Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)
RFC 4447

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Network Working Group                                    L. Martini, Ed.
Request for Comments: 4447                                      E. Rosen
Category: Standards Track                            Cisco Systems, Inc.
                                                             N. El-Aawar
                                            Level 3 Communications, LLC.
                                                                T. Smith
                                                 Network Appliance, Inc.
                                                                G. Heron
                                                                 Tellabs
                                                              April 2006

                    Pseudowire Setup and Maintenance
              Using the Label Distribution Protocol (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 (2006).

Abstract

   Layer 2 services (such as Frame Relay, Asynchronous Transfer Mode,
   and Ethernet) can be "emulated" over an MPLS backbone by
   encapsulating the Layer 2 Protocol Data Units (PDU) and transmitting
   them over "pseudowires".  It is also possible to use pseudowires to
   provide low-rate Time Division Multiplexed and a Synchronous Optical
   NETworking circuit emulation over an MPLS-enabled network.  This
   document specifies a protocol for establishing and maintaining the
   pseudowires, using extensions to Label Distribution Protocol (LDP).
   Procedures for encapsulating Layer 2 PDUs are specified in a set of
   companion documents.

Martini, et al.             Standards Track                     [Page 1]
RFC 4447                     PWE3 Using LDP                   April 2006

Table of Contents

   1. Introduction ....................................................3
   2. Specification of Requirements ...................................5
   3. The Pseudowire Label ............................................5
   4. Details Specific to Particular Emulated Services ................7
      4.1. IP Layer 2 Transport .......................................7
   5. LDP .............................................................7
      5.1. LDP Extensions .............................................8
      5.2. The PWid FEC Element .......................................8
      5.3. The Generalized PWid FEC Element ..........................10
           5.3.1. Attachment Identifiers .............................11
           5.3.2. Encoding the Generalized ID FEC Element ............13
                  5.3.2.1. Interface Parameters TLV ..................14
                  5.3.2.2. PW Grouping TLV ...........................14
           5.3.3. Signaling Procedures ...............................15
      5.4. Signaling of Pseudowire Status ............................16
           5.4.1. Use of Label Mappings Messages .....................16
           5.4.2. Signaling PW Status ................................17
           5.4.3. Pseudowire Status Negotiation Procedures ...........18
      5.5. Interface Parameters Sub-TLV ..............................19
   6. Control Word ...................................................20
      6.1. PW Types for Which the Control Word is REQUIRED ...........20
      6.2. PW Types for Which the Control Word is NOT Mandatory ......21
      6.3. LDP Label Withdrawal Procedures ...........................22
      6.4. Sequencing Considerations .................................23
           6.4.1. Label Advertisements ...............................23
           6.4.2. Label Release ......................................24
   7. IANA Considerations ............................................24
      7.1. LDP TLV TYPE ..............................................24
      7.2. LDP Status Codes ..........................................24
      7.3. FEC Type Name Space .......................................25
   8. Security Considerations ........................................25
      8.1. Data-Plane Security .......................................25
      8.2. Control-Plane Security ....................................26
   9. Acknowledgements ...............................................27
   10. Normative References ..........................................27
   11. Informative References ........................................27
   12. Additional Contributing Authors ...............................28
   Appendix A. C-bit Handling Procedures Diagram .....................31

Martini, et al.             Standards Track                     [Page 2]
RFC 4447                     PWE3 Using LDP                   April 2006