LDP Capabilities
RFC 5561

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Network Working Group                                          B. Thomas
Request for Comments: 5561                                       K. Raza
Updates: 5036                                        Cisco Systems, Inc.
Category: Standards Track                                    S. Aggarwal
                                                             R. Aggarwal
                                                        Juniper Networks
                                                             JL. Le Roux
                                                          France Telecom
                                                               July 2009

                           LDP Capabilities

Abstract

   A number of enhancements to the Label Distribution Protocol (LDP)
   have been proposed.  Some have been implemented, and some are
   advancing toward standardization.  It is likely that additional
   enhancements will be proposed in the future.  This document defines a
   mechanism for advertising LDP enhancements at session initialization
   time, as well as a mechanism to enable and disable enhancements after
   LDP session establishment.

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) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
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   Please review these documents carefully, as they describe your rights
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling

Thomas, et al.              Standards Track                     [Page 1]
RFC 5561                    LDP Capabilities                   July 2009

   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................2
      1.1. Conventions Used in This Document ..........................3
   2. The LDP Capability Mechanism ....................................3
      2.1. Capability Document ........................................4
   3. Specifying Capabilities in LDP Messages .........................4
      3.1. Backward Compatibility TLVs ................................6
   4. Capability Message ..............................................6
   5. Note on Terminology .............................................7
   6. Procedures for Capability Parameters in Initialization
      Messages ........................................................7
   7. Procedures for Capability Parameters in Capability Messages .....8
   8. Extensions to Error Handling ....................................9
   9. Dynamic Capability Announcement TLV .............................9
   10. Backward Compatibility ........................................10
   11. Security Considerations .......................................10
   12. IANA Considerations ...........................................11
   13. Acknowledgments ...............................................11
   14. References ....................................................11
      14.1. Normative References .....................................11
      14.2. Informative References ...................................11

1.  Introduction

   A number of enhancements to LDP as specified in [RFC5036] have been
   proposed.  These include LDP Graceful Restart [RFC3478], Fault
   Tolerant LDP [RFC3479], multicast extensions [MLDP], signaling for
   Layer 2 circuits [RFC4447], a method for learning labels advertised
   by next-next-hop routers in support of fast reroute node protection
   [NNHOP], upstream label allocation [UPSTREAM_LDP], and extensions for
   signaling inter-area Label Switched Paths (LSPs) [RFC5283].  Some
   have been implemented, and some are advancing toward standardization.
   It is also likely that additional enhancements will be implemented
   and deployed in the future.