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Versions: (draft-jamoussi-mpls-cr-ldp) 00 01 02 03 04 05 RFC 3212

MPLS Working Group                             Bilel Jamoussi, Editor
Internet Draft                                        Nortel Networks
Expiration Date: August 1999

                                                        February 1999

                  Constraint-Based LSP Setup using LDP

                     draft-ietf-mpls-cr-ldp-01.txt

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

   Label Distribution Protocol (LDP) is defined in [LDP] 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
   others. Constraint-based routing (CR) is a mechanism used to meet
   Traffic Engineering requirements that have been proposed by [FRAME],
   [ARCH] and [TER]. These requirements may be met by extending LDP for
   support of constraint-based routed label switched paths (CRLSPs).



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   Other uses exist for CRLSPs as well ([VPN1], [VPN2] and [VPN3]).

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

Table of Contents

   1.         Introduction .........................................   3
   2.         Constraint-based Routing Overview ....................   3
   2.1        Strict and Loose Explicit Routes .....................   4
   2.2        Traffic Characteristics ..............................   4
   2.3        Pre-emption ..........................................   5
   2.4        Route Pinning ........................................   5
   2.5        Resource Class .......................................   5
   3.         Solution Overview ....................................   5
   3.1        Required Messages and TLVs ...........................   7
   3.2        Label Request Message ................................   7
   3.3        Label Mapping Message ................................   8
   3.4        Notification Message .................................   9
   3.5        Release & Withdraw Messages ..........................   9
   4.         Protocol Specification  ..............................   9
   4.1        Explicit Route TLV (ER-TLV)  .........................  10
   4.2        Explicit Route Hop TLV  ..............................  10
   4.3        Traffic Parameters TLV  ..............................  12
   4.3.1      Semantics  ...........................................  13
   4.3.1.1    Frequency  ...........................................  13
   4.3.1.2    Peak Rate  ...........................................  14
   4.3.1.3    Committed 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 .....................  15
   4.3.1.7    Weight ......................... .....................  16
   4.3.2      Procedures ...........................................  16
   4.3.2.1    Label Request Message ................................  16
   4.3.2.2    Label Mapping Message ................................  16
   4.3.2.3    Notification Message .................................  17
   4.4        Preemption TLV .......................................  18
   4.5        LSPID TLV  ...........................................  18
   4.6        Resource Class TLV  ..................................  19
   4.7        ER-Hop Semantics .....................................  19
   4.7.1      ER-Hop 1 TLV IPv4 Prefix .............................  20
   4.7.2      ER-Hop 2 TLV IPv6 Prefix .............................  20
   4.7.3      ER-Hop 3 TLV AS Number ...............................  21
   4.7.4      ER-Hop 4 TLV LSPID ...................................  21
   4.8        Processing of the ER-TLV .............................  22
   4.8.1      Selection of the next hop ............................  22
   4.8.2      Adding the Label Request Message to the next hop .....  24
   4.9        Route Pinning TLV  ...................................  24
   4.10       CR-LSP FEC Element ...................................  24
   4.11       Error Subcodes  ......................................  25

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   5.         Security Considerations ..............................  26
   6.         Acknowledgement ......................................  26
   7.         References ...........................................  26
   8.         Author Information ...................................  28

   Appendix A CRLSP Establishment Examples .........................  30
   A.1        Strict Explicit Route Example ........................  30
   A.2        Node Groups and Specific Nodes Example ...............  31

   Appendix B QoS Service Examples .................................  34
   B.1        Service Examples .....................................  34
   B.2        Establishing CR-LSP Supporting Real-Time Applications.  35
   B.3        Establishing CR-LSP Delay Insensitive Applications ...  36

1. Introduction

   The need for constraint-based routing (CR) in MPLS has been explored
   elsewhere [ARCH], [FRAME], and [TER].  Explicit routing is a subset
   of the more general constraint-based routing function. At the MPLS WG
   meeting held during the Washington IETF there was consensus that LDP
   should support explicit routing of LSPs with provision for indication
   of associated (forwarding) priority.  In the Chicago meeting, 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.
   This specification proposes an end-to-end setup mechanism of a
   constraint-based routed LSP (CRLSP) 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 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 [TER]. 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

   Like any other LSP an CRLSP 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,
   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 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, 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.

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

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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
   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 and the holdingPriority attributes
   of the existing CRLSP are used to specify priorities. Signaling a
   higher holding priority expresses 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 should not be higher (numerically less)
   than its holdingPriority since it might bump an LSP and be bumped by
   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
   may be setup using route pinning if it is undesirable to change the
   path used by an LSP because a better next hop becomes available at
   some LSR along the loosely routed portion of the LSP.

2.5 Resource Class

   Network resources may be classified in various ways by the network
   operator. These classes are also known as "colors" or "administrative
   groups". When an CR-LSP is being established, it's necessary to
   indicate which resource classes the CR-LSP can draw from.

3. Solution Overview

   CRLSP over LDP Specification is designed with the following goals:

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

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

      3. Keep the solution simple.

   In this document, support for unidirectional point-to-point CRLSPs 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 [LDP]:

      - Basic and/or Extended Discovery Mechanisms.

      - Use the Label Request Message defined in [LDP] in downstream on
      demand label advertisement mode with ordered control.

      - Use the Label Mapping Message defined in [LDP] in downstream on
      demand mode with ordered control.

      - Use the Notification Message defined in [LDP].

      - Use the Withdraw and Release Messages defined in [LDP].

      - Use the Loop Detection (in the case of loosely routed segments
      of a CRLSP) mechanisms defined in [LDP].

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

      - The Label Request Message used to setup a CRLSP 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. Note that this is also true
      for the loosely routed parts of a CRLSP.

      - New status codes are defined to handle error notification for
      failure of established paths specified in the CR-TLV.


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

3.1 Required Messages and TLVs

   Any Messages, TLVs, and procedures not defined explicitly in this
   document are defined in the [LDP] Specification. The state
   transitions which relate to CR-LDP messages can be found in [LDP-
   STATE].

   The following subsections are meant as a cross reference to the [LDP]
   document and indication of additional functionality beyond what's
   defined in [LDP] where necessary.

3.2 Label Request Message

   The Label Request Message is as defined in 3.5.8 of [LDP] 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 Return Message ID TLV is MANDATORY.

      - 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:



















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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |U|   Label Request (0x0401)   |      Message Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Message ID                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     FEC TLV                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Return 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

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

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

      - The Label Mapping Message MUST include Label Request Message ID
      TLV.

      - The Label Mapping Message MUST include LSPID TLV.

      - 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 and an upstream mapping
      has been requested.

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

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

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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |U|   Label Mapping (0x0400)   |      Message Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Message ID                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     FEC TLV                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Label TLV                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              Label Request Message ID TLV  (mandatory)        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     LSPID TLV            (CR-LDP, mandatory)  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Traffic  TLV         (CR-LDP, optional)   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.4 Notification Message

   The Notification Message is as defined in Section 3.5.1 of [LDP] and
   the Status TLV encoding is as defined in Section 3.4.7 of [LDP].

   Establishment of an Explicitly Routed LSP may fail for a variety of
   reasons.  All such failures are considered advisory conditions and
   they are signaled by the Notification Message.

   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 and
   the processing of the CR-TLV.

   The Notification Message must carry the LSPID TLV of the
   corresponding CRLSP.

3.5 Release and Withdraw Messages

   The Label Release and Label Withdraw Messages are used as specified
   in [LDP] to clear CR-LSPs. These message may also carry the LSPID
   TLV.

4. Protocol Specification

   The Label Request Messages defined in [LDP] 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

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

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.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F|         ER-TLV  (0x0800)  |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          ER-Hop TLV 1                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          ER-Hop TLV 2                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                          ............                         ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          ER-Hop TLV n                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   Type
      A two byte field carrying the value of the ER-TLV type which
      is 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. Each ER-Hop TLV has the form:




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

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   ER-Hop Type
      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
             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 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.


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

4.3  Traffic Parameters TLV

   The following sections describe the CRLSP Traffic Parameters.  The
   required characteristics of a CRLSP 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:

      0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F| 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)                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   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:

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                         +--+--+--+--+--+--+--+--+
                         | 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.

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

                               0      - Unspecified
                               1      - Frequent
                               2      - VeryFrequest
                               3-255  - Reserved


   Reserved
      Zero on transmission.  Ignored on receipt.

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

   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

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CR-LDP Specification             - 14 -                 Exp. August 1999


   The Frequency specifies at what granularity the CDR allocated to the
   CRLSP is made available.  The value VeryFrequently 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 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. 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.

   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.

   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 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 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:

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CR-LDP Specification             - 15 -                 Exp. August 1999


        o 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

        o 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 never in
   excess of the peak rate.

   The actual implementation of a 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 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 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:

        o If Tc is less than CBS, Tc is incremented by one, else

        o if Te is less then EBS, Te is incremented by one, else

        o neither Tc nor Te is incremented.

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

        o 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

        o 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

        o the packet is in excess of both the Committed Rate and the EBS
          and neither Tc nor Tc 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

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CR-LDP Specification             - 16 -                 Exp. August 1999


   exceeded.

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

4.3.1.7 Weight

   The weight determines the CRLSP'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
   Parameters Unavailable to the upstream LSR from which it received the
   erroneous message.

   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 1).

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

   If, after possible Traffic Parameter negotiation, an LSR cannot
   support the CRLSP Traffic Parameters then the LSR MUST send a
   notification message that contains the 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
   Parameters Unavailable to the LSR from which it received the
   erroneous 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.

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CR-LDP Specification             - 17 -                 Exp. August 1999


   An LSR SHOULD adjust the resources that it reserved for a CRLSP 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, it SHOULD
   release any resources that it possibly had reserved for the CRLSP.

   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 [LDP].

4.4 Preemption TLV

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F| Preemption-TLV  (0x0820)  |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  SetPrio      | HoldPrio      |      Reserved                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

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

   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.

   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.

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CR-LDP Specification             - 18 -                 Exp. August 1999


      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 within an MPLS network.

   The LSPID is composed of the ingress LSR Router ID and a Locally
   unique CRLSP 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.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F|      LSPID-TLV  (0x0821)  |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Reserved                |      Local CRLSP ID           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Ingress LSR Router ID                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   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.

   Reserved
      Zero on transmission.  Ignored on receipt.

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

   Ingress LSR Router ID
      A 4 byte field indicating the Ingress LSR ID.

4.6 Resource Class (Color) TLV

   The Resource Class as defined in [TER] is used to specify which links
   are acceptable by this CRLSP. This information allows for the

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CR-LDP Specification             - 19 -                 Exp. August 1999


   networks topology to be pruned.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F|      ResCls-TLV  (0x0822) |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                             RsCls                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   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 can traverse.

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

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

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CR-LDP Specification             - 20 -                 Exp. August 1999


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

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   Type
      0x802  IPv6 address

   Length
      Specifies the length of the value field in bytes.

   L Bit
      Set to indicate Loose hop.

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CR-LDP Specification             - 21 -                 Exp. August 1999


      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 32:  The autonomous system number

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

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F|          0x803            |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|          Reserved           |                AS Number      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   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

   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

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CR-LDP Specification             - 22 -                 Exp. August 1999


   being established with an existing CR-LSP.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F|          0x804            |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |L|          Reserved           |               Local LSPID     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       Ingress LSR Router ID                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   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 the its Ingress LSR.

   Ingress LSR Router ID
      A 4 byte field indicating the Ingress LSR ID.

4.8. Processing of the Explicit Route TLV

4.8.1. Selection of the next hop

   A Label Request Message containing a 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

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CR-LDP Specification             - 23 -                 Exp. August 1999


   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" 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.

      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.

      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:

      5a) If the second ER-Hop is a strict ER-Hop, then there is an
      error and the node should return a "Bad strict node" error.

      5b) 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.

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CR-LDP Specification             - 24 -                 Exp. August 1999


      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.

   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

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

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   Type
      Pinning-TLV type 0x823

   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 FEC Element


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CR-LDP Specification             - 25 -                 Exp. August 1999


   A new FEC element is introduced in this specification to support CR-
   LSPs. The CRLDP FEC Element is an opaque FEC.

      FEC Element     Type      Value
      type name

      CRLSP           0x04      No value; i.e., 0 value octets;
                                            see below.

      CRLSP FEC Element
          To be used only in Messages of CR-LSPs.

   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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |U|F|          FEC(0x0100)      |      Length                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | CR-LSP (4)    |          Reserved                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   U bit
      Unknown TLV bit. As defined in [LDP].

   F bit
      Forward unknown TLV bit.  As defined in [LDP].

   Type
      FEC TLV type 0x0100

   Length
      Specifies the length of the value field in bytes.

   CR-LSP FEC Element Type
      0x04

   Reserved
      Zero on transmission.  Ignored on receipt.

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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CR-LDP Specification             - 26 -                 Exp. August 1999



      Status Code                                       Type
      --------------------------------------         ----------
      Bad Explicit Routing TLV Error                 0x04000001
      Bad Strict Node Error                          0x04000002
      Bad Loose  Node Error                          0x04000003
      Bad Initial ER-Hop Error                       0x04000004
      Resource Unavailable                           0x04000005
      Traffic Parameters Unavailable                 0x04000006
      Setup abort                                    0x04000007

5. Security

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

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

   Normal routing can be bypassed by Traffic Engineered LSPs.

6. Acknowledgments

   The messages used to signal the CRLSP setup are based on the work
   done by the [LDP] team. The Explicit Route object and procedures used
   in this specification are based on [ER].

   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.

7. References

   [LDP]   Andersson et al, "Label Distribution Protocol Specification"
           work in progress (draft-ietf-mpls-ldp-03), Feb. 1999.

   [ARCH]  Rosen et al, "Multiprotocol Label Switching Architecture",
           work in progress (draft-ietf-mpls-arch-04), Feb. 1999.

   [FRAME] Callon et al, "Framework for Multiprotocol Label Switching",
           work in progress (draft-ietf-mpls-framework-02), November
           1997.

   [TER]   Awduche et al, "Requirements for Traffic Engineering Over
           MPLS", work in progress (draft-ietf-mpls-traffic-eng-00),
           August 1998.

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


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CR-LDP Specification             - 27 -                 Exp. August 1999


   [VPN1]  Heinanen et al, "MPLS Mappings of Generic VPN Mechanisms",
           work in progress (draft-heinanen-generic-vpn-mpls-00),
           August 1998.

   [VPN2]  Jamieson et al, "MPLS VPN Architecture" work in progress
           (draft-jamieson-mpls-vpn-00), August 1998.

   [VPN3]  T. Li, "CPE based VPNs using MPLS", work in progress (draft-
           li-mpls-vpn-00.txt), October 1998.

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








































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8. Author Information

Osama S. Aboul-Magd                       Loa Andersson
Nortel Networks                           Director Bay Architecture Lab,EMEA
P O Box 3511 Station C                    Kungsgatan 34, PO Box 1788
Ottawa, ON K1Y 4H7                        111 97 Stockholm, Sweden
Canada                                    phone: +46 8 441 78 34
phone: +1 613 763-5827                    mobile +46 70 522 78 34
osama@NortelNetworks.com                  loa_andersson@baynetworks.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
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

Nancy Feldman                             Andre Fredette
IBM Corp.                                 Nortel Networks
17 Skyline Drive                          3 Federal Street
Hawthorne NY 10532                        Billerica, MA 01821
Phone:  914-784-3254                      fredette@baynetworks.com
nkf@us.ibm.com

Eric Gray                                 Joel M. Halpern
Lucent Technologies, Inc                  Newbridge Networks Inc.
1600 Osgood St.                           593 Herndon Parkway
North Andover, MA  01847                  Herndon, VA 20170
Phone: 603-659-3386                       phone: 1-703-736-5954
ewgray@lucent.com                         jhalpern@newbridge.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
jh@telia.fi




Jamoussi, et. al.          February 25, 1999                   [Page 28]


CR-LDP Specification             - 29 -                 Exp. August 1999


Bilel Jamoussi                            Timothy E. Kilty
Nortel Networks                           Northchurch Communications
P O Box 3511 Station C                    5 Corporate Drive,
Ottawa, ON K1Y 4H7                        Andover, MA 018110
Canada                                    phone: 978 691-4656
phone: +1 613 765-4814                    tkilty@northc.com
jamoussi@NortelNetworks.com

Andrew G. Malis                           Muckai K Girish
Ascend Communications, Inc.               SBC Technology Resources, Inc.
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

Kenneth Sundell                           Pasi Vaananen
Ericsson                                  Nokia Telecommunications
SE-126 25 Stockholm                       3 Burlington Woods Drive, Suite 250
Sweden                                    Burlington, MA 01803
kenneth.sundell@etx.ericsson.se           Phone: +1-781-238-4981
                                          pasi.vaananen@ntc.nokia.com

Tom Worster                               Liwen Wu
General DataComm, Inc.                    Alcatel U.S.A
5 Mount Royal Ave.                        44983 Knoll Square
Marlboro MA 01752                         Ashburn, Va. 20147
tom.worster@gdc.com                       USA
                                          Phone: (703) 724-2619
                                          FAX:   (703) 724-2005
                                          liwen.wu@adn.alcatel.com





















Jamoussi, et. al.          February 25, 1999                   [Page 29]


CR-LDP Specification             - 30 -                 Exp. August 1999


Appendix A: CRLSP Establishment Examples

A.1 Strict Explicit Route Example

   This appendix provides an example for the setup of a strictly  routed
   CRLSP.  In  this  example,  each  abstract  node  is represented by a
   specific node.

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

                             a         b         c
                    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.

   The ER-TLV is composed by a vector of three ER-Hop TLVs <a, b, c>.
   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> is part of the abstract node LSR2. 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 which now becomes <b , c>. Go to
      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

Jamoussi, et. al.          February 25, 1999                   [Page 30]


CR-LDP Specification             - 31 -                 Exp. August 1999


      already done is step 4 of Section 4.8.1 and the processing of the
      ER-TLV is 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> is part of the abstract node LSR4. 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.
      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 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 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 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 which completes the end-to-end
   CRLSP setup.

A.2. Node Groups and Specific Nodes Example

   A request at an ingress LSR to setup a CRLSP 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 calculated the explicit route and to create the Label
   Request Message.


Jamoussi, et. al.          February 25, 1999                   [Page 31]


CR-LDP Specification             - 32 -                 Exp. August 1999


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

   All the ER-Hop TLVs are strictly routed nodes.

   The setup procedure for this CRLSP 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 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.

Jamoussi, et. al.          February 25, 1999                   [Page 32]


CR-LDP Specification             - 33 -                 Exp. August 1999


      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, it returns a Label Mapping Message, that will
      traverse the same path as the Label Request Message in the
      opposite direction.






































Jamoussi, et. al.          February 25, 1999                   [Page 33]


CR-LDP Specification             - 34 -                 Exp. August 1999


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
   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.

   Packets 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


Jamoussi, et. al.          February 25, 1999                   [Page 34]


CR-LDP Specification             - 35 -                 Exp. August 1999


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

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 commit 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. Establishing CR-LSP Supporting Real-Time Applications

   In this scenario the customer needs to establish an LSP for
   supporting real-time  applications such voice and video. The 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 their values are specified by the user
   based on his requirements. 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 requires 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

Jamoussi, et. al.          February 25, 1999                   [Page 35]

CR-LDP Specification             - 36 -                 Exp. August 1999


   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 either the PDR, the PBS, or both.
   The new parameters 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. 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 either PDR and 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 parameters 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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