Pseudowire Emulation Edge to Edge

Document Charter Pseudowire Emulation Edge to Edge WG (pwe3)
Title Pseudowire Emulation Edge to Edge
Last updated 2001-05-04
State Approved
WG State Concluded
IESG Responsible AD Adrian Farrel
Charter Edit AD (None)
Send notices to (None)


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.
  Some service providers wish to use MPLS technology to
  replace existing transport network infrastructure, relying
  upon pseudowire technology is an integral component of
  these network convergence architectures.
  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 or point-to-multipoint
  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 endpoints of the PW.
  PWE3 will co-ordinate this with the AVT and TICTOC WGs.
  Where AVT or TICTOC require extensions to PWs to support
  time or frequency transfer this work will be undertaken by
  the PWE3 WG in co-ordination with the these WGs.
  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.
  PWE3 will work with the MPLS, L2VPN and other relevant WGs
  for definitions of common solutions for the secure operation
  of pseudowires.
  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.  Congestion 
  avoidance may be more difficult with P2MP pseudowires than
  P2P pseudowires. The WG will consider both cases.
  PWE3 will work closely with the L2VPN WG to ensure a clear
  demarcation is defined for where PWE3 stops and L2VPN starts,
  in particular in defining point-multipoint (P2MP) PWs.
  PWE3 will work with MPLS and L2VPN to enhance the OAM suite
  for transport applications. 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
  The IETF PWE3 WG is the design authority for pseudo-wire
  over IP/MPLS PSN technology. An entity or individual that
  wishes to propose extensions or changes to this technology
  must bring the corresponding proposals to the PWE3 WG that
  would treat them via a process similar to one described in
  RFC 4929 for the MPLS/GMPLS change process.
  WG Objectives:
  Specify the following PW types:
  Most of the initial specific PW types have been specified
  (e.g., Frame Realy, Ethernet, ATM). Investigation into
  and specification of a "generic PW" type and/or MPLS PW
  should be undertaken.
  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
  unless the Network Layer protocol is IP or MPLS.
  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
  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.
  Publish document outlining PW-specific congestion avoidance
  and response guidelines.
  Publish document outlining PW-specific security
  Specify requirements and mechanisms for P2MP functionality
  for PWs. This work will be coordinated with the L2VPN and
  MPLS working groups.
  Publish requirements and specification for PW to take
  advantage of multiple PSN paths that exist between PEs.
  Publish requirements and specification for enhanced OAM.
  Include extensions to the PWE3 protocols and RFCs
  necessary to create an MPLS Transport Profile (MPLS-TP).
  The work on the MPLS TP needs to be coordinated between
  three primary working groups (MPLS, PWE3, L2VPN and CCAMP) that
  are chartered to do MPLS TP work.