Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires
RFC 5085

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Network Working Group                                     T. Nadeau, Ed.
Request for Comments: 5085                             C. Pignataro, Ed.
Category: Standards Track                            Cisco Systems, Inc.
                                                           December 2007

      Pseudowire Virtual Circuit Connectivity Verification (VCCV):
                   A Control Channel for Pseudowires

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.

Abstract

   This document describes Virtual Circuit Connectivity Verification
   (VCCV), which provides a control channel that is associated with a
   pseudowire (PW), as well as the corresponding operations and
   management functions (such as connectivity verification) to be used
   over that control channel.  VCCV applies to all supported access
   circuit and transport types currently defined for PWs.

Nadeau & Pignataro          Standards Track                     [Page 1]
RFC 5085                        PW VCCV                    December 2007

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Specification of Requirements  . . . . . . . . . . . . . .  5
   2.  Abbreviations  . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Overview of VCCV . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  CC Types and CV Types  . . . . . . . . . . . . . . . . . . . .  8
   5.  VCCV Control Channel for MPLS PWs  . . . . . . . . . . . . . . 10
     5.1.  VCCV Control Channel Types for MPLS  . . . . . . . . . . . 10
       5.1.1.  In-Band VCCV (Type 1)  . . . . . . . . . . . . . . . . 11
       5.1.2.  Out-of-Band VCCV (Type 2)  . . . . . . . . . . . . . . 12
       5.1.3.  TTL Expiry VCCV (Type 3) . . . . . . . . . . . . . . . 12
     5.2.  VCCV Connectivity Verification Types for MPLS  . . . . . . 13
       5.2.1.  ICMP Ping  . . . . . . . . . . . . . . . . . . . . . . 13
       5.2.2.  MPLS LSP Ping  . . . . . . . . . . . . . . . . . . . . 13
     5.3.  VCCV Capability Advertisement for MPLS PWs . . . . . . . . 13
       5.3.1.  VCCV Capability Advertisement LDP Sub-TLV  . . . . . . 14
   6.  VCCV Control Channel for L2TPv3/IP PWs . . . . . . . . . . . . 15
     6.1.  VCCV Control Channel Type for L2TPv3 . . . . . . . . . . . 16
     6.2.  VCCV Connectivity Verification Type for L2TPv3 . . . . . . 17
       6.2.1.  L2TPv3 VCCV using ICMP Ping  . . . . . . . . . . . . . 17
     6.3.  L2TPv3 VCCV Capability Advertisement for L2TPv3  . . . . . 17
       6.3.1.  L2TPv3 VCCV Capability AVP . . . . . . . . . . . . . . 17
   7.  Capability Advertisement Selection . . . . . . . . . . . . . . 19
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
     8.1.  VCCV Interface Parameters Sub-TLV  . . . . . . . . . . . . 19
       8.1.1.  MPLS VCCV Control Channel (CC) Types . . . . . . . . . 19
       8.1.2.  MPLS VCCV Connectivity Verification (CV) Types . . . . 20
     8.2.  PW Associated Channel Type . . . . . . . . . . . . . . . . 21
     8.3.  L2TPv3 Assignments . . . . . . . . . . . . . . . . . . . . 21
       8.3.1.  Control Message Attribute Value Pairs (AVPs) . . . . . 21
       8.3.2.  Default L2-Specific Sublayer Bits  . . . . . . . . . . 21
       8.3.3.  ATM-Specific Sublayer Bits . . . . . . . . . . . . . . 21
       8.3.4.  VCCV Capability AVP Values . . . . . . . . . . . . . . 22
   9.  Congestion Considerations  . . . . . . . . . . . . . . . . . . 23
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 24
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 26
     12.2. Informative References . . . . . . . . . . . . . . . . . . 26

Nadeau & Pignataro          Standards Track                     [Page 2]
RFC 5085                        PW VCCV                    December 2007

1.  Introduction

   There is a need for fault detection and diagnostic mechanisms that
   can be used for end-to-end fault detection and diagnostics for a
   Pseudowire, as a means of determining the PW's true operational
   state.  Operators have indicated in [RFC4377] and [RFC3916] that such
   a tool is required for PW operation and maintenance.  This document
   defines a protocol called Virtual Circuit Connectivity Verification
   (VCCV) that satisfies these requirements.  VCCV is, in its simplest
   description, a control channel between a pseudowire's ingress and
   egress points over which connectivity verification messages can be
   sent.

   The Pseudowire Edge-to-Edge Emulation (PWE3) Working Group defines a