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Versions: (draft-morton-ippm-more-twamp) 00 01 02 RFC 5618

Network Working Group                                          A. Morton
Internet-Draft                                                 AT&T Labs
Intended status: Standards Track                              K. Hedayat
Expires: April 22, 2009                                    Brix Networks
                                                        October 19, 2008


                        More Features for TWAMP
                     draft-ietf-ippm-more-twamp-00

Status of this Memo

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Abstract

   The IETF has completed its work on TWAMP - the Two-Way Active
   Measurement Protocol.  This memo describes a simple extension to
   TWAMP, the option 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 has completed its work on the core specification of TWAMP -
   the Two-Way Active Measurement Protocol [RFC5357].  TWAMP is an
   extension of 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 that are designed to test
   implementations for protocol compliance.

   This memo describes a simple extension for TWAMP, the option to use
   different security modes in the TWAMP-Control and TWAMP-Test
   protocols.

   The relationship between this memo and TWAMP is intended to be an
   update to [RFC5357] when published.


2.  Purpose and Scope

   The purpose of this memo is to describe and specify an extension for
   TWAMP [RFC5357].  The features and extensions were vetted before
   adoption in this memo.

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

   o  Extension of the modes of operation through assignment of one new
      value in the Mode field (see section 3.1 of [RFC4656]), while
      retaining backward compatibility with TWAMP [RFC5357]
      implementations.  This value adds the OPTIONAL 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.


3.  TWAMP Control Extensions

   TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,
   and coordinates a 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 [RFC5357], and in the following sections.

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



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3.1.  Extended Connection Setup

   TWAMP connection establishment follows the same procedure defined in
   section 3.1 of [RFC4656].  This extended mode assigns one new bit
   position (and value) to allow the Test protocol security mode to
   operate in Unauthenticated mode, while the Control protocol operates
   in Encrypted 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 Modes 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 Modes Field bit position 3 SHALL
   discontinue the inheritance of the security mode in the Test
   protocol, and each protocol's mode SHALL be as specified below.  When
   the desired TWAMP Test protocol mode is identical to the Control
   Session mode, the corresponding Modes Field bit (position 0, 1 or 2)
   SHALL be set.  The table below gives the various combinations of
   integrity protection that are permissible in TWAMP (with this
   extension).  The Test protocol SHALL use the mode in each column
   corresponding to the Modes Field bit position.

   --------------------------------------------------------
   Protocol | Permissible Mode Combinations (Modes bit set)
   --------------------------------------------------------
   Control  |    Unauth.(0)|  Auth. == Encrypted (1,2,3)
   --------------------------------------------------------
            |    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
   bit position (3) is needed to convey the single mixed security mode.

   The value of the Modes Field sent by the Server in the Server-
   Greeting message is the bit-wise OR of the modes (bit positions) that



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   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 extension of [RFC5357] MAY ignore
   the values in the first 28 bits of the Modes Field, or it MAY support
   other features that are communicated in these bit positions.

   Other ways in which TWAMP extends OWAMP are described in [RFC5357].


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 [RFC5357] 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.  This TWAMP extension makes it possible to use TWAMP-Test
   Unauthenticated mode regardless of the mode used in the TWAMP-Control
   protocol.

4.1.  Sender Behavior

   This section describes REQUIRED 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 MUST follow the same
   procedure and guidelines as defined in section 4.1.2 of [RFC4656] and
   section 4.1.2 of [RFC5357], with the following exceptions:

   o  the Send Schedule is not used, and

   o  the Sessions-Sender MUST support the mixed security mode
      (Unauthenticated TEST, Encrypted CONTROL,value 8, bit position 3)
      defined in section 3.1 of this memo.








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4.2.  Reflector Behavior

   The TWAMP Reflector is REQUIRED to follow the procedures and
   guidelines in section 4.2 of [RFC5357], with the following
   extensions:

   o  the Sessions-Reflector MUST support the mixed security mode
      (Unauthenticated TEST, Encrypted CONTROL,value 8, bit position 3)
      defined in section 3.1 of this memo.


5.  Security Considerations

   The extended mixed-mode of operation permits stronger security/
   integrity protection on the TWAMP-Control protocol while
   simultaneously emphasizing accuracy or efficiency on the TWAMP-Test
   protocol, thus making it possible to increase 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
   [RFC5357].


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 bit
   positions and corresponding values.

6.2.  Registry Management

   Because the TWAMP-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



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   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.  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

   [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.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, October 2008.



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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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