Fault Tolerance for the Label Distribution Protocol (LDP)
RFC 3479
|
| Document |
Type |
|
RFC - Proposed Standard
(February 2003; No errata)
|
|
Last updated |
|
2015-10-14
|
|
Stream |
|
IETF
|
|
Formats |
|
plain text
pdf
html
bibtex
|
| Stream |
WG state
|
|
WG Document
|
|
Document shepherd |
|
No shepherd assigned
|
| IESG |
IESG state |
|
RFC 3479 (Proposed Standard)
|
|
Consensus Boilerplate |
|
Unknown
|
|
Telechat date |
|
|
|
Responsible AD |
|
Scott Bradner
|
|
Send notices to |
|
(None)
|
Network Working Group A. Farrel, Ed.
Request for Comments: 3479 Movaz Networks, Inc.
Category: Standards Track February 2003
Fault Tolerance for 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 (2003). All Rights Reserved.
IESG Note
This specification includes procedures for failure detection and
failover for a TCP connection carrying MPLS LDP control traffic, so
that it can be switched to a new TCP connection. It does not provide
a general approach to using multiple TCP connections to provide this
kind of fault tolerance. The specification lacks adequate guidance
for the timer and retry value choices related to the TCP connection
fault tolerance procedures. The specification should not serve as a
model for TCP connection fault tolerance design for any future
document, and users are advised to test configurations based on this
specification very carefully for problems such as premature
failovers.
Abstract
Multiprotocol Label Switching (MPLS) systems will be used in core
networks where system downtime must be kept to an absolute minimum.
Many MPLS Label Switching Routers (LSRs) may, therefore, exploit
Fault Tolerant (FT) hardware or software to provide high availability
of the core networks.
The details of how FT is achieved for the various components of an FT
LSR, including Label Distribution Protocol (LDP), the switching
hardware and TCP, are implementation specific. This document
identifies issues in the LDP specification in RFC 3036, "LDP
Specification", that make it difficult to implement an FT LSR using
the current LDP protocols, and defines enhancements to the LDP
specification to ease such FT LSR implementations.
Farrel Standards Track [Page 1]
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
Show full document text