GMPLS CR-LDP: Generalized Multi-Protocol Label Switching (GMPLS) Signaling Constraint-based Routed Label Distribution Protocol (CR-LDP) Extensions

Network Working Group                           P. Ashwood-Smith, Editor
Request for Comments: 3472                               Nortel Networks
Category: Standards Track                              L. Berger, Editor
                                                          Movaz Networks
                                                            January 2003


     Generalized Multi-Protocol Label Switching (GMPLS) Signaling
Constraint-based Routed Label Distribution Protocol (CR-LDP) 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) Constraint-based Routed Label Distribution Protocol (CR-LDP)
   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 CR-LDP 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  ...............................   3
    2.2  Generalized Label  .......................................   4
    2.3  Waveband Switching  ......................................   5
    2.4  Suggested Label  .........................................   6
    2.5  Label Set  ...............................................   6
   3.  Bidirectional LSPs  ........................................   8
    3.1  Procedures  ..............................................   8
   4.  Notification on Label Error  ...............................   9
   5.    Explicit Label Control  ..................................   9
    5.1  Procedures  ..............................................   9
   6.  Protection TLV  ............................................  10
    6.1  Procedures  ..............................................  11
   7.  Administrative Status Information  .........................  11
    7.1  Admin Status TLV  ........................................  11
    7.2  REQUEST and MAPPING Message Procedures  ..................  12
    7.3  Notification Message Procedures  .........................  13
   8.  Control Channel Separation  ................................  14
    8.1  Interface Identification  ................................  14
    8.2  Errored Interface Identification  ........................  15
   9.  Fault Handling     .........................................  17
   10  Acknowledgments  ...........................................  17
   11. Security Considerations  ...................................  17
   12. IANA Considerations  .......................................  17
   13. Intellectual Property Considerations  ......................  18
   14. References  ................................................  18
    14.1  Normative References  ...................................  18
    14.2  Informative References  .................................  19
   15. Contributors  ..............................................  19
   16. Editors' Addresses  ........................................  22
   17. Full Copyright Statement ...................................  23

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 CR-LDP
   specific formats and mechanisms needed to support all four classes of
   interfaces.  RSVP-TE extensions can be found in [RFC3473].

   [RFC3471] should be viewed as a companion document to this document.
   The format of this document parallels [RFC3471].  It should be noted
   that the RSVP-TE specific version of Generalized MPLS includes RSVP
   specific support for rapid failure notification, see Section 4
   [RFC3473].  For CR-LDP there is not currently a similar mechanism.
   When a failure is detected it will be propagated with
   RELEASE/WITHDRAW messages radially outward from the point of failure.
   Resources are to be released in this phase and actual resource
   information may be fed back to the source using a feedback
   mechanisms.

   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 REQUEST 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 Type, Length,
   and Value (TLV) 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 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x0824)         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | LSP Enc. Type |Switching Type |             G-PID             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.

2.1.1. Procedures

   A node processing a REQUEST message containing a 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 (Explicit Route)
   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
   requested LSP Encoding Type.  If encoding cannot be supported, the
   node MUST generate a NOTIFICATION 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 NOTIFICATION
   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
   NOTIFICATION message, with a "Routing problem/Unsupported G-PID"
   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 MAPPING message.  In this case if
   the G-PID is not supported, then the penultimate hop MUST generate a
   NOTIFICATION message with a "Routing problem/Unacceptable label
   value" indication.  The generated NOTIFICATION message MAY include an
   Acceptable Label Set, see Section 4.

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

2.1.2. Bandwidth Encoding

   Bandwidth encodings are carried in the CR-LDP Traffic Parameters TLV.
   See [RFC3471] for a definition of values to be used for specific
   signal types.  These values are set in the Peak and Committed Data
   Rate fields of the Traffic Parameters TLV.  Other bandwidth/service
   related parameters in the TLV 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x0825)         |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Label                             |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

2.2.1. Procedures

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

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

   The recipient of a MAPPING message containing a Generalized Label
   verifies that the values passed are acceptable.  If the label is
   unacceptable then the recipient MUST generate a NOTIFICATION message
   with a "Routing problem/MPLS label allocation failure" indication.
   The generated NOTIFICATION message MAY include an Acceptable Label
   Set, see Section 4.

2.3. Waveband Switching

   Waveband switching uses the same format as the generalized label, see
   section 2.2.  The type 0x0828 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x0828)         |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Waveband Id                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Start Label                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           End Label                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.

2.3.1. Procedures

   The procedures defined in Section 2.2.1 apply to waveband switching.
   This includes generating a NOTIFICATION 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 TLV MUST be swapped
   before forwarding the label TLV with the new waveband Id.  In this
   manner an egress/ingress LSR that 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 REQUEST messages.  Suggested Label uses type = 0x904.

   Errors in received Suggested Labels 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 NOTIFICATION message with a "Routing
   problem/Unacceptable label value" indication.  Furthermore, an
   ingress node SHOULD NOT transmit data traffic using a suggested label
   until the downstream node passes corresponding a label upstream.

2.5. Label Set

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|  Type (0x0827)            |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Action     |      Reserved     |        Label Type         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Subchannel 1                         |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                               :                               :
   :                               :                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Subchannel N                         |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Label Type: 14 bits

      Indicates the type and format of the labels carried in the TLV.
      Values match the TLV type of the appropriate Label TLV.

   See [RFC3471] for a description of other parameters.

2.5.1. Procedures

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

   The absence of any Label Set TLVs 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 REQUEST 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 REQUEST message.  If the node is unable to
   pick a label from the Label Set or if there is a problem parsing the
   Label Set TLVs, then the request is terminated and a NOTIFICATION
   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 MAPPING message or if the selection is made
   immediately for propagation in the MAPPING message.

   On reception of a REQUEST 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 REQUEST message.  When the resulting Label Set is
   empty, the REQUEST must be terminated, and a NOTIFICATION 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 MAPPING message at an intermediate node, the label
   propagated upstream MUST fall within the Label Set.

   Note, on reception of a MAPPING 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 MAPPING 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 REQUEST message.  An Upstream Label has the same format
   as the generalized label, see Section 2.2.  Upstream Label uses type
   = 0x0826.

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 REQUEST
   message.  The Upstream Label MUST indicate a label that is valid for
   forwarding at the time the REQUEST message is sent.

   When a REQUEST 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 NOTIFICATION
   message with a "Routing problem/Unacceptable label value" indication.
   The generated NOTIFICATION message MAY include an Acceptable Label
   Set, see Section 4.

   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 REQUEST message.  If an
   intermediate node is unable to allocate a label or internal
   resources, then it MUST issue a NOTIFICATION message with a "Routing
   problem/Label allocation failure" indication.

   Terminator nodes process REQUEST 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.

4. Notification on Label Error

   This section defines the Acceptable Label Set TLV to support
   Notification on Label Error per [RFC3471].  An Acceptable Label Set
   TLV uses a type value of 0x082a.  The remaining contents of the TLV
   have the identical format as the Label Set TLV, see Section 2.5.

   Acceptable Label Set TLVs may be carried in NOTIFICATION messages.
   The procedures for defining an Acceptable Label Set follow the
   procedures for defining a Label Set, see Section 2.5.1.
   Specifically, an Acceptable Label Set is defined via one or more
   Acceptable Label Set TLVs.  Specific labels/subchannels can be added
   to or excluded from an Acceptable Label Set via Action zero (0) and
   one (1) TLVs respectively.  Ranges of labels/subchannels can be added
   to or excluded from an Acceptable Label Set via Action two (2) and
   three (3) TLVs respectively.  When the Acceptable Label Set TLVs only
   list labels/subchannels to exclude, this implies that all other
   labels are acceptable.

   The inclusion of Acceptable Label Set TLVs is optional.  If included,
   the NOTIFICATION message SHOULD contain a "Routing
   problem/Unacceptable label value" indication.  The absence of
   Acceptable Label Set TLVs does not have any specific meaning.

5. Explicit Label Control

   The Label ER-Hop TLV 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|     Type (0x0829)         |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|U|      Reserved             |   Label                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Label (continued)                       |
   |                              ...                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

5.1. Procedures

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

   o   If the first label ER-Hop is not preceded by a ER-Hop containing
       an IP address, or a interface identifier [MPLS-UNNUM], associated
       with an output link.
   o   For a label ER-Hop to follow a ER-Hop that has the L-bit set.
   o   On unidirectional LSP setup, for there to be a label ER-Hop with
       the U-bit set.
   o   For there to be two label ER-Hops with the same U-bit values.

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

   If the U-bit of the ER-Hop 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" error SHOULD be generated.  If the label is
   acceptable, the label is copied into a new Upstream Label TLV.  This
   Upstream Label TLV MUST be included on the corresponding outgoing
   REQUEST message.

   After processing, the label ER-Hops are removed from the ER.

   Note an implication of the above procedures is that the label ER-Hop
   should never be the first ER-Hop in a newly received message.  If the
   label ER-Hop is the first ER-Hop an a received ER, 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 ER-Hop are outside the
   scope of this document.

6. Protection TLV

   The use of the Protection TLV is optional.  The TLV is included to
   indicate specific protection attributes of an LSP.

   The format of Protection Information TLV 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x0835)         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |S|                  Reserved                       | Link Flags|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.

6.1. Procedures

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

7. Administrative Status Information

   Administrative Status Information is carried in the Admin Status TLV.
   The TLV provides information related to the administrative state of a
   particular LSP.  The information is used in two ways.  In the first,
   the TLV is carried in REQUEST and MAPPING messages to indicate the
   administrative state of an LSP.  In the second, the TLV is carried in
   Notification message to request a change to the administrative state
   of an LSP.

7.1. Admin Status TLV

   The use of the Admin Status TLV is optional.  It uses Type = 0x082b.
   The format of the TLV is:

   The format of Admin Status TLV in REQUEST, MAPPING and Notification
   Messages 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x082b)         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|                          Reserved                     |T|A|D|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3471] for a description of parameters.

7.2. REQUEST and MAPPING Message Procedures

   The Admin Status TLV is used to notify each node along the path of
   the status of the LSP.  Each node processes status information based
   on local policy and then propagated in the corresponding outgoing
   messages.  The TLV is inserted in REQUEST messages at the discretion
   of the ingress node.  The absence of the TLV is the equivalent to
   receiving a TLV containing values all set to zero.

   Transit nodes receiving a REQUEST message containing an Admin Status
   TLV, update their local state, take any appropriate local action
   based on the indicated status and then propagate the received Admin
   Status TLV in the outgoing REQUEST message.

   Edge nodes receiving a REQUEST message containing an Admin Status
   TLV, also update their local state and take any appropriate local
   action based on the indicated status.  When the ADMIN Status TLV is
   received with the R bit set, the receiving edge node should reflect
   the received values in a corresponding MAPPING message.
   Specifically, if an egress node receives a Request message with the R
   bit of the Admin_Status TLV set and the node the node SHOULD send a
   Mapping message containing an Admin_Status TLV with the same values
   set, with the exception of the R bit, as received in the
   corresponding Request message.

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:

   o   The ingress node precedes an LSP deletion by inserting an Admin
       Status TLV in a Notification Message setting the Reflect (R) and
       Delete (D) bits.

   o   Transit nodes process the Admin Status TLV by passing the
       Notification message.  The egress node May respond with a
       Notification message with the Admin Status TLV.

   o   Upon receiving the Admin Status TLV with the Delete (D) bit set
       in the Notification message, the egress SHOULD respond with a
       LABEL WITHDRAW message and normal CR-LDP processing takes place.

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

   o   The egress node indicates its desire for deletion by inserting an
       Admin Status TLV in a Notification message and setting Delete (D)
       bit.

   o   Transit nodes process the Admin Status TLV as described above.

   o   Upon receiving the Admin Status TLV with the Delete (D) bit set
       in the Notification message, the ingress node sends a LABEL
       RELEASE message downstream to remove the LSP and normal CR-LDP
       processing takes place.

7.3. Notification Message Procedures

   Subsequent messaging Admin Status messaging may be performed by
   Notification Messages.  The ingress may begin the propagation of a
   Notification Message with an Admin Status TLV.  Each subsequent node
   propagates the Notification with the Admin Status TLV from the
   ingress to the egress and then the egress node returns the
   Notification messages back Upstream carrying the Admin Status TLV.

   Intermediate and egress nodes may trigger the setting of
   administrative status via the use of Notification messages.  To
   accomplish this, an intermediate or egress node generates a
   Notification message with the corresponding upstream notify session
   information.  The Admin Status TLV MUST be included in the session
   information, with the appropriate bit or bits set.  The Reflect (R)
   bit MUST NOT be set.

   An ingress or egress node receiving a Notification message containing
   an Admin Status TLV with the Delete (D) bit set, SHOULD initiate the
   deletion procedure described in the previous section.

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 TLV and other error
   conditions.  Specifically, a node that sends a Notification message
   containing an Admin Status TLV with the Down (D) bit set MUST verify
   that it receives a corresponding LABEL RELEASE message within a
   configurable period of time.  By default this period of time SHOULD
   be 30 seconds.  If the node does not receive such a LABEL RELEASE
   message, it SHOULD send a Label Release message downstream and a
   LABEL WITHDRAW message 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 REQUEST message.  The choice of the data interface is
   indicated by the sender of the REQUEST message by including the data
   channel's interface identifier in the message using a new Interface
   TLV 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
   REQUEST sender explicitly identifies the component interface used in
   each direction.

8.1.1. Interface ID TLV

   The format of IPV4 Interface ID  in REQUEST, MAPPING Messages 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x082d)         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 IPv4 Next/Previous Hop Address                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Logical Interface ID                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Interface ID TLVS see [RFC3471]                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of IPV6 Interface ID TLV in REQUEST, MAPPING Messages 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x082e)         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 IPv6 Next/Previous Hop Address                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Logical Interface ID                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Interface ID TLVS see [RFC3471]                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   See [RFC3471] for a description of parameters.

   See [RFC3212] for a description of signaling address.  See [RFC3471]
   for a description of parameters and encoding of TLVs.

8.1.2. Procedures

   An IF_ID TLV is used on links where there is not a one-to-one
   association of a control channel to a data channel, see [RFC3471].

   The LDP session uses the IF_ID TLV to identify the data channel(s)
   associated with the 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 a REQUEST message.  The IF_ID TLV SHOULD
   NOT be used when no TLVs are needed.

   A node receiving one or more IF_ID TLVs in a REQUEST message saves
   their values and returns them in the subsequent MAPPING message sent
   to the node that originated the TLVs.

   Note, the node originating an IF_ID TLV MUST ensure that the selected
   outgoing interface, as specified in the IF_ID TLV, is consistent with
   an ERO.  A node that receives an IF_ID TLV SHOULD check whether the
   information carried in this TLV is consistent with the information
   carried in a received ERO, and if not it MUST send a LABEL ABORT
   Message with the error code "Routing Error" and error value of "Bad
   Explicit Routing TLV Error" 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 Status
   TLV are defined.

8.2.1. IF_ID Status TLVs

   The format of the IPv4 IF_ID Status TLV 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x082f)         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 IPv4 Next/Previous Hop Address                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Status Code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              TLVs                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The format of the IPv6 IF_ID Status TLV 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|F|     Type (0x0830)         |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                     IPv6 Error Node Address                   |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Status Code                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                              TLVs                             ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   See [RFC3036] for a description of status code 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 Status TLV in the
   corresponding LABEL WITHDRAW or LABEL RELEASE message.  IF_ID Status
   TLV SHOULD be generated and processed as any other Status TLV, see
   [RFC3036].

9. Fault Handling

   In optical transport networks, failures in the out-of-fiber signaling
   communication or optical control plane should not have service impact
   on the existing optical connections.  Under such circumstances, a
   mechanism MUST exist to detect a signaling communication failure and
   a recovery procedure SHALL guarantee connection integrity at both
   ends of the signaling channel.

   The LDP Fault tolerant document [LDP-FT] specifies the procedures for
   recovering LDP and CR-LDP sessions under failure.  Please refer to
   his document for procedures on recovering optical connections.
   Currently the Fault tolerant document covers many of the common
   failure modes for a separated control and data plane.

10. Acknowledgments

   This document is the work of numerous authors and consists of a
   composition of a number of previous documents in this area.

   Valuable comments and input were received from a number of people,
   notably Adrian Farrel.

11. Security Considerations

   This document introduces no new security considerations to [RFC3212].

12. IANA Considerations

   This document uses the LDP [RFC3036] name spaces, see
   http://www.iana.org/assignments/ldp-namespaces, which lists the
   assignments for the following TLVs:

   o Generalized Label Request (TLV 0x0824)
   o Generalized Label (TLV 0x0825)
   o Upstream Label (TLV 0x0826)
   o Label Set (TLV 0x0827)
   o Waveband Label (TLV 0x0828)
   o ER-Hop (TLV 0x0829)
   o Acceptable Label Set (TLV 0x082a)
   o Admin Status (TLV 0x082b)
   o Interface ID (TLV 0x082c)
   o IPV4 Interface ID (TLV 0x082d)
   o IPV6 Interface ID (TLV 0x082e)
   o IPv4 IF_ID Status (TLV 0x082f)
   o IPv6 IF_ID Status (TLV 0x0830)
   o Protection (TLV 0x0835)

13. Intellectual Property Considerations

   This section is taken from Section 10.4 of [RFC2026].

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

14. References

14.1. Normative References

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

   [RFC3036]        Andersson, L., Doolan, P., Feldman, N., Fredette, A.
                    and B. Thomas, "LDP Specification", RFC 3036,
                    January 2001.

   [RFC3212]        Jamoussi, B., Andersson, L., Callon, R., Dantu, R.,
                    Wu, L., Doolan, P., Worster, T., Feldman, N.,
                    Fredette, A., Girish, M., Gray, E., Heinanen, J.,
                    Kilty, T. and A. Malis, "Constraint-Based LSP Setup
                    using LDP", RFC 3212, January 2002.

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

14.2. Informative References

   [LDP-FT]         Farrel, A., et al, "Fault Tolerance for LDP and CR-
                    LDP", Work in Progress.

   [MPLS-HIERARCHY] Kompella, K. and Y. Rekhter, "LSP Hierarchy with
                    MPLS TE", Work in Progress.

   [MPLS-UNNUM]     Kompella, K., Rekhter, Y. and A. Kullberg,
                    "Signalling Unnumbered Links in CR-LDP", Work in
                    Progress.

   [RFC2026]        Bradner, S., "The Internet Standards Process --
                    Revision 3," BCP 9, RFC 2026, October 1996.

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

15. Contributors

   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


   Ayan Banerjee
   Calient Networks
   5853 Rue Ferrari
   San Jose, CA 95138

   Phone:  +1 408 972-3645
   EMail:  abanerjee@calient.net
   Lou Berger
   Movaz Networks, Inc.
   7926 Jones Branch Drive
   Suite 615
   McLean VA, 22102

   Phone:  +1 703 847-1801
   EMail:  lberger@movaz.com


   Greg Bernstein
   EMail:  gregb@grotto-networking.com


   Yanhe Fan
   Axiowave Networks, Inc.
   200 Nickerson Road
   Marlborough, MA 01752

   Phone: + 1 774 348 4627
   EMail: yfan@axiowave.com


   Don Fedyk
   Nortel Networks Corp.
   600 Technology Park
   Billerica  MA 01821

   Phone:  +1 978 288 3041
   Fax:    +1 978 288 0620
   EMail:  dwfedyk@nortelnetworks.com


   Jonathan P. Lang
   EMail:  jplang@ieee.org


   Eric Mannie
   Independent Consultant
   2 Avenue de la Folle Chanson
   1050 Brussels
   Belgium

   EMail:  eric_mannie@hotmail.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


   Debanjan Saha
   EMail:  debanjan@acm.org


   Vishal Sharma
   Metanoia, Inc.
   1600 Villa Street, Unit 352
   Mountain View, CA 94041-1174

   Phone:  +1 650-386-6723
   EMail:  v.sharma@ieee.org


   George Swallow
   Cisco Systems, Inc.
   250 Apollo Drive
   Chelmsford, MA 01824

   Phone:  +1 978 244 8143
   EMail:  swallow@cisco.com


   Z. Bo Tang
   EMail:  botang01@yahoo.com

16. Editors' 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


   Lou Berger
   Movaz Networks, Inc.
   7926 Jones Branch Drive
   Suite 615
   McLean VA, 22102

   Phone:  +1 703 847-1801
   EMail:  lberger@movaz.com

17.  Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.