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Versions: (draft-jounay-pwe3-p2mp-pw-requirements) 00 01 02 03 04 05 06 07 08 10

Network Working Group                                  F. Jounay, Ed.
Internet-Draft                                             Orange CH
Category: Informational                                Y. Kamite, Ed.
Expires: November 15, 2014                        NTT Communications
                                                            G. Heron
                                                       Cisco Systems
                                                            M. Bocci
                                                      Alcatel-Lucent
                                                        May 15, 2014

     Requirements and Framework for Point-to-Multipoint Pseudowires
                 over MPLS Packet Switched Networks

              draft-ietf-pwe3-p2mp-pw-requirements-08.txt


Abstract

   This document presents a set of requirements and a framework for
   providing a Point-to-Multipoint Pseudowire (PW) over MPLS Packet
   Switched Networks. The requirements identified in this document are
   related to architecture, signaling and maintenance aspects of Point-
   to-Multipoint PW operation. They are proposed as guidelines for the
   standardization of such mechanisms. Among other potential
   applications, Point-to-Multipoint PWs can be used to optimize the
   support of multicast layer 2 services (Virtual Private LAN Service
   and Virtual Private Multicast Service) as defined in the Layer 2
   Virtual Private Network Working Group.

Status of This Memo


   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.
   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 15, 2014.





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Copyright Notice


   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document MUST
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

 1. Introduction.....................................................3
   1.1. Problem Statement........................................... 3
   1.2. Scope of this document...................................... 3
   1.3. Conventions used in this document........................... 4
 2. Definition...................................................... 4
   2.1. Acronyms.................................................... 4
   2.2. Terminology ................................................ 4
 3. P2MP PW Requirements.............................................5
   3.1. Reference Model............................................. 5
   3.2. P2MP PW and Underlying Layer ............................... 7
   3.3. P2MP PW Construction........................................ 9
   3.4. P2MP PW Signaling Requirements.............................. 9
     3.4.1. PW Identifier........................................... 9
     3.4.2. PW type mismatch ....................................... 9
     3.4.3. Interface Parameters sub-TLV............................ 9
     3.4.4. Leaf Grafting/Pruning ..................................10
     3.4.5. Failure Detection and Reporting.........................10
     3.4.6. Protection and Restoration..............................11
     3.4.7. Scalability.............................................12
 4. Backward Compatibility..........................................12
 5. Security Considerations.........................................13
 6. IANA Considerations.............................................13
 7. Contributing Aurhors............................................13
 8. Acknowledgments.................................................14
 9. References......................................................14
   9.1. Normative References........................................14
   9.2. Informative References......................................14






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1. Introduction
1.1. Problem Statement

   As defined in the pseudowire architecture [RFC3985], a Pseudowire
   (PW) is a mechanism that emulates the essential attributes of a
   telecommunications service (such as a T1 leased line or Frame Relay)
   over an IP or MPLS Packet Switched Network. It provides a single
   service which is perceived by its user as an unshared link or circuit
   of the chosen service.  A Pseudowire is used to transport layer 1 or
   layer 2 traffic (e.g. Ethernet, TDM, ATM, and FR) over a layer 3 PSN.
   Pseudowire Emulation Edge-to-Edge (PWE3) operates "edge to edge" to
   provide the required connectivity between the two endpoints of the
   PW.

   The Point-to-Multipoint (P2MP) topology described in
   [I-D.ietf-l2vpn-vpms-frmwk-requirements] and required to provide P2MP
   Layer2 VPN service can be achieved using one or more P2MP PWs.
   The use of PW encapsulation enables P2MP services transporting layer1
   or layer2 data.  This could be achieved using a set of point to point
   PWs, with traffic replication on the Provider Edge (PE), but at the
   cost of bandwidth efficiency, as duplicate traffic would be carried
   multiple times on shared links.

   This document defines the requirements for a Point-to-Multipoint PW
   (P2MP PW).  A P2MP PW is a mechanism that emulates the essential
   attributes of a P2MP telecommunications service such as a P2MP ATM
   VC over a Packet Switch Networks.
   The required functions of P2MP PWs include encapsulating
   service-specific Protocol data Units (PDU) arriving at an ingress
   Attachment Circuit (AC), and carrying them across a tunnel to one or
   more egress ACs, managing their timing and order, and any other
   operations required to emulate the behavior and characteristics of
   the service as faithfully as possible.


1.2. Scope of this document

   The document describes the general architecture of P2MP PW with
   reference model, mentions the notion of data encapsulation, and
   outlines specific requirements for the setup and maintenance of a
   P2MP PW.  In this document, the requirements focus on the Single-
   Segment PW model. It is for further study how it should be realized
   in Multi-Segment PW model.  For other aspects of P2MP PW
   implementation, such as packet processing (section 4) and
   Faithfulness of Emulated Services (section 7), the document refers to
   [RFC3916].


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1.3. Conventions used in this document

   Although this is a requirements specification not a protocol
   specification, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted to apply to
   protocol solutions designed to meet these requirements as described
   in [RFC2119] .

2. Definition
2.1. Acronyms

   P2P: Point-to-Point
   P2MP: Point-to-Multipoint
   PW: Pseudowire
   PSN: Packet Switched Network
   SS-PW: Single-Segment Pseudowire
   MS-PW: Multi-Segment Pseudowire

2.2. Terminology

   This document uses terminology described in [RFC5659].  It also
   introduces additional terms needed in the context of P2MP PW.

   P2MP PW, (also referred as PW Tree):
         Point-to-Multipoint Pseudowire.  A PW attached to a source
         Customer Edge (CE) used to distribute Layer1 or Layer2 traffic
         to a set of one or more receiver CEs.  The P2MP PW is
         unidirectional (i.e., carrying traffic from Root PE to Leaf
         PEs), and optionally supports a return path.
   P2MP SS-PW:
         Point-to-Multipoint Single-Segment Pseudowire.  A single
         segment P2MP PW set up between the Root PE attached to the
         source CE and the Leaf PEs attached to the receiver CEs.  The
         P2MP SS-PW uses P2MP Label Switched Paths (LSP) as PSN tunnels.
         The requirements in this document is targeted for SS-PW model.
         Application of MS-PW (Multi-segment PW) model [RFC5254] is out
         of scope and left for future work.
   Root PE:
         P2MP PW Root Provider Edge.  The PE attached to the traffic
         source CE for the P2MP PW via an Attachment Circuit (AC).
   Leaf PE:
         P2MP PW Leaf Provider Edge.  A PE attached to a set of one or
         more traffic receiver CEs, via ACs.  The Leaf PE replicates
         traffic to the CEs based on its Forwarder function [RFC3985].
   P2MP PSN Tunnel:
         In the P2MP SS-PW topology, The PSN Tunnel is a general term

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         indicating a virtual P2MP connection between the Root PE and
         the Leaf PEs.  A P2MP tunnel may potentially carry multiple
         P2MP PWs inside (aggregation).  This document uses terminology
         from the document describing the MPLS multicast architecture
         [RFC5332] for MPLS PSN.


3. P2MP PW Requirements

3.1. Reference Model

   As per the definition of [RFC3985], a pseudowire (PW) both originates
   and terminates on the edge of the same packet switched network (PSN).
   The PW label is unchanged between the originating and terminating
   Provider Edges (PEs).  This is also known as a single-segment
   pseudowire (SS-PW), as the most fundamental network model of PWE3.

   P2MP PW can be defined as Point-to-Multipoint connectivity from a
   Root PE connected to a traffic source CE to one or more Leaf PEs
   connected to traffic receiver CEs.  It is considered to be an
   extended architecture of the existing unicast-based SS-PW technology.

   Figure 1 describes the P2MP reference model which is derived from
   [RFC3985] to support P2MP emulated services.


























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                  |<-------------P2MP PW------------->|
          Native  |                                   |  Native
   ROOT   Service |    |<----P2MP PSN tunnel --->|    |  Service  LEAF
    V     (AC)    V    V                         V    V   (AC)      V
            |     +----+         +-----+         +----+     |
            |     |PE1 |         |  P  |=========|PE2 |AC2  |     +----+
            |     |    |         |   ......PW1.......>|---------->|CE2 |
            |     |    |         |   . |=========|    |     |     +----+
            |     |    |         |   . |         +----+     |
            |     |    |=========|   . |                    |
            |     |    |         |   . |         +----+     |
   +----+   | AC1 |    |         |   . |=========|PE3 |AC3  |     +----+
   |CE1 |-------->|........PW1.............PW1.......>|---------->|CE3 |
   +----+   |     |    |         |   . |=========|    |     |     +----+
            |     |    |         |   . |         +----+     |
            |     |    |=========|   . |                    |
            |     |    |         |   . |         +----+AC4  |     +----+
            |     |    |         |   . |=========|PE4 |---------->|CE4 |
            |     |    |         |   ......PW1.......>|     |     +----+
            |     |    |         |     |=========|    |AC5  |     +----+
            |     |    |         |     |         |    |---------->|CE5 |
            |     +----+         +-----+         +----+     |     +----+
                    Figure 1 P2MP PW Reference Model


   This architecture applies to the case where a P2MP PSN tunnel extends
   between edge nodes of a single PSN domain to transport a
   unidirectional P2MP PW with endpoints at these edge nodes. In this
   model a single copy of each PW packet is sent over the PW on the P2MP
   PSN tunnel and is received by all Leaf PEs due to the P2MP nature of
   the PSN tunnel.  The P2MP PW SHOULD be traffic optimized, i.e., only
   one copy of a P2MP PW packet or PSN tunnel (underlying layer) is sent
   on any single link along the P2MP path. P routers participate in P2MP
   PSN tunnel operation but not in the signaling of P2MP PWs.

   The Reference Model outlines the basic pieces of a P2MP PW.  However,
   several levels of replication needs to be considered when designing a
   P2MP PW solution:

   -  Ingress PE replication to CEs: traffic is replicated to a set of
      local receiver CEs
   -  P router replication in the core: traffic replicated by means of
      P2MP PSN tunnel (P2MP LSP)
   -  Egress PE replication to CEs: traffic replicated to local receiver
      CEs



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   Theoretically, it is also possible to consider Ingress PE replication
   in the core; that is, all traffic is replicated to a set of P2P PSN
   transport tunnels at ingress, not using P router replication at all.

   However, this approach may easily lead to more than one-stream
   bandwidth consumption at a single link, particularly if the PSN
   tunnels logically go over the same physical link.  Hence this
   approach is not preferred.

   Specific operations that MUST be performed at the PE on the native
   data units are not described here since the required pre-processing
   (Forwarder (FWRD) and Native Service Processing (NSP)) defined in
   section 4.2 of [RFC3985] are also applicable to P2MP PW.

   P2MP PWs are generally unidirectional, but a Root PE may need to
   receive unidirectional P2P return traffic from any Leaf PE.  For that
   purpose the P2MP PW solution MAY support an optional return path from
   each Leaf PE to Root PE.

3.2. P2MP PW and Underlying Layer

   The definition of MPLS multicast encapsulation [RFC5332] specifies
   the procedure to carry MPLS packets that are to be replicated and a
   copy of the packet sent to each of the specified next hops.  This
   notion is also applicable to P2MP PW (as a MPLS) packet carried by a
   P2MP PSN tunnel.

   To be more precise, a P2MP PSN tunnel corresponds to a "point-to-
   multipoint data link or tunnel" described in [RFC5332] Section 3.
   Similarly, P2MP PW labels correspond to "the top labels (before
   applying the data link or tunnel encapsulation) of all MPLS packets
   that are transmitted on a particular point-to-multipoint data link or
   tunnel."

   In P2MP PW architecture, PW label with PW-PDU [RFC3985] is replicated
   by underlying P2MP PSN tunnel layer in SS-PW network model. In other
   words, it is intended to utilize PSN technology designed for
   efficient multicast/broadcast transport. Note that PW label is
   unchanged and hidden in switching by transit P routers as long as the
   model of SS-PW is taken.

   In a solution, a P2MP PW MUST be supported over a single P2MP PSN
   tunnel as underlying layer of traffic distribution. Figure 2 gives
   an example of P2MP PW topology relying on a single P2MP LSP. The
   PW tree is composed of one Root PE (i1) and several Leaf PEs (e1, e2,
   e3, e4).
   The mechanisms for establishing the PSN tunnel are outside the scope
   of this document, as long as they enable the essential attributes of
   the service to be emulated.

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               i1
               /
              / \
             /   \
            /     \
           /\      \
          /  \      \
         /    \      \
        /      \    / \
       e1      e2  e3 e4

   Figure 2 Example of P2MP Underlying Layer for P2MP PW

   A single P2MP PSN tunnel MUST be able to serve more than one P2MP PW
   traffic in an aggregated way, i.e., multiplexing.

   A P2MP PW solution MAY support different P2MP PSN tunneling
   technology (e.g., MPLS over GRE [RFC4023], or P2MP MPLS LSP) or
   different setup protocols. (e.g., MLDP [RFC6388], and P2MP RSVP-TE
   [RFC4875]).

   The P2MP LSP associated to the P2MP PW can be selected either by user
   configuration or by dynamically using a multiplexing/demultiplexing
   mechanism.

   The P2MP PW multiplexing SHOULD be used based on the overlap rate
   between P2MP LSP and P2MP PW. As an example, an existing P2MP LSP
   may attach more leaves than the ones defined as Leaf PEs for a given
   P2MP PW.  It may be attractive to reuse it to minimize new
   configuration, but using this P2MP LSP would imply non-
   Leaf PEs (i.e. not part of the P2MP PW) to receive unwanted traffic.

   Note: no special configuration is needed for non-Leaf PEs to drop
   those unwanted traffic because they do not have forwarding
   information entry unless they process corresponding P2MP PWs set-up
   operation (e.g. signaling).

   The operator SHOULD determine whether the P2MP PW can accept
   partially multiplexing with P2MP LSP, and a minimum congruency rate
   may be defined.  The Root PE can determine whether P2MP PW can
   multiplex to a P2MP LSP according to the congruency rate.  The
   congruency rate SHOULD take into account several items, such as:

   -  the amount of overlap between the number of Leaf PEs of P2MP PW
      and existing egress PE routers of a P2MP LSP.  If there is a
      complete overlap, the congruency is perfect and the rate is 100%.
   -  at the expense of the additional traffic (e.g. other VPNs)
      supported over the P2MP LSP.

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   With this procedure a P2MP PW is nested within a P2MP LSP.  This
   allows multiplexing several PWs over a common P2MP LSP.  Prior to the
   P2MP PW signaling phase, the Root PE determines which P2MP LSP will
   be used for this P2MP PW.  The PSN Tunnel can be an existing PSN
   tunnel or the Root PE can create a new P2MP PSN tunnel. In addition,
   if ideal congruency rate is desired, if the P2MP PW has one or more
   extra leaf nodes that are not covered by the existing P2MP LSP, the
   P2MP LSP SHOULD be modified or re-created to cover them.


3.3. P2MP PW Construction

   [RFC5332] introduces two approaches to assign MPLS label (meaning PW
   label in P2MP PW context): Upstream-Assigned[RFC5331] and
   Downstream-Assigned.  However, it is out of scope of this document
   which one should be used in PW construction.  It is left to the
   specification of the solution work.

   The following requirements apply to the establishment of P2MP PWs:


   -  PE nodes MUST be configurable with the P2MP PW identifiers and
      ACs.
   -  A discovery mechanism SHOULD allow the Root PE to discover the
      Leaf PEs, or vice versa.
   -  Solutions SHOULD allow single-sided operation at the Root PE for
      the selection of some AC(s) at the Leaf PE(s) to be attached to
      the PW tree so that the Root PE controls the Leaf attachment.

   The Root PE SHOULD support a method to be informed about whether a
   Leaf PE has successfully attached to the PW tree.

3.4. P2MP PW Signaling Requirements

3.4.1. P2MP PW Identifier

   The P2MP PW MUST be uniquely identified. This unique P2MP PW
   identifier MUST be used for all signaling procedures related to this
   PW (PW setup, Monitoring, etc).

3.4.2. PW type mismatch

   The Root PE and Leaf PEs of a P2MP PW MUST be configured with the
   same PW type as defined in [RFC4446] for P2P PW. In case of a
   different type, a PE SHOULD abort attempts to attach the Leaf PE to
   the P2MP PW.

3.4.3. Interface Parameters sub-TLV


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   Some interface parameters [RFC4446] related to the AC capability have
   been defined according to the PW type and are signaled during the PW
   setup.

   Where applicable, a solution is REQUIRED to ascertain whether the AC
   at the Leaf PE is capable of supporting traffic coming from the AC at
   the Root PE.


   In case of a mismatch, the passive PE (Root or Leaf PE, depending on
   the signaling process) SHOULD support mechanisms to reject attempts
   to attach the Leaf PE to the P2MP PW.

3.4.4. Leaf Grafting/Pruning

   Once the PW tree is established, the solution MUST allow the addition
   or removal of a Leaf PE, or a subset of leaves to/from the existing
   tree, without any impact on the PW tree (data and control planes) for
   the remaining Leaf PEs.

   The addition or removal of a Leaf PE MUST also allow the P2MP PSN
   tunnel to be updated accordingly. This may cause the P2MP PSN tunnel
   to add or remove the corresponding Leaf PE.


3.4.5. Failure Detection and Reporting

   Since the underlying layer has an End-to-End P2MP topology between
   the Root PE and the Leaf PEs, the failure reporting and processing
   procedures are implemented only on the edge nodes.

   Failure events may cause one or more Leaf PEs to become detached from
   the PW tree. These events MUST be reported to the Root PE, using
   appropriate out-of-band or inband Operations, Administration, and
   Maintenance (OAM) messages for monitoring.
   It MUST be possible for the operator to choose the out-of-band or
   inband Monitoring tools or both to monitor the Leaf PE status.
   The solution SHOULD allow the Root PE to be informed of Leaf PEs
   failure for management purposes.

   Based on these failure notifications, solutions MUST allow the Root
   PE to update the remaining leaves of the PW tree.

   -  A solution MUST support in-band status notification mechanism
      to detect failures:
      unidirectional point-to-multipoint traffic failure.  This SHOULD
      be realized by enhancing existing unicast PW methods, such as VCCV


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      for seamless and familiar operation defined in [RFC5085].
   -  In case of failure, it SHOULD correctly report which Leaf PEs are
      affected.  This SHOULD be realized by enhancing existing PW
      methods, such as LDP Status Notification.  The notification
      message SHOULD include the type of fault (P2MP PW, AC or PSN
      tunnel).
   -  A Leaf PE MAY be notified of the status of the Root PE's AC.
   -  A solution MUST support OAM message mapping [RFC6310] at the
      Root PE and Leaf PE if a failure is detected on the source CE.


3.4.6. Protection and Restoration

   It is assumed that if recovery procedures are required, the P2MP PSN
   tunnel will support standard MPLS-based recovery techniques
   (typically based on RSVP-TE).  In that case a mechanism SHOULD be
   implemented to avoid race conditions between recovery at the PSN
   level and recovery at the PW level.

   An alternative protection scheme MAY rely on the PW layer.

   Leaf PEs MAY be protected via a P2MP PW redundancy mechanism.  In the
   example depicted below, a standby P2MP PW is used to protect the
   active P2MP PW.  In that protection scheme the AC at the Root PE MUST
   serve both P2MP PWs.  In this scenario, the condition when to do the
   switchover SHOULD be implemented, e.g. one or all Leaf failure of
   active P2MP PW will trigger the whole P2MP PW's switchover.


                                     CE1
                                      |
         ROOT           active       PE1    standby
                        P2MP PW  .../  \....P2MP PW
                                /           \
                              P2            P3
                             / \           / \
                            /   \         /   \
                           /     \       /     \
         LEAF            PE4    PE5    PE6    PE7
                          |      |      |      |
                          |       \    /       |
                           \        CE2       /
                            \                /
                              ------CE3-----

       Figure 3: Example of P2MP PW redundancy for protecting Leaf PEs



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   Note that some of the nodes/links in this figure can be physically
   shared, which depends on the service provider policy of network
   redundancy.

   The Root PE MAY be protected via a P2MP PW redundancy mechanism.  In
   the example depicted below, a standby P2MP PW is used to protect the
   active P2MP.  A single AC at the Leaf PE MUST be used to attach the
   CE to the primary and the standby P2MP PW.  The Leaf PE MUST support
   protection mechanisms in order to select the active P2MP PW.

                                     CE1
                                    /  \
                                   |    |
               ROOT     active    PE1  PE2   standby
                        P2MP PW1   |    |    P2MP PW2
                                   |    |
                                   P2  P3
                                  /  \/  \
                                 /   /\   \
                                /   /  \   \
                               /   /    \   \
               LEAF            PE4        PE5
                                |          |
                               CE2        CE3
      Figure 4: Example of P2MP PW redundancy for protecting Root PEs

3.4.7. Scalability

   The solution SHOULD scale at worst linearly with the number of Leaf
   PEs.

   Increasing the number of P2MP PWs between a Root PE and a given set
   of Leaf PEs SHOULD NOT cause the P router to increase the number of
   entries in its forwarding table by the same or greater proportion.
   Multiplexing P2MP PWs to P2MP PSN Tunnels achieves this.

4. Backward Compatibility

   Solutions MUST be backward compatible with current PW standards.
   Solutions SHOULD utilize existing capability advertisement and
   negotiation procedures for the PEs implementing P2MP PW endpoints.

   The implementation of OAM mechanisms also implies the advertisement
   of PE capabilities to support specific OAM features.
   The solution MAY allow advertising P2MP PW OAM capabiltities.
   A solution MUST NOT allow a P2MP PW to be established
   to PEs that do not support P2MP PW functionality.  It MUST have a
   mechanism to report an error for incompatible PEs.

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   In some cases, upstream traffic is needed from downstream CEs to
   upstream CEs.  The P2MP PW solution SHOULD allow a return path (i.e.
   from the Leaf to the Root) that provides upstream connectivity.

   In particular, the same ACs MAY be shared between downstream and
   upstream directions.  For downstream, a CE receives traffic
   originated by the Root PE over its AC.  For upstream, the CE MAY also
   send traffic destined to the same Root PE over the same AC.


5. Security Considerations

   The security requirements common to PW are raised in Section 10 of
   [RFC3916].  P2MP PW is a variant of the initial P2P PW definition,
   and those requirements also apply to P2MP PW.

6.IANA Considerations

   This document does not require any IANA action.


7. Contributing Aurhors

   Philippe Niger
   France Telecom
   2, avenue Pierre-Marzin
   22307 Lannion Cedex
   France

   Email: philippe.niger@orange-ftgroup.com

   Luca Martini
   Cisco Systems, Inc.
   9155 East Nichols Avenue, Suite 400
   Englewood, CO, 80112

   EMail: lmartini@cisco.com

   Lei Wang
   Telenor
   Snaroyveien 30
   Fornebu 1331
   Norway

   Email: lei.wang@telenor.com


   Rahul Aggarwal
   Juniper Networks

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   1194 North Mathilda Ave.
   Sunnyvale, CA 94089

   Email: rahul@juniper.net

   Simon Delord
   Telstra
   380 Flinders lane.  Melbourne

   Email: simon.delord@gmail.com

   Martin Vigoureux
   Alcatel-Lucent France
   Route de Villejust
   91620 Nozay
   France

   Email: martin.vigoureux@alcatel-lucent.fr

   Lizhong Jin
   ZTE Corporation
   889, Bibo Road
   Shanghai, 201203, China

   Email: lizho.jin@gmail.com



8. Acknowledgments

   The authors thank the authors of [RFC4461] since the structure and
   content of this document were, for some sections, largely inspired by
   [RFC4461].  Many thanks to JL Le Roux and A. Cauvin for the
   discussions, comments and support.

9. References

9.1. Normative References

[RFC2119]       Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC2119, March 1997.

9.2. Informative References

   [I-D.ietf-l2vpn-vpms-frmwk-requirements]
              Kamite, Y., Jounay, F., Niven-Jenkins, B., Brungard, D.,
              and L. Jin, "Framework and Requirements for Virtual
              Private Multicast Service (VPMS)", draft-ietf-l2vpn-vpms-
              frmwk-requirements-05 (work in progress), October 2012.


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   [RFC3916]  Xiao, X., McPherson, D., and P. Pate, "Requirements for
              Pseudo-Wire Emulation Edge-to-Edge (PWE3)", RFC 3916,
              September 2004.

   [RFC3985]  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
              Edge (PWE3) Architecture", RFC 3985, March 2005.

   [RFC4023]  Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating
              MPLS in IP or Generic Routing Encapsulation (GRE)", RFC
              4023, March 2005.

   [RFC4446]  Martini, L., "IANA Allocations for Pseudowire Edge to Edge
              Emulation (PWE3)", BCP 116, RFC 4446, April 2006.

   [RFC4461]  Yasukawa, S., "Signaling Requirements for Point-to-
              Multipoint Traffic-Engineered MPLS Label Switched Paths
              (LSPs)", RFC 4461, April 2006.

   [RFC4875]  Aggarwal, R., Papadimitriou, D., and S. Yasukawa,
              "Extensions to Resource Reservation Protocol - Traffic
              Engineering (RSVP-TE) for Point-to-Multipoint TE Label
              Switched Paths (LSPs)", RFC 4875, May 2007.

   [RFC5085]  Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
              Connectivity Verification (VCCV): A Control Channel for
              Pseudowires", RFC 5085, December 2007.

   [RFC5254]  Bitar, N., Bocci, M., and L. Martini, "Requirements for
              Multi-Segment Pseudowire Emulation Edge-to-Edge (PWE3)",
              RFC 5254, October 2008.

   [RFC5331]  Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
              Label Assignment and Context-Specific Label Space", RFC
              5331, August 2008.

   [RFC5332]  Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS
              Multicast Encapsulations", RFC 5332, August 2008.

   [RFC5659]  Bocci, M. and S. Bryant, "An Architecture for Multi-
              Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
              October 2009.






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   [RFC6310]  Aissaoui, M., Busschbach, P., Martini, L., Morrow, M.,
              Nadeau, T., and Y(J). Stein, "Pseudowire (PW) Operations,
              Administration, and Maintenance (OAM) Message Mapping",
              RFC 6310, July 2011.

   [RFC6388]  Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
              "Label Distribution Protocol Extensions for Point-to-
              Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6388, November 2011.


Authors' Addresses

   Frederic Jounay (editor)
   Orange CH
   4 rue caudray 1020 Renens
   Switzerland

   Email: frederic.jounay@orange.ch


   Yuji Kamite (editor)
   NTT Communications Corporation
   Granpark Tower
   3-4-1 Shibaura, Minato-ku
   Tokyo  108-8118
   Japan

   Email: y.kamite@ntt.com


   Giles Heron
   Cisco Systems, Inc.
   9 New Square
   Bedfont Lakes
   Feltham
   Middlesex
   TW14 8HA
   United Kingdom

   Email: giheron@cisco.com




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   Matthew Bocci
   Alcatel-Lucent Telecom Ltd
   Voyager Place
   Shoppenhangers Road
   Maidenhead
   Berks
   United Kingdom

   Email: matthew.bocci@alcatel-lucent.co.uk



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