Network Working Group                                          A. Morton
Internet-Draft                                             L. Ciavattone
Intended status: Standards Track                               AT&T Labs
Expires: January 7, 2009                                    July 6, 2008


                     TWAMP Reflect Padding Feature
               draft-morton-ippm-twamp-reflect-padding-00

Status of this Memo

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   This Internet-Draft will expire on January 7, 2009.

Abstract

   The IETF is completing its work on TWAMP - the Two-Way Active
   Measurement Protocol.  This memo describes a proposed feature for
   TWAMP, intended for discussion in the IP Performance Metrics WG.  The
   feature gives the reflector the ability to return some of the packet
   padding bits to the sender.

Requirements Language

   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 RFC 2119 [RFC2119].




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Purpose and Scope  . . . . . . . . . . . . . . . . . . . . . .  3
   3.  TWAMP Control Extensions . . . . . . . . . . . . . . . . . . .  3
     3.1.  Connection Setup with Reflect Padding Feature  . . . . . .  4
     3.2.  Request-TW-Session Packet Format . . . . . . . . . . . . .  5
     3.3.  Accept Session Packet Format . . . . . . . . . . . . . . .  5
     3.4.  Additional considerations  . . . . . . . . . . . . . . . .  6
   4.  Extended TWAMP Test  . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Sender Behavior  . . . . . . . . . . . . . . . . . . . . .  7
       4.1.1.  Packet Timings . . . . . . . . . . . . . . . . . . . .  7
       4.1.2.  Packet Format and Content  . . . . . . . . . . . . . .  7
     4.2.  Reflector Behavior . . . . . . . . . . . . . . . . . . . .  8
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  Registry Specification . . . . . . . . . . . . . . . . . .  9
     6.2.  Registry Management  . . . . . . . . . . . . . . . . . . .  9
     6.3.  Experimental Numbers . . . . . . . . . . . . . . . . . . .  9
     6.4.  Registry Contents  . . . . . . . . . . . . . . . . . . . .  9
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
   Intellectual Property and Copyright Statements . . . . . . . . . . 12

























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1.  Introduction

   The IETF is completing its work on TWAMP - the Two-Way Active
   Measurement Protocol [I-D.ietf-ippm-twamp], which is an extension to
   the One-way Active Measurement Protocol, OWAMP [RFC4656].

   This memo describes a new proposed feature for TWAMP, so it can be
   discussed and interest to take-up the feature assessed.  This feature
   adds the capability for the Session-Reflector to return a limited
   number of unassigned (padding) bits to the Server/Session-Sender.
   With this capability, the Control-Client/Session-Sender can
   information it deems useful and have the assurance that the
   corresponding test packet will contain the information when it is
   returned.

   The relationship between this memo and TWAMP is intended to be an
   update to the TWAMP RFC when published.


2.  Purpose and Scope

   The purpose of this memo is to describe an additional function and
   feature for TWAMP [I-D.ietf-ippm-twamp].  The feature needs a clear
   description so it can be discussed and (hopefully) adopted in the IP
   Performance Metrics Charter.

   The scope of the memo is currently limited to specifications of the
   following feature:

   1.  Extension of the modes of operation through assignment of new
       values in the Mode field (see section 3.1 of [RFC4656]), while
       retaining backward compatibility with TWAMP [I-D.ietf-ippm-twamp]
       implementations.  These values identify the ability of the
       Server/Session-Reflector to reflect specific octets of Packet
       Padding back to the Client/Sender.  The motivation for this
       extension is to permit the Sender to tag packets with a index for
       simplified identification, or other uses.

   (other items may be added)

   When new features are discussed and reach consensus, they may become
   chartered work items in IETF IPPM (and may appear in a different
   memo).


3.  TWAMP Control Extensions

   TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,



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   and provides two-way measurement capability.  TWAMP
   [I-D.ietf-ippm-twamp] uses the Mode field to identify and select
   specific communication capabilities, and this field is a recognized
   extension mechanism.  The following sections describe one such
   extension.

3.1.  Connection Setup with Reflect Padding Feature

   TWAMP connection establishment follows the procedure defined in
   section 3.1 of [RFC4656].  The Reflect Padding feature requires two
   new bit positions (and values) to identify the ability of the Server/
   Session-Reflector to reflect specific octets of Packet Padding back
   to the Client/Sender.  With this added feature, the complete set of
   TWAMP mode values would be as follows:

   Value  Description             Reference/Explanation
   0      Reserved
   1      Unauthenticated         RFC4656, Section 3.1
   2      Authenticated           RFC4656, Section 3.1
   4      Encrypted               RFC4656, Section 3.1
   8      Unauth. TEST protocol,  draft-...-more-twamp (3)
          Auth. CONTROL
   16     Unauth. TEST protocol,  draft-...-more-twamp (4)
          Encrypted CONTROL
   32     Auth. TEST protocol,    draft-...-more-twamp (5)
          Encrypted CONTROL
   --------------------------------------------------------
   xx     Reflect Padding         new bit position (X)
          Capability
   yyy    Reflect & Operate       new bit position (Y)
          on Padding Bits


   In the original OWAMP mode field, setting bit positions 0, 1 or 2
   indicated the security mode of the Control protocol, and the Test
   protocol inherited the same mode (see section 4 of [RFC4656]).  In
   the [I-D.morton-ippm-more-twamp] bit positions (3, 4 or 5)
   discontinue the inheritance of the security mode in the Test
   protocol.

   The Server sets one or both of the new bit positions (possibly 6
   and/or 7) in the Server Greeting message to indicate its capabilities
   and willingness to operate in these modes if desired.

   If the Control-Client intends to operate all test sessions under this
   control connection using one of the new modes, it MUST set one of
   mode bits corresponding to that mode in the Setup Response message.




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3.2.  Request-TW-Session Packet Format

   The bits designated for the Reflect Padding feature in the Request-
   TW-Session command are as shown in the packet format 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      5        |  MBZ  | IPVN  |  Conf-Sender  | Conf-Receiver |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Number of Schedule Slots                     |
   .
   .               ... Many fields not shown ...
   .
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Type-P Descriptor                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Padding (to be reflected)   |     MBZ (2 octets)            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       MBZ (4 octets)                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       HMAC (16 octets)                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The "Packet Padding (to be reflected)" field SHALL be 2 octets long,
   as shown.

3.3.  Accept Session Packet Format

   The bits designated for the Reflect Padding feature in the Accept
   Session command are as shown in the packet format below.
















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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Accept     |      MBZ      |            Port               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
   |                                                               |
   |                        SID (16 octets)                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Padding (to be reflected)   |     MBZ (2 octets)            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       MBZ (8 octets)                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                       HMAC (16 octets)                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The "Packet Padding (to be reflected)" field SHALL be 2 octets long,
   as shown.

3.4.  Additional considerations

   The value of the Modes field sent by the Server (in the Server
   Greeting message) is the bit-wise OR of the mode values that it is
   willing to support during this session.

   If BOTH the above modes are adopted, the last eight bits of the Modes
   32-bit field are used.  The first 24 bits MUST be zero.  A client
   conforming to this version of the specification MUST ignore the
   values in the first 24 bits of the Modes value.  (This way, the bits
   are available for future protocol extensions.)

   Other ways in which TWAMP extends OWAMP are described in
   [I-D.ietf-ippm-twamp].


4.  Extended TWAMP Test

   The TWAMP test protocol is similar to the OWAMP [RFC4656] 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 [I-D.ietf-ippm-twamp] section 4 defines two
   additional test packet formats for packets transmitted by the



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   Session-Reflector.  The appropriate format depends on the security
   mode chosen.  This feature utilizes some of the bits within each test
   packet format.

4.1.  Sender Behavior

   This section describes extensions to the behavior of the TWAMP
   Session-Sender.

4.1.1.  Packet Timings

   The Send Schedule is not utilized in TWAMP, and this is unchanged in
   this memo.

4.1.2.  Packet Format and Content

   The Session-Sender packet format and content follow the same
   procedure and guidelines as defined in section 4.1.2 of [RFC4656] (as
   indicated in section 4.1.2 of TWAMP [I-D.ietf-ippm-twamp]).

   The Reflect Padding feature re-designates the packet padding field,
   as shown 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                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      MBZ      |       Length (2 oct)          |     Ext ID    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                  Packet Padding (to be reflected)             |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Additional Packet Padding                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The "Packet Padding (to be reflected)" field MAY be as long as 12
   octets, as shown.  IF the test packet length is truncated within this
   field, THEN ALL packet padding MUST be reflected by Session-
   Reflectors using this feature.





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4.2.  Reflector Behavior

   The TWAMP Reflector follows the procedures and guidelines in section
   4.2 of [I-D.ietf-ippm-twamp], with the following additional
   functions:

   o  bits in the packet padding field of the Session-Sender's test
      packet MUST be inserted in the Session-Reflector's test packet.

   The Reflect Padding feature re-designates the packet padding field,
   as shown 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                 |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Sender TTL   |       Length (2 oct)          |     Ext ID    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |               Packet Padding (from Session-Sender)            |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Additional Packet Padding                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The "Packet Padding (to be reflected)" field MAY be as long as 12
   octets, as shown.  IF the test packet length is truncated within this
   field, THEN ALL packet padding MUST be reflected by Session-
   Reflectors using this feature.






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5.  Security Considerations

   These extended modes of operation permit stronger integrity
   protection on the TWAMP-Control protocol while simultaneously
   emphasizing accuracy or efficiency on the TWAMP-Test protocol, thus
   enhancing overall security when compared to the previous options.

   The security considerations that apply to any active measurement of
   live networks are relevant here as well.  See [RFC4656] and
   [I-D.ietf-ippm-twamp].


6.  IANA Considerations

   This memo adds two mode combinations to the IANA registry for the
   TWAMP Mode field, and describes behavior when the new modes are used.
   This field is a recognized extension mechanism for TWAMP.

6.1.  Registry Specification

   IANA has created a TWAMP-Modes registry (as requested in
   [I-D.morton-ippm-more-twamp]).  TWAMP-Modes are specified in TWAMP
   Server Greeting messages and Set-up Response messages, as described
   in section 3.1 of [I-D.ietf-ippm-twamp], consistent with section 3.1
   of [RFC4656], and extended by this memo.  Modes are indicated by
   setting bits in the 32-bit Modes field.  Thus, this registry can
   contain a total of 32 possible values.

6.2.  Registry Management

   Because the Modes registry can contain only thirty-two values, and
   because TWAMP is an IETF protocol, this registry must be updated only
   by "IETF Consensus" as specified in [RFC2434](an RFC documenting
   registry use that is approved by the IESG).  For the Modes registry,
   we expect that new features will be assigned using monotonically
   increasing bit positions and in the range [0-31] and the
   corresponding values, unless there is a good reason to do otherwise.

6.3.  Experimental Numbers

   No experimental values are currently assigned for the Modes Registry.

6.4.  Registry Contents

   TWAMP Modes Registry is recommended to be augmented as follows:






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   Value  Description             Semantics Definition
   0      Reserved

   1      Unauthenticated         RFC4656, Section 3.1

   2      Authenticated           RFC4656, Section 3.1

   4      Encrypted               RFC4656, Section 3.1

   8      Unauth. TEST protocol,  draft-...-more-twamp (3)
          Auth. CONTROL
   16     Unauth. TEST protocol,  draft-...-more-twamp (4)
          Encrypted CONTROL
   32     Auth. TEST protocol,    draft-...-more-twamp (5)
          Encrypted CONTROL
   --------------------------------------------------------
   xx     Reflect Padding         this memo, section 3.1
          Capability              new bit position (X)
   yyy    Reflect & Operate       this memo, section 3.1
          on Padding Bits         new bit position (Y)


7.  Acknowledgements

   The authors would like to thank future readers for helpful review and
   comments.


8.  References

8.1.  Normative References

   [I-D.ietf-ippm-twamp]
              Babiarz, J., "A Two-way Active Measurement Protocol
              (TWAMP)", draft-ietf-ippm-twamp-08 (work in progress),
              June 2008.

   [I-D.morton-ippm-more-twamp]
              Morton, A. and K. Hedayat, "More Features for TWAMP",
              draft-morton-ippm-more-twamp-00 (work in progress),
              February 2008.

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

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.



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   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, September 2006.

8.2.  Informative References

   [x]        "".


Authors' Addresses

   Al Morton
   AT&T Labs
   200 Laurel Avenue South
   Middletown,, NJ  07748
   USA

   Phone: +1 732 420 1571
   Fax:   +1 732 368 1192
   Email: acmorton@att.com
   URI:   http://home.comcast.net/~acmacm/


   Len Ciavattone
   AT&T Labs
   200 Laurel Avenue South
   Middletown,, NJ  07748
   USA

   Phone: +1 732 420 1239
   Fax:
   Email: lencia@att.com
   URI:


















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