Subject: WG Review: Pseudo Wire Edge-to-Edge Emulation (pwe3)

From: The IESG <[email-masked]>
Date: Fri, 06 Apr 2001 14:49:32 -0400

A new IETF working group has been proposed in the Transport Area.
The IESG has not made any determination as yet. 

The following Description was submitted, and is provided for
informational purposes only:

Pseudo Wire Edge-to-Edge Emulation (pwe3)
------------------------------------------

Description of Working Group:
 
The basic idea of this working group is to develop standards for
the encapsulation and service emulation of pseudo wires: encapsulating
service-specific PDUs arriving at an ingress logical port and carrying
them across a tunnel, managing their timing, order or other
aspects entering and leaving the tunnel, to emulate the behavior and
characteristics of the service as well as possible.  Applicability
statements for each sevice will describe expects shortalls of the
emulation's faithfulness.

From the customer perspective, the pseudo wire is perceived as an
unshared link or circuit (or the appropriate unit) of the chosen
service.

Pseudo wires require the edge devices providing service interfaces
to use common service-specific techniques for encapsulating PDUs and
maintaining the service characteristics and behavior in the data flow.

The purpose of the WG is to pursue standardization of the framework and
the service-specific techniques for pseudo wires.

Assumptions

   PWE3 protocols and implementation focus on the edge-to-edge
   emulation and maintenance of service-specific pseudo-wires.
   Creation and placement of the tunnels is outside of the scope.

   Tunnels for PWE3 pseudo wires will use IP (either version), L2TP,
   or MPLS.  PWE3 will coordinate closely with the L2TP WG and its
   technologies.  PWE3 pseudo wires will have the same specification
   for all underlying PSNs (i.e., there will not be specific adaptation
   of PWE3 technology for MPLS that is distinct from that developed
   for IP and L2TP).

   PWE3 will not exert controls on the underlying PSN, but only
   function at the endpoints of the pseudo wire, though the endpoints
   may be configured to set diffserv codepoints in the tunneling
   datagrams.

   PWE3 will use RTP where necessary to perform clock recovery and
   other real-time emulation and maintenance.  This work will be
   coordinated with the AVT WG and payloads will follow RFC 2736.

   PWE3 will not strive for pseudo wires to perfectly emulate the
   characteristics of the native service.  For each type of pseudo
   wire, an applicability statement will describe the degree of
   similarity of a pseudo wire to the native service it emulates.

WG Objectives (in order of priority):

   Develop a requirements document to define the specific services and
   technology to be defined by the working group.

   Specify methods to ensure in-order final PDU delivery, perform clock
   recovery, and other edge-to-edge/inband signaling functions across
   the PSN.

   Specify methods with RTP (and possibly using header compression
   where needed) to ensure in-order final PDU delivery, perform clock 
   recovery, and other inband emulation and maintenance functions
   across the PSN, where required.

   Research the statistics and other network management information
   needed for tunnel operation and management, for example, to be able
   to determine when a circuit's up/down state has changed.

   Specify the security mechanisms to be used to protect the control of
   the PWE3 technology.  The protection of the encapsulated content of
   the pseudo wire is outside of scope.

   SPs may wish to exchange encapsulation control information at the
   administrative boundary with another network.  The working group will
   specify a mechanism to exchange encapsulation control information at
   an administrative boundary of the PSN.  Since an edge could be a
   native hand-off or hand-off of the encapsulated traffic across an
   administrative boundary, specify a security technique for the
   inter-administration hand-off functions.

Deliverables

  General documents:

    Requirements Document
    Architecture Document
    Enacapsulation Framework
    Common Edge-to-Edge Emulation/Maintenance Protocol
    Common PWE3 MIB
    Traceroute for Pseudo Wires

Individual encapsulation and emulation/maintenance document(s) for each 
of the following transported protocols, as well as applicability
statements:

    Ethernet (DIX Ethernet (100M, 1G, 10G), IEEE 802.3, 802.1q (VLAN)

    Frame Relay

    ATM

    TDM (e.g. DS1, DS3, SONET)

    MPLS (over IP or L2TP only)

Out of Scope

  Any multicast service not native to the emulated medium.
  Thus, Ethernet transmission to a "multicast" IEEE-48 address is in
  scope, while multicast services like MARS that are implemented on top 
  of the medium are out of scope.

  Methods to signal underlying network

Other Working Groups We Will Coordinate With

  MPLS, DIFFSERV, L2TP, AVT, CCAMP, TEWG, PPVPN, ROHC