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Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions :: RFC3473








Network Working Group                                  L. Berger, Editor
Request for Comments: 3473                                Movaz Networks
Category: Standards Track                                   January 2003


     Generalized Multi-Protocol Label Switching (GMPLS) Signaling
 Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions

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 Internet Society (2003).  All Rights Reserved.

Abstract

   This document describes extensions to Multi-Protocol Label Switching
   (MPLS) Resource ReserVation Protocol - Traffic Engineering (RSVP-TE)
   signaling required to support Generalized MPLS.  Generalized MPLS
   extends the MPLS control plane to encompass time-division (e.g.,
   Synchronous Optical Network and Synchronous Digital Hierarchy,
   SONET/SDH), wavelength (optical lambdas) and spatial switching (e.g.,
   incoming port or fiber to outgoing port or fiber).  This document
   presents a RSVP-TE specific description of the extensions.  A generic
   functional description can be found in separate documents.

Table of Contents

   1.  Introduction  ..............................................   2
   2.  Label Related Formats   ....................................   3
    2.1  Generalized Label Request Object  ........................   3
    2.2  Bandwidth Encoding  ......................................   4
    2.3  Generalized Label Object  ................................   5
    2.4  Waveband Switching  ......................................   5
    2.5  Suggested Label  .........................................   6
    2.6  Label Set  ...............................................   7
   3.  Bidirectional LSPs  ........................................   8
    3.1  Procedures  ..............................................   9
    3.2  Contention Resolution  ...................................   9
   4.  Notification  ..............................................   9
    4.1  Acceptable Label Set Object  .............................  10
    4.2  Notify Request Objects  ..................................  10



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    4.3  Notify Message  ..........................................  12
    4.4  Removing State with a PathErr message  ...................  14
   5.  Explicit Label Control  ....................................  15
    5.1  Label ERO subobject  .....................................  15
    5.2  Label RRO subobject  .....................................  16
   6.  Protection Object  .........................................  17
    6.1  Procedures  ..............................................  18
   7.  Administrative Status Information  .........................  18
    7.1  Admin Status Object  .....................................  18
    7.2  Path and Resv Message Procedures  ........................  18
    7.3  Notify Message Procedures  ...............................  20
   8.  Control Channel Separation  ................................  21
    8.1  Interface Identification  ................................  21
    8.2  Errored Interface Identification  ........................  23
   9.  Fault Handling  ............................................  25
    9.1  Restart_Cap Object  ......................................  25
    9.2  Processing of Restart_Cap Object  ........................  26
    9.3  Modification to Hello Processing to Support
         State Recovery  ..........................................  26
    9.4  Control Channel Faults  ..................................  27
    9.5  Nodal Faults  ............................................  27
   10. RSVP Message Formats and Handling  .........................  30
    10.1  RSVP Message Formats  ...................................  30
    10.2  Addressing Path and PathTear Messages   .................  32
   11. Acknowledgments  ...........................................  32
   12. Security Considerations  ...................................  33
   13. IANA Considerations  .......................................  34
    13.1  IANA Assignments  .......................................  35
   14. Intellectual Property Considerations  ......................  36
   15. References  ................................................  37
    15.1  Normative References  ...................................  37
    15.2  Informative References  .................................  38
   16. Contributors  ..............................................  38
   17. Editor's Address  ..........................................  41
   18. Full Copyright Statement  ..................................  42

1. Introduction

   Generalized MPLS extends MPLS from supporting packet (PSC) interfaces
   and switching to include support of three new classes of interfaces
   and switching: Time-Division Multiplex (TDM), Lambda Switch (LSC) and
   Fiber-Switch (FSC).  A functional description of the extensions to
   MPLS signaling needed to support the new classes of interfaces and
   switching is provided in [RFC3471].  This document presents RSVP-TE
   specific formats and mechanisms needed to support all four classes of
   interfaces.





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   [RFC3471] should be viewed as a companion document to this document.
   The format of this document parallels [RFC3471].  In addition to the
   other features of Generalized MPLS, this document also defines RSVP-
   TE specific features to support rapid failure notification, see
   Sections 4.2 and 4.3.

   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].

2. Label Related Formats

   This section defines formats for a generalized label request, a
   generalized label, support for waveband switching, suggested label
   and label sets.

2.1. Generalized Label Request Object

   A Path message SHOULD contain as specific an LSP (Label Switched
   Path) Encoding Type as possible to allow the maximum flexibility in
   switching by transit LSRs.  A Generalized Label Request object is set
   by the ingress node, transparently passed by transit nodes, and used
   by the egress node.  The Switching Type field may also be updated
   hop-by-hop.

   The format of a Generalized Label Request 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 (19)|  C-Type (4)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | LSP Enc. Type |Switching Type |             G-PID             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.

2.1.1. Procedures

   A node processing a Path message containing a Generalized Label
   Request must verify that the requested parameters can be satisfied by
   the interface on which the incoming label is to be allocated, the
   node itself, and by the interface on which the traffic will be
   transmitted.  The node may either directly support the LSP or it may
   use a tunnel (FA), i.e., another class of switching.  In either case,
   each parameter must be checked.





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   Note that local node policy dictates when tunnels may be used and
   when they may be created.  Local policy may allow for tunnels to be
   dynamically established or may be solely administratively controlled.
   For more information on tunnels and processing of ER hops when using
   tunnels see [MPLS-HIERARCHY].

   Transit and egress nodes MUST verify that the node itself and, where
   appropriate, that the interface or tunnel on which the traffic will
   be transmitted can support the requested LSP Encoding Type.  If
   encoding cannot be supported, the node MUST generate a PathErr
   message, with a "Routing problem/Unsupported Encoding" indication.

   Nodes MUST verify that the type indicated in the Switching Type
   parameter is supported on the corresponding incoming interface.  If
   the type cannot be supported, the node MUST generate a PathErr
   message with a "Routing problem/Switching Type" indication.

   The G-PID parameter is normally only examined at the egress.  If the
   indicated G-PID cannot be supported then the egress MUST generate a
   PathErr message, with a "Routing problem/Unsupported L3PID"
   indication.  In the case of PSC and when penultimate hop popping
   (PHP) is requested, the penultimate hop also examines the (stored)
   G-PID during the processing of the Resv message.  In this case if the
   G-PID is not supported, then the penultimate hop MUST generate a
   ResvErr message with a "Routing problem/Unacceptable label value"
   indication.  The generated ResvErr message MAY include an Acceptable
   Label Set, see Section 4.1.

   When an error message is not generated, normal processing occurs.  In
   the transit case this will typically result in a Path message being
   propagated.  In the egress case and PHP special case this will
   typically result in a Resv message being generated.

2.2. Bandwidth Encoding

   Bandwidth encodings are carried in the SENDER_TSPEC and FLOWSPEC
   objects.  See [RFC3471] for a definition of values to be used for
   specific signal types.  These values are set in the Peak Data Rate
   field of Int-Serv objects, see [RFC2210].  Other bandwidth/service
   related parameters in the object are ignored and carried
   transparently.










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2.3. Generalized Label Object

   The format of a Generalized Label 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 (16)|   C-Type (2)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters and encoding of labels.

2.3.1. Procedures

   The Generalized Label travels in the upstream direction in Resv
   messages.

   The presence of both a generalized and normal label object in a Resv
   message is a protocol error and should treated as a malformed message
   by the recipient.


   The recipient of a Resv message containing a Generalized Label
   verifies that the values passed are acceptable.  If the label is
   unacceptable then the recipient MUST generate a ResvErr message with
   a "Routing problem/MPLS label allocation failure" indication.

2.4. Waveband Switching Object

   Waveband switching uses the same format as the generalized label, see
   section 2.2.  Waveband Label uses C-Type (3),

   In the context of waveband switching, the generalized label has the
   following format:














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    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 (16)|   C-Type (3)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Waveband Id                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Start Label                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           End Label                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.

2.4.1. Procedures

   The procedures defined in Section 2.3.1 apply to waveband switching.
   This includes generating a ResvErr message with a "Routing
   problem/MPLS label allocation failure" indication if any of the label
   fields are unrecognized or unacceptable.

   Additionally, when a waveband is switched to another waveband, it is
   possible that the wavelengths within the waveband will be mirrored
   about a center frequency.  When this type of switching is employed,
   the start and end label in the waveband label object MUST be flipped
   before forwarding the label object with the new waveband Id.  In this
   manner an egress/ingress LSR which receives a waveband label which
   has these values inverted, knows that it must also invert its egress
   association to pick up the proper wavelengths.

   This operation MUST be performed in both directions when a
   bidirectional waveband tunnel is being established.

2.5. Suggested Label Object

   The format of a Suggested_Label object is identical to a generalized
   label.  It is used in Path messages.  A Suggested_Label object uses
   Class-Number 129 (of form 10bbbbbb) and the C-Type of the label being
   suggested.

   Errors in received Suggested_Label objects MUST be ignored.  This
   includes any received inconsistent or unacceptable values.

   Per [RFC3471], if a downstream node passes a label value that differs
   from the suggested label upstream, the upstream LSR MUST either
   reconfigure itself so that it uses the label specified by the
   downstream node or generate a ResvErr message with a "Routing




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   problem/Unacceptable label value" indication.  Furthermore, an
   ingress node SHOULD NOT transmit data traffic using a suggested label
   until the downstream node passes a corresponding label upstream.

2.6. Label Set Object

   The Label_Set object uses Class-Number 36 (of form 0bbbbbbb) and the
   C-Type of 1.  It is used in Path messages.

   The format of a Label_Set 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 (36)|   C-Type (1)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Action     |      Reserved     |        Label Type         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Subchannel 1                         |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                               :                               :
   :                               :                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Subchannel N                         |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Label Type: 14 bits

      Indicates the type and format of the labels carried in the object.
      Values match the C-Type of the appropriate RSVP_LABEL object.
      Only the low order 8 bits are used in this field.

   See [RFC3471] for a description of other parameters.

2.6.1. Procedures

   A Label Set is defined via one or more Label_Set objects.  Specific
   labels/subchannels can be added to or excluded from a Label Set via
   Action zero (0) and one (1) objects respectively.  Ranges of
   labels/subchannels can be added to or excluded from a Label Set via
   Action two (2) and three (3) objects respectively.  When the
   Label_Set objects only list labels/subchannels to exclude, this
   implies that all other labels are acceptable.






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   The absence of any Label_Set objects implies that all labels are
   acceptable.  A Label Set is included when a node wishes to restrict
   the label(s) that may be used downstream.

   On reception of a Path message, the receiving node will restrict its
   choice of labels to one which is in the Label Set.  Nodes capable of
   performing label conversion may also remove the Label Set prior to
   forwarding the Path message.  If the node is unable to pick a label
   from the Label Set or if there is a problem parsing the Label_Set
   objects, then the request is terminated and a PathErr message with a
   "Routing problem/Label Set" indication MUST be generated.  It is a
   local matter if the Label Set is stored for later selection on the
   Resv or if the selection is made immediately for propagation in the
   Resv.

   On reception of a Path message, the Label Set represented in the
   message is compared against the set of available labels at the
   downstream interface and the resulting intersecting Label Set is
   forwarded in a Path message.  When the resulting Label Set is empty,
   the Path must be terminated, and a PathErr message, and a "Routing
   problem/Label Set" indication MUST be generated.  Note that
   intersection is based on the physical labels (actual wavelength/band
   values) which may have different logical values on different links,
   as a result it is the responsibility of the node to map these values
   so that they have a consistent physical meaning, or to drop the
   particular values from the set if no suitable logical label value
   exists.

   When processing a Resv message at an intermediate node, the label
   propagated upstream MUST fall within the Label Set.

   Note, on reception of a Resv message a node that is incapable of
   performing label conversion has no other choice than to use the same
   physical label (wavelength/band) as received in the Resv message.  In
   this case, the use and propagation of a Label Set will significantly
   reduce the chances that this allocation will fail.

3. Bidirectional LSPs

   Bidirectional LSP setup is indicated by the presence of an Upstream
   Label in the Path message.  An Upstream_Label object has the same
   format as the generalized label, see Section 2.3.  The Upstream_Label
   object uses Class-Number 35 (of form 0bbbbbbb) and the C-Type of the
   label being used.







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3.1. Procedures

   The process of establishing a bidirectional LSP follows the
   establishment of a unidirectional LSP with some additions.  To
   support bidirectional LSPs an Upstream_Label object is added to the
   Path message.  The Upstream_Label object MUST indicate a label that
   is valid for forwarding at the time the Path message is sent.

   When a Path message containing an Upstream_Label object is received,
   the receiver first verifies that the upstream label is acceptable.
   If the label is not acceptable, the receiver MUST issue a PathErr
   message with a "Routing problem/Unacceptable label value" indication.
   The generated PathErr message MAY include an Acceptable Label Set,
   see Section 4.1.

   An intermediate node must also allocate a label on the outgoing
   interface and establish internal data paths before filling in an
   outgoing upstream label and propagating the Path message.  If an
   intermediate node is unable to allocate a label or internal
   resources, then it MUST issue a PathErr message with a "Routing
   problem/MPLS label allocation failure" indication.

   Terminator nodes process Path messages as usual, with the exception
   that the upstream label can immediately be used to transport data
   traffic associated with the LSP upstream towards the initiator.

   When a bidirectional LSP is removed, both upstream and downstream
   labels are invalidated and it is no longer valid to send data using
   the associated labels.

3.2. Contention Resolution

   There are two additional contention resolution related considerations
   when controlling bidirectional LSP setup via RSVP-TE.  The first is
   that for the purposes of RSVP contention resolution, the node ID is
   the IP address used in the RSVP_HOP object.  The second is that a
   neighbor's node ID might not be known when sending an initial Path
   message.  When this case occurs, a node should suggest a label chosen
   at random from the available label space.

4. Notification

   This section covers several notification related extensions.  The
   first extension defines the Acceptable Label Set object to support
   Notification on Label Error, per [RFC3471].  The second and third
   extensions enable expedited notification of failures and other events
   to nodes responsible for restoring failed LSPs.  (The second
   extension, the Notify Request object, identifies where event



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   notifications are to be sent.  The third extension, the Notify
   message, provides for general event notification.)  The final
   notification related extension allows for the removal of Path state
   on handling of PathErr messages.

4.1. Acceptable Label Set Object

   Acceptable_Label_Set objects use a Class-Number 130 (of form
   10bbbbbb).  The remaining contents of the object, including C-Type,
   have the identical format as the Label_Set object, see Section 2.6.

   Acceptable_Label_Set objects may be carried in PathErr and ResvErr
   messages.  The procedures for defining an Acceptable Label Set follow
   the procedures for defining a Label Set, see Section 2.6.1.
   Specifically, an Acceptable Label Set is defined via one or more
   Acceptable_Label_Set objects.  Specific labels/subchannels can be
   added to or excluded from an Acceptable Label Set via  Action zero
   (0) and one (1) objects respectively.  Ranges of labels/subchannels
   can be added to or excluded from an Acceptable Label Set via Action
   two (2) and three (3) objects respectively.  When the
   Acceptable_Label_Set objects only list labels/subchannels to exclude,
   this implies that all other labels are acceptable.

   The inclusion of Acceptable_Label_Set objects is optional.  If
   included, the PathErr or ResvErr message SHOULD contain a "Routing
   problem/Unacceptable label value" indication.  The absence of
   Acceptable_Label_Set objects does not have any specific meaning.

4.2. Notify Request Objects

   Notifications may be sent via the Notify message defined below.  The
   Notify Request object is used to request the generation of
   notifications.  Notifications, i.e., the sending of a Notify message,
   may be requested in both the upstream and downstream directions.

4.2.1. Required Information

   The Notify Request Object may be carried in Path or Resv Messages,
   see Section 7.  The Notify_Request Class-Number is 195 (of form
   11bbbbbb).  The format of a Notify Request is:

      o  IPv4 Notify Request Object









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    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 (1) |  C-Type (1)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    IPv4 Notify Node Address                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   IPv4 Notify Node Address: 32 bits

      The IP address of the node that should be notified when generating
      an error message.

      o  IPv6 Notify Request Object

    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 (2) |  C-Type (2)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                    IPv6 Notify Node Address                   |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   IPv6 Notify Node Address: 16 bytes

      The IP address of the node that should be notified when generating
      an error message.

   If a message contains multiple Notify_Request objects, only the first
   object is meaningful.  Subsequent Notify_Request objects MAY be
   ignored and SHOULD NOT be propagated.

4.2.2. Procedures

   A Notify Request object may be inserted in Path or Resv messages to
   indicate the address of a node that should be notified of an LSP
   failure.  As previously mentioned, notifications may be requested in
   both the upstream and downstream directions.  Upstream notification
   is indicated via the inclusion of a Notify Request Object in the
   corresponding Path message.  Downstream notification is indicated via
   the inclusion of a Notify Request Object in the corresponding Resv
   message.






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   A node receiving a message containing a Notify Request object SHOULD
   store the Notify Node Address in the corresponding state block.  If
   the node is a transit node, it SHOULD also included a Notify Request
   object in the outgoing Path or Resv message.  The outgoing Notify
   Node Address MAY be updated based on local policy.

   Note that the inclusion of a Notify Request object does not guarantee
   that a Notify message will be generated.

4.3. Notify Message

   The Notify message provides a mechanism to inform non-adjacent nodes
   of LSP related events.  Notify messages are normally generated only
   after a Notify Request object has been received.  The Notify message
   differs from the currently defined error messages (i.e., PathErr and
   ResvErr messages) in that it can be "targeted" to a node other than
   the immediate upstream or downstream neighbor and that it is a
   generalized notification mechanism.  The Notify message does not
   replace existing error messages.  The Notify message may be sent
   either (a) normally, where non-target nodes just forward the Notify
   message to the target node, similar to ResvConf processing in
   [RFC2205]; or (b) encapsulated in a new IP header whose destination
   is equal to the target IP address.  Regardless of the transmission
   mechanism, nodes receiving a Notify message not destined to the node
   forward the message, unmodified, towards the target.

   To support reliable delivery of the Notify message, an Ack Message
   [RFC2961] is used to acknowledge the receipt of a Notify Message.
   See [RFC2961] for details on reliable RSVP message delivery.

4.3.1. Required Information

   The Notify message is a generalized notification message.  The IP
   destination address is set to the IP address of the intended
   receiver.  The Notify message is sent without the router alert
   option.  A single Notify message may contain notifications being
   sent, with respect to each listed session, both upstream and
   downstream.

   The Notify message has a Message Type of 21.  The Notify message
   format is as follows:

               ::=  []
                        [ [ | ] ... ]
                                   [  ]
                                    





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          ::= [  ]
                                    |
                                   

      ::=  [  ]
                                   [...]
                                   

    ::=  [...]
                                   

   The ERROR_SPEC object specifies the error and includes the IP address
   of either the node that detected the error or the link that has
   failed.  See ERROR_SPEC definition in [RFC2205].  The MESSAGE_ID and
   related objects are defined in [RFC2961] and are used when [RFC2961]
   is supported.

4.3.2. Procedures

   Notify messages are most commonly generated at nodes that detect an
   error that will trigger the generation of a PathErr or ResvErr
   message.  If a PathErr message is to be generated and a Notify
   Request object has been received in the corresponding Path message,
   then a Notify message destined to the recorded node SHOULD be
   generated.  If a ResvErr message is to be generated and a Notify
   Request object has been received in the corresponding Resv message,
   then a Notify message destined to the recorded node SHOULD be
   generated.  As previously mentioned, a single error may generate a
   Notify message in both the upstream and downstream directions.  Note
   that a Notify message MUST NOT be generated unless an appropriate
   Notify Request object has been received.

   When generating Notify messages, a node SHOULD attempt to combine
   notifications being sent to the same Notify Node and that share the
   same ERROR_SPEC into a single Notify message.  The means by which a
   node determines which information may be combined is implementation
   dependent.  Implementations may use event, timer based or other
   approaches.  If using a timer based approach, the implementation
   SHOULD allow the user to configure the interval over which
   notifications are combined.  When using a timer based approach, a
   default "notification interval" of 1 ms SHOULD be used.  Notify
   messages SHOULD be delivered using the reliable message delivery
   mechanisms defined in [RFC2961].

   Upon receiving a Notify message, the Notify Node SHOULD send a
   corresponding Ack message.





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4.4. Removing State with a PathErr message

   The PathErr message as defined in [RFC2205] is sent hop-by-hop to the
   source of the associated Path message.  Intermediate nodes may
   inspect this message, but take no action upon it.  In an environment
   where Path messages are routed according to an IGP and that route may
   change dynamically, this behavior is a fine design choice.

   However, when RSVP is used with explicit routes, it is often the case
   that errors can only be corrected at the source node or some other
   node further upstream.  In order to clean up resources, the source
   must receive the PathErr and then either send a PathTear (or wait for
   the messages to timeout).  This causes idle resources to be held
   longer than necessary and increases control message load.  In a
   situation where the control plane is attempting to recover from a
   serious outage, both the message load and the delay in freeing
   resources hamper the ability to rapidly reconverge.

   The situation can be greatly improved by allowing state to be removed
   by intermediate nodes on certain error conditions.  To facilitate
   this a new flag is defined in the ERROR_SPEC object.  The two
   currently defined ERROR_SPEC objects (IPv4 and IPv6 error spec
   objects) each contain a one byte flag field.  Within that field two
   flags are defined.  This specification defines a third flag, 0x04,
   Path_State_Removed.

   The semantics of the Path_State_Removed flag are simply that the node
   forwarding the error message has removed the Path state associated
   with the PathErr.  By default, the Path_State_Removed flag is always
   set to zero when generating or forwarding a PathErr message.  A node
   which encounters an error MAY set this flag if the error results in
   the associated Path state being discarded.  If the node setting the
   flag is not the session endpoint, the node SHOULD generate a
   corresponding PathTear.  A node receiving a PathErr message
   containing an ERROR_SPEC object with the Path_State_Removed flag set
   MAY also remove the associated Path state.  If the Path state is
   removed the Path_State_Removed flag SHOULD be set in the outgoing
   PathErr message.  A node which does not remove the associated Path
   state MUST NOT set the Path_State_Removed flag.  A node that receives
   an error with the Path_State_Removed flag set to zero MUST NOT set
   this flag unless it also generates a corresponding PathTear message.

   Note that the use of this flag does not result in any
   interoperability incompatibilities.







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5. Explicit Label Control

   The Label ERO (Explicit Route Object) and RRO (Record Route Object)
   subobjects are defined to support Explicit Label Control.  Note that
   the Label RRO subobject was defined in [RFC3209] and is being
   extended to support bidirectional LSPs.

5.1. Label ERO subobject

   The Label ERO subobject is defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|    Type     |     Length    |U|   Reserved  |   C-Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of L, U and Label parameters.

   Type

      3  Label

   Length

      The Length contains the total length of the subobject in bytes,
      including the Type and Length fields.  The Length is always
      divisible by 4.

   C-Type

      The C-Type of the included Label Object.  Copied from the Label
      Object.

5.1.1. Procedures

   The Label subobject follows a subobject containing the IP address, or
   the interface identifier [RFC3477], associated with the link on which
   it is to be used.  Up to two label subobjects may be present, one for
   the downstream label and one for the upstream label.  The following
   SHOULD result in "Bad EXPLICIT_ROUTE object" errors:

   o If the first label subobject is not preceded by a subobject
     containing an IP address, or an interface identifier [RFC3477],
     associated with an output link.



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   o For a label subobject to follow a subobject that has the L-bit set

   o On unidirectional LSP setup, for there to be a label subobject with
     the U-bit set

   o For there to be two label subobjects with the same U-bit values

   To support the label subobject, a node must check to see if the
   subobject following its associate address/interface is a label
   subobject.  If it is, one subobject is examined for unidirectional
   LSPs and two subobjects for bidirectional LSPs.  If the U-bit of the
   subobject being examined is clear (0), then value of the label is
   copied into a new Label_Set object.  This Label_Set object MUST be
   included on the corresponding outgoing Path message.

   If the U-bit of the subobject being examined is set (1), then value
   of the label is label to be used for upstream traffic associated with
   the bidirectional LSP.  If this label is not acceptable, a "Bad
   EXPLICIT_ROUTE object" error SHOULD be generated.  If the label is
   acceptable, the label is copied into a new Upstream_Label object.
   This Upstream_Label object MUST be included on the corresponding
   outgoing Path message.

   After processing, the label subobjects are removed from the ERO.

   Note an implication of the above procedures is that the label
   subobject should never be the first subobject in a newly received
   message.  If the label subobject is the the first subobject an a
   received ERO, then it SHOULD be treated as a "Bad strict node" error.

   Procedures by which an LSR at the head-end of an LSP obtains the
   information needed to construct the Label subobject are outside the
   scope of this document.

5.2. Label RRO subobject

   The Label RRO subobject is defined 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |     Length    |U|   Flags     |   C-Type      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of U and Label parameters.



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   Type

      3  Label

   Length

      See [RFC3209].

   Flags

      See [RFC3209].

   C-Type

      The C-Type of the included Label Object.  Copied from the Label
      Object.

5.2.1. Procedures

   Label RRO subobjects are included in RROs as described in [RFC3209].
   The only modification to usage and processing from [RFC3209] is that
   when labels are recorded for bidirectional LSPs, label ERO subobjects
   for both downstream and upstream labels MUST be included.

6. Protection Object

   The use of the Protection Object is optional.  The object is included
   to indicate specific protection attributes of an LSP.  The Protection
   Object uses Class-Number 37 (of form 0bbbbbbb).

   The format of the Protection 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 (37)|   C-Type (1)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |S|                  Reserved                       | Link Flags|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.










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6.1. Procedures

   Transit nodes processing a Path message containing a Protection
   Object MUST verify that the requested protection can be satisfied by
   the outgoing interface or tunnel (FA).  If it cannot, the node MUST
   generate a PathErr message, with a "Routing problem/Unsupported Link
   Protection" indication.

7. Administrative Status Information

   Administrative Status Information is carried in the Admin_Status
   object.  The object provides information related to the
   administrative state of a particular LSP.  The information is used in
   two ways.  In the first, the object is carried in Path and Resv
   messages to indicate the administrative state of an LSP.  In the
   second, the object is carried in a Notification message to request
   that the ingress node change the administrative state of an LSP.

7.1. Admin Status Object

   The use of the Admin_Status Object is optional.  It uses Class-Number
   196 (of form 11bbbbbb).

   The format of the Admin_Status 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(196)|   C-Type (1)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|                        Reserved                       |T|A|D|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.

7.2. Path and Resv Message Procedures

   The Admin_Status object is used to notify each node along the path of
   the status of the LSP.  Status information is processed by each node
   based on local policy and then propagated in the corresponding
   outgoing messages.  The object may be inserted in either Path or Resv
   messages at the discretion of the ingress (for Path messages) or
   egress (for Resv messages) nodes.  The absence of the object is
   equivalent to receiving an object containing values all set to zero
   (0).






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   Transit nodes receiving a non-refresh Path or Resv message containing
   an Admin_Status object, update their local state, take any
   appropriate local action based on the indicated status and then
   propagate the received Admin_Status object in the corresponding
   outgoing Path or Resv message.  If the values of an Admin_Status
   object received in a Resv message differs from the values received in
   a Path message then, with one exception, no local action should be
   taken but the values should still be propagated.  The one case where
   values received in the Resv message should result in local action is
   when both the received R and D bits are set, i.e., are one (1).

   Edge nodes receiving a non-refresh Path or Resv message containing an
   Admin_Status object, also update their local state and take any
   appropriate local action based on the indicated status.  When an
   Admin Status object is received with the R bit set, the receiving
   edge node should reflect the received values in a corresponding
   outgoing message.  Specifically, if an egress node receives a Path
   message with the R bit of the Admin_Status object set and the node
   has previously issued a Resv message corresponding to the Path
   message, the node SHOULD send an updated Resv message containing an
   Admin_Status object with the same values set, with the exception of
   the R bit, as received in the corresponding Path message.
   Furthermore, the egress node SHOULD also ensure that subsequent Resv
   messages sent by the node contain the same Admin Status Object.

   Additionally, if an ingress node receives a Resv message with the R
   bit of the Admin_Status object set, the node SHOULD send an updated
   Path message containing an Admin_Status object with the same values
   set, with the exception of the R bit, as received in the
   corresponding Resv message.  Furthermore, the ingress node SHOULD
   also ensure that subsequent Path messages sent by the node contain
   the same Admin Status Object.

7.2.1. Deletion procedure

   In some circumstances, particularly optical networks, it is useful to
   set the administrative status of an LSP before tearing it down.  In
   such circumstances the procedure SHOULD be followed when deleting an
   LSP from the ingress:

   1. The ingress node precedes an LSP deletion by inserting an Admin
      Status Object in a Path message and setting the Reflect (R) and
      Delete (D) bits.

   2. Transit and egress nodes process the Admin Status Object as
      described above.  (Alternatively, the egress MAY respond with a
      PathErr message with the Path_State_Removed flag set, see section
      4.4.)



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   3. Upon receiving the Admin Status Object with the Delete (D) bit set
      in the Resv message, the ingress node sends a PathTear message
      downstream to remove the LSP and normal RSVP processing takes
      place.

   In such circumstances the procedure SHOULD be followed when deleting
   an LSP from the egress:

   1. The egress node indicates its desire for deletion by inserting an
      Admin Status Object in a Resv message and setting the Reflect (R)
      and Delete (D) bits.

   2. Transit nodes process the Admin Status Object as described above.

   3. Upon receiving the Admin Status Object with the Delete (D) bit set
      in the Resv message, the ingress node sends a PathTear message
      downstream to remove the LSP and normal RSVP processing takes
      place.

7.2.2. Compatibility and Error Procedures

   It is possible that some nodes along an LSP will not support the
   Admin Status Object.  In the case of a non-supporting transit node,
   the object will pass through the node unmodified and normal
   processing can continue.  In the case of a non-supporting egress
   node, the Admin Status Object will not be reflected back in the Resv
   Message.  To support the case of a non-supporting egress node, the
   ingress SHOULD only wait a configurable period of time for the
   updated Admin Status Object in a Resv message.  Once the period of
   time has elapsed, the ingress node sends a PathTear message.  By
   default this period of time SHOULD be 30 seconds.

7.3. Notify Message Procedures

   Intermediate and egress nodes may trigger the setting of
   administrative status via the use of Notify messages.  To accomplish
   this, an intermediate or egress node generates a Notify message with
   the corresponding upstream notify session information.  The Admin
   Status Object MUST be included in the session information, with the
   appropriate bit or bits set.  The Reflect (R) bit MUST NOT be set.
   The Notify message may be, but is not required to be, encapsulated,
   see Section 4.3.

   An ingress node receiving a Notify message containing an Admin Status
   Object with the Delete (D) bit set, SHOULD initiate the deletion
   procedure described in the previous section.  Other bits SHOULD be
   propagated in an outgoing Path message as normal.




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7.3.1. Compatibility and Error Procedures

   Some special processing is required in order to cover the case of
   nodes that do not support the Admin Status Object and other error
   conditions.  Specifically, a node that sends a Notify message
   containing an Admin Status Object with the Down (D) bit set MUST
   verify that it receives a corresponding Path message with the Down
   (D) bit set within a configurable period of time.  By default this
   period of time SHOULD be 30 seconds.  If the node does not receive
   such a Path message, it SHOULD send a PathTear message downstream and
   either a ResvTear message or a PathErr message with the
   Path_State_Removed flag set upstream.

8. Control Channel Separation

   This section provides the protocol specific formats and procedures to
   required support a control channel not being in-band with a data
   channel.

8.1. Interface Identification

   The choice of the data interface to use is always made by the sender
   of the Path message. The choice of the data interface is indicated by
   the sender of the Path message by including the data channel's
   interface identifier in the message using a new RSVP_HOP object sub-
   type.  For bidirectional LSPs, the sender chooses the data interface
   in each direction.  In all cases but bundling, the upstream interface
   is implied by the downstream interface.  For bundling, the path
   sender explicitly identifies the component interface used in each
   direction.  The new RSVP_HOP object is used in Resv message to
   indicate the downstream node's usage of the indicated interface(s).




















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8.1.1. IF_ID RSVP_HOP Objects

   The format of the IPv4 IF_ID RSVP_HOP 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 (3) | C-Type (3)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 IPv4 Next/Previous Hop Address                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Logical Interface Handle                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              TLVs                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of the IPv6 IF_ID RSVP_HOP 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 (3) | C-Type (4)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                 IPv6 Next/Previous Hop Address                |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Logical Interface Handle                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              TLVs                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   See [RFC2205] for a description of hop address and handle fields.
   See [RFC3471] for a description of parameters and encoding of
   TLVs.










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8.1.2. Procedures

   An IF_ID RSVP_HOP object is used in place of previously defined
   RSVP_HOP objects.  It is used on links where there is not a one-to-
   one association of a control channel to a data channel, see
   [RFC3471].  The Hop Address and Logical Interface Handle fields are
   used per standard RSVP [RFC2205].

   TLVs are used to identify the data channel(s) associated with an LSP.
   For a unidirectional LSP, a downstream data channel MUST be
   indicated.  For bidirectional LSPs, a common downstream and upstream
   data channel is normally indicated.  In the special case where a
   bidirectional LSP that traverses a bundled link, it is possible to
   specify a downstream data channel that differs from the upstream data
   channel.  Data channels are specified from the viewpoint of the
   sender of the Path message.  The IF_ID RSVP_HOP object SHOULD NOT be
   used when no TLVs are needed.

   A node receiving one or more TLVs in a Path message saves their
   values and returns them in the HOP objects of subsequent Resv
   messages sent to the node that originated the TLVs.

   Note, the node originating an IF_ID object MUST ensure that the
   selected outgoing interface, as specified in the IF_ID object, is
   consistent with an ERO.  A node that receives an IF_ID object SHOULD
   check whether the information carried in this object is consistent
   with the information carried in a received ERO, and if not it MUST
   send a PathErr Message with the error code "Routing Error" and error
   value of "Bad Explicit Route Object" toward the sender.  This check
   CANNOT be performed when the initial ERO subobject is not the
   incoming interface.

8.2. Errored Interface Identification

   There are cases where it is useful to indicate a specific interface
   associated with an error.  To support these cases the IF_ID
   ERROR_SPEC Objects are defined.














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8.2.1. IF_ID ERROR_SPEC Objects

   The format of the IPv4 IF_ID ERROR_SPEC 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 (6) | C-Type (3)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     IPv4 Error Node Address                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |   Error Code  |          Error Value          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              TLVs                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of the IPv6 IF_ID ERROR_SPEC 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 (6) | C-Type (4)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                     IPv6 Error Node Address                   |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |   Error Code  |          Error Value          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              TLVs                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC2205] for a description of address, flags, error code and
   error value fields.  See [RFC3471] for a description of parameters
   and encoding of TLVs.

8.2.2. Procedures

   Nodes wishing to indicate that an error is related to a specific
   interface SHOULD use the appropriate IF_ID ERROR_SPEC Object in the
   corresponding PathErr or ResvErr message.  IF_ID ERROR_SPEC Objects
   SHOULD be generated and processed as any other ERROR_SPEC Object, see
   [RFC2205].



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9. Fault Handling

   The handling of two types of control communication faults is
   described in this section.  The first, referred to as nodal faults,
   relates to the case where a node losses its control state (e.g.,
   after a restart) but does not loose its data forwarding state.  In
   the second, referred to as control channel faults, relates to the
   case where control communication is lost between two nodes.  The
   handling of both faults is supported by the Restart_Cap object
   defined below and require the use of Hello messages.

   Note, the Restart_Cap object MUST NOT be sent when there is no
   mechanism to detect data channel failures independent of control
   channel failures.

   Please note this section is derived from [PAN-RESTART].

9.1. Restart_Cap Object

   The Restart_Cap Object is carried in Hello messages.

   The format of the Restart_Cap 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(131)|  C-Type  (1)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Restart Time                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Recovery Time                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Restart Time: 32 bits

      Restart Time is measured in milliseconds.  Restart Time SHOULD be
      set to the sum of the time it takes the sender of the object to
      restart its RSVP-TE component (to the point where it can exchange
      RSVP Hello with its neighbors) and the communication channel that
      is used for RSVP communication.  A value of 0xffffffff indicates
      that the restart of the sender's control plane may occur over an
      indeterminate interval and that the operation of its data plane is
      unaffected by control plane failures.  The method used to ensure
      continued data plane operation is outside the scope of this
      document.






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   Recovery Time: 32 bits

      The period of time, in milliseconds, that the sender desires for
      the recipient to re-synchronize RSVP and MPLS forwarding state
      with the sender after the re-establishment of Hello
      synchronization.  A value of zero (0) indicates that MPLS
      forwarding state was not preserved across a particular reboot.

9.2. Processing of Restart_Cap Object

   Nodes supporting state recovery advertise this capability by carrying
   the Restart_Cap object in Hello messages.  Such nodes MUST include
   the Restart_Cap object in all Hello messages. (Note that this
   includes Hello messages containing ACK objects.)  Usage of the
   special case Recovery Time values is described in greater detail
   below.

   When a node receives a Hello message with the Restart_Cap object, it
   SHOULD record the values of the parameters received.

9.3. Modification to Hello Processing to Support State Recovery

   When a node determines that RSVP communication with a neighbor has
   been lost, and the node previously learned that the neighbor supports
   state recovery, the node SHOULD wait at least the amount of time
   indicated by the Restart Time indicated by the neighbor before
   invoking procedures related to communication loss.  A node MAY wait a
   different amount of time based on local policy or configuration
   information.

   During this waiting period, all Hello messages MUST be sent with a
   Dst_Instance value set to zero (0), and Src_Instance should be
   unchanged.  While waiting, the node SHOULD also preserve the RSVP and
   MPLS forwarding state for (already) established LSPs that traverse
   the link(s) between the node and the neighbor.  In a sense with
   respect to established LSPs the node behaves as if it continues to
   receive periodic RSVP refresh messages from the neighbor.  The node
   MAY clear RSVP and forwarding state for the LSPs that are in the
   process of being established when their refresh timers expire.
   Refreshing of Resv and Path state SHOULD be suppressed during this
   waiting period.

   During this waiting period, the node MAY inform upstream nodes of the
   communication loss via a PathErr and/or upstream Notify message with
   "Control Channel Degraded State" indication.  If such notification
   has been sent, then upon restoration of the control channel the node





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   MUST inform other nodes of the restoration via a PathErr and/or
   upstream Notify message with "Control Channel Active State"
   indication.  (Specific error codes have been assigned by IANA.)

   When a new Hello message is received from the neighbor, the node must
   determine if the fault was limited to the control channel or was a
   nodal fault.  This determination is based on the Src_Instance
   received from the neighbor.  If the value is different than the value
   that was received from the neighbor prior to the fault, then the
   neighbor should be treated as if it has restarted.  Otherwise, the
   the fault was limited control channel.  Procedures for handling each
   case are described below.

9.4. Control Channel Faults

   In the case of control channel faults, the node SHOULD refresh all
   state shared with the neighbor.  Summary Refreshes [RFC2961] with the
   ACK_Desired flag set SHOULD be used, if supported.  Note that if a
   large number of messages are need, some pacing should be applied.
   All state SHOULD be refreshed within the Recovery time advertised by
   the neighbor.

9.5. Nodal Faults

   Recovering from nodal faults uses one new object and other existing
   protocol messages and objects.

9.5.1. Recovery Label

   The Recovery_Label object is used during the nodal fault recovery
   process.  The format of a Recovery_Label object is identical to a
   generalized label.  A Recovery_Label object uses Class-Number 34 (of
   form 0bbbbbbb) and the C-Type of the label being suggested.

9.5.2. Procedures for the Restarting node

   After a node restarts its control plane, a node that supports state
   recovery SHOULD check whether it was able to preserve its MPLS
   forwarding state.  If no forwarding state from prior to the restart
   was preserved, then the node MUST set the Recovery Time to 0 in the
   Hello message the node sends to its neighbors.

   If the forwarding state was preserved, then the node initiates the
   state recovery process.  The period during which a node is prepared
   to support the recovery process is referred to as the Recovery
   Period.  The total duration of the Recovery Period is advertised by
   the recovering node in the Recovery Time parameter of the Restart_Cap
   object.  The Recovery Time MUST be set to the duration of the



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   Recovery Period in all Hello messages sent during the Recovery
   Period.  State that is not resynchronized during the Recovery Period
   SHOULD be removed at the end of the Period.

   Note that if during Hello synchronization the restarting node
   determines that a neighbor does not support state recovery, and the
   restarting node maintains its MPLS forwarding state on a per neighbor
   basis, the restarting node should immediately consider the Recovery
   Period with that neighbor completed.  Forwarding state may be
   considered to be maintained on a per neighbor basis when per
   interface labels are used on point-to-point interfaces.

   When a node receives a Path message during the Recovery Period, the
   node first checks if it has an RSVP state associated with the
   message.  If the state is found, then the node handles this message
   according to previously defined procedures.

   If the 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 the RSVP state is not found, and the message carries a
   Recovery_Label object, the node searches its MPLS forwarding table
   (the one that was preserved across the restart) for an entry whose
   incoming interface matches the Path message and whose incoming label
   is equal to the label carried in the Recovery_Label object.

   If the MPLS forwarding table entry is not found, the node treats this
   as a setup for a new LSP, and handles it according to previously
   defined procedures.

   If the MPLS forwarding table entry is found, the appropriate RSVP
   state is created, the entry is bound to the LSP associated with the
   message, and related forwarding state should be considered as valid
   and refreshed.  Normal Path message processing should also be
   conducted.  When sending the corresponding outgoing Path message the
   node SHOULD include a Suggested_Label object with a label value
   matching the outgoing label from the now restored forwarding entry.
   The outgoing interface SHOULD also be selected based on the
   forwarding entry.  In the special case where a restarting node also
   has a restating downstream neighbor, a Recovery_Label object should
   be used instead of a Suggested_Label object.

   Additionally, for bidirectional LSPs, the node extracts the label
   from the UPSTREAM_LABEL object carried in the received Path message,
   and searches its MPLS forwarding table for an entry whose outgoing





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   label is equal to the label carried in the object (in the case of
   link bundling, this may also involved first identifying the
   appropriate incoming component link).

   If the MPLS forwarding table entry is not found, the node treats this
   as a setup for a new LSP, and handles it according to previously
   defined procedures.

   If the MPLS forwarding table entry is found, the entry is bound to
   the LSP associated with the Path message, and the entry should be
   considered to be re-synchronized.  In addition, if the node is not
   the tail-end of the LSP, the corresponding outgoing Path messages is
   sent with the incoming label from that entry carried in the
   UPSTREAM_LABEL object.

   During the Recovery Period, Resv messages are processed normally with
   two exceptions.  In the case that a forwarding entry is recovered, no
   new label or resource allocation is required while processing the
   Resv message.  The second exception is that ResvErr messages SHOULD
   NOT be generated when a Resv message with no matching Path state is
   received.  In this case the Resv message SHOULD just be silently
   discarded.

9.5.3. Procedures for the Neighbor of a Restarting node

   The following specifies the procedures that apply when the node
   reestablishes communication with the neighbor's control plane within
   the Restart Time, the node determines (using the procedures defined
   in Section 5 of [RFC3209]) that the neighbor's control plane has
   restarted, and the neighbor was able to preserve its forwarding state
   across the restart (as was indicated by a non-zero Recovery Time
   carried in the Restart_Cap object of the RSVP Hello messages received
   from the neighbor).  Note, a Restart Time value of 0xffffffff
   indicates an infinite Restart Time interval.

   Upon detecting a restart with a neighbor that supports state
   recovery, a node SHOULD refresh all Path state shared with that
   neighbor.  The outgoing Path messages MUST include a Recovery_Label
   object containing a label value corresponding to the label value
   received in the most recently received corresponding Resv message.
   All Path state SHOULD be refreshed within approximately 1/2 of the
   Recovery time advertised by the restarted neighbor.  If there are
   many LSP's going through the restarting node, the neighbor node
   should avoid sending Path messages in a short time interval, as to
   avoid unnecessary stressing the restarting node's CPU.  Instead, it
   should spread the messages across 1/2 the Recovery Time interval.





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   After detecting a restart of a neighbor that supports state recovery,
   all Resv state shared with the restarting node MUST NOT be refreshed
   until a corresponding Path message is received.  This requires
   suppression of normal Resv and Summary Refresh processing to the
   neighbor during the Recovery Time advertised by the restarted
   neighbor.  As soon as a corresponding Path message is received a Resv
   message SHOULD be generated and normal state processing SHOULD be
   re-enabled.

10. RSVP Message Formats and Handling

   This message summarizes RSVP message formats and handling as modified
   by GMPLS.

10.1. RSVP Message Formats

   This section presents the RSVP message related formats as modified by
   this document.  Where they differ, formats for unidirectional LSPs
   are presented separately from bidirectional LSPs.  Unmodified formats
   are not listed.  Again, MESSAGE_ID and related objects are defined in
   [RFC2961].

   The format of a Path message is as follows:

 ::=        [  ]
                         [ [ | ] ... ]
                         [  ]
                          
                         
                         [  ]
                         
                         [  ]
                         [  ... ]
                         [  ]
                         [  ]
                         [  ]
                         [  ... ]
                         













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   The format of the sender description for unidirectional LSPs is:

 ::=   
                         [  ]
                         [  ]
                         [  ]
                         [  ]

   The format of the sender description for bidirectional LSPs is:

 ::=   
                         [  ]
                         [  ]
                         [  ]
                         [  ]
                         

   The format of a PathErr message is as follows:

 ::=     [  ]
                         [ [ | ] ... ]
                         [  ]
                          
                         [  ... ]
                         [  ... ]
                         

   The format of a Resv message is as follows:

 ::=        [  ]
                         [ [ | ] ... ]
                         [  ]
                          
                         
                         [  ]  [  ]
                         [  ]
                         [  ]
                         [  ... ]