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Versions: 00 01 02 03 04 05 06 07 RFC 5885

PWE3                                                      T. Nadeau, Ed.
Internet-Draft                                                        BT
Intended status: Standards Track                       C. Pignataro, Ed.
Expires: January 28, 2010                            Cisco Systems, Inc.
                                                           July 27, 2009


              Bidirectional Forwarding Detection (BFD) for
    the Pseudowire Virtual Circuit Connectivity Verification (VCCV)
                      draft-ietf-pwe3-vccv-bfd-07

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   This document describes Connectivity Verification (CV) types using
   Bidirectional Forwarding Detection (BFD) with Virtual Circuit
   Connectivity Verification (VCCV).  VCCV provides a control channel
   that is associated with a Pseudowire (PW), as well as the
   corresponding operations and management functions such as
   connectivity verification to be used over that control channel.


Table of Contents

   1.  Specification of Requirements  . . . . . . . . . . . . . . . .  3

   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3

   3.  Bidirectional Forwarding Detection Connectivity
       Verification . . . . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  BFD CV Type Operation  . . . . . . . . . . . . . . . . . .  4
     3.2.  BFD Encapsulation  . . . . . . . . . . . . . . . . . . . .  5
     3.3.  CV Types for BFD . . . . . . . . . . . . . . . . . . . . .  7

   4.  Capability Selection . . . . . . . . . . . . . . . . . . . . .  9

   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     5.1.  MPLS CV Types for the VCCV Interface Parameters Sub-TLV  .  9
     5.2.  PW Associated Channel Type . . . . . . . . . . . . . . . . 10
     5.3.  L2TPv3 CV Types for the VCCV Capability AVP  . . . . . . . 10

   6.  Congestion Considerations  . . . . . . . . . . . . . . . . . . 11

   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12

   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12

   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 13

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13





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1.  Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   The reader is expected to be familiar with the terminology and
   abbreviations defined in [RFC5085].


2.  Introduction

   This document describes Connectivity Verification (CV) types using
   Bidirectional Forwarding Detection (BFD) with Virtual Circuit
   Connectivity Verification (VCCV).  VCCV [RFC5085] provides a control
   channel that is associated with a Pseudowire (PW), as well as the
   corresponding operations and management functions such as
   connectivity/fault verification to be used over that control channel.

   BFD [I-D.ietf-bfd-base] is used over the VCCV control channel
   primarily as a pseudowire fault detection mechanism, for detecting
   dataplane failures.  Some BFD CV Types can additionally carry fault
   status between the endpoints of the pseudowire.  Furthermore, this
   information can then be translated into the native OAM status codes
   used by the native access technologies, such as ATM, Frame-Relay or
   Ethernet.  The specific details of such status interworking are out
   of the scope of this document, and are only noted here to illustrate
   the utility of BFD over VCCV for such purposes.  Those details can be
   found in [I-D.ietf-pwe3-oam-msg-map].

   The new BFD CV Types are PW Demultiplexer-agnostic, and hence
   applicable for both MPLS and L2TPv3 Pseudowire Demultiplexers.  This
   document concerns itself with the BFD VCCV operation over Single-
   Segment Pseudowires (SS-PW).  This specification describes procedures
   only for BFD asynchronous mode.


3.  Bidirectional Forwarding Detection Connectivity Verification

   VCCV can support several Connectivity Verification (CV) types.  This
   section defines new CV Types for use when BFD is used as the VCCV
   payload.

   Four CV Types are defined for BFD.  Table 1 summarizes the BFD CV
   Types, grouping them by encapsulation (i.e., with vs. without IP/UDP
   headers) and by functionality (i.e., fault detection only vs. fault
   detection and status signaling).




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   +----------------------------+--------------+-----------------------+
   |                            |     Fault    |  Fault Detection and  |
   |                            |   Detection  |    Status Signaling   |
   |                            |     Only     |                       |
   +----------------------------+--------------+-----------------------+
   |  BFD, IP/UDP encapsulation |     0x04     |          0x08         |
   |      (with IP/UDP Headers) |              |                       |
   |                            |              |                       |
   |  BFD, PW-ACH encapsulation |     0x10     |          0x20         |
   |   (without IP/UDP Headers) |              |                       |
   +----------------------------+--------------+-----------------------+

                 Table 1: Bitmask Values for BFD CV Types

3.1.  BFD CV Type Operation

   When heart-beat indication is necessary for one or more PWs, the
   Bidirectional Forwarding Detection (BFD) [I-D.ietf-bfd-base] provides
   a means of continuous monitoring of the PW data path and, in some
   operational modes, propagation of PW receive and transmit defect
   state indications.

   In order to use BFD, both ends of the PW connection need to agree on
   the BFD CV Type to use:

      For statically provisioned pseudowires, both ends need to be
      statically configured to use the same BFD CV Type (in addition to
      be statically configured for VCCV with the same CC Type).

      For dynamically established pseudowires, both ends of the PW must
      have signaled the existence of a control channel and the ability
      to run BFD on it (see Section 3.3 and Section 4).

   Once a node has selected a valid BFD CV Type to use (either
   statically provisioned or selected dynamically after the node has
   both signaled and received signaling from its peer of these
   capabilities), it begins sending BFD control packets:

   o  The BFD control packets are sent on the VCCV control channel.  The
      use of the VCCV control channel provides the context required to
      bind and bootstrap the BFD session, since discriminator values are
      not exchanged; the pseudowire demultiplexer field (e.g., MPLS PW
      Label or L2TPv3 Session ID) provides the context to demultiplex
      the first BFD control packet, and thus single-hop BFD
      initialization procedures are followed (see Section 3 of
      [I-D.ietf-bfd-v4v6-1hop] and Section 6 of [I-D.ietf-bfd-generic]).





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   o  A single BFD session exists per-pseudowire.  Both PW endpoints
      take the Active role sending initial BFD Control packets with a
      "Your Discriminator" field of zero, and BFD Control packets
      received with a "Your Discriminator" field of zero are associated
      to the BFD session bound to the PW.

   o  BFD MUST be run in asynchronous mode (see [I-D.ietf-bfd-base]).

   The operation of BFD VCCV for PWs is therefore symmetrical.  Both
   endpoints of the bidirectional pseudowire MUST send BFD messages on
   the VCCV control channel.

   The details of the BFD state machine are as per Section 6.2 of
   [I-D.ietf-bfd-base].  The following scenario exemplifies the
   operation: When the downstream PE (D-PE) does not receive BFD control
   messages from its upstream peer PE (U-PE) during a certain number of
   transmission intervals (a number provisioned by the operator as
   "Detect Mult" or detection time multiplier [I-D.ietf-bfd-base]), D-PE
   declares that the PW in its receive direction is down.  In other
   words, D-PE enters the "PW receive defect" state for this PW.  After
   this calculated Detection Time (see Section 6.8.4 of
   [I-D.ietf-bfd-base]), D-PE declares the session Down, and signals
   this to the remote end via the State (Sta) with Diagnostic code 1
   (Control Detection Time Expired).  In turn, U-PE declares the PW is
   down in its transmit direction, setting the State to Down with
   Diagnostic code 3 (Neighbor signaled session down) in its control
   messages to D-PE.  U-PE enters the "PW transmit defect" state for
   this PW.  How it further processes this error condition, and
   potentially conveys this status to the attachment circuits is out of
   the scope of this specification, and is defined in
   [I-D.ietf-pwe3-oam-msg-map].

3.2.  BFD Encapsulation

   The VCCV message comprises a BFD Control packet [I-D.ietf-bfd-base]
   encapsulated as specified by the CV Type.  There are two ways in
   which a BFD connectivity verification packet may be encapsulated over
   the VCCV control channel.  This document defines four BFD CV Types
   (see Section 3), which can be grouped into two pairs of BFD CV Types
   from an encapsulation point of view.  See Table 1 in Section 3 that
   summarizes the BFD CV Types.

   o  IP/UDP BFD Encapsulation (BFD with IP/UDP Headers)

      In the first method, the VCCV encapsulation of BFD includes the
      IP/UDP headers as defined in Section 4 of
      [I-D.ietf-bfd-v4v6-1hop].  BFD Control packets are therefore
      transmitted in UDP with destination port 3784 and source port



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      within the range 49152 through 65535.  The IP Protocol Number and
      UDP Port numbers discriminate among the possible VCCV payloads
      (i.e., differentiate among ICMP Ping and LSP Ping defined in
      [RFC5085] and BFD).

      The IP version (IPv4 or IPv6) MUST match the IP version used for
      signaling for dynamically established pseudowires, or MUST be
      configured for statically provisioned pseudowires.  The source IP
      address is an address of the sender.  The destination IP address
      is a (randomly chosen) IPv4 address from the range 127/8 or IPv6
      address from the range 0:0:0:0:0:FFFF:127.0.0.0/104.  The
      rationale is explained in Section 2.1 of [RFC4379].  The Time to
      Live/Hop Limit and Generalized TTL Security Mechanism (GTSM)
      procedures from Section 5 of [I-D.ietf-bfd-v4v6-1hop] apply to
      this encapsulation, and hence the TTL/Hop Limit is set to 255.

      If the PW is establised by signaling, then the BFD CV Type used
      for this encapsulation is either 0x04 or 0x08.

   o  PW-ACH BFD Encapsulation (BFD without IP/UDP Headers)

      In the second method, a BFD Control packet (format defined in
      Section 4 of [I-D.ietf-bfd-base]) is encapsulated directly in the
      VCCV control channel (see Sections 6 and 8 of
      [I-D.ietf-bfd-generic]) and the IP/UDP headers are omitted from
      the BFD encapsulation.  Therefore, to utilize this encapsulation,
      a pseudowire MUST use the PW Associated Channel Header (PW-ACH)
      Control Word format (see [RFC5586]) for its Control Word (CW) or
      L2-Specific Sublayer (L2SS, used in L2TPv3).

      In this encapsulation, a "raw" BFD Control packet (i.e., a BFD
      Control packet as defined in Section 4.1 of [I-D.ietf-bfd-base]
      without IP/UDP Headers) follows directly the PW-ACH.  The PW-ACH
      Channel Type indicates that the Associated Channel carries "raw"
      BFD.  The PW Associated Channel (PWAC) is defined in Section 5 of
      [RFC4385], and its Channel Type field is used to discriminate the
      VCCV payload types.

      The usage of the PW-ACH on different VCCV CC Types is specified
      for CC Type 1, Type 2 and Type 3 respectively in Sections 5.1.1,
      5.1.2 and 5.1.3 of [RFC5085], and in all cases requires the use of
      a CW (see Section 7 of [RFC4385]).  When VCCV carries PW-ACH-
      encapsulated BFD (i.e., "raw" BFD), the PW-ACH (Pseudowire CW's or
      L2SS') Channel Type MUST be set to 0x0007 to indicate "BFD
      Control, PW-ACH-encapsulated" (i.e., BFD Without IP/UDP Headers,
      see Section 5.2).  This is to allow the identification of the
      encased BFD payload when demultiplexing the VCCV control channel.




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      If the PW is establised by signaling, then the BFD CV Type used
      for this encapsulation is either 0x10 or 0x20.

   In summary, for the IP/UDP encapsulation of BFD (BFD with IP/UDP
   headers), if a PW Associated Channel Header is used, the Channel Type
   MUST indicate either IPv4 (0x0021) or IPv6 (0x0057).  For the PW-ACH
   encapsulation of BFD (BFD without IP/UDP headers), the PW Associated
   Channel Header MUST be used and the Channel Type MUST indicate BFD
   Control packet (0x0007).

3.3.  CV Types for BFD

   The CV Type is defined as a bitmask field used to indicate the
   specific CV Type or Types (i.e., none, one or more) of VCCV packets
   that may be sent on the VCCV control channel.  The CV Types shown in
   the table below augment those already defined in [RFC5085].  Their
   values shown in parenthesis represent the numerical value
   corresponding to the actual bit being set in the CV Type bitfield.

   BFD CV Types:

      The defined values for the different BFD CV Types for MPLS and
      L2TPv3 PWs are:

      Bit (Value)   Description
      ============  ====================================================
      Bit 2 (0x04)  BFD IP/UDP-encapsulated, for PW Fault Detection only
      Bit 3 (0x08)  BFD IP/UDP-encapsulated, for PW Fault Detection and
                    AC/PW Fault Status Signaling
      Bit 4 (0x10)  BFD PW-ACH-encapsulated, for PW Fault Detection only
      Bit 5 (0x20)  BFD PW-ACH-encapsulated, for PW Fault Detection and
                    AC/PW Fault Status Signaling

   It should be noted that four BFD CV Types have been defined by
   combining two types of encapsulation with two types of functionality,
   see Table 1 in Section 3.

   Given the bidirectional nature of BFD, before selecting a given BFD
   CV Type capability to be used in dynamically established pseudowires,
   there MUST be common CV Types in the VCCV capability advertised and
   received.  That is, only BFD CV Types that were both advertised and
   received are available to be selected.  Additionally, only one BFD CV
   Type can be used (selecting a BFD CV Type excludes all the remaining
   BFD CV Types).

   The following list enumerates rules, restrictions and clarifications
   on the usage of BFD CV Types:




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   1.  BFD CV Types used for fault detection and status signaling (i.e.,
       CV Types 0x08 and 0x20) SHOULD NOT be used when a control
       protocol such as LDP [RFC4447] or L2TPV3 [RFC3931] is available
       that can signal the AC/PW status to the remote endpoint of the
       PW.  More details can be found in [I-D.ietf-pwe3-oam-msg-map].

   2.  BFD CV Types used for fault detection only (i.e., CV Types 0x04
       and 0x10) can be used whether a protocol that can signal AC/PW
       status is available or not.  This includes both statically
       provisioned and dynamically signaled pseudowires.

       2.1.  In this case, BFD is used exclusively to detect faults on
             the PW; if it is desired to convey AC/PW fault status, some
             means other than BFD are to be used.  Examples include
             using LDP status messages when using MPLS as a transport
             (see Section 5.4 of [RFC4447]), and the Circuit Status AVP
             in an L2TPv3 SLI message for L2TPv3 (see Section 5.4.5 of
             [RFC3931]).

   3.  Pseudowires that do not use a CW or L2SS using the PW Associated
       Channel Header MUST NOT use the BFD CV Types 0x10 or 0x20 (i.e.,
       PW-ACH encapsulation of BFD, without IP/UDP headers).

       3.1.  PWs that use a PW-ACH include CC Type 1 (for both MPLS and
             L2TPv3 as defined in Sections 5.1.1 and 6.1 of [RFC5085]),
             and MPLS CC Types 2 and 3 when using a Control Word (as
             specified in Sections 5.1.2 and 5.1.3 of [RFC5085]).  This
             restriction stems from the fact that the encapsulation uses
             the Channel Type in the PW-ACH.

       3.2.  PWs that do not use a PW-ACH can use the VCCV BFD
             encapsulation with IP/UDP headers, as the only VCCV BFD
             encapsulation supported.  Using the IP/UDP encapsulated BFD
             CV Types allows for the concurrent use of other VCCV CV
             Types that uses an encapsulation with IP headers (e.g.,
             ICMP Ping or LSP Ping defined in [RFC5085]).

   4.  Only a single BFD CV Type can be selected and used.  All BFD CV
       Types are mutually exclusive.  After selecting a BFD CV Type, a
       node MUST NOT use any of the other three BFD CV Types.

   5.  Once a PE has chosen a single BFD CV Type to use, it MUST
       continue using it until when the PW is re-signaled.  In order to
       change the negotiated and selected BFD CV Type, the PW must be
       torn-down and re-established.






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4.  Capability Selection

   The precedence rules for selection of various CC and CV Types is
   clearly outlined in Section 7 of [RFC5085].  This section augments
   these rules when the BFD CV Types defined herein are supported.  The
   selection of a specific BFD CV Type to use out of the four available
   CV Types defined is tied to multiple factors, as described in
   Section 3.3.  Given that BFD is bidirectional in nature, only CV
   Types that are both received and sent in VCCV capability signaling
   advertisement can be selected.

   When multiple BFD CV Types are advertised, and after applying the
   rules in Section 3.3, the set that both ends of the pseudowire have
   in common is determined.  If the two ends have more than one BFD CV
   Type in common, the following list of BFD CV Types is considered in
   the order of the lowest list number CV Type to the highest list
   number CV Type, and the CV Type with the lowest list number is used:

   1.  0x20 - BFD PW-ACH-encapsulated (without IP/UDP headers), for PW
       Fault Detection and AC/PW Fault Status Signaling

   2.  0x10 - BFD PW-ACH-encapsulated (without IP/UDP headers), for PW
       Fault Detection only

   3.  0x08 - BFD IP/UDP-encapsulated, for PW Fault Detection and AC/PW
       Fault Status Signaling

   4.  0x04 - BFD IP/UDP-encapsulated, for PW Fault Detection only


5.  IANA Considerations

5.1.  MPLS CV Types for the VCCV Interface Parameters Sub-TLV

   The VCCV Interface Parameters Sub-TLV codepoint is defined in
   [RFC4446], and the VCCV CV Types registry is defined in [RFC5085].
   This section lists the new BFD CV Types.

   IANA is requested to augment the "VCCV Connectivity Verification
   Types" registry in the Pseudo Wires Name Spaces, reachable from
   [IANA.pwe3-parameters].  These are bitfield values.  CV Type values
   0x04 0x08, 0x10 and 0x20 are specified in Section 3 of this document.









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      MPLS Connectivity Verification (CV) Types:

      Bit (Value)   Description
      ============  ====================================================
      Bit 2 (0x04)  BFD IP/UDP-encapsulated, for PW Fault Detection only
      Bit 3 (0x08)  BFD IP/UDP-encapsulated, for PW Fault Detection and
                    AC/PW Fault Status Signaling
      Bit 4 (0x10)  BFD PW-ACH-encapsulated, for PW Fault Detection only
      Bit 5 (0x20)  BFD PW-ACH-encapsulated, for PW Fault Detection and
                    AC/PW Fault Status Signaling

5.2.  PW Associated Channel Type

   The PW Associated Channel Types used by VCCV rely on previously
   allocated numbers from the Pseudowire Associated Channel Types
   Registry [RFC4385] in the Pseudo Wires Name Spaces reachable from
   [IANA.pwe3-parameters].

   IANA is requested to reserve a new Pseudowire Associated Channel Type
   value as follows:


   Registry:
                                                TLV
    Value   Description                         Follows  Reference
    ------  ----------------------------------  -------  ---------------
    0x0007  BFD Control, PW-ACH encapsulation   No       [This document]
            (without IP/UDP Headers)

5.3.  L2TPv3 CV Types for the VCCV Capability AVP

   This section lists the new BFD CV Types to be added to the existing
   "VCCV Capability AVP" registry in the L2TP name spaces.  The Layer
   Two Tunneling Protocol "L2TP" Name Spaces are reachable from
   [IANA.l2tp-parameters].

   IANA is requested to reserve the following L2TPv3 Connectivity
   Verification (CV) Types in the VCCV Capability AVP Values registry.













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      VCCV Capability AVP (Attribute Type AVP-TBD) Values
      ---------------------------------------------------

      L2TPv3 Connectivity Verification (CV) Types:

      Bit (Value)   Description
      ============  ====================================================
      Bit 2 (0x04)  BFD IP/UDP-encapsulated, for PW Fault Detection only
      Bit 3 (0x08)  BFD IP/UDP-encapsulated, for PW Fault Detection and
                    AC/PW Fault Status Signaling
      Bit 4 (0x10)  BFD PW-ACH-encapsulated, for PW Fault Detection only
      Bit 5 (0x20)  BFD PW-ACH-encapsulated, for PW Fault Detection and
                    AC/PW Fault Status Signaling


6.  Congestion Considerations

   The congestion considerations that apply to [RFC5085] apply to this
   mode of operation as well.  This section describes explicitly how
   they apply.

   BFD as a VCCV application is required to provide details on
   congestion and bandwidth considerations.  BFD provides with a desired
   minimum transmit interval, a required minimum receive interval,
   negotiates the transmission interval using these configurable fields,
   and has a packet of fixed size (setting the transmission rate).
   Therefore, it results in a configuration limited bandwidth
   utilization.  As stated in [RFC5085], this is sufficient protection
   against congestion as long as BFD's configured maximum bit-rate is
   minimal compared to the bit-rate of the pseudowire the VCCV channel
   is associated with.  If the pseudowire bit-rate can't be guaranteed
   to be minimal, like potentially for highly variable bit-rate and/or
   congestion responsive pseudowires, BFD will be required to operate
   using an adaptive congestion control mechanism (for example including
   a throttled transmission rate on "congestion detected" situations,
   and a slow-start after shutdown due to congestion and until basic
   connectivity is verified).

   Since the bandwidth utilized by BFD is configuration-limited, the
   VCCV channel MUST NOT be rate limited below this maximum configurable
   bandwidth or BFD will not operate correctly.  The VCCV channel could
   provide rate-limiting above the maximum BFD rate, to protect from a
   mis-behaving BFD application, so that it does not conflict and can
   coexist.  Additionally, the VCCV channel SHOULD NOT use any
   additional congestion control loop that would interfere or negatively
   interact with that of BFD.  There are no additional congestion
   considerations.




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7.  Security Considerations

   Routers that implement the additional CV Types defined herein are
   subject to the same security considerations as defined in [RFC5085],
   [I-D.ietf-bfd-base], and [I-D.ietf-bfd-v4v6-1hop].  This
   specification does not raise any additional security issues beyond
   these.  The IP/UDP-encapsulated BFD makes use of the TTL/Hop Limit
   procedures described in Section 5 of [I-D.ietf-bfd-v4v6-1hop],
   including the use of the Generalized TTL Security Mechanism (GTSM) as
   a security mechanism.


8.  Acknowledgements

   This work forks from a previous revision of the PWE3 WG document that
   resulted in [RFC5085], to which a number of people contributed,
   including Rahul Aggarwal, Peter B. Busschbach, Yuichi Ikejiri, Kenji
   Kumaki, Luca Martini, Monique Morrow, George Swallow, and others.

   Mustapha Aissaoui, Sam Aldrin, Stewart Bryant, Peter B. Busschbach,
   Annamaria Fulignoli, Vishwas Manral, Luca Martini, Dave McDysan, Ben
   Niven-Jenkins, Pankil Shah, Yaakov Stein, and George Swallow provided
   useful feedback and valuable comments and suggestions improving newer
   versions of this document.


9.  References

9.1.  Normative References

   [I-D.ietf-bfd-base]
              Katz, D. and D. Ward, "Bidirectional Forwarding
              Detection", draft-ietf-bfd-base-09 (work in progress),
              February 2009.

   [I-D.ietf-bfd-generic]
              Katz, D. and D. Ward, "Generic Application of BFD",
              draft-ietf-bfd-generic-05 (work in progress),
              February 2009.

   [I-D.ietf-bfd-v4v6-1hop]
              Katz, D. and D. Ward, "BFD for IPv4 and IPv6 (Single
              Hop)", draft-ietf-bfd-v4v6-1hop-09 (work in progress),
              February 2009.

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




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   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

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

9.2.  Informative References

   [I-D.ietf-pwe3-oam-msg-map]
              Martini, L., Nadeau, T., Aissaoui, M., Allan, D., and Y.
              Stein, "Pseudo Wire (PW) OAM Message Mapping",
              draft-ietf-pwe3-oam-msg-map-11 (work in progress),
              June 2009.

   [IANA.l2tp-parameters]
              Internet Assigned Numbers Authority, "Layer Two Tunneling
              Protocol "L2TP"", July 2009,
              <http://www.iana.org/assignments/l2tp-parameters>.

   [IANA.pwe3-parameters]
              Internet Assigned Numbers Authority, "Pseudowire Name
              Spaces (PWE3)", June 2009,
              <http://www.iana.org/assignments/pwe3-parameters>.

   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.

   [RFC4379]  Kompella, K. and G. Swallow, "Detecting Multi-Protocol
              Label Switched (MPLS) Data Plane Failures", RFC 4379,
              February 2006.

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

   [RFC4447]  Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
              Heron, "Pseudowire Setup and Maintenance Using the Label
              Distribution Protocol (LDP)", RFC 4447, April 2006.

   [RFC5586]  Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic
              Associated Channel", RFC 5586, June 2009.









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Authors' Addresses

   Thomas D. Nadeau (editor)
   BT
   BT Centre
   81 Newgate Street
   London,   EC1A 7AJ
   United Kingdom

   Email: tom.nadeau@bt.com


   Carlos Pignataro (editor)
   Cisco Systems, Inc.
   7200 Kit Creek Road
   PO Box 14987
   Research Triangle Park, NC  27709
   USA

   Email: cpignata@cisco.com































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