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Versions: (draft-nadeau-pwe3-vccv) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 5085

Network Working Group                            Thomas D. Nadeau
Internet Draft                                   Cisco Systems, Inc.
Expires: August 2004
                                                 Rahul Aggarwal
                                                 Juniper Networks
                                                 Editors

                                                 February 2004




    Pseudo Wire (PW) Virtual Circuit Connection Verification
                              (VCCV)
                   draft-ietf-pwe3-vccv-02.txt


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.  Internet-Drafts are
   working documents of the Internet Engineering Task Force (IETF), its
   areas, and its working groups.  Note that other groups may also
   distribute working documents as Internet-Drafts.

   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".

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   Distribution of this document is unlimited.  Please send comments to
   the Multiprotocol Label Switching (mpls) Working Group, mpls@uu.net.

Abstract

   This document describes Virtual Circuit Connection Verification
   (VCCV) procedures for use with pseudowire connections. VCCV
   supports connection verification applications for pseudowire
   VCs regardless of the underlying MPLS or IP tunnel technology.
   VCCV makes use of IP based protocols such as Ping and MPLS
   LSP Ping to perform operations and maintenance functions. This
   is accomplished by providing an IP control channel associated
   with each pseudowire. A network operator may use the VCCV
   procedures to test the network's forwarding plane liveliness.



Contents



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   Abstract...............................................................1
1. Contributors...........................................................1
2. Introduction...........................................................2
3. Overview of VCCV Modes of Operation....................................3
4. MPLS as PSN............................................................3
5. IP Probe Traffic.......................................................5
6. OAM Capability Indication..............................................6
7. L2TPv3/IP as PSN.......................................................8
8. Acknowledgments.......................................................11
9. References............................................................11
9.2 Normative References.................................................11
9.2 Informative References...............................................11
10. Security Considerations..............................................12
11. Intellectual Property Rights Notices.................................12
12. Full Copyright Statement.............................................13


1. Contributors

  Thomas D. Nadeau                       Rahul Aggarwal
  Cisco Systems, Inc.                    Juniper Networks
  300 Beaver Brook Road                  1194 North Mathilda Ave.
  Boxborough, MA 01719                   Sunnyvale, CA 94089
  Email: tnadeau@cisco.com               Email: rahul@juniper.net

  George Swallow                         Monique Morrow
  Cisco Systems, Inc.                    Cisco Systems, Inc.
  300 Beaver Brook Road                  Glatt-com
  Boxborough, MA 01719                   CH-8301 Glattzentrum
  Email: swallow@cisco.com               Switzerland
                                         Email: mmorrow@cisco.com

  Yuichi Ikejiri                         Kenji Kumaki
  NTT Communication Corporation          KDDI Corporation
  1-1-6, Uchisaiwai-cho, Chiyoda-ku      KDDI Bldg. 2-3-2,
  Tokyo 100-8019                         Nishishinjuku,
  Shinjuku-ku, JAPAN                     Tokyo 163-8003,
  Email: y.ikejiri@ntt.com               JAPAN
                                         E-mail: ke-kumaki@kddi.com

  Peter B. Busschbach                    Vasile Radoaca
  Lucent Technologies                    Nortel Networks
  67 Whippany Road                       Billerica, MA, 01803
  Whippany, NJ, 07981                    Email: vasile@nortelnetworks.com
  E-mail: busschbach@lucent.com          Voice: 978-288-6097


2. Introduction



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   As network operators deploy pseudowire services, fault
   detection and diagnostic mechanisms particularly for the PSN
   portion of the network are pivotal. Specifically, the ability
   to provide end-to-end fault detection and diagnostics for an
   emulated pseudowire service is critical for the network
   operator. Operators have indicated in [MPLSOAMREQS] that such
   a tool is required for pseudowire deployments. This document
   describes procedures for PSN-agnostic fault detection and
   diagnostics called virtual circuit connection verification
   (VCCV).


                         |<----- Pseudo Wire ---->|
                         |                        |
             Emulated    |  |<-- PSN Tunnel -->|  |   Emulated
              Service    V  V                  V  V    Service
                 |     +----+                  +----+     |
       +----+    |     | PE1|==================| PE2|     |    +----+
       |    |----------|............PW1.............|----------|    |
       | CE1|    |     |    |                  |    |     |    |CE2 |
       |    |----------|............PW2.............|----------|    |
       +----+    |     |    |==================|    |     |    +----+
            ^          +----+                  +----+     |    ^
            |      Provider Edge 1         Provider Edge 2     |
            |                                                  |
            |<-------------- Emulated Service ---------------->|
                         |<---------- VCCV ------>|
       Customer                                                Customer
       Edge 1                                                  Edge 2

            Figure 1: PWE3 VCCV Operation Reference Model

   Figure 1 depicts the basic functionality of VCCV. VCCV provides
   several means of creating a control channel between PEs that
   attaches the VC under test.


   +-------------+                                +-------------+
   |  Layer2     |                                |  Layer2     |
   |  Emulated   |                                |  Emulated   |
   |  Services   |         Emulated Service       |  Services   |
   |             |                                |             |
   +-------------+         VCCV/pseudowire        +-------------+
   |Demultiplexer|                                |Demultiplexor|
   +-------------+                                +-------------+
   |    PSN      |            PSN Tunnel          |    PSN      |
   |   MPLS      |                                |   MPLS      |
   +-------------+                                +-------------+
   |  Physical   |                                |  Physical   |



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   +-----+-------+                                +-----+-------+
         |                                              |
         |             ____     ___       ____          |
         |           _/    \___/   \    _/    \__       |
         |          /               \__/         \_     |
         |         /                               \    |
         ---------|      MPLS or IP Network        |-----
                  \                                /
                   \   ___      ___     __      _/
                    \_/   \____/   \___/  \____/

      Figure 2: PWE3 Protocol Stack Reference Model
                including the VCCV control channel.

   Figure 2 depicts how the VCCV IP control channel is associated
   with the pseudowire. Ping and other IP messages are encapsulated
   using the PWE3 encapsulation as described below in sections 5 and
   6. These messages, referred to as VCCV messages, are exchanged
   only after the desire to exchange such traffic has been
   negotiated between the PEs (see section 8).


3. Overview of VCCV Modes of Operation

   VCCV defines a set of messages that are exchanged between PEs to
   verify connectivity of the pseudowire. To make sure that pseudowire
   packets follow the same path as the data flow, they are encapsulated
   with the same labels. VCCV can operate in two modes:

   1) as a diagnostic tool
   2) as a fault detection tool

   In the diagnostic mode, the operator triggers LSP-Ping, L2TPV3,
   or ICMP Ping modes depending on the underlying PSN. Since a
   pseudowire is bi-directional, it makes sense to require that the
   reply is send over the PSN tunnel that makes up the other half
   of the PW under test. For example, if the PSN is an MPLS LSP,
   the reply should be sent on the LSP representing the reverse
   path. If this fails, the operator can use other reply modes to
   determine what is wrong. The specific type of reply mode is
   indicated during PW circuit set-up (see section 6).

   The fault detection mode provides a way to emulate fault
   detection mechanisms in other technologies, such as ATM for
   example. In the fault detection mode, the upstream PE sends
   BFD control messages periodically. [BFD-MPLS] describes
   procedures for using BFD to detect liveliness of MPLS LSPs.
   When the downstream PE doesn't receive these message for
   a defined period of time, it declares that direction of the
   PW down and it notifies the upstream PE. Based on the emulated



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   service, the PEs may send FDI and RDI indications over the related
   attachment circuits to notify the end points of the fault condition.
   This is described in more detail in [OAMMsgMap].


3.1 LSP Ping

   When the PSN is MPLS, the LSP Ping header is used as described
   in [LSP-PING] for verifying the connectivity status of pseudo
   wires.

3.2 L2TPV3

   When L2TPv3 is used as the underlying PSN, a VCCV mechanism is
   needed for the L2TPv3 session. The L2TPv3 control connection does
   employ a keepalive mechanism; however, this mechanism is not
   sufficent for fault detection and diagnostic of the L2TPv3 session
   i.e. data plane. In L2TPv3, a session is analogous to a PW. A L2TPv3
   VCCV mechanism is needed in particular for verifying the session
   forwarding state at the egress router.

3.3 ICMP Ping

   When IP is used as the PSN, ICMP ECHO packets can be used
   as the means by which connectivity verification is achieved
   using VCCV.

3.4 Bidirectional Forwarding Detection

   When heart-beat indication is necessary for one or more
   pseudowires, the Bidirectional Forwarding Detection (BFD)
   [BFD] provides a light-weight means of continuous
   monitoring and propagation of forward and reverse defect
   indications.  BFD can be used regardless of the underlying
   PSN technology.


4. MPLS as PSN

   In order to apply IP monitoring tools to PWE3 circuits, VCCV
   creates a control channel between PWE3 PEs[PWEARCH].  Packets
   sent across this channel are IP packets, allowing maximum
   flexibility.

   Ideally such a control channel would be completely in band.
   When a control word is present on virtual circuit, it is
   possible to indicate the control channel by setting a bit in
   the control header.  This method is described in section 7.1
   and is referred to as PWE3 inband VCCV.




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   However in order to address the case when the control header
   is not in use as well as to deal with a number of existent
   hardware devices, use of the MPLS Router Alert Label to indicate
   the IP control channel is also proposed.  This is described in
   section 7.2.

   The actual channel type is agreed through signaling as
   described in section 8.

4.1.  PWE3 Inband VCCV

   The PW set-up protocol determines whether a PW uses a control word.
   When a control word is used, it SHOULD have the following preferred
   form:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 1| Flags |FRG|  Length   | Sequence Number               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   for the purpose of indicating VCCV control channel messages.

   Note that for data, one uses the control word defined just
   above the MPLS payload [PWEARCH].

   The PWE3 payload type identifier is defined as follows:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 1|  reserved             | PPP DLL Protocol Number       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           As defined by PPP DLL protocol definition           |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The first nibble 0000 indicates data.  When the first nibble is=20
   0001, the protocol of the frame is indicated by the Protocol
   Number.  IP OAM flows are identified by either an IPv4 or IPv6
   codepoint.

4.2.  Router Alert Label Approach

   When the control word is not used, or the receiving hardware
   cannot divert control traffic based on information in the control
   word (i.e.: older hardware), an IP control channel can be
   created by including the MPLS router alert label immediately
   above the VC label.  If the control word is in use on this VC



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   it is also included in the IP control flow.


5. IP Probe Traffic

   For connectivity verification, both ICMP Ping and LSP-Ping
   packets may be used on the control channel.  The type of
   packets used is indicated during signaling as described in
   section 6.

5.1.  ICMP Ping

   When ICMP packets are used, the source address should be set
   to the source address of the LDP session and the destination
   address to the destination of the LDP session.  The Identifier
   and Sequence Number fields of the ICMP Echo Request/Echo
   Reply messages are used to track what VCs are being tested.

   These fields are only interpreted by the sending PE.  Specific
   use of these fields is an implementation matter.


5.2.  MPLS Ping Packet

   The LSP Ping header must be used as described [LSP-PING] and
   must also contain the sub-TLV of 8 for PW circuits.  This
   sub-TLV must be sent containing the circuit to be verified as
   the "VC ID" field:

5.3   Bidirectional Forwarding Detection

   When heart-beat indication is necessary for one or more
   pseudowires, the Bidirectional Forwarding Detection (BFD)
   [BFD] provides a light-weight means of continuous
   monitoring and propagation of forward and reverse defect
   indications.

   In order to use BFD, both ends of the pseudowire connection must
   have signaled the existence of a control channel and the ability to
   run BFD.  Once a node has both signaled and received signaling from
   its peer of these capabilities, it MUST begin sending BFD control
   packets.  The packets MUST be sent on the control channel.  The use
   of the control channel provides the context required to bind the
   BFD session to a particular pseudowire (FEC).  Thus normal BFD
   initialization procedures are followed.  BFD MUST be run in
   asynchronous mode.

   It may be desirable to use LSP-Ping additionally for periodic
   diagnostics in addition to BFD for fault detection on the same PW.
   [BFD-MPLS] provides further details on how BFD can be used in



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   conjunction with LSP-Ping for detecting the liveliness
   of MPLS LSPs.

   When one of the PEs (PE2) doesn't receive control messages
   from PE1 during the specified amount of time, or if it
   determines in another way that communication is lost,it
   declares that the PW in the direction from PE1 to PE2 is down.
   It stores the cause (e.g. control detection time expired) and
   sends a message to PE1 with H=3D0 (i.e. "I don't hear you"). In
   turn, PE1 declares the PW in the direction from PE1 to PE2
   down and stores as cause: neighbor signaled session down.
   Depending on the emulated services, PE2 may send a FDI
   indication on its attachment circuits and PE1 may send an RDI
   indication on its attachment circuits.

   BFD defines the following diagnostics:

       0 -- No Diagnostic
       1 -- Control Detection Time Expired
       2 -- Echo Function Failed
       3 -- Neighbor Signaled Session Down
       4 -- Forwarding Plane Reset (Local equipment failure)
       5 -- Path Down (Alarm Suppression)
       6 -- Concatenated Path Down (Propagating access link alarm)
       7 -- Administratively Down

    Of these, 0 is used when the PW is up and 2 is not applicable
    to asynchronous mode.


6. OAM Capability Indication

   To permit negotiation of the use and type of OAM for
   Connectivity Verification, a VCCV parameter is defined below.
   When a PE signals a PWE3 VC and desires OAM for that VC, it
   MUST indicate this during VC establishment using the messages
   defined below.  Specifically for LDP it MUST include the VCCV
   parameter in the VC setup message.

   As the overall method of PWE3 signaling is
   downstream, unsolicited, the decision of the type
   of IP control channel is left completely to the receiving control
   entity.  When a PE sends a label for a PW, it uses the VCCV parameter
   to indicate the type of OAM channels it is willing to receive on that
   PW. The capablity of supporting a control channel MUST be signaled
   BEFORE the remote PE may send OAM messages, and then only on the type
   of control channel indicated.

   If a PE receives OAM messages prior to sending
   a VCCV parameter, it MUST discard these messages and not reply



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   to them. In this case, the LSR SHOULD increment an error counter
   and optionally issues a system and/or SNMP notification to indicate
   to the system administrator that a mis-configuration exists.

   The requesting PE indicates its desire for the remote PE to
   support OAM capability by including the VCCV parameter with
   appropriate options set to indicate which methods of OAM are
   acceptable.  The requesting PE MAY indicate multiple
   IP control channel options.  The absence of the VCCV FEC TLV
   indicates that no OAM functions are supported or desired by
   the requesting PE.  This last method MUST be supported by all
   PEs in order to handle backward-compatibility with older PEs.
   The receiving PE agrees to accept any of the indicated
   OAM types and options by virtue of establishing the VC. If
   it does not or cannot support at least one of the options
   specified, it MUST not establish the VC. If the requesting
   PE wishes to continue, it may choose different options and
   try to signal the PW again.

6.1.  Optional VCCV Parameter

   [PWE3CONTROL] defines a VC FEC TLV for LDP.  Parameters can be
   carried within that TLV to signal different capabilities for
   specific PWs. We propose an optional parameter to be used to
   indicate the desire to use a control channel for VCCV as
   follows.

   The TLV field structure is defined in [PWE3CONTROL] as
   follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Parameter ID |    Length     |    Variable Length Value      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Variable Length Value                 |
   |                             "                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The VCCV parameter ID is defined as follows in [PWE3IANA]:

     Parameter ID   Length     Description
       0x0a           4           VCCV


   The format of the VCCV parameter TLV is as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   |      0x0a     |       0x04    |CC Type| CV Type Indicators    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The CC type field defines the type of IP control channel
   that will be used to receive. The defined values are:

    0x01 PWE3 control word (0x0001 as first nibble of CW)
    0x02 MPLS Router Alert Label

   The CV Type Indicators field defines a bitmask used to indicate the
   specific type or types (i.e.: one or more) of IP control packets
   that may be sent on the control channel.  The defined values
   are:

    0x01  ICMP Ping
    0x02  LSP Ping
    0x04  BFD

    If none of the types above are supported, a CV Type Indicator
    of 0x00 SHOULD be transmitted to indicate this to the peer. However,
    if no capability is signaled, then the peer MUST assume that
    the peer has no VCCV capability.

7.  L2TPV3 as PSN

   When L2TPv3 is used as the underlying PSN, a VCCV mechanism is
   needed for the L2TPv3 session. The L2TPv3 control connection does
   employ a keepalive mechanism. However this mechanism is not
   sufficent for fault detection and diagnostic of the L2TPv3 session
   i.e. data plane. In L2TPv3 a session is analogous to a PW. A L2TPv3
   VCCV mechanism is needed in particular for verifying the session
   forwarding state at the egress router.

   When a PE verifies the connection status of a L2TPv3 session it must
   transmit a L2TPv3 VCCV message encoded in the L2TPv3 session packet.

   The presence of a VCCV message in a L2TPv3 session packet can be
   indicated by reserving a bit in the default L2-specific sublayer
   format.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |P|S|V|x|x|x|x|x|              Sequence Number                  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Default L2-Specific Sublayer Format with V bit.

   The 'V' bit indicates that this is a VCCV session packet. If the PW
   has not been signaled to include a L2-specific sublayer format, other



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   mechanisms are needed to indicate the VCCV message. Such mechanisms
are for further study.

7.1. L2TPv3 VCCV Message

   The VCCV message MUST contain a VCCV AVP. It does not contain a
   messageheader. A new AVP, called the VCCV AVP is defined. The usage of
   the L2TPv3 AVP format leaves room for adding further AVPs to this
   message in the future as needed.

7.1.1. L2TPv3 VCCV AVP

   This AVP encodes the LSP Ping header as defined in [LSP-PING]. M and H
   bits must not be set. The attribute type is TBD. The LSP Ping header
   is not encapsulated in UDP. The modifications to the semantics of the
   fields of this header are specified here. Unless otherwise specified
   the semantics of the fields as explained in [LSP-PING] are to be
   followed. For reference the format of the LSP Ping header is shown
   below.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Version Number        |         Must Be Zero          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Message Type |   Reply mode  |  Return Code  | Return Subcode|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sender's Handle                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    TimeStamp Sent (seconds)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  TimeStamp Sent (microseconds)                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  TimeStamp Received (seconds)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                TimeStamp Received (microseconds)              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            TLVs ...                           |
      .                                                               .
      .                                                               .
      .                                                               .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The version number is currently 1. The message type is one of the
   following:




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   1 - L2TPv3 VCCV Echo Request
   2 - L2TPv3 VCCV Echo Reply

   The Reply Mode is:

   1 - Do not reply
   2 - Reply using the L2TPv3 session

   As explained in [LSP-PING] a reply mode of "do not reply" can be used

   for one way connectivity tests. The VCCV message will normally
contain a reply mode of "reply using the L2TPv3 session".

   The return code can be set to the following by the receiver:

   1 - Malformed echo request received
   2 - One or more of the TLVs was not understood
   3 - Replying router has a session mapping for the verified pseudowire
   4 - Replying router does not have a mapping for the verified pseudowire

   The LSP Ping header must contain the L2 Circuit ID TLV as defined in
   section 8.2. This TLV identifies the pseudo wire associated with the
   session, that is being verified. For L2TPv3 the remote PE address is
   the address of the session's remote end. A new PWID type is defined
   for L2TPv3, in addition to the ones defined in section 8.2:

   3. L2TPv3 Remote End Identifier AVP

7.2. L2TPv3 VCCV Capability Negotiation

   A LCCE or a LAC should be able to indicate whether the session is
   capable of processing VCCV packets. This is done by including the
   optional VCCV capability AVP in an ICRQ, ICRP, OCRQ or OCRP.

7.2.1. L2TPv3 VCCV Capability AVP

   This AVP specifies the VCCV capability. Its attribute type
   is TBD. The value field has the following format:

       0                   1
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
      | Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

7.3. L2TPv3 VCCV Operation

   A PE sends VCCV echo requests on a L2TPv3 signaled pseudo wire for
   fault detection and diagnostic of the L2TPv3 session. The destination




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   IP address in the echo request is set to the remote PE's IP address,
   while the source IP address is set to the local PE's IP address. The
   egress of the L2TPv3 session verifies the signaling and forwarding
   state of the pseudo wire, on reception of the VCCV message. Any faults
   detected can be signaled in the VCCV echo response. Its to be noted
   that the VCCV mechanism for L2TPv3 is primarily targeted at verifying
   the pseudo wire forwarding and signaling state at the egress PE. It
   also helps when L2TPv3 control and session paths are not identical.

  A PE must send VCCV packets on a L2TPv3 session only if it has
  signaled VCCV capability to the remote end and received VCCV capability
  from the remote end. If a PE receives VCCV packets and its not VCCV
  capable or it has not received VCCV capability indication from the
  remote end, it must discard these messages. In addition if a PE receives
  VCCV messages and it has not received VCCV capability from the remote
  end, it should increment an error counter. In this case the PE can
  optionally issue a system and/or SNMP notification.


8.   Acknowledgments

   The authors would like to thank Hari Rakotoranto, Michel
   Khouderchah, Bertrand Duvivier, Vanson Lim, Chris Metz, W.Mark
   Townsley, Eric Rosen, Dan Tappan,and Danny McPherson for their
   valuable comments and suggestions.


9.   References

9.1 Normative References

[BFD]      Katz, D., Ward, D., Bidirectional Forwarding
           Indication, draft-katz-ward-bfd-01.txt, August
           2003, work in progress.

[PWREQ]    Xiao, X., McPherson, D., Pate, P., "Requirements for
           Pseudo Wire Emulation Edge to-Edge (PWE3)", <
           draft-ietf-pwe3-requirements-08.txt>, December 2003

[PWE3FW]   Prayson Pate, et al., Internet draft, Framework for
           Pseudo Wire Emulation Edge-to-Edge (PWE3), draft-
           ietf-pwe3-framework-01.txt, work in progress.

[PWEARCH]  Bryant, S., Pate, P., "PWE3 Architecture", Internet
           Draft, < draft-ietf-pwe3-arch-06.txt>, October 2003

[PWE3IANA] Martini, L., Townsley, M., "IANA Allocations fo
           pseudo Wire Edge to Edge Emulation (PWE3)",
           draft-ietf-pwe3-iana-allocation-01.txt, June
           2003,  work in progress.



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[L2SIG]    Rosen, E., LDP-based Signaling for L2VPNs,
           Internet Draft <draft-rosen-ppvpn-l2-signaling-02.txt>,
           September 2002.

[LSPPING]  Kompella, K., Pan, P., Sheth, N., Cooper, D., Swallow,
           G., Wadhwa, S., Bonica, R., " Detecting MPLS Data Plane
           Failures", Internet Draft < draft-ietf-mpls-lsp-ping-04.txt>,
           October 2003

[MARTINISIG] "Transport of Layer 2 Frames Over MPLS", Martini et.
             al., draft-martini-l2circuit-trans-mpls-10.txt,
             August 2002


9.2 Informative References

[ICMP]     Postel, J. "Internet Control Message Protocol,  RFC 792

[PWEATM]   Martini, L., et al., "Encapsulation Methods for
           Transport of ATM Cells/Frame Over IP and MPLS=20
           Networks", Internet Draft <draft-ietf-pwe3-atm-
           encap-00.txt>, October 2002

[MPLSOAMREQS] Nadeau, T., et al,"OAM Requirements for MPLS
              Networks, Internet Draft
              <draft-ietf-oam-requirements-02.txt>, June 2003.

[OAMMsgMap] Nadeau, T., et al, " Pseudo Wire (PW) OAM Message
            Mapping, Internet Draft < draft-nadeau-pwe3-oam-msg-map-04.txt>,
            January, 2004.

[PWE3CONTROL] L.Martini et al., "Transport of Layer 2 Frames
              over MPLS, Internet Draft, <draft-ietf-pwe3-control-
              protocol-01.txt>, May 2003

[PPVPNFW]     Callon, R., Suzuki, M., Gleeson, B., Malis, A.,
              Muthukrishnan, K., Rosen, E., Sargor, C., and J. Yu,=20
              "A Framework for Provider Provisioned Virtual=20
              Private Networks", Internet Draft <draft-ietf-
              ppvpn-framework-01.txt>, July 2001.

[RFC3031]  Rosen, E., Viswanathan, A., and R. Callon,
           "Multiprotocol Label Switching Architecture", RFC 3031,
           January 2001.

[BFD-MPLS] Aggarwal, R. Kompella, K. "BFD for MPLS LSPs", Internet
           Draft <draft-raggarwa-mpls-bfd-00.txt>, October 2003.

10.   Security Considerations



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      TBD.


11.   Intellectual Property Rights Notices

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11.   Full Copyright Statement

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   DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT



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   NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
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