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Versions: 00 01 02 draft-ietf-ippm-more-twamp

Network Working Group                                          A. Morton
Internet-Draft                                                 AT&T Labs
Intended status: Standards Track                              K. Hedayat
Expires: January 14, 2009                                  Brix Networks
                                                           July 13, 2008


                        More Features for TWAMP
                    draft-morton-ippm-more-twamp-02

Status of this Memo

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Abstract

   The IETF is completing its work on TWAMP - the Two-Way Active
   Measurement Protocol.  This memo describes additional features for
   TWAMP, essentially the ability to use different security modes in the
   TWAMP-Control and TWAMP-Test protocols.

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.  Extended Connection Setup . . . . . . . . . . . . . . . . . 4
   4.  Extended TWAMP Test . . . . . . . . . . . . . . . . . . . . . . 5
     4.1.  Sender Behavior . . . . . . . . . . . . . . . . . . . . . . 5
       4.1.1.  Packet Timings  . . . . . . . . . . . . . . . . . . . . 5
       4.1.2.  Packet Format and Content . . . . . . . . . . . . . . . 5
     4.2.  Reflector Behavior  . . . . . . . . . . . . . . . . . . . . 6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Registry Specification  . . . . . . . . . . . . . . . . . . 6
     6.2.  Registry Management . . . . . . . . . . . . . . . . . . . . 6
     6.3.  Experimental Numbers  . . . . . . . . . . . . . . . . . . . 7
     6.4.  Initial Registry Contents . . . . . . . . . . . . . . . . . 7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9




























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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].  The TWAMP
   specification gathered wide review as it approached completion, and
   the by-products were several recommendations for new features in
   TWAMP.  There are a growing number TWAMP implementations at present,
   and wide-spread usage is expected.  There are even devices emerging
   that test implementations for protocol compliance.

   This memo describes additional features for TWAMP, such as the
   ability to use different security modes in the TWAMP-Control and
   TWAMP-Test protocols.

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


2.  Purpose and Scope

   The purpose of this memo is to specify additional functions and
   features for TWAMP [I-D.ietf-ippm-twamp].  The features and
   extensions were vetted before adoption in this memo.

   The scope of the memo is limited to specifications of the following
   features:

   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 add the ability to use different
       security modes in the TWAMP-Control and TWAMP-Test protocols.
       The motivation for this extension is to permit the low packet
       rate TWAMP-Control protocol to utilize a stronger mode of
       integrity protection than that used in the TWAMP-Test protocol.

   (other items may be added)


3.  TWAMP Control Extensions

   TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,
   and provides two-way measurement capability.  All TWAMP Control
   messages are similar in format and follow similar guidelines to those
   defined in section 3 of [RFC4656] with the exceptions described in
   TWAMP [I-D.ietf-ippm-twamp], and in the following sections.




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   All OWAMP-Control messages apply to TWAMP-Control, except for the
   Fetch Session command.

3.1.  Extended Connection Setup

   TWAMP connection establishment follows the same procedure defined in
   section 3.1 of [RFC4656].  The extended modes assign three new bit
   positions (and values) to allow the Test protocol security mode to
   differ from the Control protocol mode.  With this extension, the
   complete set of TWAMP values are 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,  new bit position (3)
          Encrypted CONTROL

   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
   this extension to TWAMP, setting a higher mode field bit position (3)
   SHALL discontinue the inheritance of the security mode in the Test
   protocol, and each protocol's mode SHALL be specified explicitly.
   When the desired TWAMP Test protocol mode is identical to the Control
   Session mode, the corresponding mode bit (position 0, 1 or 2) SHALL
   be set.  The table below gives the various combinations that are now
   permissible in TWAMP, where the Test protocol may use one of the
   modes in each column corresponding to a Control mode.

   -------------------------------------------------------
   Protocol | Permissible Mode Combinations (mode bit set)
   -------------------------------------------------------
   Control  |    Unauth.(0)|  Auth.(1)|  Encrypted (2)
   -------------------------------------------------------
            |    Unauth.(0)|          |   Unauth.  (3)
            ----------------------------------------------
   Test     |              |  Auth.(1)|
            ----------------------------------------------
            |              |          |  Encrypted (2)
   -------------------------------------------------------

   Note that the TWAMP-Control protocol security measures are identical
   in the Authenticated and Encrypted Modes.  Therefore, only one new
   mode is needed to cover all mixed secuity modes that are possible.

   The value of the Modes field sent by the Server is the bit-wise OR of



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   the mode values that it is willing to support during this session.
   Thus, the last four bits of the Modes 32-bit field are used.  The
   first 28 bits MUST be zero.  A client conforming to this version of
   the specification MUST ignore the values in the first 28 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] 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-
   Test protocol there are three security modes: unauthenticated,
   authenticated, and encrypted.  The extension to TWAMP makes it
   possible to specify these modes independently from the mode used in
   the TWAMP-Control protocol.

4.1.  Sender Behavior

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

4.1.1.  Packet Timings

   The Send Schedule is not utilized in TWAMP, and there are no
   extensions defined 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],
   with the following exceptions:

   o  the Send Schedule is not used, and

   o  the support of additional security mode combinations defined in
      section 3.1 of this memo.







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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 extensions:

   o  the support of additional security mode combinations defined in
      section 3.1 of this memo.


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 three security mode combinations to the OWAMP-Control
   specification[RFC4656], and describes behavior when the new modes are
   used.  This memo requests creation an IANA registry for the TWAMP
   Mode field.  This field is a recognized extension mechanism for
   TWAMP.

6.1.  Registry Specification

   IANA is requested to create a TWAMP-Modes registry.  TWAMP-Modes are
   specified in TWAMP Server Greeting messages and Set-up Response
   messages 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.




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6.3.  Experimental Numbers

   No experimental values are currently assigned for the Modes Registry.

6.4.  Initial Registry Contents

   TWAMP Modes Registry

   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,  this document, Section 3.1
          Encrypted CONTROL


7.  Acknowledgements

   The authors would like to thank Len Ciavattone 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.

   [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.

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





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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/


   Kaynam Hedayat
   Brix Networks
   285 Mill Road
   Chelmsford, MA  01824
   USA

   Phone: +1
   Fax:   +1
   Email: khedayat@brixnet.com
   URI:   http://www.brixnet.com/






















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