic after protection switching (i.e.,
     applies only in case of dedicated LSP protection or LSP protection
     with extra-traffic; see Section 4.2.2).

   In this document, the PROTECTION object uses as a basis the
   PROTECTION object defined in [RFC3471] and [RFC3473] and defines
   additional fields within it.  The fields defined in [RFC3471] and
   [RFC3473] are unchanged by this document.

4.2.2.  LSP Recovery

   The following classification is used to distinguish the LSP
   Protection Type with which LSPs can be associated at end-nodes (a
   distinct value is associated with each Protection Type in the
   PROTECTION object; see Section 14):

   - Full LSP Rerouting: set if a primary working LSP is dynamically
     recoverable using (non pre-planned) head-end rerouting.

   - Pre-planned LSP Rerouting without Extra-traffic: set if a
     protecting LSP is a secondary LSP that allows sharing of the pre-
     reserved recovery resources between one or more than one
     <sender;receiver> pair.  When the secondary LSPs resources are not
     pre-reserved for a single <sender;receiver> pair, this type is
     referred to as "shared mesh" recovery.

   - LSP Protection with Extra-traffic: set if a protecting LSP is a
     dedicated primary LSP that allows for extra-traffic transport and
     thus precludes any sharing of the recovery resources between more
     than one <sender;receiver> pair.  This type includes 1:N LSP
     protection with extra-traffic.

   - Dedicated LSP Protection: set if a protecting LSP does not allow
     sharing of the recovery resources nor the transport of extra-
     traffic (implying in the present context, duplication of the signal
     over both working and protecting LSPs as in 1+1 dedicated
     protection).  Note also that this document makes a distinction
     between 1+1 unidirectional and bidirectional dedicated LSP
     protection.

   For LSP protection, in particular, when the data plane provides
   automated protection-switching capability (see for instance ITU-T
   [G.841] Recommendation), a Notification (N) bit is defined in the
   PROTECTION object.  It allows for distinction between protection
   switching signaling via the control plane or the data plane.

   Note: this document assumes that Protection Type values have end-to-
   end significance and that the same value is sent over the protected
   and the protecting path.  In this context, shared-mesh (for instance)
   appears from the end-nodes perspective as being simply an LSP
   rerouting without extra-traffic services.  The net result of this is
   that a single bit (the S bit alone) does not allow determining
   whether resource allocation should be performed with respect to the
   status of the LSP within the protected entity.  The introduction of
   the P bit solves this problem unambiguously.  These bits MUST be
   processed on a hop-by-hop basis (independently of the LSP Protection
   Type context).  This allows for an easier implementation of reversion

   signaling (see Section 12) but also facilitates the transparent
   delivery of protected services since any intermediate node is not
   required to know the semantics associated with the incoming LSP
   Protection Type value.

4.3.  LSP Association

   The ASSOCIATION object, introduced in Section 16, is used to
   associate the working and protecting LSPs.

   When used for signaling the working LSP, the Association ID of the
   ASSOCIATION object (see Section 16) identifies the protecting LSP.
   When used for signaling the protecting LSP, this field identifies the
   LSP protected by the protecting LSP.

5.  1+1 Unidirectional Protection

   One of the simplest notions of end-to-end LSP protection is 1+1
   unidirectional protection.

   Consider the following network topology:

                                  A---B---C---D
                                   \         /
                                    E---F---G

   The paths [A,B,C,D] and [A,E,F,G,D] are node and link disjoint,
   ignoring the ingress/egress nodes A and D.  A 1+1 protected path is
   established from A to D over [A,B,C,D] and [A,E,F,G,D], and traffic
   is transmitted simultaneously over both component paths (i.e., LSPs).

   During the provisioning phase, both LSPs are fully instantiated (and
   thus activated) so that no resource sharing can be done along the
   protecting LSP (nor can any extra-traffic be transported).  It is
   also RECOMMENDED to set the N bit since no protection-switching
   signaling is assumed in this case.

   When a failure occurs (say, at node B) and is detected at end-node D,
   the receiver at D selects the normal traffic from the other LSP.
   From this perspective, 1+1 unidirectional protection can be seen as
   an uncoordinated protection-switching mechanism acting independently
   at both endpoints.  Also, for the LSP under failure condition, it is
   RECOMMENDED to not set the Path_State_Removed Flag of the ERROR_SPEC
   object (see [RFC3473]) upon PathErr message generation.

   Note: it is necessary that both paths are SRLG disjoint to ensure
   recoverability; otherwise, a single failure may impact both working
   and protecting LSPs.

5.1.  Identifiers

   To simplify association operations, both LSPs belong to the same
   session.  Thus, the SESSION object MUST be the same for both LSPs.
   The LSP ID, however, MUST be different to distinguish between the two
   LSPs.

   A new PROTECTION object (see Section 14) is included in the Path
   message.  This object carries the desired end-to-end LSP Protection
   Type -- in this case, "1+1 Unidirectional".  This LSP Protection Type
   value is applicable to both uni- and bidirectional LSPs.

   To allow distinguishing the working LSP (from which the signal is
   taken) from the protecting LSP, the working LSP is signaled by
   setting in the PROTECTION object the S bit to 0, the P bit to 0, and
   in the ASSOCIATION object, the Association ID to the protecting
   LSP_ID.  The protecting LSP is signaled by setting in the PROTECTION
   object the S bit to 0, the P bit to 1, and in the ASSOCIATION object,
   the Association ID to the associated protected LSP_ID.

   After protection switching completes, and after reception of the
   PathErr message, to keep track of the LSP from which the signal is
   taken, the protecting LSP SHOULD be signaled with the O bit set.  The
   formerly working LSP MAY be signaled with the A bit set in the
   ADMIN_STATUS object (see [RFC3473]).  This process assumes the tail-
   end node has notified the head-end node that traffic selection
   switchover has occurred.

6.  1+1 Bidirectional Protection

   1+1 bidirectional protection is a scheme that provides end-to-end
   protection for bidirectional LSPs.

   Consider the following network topology:

                                  A---B---C---D
                                   \         /
                                    E---F---G

   The LSPs [A,B,C,D] and [A,E,F,G,D] are node and link disjoint,
   ignoring the ingress/egress nodes A and D.  A bidirectional LSP is
   established from A to D over each path, and traffic is transmitted
   simultaneously over both LSPs.  In this scheme, both endpoints must
   receive traffic over the same LSP.  Note also that both LSPs are
   fully instantiated (and thus activated) so that no resource sharing
   can be done along the protection path (nor can any extra-traffic be
   transported).

   When a failure is detected by one or both endpoints of the LSP, both
   endpoints must select traffic from the other LSP.  This action must
   be coordinated between node A and D.  From this perspective, 1+1
   bidirectional protection can be seen as a coordinated protection-
   switching mechanism between both endpoints.

   Note: it is necessary that both paths are SRLG disjoint to ensure
   recoverability; otherwise, a single failure may impact both working
   and protecting LSPs.

6.1.  Identifiers

   To simplify association operations, both LSPs belong to the same
   session.  Thus, the SESSION object MUST be the same for both LSPs.
   The LSP ID, however, MUST be different to distinguish between the two
   LSPs.

   A new PROTECTION object (see Section 14) is included in the Path
   message.  This object carries the desired end-to-end LSP Protection
   Type -- in this case, "1+1 Bidirectional".  This LSP Protection Type
   value is only applicable to bidirectional LSPs.

   It is also desirable to allow distinguishing the working LSP (from
   which the signal is taken) from the protecting LSP.  This is achieved
   for the working LSP by setting in the PROTECTION object the S bit to
   0, the P bit to 0, and in the ASSOCIATION object, the Association ID
   to the protecting LSP_ID.  The protecting LSP is signaled by setting
   in the PROTECTION object the S bit to 0, the P bit to 1, and in the
   ASSOCIATION object the Association ID to the associated protected
   LSP_ID.

6.2.  End-to-End Switchover Request/Response

   To coordinate the switchover between endpoints, an end-to-end
   switchover request/response exchange is needed since a failure
   affecting one of the LSPs results in both endpoints switching to the
   other LSP (resulting in receiving traffic from the other LSP) in
   their respective directions.

   The procedure is as follows:

      1. If an end-node (A or D) detects the failure of the working LSP
         (or a degradation of signal quality over the working LSP) or
         receives a Notify message including its SESSION object within
         the <upstream/downstream session list> (see [RFC3473]), and the
         new error code/sub-code "Notify Error/ LSP Locally Failed" in
         the (IF_ID)_ERROR_SPEC object, it MUST begin receiving on the
         protecting LSP.  Note that the <sender descriptor> or <flow

         descriptor> is also present in the Notify message that resolves
         any ambiguity and race condition since identifying (together
         with the SESSION object) the LSP under failure condition.

            Note: (IF_ID)_ERROR_SPEC indicates that either the
            ERROR_SPEC (C-Type 1/2) or the ERROR_SPEC (C-Type 3/4,
            defined in [RFC3473]) can be used.

         This node MUST reliably send a Notify message, including the
         MESSAGE_ID object, to the other end-node (D or A, respectively)
         with the new error code/sub-code "Notify Error/LSP Failure"
         (Switchover Request) indicating the failure of the working LSP.
         This Notify message MUST be sent with the ACK_Desired flag set
         in the MESSAGE_ID object to request the receiver to send an
         acknowledgment for the message (see [RFC2961]).

         This (switchover request) Notify message MAY indicate the
         identity of the failed link or any other relevant information
         using the IF_ID ERROR_SPEC object (see [RFC3473]).  In this
         case, the IF_ID ERROR_SPEC object replaces the ERROR_SPEC
         object in the Notify message; otherwise, the corresponding
         (data plane) information SHOULD be received in the
         PathErr/ResvErr message.

      2. Upon receipt of the (switchover request) Notify message, the
         end-node (D or A, respectively) MUST begin receiving from the
         protecting LSP.

         This node MUST reliably send a Notify message, including the
         MESSAGE_ID object, to the other end-node (A or D,
         respectively).  This (switchover response) Notify message MUST
         also include a MESSAGE_ID_ACK object to acknowledge reception
         of the (switchover request) Notify message.

         This (switchover response) Notify message MAY indicate the
         identity of the failed link or any other relevant information
         using the IF_ID ERROR_SPEC object (see [RFC3473]).

         Note: upon receipt of the (switchover response) Notify message,
         the end-node (A or D, respectively) MUST send an Ack message to
         the other end-node to acknowledge its reception.

   Since the intermediate nodes (B, C, E, F, and G) are assumed to be
   GMPLS RSVP-TE signaling capable, each node adjacent to the failure
   MAY generate a Notify message directed either to the LSP head-end
   (upstream direction), or the LSP tail-end (downstream direction), or
   even both.  Therefore, it is expected that these LSP terminating
   nodes (that MAY also detect the failure of the LSP from the data

   plane) provide either the right correlation mechanism to avoid
   repetition of the above procedure or just discard subsequent Notify
   messages corresponding to the same Session.  In addition, for the LSP
   under failure condition, it is RECOMMENDED to not set the Path_State_
   Removed Flag of the ERROR_SPEC object (see [RFC3473]) upon PathErr
   message generation.

   After protection switching completes (step 2), and after reception of
   the PathErr message, to keep track of the LSP from which the signal
   is taken, the protecting LSP SHOULD be signaled with the O bit set.
   The formerly working LSP MAY be signaled with the A bit set in the
   ADMIN_STATUS object (see [RFC3473]).

   Note: when the N bit is set, the end-to-end switchover request/
   response exchange described above only provides control plane
   coordination (no actions are triggered at the data plane level).

7.  1:1 Protection with Extra-Traffic

   The most common case of end-to-end 1:N protection is to establish,
   between the same endpoints, an end-to-end working LSP (thus, N = 1)
   and a dedicated end-to-end protecting LSP that are mutually link/
   node/SRLG disjoint.  This protects against working LSP failure(s).

   The protecting LSP is used for switchover when the working LSP fails.
   GMPLS RSVP-TE signaling allows for the pre-provisioning of protecting
   LSPs by indicating in the Path message (in the PROTECTION object; see
   Section 14) that the LSPs are of type protecting.  Here, working and
   protecting LSPs are signaled as primary LSPs; both are fully
   instantiated during the provisioning phase.

   Although the resources for the protecting LSP are pre-allocated,
   preemptable traffic may be carried end-to-end using this LSP.  Thus,
   the protecting LSP is capable of carrying extra-traffic with the
   caveat that this traffic will be preempted if the working LSP fails.

   The setup of the working LSP SHOULD indicate that the LSP head-end
   and tail-end node wish to receive Notify messages using the NOTIFY
   REQUEST object.  The node upstream to the failure (upstream in terms
   of the direction an Path message traverses) SHOULD send a Notify
   message to the LSP head-end node, and the node downstream to the
   failure SHOULD send an Notify message to the LSP tail-end node.  Upon
   receipt of the Notify messages, both the end-nodes MUST switch the
   (normal) traffic from the working LSP to the pre-configured
   protecting LSP (see Section 7.2).  Moreover, some coordination is
   required if extra-traffic is carried over the end-to-end protecting

   LSP.  Note that if the working and the protecting LSP are established
   between the same end-nodes, no further notification is required to
   indicate that the working LSPs are no longer protected.

   Consider the following topology:

                                  A---B---C---D
                                   \         /
                                    E---F---G

   The working LSP [A,B,C,D] could be protected by the protecting LSP
   [A,E,F,G,D].  Both LSPs are fully instantiated (resources are
   allocated for both working and protecting LSPs) and no resource
   sharing can be done along the protection path since the primary
   protecting LSP can carry extra-traffic.

   Note: it is necessary that both paths are SRLG disjoint to ensure
   recoverability; otherwise, a single failure may impact both working
   and protecting LSPs.

7.1.  Identifiers

   To simplify association operations, both LSPs belong to the same
   session.  Thus, the SESSION object MUST be the same for both LSPs.
   The LSP ID, however, MUST be different to distinguish between the
   protected LSP carrying working traffic and the protecting LSP that
   can carry extra-traffic.

   A new PROTECTION object (see Section 14) is included in the Path
   message used to set up the two LSPs.  This object carries the desired
   end-to-end LSP Protection Type -- in this case, "1:N Protection with
   Extra-Traffic".  This LSP Protection Type value is applicable to both
   uni- and bidirectional LSPs.

   The working LSP is signaled by setting in the new PROTECTION object
   the S bit to 0, the P bit to 0, and in the ASSOCIATION object, the
   Association ID to the protecting LSP_ID.

   The protecting LSP is signaled by setting in the new PROTECTION
   object the S bit to 0, the P bit to 1, and in the ASSOCIATION object,
   the Association ID to the associated protected LSP_ID.

7.2.  End-to-End Switchover Request/Response

   To coordinate the switchover between endpoints, an end-to-end
   switchover request/response is needed such that the affected LSP is
   moved to the protecting LSP.  Protection switching from the working
   to the protecting LSP (implying preemption of extra-traffic carried
   over the protecting LSP) must be initiated by one of the end-nodes (A
   or D).

   The procedure is as follows:

      1. If an end-node (A or D) detects the failure of the working LSP
         (or a degradation of signal quality over the working LSP) or
         receives a Notify message including its SESSION object within
         the <upstream/downstream session list> (see [RFC3473]), and the
         new error code/sub-code "Notify Error/LSP Locally Failed" in
         the (IF_ID)_ERROR_SPEC object, it disconnects the extra-traffic
         from the protecting LSP.  Note that the <sender descriptor> or
         <flow descriptor> is also present in the Notify message that
         resolves any ambiguity and race condition since identifying
         (together with the SESSION object) the LSP under failure
         condition.

         This node MUST reliably send a Notify message, including the
         MESSAGE_ID object, to the other end-node (D or A, respectively)
         with the new error code/sub-code "Notify Error/LSP Failure"
         (Switchover Request) indicating the failure of the working LSP.
         This Notify message MUST be sent with the ACK_Desired flag set
         in the MESSAGE_ID object to request the receiver to send an
         acknowledgment for the message (see [RFC2961]).

         This (switchover request) Notify message MAY indicate the
         identity of the failed link or any other relevant information
         using the IF_ID ERROR_SPEC object (see [RFC3473]).  In this
         case, the IF_ID ERROR_SPEC object replaces the ERROR_SPEC
         object in the Notify message; otherwise, the corresponding
         (data plane) information SHOULD be received in the
         PathErr/ResvErr message.

      2. Upon receipt of the (switchover request) Notify message, the
         end-node (D or A, respectively) MUST disconnect the extra-
         traffic from the protecting LSP and begin sending/receiving
         normal traffic out/from the protecting LSP.

         This node MUST reliably send a Notify message, including the
         MESSAGE_ID object, to the other end-node (A or D,
         respectively).  This (switchover response) Notify message MUST

         also include a MESSAGE_ID_ACK object to acknowledge reception
         of the (switchover request) Notify message.

         This (switchover response) Notify message MAY indicate the
         identity of the failed link or any other relevant information
         using the IF_ID ERROR_SPEC object (see [RFC3473]).

         Note: since the Notify message generated by the other end-node
         (A or D, respectively) is distinguishable from the one
         generated by an intermediate node, there is no possibility of
         connecting the extra-traffic to the working LSP due to the
         receipt of a Notify message from an intermediate node.

      3. Upon receipt of the (switchover response) Notify message, the
         end-node (A or D, respectively) MUST begin receiving normal
         traffic from or sending normal traffic out the protecting LSP.

         This node MUST also send an Ack message to the other end-node
         (D or A, respectively) to acknowledge the reception of the
         (switchover response) Notify message.

   Note 1: a 2-phase protection-switching signaling is used in the
   present context; a 3-phase signaling (see [RFC4426]) that would imply
   a notification message, a switchover request, and a switchover
   response messages is not considered here.  Also, when the protecting
   LSPs do not carry extra-traffic, protection-switching signaling (as
   defined in Section 6.2) MAY be used instead of the procedure
   described in this section.

   Note 2: when the N bit is set, the above end-to-end switchover
   request/response exchange only provides control plane coordination
   (no actions are triggered at the data plane level).

   After protection switching completes (step 3), and after reception of
   the PathErr message, to keep track of the LSP from which the normal
   traffic is taken, the protecting LSP SHOULD be signaled with the O
   bit set.  In addition, the formerly working LSP MAY be signaled with
   the A bit set in the ADMIN_STATUS object (see [RFC3473]).

7.3.  1:N (N > 1) Protection with Extra-Traffic

   1:N (N > 1) protection with extra-traffic assumes that the fully
   provisioned protecting LSP is resource-disjoint from the N working
   LSPs.  This protecting LSP thereby allows for carrying extra-traffic.
   Note that the N working LSPs and the protecting LSP are all between
   the same pair of endpoints.  In addition, the N working LSPs
   (considered as identical in terms of traffic parameters) MAY be

   mutually resource-disjoint.  Coordination between end-nodes is
   required when switching from one of the working to the protecting
   LSP.

   Each working LSP is signaled with both S bit and P bit set to 0.  The
   LSP Protection Type is set to 0x04 (1:N Protection with Extra-
   Traffic) during LSP setup.  Each Association ID points to the
   protecting LSP ID.

   The protecting LSP (carrying extra-traffic) is signaled with the S
   bit set to 0 and the P bit set to 1.  The LSP Protection Type is set
   to 0x04 (1:N Protection with Extra-Traffic) during LSP setup.  The
   Association ID MUST be set by default to the LSP ID of the protected
   LSP corresponding to N = 1.

   Any signaling procedure applicable to 1:1 protection with extra-
   traffic equally applies to 1:N protection with extra-traffic.

8.  Rerouting without Extra-Traffic

   End-to-end (pre-planned) rerouting without extra-traffic relies on
   the establishment between the same pair of end-nodes of a working LSP
   and a protecting LSP that is link/node/SRLG disjoint from the working
   LSP.  However, in this case the protecting LSP is not fully
   instantiated; thus, it cannot carry any extra-traffic (note that this
   does not mean that the corresponding resources cannot be used by
   other LSPs).  Therefore, this mechanism protects against working LSP
   failure(s) but requires activation of the protecting LSP after
   failure occurrence.

   Signaling is performed by indicating in the Path message (in the
   PROTECTION object; see Section 14) that the LSPs are of type working
   and protecting, respectively.  Protecting LSPs are used for fast
   switchover when working LSPs fail.  In this case, working and
   protecting LSPs are signaled as primary LSP and secondary LSP,
   respectively.  Thus, only the working LSP is fully instantiated
   during the provisioning phase, and for the protecting LSPs, no
   resources are committed at the data plane level (they are pre-
   reserved at the control plane level only).  The setup of the working
   LSP SHOULD indicate (using the NOTIFY REQUEST object as specified in
   Section 4 of [RFC3473]) that the LSP head-end node (and possibly the
   tail-end node) wish to receive a Notify message upon LSP failure
   occurrence.  Upon receipt of the Notify message, the head-end node
   MUST switch the (normal) traffic from the working LSP to the
   protecting LSP after its activation.  Note that since the working and
   the protecting LSPs are established between the same end-nodes, no
   further notification is required to indicate that the working LSPs
   are without protection.

   To make bandwidth pre-reserved for a protecting (but not activated)
   LSP available for extra-traffic, this bandwidth could be included in
   the advertised Unreserved Bandwidth at priority lower (means
   numerically higher) than the Holding Priority of the protecting LSP.
   In addition, the Max LSP Bandwidth field in the Interface Switching
   Capability Descriptor sub-TLV should reflect the fact that the
   bandwidth pre-reserved for the protecting LSP is available for extra
   traffic.  LSPs for extra-traffic then can be established using the
   bandwidth pre-reserved for the protecting LSP by setting (in the Path
   message) the Setup Priority field of the SESSION_ATTRIBUTE object to
   X (where X is the Setup Priority of the protecting LSP), and the
   Holding Priority field to at least X+1.  Also, if the resources pre-
   reserved for the protecting LSP are used by lower-priority LSPs,
   these LSPs MUST be preempted when the protecting LSP is activated
   (see Section 10).

   Consider the following topology:

                                  A---B---C---D
                                   \         /
                                    E---F---G

   The working LSP [A,B,C,D] could be protected by the protecting LSP
   [A,E,F,G,D].  Only the protected LSP is fully instantiated (resources
   are only allocated for the working LSP).  Therefore, the protecting
   LSP cannot carry any extra-traffic.  When a failure is detected on
   the working LSP (say, at B), the error is propagated and/or notified
   (using a Notify message with the new error code/sub-code "Notify
   Error/LSP Locally Failed" in the (IF_ID)_ERROR_SPEC object) to the
   ingress node (A).  Upon reception, the latter activates the secondary
   protecting LSP instantiated during the (pre-)provisioning phase.
   This requires:

   (1)  the ability to identify a "secondary protecting LSP" (hereby
        called the "secondary LSP") used to recover another primary
        working LSP (hereby called the "protected LSP")
   (2)  the ability to associate the secondary LSP with the protected
        LSP
   (3)  the capability to activate a secondary LSP after failure
        occurrence.

   In the following subsections, these features are described in more
   detail.

8.1.  Identifiers

   To simplify association operations, both LSPs (i.e., the protected
   and the secondary LSPs) belong to the same session.  Thus, the
   SESSION object MUST be the same for both LSPs.  The LSP ID, however,
   MUST be different to distinguish between the protected LSP carrying
   working traffic and the secondary LSP that cannot carry extra-
   traffic.

   A new PROTECTION object (see Section 14) is used to set up the two
   LSPs.  This object carries the desired end-to-end LSP Protection Type
   (in this case, "Rerouting without Extra-Traffic").  This LSP
   Protection Type value is applicable to both uni- and bidirectional
   LSPs.

8.2.  Signaling Primary LSPs

   The new PROTECTION object is included in the Path message during
   signaling of the primary working LSP, with the end-to-end LSP
   Protection Type value set to "Rerouting without Extra-Traffic".

   Primary working LSPs are signaled by setting in the new PROTECTION
   object the S bit to 0, the P bit to 0, and in the ASSOCIATION object,
   the Association ID to the associated secondary protecting LSP_ID.

8.3.  Signaling Secondary LSPs

   The new PROTECTION object is included in the Path message during
   signaling of secondary protecting LSPs, with the end-to-end LSP
   Protection Type value set to "Rerouting without Extra-Traffic".

   Secondary protecting LSPs are signaled by setting in the new
   PROTECTION object the S bit and the P bit to 1, and in the
   ASSOCIATION object, the Association ID to the associated primary
   working LSP_ID, which MUST be known before signaling of the secondary
   LSP.

   With this setting, the resources for the secondary LSP SHOULD be
   pre-reserved, but not committed at the data plane level, meaning that
   the internals of the switch need not be established until explicit
   action is taken to activate this secondary LSP.  Activation of a
   secondary LSP is done using a modified Path message with the S bit
   set to 0 in the PROTECTION object.  At this point, the link and node
   resources must be allocated for this LSP that becomes a primary LSP
   (ready to carry normal traffic).

   From [RFC3945], the secondary LSP is set up with resource pre-
   reservation but with or without label pre-selection (both allowing
   sharing of the recovery resources).  In the former case (defined as
   the default), label allocation during secondary LSP signaling does
   not require any specific procedure compared to [RFC3473].  However,
   in the latter case, label (and thus resource) re-allocation MAY occur
   during the secondary LSP activation.  This means that during the LSP
   activation phase, labels MAY be reassigned (with higher precedence
   over existing label assignment; see also [RFC3471]).

   Note: under certain circumstances (e.g., when pre-reserved protecting
   resources are used by lower-priority LSPs), it MAY be desirable to
   perform the activation of the secondary LSP in the upstream direction
   (Resv trigger message) instead of using the default downstream
   activation.  In this case, any mis-ordering and any mis-
   interpretation between a refresh Resv (along the lower-priority LSP)
   and a trigger Resv message (along the secondary LSP) MUST be avoided
   at any intermediate node.  For this purpose, upon reception of the
   Path message, the egress node MAY include the PROTECTION object in
   the Resv message.  The latter is then processed on a hop-by-hop basis
   to activate the secondary LSP until reaching the ingress node.  The
   PROTECTION object included in the Path message MUST be set as
   specified in this section.  In this case, the PROTECTION object with
   the S bit MUST be set to 0 and included in the Resv message sent in
   the upstream direction.  The upstream activation behavior SHOULD be
   configurable on a local basis.  Details concerning lower-priority LSP
   preemption upon secondary LSP activation are provided in Section 10.

9. Shared-Mesh Restoration

   An approach to reduce recovery resource requirements is to have
   protection LSPs sharing network resources when the working LSPs that
   they protect are physically (i.e., link, node, SRLG, etc.) disjoint.
   This mechanism is referred to as shared mesh restoration and is
   described in [RFC4426].  Shared-mesh restoration can be seen as a
   particular case of pre-planned LSP rerouting (see Section 8) that
   reduces the recovery resource requirements by allowing multiple
   protecting LSPs to share common link and node resources.  Here also,
   the recovery resources for the protecting LSPs are pre-reserved
   during the provisioning phase, thus an explicit signaling action is
   required to activate (i.e., commit resource allocation at the data
   plane) a specific protecting LSP instantiated during the (pre-)
   provisioning phase.  This requires restoration signaling along the
   protecting LSP.

   To make bandwidth pre-reserved for a protecting (but not activated)
   LSP, available for extra-traffic this bandwidth could be included in
   the advertised Unreserved Bandwidth at priority lower (means

   numerically higher) than the Holding Priority of the protecting LSP.
   In addition, the Max LSP Bandwidth field in the Interface Switching
   Capability Descriptor sub-TLV should reflect the fact that the
   bandwidth pre-reserved for the protecting LSP is available for extra
   traffic.  LSPs for extra-traffic then can be established using the
   bandwidth pre-reserved for the protecting LSP by setting (in the Path
   message) the Setup Priority field of the SESSION_ATTRIBUTE object to
   X (where X is the Setup Priority of the protecting LSP) and the
   Holding Priority field to at least X+1.  Also, if the resources pre-
   reserved for the protecting LSP are used by lower priority LSPs,
   these LSPs MUST be preempted when the protecting LSP is activated
   (see Section 10).  Further, if the recovery resources are shared
   between multiple protecting LSPs, the corresponding working LSPs
   head-end nodes must be informed that they are no longer protected
   when the protecting LSP is activated to recover the normal traffic
   for the working LSP under failure.

   Consider the following topology:

                                  A---B---C---D
                                   \         /
                                    E---F---G
                                   /         \
                                  H---I---J---K

   The working LSPs [A,B,C,D] and [H,I,J,K] could be protected by
   [A,E,F,G,D] and [H,E,F,G,K], respectively.  Per [RFC3209], in order
   to achieve resource sharing during the signaling of these protecting
   LSPs, they must have the same Tunnel Endpoint Address (as part of
   their SESSION object).  However, these addresses are not the same in
   this example.  Resource sharing along E, F, and G can only be
   achieved if the nodes E, F, and G recognize that the LSP Protection
   Type of the secondary LSP is set to "Rerouting without Extra-Traffic"
   (see PROTECTION object, Section 14) and acts accordingly.  In this
   case, the protecting LSPs are not merged (which is useful since the
   paths diverge at G), but the resources along E, F, G can be shared.

   When a failure is detected on one of the working LSPs (say, at B),
   the error is propagated and/or notified (using a Notify message with
   the new error code/sub-code "Notify Error/LSP Locally Failed" in the
   (IF_ID)_ERROR_SPEC object) to the ingress node (A).  Upon reception,
   the latter activates the secondary protecting LSP (see Section 8).
   At this point, it is important that a failure on the other LSP (say,
   at J) does not cause the other ingress (H) to send the data down the
   protecting LSP since the resources are already in use.  This can be
   achieved by node E using the following procedure.  When the capacity
   is first reserved for the protecting LSP, E should verify that the
   LSPs being protected ([A,B,C,D] and [H,I,J,K], respectively) do not

   share any common resources.  Then, when a failure occurs (say, at B)
   and the protecting LSP [A,E,F,G,D] is activated, E should notify H
   that the resources for the protecting LSP [H,E,F,G,K] are no longer
   available.

   The following subsections detail how shared mesh restoration can be
   implemented in an interoperable fashion using GMPLS RSVP-TE
   extensions (see [RFC3473]).  This includes:

   (1)  the ability to identify a "secondary protecting LSP" (hereby
        called the "secondary LSP") used to recover another primary
        working LSP (hereby called the "protected LSP")
   (2)  the ability to associate the secondary LSP with the protected
        LSP
   (3)  the capability to include information about the resources used
        by the protected LSP while instantiating the secondary LSP.
   (4)  the capability to instantiate during the provisioning phase
        several secondary LSPs in an efficient manner.
   (5)  the capability to activate a secondary LSP after failure
        occurrence.

   In the following subsections, these features are described in detail.

9.1.  Identifiers

   To simplify association operations, both LSPs (i.e., the protected
   and the secondary LSPs) belong to the same session.  Thus, the
   SESSION object MUST be the same for both LSPs.  The LSP ID, however,
   MUST be different to distinguish between the protected LSP carrying
   working traffic and the secondary LSP that cannot carry extra-
   traffic.

   A new PROTECTION object (see Section 14) is used to set up the two
   LSPs.  This object carries the desired end-to-end LSP Protection Type
   -- in this case, "Rerouting without Extra-Traffic".  This LSP
   Protection Type value is applicable to both uni- and bidirectional
   LSPs.

9.2.  Signaling Primary LSPs

   The new PROTECTION object is included in the Path message during
   signaling of the primary working LSPs, with the end-to-end LSP
   Protection Type value set to "Rerouting without Extra-Traffic".

   Primary working LSPs are signaled by setting in the new PROTECTION
   object the S bit to 0, the P bit to 0, and in the ASSOCIATION object,
   the Association ID to the associated secondary protecting LSP_ID.

9.3.  Signaling Secondary LSPs

   The new PROTECTION object is included in the Path message during
   signaling of the secondary protecting LSPs, with the end-to-end LSP
   Protection Type value set to "Rerouting without Extra-Traffic".

   Secondary protecting LSPs are signaled by setting in the new
   PROTECTION object the S bit and the P bit to 1, and in the
   ASSOCIATION object, the Association ID to the associated primary
   working LSP_ID, which MUST be known before signaling of the secondary
   LSP.  Moreover, the Path message used to instantiate the secondary
   LSP SHOULD include at least one PRIMARY_PATH_ROUTE object (see
   Section 15) that further allows for recovery resource sharing at each
   intermediate node along the secondary path.

   With this setting, the resources for the secondary LSP SHOULD be
   pre-reserved, but not committed at the data plane level, meaning that
   the internals of the switch need not be established until explicit
   action is taken to activate this LSP.  Activation of a secondary LSP
   is done using a modified Path message with the S bit set to 0 in the
   PROTECTION object.  At this point, the link and node resources must
   be allocated for this LSP that becomes a primary LSP (ready to carry
   normal traffic).

   From [RFC3945], the secondary LSP is set up with resource pre-
   reservation but with or without label pre-selection (both allowing
   sharing of the recovery resources).  In the former case (defined as
   the default), label allocation during secondary LSP signaling does
   not require any specific procedure compared to [RFC3473].  However,
   in the latter case, label (and thus resource) re-allocation MAY occur
   during the secondary LSP activation.  This means that, during the LSP
   activation phase, labels MAY be reassigned (with higher precedence
   over existing label assignment; see also [RFC3471]).

10.  LSP Preemption

   When protecting resources are only pre-reserved for the secondary
   LSPs, they MAY be used to set up lower-priority LSPs.  In this case,
   these resources MUST be preempted when the protecting LSP is
   activated.  An additional condition raises from misconnection
   avoidance between the secondary protecting LSP being activated and
   the low-priority LSP(s) being preempted.  Procedure to be applied
   when the secondary protecting LSP (i.e., the preempting LSP) Path
   message reaches a node using the resources for lower-priority LSP(s)
   (i.e., preempted LSP(s)) is as follows:

   1. De-allocate resources to be used by the preempting LSP and release
      the cross-connection.  Note that if the preempting LSP is
      bidirectional, these resources may come from one or two lower-
      priority LSPs, and if from two LSPs, they may be uni- or bi-
      directional.  The preempting node SHOULD NOT send the Path message
      before the de-allocation of resources has completed since this may
      lead to the downstream path becoming misconnected if the
      downstream node is able to reassign the resources more quickly.

   2. Send PathTear and PathErr messages with the new error code/sub-
      code "Policy Control failure/Hard preempted" and the
      Path_State_Removed flag set for the preempted LSP(s).

   3. Reserve the preempted resources for the protecting LSP.  The
      preempting node MUST NOT cross-connect the upstream resources of a
      bidirectional preempting LSP.

   4. Send the Path message.

   5. Upon reception of a trigger Resv message from the downstream node,
      cross-connect the downstream path resources, and if the preempting
      LSP is bidirectional, perform cross-connection for the upstream
      path resources.

   Note that step 1 may cause alarms to be raised for the preempted LSP.
   If alarm suppression is desired, the preempting node MAY insert the
   following steps before step 1.

   1a. Before de-allocating resources, send a Resv message, including an
       ADMIN_STATUS object, to disable alarms for the preempted LSP.
   1b. Receive a Path message indicating that alarms are disabled.

   At the downstream node (with respect to the preempting LSP), the
   processing is RECOMMENDED to be as follows:

   1.  Receive PathTear (and/or PathErr) message for the preempted
       LSP(s).

   2a. Release the resources associated with the LSP on the interface to
       the preempting LSP, remove any cross-connection, and release all
       other resources associated with the preempted LSP.
   2b. Forward the PathTear (and/or PathErr) message per [RFC3473].

   3.  Receive the Path message for the preempting LSP and process as
       normal, forwarding it to the downstream node.

   4.  Receive the Resv message for the preempting LSP and process as
       normal, forwarding it to the upstream node.

11.  (Full) LSP Rerouting

   LSP rerouting, on the other hand, switches normal traffic to an
   alternate LSP that is fully established only after failure
   occurrence.  The new (alternate) route is selected at the LSP head-
   end and may reuse intermediate nodes included in the original route;
   it may also include additional intermediate nodes.  For strict-hop
   routing, TE requirements can be directly applied to the route
   computation, and the failed node or link can be avoided.  However, if
   the failure occurred within a loose-routed hop, the head-end node may
   not have enough information to reroute the LSP around the failure.
   Crankback signaling (see [CRANK]) and route exclusion techniques (see
   [RFC4874]) MAY be used in this case.

   The alternate route MAY be either computed on demand (that is, when
   the failure occurs; this is referred to as full LSP rerouting) or
   pre-computed and stored for use when the failure is reported.  The
   latter offers faster restoration time.  There is, however, a risk
   that the alternate route will become out of date through other
   changes in the network; this can be mitigated to some extent by
   periodic recalculation of idle alternate routes.

   (Full) LSP rerouting will be initiated by the head-end node that has
   either detected the LSP failure or received a Notify message and/or a
   PathErr message with the new error code/sub-code "Notify Error/LSP
   Locally Failed" for this LSP.  The new LSP resources can be
   established using the make-before-break mechanism, where the new LSP
   is set up before the old LSP is torn down.  This is done by using the
   mechanisms of the SESSION_ATTRIBUTE object and the Shared-Explicit
   (SE) reservation style (see [RFC3209]).  Both the new and old LSPs
   can share resources at common nodes.

   Note that the make-before-break mechanism is not used to avoid
   disruption to the normal traffic flow (the latter has already been
   broken by the failure that is being repaired).  However, it is
   valuable to retain the resources allocated on the original LSP that
   will be reused by the new alternate LSP.

11.1.  Identifiers

   The Tunnel Endpoint Address, Tunnel ID, Extended Tunnel ID, and
   Tunnel Sender Address uniquely identify both the old and new LSPs.
   Only the LSP_ID value differentiates the old from the new alternate
   LSP.  The new alternate LSP is set up before the old LSP is torn down
   using Shared-Explicit (SE) reservation style.  This ensures that the
   new (alternate) LSP is established without double-counting resource
   requirements along common segments.

   The alternate LSP MAY be set up before any failure occurrence with
   SE-style resource reservation, the latter shares the same Tunnel End
   Point Address, Tunnel ID, Extended Tunnel ID, and Tunnel Sender
   Address with the original LSP (i.e., only the LSP ID value MUST be
   different).

   In both cases, the Association ID of the ASSOCIATION object MUST be
   set to the LSP ID value of the signaled LSP.

11.2.  Signaling Reroutable LSPs

   A new PROTECTION object is included in the Path message during
   signaling of dynamically reroutable LSPs, with the end-to-end LSP
   Protection Type value set to "Full Rerouting".  These LSPs that can
   be either uni- or bidirectional are signaled by setting in the
   PROTECTION object the S bit to 0, the P bit to 0, and the Association
   ID value to the LSP_ID value of the signaled LSP.  Any specific
   action to be taken during the provisioning phase is up to the end-
   node local policy.

   Note: when the end-to-end LSP Protection Type is set to
   "Unprotected", both S and P bit MUST be set to 0, and the LSP SHOULD
   NOT be rerouted at the head-end node after failure occurrence.  The
   Association_ID value MUST be set to the LSP_ID value of the signaled
   LSP.  This does not mean that the Unprotected LSP cannot be re-
   established for other reasons such as path re-optimization and
   bandwidth adjustment driven by policy conditions.

12.  Reversion

   Reversion refers to a recovery switching operation, where the normal
   traffic returns to (or remains on) the working LSP when it has
   recovered from the failure.  Reversion implies that resources remain
   allocated to the LSP that was originally routed over them even after
   a failure.  It is important to have mechanisms that allow reversion
   to be performed with minimal service disruption and reconfiguration.

   For "1+1 bidirectional Protection", reversion to the recovered LSP
   occurs by using the following sequence:

   1. Clear the A bit of the ADMIN_STATUS object if set for the
      recovered LSP.

   2. Then, apply the method described below to switch normal traffic
      back from the protecting to the recovered LSP.  This is performed
      by using the new error code/sub-code "Notify Error/LSP Recovered"
      (Switchback Request).

      The procedure is as follows:

      1) The initiating (source) node sends the normal traffic onto both
         the working and the protecting LSPs.  Once completed, the
         source node sends reliably a Notify message to the destination
         with the new error code/sub-code "Notify Error/LSP Recovered"
         (Switchback Request).  This Notify message includes the
         MESSAGE_ID object.  The ACK_Desired flag MUST be set in this
         object to request the receiver to send an acknowledgment for
         the message (see [RFC2961]).

      2) Upon receipt of this message, the destination selects the
         traffic from the working LSP.  At the same time, it transmits
         the traffic onto both the working and protecting LSP.

         The destination then sends reliably a Notify message to the
         source confirming the completion of the operation.  This
         message includes the MESSAGE_ID_ACK object to acknowledge
         reception of the received Notify message.  This Notify message
         also includes the MESSAGE_ID object.  The ACK_Desired flag MUST
         be set in this object to request the receiver to send an
         acknowledgment for the message (see [RFC2961]).

      3) When the source node receives this Notify message, it switches
         to receive traffic from the working LSP.

         The source node then sends an Ack message to the destination
         node confirming that the LSP has been reverted.

   3. Finally, clear the O bit of the PROTECTION object sent over the
      protecting LSP.

   For "1:N Protection with Extra-traffic", reversion to the recovered
   LSP occurs by using the following sequence:

   1. Clear the A bit of the ADMIN_STATUS object if set for the
      recovered LSP.

   2. Then, apply the method described below to switch normal traffic
      back from the protecting to the recovered LSP.  This is performed
      by using the new error code/sub-code "Notify Error/LSP Recovered"
      (Switchback Request).

      The procedure is as follows:

      1) The initiating (source) node sends the normal traffic onto both
         the working and the protecting LSPs.  Once completed, the
         source node sends reliably a Notify message to the destination

         with the new error code/sub-code "Notify Error/LSP Recovered"
         (Switchback Request).  This Notify message includes the
         MESSAGE_ID object.  The ACK_Desired flag MUST be set in this
         object to request the receiver to send an acknowledgment for
         the message (see [RFC2961]).

      2) Upon receipt of this message, the destination selects the
         traffic from the working LSP.  At the same time, it transmits
         the traffic onto both the working and protecting LSP.

         The destination then sends reliably a Notify message to the
         source confirming the completion of the operation.  This
         message includes the MESSAGE_ID_ACK object to acknowledge
         reception of the received Notify message.  This Notify message
         also includes the MESSAGE_ID object.  The ACK_Desired flag MUST
         be set in this object to request the receiver to send an
         acknowledgment for the message (see [RFC2961]).

      3) When the source node receives this Notify message, it switches
         to receive traffic from the working LSP, and stops transmitting
         traffic on the protecting LSP.

         The source node then sends an Ack message to the destination
         node confirming that the LSP has been reverted.

      4) Upon receipt of this message, the destination node stops
         transmitting traffic along the protecting LSP.

   3. Finally, clear the O bit of the PROTECTION object sent over the
      protecting LSP.

   For "Rerouting without Extra-traffic" (including the shared recovery
   case), reversion implies that the formerly working LSP has not been
   torn down by the head-end node upon PathErr message reception, i.e.,
   the head-end node kept refreshing the working LSP under failure
   condition.  This ensures that the exact same resources are retrieved
   after reversion switching (except if the working LSP required re-
   signaling).  Re-activation is performed using the following sequence:

   1. Clear the A bit of the ADMIN_STATUS object if set for the
      recovered LSP.

   2. Then, apply the method described below to switch normal traffic
      back from the protecting to the recovered LSP.  This is performed
      by using the new error code/sub-code "Notify Error/LSP Recovered"
      (Switchback Request).

      The procedure is as follows:

      1) The initiating (source) node sends the normal traffic onto both
         the working and the protecting LSPs.  Once completed, the
         source node sends reliably a Notify message to the destination
         with the new error code/sub-code "Notify Error/LSP Recovered"
         (Switchback Request).  This Notify message includes the
         MESSAGE_ID object.  The ACK_Desired flag MUST be set in this
         object to request the receiver to send an acknowledgment for
         the message (see [RFC2961]).

      2) Upon receipt of this message, the destination selects the
         traffic from the working LSP.  At the same time, it transmits
         the traffic onto both the working and protecting LSP.

         The destination then sends reliably a Notify message to the
         source confirming the completion of the operation.  This
         message includes the MESSAGE_ID_ACK object to acknowledge
         reception of the received Notify message.  This Notify message
         also includes the MESSAGE_ID object.  The ACK_Desired flag MUST
         be set in this object to request the receiver to send an
         acknowledgment for the message (see [RFC2961]).

      3) When the source node receives this Notify message, it switches
         to receive traffic from the working LSP, and stops transmitting
         traffic on the protecting LSP.

         The source node then sends an Ack message to the destination
         node confirming that the LSP has been reverted.

      4) Upon receipt of this message, the destination node stops
         transmitting traffic along the protecting LSP.

   3. Finally, de-activate the protecting LSP by setting the S bit to 1
      in the PROTECTION object sent over the protecting LSP.

13.  Recovery Commands

   This section specifies the control plane behavior when using several
   commands (see [RFC4427]) that can be used to influence the recovery
   operations.

   A. Lockout of recovery LSP:

   The Lockout (L) bit of the ADMIN_STATUS object is used following the
   rules defined in Section 8 of [RFC3471] and Section 7 of [RFC3473].
   The L bit must be set together with the Reflect (R) bit in the
   ADMIN_STATUS object sent in the Path message.  Upon reception of the

   Resv message with the L bit set, this forces the recovery LSP to be
   temporarily unavailable to transport traffic (either normal or
   extra-traffic).  Unlock is performed by clearing the L bit, following
   the rules defined in Section 7 of [RFC3473].  This procedure is only
   applicable when the LSP Protection Type Flag is set to either 0x04
   (1:N Protection with Extra-Traffic), or 0x08 (1+1 Unidirectional
   Protection), or 0x10 (1+1 Bidirectional Protection).

   The updated format of the ADMIN_STATUS object to include the L bit is
   as follows:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            Length             | Class-Num(196)|   C-Type (1)  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |R|                        Reserved                 |L|I|C|T|A|D|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Lockout (L): 1 bit

        When set, forces the recovery LSP to be temporarily unavailable
        to transport traffic (either normal or extra traffic).

   The R (Reflect), T (Testing), A (Administratively down), and D
   (Deletion in progress) bits are defined in [RFC3471].  The C (Call
   control) bit is defined in [GMPLS-CALL], and the I (Inhibit alarm
   communication) bit in [RFC4783].

   B. Lockout of normal traffic:

   The O bit of the PROTECTION object is set to 1 to force the recovery
   LSP to be temporarily unavailable to transport normal traffic.  This
   operation MUST NOT occur unless the working LSP is carrying the
   normal traffic.  Unlock is performed by clearing the O bit over the
   protecting LSP.  This procedure is only applicable when the LSP
   Protection Type Flag is set to either 0x04 (1:N Protection with
   Extra-Traffic), or 0x08 (1+1 Unidirectional Protection), or 0x10 (1+1
   Bidirectional Protection).

   C. Forced switch for normal traffic:

   Recovery signaling is initiated that switches normal traffic to the
   recovery LSP following the procedures defined in Section 6, 7, 8, and
   9.

   D. Requested switch for normal traffic:

   Recovery signaling is initiated that switches normal traffic to the
   recovery LSP following the procedures defined in Section 6, 7, 8, and
   9.  This happens unless a fault condition exists on other LSPs or
   spans (including the recovery LSP), or a switch command of equal or
   higher priority is in effect.

   E. Requested switch for recovery LSP:

   Recovery signaling is initiated that switches normal traffic to the
   working LSP following the procedure defined in Section 12.  This
   request is executed except if a fault condition exists on the working
   LSP or an equal or higher priority switch command is in effect.

14.  PROTECTION Object

   This section describes the extensions to the PROTECTION object to
   broaden its applicability to end-to-end LSP recovery.

14.1.  Format

   The format of the PROTECTION Object (Class-Num = 37, C-Type = 2) is
   as follows:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Length             | Class-Num(37) | C-Type (2)    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |S|P|N|O| Reserved  | LSP Flags |     Reserved      | Link Flags|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           Reserved                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Secondary (S): 1 bit

         When set to 1, this bit indicates that the requested LSP is a
         secondary LSP.  When set to 0 (default), it indicates that the
         requested LSP is a primary LSP.

      Protecting (P): 1 bit

         When set to 1, this bit indicates that the requested LSP is a
         protecting LSP.  When set to 0 (default), it indicates that the
         requested LSP is a working LSP.  The combination, S set to 1
         with P set to 0 is not valid.

      Notification (N): 1 bit

         When set to 1, this bit indicates that the control plane
         message exchange is only used for notification during
         protection switching.  When set to 0 (default), it indicates
         that the control plane message exchanges are used for
         protection-switching purposes.  The N bit is only applicable
         when the LSP Protection Type Flag is set to either 0x04 (1:N
         Protection with Extra-Traffic), or 0x08 (1+1 Unidirectional
         Protection), or 0x10 (1+1 Bidirectional Protection).  The N bit
         MUST be set to 0 in any other case.

      Operational (O): 1 bit

         When set to 1, this bit indicates that the protecting LSP is
         carrying the normal traffic after protection switching.  The O
         bit is only applicable when the P bit is set to 1, and the LSP
         Protection Type Flag is set to either 0x04 (1:N Protection with
         Extra-Traffic), or 0x08 (1+1 Unidirectional Protection) or 0x10
         (1+1 Bidirectional Protection).  The O bit MUST be set to 0 in
         any other case.

      Reserved: 5 bits

         This field is reserved.  It MUST be set to zero on transmission
         and MUST be ignored on receipt.  These bits SHOULD be passed
         through unmodified by transit nodes.

      LSP (Protection Type) Flags: 6 bits

         Indicates the desired end-to-end LSP recovery type.  A value of
         0 implies that the LSP is "Unprotected".  Only one value SHOULD
         be set at a time.  The following values are defined.  All other
         values are reserved.

                0x00    Unprotected
                0x01    (Full) Rerouting
                0x02    Rerouting without Extra-Traffic
                0x04    1:N Protection with Extra-Traffic
                0x08    1+1 Unidirectional Protection
                0x10    1+1 Bidirectional Protection

      Reserved: 10 bits

         This field is reserved.  It MUST be set to zero on transmission
         and MUST be ignored on receipt.  These bits SHOULD be passed
         through unmodified by transit nodes.

      Link Flags: 6 bits

         Indicates the desired link protection type (see [RFC3471]).

      Reserved field: 32 bits

         Encoding of this field is detailed in [RFC4873].

14.2.  Processing

   Intermediate and egress nodes processing a Path message containing a
   PROTECTION object MUST verify that the requested LSP Protection Type
   can be satisfied by the incoming interface.  If it cannot, the node
   MUST generate a PathErr message, with the new error code/sub-code
   "Routing problem/Unsupported LSP Protection".

   Intermediate nodes processing a Path message containing a PROTECTION
   object with the LSP Protection Type 0x02 (Rerouting without Extra-
   Traffic) value set and a PRIMARY_PATH_ROUTE object (see Section 15)
   MUST verify that the requested LSP Protection Type can be supported
   by the outgoing interface.  If it cannot, the node MUST generate a
   PathErr message with the new error code/sub-code "Routing
   problem/Unsupported LSP Protection".

15.  PRIMARY_PATH_ROUTE Object

   The PRIMARY_PATH_ROUTE object (PPRO) is defined to inform nodes along
   the path of a secondary protecting LSP about which resources
   (link/nodes) are being used by the associated primary protected LSP
   (as specified by the Association ID field).  If the LSP Protection
   Type value is set to 0x02 (Rerouting without Extra-Traffic), this
   object SHOULD be present in the Path message for the pre-provisioning
   of the secondary protecting LSP to enable recovery resource sharing
   between one or more secondary protecting LSPs (see Section 9).  This
   document does not assume or preclude any other usage for this object.

   PRIMARY_PATH_ROUTE objects carry information extracted from the
   EXPLICIT ROUTE object and/or the RECORD ROUTE object of the primary
   working LSPs they protect.  Selection of the PPRO content is up to
   local policy of the head-end node that initiates the request.
   Therefore, the information included in these objects can be used as
   policy-based admission control to ensure that recovery resources are
   only shared between secondary protecting LSPs whose associated
   primary LSPs have link/node/SRLG disjoint paths.

15.1.  Format

   The primary path route is specified via the PRIMARY_PATH_ROUTE object
   (PPRO).  The Primary Path Route Class Number (Class-Num) of form
   0bbbbbbb 38.

   Currently one C-Type (Class-Type) is defined, Type 1, Primary Path
   Route.  The PRIMARY_PATH_ROUTE object has the following format:

   Class-Num = 38 (of the form 0bbbbbbb), C-Type = 1

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     //                        (Subobjects)                         //
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The contents of a PRIMARY_PATH_ROUTE object are a series of
   variable-length data items called subobjects (see Section 15.3).

   To signal a secondary protecting LSP, the Path message MAY include
   one or multiple PRIMARY_PATH_ROUTE objects, where each object is
   meaningful.  The latter is useful when a given secondary protecting
   LSP must be link/node/SRLG disjoint from more than one primary LSP
   (i.e., is protecting more than one primary LSP).

15.2.  Subobjects

   The PRIMARY_PATH_ROUTE object is defined as a list of variable-length
   data items called subobjects.  These subobjects are derived from the
   subobjects of the EXPLICIT ROUTE and/or RECORD ROUTE object of the
   primary working LSP(s).

   Each subobject has its own length field.  The length contains the
   total length of the subobject in bytes, including the Type and Length
   fields.  The length MUST always be a multiple of 4, and at least 4.

   The following subobjects are currently defined for the
   PRIMARY_PATH_ROUTE object:

   - Sub-Type 1: IPv4 Address (see [RFC3209])
   - Sub-Type 2: IPv6 Address (see [RFC3209])
   - Sub-Type 3: Label (see [RFC3473])
   - Sub-Type 4: Unnumbered Interface (see [RFC3477])

   An empty PPRO with no subobjects is considered illegal.  If there is
   no first subobject, the corresponding Path message is also in error,
   and the receiving node SHOULD return a PathErr message with the new
   error code/sub-code "Routing Problem/Bad PRIMARY_PATH_ROUTE object".

   Note: an intermediate node processing a PPRO can derive SRLG
   identifiers from the local IGP-TE database using its Type 1, 2, or 4
   subobject values as pointers to the corresponding TE Links (assuming
   each of them has an associated SRLG TE attribute).

15.3.  Applicability

   The PRIMARY_PATH_ROUTE object MAY only be used when all GMPLS nodes
   along the path support the PRIMARY_PATH_ROUTE object and a secondary
   protecting LSP is being requested.  The PRIMARY_PATH_ROUTE object is
   assigned a class value of the form 0bbbbbbb.  Receiving GMPLS nodes
   along the path that do not support this object MUST return a PathErr
   message with the "Unknown Object Class" error code (see [RFC2205]).

   Also, the following restrictions MUST be applied with respect to the
   PPRO usage:

   - PPROs MAY only be included in Path messages when signaling
     secondary protecting LSPs (S bit = 1 and P bit = 1) and when the
     LSP Protection Type value is set to 0x02 (without Rerouting Extra-
     Traffic) in the PROTECTION object (see Section 14).

   - PRROs SHOULD be present in the Path message for the pre-
     provisioning of the secondary protecting LSP to enable recovery
     resource sharing between one or more secondary protecting LSPs (see
     Section 15.4).

   - PPROs MUST NOT be used in any other conditions.  In particular, if
     a PPRO is received when the S bit is set to 0 in the PROTECTION
     object, the receiving node MUST return a PathErr message with the
     new error code/sub-code "Routing Problem/PRIMARY_PATH_ROUTE object
     not applicable".

   - Crossed exchanges of PPROs over primary LSPs are forbidden (i.e.,
     their usage is restricted to a single set of protected LSPs).

   - The PPRO's content MUST NOT include subobjects coming from other
     PPROs.  In particular, received PPROs MUST NOT be reused to
     establish other working or protecting LSPs.

15.4.  Processing

   The PPRO enables sharing recovery resources between a given secondary
   protecting LSP and one or more secondary protecting LSPs if their
   corresponding primary working LSPs have mutually (link/node/SRLG)
   disjoint paths.  Consider a node N through which n secondary
   protecting LSPs (say, P[1],...,P[n]) have already been established
   that protect n primary working LSPs (say, P'[1],...,P'[n]).  Suppose
   also that these n secondary working LSPs share a given outgoing link
   resource (say r).

   Now, suppose that node N receives a Path message for an additional
   secondary protecting LSP (say, Q, protecting Q').  The PPRO carried
   by this Path message is processed as follows:

   - N checks whether the primary working LSPs P'[1],...,P'[n]
     associated with the LSPs P[1],...,P[n], respectively, have any
     link, node, and SLRG in common with the primary working Q'
     (associated with Q) by comparing the stored PPRO subobjects
     associated with P'[1],...,P'[n] with the PPRO subobjects associated
     with Q' received in the Path message.

   - If this is the case, N SHOULD NOT attempt to share the outgoing
     link resource r between P[1],...,P[n] and Q.  However, upon local
     policy decision, N MAY allocate another available (shared) link
     other than r for use by Q.  If this is not the case (upon the local
     policy decision that no other link is allowed to be allocated for
     Q) or if no other link is available for Q, N SHOULD return a
     PathErr message with the new error code/sub-code "Admission Control
     Failure/LSP Admission Failure".

   - Otherwise (if P'[1],...,P'[n] and Q' are fully disjoint), the link
     r selected by N for the LSP Q MAY be exactly the same as the one
     selected for the LSPs P[1],...,P[n].  This happens after verifying
     (from the node's local policy) that the selected link r can be
     shared between these LSPs.  If this is not the case (for instance,
     the sharing ratio has reached its maximum for that link), and if
     upon local policy decision, no other link is allowed to be
     allocated for Q, N SHOULD return a PathErr message with the error
     code/sub-code "Admission Control Failure/Requested Bandwidth
     Unavailable" (see [RFC2205]).  Otherwise (if no other link is
     available), N SHOULD return a PathErr message with the new error
     code/sub-code "Admission Control Failure/LSP Admission Failure".

   Note that the process, through which m out of the n (m =< n)
   secondary protecting LSPs' PPROs may be selected on a local basis to
   perform the above comparison and subsequent link selection, is out of
   scope of this document.

16.  ASSOCIATION Object

   The ASSOCIATION object is used to associate LSPs with each other.  In
   the context of end-to-end LSP recovery, the association MUST only
   identify LSPs that support the same Tunnel ID as well as the same
   tunnel sender address and tunnel endpoint address.  The Association
   Type, Association Source, and Association ID fields of the object
   together uniquely identify an association.  The object uses an object
   class number of the form 11bbbbbb to ensure compatibility with non-
   supporting nodes.

   The ASSOCIATION object is used to associate LSPs with each other.

16.1.  Format

   The IPv4 ASSOCIATION object (Class-Num of the form 11bbbbbb with
   value = 199, C-Type = 1) has the 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            Length             | Class-Num(199)|  C-Type (1)   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Association Type        |       Association ID          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  IPv4 Association Source                      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The IPv6 ASSOCIATION object (Class-Num of the form 11bbbbbb with
   value = 199, C-Type = 2) has the 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |            Length             | Class-Num(199)|  C-Type (2)   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Association Type        |       Association ID          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                  IPv6 Association Source                      |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Association Type: 16 bits

         Indicates the type of association being identified.  Note that
         this value is considered when determining association.  The
         following are values defined in this document.

            Value       Type
            -----       ----
              0         Reserved
              1         Recovery (R)

      Association ID: 16 bits

         A value assigned by the LSP head-end.  When combined with the
         Association Type and Association Source, this value uniquely
         identifies an association.

      Association Source: 4 or 16 bytes

         An IPv4 or IPv6 address, respectively, that is associated to
         the node that originated the association.

16.2.  Processing

   In the end-to-end LSP recovery context, the ASSOCIATION object is
   used to associate a recovery LSP with the LSP(s) it is protecting or
   a protected LSP(s) with its recovery LSP.  The object is carried in
   Path messages.  More than one object MAY be carried in a single Path
   message.

   Transit nodes MUST transmit, without modification, any received
   ASSOCIATION object in the corresponding outgoing Path message.

   An ASSOCIATION object with an Association Type set to the value
   "Recovery" is used to identify an LSP-Recovery-related association.
   Any node associating a recovery LSP MUST insert an ASSOCIATION object
   with the following setting:

   - The Association Type MUST be set to the value "Recovery" in the
     Path message of the recovery LSP.

   - The (IPv4/IPv6) Association Source MUST be set to the tunnel sender
     address of the LSP being protected.

   - The Association ID MUST be set to the LSP ID of the LSP being
     protected by this LSP or the LSP protecting this LSP.  If unknown,
     this value is set to its own signaled LSP_ID value (default).
     Also, the value of the Association ID MAY change during the
     lifetime of the LSP.

   Terminating nodes use received ASSOCIATION object(s) with the
   Association Type set to the value "Recovery" to associate a recovery
   LSP with its matching working LSP.  This information is used to bind
   the appropriate working and recovery LSPs together.  Such nodes MUST
   ensure that the received Path messages, including ASSOCIATION
   object(s), are processed with the appropriate PROTECTION object
   settings, if present (see Section 14 for PROTECTION object
   processing).  Otherwise, this node MUST return a PathErr message with
   the new error code/sub-code "LSP Admission Failure/Bad Association
   Type".  Similarly, terminating nodes receiving a Path message with a

   PROTECTION object requiring association between working and recovery
   LSPs MUST include an ASSOCIATION object.  Otherwise, such nodes MUST
   return a PathErr message with the new error code/sub-code "Routing
   Problem/PROTECTION object not Applicable".

17.  Updated RSVP Message Formats

   This section presents the RSVP message-related formats as modified by
   this document.  Unmodified RSVP message formats are not listed.

   The format of a Path message is as follows:

   <Path Message> ::= <Common Header> [ <INTEGRITY> ]
                      [ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ... ]
                      [ <MESSAGE_ID> ]
                      <SESSION> <RSVP_HOP>
                      <TIME_VALUES>
                      [ <EXPLICIT_ROUTE> ]
                      <LABEL_REQUEST>
                      [ <PROTECTION> ]
                      [ <LABEL_SET> ... ]
                      [ <SESSION_ATTRIBUTE> ]
                      [ <NOTIFY_REQUEST> ... ]
                      [ <ADMIN_STATUS> ]
                      [ <ASSOCIATION> ... ]
                      [ <PRIMARY_PATH_ROUTE> ... ]
                      [ <POLICY_DATA> ... ]
                      <sender descriptor>

   The format of the <sender descriptor> for unidirectional and
   bidirectional LSPs is not modified by the present document.

   The format of a Resv message is as follows:

   <Resv Message> ::= <Common Header> [ <INTEGRITY> ]
                      [ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ... ]
                      [ <MESSAGE_ID> ]
                      <SESSION> <RSVP_HOP>
                      <TIME_VALUES>
                      [ <RESV_CONFIRM> ]  [ <SCOPE> ]
                      [ <PROTECTION> ]
                      [ <NOTIFY_REQUEST> ]
                      [ <ADMIN_STATUS> ]
                      [ <POLICY_DATA> ... ]
                      <STYLE> <flow descriptor list>

      <flow descriptor list> is not modified by this document.

18.  Security Considerations

   The security threats identified in [RFC4426] may be experienced due
   to the exchange of RSVP messages and information as detailed in this
   document.  The following security mechanisms apply.

   RSVP signaling MUST be able to provide authentication and integrity.
   Authentication is required to ensure that the signaling messages are
   originating from the right place and have not been modified in
   transit.

   For this purpose, [RFC2747] provides the required RSVP message
   authentication and integrity for hop-by-hop RSVP message exchanges.
   For non hop-by-hop RSVP message exchanges the standard IPsec-based
   integrity and authentication can be used as explained in [RFC3473].

   Moreover, this document makes use of the Notify message exchange.
   This precludes RSVP's hop-by-hop integrity and authentication model.
   In the case, when the same level of security provided by [RFC2747] is
   desired, the standard IPsec based integrity and authentication can be
   used as explained in [RFC3473].

   To prevent the consequences of poorly applied protection and the
   increased risk of misconnection, in particular, when extra-traffic is
   involved, that would deliver the wrong traffic to the wrong
   destination, specific mechanisms have been put in place as described
   in Section 7.2, 8.3, and 10.

19.  IANA Considerations

   IANA assigns values to RSVP protocol parameters.  Within the current
   document, a PROTECTION object (new C-Type), a PRIMARY_PATH_ROUTE
   object, and an ASSOCIATION object are defined.  In addition, new
   Error code/sub-code values are defined in this document.  Finally,
   registration of the ADMIN_STATUS object bits is requested.

   Two RSVP Class Numbers (Class-Num) and three Class Types (C-Types)
   values have to be defined by IANA in registry:

   http://www.iana.org/assignments/rsvp-parameters

   1) PROTECTION object (defined in Section 14.1)

   o PROTECTION object: Class-Num = 37

   - Type 2: C-Type = 2

   2) PRIMARY_PATH_ROUTE object (defined in Section 15.1)

   o PRIMARY_PATH_ROUTE object: Class-Num = 38 (of the form 0bbbbbbb),

   - Primary Path Route: C-Type = 1

   3) ASSOCIATION object (defined in Section 16.1)

   o ASSOCIATION object: Class-Num = 199 (of the form 11bbbbbb)

   - IPv4 Association: C-Type = 1
   - IPv6 Association: C-Type = 2

   o Association Type

   The following values defined for the Association Type (16 bits) field
   of the ASSOCIATION object.

            Value       Type
            -----       ----
              0         Reserved
              1         Recovery (R)

   Assignment of values (from 2 to 65535) by IANA are subject to IETF
   expert review process, i.e., IETF Standards Track RFC Action.

   4) Error Code/Sub-code values

   The following Error code/sub-code values are defined in this
   document:

   Error Code = 01: "Admission Control Failure" (see [RFC2205])

   o "Admission Control Failure/LSP Admission Failure" (4)
   o "Admission Control Failure/Bad Association Type" (5)

   Error Code = 02: "Policy Control Failure" (see [RFC2205])

   o "Policy Control failure/Hard Pre-empted" (20)

   Error Code = 24: "Routing Problem" (see [RFC3209])

   o "Routing Problem/Unsupported LSP Protection" (17)
   o "Routing Problem/PROTECTION object not applicable" (18)
   o "Routing Problem/Bad PRIMARY_PATH_ROUTE object" (19)
   o "Routing Problem/PRIMARY_PATH_ROUTE object not applicable" (20)

   Error Code = 25: "Notify Error" (see [RFC3209])

   o "Notify Error/LSP Failure"               (9)
   o "Notify Error/LSP Recovered"             (10)
   o "Notify Error/LSP Locally Failed"        (11)

   5) Registration of the ADMIN_STATUS object bits

   The ADMIN_STATUS object (Class-Num = 196, C-Type = 1) is defined in
   [RFC3473].

   IANA is also requested to track the ADMIN_STATUS bits extended by
   this document.  For this purpose, the following new registry entries
   have been created:

   http://www.iana.org/assignments/gmpls-sig-parameters

   - ADMIN_STATUS bits:

        Name: ADMIN_STATUS bits
        Format: 32-bit vector of bits
        Position:
           [0]          Reflect (R) bit defined in [RFC3471]
           [1..25]      To be assigned by IANA via IETF Standards
                        Track RFC Action.
           [26]         Lockout (L) bit is defined in Section 13
           [27]         Inhibit alarm communication (I) in [RFC4783]

           [28]         Call control (C) bit is defined in
                        [GMPLS-CALL]
           [29]         Testing (T) bit is defined in [RFC3471]
           [30]         Administratively down (A) bit is defined in
                        [RFC3471]
           [31]         Deletion in progress (D) bit is defined in
                        [RFC3471]

20.  Acknowledgments

   The authors would like to thank John Drake for his active
   collaboration, Adrian Farrel for his contribution to this document
   (in particular, to the Section 10 and 11) and his thorough review of
   the document, Bart Rousseau (for editorial review), Dominique
   Verchere, and Stefaan De Cnodder.  Thanks also to Ichiro Inoue for
   his valuable comments.

   The authors would also like to thank Lou Berger for the time and
   effort he spent together with the design team, in contributing to the
   present document.

21.  References

21.1.  Normative References

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

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

   [RFC2747]    Baker, F., Lindell, B., and M. Talwar, "RSVP
                Cryptographic Authentication", RFC 2747, January 2000.

   [RFC2961]    Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
                and S. Molendini, "RSVP Refresh Overhead Reduction
                Extensions", RFC 2961, April 2001.

   [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.

   [RFC3471]    Berger, L., "Generalized Multi-Protocol Label Switching
                (GMPLS) Signaling Functional Description", RFC 3471,
                January 2003.

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

   [RFC3477]    Kompella, K. and Y. Rekhter, "Signalling Unnumbered
                Links in Resource ReSerVation Protocol - Traffic
                Engineering (RSVP-TE)", RFC 3477, January 2003.

   [RFC3945]    Mannie, E., "Generalized Multi-Protocol Label Switching
                (GMPLS) Architecture", RFC 3945, October 2004.

   [RFC4426]    Lang, J., Rajagopalan, B., and D. Papadimitriou,
                "Generalized Multi-Protocol Label Switching (GMPLS)
                Recovery Functional Specification", RFC 4426, March
                2006.

   [RFC4873]    Berger, L., Bryskin, I., Papdimitriou, D., and A.
                Farrel, "GMPLS Segment Recovery," RFC 4873, May 2007.

21.2.  Informative References

   [RFC4783]    Berger, L., "GMPLS - Communication of Alarm
                Information", RFC 4783, December 2006.

   [CRANK]      Farrel, A., Ed., "Crankback Signaling Extensions for
                MPLS and GMPLS RSVP-TE",  Work in Progress, January
                2007.

   [GMPLS-CALL] Papadimitriou, D., Ed., and A. Farrel, Ed., "Generalized
                MPLS (GMPLS) RSVP-TE Signaling Extensions in support of
                Calls",  Work in Progress, January 2007.

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

   [RFC4427]    Mannie, E., Ed., and D. Papadimitriou, Ed., "Recovery
                (Protection and Restoration) Terminology for Generalized
                Multi-Protocol Label Switching (GMPLS)", RFC 4427, March
                2006.

   [RFC4874]    Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes
                - Extension to Resource ReserVation Protocol-Traffic
                Engineering (RSVP-TE)", RFC 4874, April 2007.

   [G.841]      ITU-T, "Types and Characteristics of SDH Network
                Protection Architectures," Recommendation G.841, October
                1998, available from http://www.itu.int.

22.  Contributors

   This document is the result of the CCAMP Working Group Protection and
   Restoration design team joint effort.  The following are the authors
   that contributed to the present document:

   Deborah Brungard (AT&T)
   Rm. D1-3C22 - 200, S. Laurel Ave.
   Middletown, NJ 07748, USA
   EMail: dbrungard@att.com

   Sudheer Dharanikota
   EMail: sudheer@ieee.org

   Guangzhi Li (AT&T)
   180 Park Avenue
   Florham Park, NJ 07932, USA
   EMail: gli@research.att.com

   Eric Mannie (Perceval)
   Rue Tenbosch, 9
   1000 Brussels, Belgium
   Phone: +32-2-6409194
   EMail: eric.mannie@perceval.net

   Bala Rajagopalan (Intel Broadband Wireless Division)
   2111 NE 25th Ave.
   Hillsboro, OR 97124, USA
   EMail: bala.rajagopalan@intel.com

Editors' Addresses

   Jonathan P. Lang
   Sonos
   506 Chapala Street
   Santa Barbara, CA 93101, USA

   EMail: jplang@ieee.org

   Yakov Rekhter
   Juniper
   1194 N. Mathilda Avenue
   Sunnyvale, CA 94089, USA

   EMail: yakov@juniper.net

   Dimitri Papadimitriou
   Alcatel
   Copernicuslaan 50
   B-2018, Antwerpen, Belgium

   EMail: dimitri.papadimitriou@alcatel-lucent.be

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