GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc3212

Network Working Group B. Jamoussi, Editor, Nortel Networks Request for Comments: 3212 L. Andersson, Utfors AB Category: Standards Track R. Callon, Juniper Networks

                                         R. Dantu, Netrake Corporation
                                                  L. Wu, Cisco Systems
                                       P. Doolan, OTB Consulting Corp.
                                                            T. Worster
                                                 N. Feldman, IBM Corp.
                                           A. Fredette, ANF Consulting
                                              M. Girish, Atoga Systems
                                                    E. Gray, Sandburst
                                      J. Heinanen, Song Networks, Inc.
                                    T. Kilty, Newbridge Networks, Inc.
                                             A. Malis, Vivace Networks
                                                          January 2002
               Constraint-Based LSP Setup using LDP

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

 This document specifies mechanisms and TLVs (Type/Length/Value) for
 support of CR-LSPs (constraint-based routed Label Switched Path)
 using LDP (Label Distribution Protocol).
 This specification proposes an end-to-end setup mechanism of a CR-LSP
 initiated by the ingress LSR (Label Switching Router).  We also
 specify mechanisms to provide means for reservation of resources
 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].

Jamoussi, et al. Standards Track [Page 1] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

Table of Contents

 1. Introduction....................................................3
 2. Constraint-based Routing Overview...............................4
 2.1 Strict and Loose Explicit Routes...............................5
 2.2 Traffic Characteristics........................................5
 2.3 Preemption.....................................................5
 2.4 Route Pinning..................................................6
 2.5 Resource Class.................................................6
 3. Solution Overview...............................................6
 3.1 Required Messages and TLVs.....................................7
 3.2 Label Request Message..........................................7
 3.3 Label Mapping Message..........................................9
 3.4 Notification Message..........................................10
 3.5 Release , Withdraw, and Abort Messages........................11
 4. Protocol Specification.........................................11
 4.1 Explicit Route TLV (ER-TLV)...................................11
 4.2 Explicit Route Hop TLV (ER-Hop TLV)...........................12
 4.3 Traffic Parameters TLV........................................13
 4.3.1 Semantics...................................................15
 4.3.1.1 Frequency.................................................15
 4.3.1.2 Peak Rate.................................................16
 4.3.1.3 Committed Rate............................................16
 4.3.1.4 Excess Burst Size.........................................16
 4.3.1.5 Peak Rate Token Bucket....................................16
 4.3.1.6 Committed Data Rate Token Bucket..........................17
 4.3.1.7 Weight....................................................18
 4.3.2 Procedures..................................................18
 4.3.2.1 Label Request Message.....................................18
 4.3.2.2 Label Mapping Message.....................................18
 4.3.2.3 Notification Message......................................19
 4.4 Preemption TLV................................................19
 4.5 LSPID TLV.....................................................20
 4.6 Resource Class (Color) TLV....................................21
 4.7 ER-Hop semantics..............................................22
 4.7.1. ER-Hop 1: The IPv4 prefix..................................22
 4.7.2. ER-Hop 2: The IPv6 address.................................23
 4.7.3. ER-Hop 3:  The autonomous system number....................24
 4.7.4. ER-Hop 4: LSPID............................................24
 4.8. Processing of the Explicit Route TLV.........................26
 4.8.1. Selection of the next hop..................................26
 4.8.2. Adding ER-Hops to the explicit route TLV...................27
 4.9 Route Pinning TLV.............................................28
 4.10 CR-LSP FEC Element...........................................28
 5. IANA Considerations............................................29
 5.1 TLV Type Name Space...........................................29
 5.2 FEC Type Name Space...........................................30
 5.3 Status Code Space.............................................30

Jamoussi, et al. Standards Track [Page 2] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 6. Security Considerations........................................31
 7. Acknowledgments................................................31
 8. Intellectual Property Consideration............................31
 9. References.....................................................32
 Appendix A: CR-LSP Establishment Examples.........................33
 A.1 Strict Explicit Route Example.................................33
 A.2 Node Groups and Specific Nodes Example........................34
 Appendix B. QoS Service Examples..................................36
 B.1 Service Examples..............................................36
 B.2 Establishing CR-LSP Supporting Real-Time Applications.........38
 B.3 Establishing CR-LSP Supporting Delay Insensitive Applications.38
 Author's Addresses................................................39
 Full Copyright Statement..........................................42

1. Introduction

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

Jamoussi, et al. Standards Track [Page 3] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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:
  1. Strict and Loose Explicit Routing
  2. Specification of Traffic Parameters
  3. Route Pinning
  4. CR-LSP Preemption though setup/holding priorities
  5. Handling Failures
  6. LSPID
  7. 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
 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.

Jamoussi, et al. Standards Track [Page 4] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

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 path's traffic.

2.3 Preemption

 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 preemption.  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 preempt 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

Jamoussi, et al. Standards Track [Page 5] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 established, should have a lower chance of being preempted. Signaling
 a higher setup priority expresses the expectation that, in the case
 that resource are unavailable, the path is more likely to preempt
 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 "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 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 "colors" or "administrative groups".
 When a CR-LSP is being established, it's necessary to indicate which
 resource classes the CR-LSP can draw from.

3. Solution Overview

 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].

Jamoussi, et al. Standards Track [Page 6] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

    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]:
  1. Use of Basic and/or Extended Discovery Mechanisms.
  2. Use of the Label Request Message defined in [1] in downstream

on demand label advertisement mode with ordered control.

  1. Use of the Label Mapping Message defined in [1] in downstream

on demand mode with ordered control.

  1. Use of the Notification Message defined in [1].
  2. Use of the Withdraw and Release Messages defined in [1].
  3. 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 what's defined
 in [1]:
  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.
  1. 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.
  1. New status codes are defined to handle error notification for

failure of established paths specified in the CR-TLVs. All of

       the new status codes require that the F bit be set.
 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.
 Examples of CR-LSP establishment are given in Appendix A to
 illustrate how the mechanisms described in this document work.

Jamoussi, et al. Standards Track [Page 7] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

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 what's
 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):
  1. 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.
  1. The Optional Parameters TLV includes the definition of any of

the Constraint-based TLVs specified in Section 4.

  1. The Procedures to handle the Label Request Message are

augmented by the procedures for processing of the CR-TLVs as

       defined in Section 4.

Jamoussi, et al. Standards Track [Page 8] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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)  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     ER-TLV               (CR-LDP, optional)   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Traffic  TLV         (CR-LDP, optional)   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Pinning TLV          (CR-LDP, optional)   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Resource Class TLV (CR-LDP, optional)     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Preemption  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:
  1. The Label Mapping Message MUST include a single Label-TLV.
  1. 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.

Jamoussi, et al. Standards Track [Page 9] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 The encoding for the CR-LDP Label Mapping Message is as follows:
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0|   Label Mapping (0x0400)   |      Message Length            |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Message ID                                |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     FEC TLV                                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Label TLV                                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              Label Request Message ID TLV                     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     LSPID TLV            (CR-LDP, optional)   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                     Traffic  TLV         (CR-LDP, optional)   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.4 Notification Message

 The Notification Message is as defined in Section 3.5.1 of [1] and
 the Status TLV encoding is as defined in Section 3.4.6 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.  All of the new status codes require
 that the F bit be set.
 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.

Jamoussi, et al. Standards Track [Page 10] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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:
  1. Explicit Route TLV
  2. Explicit Route Hop TLV
  3. Traffic Parameters TLV
  4. Preemption TLV
  5. LSPID TLV
  6. Route Pinning TLV
  7. Resource Class TLV
  8. 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.

Jamoussi, et al. Standards Track [Page 11] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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 Route" Notification
 Message.
 Each ER-Hop TLV has the form:
 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |0|0|                 Type      |      Length                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |L|                                  Content //                 |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Jamoussi, et al. Standards Track [Page 12] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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."  Otherwise,
       the value of the attribute is "strict."  For brevity, we say
       that if the value of the ER-Hop attribute is loose then it is a
       "loose ER-Hop."  Otherwise, it's a "strict ER-Hop."  Further,
       we say that the abstract node of a strict or loose ER-Hop is a
       strict or a loose node, respectively.  Loose and strict nodes
       are always interpreted relative to their prior abstract nodes.
       The path between a strict node and its prior node MUST include
       only network nodes from the strict node and its prior abstract
       node.
       The path between a loose node and its prior node MAY include
       other network nodes, which are not part of the strict node or
       its prior abstract node.
 Contents
       A variable length field containing 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.

Jamoussi, et al. Standards Track [Page 13] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

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

Jamoussi, et al. Standards Track [Page 14] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

       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- 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.

Jamoussi, et al. Standards Track [Page 15] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

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.
 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:
  1. 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

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

decremented.

Jamoussi, et al. Standards Track [Page 16] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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 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 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.
 Thereafter, the token counts Tc and Te are updated CDR times per
 second as follows:
  1. If Tc is less than CBS, Tc is incremented by one, else
  2. 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:
  1. 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
  1. 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
  1. 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 doesn't need to be modeled
 according to the above formal specification.

Jamoussi, et al. Standards Track [Page 17] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

4.3.1.7 Weight

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

4.3.2 Procedures

4.3.2.1 Label Request Message

 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
 which the value of PDR is less than the value of CDR then it MUST
 send a Notification Message including the Status code "Traffic
 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 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 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.  In addition, the LSP should send a Notification
 Message upstream with the status code 'Label Request Aborted'.
 If the negotiation flag was set in the label request message, the
 egress LSR MUST include the (possibly negotiated) Traffic Parameters
 and Weight in the Label Mapping message.
 The Traffic Parameters and the Weight in a Label Mapping message MUST
 be forwarded unchanged.

Jamoussi, et al. Standards Track [Page 18] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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].  Further the F bit MUST be set.

4.4 Preemption TLV

 The default 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).
 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.

Jamoussi, et al. Standards Track [Page 19] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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.
 An "action indicator flag" is carried in the LSPID TLV.  This "action
 indicator flag" indicates explicitly the action that should be taken
 if the LSP already exists on the LSR receiving the message.
 After a CR-LSP is set up, its bandwidth reservation may need to be
 changed by the network operator, due to the new requirements for the
 traffic carried on that CR-LSP.  The "action indicator flag" is used
 indicate the need to modify the bandwidth and possibly other
 parameters of an established CR-LSP without service interruption.
 This feature has application in dynamic network resources management
 where traffic of different priorities and service classes is
 involved.
 The procedure for the code point "modify" is defined in [8].  The
 procedures for other flags are FFS.

Jamoussi, et al. Standards Track [Page 20] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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.

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
 network's topology to be pruned.

Jamoussi, et al. Standards Track [Page 21] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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 groups" or "colors" 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
       Set to indicate Loose hop.
       Cleared to indicate a strict hop.

Jamoussi, et al. Standards Track [Page 22] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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.

Jamoussi, et al. Standards Track [Page 23] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

4.7.3. ER-Hop 3: The autonomous system number

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

Jamoussi, et al. Standards Track [Page 24] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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 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.

Jamoussi, et al. Standards Track [Page 25] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

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
 effort attempt to determine a loop-free path.  Note that such best
 efforts may be overridden by local policy.
 To determine the next hop for the path, a node performs the following
 steps:
    1. The node receiving the Label Request Message must first
       evaluate the first ER-Hop.  If the L bit is not set in the
       first ER-Hop and if the node is not part of the abstract node
       described by the first ER-Hop, it has received the message in
       error, and should return a "Bad Initial ER-Hop Error" status.
       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" status 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.

Jamoussi, et al. Standards Track [Page 26] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

    5. Next, the node selects a next hop within the abstract node of
       the first ER-Hop that is along the path to the abstract node of
       the second ER-Hop.  If no such path exists then there are two
       cases:
       5.a If the second ER-Hop is a strict ER-Hop, then there is an
           error and the node should return a "Bad Strict Node Error"
           status.
       5.b Otherwise, if the second ER-Hop is a loose ER-Hop, then the
           node selects any next hop that is along the path to the
           next abstract node.  If no path exists within the MPLS
           domain, then there is an error, and the node should return
           a "Bad Loose Node Error" status.
    6. Finally, the node replaces the first ER-Hop with any ER-Hop
       that denotes an abstract node containing the next hop.  This is
       necessary so that when the explicit route is received by the
       next hop, it will be accepted.
    7. Progress the Label Request Message to the next hop.

4.8.2. Adding ER-Hops to the explicit route TLV

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

Jamoussi, et al. Standards Track [Page 27] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

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.

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;

Jamoussi, et al. Standards Track [Page 28] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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:
  1. TLV types.
  2. FEC types.
  3. Status codes.
 The following sections provide guidelines for managing these name
 spaces.

5.1 TLV Type Name Space

 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.

Jamoussi, et al. Standards Track [Page 29] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 Initial values for this range are specified in the following table:
       TLV                                               Type
       --------------------------------------         ----------
       Explicit 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 name space.  Further, RFC 3036 has
 assigned values 0x00 through 0x03.  FEC types 0 through 127 are
 available for assignment through IETF consensus action.  This
 specification makes the following additional assignment, using the
 policies outlined in [IANA]:
       FEC Element                                       Type
       --------------------------------------         ----------
       CR-LSP FEC Element                                0x04

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 0x04000000 - 0x040000FF.
 Following the policies outlined in [IANA], TLV types in this range
 are allocated through an IETF Consensus action.

Jamoussi, et al. Standards Track [Page 30] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 Initial values for this range are specified in the following table:
       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
       LSP Preempted                                  0x04000007
       Modify Request Not Supported                   0x04000008

6. Security Considerations

 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 LDP [1] design team.
 The list of authors provided with this document is a reduction of the
 original list.  Currently listed authors wish to acknowledge that a
 substantial amount was also contributed to this work by:
    Osama Aboul-Magd, Peter Ashwood-Smith, Joel Halpern,
    Fiffi Hellstrand, Kenneth Sundell and Pasi Vaananen.
 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 and 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.

Jamoussi, et al. Standards Track [Page 31] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

9. References

 [1] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and B.
     Thomas, "Label Distribution Protocol Specification", RFC 3036,
     January 2001.
 [2] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label
     Switching Architecture", RFC 3031, January 2001.
 [3] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M. and J. McManus,
     "Requirements for Traffic Engineering Over MPLS", RFC 2702,
     September 1999.
 [4] Gleeson, B., Lin, A., Heinanen, Armitage, G. and A. Malis, "A
     Framework for IP Based Virtual Private Networks", RFC 2764,
     February 2000.
 [5] Ash, J., Girish, M., Gray, E., Jamoussi, B. and G. Wright,
     "Applicability Statement for CR-LDP", RFC 3213, January 2002.
 [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
     Levels", BCP 14, RFC 2119, March 1997.
 [7] Boscher, C., Cheval, P., Wu, L. and E. Gray, "LDP State Machine",
     RFC 3215, January 2002.
 [8] Ash, J., Lee, Y., Ashwood-Smith, P., Jamoussi, B., Fedyk, D.,
     Skalecki, D. and L. Li, "LSP Modification Using CR-LDP", RFC
     3214, January 2002.

Jamoussi, et al. Standards Track [Page 32] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

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 document 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 document 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.

Jamoussi, et al. Standards Track [Page 33] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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
 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.

Jamoussi, et al. Standards Track [Page 34] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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
 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).

Jamoussi, et al. Standards Track [Page 35] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

    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.
    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.

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.
 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.

Jamoussi, et al. Standards Track [Page 36] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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
 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.

Jamoussi, et al. Standards Track [Page 37] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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.
 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.

Jamoussi, et al. Standards Track [Page 38] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 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.

10. Author's Addresses

 Loa Andersson
 Utfors Bredband AB
 Rasundavagen 12 169 29
 Solna
 Phone: +46 8 5270 50 38
 EMail: loa.andersson@utfors.se
 Ross Callon
 Juniper Networks
 1194 North Mathilda Avenue,
 Sunnyvale, CA  94089
 Phone: 978-692-6724
 EMail: rcallon@juniper.net
 Ram Dantu
 Netrake Corporation
 3000 Technology Drive, #100
 Plano Texas, 75024
 Phone: 214 291 1111
 EMail: rdantu@netrake.com
 Paul Doolan
 On The Beach Consulting Corp
 34 Mill Pond Circle
 Milford MA 01757
 Phone 617 513 852
 EMail: pdoolan@acm.org

Jamoussi, et al. Standards Track [Page 39] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 Nancy Feldman
 IBM Research
 30 Saw Mill River Road
 Hawthorne, NY 10532
 Phone:  914-784-3254
 EMail: Nkf@us.ibm.com
 Andre Fredette
 ANF Consulting
 62 Duck Pond Dr.
 Groton, MA  01450
 EMail: afredette@charter.net
 Eric Gray
 600 Federal Drive
 Andover, MA  01810
 Phone: (978) 689-1610
 EMail: eric.gray@sandburst.com
 Juha Heinanen
 Song Networks, Inc.
 Hallituskatu 16
 33200 Tampere, Finland
 EMail: jh@song.fi
 Bilel Jamoussi
 Nortel Networks
 600 Technology Park Drive
 Billerica, MA 01821
 USA
 Phone: +1 978 288-4506
 Mail: Jamoussi@nortelnetworks.com
 Timothy E. Kilty
 Island Consulting
 Phone: (978) 462 7091
 EMail: tim-kilty@mediaone.net
 Andrew G. Malis
 Vivace Networks
 2730 Orchard Parkway
 San Jose, CA 95134
 Phone: +1 408 383 7223
 EMail: Andy.Malis@vivacenetworks.com

Jamoussi, et al. Standards Track [Page 40] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

 Muckai K Girish
 Atoga Systems
 49026 Milmont Drive
 Fremont, CA 94538
 EMail: muckai@atoga.com
 Tom Worster
 Phone: 617 247 2624
 EMail: fsb@thefsb.org
 Liwen Wu
 Cisco Systems
 250 Apollo Drive
 Chelmsford, MA. 01824
 Phone: 978-244-3087
 EMail: liwwu@cisco.com

Jamoussi, et al. Standards Track [Page 41] RFC 3212 Constraint-Based LSP Setup using LDP January 2002

Full Copyright Statement

 Copyright (C) The Internet Society (2002).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

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

Jamoussi, et al. Standards Track [Page 42]

/data/webs/external/dokuwiki/data/pages/rfc/rfc3212.txt · Last modified: 2002/02/05 19:44 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki