Encapsulation Methods for Transport of Ethernet over MPLS Networks
RFC 4448

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Network Working Group                                    L. Martini, Ed.
Request for Comments: 4448                                      E. Rosen
Category: Standards Track                            Cisco Systems, Inc.
                                                             N. El-Aawar
                                             Level 3 Communications, LLC
                                                                G. Heron
                                                                 Tellabs
                                                              April 2006

   Encapsulation Methods for Transport of Ethernet 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 Internet Society (2006).

Abstract

   An Ethernet pseudowire (PW) is used to carry Ethernet/802.3 Protocol
   Data Units (PDUs) over an MPLS network.  This enables service
   providers to offer "emulated" Ethernet services over existing MPLS
   networks.  This document specifies the encapsulation of
   Ethernet/802.3 PDUs within a pseudowire.  It also specifies the
   procedures for using a PW to provide a "point-to-point Ethernet"
   service.

Martini, et al.             Standards Track                     [Page 1]
RFC 4448          Encapsulation of Ethernet over MPLS         April 2006

Table of Contents

   1. Introduction ....................................................3
   2. Specification of Requirements ...................................6
   3. Applicability Statement .........................................6
   4. Details Specific to Particular Emulated Services ................7
      4.1. Ethernet Tagged Mode .......................................7
      4.2. Ethernet Raw Mode ..........................................8
      4.3. Ethernet-Specific Interface Parameter LDP Sub-TLV ..........8
      4.4. Generic Procedures .........................................9
           4.4.1. Raw Mode vs. Tagged Mode ............................9
           4.4.2. MTU Management on the PE/CE Links ..................11
           4.4.3. Frame Ordering .....................................11
           4.4.4. Frame Error Processing .............................11
           4.4.5. IEEE 802.3x Flow Control Interworking ..............11
      4.5. Management ................................................12
      4.6. The Control Word ..........................................12
      4.7. QoS Considerations ........................................13
   5. Security Considerations ........................................14
   6. PSN MTU Requirements ...........................................14
   7. Normative References ...........................................15
   8. Informative References .........................................15
   9. Significant Contributors .......................................17
   Appendix A. Interoperability Guidelines ...........................20
      A.1. Configuration Options .....................................20
      A.2. IEEE 802.3x Flow Control Considerations ...................21
   Appendix B. QoS Details ...........................................21
      B.1. Adaptation of 802.1Q CoS to PSN CoS .......................22
      B.2. Drop Precedence ...........................................23

Martini, et al.             Standards Track                     [Page 2]
RFC 4448          Encapsulation of Ethernet over MPLS         April 2006

1.  Introduction

   An Ethernet pseudowire (PW) allows Ethernet/802.3 [802.3] Protocol
   Data Units (PDUs) to be carried over a Multi-Protocol Label Switched
   [MPLS-ARCH] network.  In addressing the issues associated with
   carrying an Ethernet PDU over a packet switched network (PSN), this
   document assumes that a pseudowire (PW) has been set up by using a
   control protocol such as the one as described in [PWE3-CTRL].  The
   design of Ethernet pseudowire described in this document conforms to
   the pseudowire architecture described in [RFC3985].  It is also
   assumed in the remainder of this document that the reader is familiar
   with RFC 3985.

   The Pseudowire Emulation Edge-to-Edge (PWE3) Ethernet PDU consists of
   the Destination Address, Source Address, Length/Type, MAC Client
   Data, and padding extracted from a MAC frame as a concatenated octet
   sequence in their original order [PDU].

   In addition to the Ethernet PDU format used within the pseudowire,
   this document discusses:

      - Procedures for using a PW in order to provide a pair of Customer
        Edge (CE) routers with an emulated (point-to-point) Ethernet