XCON Working Group S. Srinivasan Internet-Draft Microsoft Corporation Intended status: Standards Track R. Even Expires: January 10, 2008 Polycom July 9, 2007 Conference event package data format extension for centralized conferencing draft-srinivasan-xcon-eventpkg-extensions-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 10, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document augments the notification mechanism defined in the Conference Event Package [2] to suit the specific needs of the Centralized Conferencing Framework [1] and the Data Model for Centralized Conferencing [3]. The document registers a new media subtype for this purpose. Support for this new data format may be negotiated using Accept header semantics as defined in the Session Srinivasan & Even Expires January 10, 2008 [Page 1] Internet-Draft xcon-eventpkg-extensions July 2007 Initilization Protocol (SIP). Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Partial notification limitations . . . . . . . . . . . . . . . 3 4. Goals for this document . . . . . . . . . . . . . . . . . . . . 4 5. Elements supporting partial updates . . . . . . . . . . . . . 4 5.1. Available-media . . . . . . . . . . . . . . . . . . . . . . 4 5.2. Media . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. New media type definition . . . . . . . . . . . . . . . . . . . 5 7. Client Considerations . . . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 9.1. application/xcon-conference-info+xml media type registration . . . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 10.1. Normative References . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 9 Srinivasan & Even Expires January 10, 2008 [Page 2] Internet-Draft xcon-eventpkg-extensions July 2007 1. Introduction The conferencing framework [1] describes a framework for centralized 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 for the data model defined for centralized conferencing and build upon the framework established in the conference event package [2]. 2. 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. 3. Partial notification limitations The media type 'application/conference-info+xml' is defined in the conference event package [2]. 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 those sections, however, prevents the partial notifications for non-atomic sub-elements of elements like 'available-media' (defined in Section 5.3.4 of [2]) and 'media' (defined in Section 5.7.8 of [2]) as these elements do not contain a state attribute defined. The data model for centralized conferencing [3] introduces the concept of controls for controling media. This is defined under 'available-media' for streams from the mixer and under 'media' for streams received from and sent to the mixer from conference participant's endpoints. A 'floor' element has also been defined under the 'media' element. These elements may frequently change their state over the course of a conference. The list of media could grow significantly large for large conferences. Furthermore, clients receiving updates of media often need to know which specific control changed when a notification as such is received. To overcome these limitations, a partial notification mechanism needs to be defined for these elements. Thus, state attributes and element keys (for the sub-elements) have been defined in the data model [3] for these elements. This, however, requires that a new media subtype be defined and registered as these elements have been explicitly marked as not having a state attribute in [2]. A conferencing system, implementing only [2], may not expect to receive these XML Srinivasan & Even Expires January 10, 2008 [Page 3] Internet-Draft xcon-eventpkg-extensions July 2007 elements with a state attribute of partial and thus this may result in inconsistent conferencing state. In-order to overcome this limitation this specification defines a new media subtype which can be used to enable partial notifications of elements previously defined without a state attribute. 4. Goals for this document Listed here are some of the goals for this document. (1) It should satisfy all the notifications needs defined in the conferencing framework [1] and the data model defined for centralized conferencing in [3]. (2) It should support partial updates of changes in elements defined in the data model for centralized conferencing [3] such as controls and list elements. Clients receiving partial notifications can determine the specific control that changed by examining the notification received. [[ During IETF-67, it was determined that there would be changes required in this area. ]] (3) The document should describe how conference-aware clients implementing the conference event package [2] (and the data format defined therein) will work against the centralized conferencing defined data format. [[ 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.]] 5. Elements supporting partial updates As specified 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] 5.1. Available-media With the introduction of the state attribute to available-media in [3], element keys are defined as follows for sub-elements. The sub-element 'entry' is defined with the attribute key 'label'. The non-atomic sub-elements under 'entry' are 'codecs' and Srinivasan & Even Expires January 10, 2008 [Page 4] Internet-Draft xcon-eventpkg-extensions July 2007 'controls'. There are no requirements to have 'codecs' support partial updates as these are expected to change rarely. The 'controls' element is defined with a state attribute as well. The sub-elements appearing under 'controls' do not require a key as each sub-element (like 'mute' or 'gain') appears only once and is atomic. That is, in a partial notification, the 'mute' element (and all sub-elements) should be included. 5.2. Media Similarly, the introduction of the state attribute to media requires element keys to be defined for its sub-elements. The 'endpoints' element (under which 'media' appears) has the state attribute defined and so do all its parent elements. The non-atomic sub-elements under 'media' are 'from-mixer' and 'to- mixer'. Both of which have the state attribute defined. The non- atomic sub-element appearing under both 'from-mixer' and 'to-mixer' is the 'controls' element. The 'floor' element is an atomic sub-element of 'from-mixer' or 'to- mixer' and thus does not require a state attribute. The 'controls' element is a non-atomic sub-element and thus has a 'state' attribute defined. The sub-elements appearing under 'controls', as defined in the previous section, do not require a key as each sub-element appears only once and is atomic. 6. New media type definition This document defines a new media type 'application/ xcon-conference-info+xml' for supporting the data model for centralized confeerncing for which the XML schema (data format) is defined in [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. 7. Client Considerations Conference-aware clients, implementing the conference event package [2], SHOULD be able to subscribe to conference state information from Srinivasan & Even Expires January 10, 2008 [Page 5] Internet-Draft xcon-eventpkg-extensions July 2007 the conferencing focus. The conference focus thus SHOULD support media types defined here as well as the one defined in the conference event package for backward compatibility. If there is lack of support for the media type format defined in conference event package, then clients not supporting it will not be able to interwork with the centralized conferencing clients implementing [3]. 8. Security Considerations TBD 9. IANA Considerations 9.1. application/xcon-conference-info+xml media type registration [[This section needs editing.]] To: ietf-types@iana.org Subject: Registration of media type application/ xcon-conference-info+xml Type name: application Subtype name: xcon-conference-info+xml Required parameters: none Optional parameters: Same as charset parameter application/xml as 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 data model for centralized conferencing [3] Additional Information: Srinivasan & Even Expires January 10, 2008 [Page 6] Internet-Draft xcon-eventpkg-extensions July 2007 Magic Number(s): None File Extension(s): .xml Macintosh file type code(s): "TEXT" Personal and email address for further information: TBD Intended usage: COMMON Author: Change controller: TBD 10. References 10.1. 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., Even, R., "A Common Conference Information Data Model for Centralized Conferencing (XCON)", draft-ietf-xcon-common-data-model-05 (work in progress), October 2007. Authors' Addresses Srivatsa Srinivasan Microsoft Corporation One Microsoft Way Redmond, WA 98052, USA Email: srivats@microsoft.com Srinivasan & Even Expires January 10, 2008 [Page 7] Internet-Draft xcon-eventpkg-extensions July 2007 Roni Even Polycom 94 Derech Em Hamoshavot Petach Tikva 49130, Israel Email: roni.even@polycom.co.il Srinivasan & Even Expires January 10, 2008 [Page 8] Internet-Draft xcon-eventpkg-extensions July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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