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LDP Specification
RFC 3036

Document type: RFC - Proposed Standard (January 2001; Errata)
Obsoleted by RFC 5036
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Document shepherd: No shepherd assigned

IESG State: RFC 3036 (Proposed Standard)
Responsible AD: (None)
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Network Working Group                                        L. Andersson
Request for Comments: 3036                           Nortel Networks Inc.
Category: Standards Track                                       P. Doolan
                                                        Ennovate Networks
                                                               N. Feldman
                                                                 IBM Corp
                                                              A. Fredette
                                                            PhotonEx Corp
                                                                B. Thomas
                                                      Cisco Systems, Inc.
                                                             January 2001

                           LDP Specification

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 (2001).  All Rights Reserved.

Abstract

   The architecture for Multi Protocol Label Switching (MPLS) is
   described in RFC 3031.  A fundamental concept in MPLS is that two
   Label Switching Routers (LSRs) must agree on the meaning of the
   labels used to forward traffic between and through them.  This common
   understanding is achieved by using a set of procedures, called a
   label distribution protocol, by which one LSR informs another of
   label bindings it has made.  This document defines a set of such
   procedures called LDP (for Label Distribution Protocol) by which LSRs
   distribute labels to support MPLS forwarding along normally routed
   paths.

Andersson, et al.           Standards Track                     [Page 1]
RFC 3036                   LDP Specification                January 2001

Table of Contents

   1          LDP Overview  .......................................   5
   1.1        LDP Peers  ..........................................   6
   1.2        LDP Message Exchange  ...............................   6
   1.3        LDP Message Structure  ..............................   7
   1.4        LDP Error Handling  .................................   7
   1.5        LDP Extensibility and Future Compatibility  .........   7
   1.6        Specification Language  .............................   7
   2          LDP Operation  ......................................   8
   2.1        FECs  ...............................................   8
   2.2        Label Spaces, Identifiers, Sessions and Transport  ..   9
   2.2.1      Label Spaces  .......................................   9
   2.2.2      LDP Identifiers  ....................................  10
   2.2.3      LDP Sessions  .......................................  10
   2.2.4      LDP Transport  ......................................  11
   2.3        LDP Sessions between non-Directly Connected LSRs  ...  11
   2.4        LDP Discovery   .....................................  11
   2.4.1      Basic Discovery Mechanism  ..........................  12
   2.4.2      Extended Discovery Mechanism  .......................  12
   2.5        Establishing and Maintaining LDP Sessions  ..........  13
   2.5.1      LDP Session Establishment  ..........................  13
   2.5.2      Transport Connection Establishment  .................  13
   2.5.3      Session Initialization  .............................  14
   2.5.4      Initialization State Machine  .......................  17
   2.5.5      Maintaining Hello Adjacencies  ......................  20
   2.5.6      Maintaining LDP Sessions  ...........................  20
   2.6        Label Distribution and Management  ..................  21
   2.6.1      Label Distribution Control Mode  ....................  21
   2.6.1.1    Independent Label Distribution Control  .............  21
   2.6.1.2    Ordered Label Distribution Control  .................  21
   2.6.2      Label Retention Mode  ...............................  22
   2.6.2.1    Conservative Label Retention Mode  ..................  22
   2.6.2.2    Liberal Label Retention Mode  .......................  22
   2.6.3      Label Advertisement Mode  ...........................  23
   2.7        LDP Identifiers and Next Hop Addresses  .............  23
   2.8        Loop Detection  .....................................  24
   2.8.1      Label Request Message  ..............................  24
   2.8.2      Label Mapping Message  ..............................  26
   2.8.3      Discussion  .........................................  27

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