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Versions: (draft-aruns-ccamp-rsvp-restart-ext) 00 01 02 03 04 05 06 07 08 09 RFC 5063

Network Working Group                   A. Satyanarayana (Cisco Systems)
Internet Draft                                 R. Rahman (Cisco Systems)
Expiration Date: September 2005                                  Editors

                                                              March 2005


               Extensions to GMPLS RSVP Graceful Restart


                draft-ietf-ccamp-rsvp-restart-ext-02.txt

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   or will be disclosed, and any of which I become aware will be
   disclosed, in accordance with RFC 3668.

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

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

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

Abstract

   This document describes extensions to the RSVP Graceful Restart
   mechanisms defined in RFC 3473.  The extensions enable the recovery
   of RSVP signaling state based on the Path message last sent by the
   node being restarted.  Previously defined Graceful Restart
   mechanisms, also called recovery from nodal faults, permit recovery
   of signaling state from adjacent nodes when the data plane has
   retained the associated forwarding state across a restart.  These
   mechanisms do not fully support signaling state recovery on ingress
   nodes or recovery of all RSVP objects.  The presented extensions use
   the RSVP Hello extensions defined in RFC 3209, and extensions for
   state recovery on nodal faults defined in RFC 3473.  With the
   presented extensions the restarting node can recover all previously
   transmitted Path state including the ERO and the downstream
   (outgoing) interface identifiers.  The extensions can also be used to
   recover signaling state after the restart of an ingress node.  The
   extensions optionally support the use of Summary Refresh, defined in
   RFC 2961, to reduce the number of messages exchanged during the



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   Recovery Phase when the restarting node has recovered signaling state
   locally for one or more LSP's.



Contents

 1      Introduction  ..............................................   3
 2      Extensions to Nodal Fault Handling  ........................   5
 2.1    RecoveryPath Message Format  ...............................   5
 2.2    Related Procedures  ........................................   5
 2.3    Procedures For The Downstream Neighbor  ....................   6
 2.4    Procedures for the Restarting Node  ........................   7
 2.4.1  Path and RecoveryPath Message Procedures  ..................   7
 2.4.2  Re-Synchronization Procedures  .............................   8
 2.4.3  Procedures on Expiration of Recovery Period  ...............   9
 2.5    Compatibility  .............................................   9
 3      RecoveryPath Summary Refresh  ..............................  10
 3.1    MESSAGE_ID ACK/NACK and MESSAGE_ID LIST Objects  ...........  11
 3.2    Capability Object  .........................................  12
 3.2.1  Procedures  ................................................  13
 3.2.2  Compatibility  .............................................  13
 3.3    RecoveryPath Summary Refresh Procedures  ...................  14
 3.3.1  Generation of RecoveryPath-related Srefresh Messages  ......  14
 3.3.2  RecoveryPath-related Srefresh Receive Processing and NACK
        Generation  ................................................  15
 3.3.3  RecoveryPath-related MESSAGE_ID NACK Receive Processing  ...  16
 4      Acknowledgments  ...........................................  17
 5      Security Considerations  ...................................  17
 6      IANA Considerations  .......................................  17
 7      References  ................................................  17
 7.1    Normative References  ......................................  17
 7.2    Informative References  ....................................  18
 8      Authors' Addresses  ........................................  18
 9      Intellectual Property Considerations  ......................  19
10      Disclaimer of Validity  ....................................  20
11      Full Copyright Statement  ..................................  20














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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 RFC 2119 [RFC2119].


1. Introduction

   RSVP Graceful Restart is defined in [RFC3473] and uses mechanisms
   defined in [RFC3209].  [RFC3209] describes a mechanism, using RSVP
   Hello messages, to detect the state of an adjacent RSVP agent.
   [RFC3473] extends this mechanism to advertise the capability of
   retaining data / forwarding plane state across the restart of a node
   or a "nodal fault".  [RFC3473] also defines the Recovery Label object
   for use in the Path message of the RSVP neighbor upstream of a
   restarting node, to indicate that the Path message is for existing
   data plane state.

   This document presents extensions to address two aspects of graceful
   restart not previously supported.  The presented extensions enable a
   restarting node to recover all objects in previously transmitted Path
   messages including the ERO, from its downstream neighbors.  The
   extensions also enable graceful restart of an ingress node that does
   not preserve full RSVP state across restarts.

   Per [RFC3473], a restarting node can distinguish Path messages
   associated with LSPs being recovered by the presence of the Recovery
   Label object.  To determine the downstream (outgoing) interface and
   associated label(s), the restarting node must consult the data plane.
   This may not be possible for all types of nodes.  Furthermore, data
   plane information is not sufficient to reconstruct all previously
   transmitted Path state.  In these cases, the only source of RSVP
   state is the downstream RSVP neighbor.

   For example, when the restarting node is an ingress node, all
   previously transmitted Path state may need to be recovered.  Such
   Path state may include (but is not restricted to) the Protection
   object, the Admin Status object, the Session Attribute object, the
   Notify Request object, the Sender Tspec object.  A restarting transit
   node may have modified received Path state in its previously
   transmitted Path message, which cannot be reconstructed internally
   during recovery.

   Another example of state that cannot be completely recovered from the
   data plane in some cases is the previously transmitted ERO.  Recovery
   of the previously transmitted ERO minimizes subsequent change of
   downstream LSP state.  On a restarting ingress node, the ERO may have



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   been based on configuration or the result of a previous path
   computation.  A restarting transit node may have previously performed
   some form of path computation as a result of not receiving an ERO or
   receiving a loose hop in the ERO.  In addition to the ERO, the
   restarting node may have modified other received Path state in its
   previously transmitted Path state, which cannot be reconstructed
   internally during recovery.

   The defined extensions provide a restarting upstream node with all
   information previously transmitted by the node in Path messages.
   This is accomplished by the downstream RSVP neighbor, after
   reestablishing RSVP communication with the restarted node, sending a
   new message for every Path message it has previously received from
   the restarting node.

   The new message is called the RecoveryPath message.  The message
   conveys the contents of the last received Path message back to the
   restarting node.  The restarting node can use the RecoveryPath
   message along with the state in the received Path message to
   associate control and data plane state and to validate the forwarding
   state with the state presented by the neighboring RSVP nodes.

   If the restarting node is a transit node, it will receive a Path
   message with a Recovery Label object from its upstream RSVP neighbor.
   In addition, the RecoveryPath message allows such transit nodes to
   reconstruct any state that was previously dynamically constructed by
   the node, e.g., ERO sub-objects.  If the restarting node is an
   ingress node, all significant signaling state can be recovered based
   on the RecoveryPath message.

   Selective transmission of the RecoveryPath message is supported by
   enhancing the Summary Refresh mechanisms defined in [RFC2961].  When
   Recovery Summary Refresh is supported, the restarting node can select
   the LSP's for which it would like to receive RecoveryPath messages.
   This is useful when the restarting node is able to locally recover
   the signaling state for a subset of the previously active LSP's.

   Restarting egress nodes, and Resv message processing are not impacted
   by the presented extensions, see [RFC3473] for details.












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2. Extensions to Nodal Fault Handling

   This section presents the protocol modifications to Section 9 of
   [RFC3473].


2.1. RecoveryPath Message Format

   The format of a RecoveryPath message is the same as the format of a
   Path message as defined in [RFC3473]:

      <RecoveryPath Message> ::= <Path Message>

   The destination address used in the IP header of a RecoveryPath
   message MUST be the same as the destination address used in the IP
   header of the corresponding Resv message last generated by the
   sending node.  Except as specified below all objects in a
   RecoveryPath message are identical to the objects in the
   corresponding Path message last received by the sending node.


2.2. Related Procedures

   This document does not modify existing procedures for sending and
   receiving RSVP Hello messages as defined in [RFC3209] and the
   Restart_Caps object in RSVP Hello messages as defined in [RFC3473].
   The procedures for control channel faults are defined in [RFC3473]
   and are not changed by this document.

   The presented extensions require the use of RSVP Hellos as defined in
   [RFC3209] and the use of the Restart_Caps object extension as defined
   in [RFC3473].  The presented extensions address only "Nodal Faults"
   as defined in [RFC3473].  Control channel faults are fully addressed
   in [RFC3473].

   Note: There are no changes to the procedures defined in Section 9.5.3
   in [RFC3473] (Procedures for the Neighbor of a Restarting node).
   There are no changes to the procedures defined in Section 9.5.2 in
   [RFC3473] if the restarting node is an egress node.

   The following sections assume previously defined procedures are
   followed, except where explicitly modified.









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2.3. Procedures For The Downstream Neighbor

   After a downstream RSVP neighbor has detected that its upstream node
   has restarted and is capable of recovery as defined in [RFC3473], the
   downstream RSVP neighbor MUST send a RecoveryPath message for each
   LSP associated with the restarting node for which it has sent a Resv
   message.

   The RecoveryPath message is constructed by copying all objects from
   the last received associated Path message, with the following
   exceptions:

      The MESSAGE_ID, MESSAGE_ID_ACK and MESSAGE_ID_NACK objects are not
      copied.  Any MESSAGE_ID, MESSAGE_ID_ACK and MESSAGE_ID_NACK
      objects used in RecoveryPath messages are generated based on
      procedures defined in [RFC2961].

      The Integrity object is not copied.  Any Integrity objects used in
      RecoveryPath messages are generated based on procedures defined in
      [RFC2747].

      The RSVP Hop object is copied from the most recent associated Resv
      message sent to the restarted node, for the LSP being recovered.

      In the sender descriptor, the Recovery Label object MUST be
      included, with the label value copied from the label value in the
      Label object in the most recent associated Resv message sent to
      the restarted node, for the LSP being recovered.

   All other objects from the most recent received Path message MUST be
   included in the RecoveryPath message.

   All RecoveryPath messages SHOULD be sent within approximately 1/2 of
   the Recovery Time advertised by the restarted neighbor.  If there are
   many LSP's to be recovered by the restarted node, the downstream RSVP
   neighbor should avoid sending RecoveryPath messages in a short time
   interval, to avoid overloading the restarted node's CPU.  Instead it
   should spread the messages across 1/2 the Recovery Time interval.

   After sending a RecoveryPath message and during the Recovery Period,
   the node SHOULD periodically re-send the RecoveryPath message until
   it receives a corresponding response.  A corresponding response is a
   Message ID acknowledgment or a Path message for the LSP the
   RecoveryPath message represents.  Each such re-send attempt is at the
   end of any Message ID rapid retransmissions, if the Message ID
   mechanism is used.  If the Message ID mechanim is not in use, the
   period between re-send attempts SHOULD be such that at least 3
   attempts are completed before the expiry of 1/2 the Recovery Time



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   interval.  Each such re-send attempt MUST treat the RecoveryPath
   message as a new message, and update the MESSAGE_ID object according
   to procedures defined in [RFC2961].  Note, per [RFC3473], Resv
   messages are suppressed during this recovery period until a
   corresponding Path message is received.


2.4. Procedures for the Restarting Node

   These procedures apply during the "state recovery process" and
   "Recovery Period" as defined in Section 9.5.2 in [RFC3473].  Any
   RecoveryPath message received after the Recovery Period has expired
   MUST be discarded.  If no LSP state matching the RecoveryPath message
   is located, the restarted node MAY send a PathTear message
   constructed from the RecoveryPath message, to expedite the cleanup of
   unrecovered RSVP and associated forwarding state downstream of the
   restarted node.

   The remaining procedures are broken down into three sub-sections.
   The term "resynchronized state", originally defined in [RFC3473], is
   used and modified in these sections.  This term refers to LSP state
   that is fully recovered.

   Signaling state may be recovered from sources other than the
   mechanisms defined in this document.  The restarting node SHOULD
   consider signaling state as resynchronized for all such LSPs and
   follow corresponding procedures defined below.  Further, recovery
   procedures defined below may be overridden by local policy.

   Again, there are no changes to the procedures defined in Section
   9.5.2 in [RFC3473] if the restarting node is an egress node.


2.4.1. Path and RecoveryPath Message Procedures

   When a node receives a RecoveryPath message during the Recovery
   Period, the node first checks if it has resynchronized RSVP state
   associated with the message.  If there is resynchronized state, and
   when both reliable message delivery [RFC2961] is supported and a
   MESSAGE_ID object is present in the RecoveryPath message, the node
   MUST follow Message ID acknowledgment procedures as defined in
   [RFC2961], and, consider the message as processed. If there is
   resynchronized state, and, there is no MESSAGE_ID object or reliable
   message delivery [RFC2961] is not supported, the node SHOULD send a
   triggered Path message, and, consider the message as processed.

   If non-resynchronized state is found or the node is the ingress, the
   node saves the information contained in the RecoveryPath message and



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   continues with processing as defined in Section 2.4.2.

   If no associated RSVP state is found and the node is not the ingress
   node, the node saves the information contained in the RecoveryPath
   message for later use.

   Note the following modifies Section 9.5.2 of [RFC3473]:

   When a node receives a Path message during the Recovery Period, the
   node first locates any RSVP state associated with the message.  If
   resynchronized RSVP state is found, then the node handles this
   message according to previously defined procedures.

   If non-resynchronized state is found, the node saves the information
   contained in the Path message including the Recovery_Label object and
   continues with processing as defined in Section 2.4.2.

   Per [RFC3473], if matching RSVP state is not found, and the message
   does not carry a Recovery_Label object, the node treats this as a
   setup for a new LSP, and handles it according to previously defined
   procedures.

   If matching RSVP state is not found, and the message carries a
   Recovery_Label object, the node saves the information contained in
   the Path message including the Recovery_Label object for later use.


2.4.2. Re-Synchronization Procedures

   After receipt of the RecoveryPath message and, for non-ingress LSPs,
   the corresponding Path message with a Recovery Label object, the
   restarting node SHOULD locate and associate corresponding forwarding
   state using the received information.  The restarting node associates
   the corresponding active forwarding plane state from the following
   signaled information:

      The upstream data interface is recovered from the RSVP HOP object
      in the received Path message.

      The label on the upstream data interface is recovered from the
      Recovery Label object in the received Path message.  If the LSP is
      bidirectional, the label for the upstream direction is recovered
      from the Upstream Label object in the received Path message.

      The downstream data interface is recovered from the RSVP HOP
      object in the received RecoveryPath message.

      The label on the downstream data interface is recovered from the



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      Recovery Label object in the received RecoveryPath message.  If
      the LSP is bidirectional, the label for the upstream direction is
      recovered from the Upstream Label object in the RecoveryPath
      message.

   If complete forwarding state is located, the restarted node MUST
   treat the LSP as resynchronized and MUST send a triggered Path
   message downstream.  The Explicit Route object in the Path message
   SHOULD match the Explicit Route object received in the RecoveryPath
   message.  In addition, the restarted node SHOULD recover state from
   the other objects received in the RecoveryPath message.  Optimally
   the resulting Path message should not cause any redundant or
   unnecessary re-processing of state along the remaining downstream
   nodes.  Ideally, except for MESSAGE_ID processing and recovery
   processing, the transmitted Path message will be treated as a refresh
   by the downstream RSVP neighbor (and hence should not trigger any
   generation of Path messages with changed state further downstream).

   If no forwarding state is located, the node treats the path message
   as a setup for a new LSP.  The outgoing interface and label(s)
   indicated in the RecoveryPath message SHOULD be reused, when
   possible.  All other information contained in the RecoveryPath
   message MAY also be used.


2.4.3. Procedures on Expiration of Recovery Period

   There are several cleanup steps to follow at the end of the Recovery
   Period.  At the end of the Recovery Period, any state that was
   installed as the result of a received RecoveryPath message that is
   not resynchronized SHOULD be discarded.

   Any Path messages that were received containing a Recovery_Label that
   have not been resynchronized, SHOULD be treated as being received
   during the Recovery Period and processed as per [RFC3473].

   Per [RFC3473], any other state that is not resynchronized during the
   Recovery Period SHOULD be removed at the end of the Period.


2.5. Compatibility

   This document introduces a new RSVP signaling message to be generated
   by the downstream RSVP neighbor of a restarting node.

   If the restarting node does not support the RecoveryPath message and
   associated procedures, it will discard all received RecoveryPath
   messages, and revert to recovery processing as defined in [RFC3473].



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   If the downstream RSVP neighbor does not support the RecoveryPath
   message and associated procedures, the restarting node processes
   received Path messages as defined in Section 2.4.3, which essentially
   reverts to the processing defined in [RFC3473].


3. RecoveryPath Summary Refresh

   This section describes a mechanism to control which LSP state is
   communicated in RecoveryPath messages.  This mechanism enhances the
   Summary Refresh mechanism defined in [RFC2961], and uses a new object
   carried in the Hello message defined in [RFC3209] and [RFC3473].  The
   described mechanism is referred to as RecoveryPath Summary Refresh.

   Selective transmission of RecoveryPath messages is controlled much
   the same way transmission of Path or Resv messages is controlled with
   standard Summary Refresh, see [RFC2961].  In standard Summary
   Refresh, an Srefresh message is sent by a node to identify to its
   neighbor about Path and Resv state that is locally installed and
   available.  The receiver of the Srefresh message, can then attempt to
   locate matching Path and Resv state. If no matching state is found,
   the receiver can request that the missing state be sent to it, by
   sending an Srefresh NACK to the sender of the Srefresh message.  When
   the Srefresh NACK is received, the corresponding Path or Resv message
   is sent.  MESSAGE_ID information is used to identify Path and Resv
   state in this process.

   The mechanism described in this section extends the Summary Refresh
   process to the Path state that can be represented in RecoveryPath
   messages.  In this case, the Srefresh messages represent previously
   received Path messages, rather than previously transmitted Path
   messages.  This is the primary difference between standard Summary
   Refresh and RecoveryPath Summary Refresh described in this section.

   When a node restarts, and is capable of supporting the mechanisms
   described in this section, it includes a new object in Hello messages
   it sends to its RSVP neighbors.  The new object is defined below in
   Section 3.2 and is called the Capability object.  A bit carried
   within the Capability object indicates when a restarting node desires
   its downstream neighbor to use the mechanisms described in this
   section.  This bit is called the RecoveryPath Srefresh Capable bit.

   When a neighbor of the restarting node detects a restart, see
   [RFC3209], it detects that the restarted node is requesting
   RecoveryPath Srefresh messages by the presence of the Capability
   object with the RecoveryPath Srefresh Capable bit set.  When such an
   indication is found, the neighbor generates one or more Srefresh
   messages.  Each message indicates the Path state that can be



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   represented in a RecoveryPath message.  Within such Srefresh
   messages, Path state that can be represented in RecoveryPath messages
   is represented using MESSAGE_ID information, and this information is
   communicated within MESSAGE_ID LIST objects.  To indicate that the
   MESSAGE_ID LIST object is for recovery purposes, a new flag is set in
   the MESSAGE_ID LIST object.  This flag is called the RecoveryPath
   Flag and is defined below.

   The restarted node can then use the Srefresh message and the
   MESSAGE_ID LIST object to try to identify matching transmitted Path
   state.  The node identifies local state by matching Epoch and Message
   ID tuples against Path messages transmitted downstream prior to the
   restart.

   If matching state is located, then the restarted node operates as if
   a RecoveryPath message has been received, per Section 2.4.  If no
   matching state can be located, the restarted node generates a
   Srefresh NACK, see Section 5.4 of [RFC2961].  The Srefresh NACK is
   also marked with the new RecoveryPath Flag to indicate that the NACK
   is related to RecoveryPath messages.

   Upon receiving a Srefresh NACK, the downstream node generates a
   RecoveryPath message for the Path state indicated by each entry in
   the MESSAGE_ID LIST.  The procedures defined above in Section 2 are
   then followed by the restarted node and the downstream RSVP neighbor.


3.1. MESSAGE_ID ACK/NACK and MESSAGE_ID LIST Objects

   The MESSAGE_ID ACK/NACK objects and the MESSAGE_ID LIST object,
   defined in [RFC2961], are updated by this document.  A new bit within
   the existing Flags field of each object is defined.  This bit
   indicates that the object carries MESSAGE_ID information related to
   Path state that can be recovered using RecoveryPath messages.  The
   same flag value is used in all the objects for consistency.
















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   MESSAGE_ID_ACK object
   MESSAGE_ID_NACK object

      See Section 4.3 of [RFC2961] for definition of other fields.

   MESSAGE_ID LIST object

      See Section 5.1 of [RFC2961] for definition of other fields.

      Flags: 8 bits

         0x02: RecoveryPath Flag

            Indicates that the associated object carries MESSAGE_ID
            information related to one or more Path messages that can be
            recovered using a RecoveryPath message.


3.2. Capability Object

   Capability objects are carried in RSVP Hello messages.  The
   Capability object uses Class-Number TBA (of form 10bbbbbb) and C-Type
   of 1.

   The message format of a Hello message is modified to be:

   <Hello Message> ::= <Common Header> [ <INTEGRITY> ] <HELLO>
                       [ <RESTART_CAP> ] [ <CAPABILITY> ]

   The format of a Capability object is:

    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(TBA)|  C-Type  (1)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Reserved                            |R|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+













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      RecoveryPath Srefresh Capable (R): 1 bit

         When set (1), indicates that the sending node is capable of
         receiving and processing Srefresh messages with the
         RecoveryPath Flag set (1) in the MESSAGE_ID LIST object.
         Absence of the Capability object MUST be treated as if the
         R-bit is cleared (0).

      Reserved bits

         Reserved bits MUST be set to zero on transmission and MUST be
         ignored on receipt.


3.2.1. Procedures

   The Capability object is sent within a Hello message to indicate that
   a node supports selective transmission of RecoveryPath messages.  To
   indicate to a neighbor that selective transmission of RecoveryPath
   messages is desired, a restarting node MUST include the Capability
   object with the R-bit set (1) in all Hello messages it sends during
   the Recovery Period to the neighbor.  When either the Restart_Cap
   Object is not present in a Hello message or when the Recovery Time is
   zero (0), the Capability object MUST be omitted or the R-bit MUST be
   cleared (0).

   On the downstream neighbor, the R-bit is checked upon detecting a
   restart of a neighbor that supports state recovery.  Detection of
   neighbor restarts with state recovery is defined in [RFC3473].  When
   a node supports RecoveryPath Summary Refresh, and it detects a
   restart of a neighbor that supports state recovery, it MUST check to
   see if the received Hello message contains a Capability object with
   the R-bit set.  If the R-bit is set, then the procedures defined
   below in Section 3.3.1 MUST be followed.  If the Capability object is
   not found or the R-bit not set, then the node MUST revert to normal
   recovery procedures as defined above in Section 2.3.


3.2.2. Compatibility

   There are no compatibility issues introduced in this section.  The
   use of the Capability object will not cause any issues on a
   non-supporting receiver as it uses a Class-Number of form 10bbbbbb.
   The object will simply be ignored, and normal processing will
   continue. Normal processing includes procedures defined above in
   Section 2, in [RFC3473] and in [RFC3209].

   The sender of the Capability object will detect that its neighbor



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   does not support selective transmission of RecoveryPath messages when
   a RecoveryPath message is received prior to the receipt of a Srefresh
   message containing a MESSAGE_ID LIST object with the RecoveryPath
   Flag set (1).  When this occurs, any received RecoveryPath messages
   MUST be processed as defined above in Section 2.


3.3. RecoveryPath Summary Refresh Procedures

   Related processing occurs in the following logical order:

      o  Generation of RecoveryPath-related Srefresh messages
      o  RecoveryPath-related Srefresh message receive processing and
         NACK generation
      o  Message ID NACK receive processing and generation of
         RecoveryPath messages
      o  Receive processing of RecoveryPath messages

   Actual processing MAY result in the above occurring in an interlaced
   fashion when multiple LSP's are being recovered.  Both the restarted
   node and the downstream RSVP neighbor MUST be able to process in this
   fashion.


3.3.1. Generation of RecoveryPath-related Srefresh Messages

   A neighbor of a restarting node generates one or more
   RecoveryPath-related Srefresh messages when the R-bit is set in the
   restarted node's Hello messages as described above in Section 3.2.1.
   The procedures for generating an Srefresh message are defined in
   [RFC2961].  Only modifications to these procedures are described in
   this section.

   To generate RecoveryPath-related Srefresh messages, a node must
   identify which Path state can be represented in RecoveryPath messages
   and which Srefresh message or messages can be used to carry the
   related information.  As previously mentioned, the Path state that
   can be represented in RecoveryPath messages is indicated in Srefresh
   messages using the MESSAGE_ID information from the most recently
   received Path message associated with the state.

   After processing the R-bit as described in Section 3.2.1, the node
   identifies all state associated with Path messages received from the
   restarted neighbor.  Only Path state that has not been updated since
   the restart may be represented in the Srefresh messages.  Received
   Path state containing a MESSAGE_ID object whose Epoch value matches
   the Epoch received in the most recent Hello message is considered as
   updated after the upstream neighbor has restarted.  Such Path state



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   MUST NOT be represented in the Srefresh messages.

   Each Srefresh message contains one or more MESSAGE_ID LIST objects.
   Each such MESSAGE_ID LIST object MUST have the RecoveryPath Flag set
   (1).  Multiple MESSAGE_ID LIST objects MAY be included in order to
   accommodate multiple Epoch values.  The MESSAGE_ID LIST objects
   represent the identified, non-updated, Path state.  A
   Message_Identifier field created for each identified, non-updated
   Path state MUST be included in an appropriate MESSAGE_ID LIST object.
   The Message_Identifier field is created based on the MESSAGE_ID
   object from the most recently received Path message associated with
   identified Path state.  If any identified Path state does not have an
   associated MESSAGE_ID object, this state MUST be processed as defined
   above in Section 2.3.

   The source IP address for the Srefresh message SHOULD be the source
   IP address in the IP header of the corresponding Resv messages
   previously sent to the restarted node.  The Srefresh message SHOULD
   be destined to the IP address in the HOP object in the corresponding
   Path messages.  This may result in multiple Srefresh messages being
   generated.  Per [RFC2961], implementations may choose to limit each
   Srefresh message to the MTU size of the outgoing link, and to not
   bundle Srefresh messages.  RecoveryPath-related Srefresh messages
   SHOULD be sent using reliable delivery, as defined in [RFC2961].

   During the Recovery Period, unacknowledged RecoveryPath-related
   Srefresh messages SHOULD be periodically transmitted.  The
   retransmission algorithm used can be same algorithm used for
   retransmitting RecoveryPath messages during the Recovery Period (see
   section 2.3).  Note that prior to each such periodic retransmission,
   the Srefresh message SHOULD be updated to exclude the Message ID's of
   Path state that has been updated by the receipt of a Path message.

   To allow sufficient processing time for the restarted node, the
   downstream RSVP neighbor MAY choose to generate multiple
   RecoveryPath-related Srefresh messages containing partial but
   mutually exclusive sets of Message Identifiers spread across 1/4 of
   the Recovery Time advertised by the restarted node.


3.3.2. RecoveryPath-related Srefresh Receive Processing and NACK
   Generation

   Upon receiving an Srefresh message containing a MESSAGE_ID LIST
   object with the RecoveryPath Flag set), the restarted node attempts
   to locate matching previously transmitted Path state.  The Epoch in
   the MESSAGE_ID LIST object along with each Message Identifier in the
   object is used to match against the MESSAGE_ID object in Path



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   messages previously transmitted to the downstream RSVP neighbor.  For
   each Message Identifier in the MESSAGE_ID LIST:

      If matching transmitted Path state is found, the restarting node
      treats the corresponding LSP state as having received and
      processed a RecoveryPath message, and, perform any further
      processing necessary as defined in Section 2.4.  Specifically, it
      MUST generate a triggered Path message for the LSP as defined in
      Section 2.4.2.  The restarted node MAY spread the transmission of
      such triggered Path messages across 1/2 of the remaining Recovery
      Period to allow the downstream RSVP neighbor sufficient processing
      time.

      If matching transmitted Path state is not found, the restarting
      node MUST generate a MESSAGE_ID NACK as defined in [RFC2961].
      Each generated MESSAGE_ID NACK MUST have the RecoveryPath Flag set
      (1).

   It is recommended that the restarted node combine multiple such
   MESSAGE_ID NACK's into a single ACK message, per [RFC2961].


3.3.3. RecoveryPath-related MESSAGE_ID NACK Receive Processing

   This section defines the procedures associated with the processing of
   received MESSAGE_ID NACK's which have the RecoveryPath Flag set (1).
   Procedures for processing of MESSAGE_ID NACK's without the
   RecoveryPath Flag present are defined in [RFC2961] and not modified
   in this document.  Processing of MESSAGE_ID NACK's with the
   RecoveryPath Flag set (1) also follows procedures defined in
   [RFC2961] unless explicitly modified in this section.

   For each MESSAGE_ID NACK with the RecoveryPath Flag set (1), the
   downstream RSVP neighbor must locate the matching received Path
   message.  If a matching Path message is found, the downstream RSVP
   neighbor MUST generate a RecoveryPath message as defined in Section
   2.3.  If a matching Path message is not found, the MESSAGE_ID NACK is
   ignored.  An example where this may occur is when the restarted node
   has already generated an updated Path message after its restart.












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4. Acknowledgments

   The authors would like to thank participants of the CCAMP WG for
   comments and suggestions.  Also thanks to Arthi Ayyangar, Adrian
   Farrel and Nick Neate for their helpful comments and feedback.


5. Security Considerations

   This document introduces a new RSVP message that is restricted to one
   RSVP hop.  This document introduces no new security considerations
   beyond those already addressed for existing RSVP hop-by-hop messages.

   This document introduces a new RSVP object to be included in RSVP
   Hello messages.  This document introduces no new security
   considerations beyond those already addressed for existing objects in
   RSVP Hello messages.


6. IANA Considerations

   A new RSVP message type is defined in this document.  The RSVP
   message type is TBA by IANA.

   A new RSVP object of form 10bbbbbb is defined in this document.  The
   Class-Num is TBA by IANA.


7. References

7.1. Normative References

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

   [RFC2205] "Resource ReSerVation Protocol (RSVP) - Version 1,
              Functional Specification",
              RFC 2205, Braden, et al, September 1997.

   [RFC2747] "RSVP Cryptographic Authentication",
              RFC 2747, F.  Baker, et al, January 2000.

   [RFC2961] "RSVP Refresh Overhead Reduction Extensions",
              RFC 2961, L.  Berger, et al, April 2001.

   [RFC3209] "Extensions to RSVP for LSP Tunnels", D.  Awduche, et al,
              RFC 3209, December 2001.




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

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


7.2. Informative References

   [RESTART] "RSVP Graceful Restart Extensions",
             draft-rahman-rsvp-restart-extensions-00,
             R. Rahman, et al, October 2003


8. Authors' Addresses

   Arun Satyanarayana
   Cisco Systems, Inc.
   170 West Tasman Dr.
   San Jose, CA 95134
   Phone:  +1 408 853-3206
   Email:  asatyana@cisco.com

   Lou Berger
   Movaz Networks, Inc.
   7926 Jones Branch Drive
   Suite 615
   McLean VA, 22102
   Phone:  +1 703 847-1801
   Email:  lberger@movaz.com

   Dimitri Papadimitriou (Alcatel)
   Francis Wellesplein 1
   B-2018 Antwerpen, Belgium
   Phone:  +32 3 240-8491
   Email:  dimitri.papadimitriou@alcatel.be

   Reshad Rahman
   Cisco Systems Inc.
   2000 Innovation Dr.,
   Kanata, Ontario, K2K 3E8
   Canada.
   Phone: (613)-254-3519
   Email: rrahman@cisco.com




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   Anca Zamfir
   Cisco Systems Inc.
   2000 Innovation Dr.,
   Kanata, Ontario, K2K 3E8
   Canada.
   Phone: (613)-254-3484
   Email: ancaz@cisco.com

   Junaid Israr
   Cisco Systems Inc.
   2000 Innovation Dr.,
   Kanata, Ontario, K2K 3E8
   Canada.
   Phone: (613)-254-3693
   Email: jisrar@cisco.com


9. Intellectual Property Considerations

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.











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10. Disclaimer of Validity

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


11. Full Copyright Statement

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.



































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