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Versions: 00 01 02 03 04 05 06 07 08 RFC 3473

Network Working Group        Peter Ashwood-Smith (Nortel Networks Corp.)
Internet Draft                          Ayan Banerjee (Calient Networks)
Expiration Date: May 2001                    Lou Berger (Movaz Networks)
                                      Greg Bernstein (Ciena Corporation)
                                           John Drake (Calient Networks)
                                           Yanhe Fan (Axiowave Networks)
                               Kireeti Kompella (Juniper Networks, Inc.)
                                                       Eric Mannie (GTS)
                                     Jonathan P. Lang (Calient Networks)
                                        Bala Rajagopalan (Tellium, Inc.)
                                           Yakov Rekhter (Cisco Systems)
                                           Debanjan Saha (Tellium, Inc.)
                                                 Vishal Sharma (Tellabs)
                                          George Swallow (Cisco Systems)
                                              Z. Bo Tang (Tellium, Inc.)

                                                           November 2000


            Generalized MPLS Signaling - RSVP-TE Extensions


               draft-ietf-mpls-generalized-rsvp-te-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   To view the current status of any Internet-Draft, please check the
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Abstract

   This document describes extensions to RSVP-TE signaling required to
   support Generalized MPLS.  Generalized MPLS extends MPLS to encompass
   time-division (e.g. SONET ADMs), wavelength (optical lambdas) and
   spatial switching (e.g. incoming port or fiber to outgoing port or
   fiber).  This document presents an RSVP-TE specific description of
   the extensions.  A CR-LDP specific description can be found in
   [GMPLS-LDP].  A generic functional description is presented in
   [GMPLS-SIG].



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Contents

 1      Introduction  ..............................................   3
 2      Label Related Formats   ....................................   3
 2.1    Generalized Label Request   ................................   3
 2.1.1  Generalized Label Request with SONET/SDH Label Range  ......   4
 2.1.2  Procedures  ................................................   4
 2.1.3  Bandwidth Encoding  ........................................   5
 2.2    Generalized Label  .........................................   5
 2.2.1  Procedures  ................................................   6
 2.3    Waveband Switching  ........................................   6
 2.3.1  Procedures  ................................................   7
 2.4    Suggested Label  ...........................................   7
 2.5    Label Set  .................................................   7
 2.5.1  Procedures  ................................................   8
 3      Bidirectional LSPs  ........................................   9
 3.1    Procedures  ................................................   9
 3.2    Contention Resolution  .....................................  10
 4      Notification  ..............................................  10
 4.1    Notify Request Object  .....................................  10
 4.1.1  Required Information  ......................................  11
 4.1.2  Procedures  ................................................  11
 4.2    Notify Message  ............................................  12
 4.2.1  Required Information  ......................................  12
 4.2.2  Procedures  ................................................  13
 4.3    Removing State with a PathErr message  .....................  13
 5      Explicit Label Control  ....................................  14
 5.1    Procedures  ................................................  15
 6      RSVP Message Formats  ......................................  16
 7      Acknowledgments  ...........................................  17
 8      Security Considerations  ...................................  17
 9      References  ................................................  18
10      Authors' Addresses  ........................................  18







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Changes from previous version:

o  Moved protocol specific details into two documents, one for RSVP-TE
   and one for CR-LDP.
o  Fixed bandwidth encodings
o  Revised Notify message format to disambiguate upstream and
   downstream notifications.
o  Minor text cleanup


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 [GMPLS-SIG].  This document presents RSVP-TE
   specific formats and mechanisms needed to support all four classes of
   interfaces.  CR-LDP extensions can be found in [GMPLS-LDP].

   [GMPLS-SIG] should be viewed as a companion document to this
   document.  The format of this document parallels [GMPLS-SIG].  In
   addition to the other features of Generalized MPLS, this document
   also defines RSVP-TE specific features to support rapid failure
   notification, see Section 4.

   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

   A Path message SHOULD contain as specific an LSP 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.






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   The format of a Generalized Label Request 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)[TBA]|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | LSP Enc. Type |Link Prot.Flags|             G-PID             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      See [GMPLS-SIG] for a description of parameters.


2.1.1. Generalized Label Request with SONET/SDH Label Range

   The format of a Generalized Label Request with SONET/SDH Label Range
   (in RSVP) 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 (5)[TBA]|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | LSP Enc. Type |Link Prot.Flags|             G-PID             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  RGT  |   RT  |    Reserved   |              RNC              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      See [GMPLS-SIG] for a description of parameters.


2.1.2. Procedures

   A node processing the Path message containing the Generalized Label
   Request must verify that the requested parameters can be satisfied by
   the incoming interface, the node and by the outgoing interface.  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.

   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 outgoing interface or tunnel can support the



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   requested LSP Encoding Type.  If encoding cannot be supported, the
   node MUST generate a PathErr message, with a "Routing
   problem/Unsupported Encoding" indication.

   Transit nodes MUST verify that the outgoing interface or tunnel can
   support the requested Link Protection Flags.  If it cannot, the node
   MUST generate a PathErr message, with a "Routing problem/Unsupported
   Link Protection" 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 GPID"
   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.

   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.


2.1.3. Bandwidth Encoding

   Bandwidth encodings are carried in the SENDER_TSPEC and FLOWSPEC
   objects.  See [GMPLS-SIG] 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.  Other bandwidth/service related
   parameters in the object are ignored and carried transparently.


2.2. Generalized Label


   The format of a Generalized Label 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                             |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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      See [GMPLS-SIG] for a description of parameters and encoding of
      SDH, SONET, port, wavelength and other labels.


2.2.1. 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.


2.3. Waveband Switching

   Waveband switching uses the same format as the generalized label, see
   section 2.2.  For compatibility reasons, a new RSVP c-type (3) is
   assigned for the Waveband Label.

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

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Length             | Class-Num (16)|   C-Type (3)  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Waveband Id                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Start Label                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           End Label                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      See [GMPLS-SIG] for a description of parameters.









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2.3.1. Procedures

   The procedures defined in Section 2.2.1 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.  Without this
   mechanism and with an odd number of mirrored switching operations,
   the egress LSRs will not know that an input wavelength of say L1 will
   emerge from the waveband tunnel as L100.

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


2.4. Suggested Label

   The format of a suggested label is identical to a generalized label.
   It is used in Path messages.  Suggested Label uses a new Class-Number
   (TBD of form 10bbbbbb) and the C-type of the label being suggested.

   Errors in received Suggested Labels MUST be ignored.  This includes
   any received inconsistent or unacceptable values.


2.5. Label Set

   The Label_Set object uses a Class-Number TBA (of form 0bbbbbbb) and
   the C-type of the label type being described.














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   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(TBA)|   C-Type (1)  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Reserved           |  Label Type   |    Action     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Subchannel 1                         |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      :                               :                               :
      :                               :                               :
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Subchannel N                         |
      |                              ...                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Label Type: 8 bits

         Indicates the type and format of the labels carried in the
         object.  Values match the C-Type of the appropriate Label
         object.

      See [GMPLS-SIG] for a description of other parameters.


2.5.1. 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.

   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 a CI-capable interface will restrict
   its choice of labels to one which is in the Label Set.  The CI-
   capable receiver 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



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   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 for a CI-incapable interface, 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 for an interface which is CI-
   incapable it has no other choice than to use the same physical label
   (wavelength/band) as received in the Resv. In this case, the use and
   propagation of a Label Set will significantly reduce the chances that
   this allocation will fail when CI-incapable nodes are traversed.


3. Bidirectional LSPs

   Bidirectional LSP setup is indicated by the presence of an Upstream
   Label in the Path message.   An Upstream Label has the same format as
   the generalized label, see Section 2.2.  The Upstream Label uses
   Class-Number TBD (of form 0bbbbbbb) and the C-type of the label being
   suggested.


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 is added to the Path
   message.  The Upstream Label 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 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.



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   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/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 LSPs 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 defines three signaling extensions that modify error
   handling, enable expedited notification of failures and other events
   to nodes responsible for restoring failed LSPs.  The first extension,
   the Notify Request object, identifies where event notifications are
   to be sent.  The second, the Notify message, provides for general
   event notification.  The final extension allows for the removal of
   Path state on handling of PathErr messages.


4.1. Notify Request Object

   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.







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4.1.1. Required Information

   The Notify Request Object may be carried in Path or Resv Messages,
   see Section 6.  The NOTIFY_REQUEST Class-Number is TBA (of form
   11bbbbbb).  The format of a Notify Request 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(TBD)|  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.

   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.


4.1.2. 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.

   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.








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4.2. Notify Message

   The Notify message provides a mechanism to inform non-adjacent nodes
   of LSP related events.  Notify messages are only generated after a
   Notify Request object has been received.  The Notify message differs
   from the currently defined error messages (i.e., PathErr and ResvErr
   messages of RSVP) 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 [RSVP];
   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
   [RSVP-RR] is used to acknowledge the receipt of a Notify Message.
   See [RSVP-RR] for details on reliable RSVP message delivery.


4.2.1. 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.

   <Notify message> ::= <Common Header> [<INTEGRITY>] <MESSAGE_ID>
                        <ERROR_SPEC> <notify session list>

   <notify session list> ::= [ <notify session list> ]
                             <upstream notify session> |
                             <downstream notify session>

   <downstream notify session> ::= <SESSION> [<POLICY_DATA>...]
                                   <sender descriptor>

   <upstream notify session> ::= <SESSION> [<POLICY_DATA>...]
                                 <flow descriptor list descriptor>

   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
   object is defined in [RSVP-RR].



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4.2.2. Procedures

   Notify messages are 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 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 [RSVP-RR].

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


4.3. 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 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.



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   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.


5. Explicit Label Control

   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 [GMPLS-SIG] for a description of L, U and Label parameters.

      Type

         3  Label





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      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. Procedures

   The Label subobject follows a subobject containing the IP address, or
   the interface identifier [MPLS-UNNUM], associated with the link on
   which it is to be used.  The preceding subobject must be a strict
   object.  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:
     -  If the first label subobject is not preceded by a subobject
        containing an IP address, or a interface identifier
        [MPLS-UNNUM], associated with an output link.
     -  For a label subobject to follow a subobject that has the L-bit
        set
     -  On unidirectional LSP setup, for there to be a label subobject
        with the U-bit set
     -  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 it's 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



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   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.


6. 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.

   The format of a Path message is as follows:

         <Path Message> ::=       <Common Header> [ <INTEGRITY> ]
                                  <SESSION> <RSVP_HOP>
                                  <TIME_VALUES>
                                  [ <EXPLICIT_ROUTE> ]
                                  <LABEL_REQUEST>
                                  [ <LABEL_SET> ... ]
                                  [ <SESSION_ATTRIBUTE> ]
                                  [ <NOTIFY_REQUEST> ]
                                  [ <POLICY_DATA> ... ]
                                  <sender descriptor>

   The format of the sender description for unidirectional LSPs is:

         <sender descriptor> ::=  <SENDER_TEMPLATE> <SENDER_TSPEC>
                                  [ <ADSPEC> ]
                                  [ <RECORD_ROUTE> ]
                                  [ <SUGGESTED_LABEL> ]

   The format of the sender description for bidirectional LSPs is:

         <sender descriptor> ::=  <SENDER_TEMPLATE> <SENDER_TSPEC>
                                  [ <ADSPEC> ]
                                  [ <RECORD_ROUTE> ]
                                  [ <SUGGESTED_LABEL> ]
                                  <UPSTREAM_LABEL>








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   The format of a Resv message is as follows:

         <Resv Message> ::=       <Common Header> [ <INTEGRITY> ]
                                  <SESSION>  <RSVP_HOP>
                                  <TIME_VALUES>
                                  [ <RESV_CONFIRM> ]  [ <SCOPE> ]
                                  [ <NOTIFY_REQUEST> ]
                                  [ <POLICY_DATA> ... ]
                                  <STYLE> <flow descriptor list>

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


7. Acknowledgments

   This draft is the work of numerous authors and consists of a
   composition of a number of previous drafts in this area.  A list of
   the drafts from which material and ideas were incorporated follows:

   draft-saha-rsvp-optical-signaling-00.txt
   draft-lang-mpls-rsvp-oxc-00.txt
   draft-kompella-mpls-optical-00.txt
   draft-fan-mpls-lambda-signaling-00.txt

   Valuable comments and input were received from a number of people,
   including Igor Bryskin and Adrian Farrel.  Portions of Section 4 are
   based on suggestions and text proposed by Adrian Farrel.


8. Security Considerations

   The transmission of notify messages using IP in IP, break RSVP's hop-
   by-hop integrity and authentication model.  Fortunately, such usage
   mirrors the IP end-to-end model.  In the case where RSVP is
   generating end-to-end messages and integrity and/or authentication
   are desired, the standard IPSEC based integrity and authentication
   methods SHOULD be used.

   This draft introduce no other new security considerations to [RSVP-
   TE].











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9. References

[MPLS-HIERARCHY] Kompella, K., and Rekhter, Y., "LSP Hierarchy with
                 MPLS TE", Internet Draft,
                 draft-ietf-mpls-lsp-hierarchy-00.txt, July 2000.

[GMPLS-LDP] Ashwood-Smith, P. et al, "Generalized MPLS Signaling -
            CR-LDP Extensions", Internet Draft,
            draft-ietf-mpls-generalized-cr-ldp-00.txt,
            November 2000.

[GMPLS-SIG] Ashwood-Smith, P. et al, "Generalized MPLS -
            Signaling Functional Description", Internet Draft,
            draft-ietf-mpls-generalized-signaling-01.txt,
            November 2000.

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

[RFC2205] Braden, R. Ed. et al, "Resource ReserVation Protocol
           -- Version 1 Functional Specification", RFC 2205,
           September 1997.

[RSVP-TE] Awduche, D.O., Berger, L., Gan, D.-H., Li, T., Swallow, G.,
          and Srinivasan, V., "RSVP-TE: Extensions to RSVP for LSP
          Tunnels,"  Internet Draft,
          draft-ietf-mpls-rsvp-lsp-tunnel-06.txt, July 2000.

[RSVP-RR]  Berger L., Gan D., Swallow G., Pan P., Tommasi F.,
           Molendini S., "RSVP Refresh Overhead Reduction Extensions",
           draft-ietf-rsvp-refresh-reduct-05.txt, June 2000.


10. Authors' Addresses

   Peter Ashwood-Smith
   Nortel Networks Corp.
   P.O. Box 3511 Station C,
   Ottawa, ON K1Y 4H7
   Canada
   Phone:  +1 613 763 4534
   Email:  petera@nortelnetworks.com









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   Ayan Banerjee
   Calient Networks
   5853 Rue Ferrari
   San Jose, CA 95138
   Phone:  +1 408 972-3645
   Email:  abanerjee@calient.net

   Lou Berger
   Movaz Networks
   Phone:  +1 301 468 9228
   Email:  lberger@movaz.com

   Greg Bernstein
   Ciena Corporation
   10480 Ridgeview Court
   Cupertino, CA 94014
   Phone:  +1 408 366 4713
   Email:  greg@ciena.com

   John Drake
   Calient Networks
   5853 Rue Ferrari
   San Jose, CA 95138
   Phone:  +1 408 972 3720
   Email:  jdrake@calient.net

   Yanhe Fan
   Axiowave Networks, Inc.
   100 Nickerson Road
   Marlborough, MA 01752
   Phone:  +1 508 460 6969 Ext. 627
   Email:  yfan@axiowave.com

   Kireeti Kompella
   Juniper Networks, Inc.
   1194 N. Mathilda Ave.
   Sunnyvale, CA 94089
   Email:  kireeti@juniper.net

   Jonathan P. Lang
   Calient Networks
   25 Castilian
   Goleta, CA 93117
   Email:  jplang@calient.net







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   Eric Mannie
   GTS
   Terhulpsesteenweg 6A
   1560 Hoeilaart - Belgium
   Phone:  +32 2 658 56 52
   Mobile: +32 496 58 56 52
   Fax:    +32 2 658 51 18
   Email:  eric.mannie@gts.com

   Bala Rajagopalan
   Tellium, Inc.
   2 Crescent Place
   P.O. Box 901
   Oceanport, NJ 07757-0901
   Phone:  +1 732 923 4237
   Fax:    +1 732 923 9804
   Email:  braja@tellium.com

   Yakov Rekhter
   cisco Systems
   Email:  yakov@cisco.com

   Debanjan Saha
   Tellium Optical Systems
   2 Crescent Place
   Oceanport, NJ 07757-0901
   Phone:  +1 732 923 4264
   Fax:    +1 732 923 9804
   Email:  dsaha@tellium.com

   Vishal Sharma
   Tellabs Research Center
   One Kendall Square
   Bldg. 100, Ste. 121
   Cambridge, MA 02139-1562
   Phone:  +1 617 577 8760
   Email:  Vishal.Sharma@tellabs.com

   George Swallow
   Cisco Systems, Inc.
   250 Apollo Drive
   Chelmsford, MA 01824
   Voice:  +1 978 244 8143
   Email:  swallow@cisco.com







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   Z. Bo Tang
   Tellium, Inc.
   2 Crescent Place
   P.O. Box 901
   Oceanport, NJ 07757-0901
   Phone:  +1 732 923 4231
   Fax:    +1 732 923 9804
   Email:  btang@tellium.com











































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