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RFC 7338

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

 


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Internet Engineering Task Force (IETF)                    F. Jounay, Ed.
Request for Comments: 7338                                     Orange CH
Category: Informational                                   Y. Kamite, Ed.
ISSN: 2070-1721                                       NTT Communications
                                                                G. Heron
                                                           Cisco Systems
                                                                M. Bocci
                                                          Alcatel-Lucent
                                                          September 2014


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

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).

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7338.

Page 2 
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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

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Table of Contents

   1. Introduction ....................................................3
      1.1. Problem Statement ..........................................3
      1.2. Scope of This Document .....................................4
      1.3. Conventions Used in This Document ..........................4
   2. Definitions .....................................................5
      2.1. Acronyms ...................................................5
      2.2. Terminology ................................................5
   3. P2MP PW Requirements ............................................6
      3.1. Reference Model ............................................6
      3.2. P2MP PW and Underlying Layer ...............................7
      3.3. P2MP PW Construction .......................................9
      3.4. P2MP PW Signaling Requirements ............................10
           3.4.1. P2MP PW Identifier .................................10
           3.4.2. PW Type Mismatch ...................................10
           3.4.3. Interface Parameters Sub-TLV .......................10
           3.4.4. Leaf Grafting/Pruning ..............................10
           3.4.5. Failure Detection and Reporting ....................11
           3.4.6. Protection and Restoration .........................11
           3.4.7. Scalability ........................................13
   4. Backward Compatibility .........................................13
   5. Security Considerations ........................................13
   6. References .....................................................14
      6.1. Normative References ......................................14
      6.2. Informative References ....................................14
   7. Acknowledgments ................................................15
   8. Contributors ...................................................16

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 (PSN).  It provides a
   single service that 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, Time-Division
   Multiplexing (TDM), ATM, and Frame Relay) 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 [VPMS-REQS] and
   required to provide P2MP Layer 2 VPN service can be achieved using
   one or more P2MP PWs.  The use of PW encapsulation enables P2MP

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   services to transport Layer 1 or Layer 2 data.  This could be
   achieved using a set of point-to-point PWs, with traffic replication
   at the Root 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
   Virtual Circuit over a Packet Switched Network.

   The required functions of P2MP PWs include encapsulating service-
   specific Protocol Data Units (PDUs) arriving at an ingress Attachment
   Circuit (AC), 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 a
   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.  The requirements for realizing P2MP PW in the
   Multi-Segment PW model [RFC5254] are left for further study.  This
   document refers to [RFC3916] for other aspects of P2MP PW
   implementation, such as "Packet Processing" (Section 4 of that
   document) and "Faithfulness of Emulated Services" (Section 7 of that
   document).

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].

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2.  Definitions

2.1.  Acronyms

   P2P:   Point-to-Point
   P2MP:  Point-to-Multipoint
   PW:    Pseudowire
   PSN:   Packet Switched Network
   SS-PW: Single-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 to as PW tree):
      Point-to-Multipoint Pseudowire.  A PW attached to a source
      Customer Edge (CE) used to distribute Layer 1 or Layer 2 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 (LSPs) as PSN tunnels.

   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
      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.

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3.  P2MP PW Requirements

3.1.  Reference Model

   As per the definition in [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) -- the most fundamental network model of PWE3.

   A 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 P2P SS-PW technology.

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

                  |<-------------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

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   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) packet 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 need 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 is replicated by means
      of a P2MP PSN tunnel (P2MP LSP)

   -  Egress PE replication to CEs: traffic is replicated to local
      receiver CEs

   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 lead to duplicate copies of each PW packet
   being sent over the same physical link, specifically in the case
   where multiple PSN tunnels transit that 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] is 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 the 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 a P2MP PW 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 Section 3 of [RFC5332].

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   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 the P2MP PW architecture using the SS-PW network model, the PW-PDU
   [RFC3985] is replicated by the underlying P2MP PSN tunnel layer.
   Note that the PW label is unchanged, and hidden in switching, by the
   transit P routers.

   In a solution, a P2MP PW MUST be supported over a single P2MP PSN
   tunnel as the 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.

                                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 the traffic from more
   than one P2MP PW 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., multipoint extensions for LDP (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

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   P2MP PW.  It may be attractive to reuse it to minimize new
   configuration, but using this P2MP LSP would cause 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
   that unwanted traffic because they do not have forwarding information
   entries unless they process the setup operation for corresponding
   P2MP PWs (e.g., signaling).

   The operator SHOULD determine whether it is acceptable to partially
   multiplex the P2MP PW onto a P2MP LSP, and a minimum congruency rate
   may be defined to enable the Root PE to make this determination.  The
   congruency rate SHOULD take into account several items, including:

   -  the amount of overlap between the Leaf PEs of the P2MP PW and the
      existing egress PE routers of the P2MP LSP.  If there is a
      complete overlap, the congruency is perfect and the rate is 100%.

   -  the impact on other traffic (e.g., from other VPNs) supported over
      the P2MP LSP.

   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.  Note that
   the ingress PE may modify or re-create an existing P2MP PSN tunnel in
   order to add one or more leaf PEs to enable it to transport the P2MP
   PW.

3.3.  P2MP PW Construction

   [RFC5332] introduces two approaches to assigning MPLS labels (meaning
   PW labels in the 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.

   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.

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   -  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 type
   mismatch, a PE SHOULD abort attempts to attach the Leaf PE to the
   P2MP PW.

3.4.3.  Interface Parameters Sub-TLV

   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.

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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 in-band Operations, Administration, and
   Maintenance (OAM) messages for monitoring.

   It MUST be possible for the operator to choose the out-of-band or in-
   band monitoring tools or both to monitor the Leaf PE status.  For
   management purposes, the solution SHOULD allow the Root PE to be
   informed of Leaf PEs' failure.

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

   -  A solution MUST support an in-band status notification mechanism
      to detect failures: unidirectional point-to-multipoint traffic
      failure.  This MUST be realized by enhancing existing unicast PW
      methods, such as Virtual Circuit Connectivity Verification (VCCV)
      for seamless and familiar operation as defined in [RFC5085].

   -  In case of failure, it MUST correctly report which Leaf PEs are
      affected.  This MUST 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.  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 criteria for

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   switching over SHOULD be defined, e.g., failure of one or all leaves
   of the active P2MP PW will trigger switchover of the whole P2MP PW.

                                     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

   Note that some of the nodes/links in this figure can be physically
   shared; this 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

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3.4.7.  Scalability

   The solution SHOULD scale at worst linearly for message size, memory
   requirements, and processing requirements, 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 capabilities.  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.

   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 PE to the Root PE) that provides upstream connectivity.

   In particular, the same ACs MAY be shared between the 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 11 of
   [RFC3916].  P2MP PW is a variant of the initial P2P PW definition,
   and those requirements (and the security considerations from
   [RFC3985]) also apply.  The security considerations from [RFC5920]
   and [RFC6941] also apply to the IP/MPLS and MPLS-TP deployment
   scenarios, respectively.

   Some issues specifically due to P2MP topology need to be addressed in
   the definition of the solution:

   -  The solution SHOULD provide means to protect the traffic delivered
      to receivers (Integrity, Confidentiality, Endpoint
      Authentication).

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   -  The solution SHOULD support means to protect the P2MP PW as a
      whole against attacks that would lead to any kind of denial of
      service.

   Specifically, safeguard mechanisms should be considered to avoid any
   negative impact on the whole PW tree when any one receiver or any
   group of receivers is attacked.  Safeguard mechanisms for both the
   data plane and the control plane need to be considered.

6.  References

6.1.  Normative References

   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate
               Requirement Levels", BCP 14, RFC 2119, March 1997.

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

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

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

   [RFC5332]   Eckert, T., Rosen, E., Ed., 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.

   [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.

6.2.  Informative References

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

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

Top      ToC       Page 15 
   [RFC4875]   Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
               Yasukawa, Ed., "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., Ed., and C. Pignataro, Ed., "Pseudowire
               Virtual Circuit Connectivity Verification (VCCV): A
               Control Channel for Pseudowires", RFC 5085, December
               2007.

   [RFC5254]   Bitar, N., Ed., Bocci, M., Ed., and L. Martini, Ed.,
               "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.

   [RFC5920]   Fang, L., Ed., "Security Framework for MPLS and GMPLS
               Networks", RFC 5920, July 2010.

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

   [RFC6941]   Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S.,
               Ed., and R. Graveman, Ed., "MPLS Transport Profile
               (MPLS-TP) Security Framework", RFC 6941, April 2013.

   [VPMS-REQS] Kamite, Y., Jounay, F., Niven-Jenkins, B., Brungard, D.,
               and L. Jin, "Framework and Requirements for Virtual
               Private Multicast Service (VPMS)", Work in Progress,
               October 2012.

7.  Acknowledgments

   The authors thank the following people: the authors of [RFC4461]
   since the structure and content of this document were, for some
   sections, largely inspired by [RFC4461]; JL. Le Roux and A. Cauvin
   for the discussions, comments, and support; Adrian Farrel for his
   Routing Area Director review; and IESG reviewers.

Top      ToC       Page 16 
8.  Contributors

   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
   US

   EMail: lmartini@cisco.com


   Lei Wang
   Telenor
   Snaroyveien 30
   Fornebu 1331
   Norway

   EMail: lei.wang@telenor.com


   Rahul Aggarwal
   Juniper Networks
   1194 North Mathilda Ave.
   Sunnyvale, CA  94089
   US

   EMail: rahul@juniper.net


   Simon Delord
   Telstra
   380 Flinders Lane
   Melbourne
   Australia

   EMail: simon.delord@gmail.com

Top      ToC       Page 17 
   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

Top      ToC       Page 18 
Authors' Addresses

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

   EMail: frederic.jounay@orange.ch


   Yuji Kamite (editor)
   NTT Communications Corporation
   1-1-6 Uchisaiwai-cho, Chiyoda-ku
   Tokyo 100-8019
   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


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

   EMail: Matthew.Bocci@alcatel-lucent.com