LDP IGP Synchronization
RFC 5443
| Document | Type |
RFC - Informational
(March 2009; Errata)
Updated by RFC 6138
|
|
|---|---|---|---|
| Last updated | 2016-05-07 | ||
| Replaces | draft-ietf-mpls-igp-sync | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | WG Document | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 5443 (Informational) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | David Ward | ||
| Send notices to | rcallcon@juniper.net, isis-chairs@ietf.org | ||
Network Working Group M. Jork
Request for Comments: 5443 GENBAND
Category: Informational A. Atlas
British Telecom
L. Fang
Cisco Systems, Inc.
March 2009
LDP IGP Synchronization
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
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Jork, et al. Informational [Page 1]
RFC 5443 LDP IGP Synchronization March 2009
Abstract
In certain networks, there is dependency on the edge-to-edge Label
Switched Paths (LSPs) setup by the Label Distribution Protocol (LDP),
e.g., networks that are used for Multiprotocol Label Switching (MPLS)
Virtual Private Network (VPN) applications. For such applications,
it is not possible to rely on Internet Protocol (IP) forwarding if
the MPLS LSP is not operating appropriately. Blackholing of labeled
traffic can occur in situations where the Interior Gateway Protocol
(IGP) is operational on a link on which LDP is not. While the link
could still be used for IP forwarding, it is not useful for MPLS
forwarding, for example, MPLS VPN applications or Border Gateway
Protocol (BGP) route-free cores. This document describes a mechanism
to avoid traffic loss due to this condition without introducing any
protocol changes.
Table of Contents
1. Introduction ....................................................2
1.1. Conventions Used in This Document ..........................3
2. Proposed Solution ...............................................3
3. Applicability ...................................................4
4. Interaction with TE Tunnels .....................................5
5. Security Considerations .........................................5
6. References ......................................................6
6.1. Normative References .......................................6
6.2. Informative References .....................................6
7. Acknowledgments .................................................6
1. Introduction
LDP [RFC5036] establishes MPLS LSPs along the shortest path to a
destination as determined by IP forwarding. In a common network
design, LDP is used to provide Label Switched Paths throughout the
complete network domain covered by an IGP such as Open Shortest Path
First (OSPF) [RFC2328] or Intermediate System to Intermediate System
(IS-IS) [ISO.10589.1992]; i.e., all links in the domain have IGP as
well as LDP adjacencies.
A variety of services a network provider may want to deploy over an
LDP-enabled network depend on the availability of edge-to-edge label
switched paths. In a layer 2 (L2) or layer 3 (L3) VPN scenario, for
example, a given Provider-Edge (PE) router relies on the availability
of a complete MPLS forwarding path to the other PE routers for the
VPNs it serves. This means that all the links along the IP shortest
path from one PE router to the other need to have operational LDP
sessions, and the necessary label binding must have been exchanged
over those sessions. If only one link along the IP shortest path is
Jork, et al. Informational [Page 2]
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