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Versions: 00 01 02                                                      
INTERNET-DRAFT                                            R. Shekh-Yusef
Intended Status: Standards Track                                   Avaya
Expires: July 28, 2011                                         M. Barnes
                                                                 Polycom
                                                        January 24, 2011


                Conference Focus Indicating CCMP Support
                draft-yusef-xcon-ccmp-indication-00.txt

Abstract

   The Centralized Conferencing Manipulation Protocol document defines a
   way for a client to discover a conference control server that
   supports CCMP. However, it does not define a way for a client to
   discover if a conference focus supports CCMP.

   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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Copyright and License Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   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  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . . 7
   5  References . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
      5.1  Normative References  . . . . . . . . . . . . . . . . . . . 7
      5.2  Informative References  . . . . . . . . . . . . . . . . . . 7
   Author's Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8



































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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 discover a conference control server
   that supports CCMP, but it does not define a way for a client to
   discover 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. 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 discover 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 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. The cons is that it requires an extra step to discover
   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:  Accessing a URI with this purpose 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 proposal introduce no additional security considerations beyond
   those which are applicable to each of the mechanisms described
   herein.


4  IANA Considerations

   <IANA considerations text>


5  References

5.1  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.

   [CCMP]      Barnes M., Boulton, C., Romano S P., and Schulzrinne H.,
               "Centralized Conferencing Manipulation Protocol", Work in
               Progress, October 2010.


5.2  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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