Pseudowire Emulation Edge to Edge (pwe3)

Last modified: 2014-11-19


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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. 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 protocols.

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 considerations.

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.

Goals and Milestones


PWE3 WG started, organize editing teams.


Hold interim meeting, including discussion of priority of service-specific documents and consider pruning some deliverables


Accept drafts of service-specific documents as WG items


PW Requirements Document Last Call


TDM Circuit Documents Last Call


ATM Documents Last Call


Ethernet Documents Last Call

Done Fragmentation LC

TDM Requirements LC


SONET Documents Last Call


TDM Documents Last Call

Done Frame Relay Documents Last Call

FCS retention Last Call

Done Multi-Segment PW Requirements LC



PWE3 Services MIBs LC




Wildcard FEC LC


TDM Signaling LC


Multi-Segment Architecture LC


Basic Pseudowire MIBs LC


Fiber Channel Encap LC


PW OAM Mapping LC


PW Protection and Restoration Requirements LC


PW Protection and Restoration Architecture


Multipath PW LC


Generic Associated Channel Header LC


Multi-Segment PW LC


PW Protection and Restoration LC


PW Status signalling in static/MPLS-TP


Packet PW Requirements / solution


Dynamic MS PW LC draft-ietf-pwe3-dynamic-ms-pw

Sep 2013

Congestion Considerations draft-ietf-pwe3-congestion-frmwk

Jun 2014

P2MP Requirements LC draft-ietf-pwe3-p2mp-pw-requirements

Jun 2014 Multisegment PW MIB
Jun 2014

Additional VCCV Channel Type using the GAL

Jun 2014 VCCV capability negotiation for MPLS-TP OAM tools draft-ietf-pwe3-mpls-tp-cv-adv
Sep 2014

P2MP PW Signaling (root initiated) draft-ietf-pwe3-p2mp-pw

Sep 2014 Security Considerations LC
Nov 2014 P2MP PW Signaling (leaf initiated)


Request for Comments

  • RFC 3916 Requirements for Pseudo-Wire Emulation Edge-to-Edge (PWE3) (Informational)

  • RFC 3985 Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture (Informational) Updated by RFC5462

  • RFC 4197 Requirements for Edge-to-Edge Emulation of Time Division Multiplexed (TDM) Circuits over Packet Switching Networks (Informational)

  • RFC 4385 Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN Proposed Standard) Updated by RFC5586

  • RFC 4446 IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3) (Best Current Practice)

  • RFC 4447 Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)  (Proposed Standard) Updated by RFC6723, RFC6870, RFC7358

  • RFC 4448 Encapsulation Methods for Transport of Ethernet over MPLS Networks  (Proposed Standard) Updated by RFC5462

  • RFC 4553 Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)  (Proposed Standard)

  • RFC 4618 Encapsulation Methods for Transport of PPP/High-Level Data Link Control (HDLC) over MPLS Networks  (Proposed Standard)

  • RFC 4619 Encapsulation Methods for Transport of Frame Relay over Multiprotocol Label Switching (MPLS) Networks      (Proposed Standard)

  • RFC 4623 Pseudowire Emulation Edge-to-Edge (PWE3) Fragmentation and Reassembly (Proposed Standard)

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

  • RFC 4720 Pseudowire Emulation Edge-to-Edge (PWE3) Frame Check Sequence Retention                (Proposed Standard)

  • RFC 4816 Pseudowire Emulation Edge-to-Edge (PWE3) Asynchronous Transfer Mode (ATM) Transparent Cell Transport Service (Proposed Standard)

  • RFC 4842 Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP) (Proposed Standard)

  • RFC 4863 Wildcard Pseudowire Type  (Proposed Standard)  

  • RFC 5003 Attachment Individual Identifier (AII) Types for Aggregation  (Proposed Standard)

  • RFC 5085 Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires (Proposed Standard) Updated by RFC5586 

  • RFC 5086 Structure-Aware Time Division Multiplexed (TDM) Circuit Emulation Service over Packet Switched Network (CESoPSN) (Informational)         

  • RFC 5087 Time Division Multiplexing over IP (TDMoIP)  (Informational)

  • RFC 5254 Requirements for Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3)     (Informational)

  • RFC 5287 Control Protocol Extensions for the Setup of Time-Division Multiplexing (TDM) Pseudowires in MPLS Networks (Proposed Standard)  

  • RFC 5542 Definitions of Textual Conventions for Pseudowire (PW) Management  (Proposed Standard)

  • RFC 5601 Pseudowire (PW) Management Information Base (MIB) (Proposed Standard)

  • RFC 5602 Pseudowire (PW) over MPLS PSN Management Information Base (MIB)     (Proposed Standard)

  • RFC 5603 Ethernet Pseudowire (PW) Management Information Base (MIB) (Proposed Standard)

  • RFC 5604 Managed Objects for Time Division Multiplexing (TDM) over Packet Switched Networks (PSNs) (Proposed Standard)          

  • RFC 5605 Managed Objects for ATM over Packet Switched Networks (PSNs) (Proposed Standard)

  • RFC 5659 An Architecture for Multi-Segment Pseudowire Emulation Edge-to-Edge (Informational)

  • RFC 5885 Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit Connectivity Verification (VCCV) (Proposed Standard) Updated by RFC6478

  • RFC 5994 Application of Ethernet Pseudowires to MPLS Transport Networks (Informational)

  • RFC 6073 Segmented Pseudowire  (Proposed Standard) Updated by RFC6723, RFC7267

  • RFC 6240 Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP) MIB Using SMIv2(Proposed Standard)

  • RFC 6307 Encapsulation Methods for Transport of Fibre Channel Traffic over MPLS Networks (Proposed Standard)

  • RFC 6310 Pseudowire (PW) Operations, Administration, and Maintenance (OAM) Message Mapping (Proposed Standard)

  • RFC 6391 Flow-Aware Transport of Pseudowires over an MPLS Packet Switched Network  (Proposed Standard) Updated by RFC7274

  • RFC 6423 Using the Generic Associated Channel Label for Pseudowire in the MPLS Transport Profile (MPLS-TP) (Proposed Standard)

  • RFC 6478 Pseudowire Status for Static Pseudowires (Proposed Standard) Updated by RFC7274

  • RFC 6658 Packet Pseudowire Encapsulation over an MPLS PSN  (Proposed Standard)

  • RFC 6667 LDP 'Typed Wildcard' Forwarding Equivalence Class (FEC) for PWid and Generalized PWid FEC Elements (Proposed Standard)

  • RFC 6718 Pseudowire Redundancy (Informational)

  • RFC 6723 Update of the Pseudowire Control-Word Negotiation Mechanism (Proposed Standard)

  • RFC 6870 Pseudowire Preferential Forwarding Status Bit (Proposed Standard)

  • RFC 7023 MPLS and Ethernet Operations, Administration, and Maintenance (OAM) Interworking (Proposed Standard)

  • RFC 7079 The Pseudowire (PW) and Virtual Circuit Connectivity Verification (VCCV) Implementation Survey Results (Informational)

  • RFC 7189 Virtual Circuit Connectivity Verification (VCCV) Capability Advertisement for MPLS Transport Profile (MPLS-TP) Proposed Standard)

  • RFC 7267 Dynamic Placement of Multi-Segment Pseudowires     (Proposed Standard)

  • RFC 7275 Inter-Chassis Communication Protocol for Layer 2 Virtual Private Network (L2VPN) Provider Edge (PE) Redundancy (Proposed Standard)

  • RFC 7338 Requirements and Framework for Point-to-Multipoint Pseudowires over MPLS Packet Switched Networks (Informational)

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