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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 Corp.
Expiration Date: August 2001

                         O. Aboul-Magd, L. Andersson, P. Ashwood-Smith,
                       F. Hellstrand, K. Sundell, Nortel Networks Corp.
                                           R. Callon, Juniper Networks.
                                         R. Dantu, L. Wu, Cisco Systems
                         P. Doolan, T. Worster, Ennovate Networks Corp.
                                                  N. Feldman, IBM Corp.
                                            A. Fredette, PhotonEx Corp.
                                               M. Girish, Atoga Systems
                                                     E. Gray, Sandburst
                                    J. Halpern, Longitude Systems, Inc.
                                             J. Heinanen, Telia Finland
                                     T. Kilty, Newbridge Networks, Inc.
                                              A. Malis, Vivace Networks
                                  P. Vaananen, Nokia Telecommunications

                                                          February 2001


                  Constraint-Based LSP Setup using LDP

                     draft-ietf-mpls-cr-ldp-05.txt

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress.ö

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

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

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   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] and [3]. These requirements may be met by extending LDP for
   support of constraint-based routed label switched paths (CR-LSPs).
   Other uses for CR-LSPs include MPLS-based VPNs [4]. More information
   about the applicability of CR-LDP can be found in [5].

   This draft specifies mechanisms and TLVs for support of CR-LSPs
   using LDP.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL"
   in this document are to be interpreted as described in RFC 2119 [6].

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   Table of Contents


   1. Introduction....................................................4
   2. Constraint-based Routing Overview...............................4
   2.1 Strict and Loose Explicit Routes...............................5
   2.2 Traffic Characteristics........................................5
   2.3 Pre-emption....................................................6
   2.4 Route Pinning..................................................6
   2.5 Resource Class.................................................6
   3. Solution Overview...............................................6
   3.1 Required Messages and TLVs.....................................8
   3.2 Label Request Message..........................................8
   3.3 Label Mapping Message..........................................9
   3.4 Notification Message...........................................9
   3.5 Release , Withdraw, and Abort Messages........................10
   4. Protocol Specification.........................................10
   4.1 Explicit Route TLV (ER-TLV)...................................11
   4.2 Explicit Route Hop TLV (ER-Hop TLV)...........................11
   4.3 Traffic Parameters TLV........................................12
   4.3.1 Semantics...................................................14
   4.3.1.1 Frequency.................................................14
   4.3.1.2 Peak Rate.................................................14
   4.3.1.3 Committed Rate............................................14
   4.3.1.4 Excess Burst Size.........................................15
   4.3.1.5 Peak Rate Token Bucket....................................15
   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.....................................17
   4.3.2.3 Notification Message......................................17
   4.4 Preemption TLV................................................17
   4.5 LSPID TLV.....................................................18
   4.6 Resource Class (Color) TLV....................................20
   4.7 ER-Hop semantics..............................................20
   4.7.1. ER-Hop 1: The IPv4 prefix..................................20
   4.7.2. ER-Hop 2: The IPv6 address.................................21
   4.7.3. ER-Hop 3:  The autonomous system number....................21
   4.7.4. ER-Hop 4: LSPID............................................22
   4.8. Processing of the Explicit Route TLV.........................23
   4.8.1. Selection of the next hop..................................23
   4.8.2. Adding ER-Hops to the explicit route TLV...................25
   4.9 Route Pinning TLV.............................................25
   4.10 CR-LSP FEC Element...........................................26
   5. IANA Considerations............................................26
   5.1 TLV Type Name Space...........................................26
   5.2 FEC Type Name Space...........................................27
   5.3 Status Code Space.............................................27
   6. Security.......................................................28
   7. Acknowledgments................................................28
   8. Intellectual Property Consideration............................28

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   9. References.....................................................28
   10. AuthorÆs Addresses............................................29
   Appendix A: CR-LSP Establishment Examples.........................31
   A.1 Strict Explicit Route Example.................................31
   A.2 Node Groups and Specific Nodes Example........................32
   Appendix B. QoS Service Examples..................................35
   B.1 Service Examples..............................................35
   B.2 Establishing CR-LSP Supporting Real-Time Applications.........36
   B.3 Establishing CR-LSP Supporting Delay Insensitive Applications.37

1. Introduction

   The need for constraint-based routing (CR) in MPLS has been explored
   elsewhere [2], and [3].  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 (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
        - 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 [3]. Explicit Routing is a
   subset of the more general constraint-based routing where the
   constraint is the explicit route (ER). Other constraints are defined

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   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.

   Like any other LSP 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 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.

2.1 Strict and Loose Explicit Routes

   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 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 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
   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
   specify a constraint on the delay variation that the CR-LDP MPLS
   domain may introduce to a pathÆs 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 CR-LSP and the holdingPriority attributes
   of the existing 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 recommended
   default value is (4).

   The setupPriority of a CR-LSP should not be higher (numerically
   less) than its holdingPriority since it might bump an LSP and be
   bumped by the next "equivalentö 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 öLö bit set or where the next hop is an öabstract nodeö.  A
   CR-LSP may be setup using route pinning if it is undesirable to
   change the path used by an LSP 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 "colorsö or "administrative groupsö.
   When a CR-LSP is being established, itÆs necessary to indicate which
   resource classes the CR-LSP can draw from.

3. Solution Overview


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

        1. Meet the requirements outlined in [3] 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 specification is
        based on [1].

        3. Keep the solution simple.

   In this document, support for unidirectional point-to-point 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 CR-LSP) mechanisms defined in [1].

   In addition, the following functionality is added to whatÆs defined
   in [1]:

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

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

   Optional TLVs MUST be implemented to be compliant with the protocol.
   However, they are optionally carried in the CR-LDP messages to
   signal certain characteristics of the CR-LSP being established or
   modified.


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   Examples of CR-LSP 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 [1]. The reader can
   use [7] as an informational document about the state transitions,
   which relate to CR-LDP messages.

   The following subsections are meant as a cross-reference to the [1]
   document and indication of additional functionality beyond whatÆs
   defined in [1] where necessary.

   Note that use of the Status TLV is not limited to Notification
   messages as specified in Section 3.4.6 of [1].  A message other than
   a Notification message may carry a Status TLV as an Optional
   Parameter.  When a message other than a Notification carries a
   Status TLV the U-bit of the Status TLV should be set to 1 to
   indicate that the receiver should silently discard the TLV if
   unprepared to handle it.

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):

     - The Label Request Message MUST include a single FEC-TLV element.
     The CR-LSP FEC TLV element SHOULD be used. However, the other FEC-
     TLVs defined in [1] MAY be used instead for certain applications.

     - 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                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     LSPID TLV            (CR-LDP, mandatory)  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   |                     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 [1] with the
   following modifications:

     - The Label Mapping Message MUST include a single Label-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 CR-LSP and an upstream
        mapping has been requested.

        2. The LSR received a mapping from its downstream next hop LSR
        for an 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


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   The Notification Message is as defined in Section 3.5.1 of [1] and
   the Status TLV encoding is as defined in Section 3.4.6 of [1].
   Establishment of an CR-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 CR-LSP
   and the processing of the CR-TLV.

   The Notification Message MAY carry the LSPID TLV of the
   corresponding 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 Message defined in [1] MUST carry the LSPID TLV
   and MAY carry 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

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     - Route Pinning TLV
     - Resource Class TLV
     - CR-LSP 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|         Type = 0x0800     |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ER-Hop TLV 1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ER-Hop TLV 2                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                          ............                         ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          ER-Hop TLV n                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ER-TLV Type =
        0x0800.

   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 MUST not progress the label request message to
   the downstream LSR and MUST send back a "No Routeö 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|                 Type      |      Length                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|                                  Content //                 |

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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

        Value  Type
        ------ ------------------------
        0x0801 IPv4 prefix
        0x0802 IPv6 prefix
        0x0803 Autonomous system number
        0x0804 LSPID

   Length
        Specifies the length of the value field in bytes.

   L bit
        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.ö  Otherwise,
        the value of the attribute is "strict.ö  For brevity, we say
        that if the value of the ER-Hop attribute is loose then it is a
        "loose ER-Hop.ö  Otherwise, itÆs a "strict ER-Hop.ö  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 a node or abstract node
        which is one of the consecutive nodes that make up the
        explicitly routed LSP.

4.3 Traffic Parameters TLV

   The following sections describe the CR-LSP Traffic Parameters.  The
   required characteristics of a 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|        Type = 0x0810      |      Length = 24              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     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 Traffic
        Parameters TLV Type = 0x0810.

   Length
        Specifies the length of the value field in bytes = 24.

   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.

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

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

   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 CR-LSP.

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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 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 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 never
   in excess of the peak rate.

   The actual implementation of an LSR doesnÆt 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 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
   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.

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   Thereafter, the token counts Tc and Te are updated CDR times per
   second as follows:

     - 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 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 an LSR doesnÆt need to be modeled
   according to the above formal specification.

4.3.1.7 Weight

   The weight determines the CR-LSPÆs relative share of the possible
   excess bandwidth above its committed rate.  The definition of
   "relative shareö 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 Unavailableö 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.


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

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

   If, after possible Traffic Parameter negotiation, an LSR cannot
   support the CR-LSP Traffic Parameters then the LSR MUST send a
   Notification Message that contains the "Resource Unavailableö 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 Unavailableö 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 Abortedö.

   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 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 CR-LSP, it SHOULD
   release any resources that it possibly had reserved for the 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 decreasing
   the priority starting at the middle of the range.

   Since the Preemption TLV is an optional TLV, LSPs that are setup
   without an explicitly signaled preemption TLV SHOULD be treated as
   LSPs with the default setup and holding priorities (e.g., 4).

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   When an established LSP is preempted, the LSR that initiates the
   preemption sends a Withdraw Message upstream and a Release Message
   downstream.

   When an LSP in the process of being established (outstanding Label
   Request without getting a Label Mapping back) is preempted, the LSR
   that initiates the preemption, sends a Notification Message upstream
   and an Abort Message downstream.

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|     Type = 0x0820         |      Length = 4               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  SetPrio      | HoldPrio      |      Reserved                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the Preemption-TLV
        Type = 0x0820.

   Length
        Specifies the length of the value field in bytes = 4.

   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 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 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.

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   An "action indicator flagö is carried in the LSPID TLV. This "action
   indicator flagö 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 flagö is used
   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 "modifyö is defined in [8]. 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|       Type = 0x0821       |      Length = 4               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Reserved        |ActFlg |      Local CR-LSP ID          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Ingress LSR Router ID                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the LSPID-TLV
        Type =  0x0821.

   Length
        Specifies the length of the value field in bytes = 4.

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

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


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4.6 Resource Class (Color) TLV

   The Resource Class as defined in [3] is used to specify which links
   are acceptable by this CR-LSP. This information allows for the
   networkÆs 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|         Type = 0x0822     |      Length = 4               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             RsCls                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ResCls-TLV Type
        = 0x0822.

   Length
        Specifies the length of the value field in bytes = 4.

   RsCls
        The Resource Class bit mask indicating which of the 32
        "administrative groupsö or "colorsö of links the CR-LSP 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|         Type = 0x0801     |      Length = 8               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|      Reserved                               |    PreLen     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    IPv4 Address (4 bytes)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ER-Hop 1, IPv4
        Address, Type = 0x0801

   Length
        Specifies the length of the value field in bytes = 8.

   L Bit

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        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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|          0x0802           |      Length = 20              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|             Reserved                        |    PreLen     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  IPV6 address                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  IPV6 address (continued)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  IPV6 address (continued)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  IPV6 address (continued)                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ER-Hop 2, IPv6
        Address, Type = 0x0802

   Length
        Specifies the length of the value field in bytes = 20.

   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


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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|          0x0803           |      Length = 4               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|          Reserved           |                AS Number      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ER-Hop 3, AS
        Number, Type = 0x0803

   Length
        Specifies the length of the value field in bytes = 4.

   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
   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
   remove the LSP-ID Hop and forward the remaining ER-TLV in a Label
   Request message using an LDP session established with the LSR that
   is the specified CR-LSP's egress.  That LSR will continue processing

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   of the CR-LSP Label Request Message.  The result is a tunneled, or
   stacked, CR-LSP.

   To support labels negotiated for tunneled CR-LSP segments, an LDP
   session is required [1] between tunnel end points - possibly using
   the existing CR-LSP.  Use of the existence of the CR-LSP in lieu of
   a session, or other possible session-less approaches, is 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|          0x0804           |      Length = 8               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |L|          Reserved           |               Local LSPID     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Ingress LSR Router ID                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the ER-Hop 4, LSPID,
        Type = 0x0804

   Length
        Specifies the length of the value field in bytes = 8.

   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.

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


4.8. Processing of the Explicit Route TLV

4.8.1. Selection of the next hop

   A Label Request Message containing 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

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   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-Hopö 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 TLVö 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.

      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 Nodeö
           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 nodeö 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

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      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.

   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|          Type = 0x0823    |      Length = 4               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |P|                        Reserved                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the Pinning-TLV
        Type = 0x0823

   Length
        Specifies the length of the value field in bytes = 4.

   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.


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4.10 CR-LSP FEC Element

   A new FEC element is introduced in this specification to support CR-
   LSPs. A FEC TLV containing a FEC of Element type CR-LSP (0x04) is a
   CR-LSP FEC TLV. The CR-LSP FEC Element is an opaque FEC to be used
   only in Messages of CR-LSPs.

   A single FEC element MUST be included in the Label Request Message.
   The FEC Element SHOULD be the CR-LSP FEC Element. However, one of
   the other FEC elements (Type=0x01, 0x02, 0x03) defined in [1] MAY be
   in CR-LDP messages instead of the CR-LSP FEC Element for certain
   applications. A FEC TLV containing a FEC of Element type CR-LSP
   (0x04) is a CR-LSP FEC TLV.

        FEC Element     Type    Value
        Type name

        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|          Type = 0x0100    |      Length = 1               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | CR-LSP (4)    |
   +-+-+-+-+-+-+-+-+

   Type
        A fourteen-bit field carrying the value of the FEC TLV
        Type = 0x0100

   Length
        Specifies the length of the value field in bytes = 1.

   CR-LSP FEC Element Type

        0x04

5. IANA Considerations

   CR-LDP defines the following name spaces, which require management:

        - TLV types.
        - FEC types.
        - Status codes.

   The following sections provide guidelines for managing these name
   spaces.

5.1 TLV Type Name Space

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   RFC 3036 [1] defines the LDP TLV name space. This document further
   subdivides the range of RFC 3036 from that TLV space for TLVs
   associated with the CR-LDP in the range 0x0800 - 0x08FF.

   Following the policies outlined in [IANA], TLV types in this range
   are allocated through an IETF Consensus action.

   Initial values for this range are specified in the following table:

        TLV                                               Type
        --------------------------------------         ----------
        Explicite Route TLV                             0x0800
        Ipv4 Prefix ER-Hop TLV                          0x0801
        Ipv6 Prefix ER-Hop TLV                          0x0802
        Autonomous System Number ER-Hop TLV             0x0803
        LSP-ID ER-Hop TLV                               0x0804
        Traffic Parameters TLV                          0x0810
        Preemption TLV                                  0x0820
        LSPID TLV                                       0x0821
        Resource Class TLV                              0x0822
        Route Pinning TLV                               0x0823

5.2 FEC Type Name Space

   RFC 3036 defines the FEC Type TLV name space. This document further
   subdivides the range of RFC 3036 from that TLV space for TLVs
   associated with the CR-LDP in the range 100 - 116.

   Following the policies outlined in [IANA], TLV types in this range
   are allocated through an IETF Consensus action.

   Initial values for this range are specified in the follwing table:

        FEC Element TLV                                   Type
        --------------------------------------         ----------
        CR-LSP FEC Element TLV                          0x0100

5.3 Status Code Space

   RFC 3036 defines the Status Code name space. This document further
   subdivides the range of RFC 3036 from that TLV space for TLVs
   associated with the CR-LDP in the range 0x44000000 - 0x440000FF.

   Following the policies outlined in [IANA], TLV types in this range
   are allocated through an IETF Consensus action.

   Initial values for this range are specified in the follwing table:

        Status Code                                       Type
        --------------------------------------         ----------
        Bad Explicit Routing TLV Error                 0x44000001

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        Bad Strict Node Error                          0x44000002
        Bad Loose  Node Error                          0x44000003
        Bad Initial ER-Hop Error                       0x44000004
        Resource Unavailable                           0x44000005
        Traffic Parameters Unavailable                 0x44000006
        LSP Preempted                                  0x44000007
        Modify Request Not Supported                   0x44000008
        Setup Abort (Label Request Aborted in [1])     0x04000015

6. Security

   CR-LDP inherits the same security mechanism described in Section 4.0
   of [1] to protect against the introduction of spoofed TCP segments
   into LDP session connection streams.

7. Acknowledgments

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

   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, Ankur Anand, Adrian Farrel.

8. Intellectual Property Consideration

   The IETF has been notified of intellectual property rights claimed
   in regard to some or all of the specification contained in this
   document.  For more information consult the online list of claimed
   rights.

9. References

   1  Andersson et. al., "Label Distribution Protocol Specification"
      RFC 3036, January 2001.

   2  Rosen et. al., "Multiprotocol Label Switching Architecture",
      RFC 3031, January 2001.

   3  Awduche et. al., "Requirements for Traffic Engineering Over
      MPLS", RFC 2702, September 1999.

   4  Gleeson, et. al., "A Framework for IP Based Virtual Private
      Networks", RFC 2764, February 2000.

   5  B. Jamoussi, et. al., ôApplicability Statement for CR-LDPö, work
      in progress, (draft-ietf-mpls-crldp-applic-01), June 2000.

   6  S. Bradner, "Key words for use in RFCs to Indicate Requirement
      Levelsö, RFC 2119, March 1997.



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   7  L. Wu, et. al., "LDP State Machine", work in progress,
      (draft-ietf-mpls-ldp-state-03), January 2000.

   8  J. Ash, et. al., "LSP Modification Using CR-LDP", work in
      progress, (draft-ietf-mpls-crlsp-modify-02), October 2000.

10. AuthorÆs Addresses

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

   Peter Ashwood-Smith               Ross Callon
   Nortel Networks                   Juniper Networks
   P O Box 3511 Station C            1194 North Mathilda Avenue,
   Ottawa, ON K1Y 4H7                Sunnyvale, CA  94089
   Canada                            978-692-6724
   Phone: +1 613 763-4534            rcallon@juniper.net
   Petera@nortelnetworks.com

   Ram Dantu                         Paul Doolan
   Cisco Systems                     Ennovate Networks
   17919 Waterview Parkway          330 Codman Hill Rd
   Dallas, 75252                     Marlborough MA 01719
   +1 469 255 0716                   Phone: 978-263-2002
   rdantu@cisco.com                  Pdoolan@ennovatenetworks.com

   Nancy Feldman                     Andre Fredette
   IBM Research                      PhotonEx Corporation
   30 Saw Mill River Road            135 South Road
   Hawthorne, NY 10532               Bedford, MA 01730
   Phone:  914-784-3254              email: fredette@photonex.com
   Nkf@us.ibm.com                    phone: 781-275-8500

   Eric Gray                         Joel M. Halpern
   600 Federal Drive                 Longitude Systems, Inc.
   Andover, MA  01810                1319 Shepard Road
   Phone: (978) 689-1610             Sterling, VA 20164
   eric.gray@sandburst.com           703-433-0808 x207
                                     joel@longsys.com

   Juha Heinanen                     Fiffi Hellstrand
   Telia Finland, Inc.               Nortel Networks
   Myyrmaentie 2                     S:t Eriksgatan 115
   01600 VANTAA                      PO Box 6701, 113 85 Stockholm
   Finland                           Sweden

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   Tel: +358 41 500 4808             +46705593687
   Jh@telia.fi                       fiffi@nortelnetworks.com

   Bilel Jamoussi                    Timothy E. Kilty
   Nortel Networks Corp.             Newbridge Networks, Inc.
   600 Technology Park Drive         5 Corporate Drive
   Billerica, MA 01821               Andover, MA 01810
   USA                               USA
   Phone: +1 978 288-4506            phone: 978 691-4656
   Jamoussi@nortelnetworks.com       tkilty@northchurch.net

   Andrew G. Malis                   Muckai K Girish
   Vivace Networks                   Atoga Systems
   2730 Orchard Parkway              49026 Milmont Drive
   San Jose, CA 95134                Fremont, CA 94538
   Andy.Malis@vivacenetworks.com     E-mail: muckai@atoga.com
   Tel: +1 408 383 7223
   Fax: +1 408 904 4748

   Kenneth Sundell                   Pasi Vaananen
   Nortel Networks                   Nokia Telecommunications
   S:t Eriksgatan 115                3 Burlington Woods Drive,
   PO Box 6701                       Burlington, MA 01803
   113 85 Stockholm                  Phone: +1-781-238-4981
   Tel: +46 8 508 835 00             pasi.vaananen@nokia.com
   Fax: +46 8 508 835 01
   Ksundell@nortelnetworks.com

   Tom Worster                       Liwen Wu
   Ennovate Networks                 Cisco Systems
   60 Codman Hill Rd                 250 Apollo Drive
   Boxborough                        Chelmsford, MA. 01824
   MA 01719                          Tel: 978-244-3087.
   tworster@ennovatenetworks.com     liwwu@cisco.com


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Appendix A: CR-LSP Establishment Examples

A.1 Strict Explicit Route Example

   This appendix provides an example for the setup of a strictly routed
   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 node LSR2 is part of the abstract node 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, which now becomes <b, c>.
        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 node LSR4 is part of the abstract node 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 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 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 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 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, which completes the end-to-end
   CR-LSP setup.

A.2 Node Groups and Specific Nodes Example

   A request at ingress LSR to setup a 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 an ER-TLV defining the explicitly routed path. In our

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   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 CR-LSP (Node B).

   All the ER-Hop TLVs are strictly routed nodes.
   The setup procedure for this 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 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.

        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.


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        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 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 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 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 (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 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 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
   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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Jamoussi, et. al.   draft-ietf-mpls-cr-ldp-04.txt                  38


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