2.3.21 Pseudowire Emulation Edge to Edge (pwe3)

NOTE: This charter is a snapshot of the 66th IETF Meeting in Montreal, Quebec Canada. It may now be out-of-date.

Last Modified: 2006-10-03


Stewart Bryant <stbryant@cisco.com>
Danny McPherson <danny@arbor.net>

Internet Area Director(s):

Jari Arkko <jari.arkko@piuha.net>
Mark Townsley <townsley@cisco.com>

Internet Area Advisor:

Mark Townsley <townsley@cisco.com>


Matthew Bocci <matthew.bocci@alcatel.co.uk>

Mailing Lists:

General Discussion: pwe3@ietf.org
To Subscribe: pwe3-request@ietf.org
In Body: subscribe your_email_address
Archive: http://www.ietf.org/mail-archive/web/pwe3/index.html

Description of Working Group:

Network transport service providers and their users are
seeking to rationalize their networks by migrating their
existing services and platforms onto IP or MPLS enabled
IP packet switched networks (PSN). This migration requires
communications services that can emulate the essential
properties of traditional communications links over a PSN.

Pseudowire Emulation Edge to Edge (PWE3) will specify the
encapsulation, transport, control, management, interworking and
security of services emulated over IETF specified PSNs.

A pseudowire emulates a point-to-point link, and provides a
single service which is perceived by its user as an unshared
link or circuit of the chosen service. It is not intended that
an emulated service will be indistinguishable from the service
that is being emulated. The emulation need only be sufficient
for the satisfactory operation of the service. Emulation
necessarily involves a degree of cost-performance trade-off.
In some cases it may be necessary to design more than one
emulation mechanism in order to resolve these design
conflicts. All emulated service definitions must include an
applicability statement describing the faithfulness of the
emulation. Switching, multiplexing, modification or other
operation on the traditional service, unless required as
part of the emulation, is out of the scope of the PWE3 WG.

PWE3 will make use of existing IETF specified mechanisms
unless there are technical reasons why the existing mechanisms
are insufficient or unnecessary.

PWE3 operates "edge to edge" and will not exert control on
the underlying PSN, other than to use any existing QoS or
path control mechanism to provide the required connectivity
between the two endpoints of the PW.

PWE3 will investigate mechanisms necessary to perform clock
recovery and other real-time signaling functions. This work will
be coordinated with the AVT WG and RTP will be used where

A PW operating over a shared PSN does not necessarily have
the same intrinsic security as a dedicated, purpose built,
network. In some cases this is satisfactory, while in other
cases it will be necessary to enhance the security of the PW
to emulate the intrinsic security of the emulated service.
PW specifications MUST include a description of how they
are to be operated over a shared PSN with adequate security.

Whilst a service provider may traffic engineer their network
in such a way that PW traffic will not cause significant
congestion, a PW deployed by an end-user may cause
congestion of the underlying PSN. Suitable congestion
avoidance mechanisms are therefore needed to protect the
Internet from the unconstrained deployment of PWs.

PWE3 will work closely with the L2VPN WG to ensure a clear
demarcation is defined for where PWE3 stops and L2VPN starts.
PWE3 will coordinate very closely with any WG that is
responsible for protocols which PWE3 intends to extend (e.g.,
the MPLS WG for LDP), as well as foster interaction with WGs
that intend to extend PWE3 protocols.

WG Objectives:

Specify the following PW types:

Ethernet, Frame Relay, PPP, HDLC, ATM, low-rate TDM,
SONET/SDH and Fibre Channel.

PWE3 will specify a PW type for the special case where the
access service payloads at both ends are known to consist
entirely of IP packets. PWE3 will not specify mechanisms
by which a PW connects two different access services.

Specify the control and management functions of chartered PW
types, to include PW setup, configuration, maintenance and
tear-down. The PWE3 WG will do this in its entirety for
MPLS PSNs, and the L2TPEXT WG will develop the L2TP specifics
for L2TPv3-based PWs.

Specify Operations and Management (OAM) mechanisms for all
PW types, suitable for operation over both IP/L2TPv3 and
MPLS PSNs, and capable of providing the necessary
interworking with the OAM mechanisms of the emulated

Further enhance PW specifications to enable more transparent
emulation when necessary, for example the retention of FCS
across a PW.

Define a mechanism for MPLS PWs that provides interoperability
with currently deployed equal cost multiple path (ECMP)
algorithms such that packets for a given PW follow the same
path through an MPLS PSN.

Define requirements for and mechanisms to provide
interconnection of PWs (to include inter-domain PWs).

Define requirements for and mechanisms to provide
protection and restoration of PWs.

Goals and Milestones:

Done  PWE3 WG started, organize editing teams.
Done  Hold interim meeting, including discussion of priority of service-specific documents and consider pruning some deliverables
Done  Accept drafts of service-specific documents as WG items
Done  PW Requirements Document Last Call
Done  TDM Circuit Documents Last Call
Done  ATM Documents Last Call
Done  Ethernet Documents Last Call
Done  Fragmentation LC
Done  TDM Requirements LC
Done  SONET Documents Last Call
Done  TDM Documents Last Call
Done  Frame Relay Documents Last Call
Done  FCS retention Last Call
Apr 2006  Multi-Segment PW Requirements LC
Apr 2006  VCCV LC
Apr 2006  PWE3 Services MIBs LC
Apr 2006  PPP/HDLC PW LC
May 2006  Wildcard FEC LC
May 2006  PW Protection and Restoration Requirements LC
Jun 2006  PW OAM Mapping LC
Jun 2006  Multi-Segment PW Architecture LC
Jul 2006  TDM Signaling LC
Aug 2006  PW Protection and Restoration Architecture
Aug 2006  Fiber Channel LC
Dec 2006  Multi-Segment PW LC
Mar 2007  PW Protection and Restoration LC


  • draft-ietf-pwe3-pw-mib-09.txt
  • draft-ietf-pwe3-pw-mpls-mib-10.txt
  • draft-ietf-pwe3-pw-tc-mib-08.txt
  • draft-ietf-pwe3-sonet-13.txt
  • draft-ietf-pwe3-cep-mib-09.txt
  • draft-ietf-pwe3-enet-mib-09.txt
  • draft-ietf-pwe3-atm-encap-11.txt
  • draft-ietf-pwe3-vccv-11.txt
  • draft-ietf-pwe3-fcs-retention-04.txt
  • draft-ietf-pwe3-cesopsn-07.txt
  • draft-ietf-pwe3-tdmoip-05.txt
  • draft-ietf-pwe3-tdm-mib-06.txt
  • draft-ietf-pwe3-cell-transport-06.txt
  • draft-ietf-pwe3-ms-pw-requirements-03.txt
  • draft-ietf-pwe3-segmented-pw-03.txt
  • draft-ietf-pwe3-tdm-control-protocol-extensi-02.txt
  • draft-ietf-pwe3-dynamic-ms-pw-02.txt
  • draft-ietf-pwe3-ms-pw-arch-02.txt
  • draft-ietf-pwe3-wildcard-pw-type-02.txt
  • draft-ietf-pwe3-aii-aggregate-01.txt
  • draft-ietf-pwe3-fc-encap-02.txt

    Request For Comments:

    RFC3916 I Requirements for Pseudo-Wire Emulation Edge-to-Edge (PWE3)
    RFC3985 I PWE3 Architecture
    RFC4197 I Requirements for Edge-to-Edge Emulation of Time Division Multiplexed (TDM) Circuits over Packet Switching Networks
    RFC4385 PS Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN
    RFC4446 BCP IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)
    RFC4447 PS Pseudowire Setup and Maintenance using the Label Distribution Protocol (LDP)
    RFC4448 PS Encapsulation Methods for Transport of Ethernet Over MPLS Networks
    RFC4553 PS Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)
    RFC4618 PS Encapsulation Methods for Transport of PPP/High-Level Data Link Control (HDLC) over MPLS Networks
    RFC4619 PS Encapsulation Methods for Transport of Frame Relay Over MPLS Networks
    RFC4623 PS Pseudowire Emulation Edge-to-Edge (PWE3) Fragmentation and Reassembly

    Meeting Minutes


    PWE3 Status
    draft-pan PWE3 protection
    Generic PWs
    PWE3 congestion
    VCCV Update