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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 5357

                                                             J. Babiarz
  Internet Draft                                        Nortel Networks
  Expires: May 11, 2006                                      K. Hedayat
                                                          Brix Networks
                                                          R. Krzanowski
                                                                Verizon
                                                               Kiho Yum
                                                      Juniper  Networks
                                                       November 7, 2005
 
                A Two-way Active Measurement Protocol (TWAMP)
                        draft-ietf-ippm-twamp-00
 
 
 Status of this Memo
 
 
    By submitting this Internet-Draft, each author represents that any
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 Copyright Notice
 
    Copyright (C) The Internet Society (2005).
 
 
 Abstract
 
 
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    The IPPM One-way Active Measurement Protocol [OWAMP] provides a
    common protocol for measuring one-way metrics between network
    devices.  OWAMP [OWAMP] can be used in both directions
    independently to measure one-way metrics in both directions between
    two network elements.  However, it does not accommodate round-trip
    or two-way measurements.  This draft proposes a Two-way Active
    Measurement Protocol, based on the One-way Active Measurement
    Protocol [OWAMP], that will accommodate two-way or round-trip
    measurements.
 
 
 Table of Contents
 
 
    1. Introduction..................................................2
    2. Terminology...................................................3
    3. Protocol Overview.............................................3
       3.1 Relationship of Test and Control Protocols................3
       3.2 Logical Model.............................................3
    4. TWAMP Control.................................................5
       4.1 Connection Setup..........................................6
       4.2 TWAMP Control Commands....................................6
       4.3 Creating Test Sessions....................................6
       4.4 Send Schedules............................................6
       4.5 Starting Test Sessions....................................6
       4.6 Stop-Sessions.............................................6
       4.7 Fetch-Session.............................................6
    5. TWAMP Test....................................................7
       5.1 Sender Behavior...........................................7
       5.2 Reflector Behavior........................................8
    6. Implementers Guide...........................................12
       6.1 Complete TWAMP...........................................12
       6.2 TWAMP Light..............................................12
    7. Security Considerations......................................13
    8. IANA Considerations..........................................13
    9. References...................................................13
       9.1 Normative References.....................................14
 
 
 1. Introduction
 
 
    The IETF IP Performance Metrics (IPPM) working group has proposed
    the draft standard for round-trip delay [RFC2681] metric.  IPPM has
    also proposed a new protocol for establishment of sessions for
    measurement of one-way metrics [OWAMP].  Two-way Active Measurement
    Protocol uses the methodology and architecture of OWAMP [OWAMP] to
 
 
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    define an open protocol for measurement of two-way or round-trip
    metrics.  Henceforth in this document the term two-way also
    signifies round-trip.
 
 
 2. Terminology
 
 
    In this document, the key words "MUST", "MUST NOT", "REQUIRED",
    "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
    and "OPTIONAL" are to be interpreted as described in RFC 2119
    [RFC2681] and indicate requirement levels for compliant
    implementations.
 
 
 3. Protocol Overview
 
 
    The Two-way Active Measurement Protocol is an open protocol for
    measurement of two-way metrics.  It is based on OWAMP [OWAMP] and
    adheres to its overall architecture and design.  The protocol
    defined in this document defines extensions and changes to OWAMP
    [OWAMP] as follows:
 
    -  Define a new logical entity, Session-Reflector, in place of the
        Session-Receiver.
 
    -  Define the Session-Reflector behavior in place of the
        Session-Receiver behavior of OWAMP [OWAMP].
 
    -  Define a new test packet format for packets transmitted from the
        Session-Reflector to Session-Sender.
 
    -  Presence of the Fetch client in the system and the support of
        the Fetch command by the Server are optional.
 
 
 3.1 Relationship of Test and Control Protocols
 
 
    Similar to OWAMP [OWAMP], TWAMP consists of two inter-related
    protocols: TWAMP-Control and TWAMP-Test.  The relationship of these
    protocols is as defined in section 1.1 of OWAMP [OWAMP].
 
 
 3.2 Logical Model
 
 
 
 
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    The role and definition of the logical entities are as defined in
    section 1.2 of OWAMP [OWAMP] with the following exceptions:
 
    -  Session-Receiver is called the Session-Reflector in the TWAMP
        architecture.
 
    -  The presence of the Fetch-Client is optional since two-way
        measurements do not require data retrieval from the
        Session-Reflector.  Consequently the support for the Fetch
        command is optional by the Server.  However, the Server may
        choose to implement the Fetch-Client and support the
        Fetch-Command to enable both one-way and two-way measurements
        in the same session.  This is explained in more detail in
        section 4.7.
 
    Several examples of possible relationship scenarios between these
    roles are presented below.  In the first example different logical
    roles are played on different hosts.
 
           +----------------+               +-------------------+
           | Session-Sender |<-TWAMP-Test-->| Session-Reflector |
           +----------------+               +-------------------+
             ^                                     ^
             |                                     |
             |                                     |
             |                                     |
             |  +----------------+<----------------+
             |  |     Server     |<-------+
             |  +----------------+        |
             |    ^                       |
             |    |                       |
             | TWAMP-Control         TWAMP-Control
             |    |                       |
             v    v                       v
           +----------------+     +-----------------+
           | Control-Client |     |   Fetch-Client  |
           +----------------+     +-----------------+
 
 
 
 
 
 
 
 
 
 
 
 
 
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    Second example is similar to the first example without the
    Fetch-Client.  In this example only two-way metrics are collected.
 
 
           +----------------+                +-------------------+
           | Session-Sender |<--TWAMP-Test-->| Session-Reflector |
           +----------------+                +-------------------+
             ^                                      ^
             |                                      |
             |                                      |
             |                                      |
             |  +----------------+                  |
             |  |     Server     |<-----------------+
             |  +----------------+
             |       ^
             |       |
             |   TWAMP-Control
             |       |
             v       V
           +----------------+
           | Control-Client |
           +----------------+
 
    Similar to OWAMP [OWAMP] different logical roles can be played by
    the same host.  For example, in the figure above, there could be
    actually two hosts: one playing the role of Control-Client,
    Fetch-Client, Session-Sender, and Server, and the other playing the
    role of  Session-Reflector.  This is the third example shown below.
 
 
           +-----------------+                   +-------------------+
           |     Server      |<------------------|                   |
           | Control-Client  |                   | Session-Reflector |
           | Session-Sender  |<--TWAMP-Test----->|                   |
           +-----------------+                   +-------------------+
 
 
    Additionally, following the guidelines of OWAMP [OWAMP], TWAMP has
    been defined to allow for small test packets that would fit inside
    the payload of a single ATM cell (only in unauthenticated mode).
 
 
 4. TWAMP Control
 
 
    All TWAMP Control messages are similar in format to and follow the
    same guidelines defined in section 3 of OWAMP [OWAMP].
 
 
 
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 4.1 Connection Setup
 
 
    Connection establishment of TWAMP follows the same procedure
    defined in section 3.1 of OWAMP [OWAMP].
 
 
 4.2 TWAMP Control Commands
 
 
    TWAMP control commands are as defined in section 3.3 of OWAMP
    [OWAMP] except for the optional requirement of the Fetch-Session
    command.
 
 
 4.3 Creating Test Sessions
 
 
    Test sessions creation follows the same procedure as defined in
    section 3.4 of OWAMP [OWAMP].  In order to distinguish the session
    as a two-way versus a one-way measurement session the first octet
    of the Request-Session command MUST be set to 5.  Value of 5
    indicates that this is a Request-Session for a two-way metrics
    measurement session.
 
 
 4.4 Send Schedules
 
 
    Send schedule of test packets follow the same procedure and
    guidelines as defined in section 3.5 of OWAMP [OWAMP].
 
 
 4.5 Starting Test Sessions
 
 
    Starting test sessions follow the same procedure and guidelines as
    defined in section 3.6 of OWAMP [OWAMP].
 
 
 4.6 Stop-Sessions
 
 
    Stopping test sessions follow the same procedure and guidelines as
    defined in section 3.7 of OWAMP [OWAMP].
 
 
 4.7 Fetch-Session
 
 
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    The purpose of TWAMP is measurement of two-way metrics.  Two-way
    measurements do not rely on packet level data collected by the
    Session-Reflector such as sequence number, timestamp, and TTL.   As
    such the protocol does not require the retrieval of packet level
    data from the Server and the Fetch-Session command is optionally
    supported by the Server.
 
    However, TWAMP can be used as an extension to OWAMP [OWAMP] where
    both one-way and two-way measurements are measured in the same
    session.  In this case the Server MAY support the Fetch-Session
    command as defined in section 3.8 of OWAMP[OWAMP].  The
    Session-Reflector will reject the Fetch-Session request if either
    it does not support the Fetch-Session command or Session-Reflector
    cannot provide the required data.  In this case the server MUST
    respond with a Fetch-Ack message with Accept value of 3.
 
 
 5. TWAMP Test
 
 
    The TWAMP test protocol is similar to the OWAMP [OWAMP] test
    protocol with the exception that the Session-Reflector transmits
    test packets to the Session-Sender in response to each test packet
    it receives.  TWAMP defines two different test packet formats, one
    for packets transmitted by the Session-Sender and one for packets
    transmitted by the Session-Reflector.  As with OWAMP [OWAMP] test
    protocol there are three modes: unauthenticated, authenticated, and
    encrypted.
 
 
 5.1 Sender Behavior
 
 
    The sender behavior is as defined in section 4.1 of OWAMP [OWAMP]
    for both packet timing and packet format.  Additionally the
    Session-Sender records the necessary information provided by the
    packets transmitted by the Session-Reflector for measuring two-way
    metrics.  The information recording based on the received packet by
    the Session-Sender is implementation dependent.
 
 
 5.1.1 Packet Timings
 
 
    Packet timings follow the same procedure and guidelines as defined
    in section 4.1.1 of OWAMP [OWAMP].
 
 
 
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 5.1.2 Packet Format and Content
 
 
    Session-Sender packet format and content follow the same procedure
    and guidelines as defined in section 4.1.2 of OWAMP [OWAMP].
 
 
 5.2 Reflector Behavior
 
 
    When receiving packets the reflector behavior is same as
    Session-Receiver behavior defined in section 4.2 of OWAMP [OWAMP]
    with the exception of optional packet information recording.  If
    the Session-Reflector chooses not to collect packet information for
    packets received from the Session-Sender, the Server will not
    support the Fetch-Session command.  Additionally, TWAMP requires
    the Session-Reflector to transmit a packet to the Session-Sender in
    response to each packet it receives.
 
    As packets are received the Session-Reflector will,
 
    -  Timestamp the received packet.
 
    -  In authenticated or encrypted mode, decrypt the first block (16
        octets) of the packet body.
 
    -  Copy the packet sequence number into the corresponding reflected
        packet to the Session-Sender.
 
    -  Optionally store the packet sequence number, send time, receive
        time, and the TTL for IPv4 (or Hop Limit for IPv6) from the
        packet IP header for the results to be transferred.
 
    -  Packets not received within the Timeout are considered lost.
        They are optionally recorded with their true sequence number,
        presumed send time, receive time consisting of a string of zero
        bits, and TTL (or Hop Limit) of 255.  The Session-Reflector
        will not generate a test packet to the Session-Sender for
        packets that are considered lost.
 
    -  Transmit a test packet to the Session-Sender in response to
        every received packet.  The response must be generated as
        immediately as possible.  The format and content of the test
        packet is defined in section 5.2.1.  Prior to the transmission
        of the test packet Session-Reflector MUST determine the elapsed
        time since the reception of the packet for incorporating the
        value in the reflected test packet.
 
 
 
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 5.2.1 Packet Format and Content
 
 
    The Session-Reflector MUST transmit a packet to the Session-Sender
    in response to each packet received.  The Session-Reflector SHOULD
    transmit the packets as immediately as possible.  The
    Session-Reflector SHOULD set the TTL in IPV4 (or Hop Limit in IPv6)
    in the UDP packet to 255.
 
    The test packet will have the necessary information for calculating
    two-way metrics by the Session-Sender.  The format of the test
    packet depends on the mode being used.  The format of the packet is
    presented below.
 
    For unauthenticated mode:
 
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Sequence Number                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Timestamp                            |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Error Estimate        |           MBZ                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Receive Timestamp                    |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Sender Sequence Number                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Sender Timestamp                         |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Sender Error Estimate    |           MBZ                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                         Packet Padding                        .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
 
 
 
 
 
 
 
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    For authenticated and encrypted modes:
 
    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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Sequence Number                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        IZP (12 octets)                        |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Timestamp                            |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |         Error Estimate        |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
    |                        IZP (6 octets)                         |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        Receive Timestamp                      |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        IZP (8 octets)                         |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
    |                        Sender Sequence Number                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                        IZP (12 octets)                        |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Sender Timestamp                         |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Sender Error Estimate    |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
    |                        IZP (6 octets)                         |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    .                                                               .
    .                         Packet Padding                        .
    .                                                               .
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
 
    Sequence Number is the sequence number of the test packet and
    starts with zero and is incremented by one for each subsequent
    packet.  The generated sequence number by the Session-Reflector,
 
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    Sequence Number, is independent from the sequence number of the
    received packets.
 
    Timestamp and Error Estimate are the transmit timestamp and error
    estimate of the test packet respectively.  Sender Timestamp and
    Sender Error Estimate are exact copies of the timestamp and error
    estimate from the Session-Sender test packet that corresponds to
    this test packet.  The format of all timestamp and error estimate
    fields follow the definition and formats defined by OWAMP[OWAMP].
 
    Receive Timestamp is the time the test packet was received by the
    reflector. The difference between Timestamp and Receive Timestamp
    is the amount of time the packet was in transition in the
    Session-Reflector.  The Error Estimate of Timestamp also applies to
    Receive Timestamp.
 
    Sender Sequence Number is the Sequence Number of the packet
    transmitted by the Session-Sender that corresponds to this test
    packet.
 
    Similar to OWAMP [OWAMP] the TWAMP packet layout is the same in
    authenticated and encrypted modes.  The encryption operation of
    Session-Receiver packet follow the same rules of Session-Sender
    packets as defined in OWAMP [OWAMP].
 
    The minimum data segment length is, therefore, 36 octets in
    unauthenticated mode, and 80 octets in both authenticated mode and
    encrypted modes.
 
    The Session-Reflector TWAMP-Test packet layout is the same in
    authenticated and encrypted modes.  The encryption operations are,
    however, different.  The difference is that in encrypted mode both
    the sequence numbers and timestamps are encrypted to provide
    maximum data integrity protection while in authenticated mode the
    sequence numbers are encrypted and the timestamps are sent in clear
    text.  Sending the timestamp in clear text in authenticated mode
    allows one to reduce the time between when a timestamp is obtained
    by a reflector and when the packet is reflected out.  In encrypted
    mode, both the sender and reflector have to fetch the timestamp,
    encrypt it, and send it; in authenticated mode, the middle step is
    removed, potentially improving accuracy (the sequence number can be
    encrypted before the timestamp is fetched).
 
    In authenticated mode, the first block (32 octets) of each packet
    is encrypted using AES Electronic Cookbook (ECB) mode.
 
    Obtaining the key, encryption method, and packet padding is as
    defined in section 4.1.2 of OWAMP [OWAMP].  In unauthenticated
    mode, no encryption is applied.
 
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 6. Implementers Guide
 
 
    This section serves as guidance to implementers of TWAMP.  Two
    architectures are presented in this section for implementations
    where two hosts play the subsystem roles of TWAMP.  Although only
    two architectures are presented here the protocol does not require
    their use.  Similar to OWAMP [OWAMP] TWAMP is designed with
    complete flexibility to allow different architectures that suite
    multiple system requirements.
 
 
 6.1 Complete TWAMP
 
 
    In this example the roles of Control-Client, Fetch-Client, and
    Session-Sender are implemented in one host referred to as the
    controller and the roles of Server and Session-Receiver are
    implemented in another host referred to as the responder.
 
 
               controller                              responder
           +-----------------+                   +-------------------+
           | Control-Client  |<--TWAMP-Control-->| Server            |
           | Fetch-Client    |                   |                   |
           | Session-Sender  |<--TWAMP-Test----->| Session-Reflector |
           +-----------------+                   +-------------------+
 
 
    This example provides an architecture that supports the full TWAMP
    standard.  The controller establishes the test session with the
    responder through the TWAMP-Control protocol.  After the session is
    established the controller transmits test packets to the responder.
    The responder follows the Session-Receiver behavior of both OWAMP
    [OWAMP] and TWAMP as described in section 5.2.  In this
    architecture the responder supports the Fetch-Session command.
    After the transmission of test packets the controller fetches the
    responder's information through its Fetch-Client.  This
    architecture allows for collection of both one-way and two-way
    metrics.
 
 
 6.2 TWAMP Light
 
 
    In this example the roles of Control-Client, Server, and
    Session-Sender are implemented in one host referred to as the
 
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    controller and the role of Session-Receiver is implemented in
    another host referred to as the responder.
 
 
               controller                              responder
           +-----------------+                   +-------------------+
           |     Server      |<----------------->|                   |
           | Control-Client  |                   | Session-Reflector |
           | Session-Sender  |<--TWAMP-Test----->|                   |
           +-----------------+                   +-------------------+
 
 
    This example provides a simple architecture for responders where
    their role will be to simply act as light test points in the
    network.  The controller establishes the test session with the
    Server through non-standard means.  After the session is
    established the controller transmits test packets to the responder.
    The responder follows the Session-Receiver behavior of TWAMP as
    described in section 5.2.1.  The controller receives the reflected
    test packets and collects two-way metrics. This architecture allows
    for collection of two-way metrics.
 
    This example eliminates the need for the TWAMP-Control protocol and
    assumes that the Session-Reflector is configured and communicates
    its configuration with the Server through non-standard means.
    Furthermore, the Server does not support the Fetch-Session command
    and the responder does not collect the received packet information.
    The Session-Reflector simply reflects the incoming packets back to
    the controller while copying the necessary information and
    generating sequence number and timestamp values per section 5.2.1.
 
 
 7. Security Considerations
 
 
    The security considerations of OWAMP [OWAMP] apply.
 
 
 8. IANA Considerations
 
 
    There are no IANA considerations associated with this
    specification.
 
 
 9. Acknowledgements
 
 
 
 
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    The authors wish to thank Sharee McNab and Nick Kinraid for their
    comments and suggestions.
 
 
 10. References
 
 
 10.1 Normative References
 
 
       [OWAMP]   Shalunov, S., Teitelbaum, B., Karp, A., Boote, J.,
                  Zekauskas, M., "A One-way Active Measurement Protocol
                  (OWAMP)", draft-ietf-ippm-owdp-11.txt, October 2004.
 
 
       [RFC2681] Almes, G., Kalidindi, S., Zekauskas, M., "A
                  Round-Trip Delay Metric for IPPM". RFC 2681, STD 1,
                  September 1999.
 
 
    Authors' Addresses
 
 
       Kaynam Hedayat
       Brix Networks
       285 Mill Road
       Chelmsford, MA  01824
       US
 
       Phone: +1 978 367 5611
       EMail: khedayat@brixnet.com
       URI:   http://www.brixnet.com/
 
 
       Roman M. Krzanowski, Ph.D.
       Verizon
       500 Westchester Ave.
       White Plains, NY
       US
 
       Phone: +1 914 644 2395
       EMail: roman.krzanowski@verizon.com
       URI:   http://www.verizon.com/
 
 
       Kiho Yum
       Juniper Networks
       1194 Mathilda Ave.
       Sunnyvale, CA
 
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       US
 
       Phone: +1 408 936 2272
       EMail: kyum@juniper.net
       URI:   http://www.juniper.com/
 
 
 IPR Disclosure Acknowledgement
 
 
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 Copyright Notice
 
 
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    Copyright (C) The Internet Society (2005).
 
    This document is subject to the rights, licenses and restrictions
    contained in BCP 78, and except as set forth therein, the authors
    retain all their rights.
 
 
 Acknowledgment
 
 
    Funding for the RFC Editor function is currently provided by the
    Internet Society.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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