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INTERNET-DRAFT                                            R. Shekh-Yusef
Intended Status: Standards Track                                   Avaya
Expires: November 27, 2012                                     M. Barnes
                                                                 Polycom
                                                            May 26, 2012


                Conference Focus Indicating CCMP Support
                draft-yusef-dispatch-ccmp-indication-00

Abstract

   The Centralized Conferencing Manipulation Protocol document defines
   away for a client to discover a conference control server that
   supports CCMP. However, it does not define a way for a client
   involved in a conference to determine if the conference focus
   supports CCMP. This information would allow a CCMP-enabled client
   that joins a conference using SIP to also register for the XCON
   conference event package and take advantage of CCMP operations on the
   conference.

   This draft describes few options to address the above limitation with
   the pros and cons for each approach.



Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Internet-Drafts.

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   http://www.ietf.org/shadow.html





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Copyright and License Notice

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   described in the Simplified BSD License.





































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Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  4
   2  Possible Solutions  . . . . . . . . . . . . . . . . . . . . . .  5
     2.1 Feature Tag  . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.2 OPTIONS  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.3 Conference Event Package . . . . . . . . . . . . . . . . . .  6
       2.3.1 Service URI purpose  . . . . . . . . . . . . . . . . . .  6
       2.3.2 Conference URI purpose . . . . . . . . . . . . . . . . .  6
   3  Security Considerations . . . . . . . . . . . . . . . . . . . .  7
   4  Recommendation  . . . . . . . . . . . . . . . . . . . . . . . .  7
   5  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  7
   6  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . .  7
   7  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     7.1  Normative References  . . . . . . . . . . . . . . . . . . .  8
     7.2  Informative References  . . . . . . . . . . . . . . . . . .  8
   Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9

































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1  Introduction

   RFC 5239 defines a framework for Centralized Conferencing, which
   allows participants to exchange media in a centralized unicast
   conference. The framework also outlines a set of conferencing
   protocols for building advanced conferencing applications.

   The Centralized Conferencing Manipulation Protocol (CCMP) allows
   authenticated and authorized users to create, manipulate and delete
   conference objects.  Operations on conferences include adding and
   removing participants, changing their roles, as well as adding and
   removing media streams and associated end points.

   The Centralized Conferencing Manipulation Protocol (CCMP) draft
   defines a way for a client to determine a conference control server
   that supports CCMP, but it does not define a way for a client to
   determine if a conference focus supports CCMP.

   This draft describes few options to address the above limitation with
   the pros and cons for each approach.


1.1  Terminology

   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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2  Possible Solutions


2.1 Feature Tag

   This approach defines a feature parameter 'ccmp' to express that a
   SIP dialog belongs to a conference that supports CCMP.  The use of
   feature parameters in Contact header fields to describe the
   characteristics and capabilities of a UA is described in the User
   Agent Capabilities document.

   The focus behavior regarding the handling of the 'ccmp' feature is
   the same as the handling of the 'isfocus' feature parameter. In
   session establishment, a focus MUST include the 'ccmp' feature
   parameter in the Contact header field unless the focus wishes to hide
   the fact that it is a focus.

   The pros of this approach is a one step discovery of the focus and
   its ccmp support, and the fact that it can be used in response to an
   OPTIONS request, and that it enables the discovery of the ccmp
   capability by any network element that does not need the conference
   event package. The cons is the definition of a new feature parameter.



2.2 OPTIONS

   This approach requires the client to send an OPTIONS request to the
   conference focus to determine if the conference supports CCMP.

   If the feature tag approach is used, then the 200 OK response to the
   OPTIONS request MUST include the ccmp feature parameter in the
   Contact header.

   Another option is to return the Call-Info header with an XCON-URI in
   the 200 OK .

   The pros of this approach is that it is consistent with SIP in terms
   of the mechanism by which a UA determines the capabilities of a SIP
   intermediary, and that it enables the discovery of the ccmp
   capability by any network element that does not need the conference
   event package. The cons is that it requires an extra step to
   determine that a conference focus supports CCMP.








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2.3 Conference Event Package

   There are two options that rely on the SIP conference event package
   defined in RFC 4575:


2.3.1 Service URI purpose

   Define an additional URI 'purpose' of 'ccmp' associated with a
   'service-uris' element in the SIP conferencing event package.  The
   XCON-URI for the conference is included in the 'uri' element, per the
   following example:

      <service-uris>
        <entry>
          <uri>XCON:conf1@example.com</uri>
          <purpose>ccmp</purpose>
        </entry>
      </service-uris>


2.3.2 Conference URI purpose

   Define an additional URI 'purpose' of 'ccmp' associated with a
   'confs-uris' element in the SIP conferencing event package.

   ccmp: Indicates that the conference focus represented by this URI
   supports ccmp, which allows a client to use the CCMP protocol to
   manipulate the conference. This URI MUST be an XCON-URI as defined in
   the xcon-data-model.



      <conf-uris>
        <entry>
          <uri>XCON:conf1@example.com</uri>
          <display-text>whatever</display-text>
          <purpose>ccmp</purpose>
        </entry>
      </conf-uris>

   The pro of the SIP conference event package options is the use of an
   existing mechanism for extending the <purpose> field of the <service-
   uris> or <conf-uris> elements. The con is the requirement that the
   client register for the conference event package.  However, given
   that clients that want to take advantage of CCMP would most likely
   register for the conference event packages.




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3  Security Considerations

   These proposals introduce no additional security considerations
   beyond those which are applicable to each of the mechanisms described
   herein.


4  Recommendation

   This document recommends two mechanisms:

      * Call-Info that can be used with INVITE requests and responses,
        and responses to OPTIONS requests.
      * <service-uris> because it is typically used for ancillary or
        meta-information about the conference.

   This recommendation allows UAs that are interested in subscribing to
   the conference event package to discover the CCMP capabilities
   without any extra steps, while it allows UAs that are not interested
   in subscribing to the conference event package to discover if a
   conference focus supports CCMP without forcing them to subscribe to
   the conference event package.



5  IANA Considerations

   <IANA considerations text>



6  Acknowledgments

   The authors would like to thank Alan Johnston and Robert Sparks for
   their careful review and feedback.

   Special thanks to Adam Roach for his thorough review, comments, and
   suggestions.













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7  References

7.1  Normative References

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

   [RFC3261]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
               A., Peterson, J., Sparks, R., Handley, M., and E.
               Schooler, "SIP: Session Initiation Protocol", RFC 3261,
               June 2002.

   [RFC5239]   Barnes, M., Boulton, C., and O. Levin, "A Framework for
               Centralized Conferencing", RFC 5239, June 2008.

   [RFC4575]   Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session
               Initiation Protocol (SIP) Event Package for Conference
               State", RFC 4575, August 2006.

   [RFC6503]   Barnes M., Boulton, C., Romano S P., and Schulzrinne H.,
               "Centralized Conferencing Manipulation Protocol",
               RFC6503, March 2012.


7.2  Informative References


























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Author's Addresses


   Rifaat Shekh-Yusef
   Avaya
   250 Sidney Street
   Belleville, Ontario
   Canada

   Phone: +1-613-967-5267
   Email: rifatyu@avaya.com



   Mary Barnes
   Polycom
   TX
   US

   Email: mary.ietf.barnes@gmail.com































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