Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks
RFC 4717

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Network Working Group                                         L. Martini
Request for Comments: 4717                                  J. Jayakumar
Category: Standards Track                            Cisco Systems, Inc.
                                                                M. Bocci
                                                                 Alcatel
                                                             N. El-Aawar
                                             Level 3 Communications, LLC
                                                              J. Brayley
                                                        ECI Telecom Inc.
                                                              G. Koleyni
                                                         Nortel Networks
                                                           December 2006

                Encapsulation Methods for Transport of
          Asynchronous Transfer Mode (ATM) over MPLS Networks

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 IETF Trust (2006).

Abstract

   An Asynchronous Transfer Mode (ATM) Pseudowire (PW) is used to carry
   ATM cells over an MPLS network.  This enables service providers to
   offer "emulated" ATM services over existing MPLS networks.  This
   document specifies methods for the encapsulation of ATM cells within
   a pseudowire.  It also specifies the procedures for using a PW to
   provide an ATM service.

Martini, et al.             Standards Track                     [Page 1]
RFC 4717            Encapsulation for ATM over MPLS        December 2006

Table of Contents

   1. Introduction ....................................................3
   2. Specification of Requirements ...................................4
   3. Applicability Statement .........................................4
   4. Terminology .....................................................4
   5. General Encapsulation Method ....................................6
      5.1. The Control Word ...........................................6
           5.1.1. The Generic Control Word ............................7
           5.1.2. The Preferred Control Word ..........................8
           5.1.3. Setting the Sequence Number Field in the
                  Control Word ........................................9
      5.2. MTU Requirements ...........................................9
      5.3. MPLS Shim S Bit Value .....................................10
      5.4. MPLS Shim TTL Values ......................................10
   6. Encapsulation Mode Applicability ...............................10
      6.1. ATM N-to-One Cell Mode ....................................11
      6.2. ATM One-to-One Cell Encapsulation .........................13
      6.3. AAL5 SDU Frame Encapsulation ..............................13
      6.4. AAL5 PDU Frame Encapsulation ..............................14
   7. ATM OAM Cell Support ...........................................15
      7.1. VCC Case ..................................................15
      7.2. VPC Case ..................................................16
      7.3. SDU/PDU OAM Cell Emulation Mode ...........................16
      7.4. Defect Handling ...........................................17
   8. ATM N-to-One Cell Mode .........................................18
      8.1. ATM N-to-One Service Encapsulation ........................19
   9. ATM One-to-One Cell Mode .......................................21
      9.1. ATM One-to-One Service Encapsulation ......................21
      9.2. Sequence Number ...........................................22
      9.3. ATM VCC Cell Transport Service ............................22
      9.4. ATM VPC Services ..........................................24
           9.4.1. ATM VPC Cell Transport Services ....................25
   10. ATM AAL5 CPCS-SDU Mode ........................................26
      10.1. Transparent AAL5 SDU Frame Encapsulation .................27
   11. AAL5 PDU Frame Mode ...........................................28
      11.1. Transparent AAL5 PDU Frame Encapsulation .................28
      11.2. Fragmentation ............................................30
           11.2.1. Procedures in the ATM-to-PSN Direction ............30
           11.2.2. Procedures in the PSN-to-ATM Direction ............31
   12. Mapping of ATM and PSN Classes of Service .....................31
   13. ILMI Support ..................................................32
   14. ATM-Specific Interface Parameter Sub-TLVs .....................32
   15. Congestion Control ............................................32