MPLS WG Working Group                               Bilel Jamoussi, Editor
Internet Draft                                    Nortel Networks Corp.
Expiration Date: February March 2000
                                                            August
                                                         September 1999

                  Constraint-Based LSP Setup using LDP

                     draft-ietf-mpls-cr-ldp-02.txt

                     draft-ietf-mpls-cr-ldp-03.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Abstract

   Label Distribution Protocol (LDP) is defined in [1] for distribution
   of labels inside one MPLS domain.  One of the most important
   services that may be offered using MPLS in general and LDP in
   particular is support for constraint-based routing of traffic across
   the routed network. Constraint-based routing offers the opportunity
   to extend the information used to setup paths beyond what is
   available for the routing protocol. For instance, an LSP can be
   setup based on explicit route constraints, QoS constraints, and
   other constraints. Constraint-based routing (CR) is a mechanism used
   to meet Traffic Engineering requirements that have been proposed by
   [2], [3] and [4]. These requirements may be met by extending LDP for
   support of constraint-based routed label switched paths (CRLSPs). (CR-LSPs).
   Other uses exist for CRLSPs as well ([5], [6] and [7]). CR-LSPs include MPLS-based VPNs.

   This draft specifies mechanisms and TLVs for support of CRLSPs CR-LSPs
   using LDP. The Explicit Route object and procedures are extracted from
   [8].

Table of Contents

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   Table of Contents

   1. Introduction....................................................3
   2. Constraint-based Routing Overview...............................3
   2.1 Strict and Loose Explicit Routes...............................3 Routes...............................4
   2.2 Traffic Characteristics........................................4
   2.3 Pre-emption....................................................4 Pre-emption....................................................5
   2.4 Route Pinning..................................................5
   2.5 Resource Class.................................................5
   3. Solution Overview...............................................5 Overview...............................................6
   3.1 Required Messages and TLVs.....................................6 TLVs.....................................7
   3.2 Label Request Message..........................................7
   3.3 Label Mapping Message..........................................7 Message..........................................8
   3.4 Notification Message...........................................8
   3.5 Release , Withdraw, and Abort Messages.........................9
   4. Protocol Specification..........................................9
   4.1 Explicit Route TLV (ER-TLV)....................................9 (ER-TLV)...................................10
   4.2 Explicit Route Hop TLV (ER-Hop TLV)...........................10
   4.3 Traffic Parameters TLV........................................11
   4.3.1 Semantics...................................................13
   4.3.1.1 Frequency.................................................13
   4.3.1.2 Peak Rate.................................................13
   4.3.1.3 Committed Rate............................................13 Rate............................................14
   4.3.1.4 Excess Burst Size.........................................14
   4.3.1.5 Peak Rate Token Bucket....................................14
   4.3.1.6 Committed Data Rate Token Bucket..........................14
   4.3.1.7 Weight....................................................15
   4.3.2 Procedures..................................................15
   4.3.2.1 Label Request Message.....................................15
   4.3.2.2 Label Mapping Message.....................................16
   4.3.2.3 Notification Message......................................16
   4.4 Preemption TLV................................................16
   4.5 LSPID TLV.....................................................17
   4.6 Resource Class (Color) TLV....................................18
   4.7 ER-Hop semantics..............................................19
   4.7.1. ER-Hop 1: The IPv4 prefix..................................19
   4.7.2. ER-Hop 2: The IPv6 address.................................19 address.................................20
   4.7.3. ER-Hop 3:  The autonomous system number....................20
   4.7.4. ER-Hop 4: LSPID............................................20 LSPID............................................21
   4.8. Processing of the Explicit Route TLV.........................22
   4.8.1. Selection of the next hop..................................22
   4.8.2. Adding ER-Hops to the explicit route TLV...................23
   4.9 Route Pinning TLV.............................................23 TLV.............................................24
   4.10 CRLSP CR-LSP FEC Element............................................24 Element...........................................24
   4.11 Error subcodes...............................................24 subcodes...............................................25
   5. Security.......................................................25
   6. Acknowledgments................................................25
   7. Intellectual Property Consideration............................25 Consideration............................26
   8. References.....................................................25 References.....................................................26
   9. Author's Addresses.............................................26
   Appendix A: CRLSP CR-LSP Establishment Examples..........................29
   A.1 Strict Explicit Route Example.................................29
   A.2. Node Groups and Specific Nodes Example.......................30 Examples.........................29

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   A.1 Strict Explicit Route Example.................................29
   A.2 Node Groups and Specific Nodes Example........................30
   Appendix B. QoS Service Examples..................................33
   B.1 Service Examples..............................................33
   B.2.
   B.2 Establishing CR-LSP Supporting Real-Time Applications........34
   B.3. Applications.........34
   B.3 Establishing CR-LSP Supporting Delay Insensitive Applications35 Applications.35
   Appendix C. LSP Modification Using CR-LDP.........................36
   C.1 Introduction..................................................36
   C.2 Basic Procedure...............................................37
   C.3 Priority Handling.............................................38
   C.4 Modification Failure Case Handling............................39

1. Introduction

   The need for constraint-based routing (CR) in MPLS has been explored
   elsewhere [3], [2], and [4].  Explicit routing is a subset of the
   more general constraint-based routing function. At the MPLS WG
   meeting held during the Washington IETF (December 1997) there was
   consensus that LDP should support explicit routing of LSPs with
   provision for indication of associated (forwarding) priority.  In
   the Chicago meeting (August 1998), a decision was made that support
   for explicit path setup in LDP will be moved to a separate document.
   This document provides that support and it has been accepted as a
   working document in the Orlando meeting (December 1998).

   This specification proposes an end-to-end setup mechanism of a
   constraint-based routed LSP (CRLSP) (CR-LSP) initiated by the ingress LSR.
   We also specify mechanisms to provide means for reservation of
   resources using LDP.

   This document introduce TLVs and procedures that provide support
   for:
        - Strict and Loose Explicit Routing
        - Specification of Traffic Parameters
        - Route Pinning
        - CRLSP CR-LSP Pre-emption though setup/holding priorities
        - Handling Failures
        - LSPID
        - Resource Class

   Section 2 introduces the various constraints defined in this
   specification. Section 3 outlines the CR-LDP solution. Section 4
   defines the TLVs and procedures used to setup constraint-based
   routed label switched paths.  Appendix A provides several examples
   of CR-LSP path setup. Appendix B provides Service Definition
   Examples.

2. Constraint-based Routing Overview

   Constraint-based routing is a mechanism that supports the Traffic
   Engineering requirements defined in [4]. Explicit Routing is a
   subset of the more general constraint-based routing where the

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   constraint is the explicit route (ER). Other constraints are defined
   to provide a network operator with control over the path taken by an
   LSP. This section is an overview of the various constraints
   supported by this specification.

2.1 Strict and Loose Explicit Routes

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   Like any other LSP an CRLSP a CR-LSP is a path through an MPLS network. The
   difference is that while other paths are setup solely based on
   information in routing tables or from a management system, the
   constraint-based route is calculated at one point at the edge of
   network based on criteria, including but not limited to routing
   information. The intention is that this functionality shall give
   desired special characteristics to the LSP in order to better
   support the traffic sent over the LSP. The reason for setting up
   CRLSPs, CR-
   LSPs might be that one wants to assign certain bandwidth or other
   Service Class characteristics to the LSP, or that one wants to make
   sure that alternative routes use physically separate paths through
   the network.

   An explicit route is represented in a Label Request Message as a
   list of nodes or groups of nodes along the constraint-based route.
   When the CRLSP CR-LSP is established, all or a subset of the nodes in a
   group may be traversed by the LSP.  Certain operations to be
   performed along the path can also be encoded in the constraint-based
   route.

   The capability to specify, in addition to specified nodes, groups of
   nodes, of which a subset will be traversed by the CRLSP, CR-LSP, allows the
   system a significant amount of local flexibility in fulfilling a
   request for a constraint-based route.  This allows the generator of
   the constraint-based route to have some degree of imperfect
   information about the details of the path.

   The constraint-based route is encoded as a series of ER-Hops
   contained in a constraint-based route TLV.  Each ER-Hop may identify
   a group of nodes in the constraint-based route. A constraint-based
   route is then a path including all of the identified groups of
   nodes. nodes
   in the order in which they appear in the TLV.

   To simplify the discussion, we call each group of nodes an abstract
   node.  Thus, we can also say that a constraint-based route is a path
   including all of the abstract nodes, with the specified operations
   occurring along that path.

2.2 Traffic Characteristics

   The traffic characteristics of a path are described in the Traffic
   Parameters TLV in terms of a peak rate, committed rate, and service
   granularity. The peak and committed rates describe the bandwidth
   constraints of a path while the service granularity can be used to

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   specify a constraint on the delay variation that the CRLDP CR-LDP MPLS
   domain may introduce to a path's traffic.

2.3 Pre-emption

   CR-LDP signals the resources required by a path on each hop of the
   route. If a route with sufficient resources can not be found,
   existing paths may be rerouted to reallocate resources to the new

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   path. This is the process of path pre-emption. Setup and holding
   priorities are used to rank existing paths (holding priority) and
   the new path (setup priority) to determine if the new path can pre-
   empt an existing path.

   The setupPriority of a new CRLSP CR-LSP and the holdingPriority attributes
   of the existing CRLSP CR-LSP are used to specify priorities. Signaling a
   higher holding priority express that the path, once it has been
   established, should have a lower chance of being pre-empted.
   Signaling a higher setup priority expresses the expectation that, in
   the case that resource are unavailable, the path is more likely to
   pre-empt other paths. The exact rules determining bumping are an
   aspect of network policy.

   The allocation of setup and holding priority values to paths is an
   aspect of network policy.

   The setup and holding priority values range from zero (0) to seven
   (7). The value zero (0) is the priority assigned to the most
   important path. It is referred to as the highest priority. Seven (7)
   is the priority for the least important path. The use of default
   priority values is an aspect of network policy.

   The setupPriority of a CRLSP CR-LSP should not be higher (numerically
   less) than its holdingPriority since it might bump an LSP and be
   bumped by the next _equivalent_ request.

2.4 Route Pinning

   Route pinning is applicable to segments of an LSP that are loosely
   routed - i.e. those segments which are specified with a next hop
   with the `L' bit set or where the next hop is an _abstract node_.  A
   CRLSP
   CR-LSP may be setup using route pinning if it is undesirable to
   change the path used by an LSP because even when a better next hop becomes
   available at some LSR along the loosely routed portion of the LSP.

2.5 Resource Class

   The network operator may classify network resources in various ways.
   These classes are also known as _colors_ or _administrative groups_.
   When an a CR-LSP is being established, it's necessary to indicate which
   resource classes the CR-LSP can draw from.

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3. Solution Overview

   CRLSP

   CR-LSP over LDP Specification is designed with the following goals:

        1. Meet the requirements outlined in [4] for performing traffic
           engineering and provide a solid foundation for performing
           more general constraint-based routing.

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        2. Build on already specified functionality that meets the
           requirements whenever possible. Hence, this specification is
           based on [1] and the Explicit Route object and procedures
           defined in [8]. [1].

        3. Keep the solution simple.

   In this document, support for unidirectional point-to-point CRLSPs CR-LSPs
   is specified. Support for point-to-multipoint, multipoint-to-point,
   is for further study (FFS).

   Support for constraint-based routed LSPs in this specification
   depends on the following minimal LDP behaviors as specified in [1]:

     -  Use of Basic and/or Extended Discovery Mechanisms.
     -  Use of the Label Request Message defined in [1] in downstream
        on demand label advertisement mode with ordered control.
     -  Use of the Label Mapping Message defined in [1] in downstream
        on demand mode with ordered control.
     -  Use of the Notification Message defined in [1].
     -  Use of the Withdraw and Release Messages defined in [1].
     -  Use of the Loop Detection (in the case of loosely routed
        segments of a CRLSP) CR-LSP) mechanisms defined in [1].

   In addition, the following functionality is added to what's defined
   in [1]:

     -  The Label Request Message used to setup a CRLSP CR-LSP includes one
        or more CR-TLVs defined in Section 4. For instance, the Label
        Request Message may include the ER-TLV.
     -  An LSR implicitly infers ordered control from the existence of
        one or more CR-TLVs in the Label Request Message. This means
        that the LSR can still be configured for independent control
        for LSPs established as a result of dynamic routing. However,
        when a Label Request Message includes one or more of the CR-
        TLVs, then ordered control is used to setup the CRLSP. CR-LSP. Note
        that this is also true for the loosely routed parts of a CRLSP. CR-
        LSP.
     -  New status codes are defined to handle error notification for
        failure of established paths specified in the CR-TLV. CR-TLVs.

   Optional TLVs are not required in the CR-LDP messages for the
   messages to be compliant with the protocol.  Optional parameters CAN MAY
   be required for a particular operation to work (or work correctly),
   however.

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   Examples of CRLSP CR-LSP establishment are given in Appendix A to
   illustrate how the mechanisms described in this draft work.

3.1 Required Messages and TLVs

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   Any Messages, TLVs, and procedures not defined explicitly in this
   document are defined in the LDP Specification [1]. The state
   transitions, which relate to CR-LDP messages, can be found in [9]. [5].
   The following subsections are meant as a cross-reference to the [1]
   document and indication of additional functionality beyond what's
   defined in [1] where necessary.

3.2 Label Request Message

   The Label Request Message is as defined in 3.5.8 of [1] with the
   following modifications (required only if any of the CR-TLVs is
   included in the Label Request Message):

     -  Only a single FEC-TLV may be included in the Label Request
        Message. The CR-LSP FEC TLV should be used.

     -  The Optional Parameters TLV includes the definition of any of
        the Constraint-based TLVs specified in Section 4.

     -  The Procedures to handle the Label Request Message are
        augmented by the procedures for processing of the CR-TLVs as
        defined in Section 4.

   The encoding for the CR-LDP Label Request Message is as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Label Request (0x0401)   |      Message Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     FEC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID TLV  (mandatory)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     LSPID TLV            (CR-LDP, mandatory)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     ER-TLV               (CR-LDP, optional)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Traffic  TLV         (CR-LDP, optional)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Pinning TLV          (CR-LDP, optional)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Resource Class TLV (CR-LDP, optional)     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Pre-emption  TLV     (CR-LDP, optional)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.3 Label Mapping Message

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3.3 Label Mapping Message

   The Label Mapping Message is as defined in 3.5.7 of [1] with the
   following modifications:

     -  Only a single Label-TLV may be included in the Label Mapping
        Message.

     -  The Label Mapping Message Procedures are limited to downstream
        on demand ordered control mode.

   A Mapping message is transmitted by a downstream LSR to an upstream
   LSR under one of the following conditions:

        1. The LSR is the egress end of the CRLSP CR-LSP and an upstream
           mapping has been requested.

        2. The LSR received a mapping from its downstream next hop LSR
           for an CRLSP CR-LSP for which an upstream request is still
           pending.

   The encoding for the CR-LDP Label Mapping Message is as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Label Mapping (0x0400)   |      Message Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     FEC TLV                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Label TLV                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Label Request Message ID TLV                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     LSPID TLV            (CR-LDP, optional)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Traffic  TLV         (CR-LDP, optional)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.4 Notification Message

   The Notification Message is as defined in Section 3.5.1 of [1] and
   the Status TLV encoding is as defined in Section 3.4.7 3.4.6 of [1].
   Establishment of an Explicitly Routed LSP CR-LSP may fail for a variety of reasons.  All
   such failures are considered advisory conditions and they are
   signaled by the Notification Message.

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   Notification Messages carry Status TLVs to specify events being
   signaled. New status codes are defined in Section 4.11 to signal
   error notifications associated with the establishment of a CRLSP CR-LSP
   and the processing of the CR-TLV.

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   The Notification Message must may carry the LSPID TLV of the
   corresponding CRLSP. CR-LSP.

   Notification Messages MUST be forwarded toward the LSR originating
   the Label Request at each hop and at any time that procedures in
   this specification - or in [1] - specify sending of a Notification
   Message in response to a Label Request Message.

   The encoding of the notification message is as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|   Notification (0x0001)     |      Message Length           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Message ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Status (TLV)                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Optional Parameters                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.5 Release , Withdraw, and Abort Messages

   The Label Release , Label Withdraw, and Label Abort Request Messages
   are used as specified in [1]. These messages may also carry the
   LSPID TLV.

4. Protocol Specification

   The Label Request Messages Message defined in [1] optionally carries one or
   more of the optional Constraint-based Routing TLVs (CR-TLVs) defined
   in this section. If needed, other constraints can be supported later
   through the definition of new TLVs. In this specification, the
   following TLVs are defined:

     -  Explicit Route TLV
     -  Explicit Route Hop TLV
     -  Traffic Parameters TLV
     -  Preemption TLV
     -  LSPID TLV
     -  Route Pinning TLV
     -  Resource Class TLV
     -  CRLSP  CR-LSP FEC TLV

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4.1 Explicit Route TLV (ER-TLV)

   The ER-TLV is an object that specifies the path to be taken by the
   LSP being established. It is composed of one or more Explicit Route
   Hop TLVs (ER-Hop TLVs) defined in Section 4.2.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|         ER-TLV  (0x0800)  |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ER-Hop TLV 1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ER-Hop TLV 2                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                          ............                         ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ER-Hop TLV n                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A two-byte field carrying the value of the ER-TLV type whichis
        0x800.

   Length
        Specifies the length of the value field in bytes.

   ER-Hop TLVs
        One or more ER-Hop TLVs defined in Section 4.2.

4.2 Explicit Route Hop TLV (ER-Hop TLV)

   The contents of an ER-TLV are a series of variable length ER-Hop
   TLVs.

   A node receiving a label request message including an ER-Hop type
   that is not supported should not progress the label request message
   to the downstream LSR and should send back a _No Route_ Notification
   Message.

   Each ER-Hop TLV has the form:

   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|          ER-Hop-Type      |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|                                  Content //                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   ER-Hop Type

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        A fourteen-bit field indicating the type of contents of the ER-
        Hop. Currently defined values are:

        Value Type
         ----- ------------------------
        0x801 IPv4 prefix
        0x802 IPv6 prefix

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        0x803 Autonomous system number
        0x804 LSPID

   Length
        Specifies the length of the value field in bytes.

   L bit
        The L bit is an attribute of the ER-Hop. The L bit is set if
        the ER-Hop ER-Hop represents a loose hop in the explicit route.
        If the bit is not set, the ER-Hop represents a strict hop in
        the explicit route.

        The L bit in the ER-Hop is a one-bit attribute.  If the L bit
        is set, then the value of the attribute is _loose._  Otherwise,
        the value of the attribute is _strict._  For brevity, we say
        that if the value of the ER-Hop attribute is loose then it is a
        _loose ER-Hop._  Otherwise, it's a _strict ER-Hop._  Further,
        we say that the abstract node of a strict or loose ER-Hop is a
        strict or a loose node, respectively.  Loose and strict nodes
        are always interpreted relative to their prior abstract nodes.
        The path between a strict node and its prior node MUST include
        only network nodes from the strict node and its prior abstract
        node.

        The path between a loose node and its prior node MAY include
        other network nodes, which are not part of the strict node or
        its prior abstract node.

   Contents
        A variable length field containing the a node or abstract node
        that
        which is one of the consecutive nodes that make up the explicit
        explicitly routed LSP.

4.3 Traffic Parameters TLV

   The following sections describe the CRLSP CR-LSP Traffic Parameters.  The
   required characteristics of a CRLSP CR-LSP are expressed by the Traffic
   Parameter values.

   A Traffic Parameters TLV, is used to signal the Traffic Parameter
   values. The Traffic Parameters are defined in the subsequent
   sections.

   The Traffic Parameters TLV contains a Flags field, a Frequency, a
   Weight, and the five Traffic Parameters PDR, PBS, CDR, CBS, EBS.
   The Traffic Parameters TLV is shown below:

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0| Traf. Param. TLV  (0x0810)|      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Flags     |    Frequency  |     Reserved  |    Weight     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Peak Data Rate (PDR)                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Peak Burst Size (PBS)                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Committed Data Rate (CDR)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Committed Burst Size (CBS)                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Excess Burst Size (EBS)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ER-TLV type
        which is 0x810.

   Length
        Specifies the length of the value field in bytes.

   Flags
        The Flags field is shown below:

         +--+--+--+--+--+--+--+--+
         | Res |F6|F5|F4|F3|F2|F1|
         +--+--+--+--+--+--+--+--+

        Res - These bits are reserved.
        Zero on transmission.
        Ignored on receipt.
        F1 - Corresponds to the PDR.
        F2 - Corresponds to the PBS.
        F3 - Corresponds to the CDR.
        F4 - Corresponds to the CBS.
        F5 - Corresponds to the EBS.
        F6 - Corresponds to the Weight.

        Each flag Fi is a Negotiable Flag corresponding to a Traffic
        Parameter. The Negotiable Flag value zero denotes NotNegotiable
        and value one denotes Negotiable.

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   Frequency
        The Frequency field is coded as an 8 bit unsigned integer with
        the following code points defined:

        0- Unspecified
        1- Frequent

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        2- VeryFrequest VeryFrequent
        3-255  - Reserved
        Reserved - Zero on transmission.  Ignored on receipt.

   Weight
        An 8 bit unsigned integer indicating the weight of the CRLSP. CR-LSP.
        Valid weight values are from 1 to 255.  The value 0 means that
        weight is not applicable for the CRLSP. CR-LSP.

   Traffic Parameters
        Each Traffic Parameter is encoded as a 32-bit IEEE single-
        precision floating-point number.  A value of positive infinity
        is represented as an IEEE single-precision floating-point
        number with an exponent of all ones (255) and a sign and
        mantissa of all zeros. The values PDR and CDR are in units of
        bytes per second. The values PBS, CBS and EBS are in units of
        bytes.

        The value of PDR MUST be greater than or equal to the value of
        CDR in a correctly encoded Traffic Parameters TLV.

4.3.1 Semantics

4.3.1.1 Frequency

   The Frequency specifies at what granularity the CDR allocated to the
   CRLSP
   CR-LSP is made available.  The value VeryFrequently VeryFrequent means that the
   available rate should average at least the CDR when measured over
   any time interval equal to or longer than the shortest packet time
   at the CDR.  The value Frequently Frequent means that the available rate should
   average at least the CDR when measured over any time interval equal
   to or longer than a small number of shortest packet times at the
   CDR.

   The value Unspecified means that the CDR MAY be provided at any
   granularity.

4.3.1.2 Peak Rate

   The Peak Rate defines the maximum rate at which traffic SHOULD be
   sent to the CRLSP. CR-LSP. The Peak Rate is useful for the purpose of
   resource allocation. If resource allocation within the MPLS domain
   depends on the Peak Rate value then it should be enforced at the
   ingress to the MPLS domain.

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   The Peak Rate is defined in terms of the two Traffic Parameters PDR
   and PBS, see section 4.3.1.5 below.

4.3.1.3 Committed Rate

   The Committed Rate defines the rate that the MPLS domain commits to
   be available to the CRLSP.

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   The Committed Rate is defined in terms of the two Traffic Parameters
   CDR and CBS, see section 4.3.1.6 below.

4.3.1.4 Excess Burst Size

   The Excess Burst Size may be used at the edge of an MPLS domain for
   the purpose of traffic conditioning. The EBS MAY be used to measure
   the extent by which the traffic sent on a CRLSP CR-LSP exceeds the
   committed rate.

   The possible traffic conditioning actions, such as passing, marking
   or dropping, are specific to the MPLS domain.

   The Excess Burst Size is defined together with the Committed Rate,
   see section 4.3.1.6 below.

4.3.1.5 Peak Rate Token Bucket

   The Peak Rate of a CRLSP CR-LSP is specified in terms of a token bucket P
   with token rate PDR and maximum token bucket size PBS.

   The token bucket P is initially (at time 0) full, i.e., the token
   count Tp(0) = PBS.  Thereafter, the token count Tp, if less than
   PBS, is incremented by one PDR times per second. When a packet of
   size B bytes arrives at time t, the following happens:

     -  If Tp(t)-B >= 0, the packet is not in excess of the peak  rate
        and Tp is decremented by B down to the minimum value of 0, else

     -  the packet is in excess of the peak rate and Tp is not
        decremented.

   Note that according to the above definition, a positive infinite
   value of either PDR or PBS implies that arriving packets are ever never
   in excess of the peak rate.

   The actual implementation of a an LSR doesn't need to be modeled
   according to the above formal token bucket specification.

4.3.1.6 Committed Data Rate Token Bucket

   The committed rate of a CRLSP CR-LSP is specified in terms of a token
   bucket C with rate CDR.  The extent by which the offered rate
   exceeds the committed rate MAY be measured in terms of another token

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   bucket E, which also operates at rate CDR.  The maximum size of the
   token bucket C is CBS and the maximum size of the token bucket E is
   EBS.

   The token buckets C and E are initially (at time 0) full, i.e., the
   token count Tc(0) = CBS and the token count Te(0) = EBS.
   Thereafter, the token counts Tc and Te are updated CDR times per
   second as follows:

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     -  If Tc is less than CBS, Tc is incremented by one, else
     -  if Te is less then EBS, Te is incremented by one, else
     -  neither Tc nor Te is incremented.

   When a packet of size B bytes arrives at time t, the following
   happens:

     -  If Tc(t)-B >= 0, the packet is not in excess of the Committed
        Rate and Tc is decremented by B down to the minimum value of 0,
        else
     -  if Te(t)-B >= 0, the packet is in excess of the Committed rate
        but is not in excess of the EBS and Te is decremented by B down
        to the minimum value of 0, else
     -  the packet is in excess of both the Committed Rate and the EBS
        and neither Tc nor Tc Te is decremented.

   Note that according to the above specification, a CDR value of
   positive infinity implies that arriving packets are never in excess
   of either the Committed Rate or EBS. A positive infinite value of
   either CBS or EBS implies that the respective limit cannot be
   exceeded.

   The actual implementation of a an LSR doesn't need to be modeled
   according to the above formal specification.

4.3.1.7 Weight

   The weight determines the CRLSP's CR-LSP's relative share of the possible
   excess bandwidth above its committed rate.  The definition of
   _relative share_ is MPLS domain specific.

4.3.2 Procedures

4.3.2.1 Label Request Message

   If an LSR receives an incorrectly encoded Traffic Parameters TLV in
   which the value of PDR is less than the value of CDR then it MUST
   send a Notification Message including the Status code Traffic _Traffic
   Parameters Unavailable Unavailable_ to the upstream LSR from which it received
   the erroneous message.

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   If a Traffic Parameter is indicated as Negotiable in the Label
   Request Message by the corresponding Negotiable Flag then an LSR MAY
   replace the Traffic Parameter value with a smaller value.

   If the Weight is indicated as Negotiable in the Label Request
   Message by the corresponding Negotiable Flag then an LSR may adjust replace
   the Weight value with a lower value (down to 0).

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   If, after possible Traffic Parameter negotiation, an LSR can support
   the CRLSP CR-LSP Traffic Parameters then the LSR MUST reserve the
   corresponding resources for the CRLSP. CR-LSP.

   If, after possible Traffic Parameter negotiation, an LSR cannot
   support the CRLSP CR-LSP Traffic Parameters then the LSR MUST send a
   notification message
   Notification Message that contains the Resource Unavailable _Resource Unavailable_ status
   code.

4.3.2.2 Label Mapping Message

   If an LSR receives an incorrectly encoded Traffic Parameters TLV in
   which the value of PDR is less than the value of CDR then it MUST
   send a Label Release message containing the Status code Traffic _Traffic
   Parameters Unavailable Unavailable_ to the LSR from which it received the
   erroneous message. In addition, the LSP should send a Notification
   Message upstream with the status code _Label Request Aborted_.

   If the negotiation flag was set in the label request message, the
   egress LSR MUST include the (possibly negotiated) Traffic Parameters
   and Weight in the Label Mapping message.

   The Traffic Parameters and the Weight in a Label Mapping message
   MUST be forwarded unchanged.

   An LSR SHOULD adjust the resources that it reserved for a CRLSP CR-LSP
   when it receives a Label Mapping Message if the Traffic Parameters
   differ from those in the corresponding Label Request Message.

4.3.2.3 Notification Message

   If an LSR receives a Notification Message for a CRLSP, CR-LSP, it SHOULD
   release any resources that it possibly had reserved for the CRLSP. CR-LSP.
   In addition, on receiving a Notification Message from a Downstream
   LSR that is associated with a Label Request from an upstream LSR,
   the local LSR MUST propagate the Notification message using the
   procedures in [1].

4.4 Preemption TLV

   The defualt value of the setup and holding priorities should be in
   the middle of the range (e.g., 4) so that this feature can be turned
   on gradually in an operational network by increasing or decerasing
   the priority starting at the middle of the range.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0| Preemption-TLV  (0x0820)  |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  SetPrio      | HoldPrio      |      Reserved                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Type
        A fourteen-bit field carrying the value of the Preemption-TLV
        type which is 0x810. 0x820.

   Length
        Specifies the length of the value field in bytes.

   Reserved
        Zero on transmission.  Ignored on receipt.

   SetPrio
        A SetupPriority of value zero (0) is the priority assigned to
        the most important path. It is referred to as the highest
        priority.  Seven (7) is the priority for the least important
        path. The higher the setup priority, the more paths CR-LDP can
        bump to set up the path. The default value should be 4.

   HoldPrio
        A HoldingPriority of value zero (0) is the priority assigned to
        the most important path. It is referred to as the highest
        priority. Seven (7) is the priority for the least important
        path. The default value should be 4.
        The higher the holding priority, the less likely it is for CR-
        LDP to reallocate its bandwidth to a new path.

4.5 LSPID TLV

   LSPID is a unique identifier of a CRLSP CR-LSP within an MPLS network.

   The LSPID is composed of the ingress LSR Router ID (or any of its
   own Ipv4 addresses) and a Locally unique CRLSP CR-LSP ID to that LSR.

   The LSPID is useful in network management, in CR-LSP repair, and in
   using an already established CR-LSP as a hop in an ER-TLV.

   An action _action indicator flag_ is carried in the LSPID TLV. This _action
   indicator flag_ indicates explicitly the action that should be taken
   if the LSP already exists on the LSR receiving the message.

   After a CR-LSP is set up, its bandwidth reservation may need to be
   changed by the network operator, due to the new requirements for the
   traffic carried on that CR-LSP. The _action indicator flag_ is used

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   indicate the need to modify the bandwidth and possibly other
   parameters of an established CR-LSP without service interruption.
   This feature has application in dynamic network resources management
   where traffic of different priorities and service classes is
   involved.

   The procedure for the code point _modify_ is defined in section 2.1.
   of [10]. Appendix C.
   The procedures for other flags are FFS.

   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|      LSPID-TLV  (0x0821)  |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Reserved        |ActFlg |      Local CRLSP CR-LSP ID           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Ingress LSR Router ID                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Type
        A fourteen-bit field carrying the value of the  LSPID-TLV type
        which is 0x821.

   Length
        Specifies the length of the value field in bytes.

   ActFlg
        Action Indicator Flag: A 4-bit field that indicates explicitly
        the action that should be taken if the LSP already exists on
        the LSR receiving the message. A set of indicator code points
        is proposed as follows:

                0000: indicates initial LSP setup
                0001: indicates modify LSP
   Reserved
        Zero on transmission.  Ignored on receipt.

   Local CRLSP CR-LSP ID
        The Local LSP ID is an identifier of the CRLSP CR-LSP locally unique
        within the Ingress LSR originating the CRLDP. CR-LSP.

   Ingress LSR Router ID
        "An
        An LSR may use any of its own IPv4 addresses in this field" field.

4.6 Resource Class (Color) TLV

   The Resource Class as defined in [4] is used to specify which links
   are acceptable by this CRLSP. CR-LSP. This information allows for the
   network's topology to be pruned.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|      ResCls-TLV  (0x0822) |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             RsCls                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ResCls-TLV type
        which is 0x822.

   Length
        Specifies the length of the value field in bytes.

   RsCls
        The Resource Class bit mask indicating which of the 32
        _administrative groups_ or _colors_ of links the CRLSP CR-LSP can
        traverse.

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4.7 ER-Hop semantics

4.7.1. ER-Hop 1: The IPv4 prefix

   The abstract node represented by this ER-Hop is the set of nodes,
   which have an IP address, which lies within this prefix.  Note that
   a prefix length of 32 indicates a single IPv4 node.

   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|         0x801             |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|      Reserved                               |    PreLen     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    IPv4 Address (4 bytes)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        IPv4 Address 0x801

   Length
        Specifies the length of the value field in bytes.

   L Bit
        Set to indicate Loose hop.
        Cleared to indicate a strict hop.

   Reserved
        Zero on transmission.  Ignored on receipt.

   PreLen

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        Prefix Length 1-32

   IP Address
        A four-byte field indicating the IP Address.

4.7.2. ER-Hop 2: The IPv6 address

   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|          0x802            |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|             Reserved                        |    PreLen     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  IPV6 address                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  IPV6 address (continued)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  IPV6 address (continued)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   |                  IPV6 address (continued)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        0x802  IPv6 address

   Length
        Specifies the length of the value field in bytes.

   L Bit
        Set to indicate Loose hop.
        Cleared to indicate a strict hop.

   Reserved
        Zero on transmission.  Ignored on receipt.

   PreLen
        Prefix Length 1-128

   IPv6 address
        A 128-bit unicast host address.

4.7.3. ER-Hop 3:  The autonomous system number

   The abstract node represented by this ER-Hop is the set of nodes
   belonging to the autonomous system.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|          0x803            |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|          Reserved           |                AS Number      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        AS Number 0x803

   Length
        Specifies the length of the value field in bytes.

   L Bit
        Set to indicate Loose hop.
        Cleared to indicate a strict hop.

   Reserved
        Zero on transmission.  Ignored on receipt.

   AS Number
        Autonomous System number

4.7.4. ER-Hop 4: LSPID

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   The LSPID is used to identify the tunnel ingress point as the next
   hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
   already established CR-LSP. It also allows for splicing the CR-LSP
   being established with an existing CR-LSP.

   If an LSPID Hop is the last ER-Hop in an ER-TLV, than the LSR may
   splice the CR-LSP of the incoming Label Request to the CR-LSP that
   currently exists with this LSPID.  This is useful, for example, at
   the point at which a Label Request used for local repair arrives at
   the next ER-Hop after the loosely specified CR-LSP segment.  Use of
   the LSPID Hop in this scenario eliminates the need for ER-Hops to
   keep the entire remaining ER-TLV at each LSR that is at either
   (upstream or downstream) end of a loosely specified CR-LSP segment
   as part of its state information. This is due to the fact that the
   upstream LSR needs only to keep the next ER-Hop and the LSPID and
   the downstream LSR needs only to keep the LSPID in order for each
   end to be able to recognize that the same LSP is being identified.

   If the LSPID Hop is not the last hop in an ER-TLV, the LSR must
   forward the remaining ER-TLV in a Label Request message, using the
   CR-LSP specified by the LSPID, to the LSR that is the CR-LSP's
   egress. That LSR will continue processing of the CR-LSP Label
   Request Message.  The result is a tunneled, or stacked, CR-LSP.

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|          0x804            |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|          Reserved           |               Local LSPID     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Ingress LSR Router ID                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        LSPID 0x804

   Length
        Specifies the length of the value field in bytes.

   L Bit
        Set to indicate Loose hop.
        Cleared to indicate a strict hop.

   Reserved
        Zero on transmission.  Ignored on receipt.

   Local LSPID
        A 2 byte field indicating the LSPID which is unique with
        reference to its Ingress LSR.

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   Ingress LSR Router ID
        "An
        An LSR may use any of its own IPv4 addresses in this field" field.

4.8. Processing of the Explicit Route TLV

4.8.1. Selection of the next hop

   A Label Request Message containing a an explicit route TLV must
   determine the next hop for this path.  Selection of this next hop
   may involve a selection from a set of possible alternatives.  The
   mechanism for making a selection from this set is implementation
   dependent and is outside of the scope of this specification.
   Selection of particular paths is also outside of the scope of this
   specification, but it is assumed that each node will make a best
   effort attempt to determine a loop-free path.  Note that such best
   efforts may be overridden by local policy.

   To determine the next hop for the path, a node performs the
   following steps:

      1. The node receiving the Label Request Message must first
         evaluate the first ER-Hop. If the L bit is not set in the
         first ER-Hop and if the node is not part of the abstract node
         described by the first ER-Hop, it has received the message in
         error, and should return a _Bad initial ER-Hop_

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         error, and should return a _Bad Initial ER-Hop_ error. If the
         L bit is set and the local node is not part of the abstract
         node described by the first ER-Hop, the node selects a next
         hop that is along the path to the abstract node described by
         the first ER-Hop. If there is no first ER-Hop, the message is
         also in error and the system should return a _Bad Explicit
         Routing TLV_ error. error using a Notification Message sent upstream.

      2. If there is no second ER-Hop, this indicates the end of the
         explicit route. The explicit route TLV should be removed from
         the Label Request Message.  This node may or may not be the
         end of the LSP.  Processing continues with section 4.8.2,
         where a new explicit route TLV may be added to the Label
         Request Message.

      3. If the node is also a part of the abstract node described by
         the second ER-Hop, then the node deletes the first ER-Hop and
         continues processing with step 2, above.  Note that this makes
         the second ER-Hop into the first ER-Hop of the next iteration.

      4. The node determines if it is topologically adjacent to the
         abstract node described by the second ER-Hop.  If so, the node
         selects a particular next hop which is a member of the
         abstract node.  The node then deletes the first ER-Hop and
         continues processing with section 4.8.2.

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      5. Next, the node selects a next hop within the abstract node of
         the first ER-Hop that is along the path to the abstract node
         of the second ER-Hop.  If no such path exists then there are
         two cases:

           5.a If the second ER-Hop is a strict ER-Hop, then there is
           an error and the node should return a _Bad strict node_ Strict Node_
           error.

           5.b Otherwise, if the second ER-Hop is a loose ER-Hop, then
           the node selects any next hop that is along the path to the
           next abstract node.  If no path exists within the MPLS
           domain, then there is an error, and the node should return a
           _Bad loose node_ error.

      6. Finally, the node replaces the first ER-Hop with any ER-Hop
         that denotes an abstract node containing the next hop.  This
         is necessary so that when the explicit route is received by
         the next hop, it will be accepted.

      7. Progress the Label Request Message to the next hop.

4.8.2. Adding ER-Hops to the explicit route TLV

   After selecting a next hop, the node may alter the explicit route in
   the following ways.

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   If, as part of executing the algorithm in section 4.8.1, the
   explicit route TLV is removed, the node may add a new explicit route
   TLV.

   Otherwise, if the node is a member of the abstract node for the
   first ER-Hop, then a series of ER-Hops may be inserted before the
   first ER-Hop or may replace the first ER-Hop.  Each ER-Hop in this
   series must denote an abstract node that is a subset of the current
   abstract node.

   Alternately, if the first ER-Hop is a loose ER-Hop, an arbitrary
   series of ER-Hops may be inserted prior to the first ER-Hop.

4.9 Route Pinning TLV

   Section 2.4 describes the use of route pinning. The encoding of the
   Route Pinning TLV is as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|          0x823            |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |P|                        Reserved                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        Pinning-TLV type 0x823

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   Length
        Specifies the length of the value field in bytes.

   P Bit
        The P bit is set to 1 to indicate that route pinning is
        requested.
        The P bit is set to 0 to indicate that route pinning is not
        requested

   Reserved
        Zero on transmission.  Ignored on receipt.

4.10 CRLSP CR-LSP FEC Element

   A new FEC element is introduced in this specification to support CR-
   LSPs. This new FEC element does not preclude the use of other FECs
   elements (Type=0x01, 0x02, 0x03) defined in the LDP spec in CR-LDP
   messages. The CRLDP CR-LDP FEC Element is an opaque FEC to be used only in
   Messages of CR-LSPs.

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        FEC Element     Type    Value
        Type name

        CRLSP

        CR-LSP          0x04    No value; i.e., 0 value octets;

   The CR-LSP FEC TLV encoding is as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|          FEC(0x0100)      |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | CR-LSP (4)    |
   +-+-+-+-+-+-+-+-+

   Type
        FEC TLV type 0x0100

   Length
        Specifies the length of the value field in bytes.

   CR-LSP FEC Element Type
        0x04

4.11 Error subcodes

   In the processing described above, certain errors need to be
   reported as part of the Notification Message.  This section defines
   the status codes for the errors described in this specification.

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         Status Code                                       Type
         --------------------------------------         ----------
         Bad Explicit Routing TLV Error                 0x44000001
         Bad Strict Node Error                          0x44000002
         Bad Loose  Node Error                          0x44000003
         Bad Initial ER-Hop Error                       0x44000004
         Resource Unavailable                           0x44000005
         Traffic Parameters Unavailable                 0x44000006
         Setup abort Abort (Label Request Aborted in [1])     0x04000015
         Modify request not supported Request Not Supported                   0x44000008

5. Security

   Pre-emption has to be controlled by the MPLS domain.

   Resource reservation requires the LSRs to have an LSP admission
   control function.

   Traffic Engineered LSPs can bypass normal routing.

6. Acknowledgments

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   The messages used to signal the CRLSP CR-LSP setup are based on the work
   done by the [1] team.

   The Explicit Route object and procedures used
   in this specification are based on [8].

   The authors would also like to acknowledge the careful review and
   comments of Ken Hayward, Greg Wright, Geetha Brown, Brian Williams,
   Paul Beaubien, Matthew Yuen, Liam Casey, and Ankur Anand. Anand, Adrian Farrel.

7. Intellectual Property Consideration

   Nortel Networks may seek patent or other

   The IETF has been notified of intellectual property
   protection for rights claimed
   in regard to some or all of the technologies disclosed specification contained in this
   document. If any standards arising from this document are or become
   protected by one or  For more patents assigned to Nortel Networks, Nortel
   Networks is prepared to make a license available to any qualified
   applicant upon reasonable and non-discriminatory terms and
   conditions. Any such licenses will be subject to negotiations
   outside of information consult the IETF. online list of claimed
   rights.

8. References

   1  Andersson et al, "Label Distribution Protocol Specification"
      work in progress (draft-ietf-mpls-ldp-05), June 1999.

   2  Callon et al, "Framework for Multiprotocol Label Switching",
      work in progress (draft-ietf-mpls-framework-04), July (draft-ietf-mpls-framework-05), September 1999.

   3  Rosen et al, "Multiprotocol Label Switching Architecture",
      work in progress (draft-ietf-mpls-arch-04), April (draft-ietf-mpls-arch-06), September 1999.

Jamoussi, et. al.    draft-ietf-mpls-crldp-02.txt                   25 Internet Draft   Constraint-Based LSP Setup using LDP     August, 1999

   4  Awduche et al, "Requirements for Traffic Engineering Over
      MPLS", work in progress (draft-ietf-mpls-traffic-eng-01),
      June RFC 2702, September 1999.

   5  Heinanen et al, "MPLS Mappings of Generic VPN Mechanisms",
      work in progress (draft-heinanen-generic-vpn-mpls-00),
      August 1998.

   6  Jamieson et al, "MPLS VPN Architecture" work in progress
     (draft-jamieson-mpls-vpn-00), August 1998.

   7  T. Li, "CPE based VPNs using MPLS", work in progress (draft-
      li-mpls-vpn-00.txt), October 1998.

   8  Guerin et al, "Setting up Reservations on Explicit Paths using
      RSVP", work in progress (draft-guerin-expl-path-rsvp-01) November
      1997.

   9  L. Wu, et. al., "LDP State Machine" work in progress
      (draft-ietf-mpls-ldp-state-00), Feb 1999.

   10 J. Ash, et. al., _LSP Modification Using CR-LDP_ work in progress
      (draft-ash-crlsp-modify-00.txt), July 1999.

9. Author's Addresses

   Osama S. Aboul-Magd               Loa Andersson
   Nortel Networks                   Nortel Networks
   P O Box 3511 Station C            Kungsgatan 34, PO Box 1788            S:t Eriksgatan 115
   Ottawa, ON K1Y 4H7                111 97 Stockholm, Sweden                PO Box 6701
   Canada                            Phone: +46 8 441 78 34                            113 85 Stockholm
   Phone: +1 613 763-5827            Mobile            Tel: +46 70 522 78 34 8 508 835 00
   Osama@nortelnetworks.com          Loa_andersson@beynetworks.com          Fax: +46 8 508 835 01
                                  Loa_andersson@nortelnetworks.com

   Peter Ashwood-Smith               Ross Callon
   Nortel Networks                   IronBridge Networks
   P O Box 3511 Station C            55 Hayden Avenue,
   Ottawa, ON K1Y 4H7                Lexington, MA  02173
   Canada                            Phone: +1-781-402-8017
   Phone: +1 613 763-4534            Rcallon@ironbridgenetworks.com
   Petera@nortelnetworks.com

   Ram Dantu                         Paul Doolan
   Alcatel USA Inc.                  Ennovate Networks

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   IP Competence Center              330 Codman Hill Rd
   1201 E. Campbell Road.,446-315    Marlborough MA 01719
   Richadson, TX USA., 75081-2206    Phone: 978-263-2002
   Phone: 972 996 2938               Pdoolan@ennovatenetworks.com
   Fax:   972 996 5902
   Ram.dantu@aud.alcatel.com

Jamoussi, et. al.    draft-ietf-mpls-crldp-02.txt                   26 Internet Draft   Constraint-Based LSP Setup using LDP     August, 1999
   Ram.dantu@alcatel.com

   Nancy Feldman                     Andre Fredette
   IBM Corp.                         Nortel Networks
   17 Skyline Drive                  3 Federal Street                  600 Technology Park Drive
   Hawthorne NY 10532                Billerica, MA 01821
   Phone:  914-784-3254              978-288-8524
   Nkf@us.ibm.com                    Fredette@baynetworks.com                    Fredette@nortelnetworks.com

   Eric Gray                         Joel M. Halpern
   Lucent Technologies, Inc          Institutional Venture Partners
   1600 Osgood St.                   650-926-5633
   North Andover, MA  01847          joel@mcquillan.com          Joel@mcquillan.com
   Phone: 603-659-3386
   Ewgray@lucent.com

   Juha Heinanen                     Fiffi Hellstrand
   Telia Finland, Inc.               Ericsson Telecom AB
   Myyrmaentie 2                     S-126 25 STOCKHOLM
   01600 VANTAA                      Sweden
   Finland                           Tel: +46 8 719 4933
   Tel: +358 41 500 4808             etxfiff@etxb.ericsson.se             Etxfiff@etxb.ericsson.se
   Jh@telia.fi

   Bilel Jamoussi                    Timothy E. Kilty
   Nortel Networks Corp.             Northchurch Communications
   3 Federal Street
   600 Technology Park Drive         5 Corporate Drive,
   Billerica, MA 01821               Andover, MA 018110
   USA                               phone: 978 691-4656
   Phone: +1 978 288-4506            tkilty@northc.com            Tkilty@northc.com
   Jamoussi@nortelnetworks.com

   Andrew G. Malis                   Muckai K Girish
   Ascend Communications, Inc.       SBC Technology Resources,
   1 Robbins Road                    4698 Willow Road
   Westford, MA 01886                Pleasanton, CA 94588
   Phone: 978 952-7414               Phone: (925) 598-1263
   fax:   978 392-2074               Fax:   (925) 598-1321
   Malis@ascend.com                  mgirish@tri.sbc.com                  Mgirish@tri.sbc.com

   Kenneth Sundell                   Pasi Vaananen
   Nortel Networks                   Nokia Telecommunications
   Architecture Lab, EMEA
   S:t Eriksgatan 115                3 Burlington Woods Drive,
   Kungsgatan 34,
   PO Box 1788 6701                       Burlington, MA 01803
   111 97 Stockholm, Sweden
   113 85 Stockholm                  Phone: +1-781-238-4981
   phone:
   Tel: +46 8 441-7838,            Pasi.vaananen@ntc.nokia.com
   mobile 508 835 00             Pasi.vaanenen@ntc.nokia.com
   Fax: +46 70 665-7838
   ksundell@nortelnetworks.com 8 508 835 01

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   Ksundell@nortelnetworks.com

   Tom worster Worster                       Liwen Wu
   Nokia                             Alcatel U.S.A
   3 Burlington Woods Dr.            44983 Knoll Square
   Suite 250                         Ashburn, Va. 20147
   Burlington MA 01803 USA           Phone: (703) 724-2619
   +1 617 247 2624                   FAX:   (703) 724-2005
   tom.worster@nokia.com
   Tom.worster@nokia.com             Liwen.wu@and.alcatel.com

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Appendix A: CRLSP CR-LSP Establishment Examples

A.1 Strict Explicit Route Example

   This appendix provides an example for the setup of a strictly routed
   CRLSP.
   CR-LSP.  In this example, a specific node represents each abstract
   node.

   The sample network used here is a four node network with two  edge
   LSRs and two core LSRs as follows:

   abc
   LSR1------LSR2------LSR3------LSR4

   LSR1 generates a Label Request Message as described in Section 3.1
   of this draft and sends it to LSR2. This message includes the CR-
   TLV.

   A vector of three ER-Hop TLVs <a, b, c> composes the ER-TLV.
   The ER-Hop TLVs used in this example are of type 0x0801 (IPv4
   prefix) with a prefix length of 32. Hence, each ER-Hop TLV
   identifies a specific node as opposed to a group of nodes.
   At LSR2, the following processing of the ER-TLV per Section 4.8.1 of
   this draft takes place:

        1) The first hop <a> node LSR2 is part of the abstract node LSR2. described by the
           first hop <a>.  Therefore, the first step passes the test.
           Go to step 2.

        2) There is a second ER-Hop, <b>. Go to step 3.

        3) LSR2 is not part of the abstract node described by the
           second ER-Hop <b>. Go to Step 4.

        4) LSR2 determines that it is topologically adjacent to the
           abstract node described by the second ER-Hop <b>. LSR2
           selects a next hop (LSR3) which is the abstract node. LSR2
           deletes the first ER-Hop <a> from the ER-TLV ER-TLV, which now
           becomes <b , <b, c>. Go
        to Processing continues with Section 4.8.2.

   At LSR2, the following processing of Section 4.8.2 takes place:
   Executing algorithm 4.8.1 did not result in the removal of the ER-
   TLV.

   Also, LSR2 is not a member of the abstract node described by the
   first ER-Hop <b>.

   Finally, the first ER-Hop <b> is a strict hop.

   Therefore, processing section 4.8.2 does not result in the insertion
   of new ER-Hops. The selection of the next hop has been already done
   is step 4 of Section 4.8.1 and the processing of the ER-TLV is

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   completed at LSR2. In this case, the Label Request Message including
   the ER-TLV <b, c> is progressed by LSR2 to LSR3.

   At LSR3, a similar processing to the ER-TLV takes place except that
   the incoming ER-TLV = <b, c> and the outgoing ER-TLV is <c>.

   At LSR4, the following processing of section 4.8.1 takes place:

        1) The first hop <c> node LSR4 is part of the abstract node LSR4. described by the
           first hop <c>. Therefore, the first step passes the test. Go
           to step 2.
        2) There is no second ER-Hop, this indicates the end of the
        CRLSP. CR-
           LSP. The ER-TLV is removed from the Label Request Message.
           Processing continues with Section 4.8.2.

   At LSR4, the following processing of Section 4.8.2 takes place:
   Executing algorithm 4.8.1 resulted in the removal of the ER-TLV.
   LSR4 does not add a new ER-TLV.

   Therefore, processing section 4.8.2 does not result in the insertion
   of new ER-Hops. This indicates the end of the CRLSP CR-LSP and the
   processing of the ER-TLV is completed at LSR4.

   At LSR4, processing of Section 3.2 is invoked. The first condition
   is satisfied (LSR4 is the egress end of the CRLSP CR-LSP and upstream
   mapping has been requested). Therefore, a Label Mapping Message is
   generated by LSR4 and sent to LSR3.

   At LSR3, the processing of Section 3.2 is invoked. The second
   condition is satisfied (LSR3 received a mapping from its downstream
   next hop LSR4 for a CRLSP CR-LSP for which an upstream request is still
   pending). Therefore, a Label Mapping Message is generated by LSR3
   and sent to LSR2.

   At LSR2, a similar processing to LSR 3 takes place and a Label
   Mapping Message is sent back to LSR1 LSR1, which completes the end-to-end
   CRLSP
   CR-LSP setup.

A.2.

A.2 Node Groups and Specific Nodes Example

   A request at ingress LSR to setup a CRLSP CR-LSP might originate from a
   management system or an application, the details are implementation
   specific.

   The ingress LSR uses information provided by the management system
   or the application and possibly also information from the routing
   database to calculate the explicit route and to create the Label
   Request Message.

   The Label request message carries together with other necessary
   information a an ER-TLV defining the explicitly routed path. In our
   example the list of hops in the ER-Hop TLV is supposed to contain an

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   abstract node representing a group of nodes, an abstract node
   representing a specific node, another abstract node representing a
   group of nodes, and an abstract node representing a specific egress
   point.

   In--{Group 1}--{Specific A}--{Group 2}--{Specific Out: B}
   The ER-TLV contains four ER-Hop TLVs:

        1. An ER-Hop TLV that specifies a group of LSR valid for the
           first abstract node representing a group of nodes (Group 1).

        2. An ER-Hop TLV that indicates the specific node (Node A).

        3. An ER-Hop TLV that specifies a group of LSRs valid for the
           second abstract node representing a group of nodes (Group
           2).

        4. An ER-Hop TLV that indicates the specific egress point for
           the CRLSP CR-LSP (Node B).

   All the ER-Hop TLVs are strictly routed nodes.
   The setup procedure for this CRLSP CR-LSP works as follows:

        1. The ingress node sends the Label Request Message to a node
           that is a member the group of nodes indicated in the first
           ER-Hop TLV, following normal routing for the specific node
           (A).

        2. The node that receives the message identifies itself as part
           of the group indicated in the first ER-Hop TLV, and that it
           is not the specific node (A) in the second. Further it
           realizes that the specific node (A) is not one of its next
           hops.

        3. It keeps the ER-Hop TLVs intact and sends a Label Request
           Message to a another node that is part of the group indicated
           in the first ER-Hop TLV (Group 1), following normal routing
           for the specific node (A).

        4. The node that receives the message identifies itself as part
           of the group indicated in the first ER-Hop TLV, and that it
           is not the specific node (A) in the second ER-Hop TLV.
           Further it realizes that the specific node (A) is one of its
           next hops.

        5. It removes the first ER-Hop TLVs and sends a Label Request
           Message to the specific node (A).

        6. The specific node (A) recognizes itself in the first ER-Hop
           TLV. Removes the specific ER-Hop TLV.

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        7. It sends a Label Request Message to a node that is a member
           of the group (Group 2) indicated in the ER-Hop TLV.

        8. The node that receives the message identifies itself as part
           of the group indicated in the first ER-Hop TLV, further it
           realizes that the specific egress node (B) is one of its
           next hops.

        9. It sends a Label Request Message to the specific egress node
           (B).

        10.The specific egress node (B) recognizes itself as the egress

           for the CRLSP, CR-LSP, it returns a Label Mapping Message, that
           will traverse the same path as the Label Request Message in
           the opposite direction.

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                    Appendix B. QoS Service Examples

B.1 Service Examples

   Construction of an end-to-end service is the result of the rules
   enforced at the edge and the treatment that packets receive at the
   network nodes. The rules define the traffic conditioning actions
   that are implemented at the edge and they include policing with
   pass, mark, and drop capabilities. The edge rules are expected to
   be tobe
   defined by the mutual agreements between the service providers and
   their customers and they will constitute an essential part of the
   SLA. Therefore edge rules are not included in the signaling
   protocol.

   Packet treatment at a network node is usually referred to as the
   local behavior.  Local behavior could be specified in many ways. One
   example for local behavior specification is the service frequency
   introduced in section 4.3.2.1, together with the resource
   reservation rules implemented at the nodes.

   Edge rules and local behaviors can be viewed as the main building
   blocks for the end-to-end service construction. The following table
   illustrates the applicability of the building block approach for
   constructing different services including those defined for ATM.

   Service        PDR  PBS  CDR     CBS   EBS  Service    Conditioning
   Examples                                    Frequency  Action

   DS             S    S    =PDR    =PBS  0    Frequent   drop>PDR

   TS             S    S    S       S     0    Unspecified drop>PDR,PBS
                                                           mark>CDR,CBS

   BE             inf  inf  inf     inf   0    Unspecified      -

   FRS            S    S    CIR     ~B_C  ~B_E Unspecified drop>PDR,PBS
                                                       mark>CDR,CBS,EBS

   ATM-CBR        PCR  CDVT =PCR    =CDVT 0    VeryFrequent    drop>PCR

   ATM-VBR.3(rt)  PCR  CDVT SCR     MBS   0    Frequent        drop>PCR
                                                           mark>SCR,MBS

   ATM-VBR.3(nrt) PCR  CDVT SCR     MBS   0    Unspecified     drop>PCR
                                                           mark>SCR,MBS

   ATM-UBR        PCR  CDVT -       -     0    Unspecified     drop>PCR

   ATM-GFR.1      PCR  CDVT MCR     MBS   0    Unspecified     drop>PCR

   ATM-GFR.2      PCR  CDVT MCR     MBS   0    Unspecified     drop>PCR
                                                           mark>MCR,MFS

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   int-serv-CL    p    m    r       b     0    Frequent        drop>p
                                                               drop>r,b

   S= User specified

   In the above table, the DS refers to a delay sensitive service where
   the network commits to deliver with high probability user datagrams
   at a rate of PDR with minimum delay and delay requirements.
   Datagrams in excess of PDR will be discarded.

   The TS refers to a generic throughput sensitive service where the
   network commits to deliver with high probability user datagrams at a
   rate of at least CDR. The user may transmit at a rate higher than
   CDR but datagrams in excess of CDR would have a lower probability of
   being delivered.

   The BE is the best effort service and it implies that there are no
   expected service guarantees from the network.

B.2.

B.2 Establishing CR-LSP Supporting Real-Time Applications

   In this scenario the customer needs to establish an LSP for
   supporting real-time applications such as voice and video. The Delay-
   sensitive
   Delay-sensitive (DS) service is requested in this case.

   The first step is the specification of the traffic parameters in the
   signaling message. The two parameters of interest to the DS service
   are the PDR and the PBS and the user based on his requirements
   specifies their values. Since all the traffic parameters are
   included in the signaling message, appropriate values must be
   assigned to all of them. For DS service, the CDR and the CBS values
   are set equal to the PDR and the PBS respectively. An indication of
   whether the parameter values are subject to negotiation is flagged.

   The transport characteristics of the DS service require that Frequent
   frequency to be requested to reflect the real-time delay
   requirements of the service.

   In addition to the transport characteristics, both the network
   provider and the customer need to agree on the actions enforced at
   the edge. The specification of those actions is expected to be a
   part of the service level agreement (SLA) negotiation and is not
   included in the signaling protocol. For DS service, the edge action
   is to drop packets that exceed the PDR and the PBS specifications.
   The signaling message will be sent in the direction of the ER path
   and the LSP is established following the normal LDP procedures. Each
   LSR applies its admission control rules. If sufficient resources are
   not available and the parameter values are subject to negotiation,
   then the LSR could negotiate down the PDR, the PBS, or both.

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   The new parameter values are echoed back in the Label Mapping
   Message. LSRs might need to re-adjust their resource reservations
   based on the new traffic parameter values.

B.3.

B.3 Establishing CR-LSP Supporting Delay Insensitive Applications

   In this example we assume that a throughput sensitive (TS) service
   is requested. For resource allocation the user assigns values for
   PDR, PBS, CDR, and CBS. The negotiation flag is set if the traffic
   parameters are subject to negotiation.
   Since the service is delay insensitive by definition, the
   Unspecified frequency is signaled to indicate that the service
   frequency is not an issue.

   Similar to the previous example, the edge actions are not subject
   for signaling and are specified in the service level agreement
   between the user and the network provider.

   For TS service, the edge rules might include marking to indicate
   high discard precedence values for all packets that exceed CDR and
   the CBS. The edge rules will also include dropping of packets that
   are do not
   conform to neither PDR nor PBS.

   Each LSR of the LSP is expected to run its admission control rules
   and negotiate traffic parameters down if sufficient resources do not
   exist. The new parameter values are echoed back in the Label Mapping
   Message. LSRs might need to re-adjust their resources based on the
   new traffic parameter values.

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Full Copyright Statement
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   others, and derivative works that comment on or otherwise explain it
   or assist in

               Appendix C. LSP Modification Using CR-LDP

   After a CR-LSP is set up, its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works. However, this
   document itself bandwidth reservation may not need to be modified in any way, such as
   changed by removing the copyright notice or references network operator, due to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures new requirements for
   copyrights defined in the Internet Standards process must be
   followed, or as required
   traffic carried on that CR-LSP. This contribution presents an
   approach to translate modify the bandwidth and possibly other parameters of an
   established CR-LSP using CR-LDP without service interruption. The
   LSP modification feature can be supported by CR-LDP with a minor
   extension of an _action indicator flag_. This feature has
   application in dynamic network resources management where traffic of
   different priorities and service classes is involved.

   Conventions used in this Appendix:

        L:              LSP (Label Switched Path)
        Lid:            LSPID (LSP Identifier)
        T:              Traffic Parameters
        R:              LSR (Label Switching Router)
        FTN:            FEC To NHLFE
        FEC:            Forwarding Equivalence Class
        NHLFE:          Next Hop Label Forwarding Entity
        TLV:            Type Length Value

C.1 Introduction

   Consider an LSP L1 that has been established with its set of traffic
   parameters T0. A certain amount of bandwidth is reserved along the
   path of L1.  Consider then that some changes are required on L1. For
   example, the bandwidth of L1 needs to be increased to accommodate
   the increased traffic on L1. Or the SLA associated with L1 needs to
   be modified because a different service class is desired. The
   network operator, in these cases, would like to modify the
   characteristics of L1, for example, to change its traffic parameter
   set from T0 to T1, without releasing the LSP L1 to interrupt the
   service. In some other cases, network operators may want to reroute
   a CR-LSP to a different path for either improved performance or
   better network resource utilization. In all these cases, LSP
   modification is required. In section C.2 below, a method to modify
   an active LSP using CR-LDP is presented. The concept of LSPID in CR-
   LDP is used to achieve the LSP modification, without releasing the
   LSP and interrupting the service and, without double booking the
   bandwidth. Only a minimum extension on CR-LDP, an action indication
   flag of _modify_ is needed in order to explicitly specify the
   behavior, and allow the existing LSPID to support other networking
   capabilities in the future. Section 4.5 specifies the action
   indication flag of _modify_ for CR-LDP. An example is described to
   demonstrate an application of the presented method in dynamically
   managing network bandwidth requirements without interrupting
   service.

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C.2 Basic Procedure

   LSP modification can only be allowed when the LSP is already set up
   and active. That is, modification is not defined nor allowed during
   the LSP establishment or label release/withdraw phases. Only
   modification requested by the ingress LSR of the LSP is considered
   in this draft for CR-LSP. Ingress LSR cannot modify an LSP before a
   previous modification procedure is completed.

   Assume that CR-LSP L1 is set up with LSPID L-id1, which is unique in
   the MPLS network. The ingress LSR R1 of L1 has in its FTN (FEC To
   NHLFE) table FEC1 -> Label A mapping where A is the outgoing label
   for LSP L1. To modify the characteristics of L1, R1 sends a Label
   Request Message. In the messages, the TLVs will have the new
   requested values, and the LSPID TLV is included which indicates the
   value of L-id1. The Traffic Parameters TLV, the ER-TLV, the Resource
   Class (color) TLV and the Preemption TLV can have values different
   from those in the original Label Request Message, which  has been
   used to set up L1 earlier. Thus, L1 can be changed in its bandwidth
   request (traffic parameter TLV), its traffic service class (traffic
   parameter TLV), the route it traverses (ER TLV) and its setup and
   holding (Preemption TLV) priorities. The ingress LSR R1 now still
   has the entry in FTN as FEC1 -> Label A. R1 is waiting to establish
   another entry for FEC1.

   When an LSR Ri along the path of L1 receives the Label Request
   message, its behavior is the same as that of receiving any Label
   request message. The only extension is that Ri examines the LSPID
   carried in the Label Request Message, L-id1 and identifies if it
   already has L-id1. If Ri does not have L-id1, Ri behaves the same as
   receiving a new Label Request message. If Ri already has L-id1, Ri
   takes the newly received Traffic Parameter TLV and computes the new
   bandwidth required and derives the new service class. Compared with
   the already reserved bandwidth for L-id1, Ri now reserves only the
   difference of the bandwidth requirements. This prevents Ri from
   doing bandwidth double booking. If a new service class is requested,
   Ri also prepares to receive the traffic on L1 in, perhaps a
   different type of queue, just the same as handling it for a Label
   Request Message. Ri assigns a new label for the Label Request
   Message.

   When the Label Mapping message is received, two sets of labels exist
   for the same LSPID. Then the ingress LSR R1 will have two outgoing
   labels, A and B, associated with the same FEC, where B is the new
   outgoing label received for LSP L1. The ingress LSR R1 can now
   activate the new entry in FTN, FEC1 - > Label B. This means that R1
   swaps traffic on L1 to the new label _B_ (_new_ path) for L1. The
   packets can now be sent with the new label B, with the new set of
   traffic parameters if any, on a new path, that is, if a new path is
   requested in the Label Request Message for the modification. All the
   other LSRs along the path will start to receive the incoming packets
   with the new label. For the incoming new label, the LSR has already

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   established its mapping to the new outgoing label. Thus, the packets
   will be sent out with the new outgoing label. The LSRs do not have
   to  implement new procedures to track the new and old
   characteristics of the LSP.

   The ingress LSR R1 then starts to release the original label A for
   LSP L1. The Label Release Message is sent by R1 towards the down
   stream LSRs. The Release message carries the LSPID of L-id1 and the
   Label TLV to indicate which label is to be released. The Release
   Message is propagated to the egress LSR to release the original
   labels previously used for L1. Upon receiving the Label Release
   Message, LSR R1 examines the LSPID, L-id1 and finds out that the L-
   id1 has still another set of label (incoming/outgoing) under it.
   Thus, the old label is released without releasing the resource in
   use. That is, if the bandwidth has been decreased for L1, the delta
   bandwidth is released. Otherwise, no bandwidth is released. This
   modification procedure can not only be applied to modify the traffic
   parameters and/or service class of an active LSP, but also to
   reroute an existing LSP, and/or change its setup/holding priority if
   desired. After the release procedure, the modification of the LSP is
   completed.

   The method described above follows the normal behavior of Label
   Request / Mapping / Notification / Release /Withdraw procedure of a
   CR-LDP operated LSR with a specific action taken on LSPID. If Label
   Withdraw Message is used to withdraw a label associated with an
   LSPID, the Label TLV should be included to specify which label to
   withdraw. Since the LSPID can also be used for other feature
   support, an action indication flag of _modify_ assigned to the LSPID
   would explicitly explain the action/semantics that should be
   associated with the messaging procedure. The details of this flag
   are addressed in Section 4.5.

C.3 Priority Handling

   When sending a Label Request Message for an active LSP L1 to request
   changes, the setup priority used in the label Request Message can be
   different from the one used in the previous Label Request Message,
   effectively indicating the priority of this _modification_ request.
   Network operators can use this feature to decide what priority is to
   be assigned to a modification request, based on their
   policies/algorithms and other traffic situations in the network. For
   example, the priority for modification can be determined by the
   priority of the customer/LSP. If a customer has exceeded the
   reserved bandwidth of its VPN LSP tunnel by too much, the
   modification request's priority may be given higher.
   The Label Request message for the modification of an active LSP can
   also be sent with a holding priority different from its previous
   one. This effectively changes the holding priority of the LSP. Upon
   receiving a Label Request Message that requests a new holding
   priority, the LSR assigns the new holding priority to the bandwidth.
   That is, the new holding priority is assigned to both the existing

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   incoming / outgoing labels and the new labels to be established for
   the LSPID in question. In this way self-bumping is prevented.

C.4 Modification Failure Case Handling

   A modification attempt may fail due to insufficient resource or
   other situations. A Notification message is sent back to the ingress
   LSR R1 to indicate the failure of Label Request Message that
   intended to modify the LSP. Retry may be attempted if desired by the
   network operator.

   If the LSP on the original path failed when a modification attempt
   is in progress, the attempt should be aborted by using the Label
   Abort Request message as specified in LDP draft.

Full Copyright Statement
   _Copyright c The Internet Society (date). All Rights Reserved. This
   document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

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