XCON Working Group                                         S. Srinivasan
Internet-Draft                                     Microsoft Corporation
Intended status: Standards Track                                 R. Even
Expires: August 30, 2007                                         Polycom
                                                       February 26, 2007


       Conference event package extensions for the XCON framework
              draft-srinivasan-xcon-eventpkg-extensions-00

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document extends the notification mechanism defined in the
   conference event package [2] to suit the specific needs of the XCON
   framework [1] and the XCON data model [3].  The document registers a
   new MIME-subtype for this purpose.  Support for this new data format
   may be negotiated using Accept header semantics (as defined in RFC
   3261).




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Limitations of current data format for notifications
       defined in the conference event package  . . . . . . . . . . .  3
     2.1.  Partial updates for existing elements  . . . . . . . . . .  3
     2.2.  Re-definition of existing elements . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  4
   5.  Candidate elements (for partial updates) . . . . . . . . . . .  4
   6.  New MIME subtype definition  . . . . . . . . . . . . . . . . .  5
     6.1.  Partial Notification Mechanism: Updates to Section 4.4
           of [2] . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     6.2.  Element keys: Updates to Section 4.5 of [2]  . . . . . . .  5
   7.  Other approaches . . . . . . . . . . . . . . . . . . . . . . .  5
   8.  Conference-aware clients subscribing to conference state . . .  6
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
     10.1. application/xcon-conference-info+xml MIME Registration . .  6
     10.2. URN sub-namespace registration for
           'urn:ietf:params:xml:ns:xcon-conference-info'  . . . . . .  8
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     11.1. Normative References . . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9
   Intellectual Property and Copyright Statements . . . . . . . . . . 10


























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1.  Introduction

   The XCON centralized conferencing framework [1] describes a framework
   for XCON based conferencing.  It specifies the need for a
   notification mechanism to deliver conference state updates to
   conference-aware clients.  The purpose of this document is to fill
   that requirement and build upon the framework established in the
   conference event package [2].  For more information, refer [2] and
   [3].  The following section will describe the limitations of the
   current data format defined within the conference event package [2].


2.  Limitations of current data format for notifications defined in the
    conference event package

   [2] defines the MIME-type 'application/conference-info+xml' to be
   associated with the conference event package.  The following section
   discusses a few of the limitations in the data format defined in the
   conference event package [2].

2.1.  Partial updates for existing elements

   Section 4.4, 4.5 and 4.6 of [2] specify a mechanism to send partial
   updates of conference state information.  The algorithm (defined in
   Section 4.6 of [2]), however, prevents the partial notifications for
   non-atomic sub-elements for elements like 'available-media' (as
   defined in Section 5.3.4 of [2]) and 'media' XML element (as defined
   in Section 5.7.8 of [2]) as these elements do not contain a state
   attribute defined.

2.2.  Re-definition of existing elements

   Several elements defined in [2] have been re-defined or extended for
   the purposes of XCON and multi-protocol support.  Examples of such
   elements are 'conf-uris' element defined in Section 3.3.2 and
   'service-uris' defined in Section 3.3.3.


3.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in BCP 14, RFC 2119 [1] and indicate requirement levels for
   compliant implementations.






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4.  Requirements

   Listed here are some of the requirements for developing an XCON-based
   conference event package data format.

   REQ-1: It should satisfy all the notifications needs defined in the
   conferencing framework [1].

   REQ-2: The document should describe changes in behavior and describe
   how conference-aware clients implementing the conference event
   package [2] (and the data format defined therein) MAY work against
   the XCON defined extensions. [[ Note that this is a MAY.  However, as
   per Section 3.4 in [2] states, all subscribers and notifiers MUST
   support the "application/conference-info+xml" data format.]]

   REQ-3: The document should define any and all changes that break
   normative text defined in the SIP conference event package.

   REQ-4: It should enable partial updates of changes in specific
   element extensions defined in the XCON data model [3] such as
   controls and list elements. [[ During IETF-67, it was determined that
   there would be changes required in this area. ]]

   REQ-5: The data format for the notification is the XCON data model
   [3] (which is an extension to the conference event package [2] with
   certain elements being re-defined).

   REQ-6: A general notification mechanism for sending partial updates
   to any XML element (stretch goal). [[ Like partial pidf.  Should this
   be a concrete requirement? ]]


5.  Candidate elements (for partial updates)

   As defined earlier, the following list captures elements defined in
   [2] not supporting partial updates:

   1.  Conference information 'available-media' XML element defined in
   Section 5.3.4 of [2]

   2.  Endpoint 'media' XML element defined in Section 5.7.8 of [2]

   3.  Conference information 'conf-uris' and 'service-uris' defined in
   Section 5.3.1 and Section 5.3.2 respectively of [2]







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6.  New MIME subtype definition

   This document defines a new MIME subtype for subscribing to and
   notifying conference state information.  The new MIME-type
   'application/xcon-conference-info+xml' defines the new content type
   for supporting the XCON data model.  The XML schema (data format) is
   as defined in the XCON data model [3].  Implementations MUST follow
   all sections of [2] not related directly to the data model.  These
   include, but are not limited to, Section 3, Section 4 (see
   annotations below), Section 8 and Section 9.1.

   Note: This approach will require the XCON server to support both
   versions if there is a need for backward compatibility.  If there is
   lack of support for the MIME-type format defined in [2], then SIP
   clients (implementing [2]) will not be able to interwork with the
   XCON clients.

6.1.  Partial Notification Mechanism: Updates to Section 4.4 of [2]

   The only change here is to include additional elements for partial
   updates (TBD).  The following is a list of additional elements
   previously defined in [2] that are now permissible for partial
   updates using the data model defined in [3].

   o Element 'available-media'

   o Element 'media' as defined in Section 5.7.8 of [2]

6.2.  Element keys: Updates to Section 4.5 of [2]

   The only change here is to include the keys for the additional
   elements supporting partial updates.  [TODO: add definitions here]


7.  Other approaches

   [[ This section presents other approaches or solutions for
   information purposes only and will be removed from the final document
   once a decision has been made. ]]

   Alternate-1: Re-define elements that require partial updates that
   appear under available-media and media (as described in the previous
   section) in a separate section without breaking backward
   compatibility with [2].  Eliminate the re-defined elements and extend
   the base conference event package schema.  This eliminates the
   limitations described in the Limitations section above.  [[Note: This
   was discussed in an offline discussion and was not clean from a data
   model perspective. ]]



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   Alternate-2: Introduce a protocol version as a MIME parameter
   instead.  Note that this may not satisfy all requirements for
   protocol processing and backward compatibility.  The content type
   header may look like -- "application/conference-info+xml;version=2".
   Change the schema to include 'state' attribute in existing elements
   defined within the conference event package [2] that require partial
   updates.

   Alternate-3: Deprecate logic defined in the conference event package
   for partial updates (i.e. use of 'state' attributes is no longer
   required).  Use a PIDF-DIFF like (or better) system for partial
   conference state updates and eliminate re-defined elements to conform
   to [2].

   Alternate-4: Define a new event package.  The event header may look
   like -- "Event: xcon-conference".  Change the schema to include
   'state' attribute in existing elements defined within the conference
   event package [2] that require partial updates.


8.  Conference-aware clients subscribing to conference state

   Conference-aware clients implementing [2] SHOULD be able to subscribe
   to conference state information from the conferencing focus.  The
   conference focus thus SHOULD support both MIME-type's defined in [2]
   and this document.  [[Note: If Option-1, in the previous section,
   were to be chosen then this requirement goes away.]]


9.  Security Considerations

   TBD


10.  IANA Considerations

   TBD [[Note: This section only applies if Option-1a or Option-1b are
   chosen.]]

10.1.  application/xcon-conference-info+xml MIME Registration

   MIME media type name: application

   MIME subtype name: xcon-conference-info+xml

   Mandatory parameters: none

   Optional parameters: Same as charset parameter application/xml as



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   specified in RFC 3023 [rfc3023]

   Encoding considerations: Same as encoding considerations of
   application/xml as specified in RFC 3023 [rfc3023]

   Security considerations: See Section 10 of RFC 3023 [rfc3023] and
   Section 8 of this specification

   Interoperability considerations: none

   Published specification: This document

   Applications which use this media type: This document type has been
   used to support SIP conferencing applications that comply with the
   XCON data model [3]

   Additional Information:

   Magic Number: None

   File Extension: .xml

   Macintosh file type code: "TEXT"

   Personal and email address for further information: TBD

   Intended usage: COMMON

   Author/Change controller: TBD






















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10.2.  URN sub-namespace registration for
       'urn:ietf:params:xml:ns:xcon-conference-info'


         URI:
         urn:ietf:params:xml:ns:xcon-conference-info

         Description:
         This is the XML namespace for XML elements defined by
         [[[RFCXXXX]]] to describe the
         'application/xcon-conference-info+xml' content type for the
         XCON extensions defined for the conference event pacakge.

         Registrant Contact: TBD

         XML:
           BEGIN
            <?xml version="1.0"?>
            <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
            "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
            <html xmlns="http://www.w3.org/1999/xhtml
            <head>
                 <meta http-equiv="content-type"
                 content="text/html;charset=iso-8859-1"/>
                 <title>XCON conference event package extensions
                        for conference state</title>
            </head>
            <body>
                <h1>Namespace for XCON extensions for
                    conference state</h1>
                <h2>urn:ietf:params:xml:ns:xcon-conference-info</h2>
                <p>See <a href="[[[URL of published RFC]]]">
                RFCXXXX</a>.</p>
             </body>
             </html>
           END



11.  References











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11.1.  Normative References

    [1]  Barnes, M., "A Framework and Data Model for Centralized
         Conferencing", draft-ietf-xcon-framework-05 (work in progress),
         September 2006.

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

    [3]  Novo, O., Camarillo, G., Morgan, D., "A Common Conference
         Information Data Model for Centralized Conferencing  (XCON)",
         draft-ietf-xcon-common-data-model-03 (work in progress),
         October 2006.

    [4]  G. Camarillo, J. Holler, and H. Schulzrinne, "Grouping of Media
         Lines in the Session Description Protocol (SDP)", RFC 3388,
         December 2002.


Authors' Addresses

   Srivatsa Srinivasan
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052, USA

   Email: srivats@microsoft.com


   Roni Even
   Polycom
   94 Derech Em Hamoshavot
   Petach Tikva  49130, Israel

   Email: roni.even@polycom.co.il















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