MPLS Generic Associated Channel
RFC 5586
Network Working Group M. Bocci, Ed.
Request for Comments: 5586 M. Vigoureux, Ed.
Updates: 3032, 4385, 5085 Alcatel-Lucent
Category: Standards Track S. Bryant, Ed.
Cisco Systems
June 2009
MPLS Generic Associated Channel
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.
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Abstract
This document generalizes the applicability of the pseudowire (PW)
Associated Channel Header (ACH), enabling the realization of a
control channel associated to MPLS Label Switched Paths (LSPs) and
MPLS Sections in addition to MPLS pseudowires. In order to identify
the presence of this Associated Channel Header in the label stack,
this document also assigns one of the reserved MPLS label values to
the Generic Associated Channel Label (GAL), to be used as a label
based exception mechanism.
Bocci, et al. Standards Track [Page 1]
RFC 5586 G-ACh and GAL June 2009
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Objectives . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Requirements Language and Terminology . . . . . . . . . . 5
2. Generic Associated Channel Header . . . . . . . . . . . . . . 5
2.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Allocation of Channel Types . . . . . . . . . . . . . . . 6
3. ACH TLVs . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. ACH TLV Payload Structure . . . . . . . . . . . . . . . . 7
3.2. ACH TLV Header . . . . . . . . . . . . . . . . . . . . . . 8
3.3. ACH TLV Object . . . . . . . . . . . . . . . . . . . . . . 8
4. Generalized Exception Mechanism . . . . . . . . . . . . . . . 9
4.1. Relationship with Existing MPLS OAM Alert Mechanisms . . . 9
4.2. GAL Applicability and Usage . . . . . . . . . . . . . . . 10
4.2.1. GAL Processing . . . . . . . . . . . . . . . . . . . . 10
4.3. Relationship with RFC 3429 . . . . . . . . . . . . . . . . 13
5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 14
6. Congestion Considerations . . . . . . . . . . . . . . . . . . 15
7. Major Contributing Authors . . . . . . . . . . . . . . . . . . 15
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . . 18
Bocci, et al. Standards Track [Page 2]
RFC 5586 G-ACh and GAL June 2009
1. Introduction
There is a need for Operations, Administration, and Maintenance (OAM)
mechanisms that can be used for fault detection, diagnostics,
maintenance, and other functions on a pseudowire (PW) and a Label
Switched Path (LSP). These functions can be used between any two
Label Edge Routers (LERs)/Label Switching Router (LSRs) or
Terminating Provider Edge routers (T-PEs)/Switching Provider Edge
routers (S-PEs) along the path of an LSP or PW, respectively
[MPLS-TP]. Some of these functions can be supported using existing
tools such as Virtual Circuit Connectivity Verification (VCCV)
[RFC5085], Bidirectional Forwarding Detection for MPLS LSPs (BFD-
MPLS) [BFD-MPLS], LSP-Ping [RFC4379], or BFD-VCCV [BFD-VCCV].
However, a requirement has been indicated to augment this set of
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