RFC 3479 (rfc3479) - Page 2 of 52


Fault Tolerance for the Label Distribution Protocol (LDP)



Alternative Format: Original Text Document



RFC 3479              Fault Tolerance for the LDP          February 2003


   The issues and extensions described here are equally applicable to
   RFC 3212, "Constraint-Based LSP Setup Using LDP" (CR-LDP).

Table of Contents

   1. Conventions and Terminology used in this document..........3
   2. Contributing Authors.......................................4
   3. Introduction...............................................4
      3.1. Fault Tolerance for MPLS..............................4
      3.2. Issues with LDP.......................................5
   4. Overview of LDP FT Enhancements............................7
      4.1. Establishing an FT LDP Session........................8
           4.1.1 Interoperation with Non-FT LSRs.................8
      4.2. TCP Connection Failure................................9
           4.2.1 Detecting TCP Connection Failures...............9
           4.2.2 LDP Processing after Connection Failure.........9
      4.3. Data Forwarding During TCP Connection Failure........10
      4.4. FT LDP Session Reconnection..........................10
      4.5. Operations on FT Labels..............................11
      4.6. Check-Pointing.......................................11
           4.6.1 Graceful Termination...........................12
      4.7. Label Space Depletion and Replenishment..............13
      4.8. Tunneled LSPs........................................13
   5. FT Operations.............................................14
      5.1. FT LDP Messages......................................14
           5.1.1 Sequence Numbered FT Label Messages............14
           5.1.2 FT Address Messages............................15
           5.1.3 Label Resources Available Notifications........15
      5.2. FT Operation ACKs....................................17
      5.3. Preservation of FT State.............................17
      5.4. FT Procedure After TCP Failure.......................19
           5.4.1 FT LDP Operations During TCP Failure...........20
      5.5. FT Procedure After TCP Re-connection.................21
           5.5.1 Re-Issuing FT Messages.........................22
   6. Check-Pointing Procedures.................................22
      6.1 Check-Pointing with the Keepalive Message.............23
      6.2 Quiesce and Keepalive.................................23
   7. Changes to Existing Messages..............................24
      7.1. LDP Initialization Message...........................24
      7.2. LDP Keepalive Messages...............................25
      7.3. All Other LDP Session Messages.......................25
   8. New Fields and Values.....................................26
      8.1. Status Codes.........................................26
      8.2. FT Session TLV.......................................27
      8.3. FT Protection TLV....................................29
      8.4. FT ACK TLV...........................................32
      8.5. FT Cork TLV..........................................33
   9. Example Use...............................................34



Farrel                      Standards Track