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XCON BOF                                                         R. Even
Internet-Draft                                                   Polycom
Expires: December 21, 2003                                      O. Levin
                                                               RADVISION
                                                               N. Ismail
                                                     Cisco Systems, Inc.
                                                           June 22, 2003


                Conferencing media policy  requirements
           draft-even-xcon-media-policy-requirements- 00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on December 21, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This document defines the  requirements for Media Policy, i.e.  a set
   of rules associated with the media distribution of the conference.
   This document presents the requirements for the media manipulations
   that can be done using these rules by conference participants or
   third parties using any kind of media/conference policy control
   protocol.  This document does not address the interface between the
   focus and the media policy.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Rational . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  High Level Architecture  . . . . . . . . . . . . . . . . . . .  3
   5.  Media Policy Data Model  . . . . . . . . . . . . . . . . . . .  5
   5.1 General  . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   6.  Media Policy Requirements  . . . . . . . . . . . . . . . . . .  6
   6.1 Genera Media Policy Requirements . . . . . . . . . . . . . . .  6
   6.2 Video specific requirements  . . . . . . . . . . . . . . . . .  7
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
       References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . .  8
       Intellectual Property and Copyright Statements . . . . . . . .  9




































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1. Introduction

   The Conferencing Framework [2] presents an overall framework and
   defines the terminology for SIP [1] tightly coupled conferencing.
   The conferencing framework architecture includes the media policy.
   This is a set of rules that describes the media distribution of a
   conference.  This document presents the requirements for the media
   policy data model and for the manipulations on these rules by
   conference participants or third parties using any kind of media/
   conference policy control protocol.  This document does not address
   the interface between the focus and the media policy and between the
   focus and the media mixer.

2. Rational

   The media policy enables a conference participant or an application
   server to define and manipulate the content of the media streams
   going to the conference participants.  This will enable applications
   like sidebars, announcement to specific participants, call centers
   and panel conferences.

3. Terminology

   The draft relies on the terminology defined in the conferencing
   framework document[2].

4. High Level Architecture

   The basic conferencing architecture used in this document is defined
   in the Conferencing architecture framework [2].  This document
   focuses on the media policy component and the requirements to
   manipulate the media policy by authorized entities.

   An authorized entity can manipulate the media policy using a supplied
   application.  Examples for such applications include a web
   application, an interactive voice response application, an
   interactive Instant Messaging (IM) base application, or an
   application that uses the media policy control protocol.

   The Conference policy control protocol (CPCP) provides a standard way
   for an automated authorized entity to manipulate the media policy.
   The requirements and definition of the CPCP protocol are out of scope
   of this document.

   The media policy is a set of rules that describes the media mixing or
   switching required for each participant in the conference.  This
   includes the set of sources to be mixed or switched and the rules for
   their mixing or switching.  The focus uses the media policy to



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   determine the proper configuration of the mixers.  Authorized
   entities will be notified of changes to the media policy by
   subscribing to the conference event package.  The information about
   the current contributing sources to the mixed streams can be learned
   by the information in the RTP header or by the conference event
   package [4].  The data structures that include the contributing
   sources of the current streams is in the focus or the mixer and is
   not in the scope of the work.

   The initial state of the media policy data structure is defined at
   the conference creation time.  It can be either provisioned or
   created by using a conference policy control protocol or/and other
   protocols being used to create the conference.

   Typically, a focus has access to the media policy and is responsible
   for translating the media policy data into the actions towards the
   physical entities ("mixers").

   Figure 1 describes an instance of media policy of a conference.  The
   figure shows a single mixer and a single type of stream for ease of
   drawing but the model does not have such a restriction.






























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                  Conference   .
                  Policy       . +-----------+        //-----\\    .
                  Control      . |           |      ||         ||  .
                  Protocol     . | Conference|        \\-----//    .
                  +------------->|  Policy   |       |         |   .
                  |            . |  Server   |---->  |Conference   .
                  |            . |           |       |    |   .
                  |            . +-----------+       |    &    |   .
                  |            .                     |         |   .
                  |            .                     | Media   |   .
        +------------+         . +-----------+       |   Policy|   .
       | +----------++         . |           |        \       //   .
        | |          ||        . |           |         \-----/     .
        |Participants||<-------->|   Focus   |            |        .
        | |          || SIP    . |           |            |        .
        | |          || Dialog . |           |<-----------+        .
       +-+----------++         . +-----------+                     .
          +-----------+        .      |                            .
           ^    |              .      |                            .
           |    | Contributing .      |                            .
           |    | Streams      . +-----------+                     .
           |    +------------->. |           |                     .
           | Distributed       . | Mixer     |                     .
           | Streams           . |           |                     .
           +-------------------. +-----------+                     .
                               .....................................

                                           Conference
                                            Functions

             Figure 1: Media Policy in a Conference



5. Media Policy Data Model

5.1 General

   The fundamental conferencing functionality is being able to combine
   (i.e.  "to mix") in a media specific manner participants' streams
   that belong to a logical sub-function within a conference (such as
   participant's video, left audio stream, right audio stream, video
   streaming presentation, slide presentation) and are of the same media
   type (such as video, audio, etc.).  In the case of using
   centralized-mixing the resultant stream(s) will be sent back to the
   participants.  In the case of end-point mixing, the original streams,
   needed to produce the mixed media, will be distributed to the
   participants that will perform the actual mixing.



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   Typically, the maximum number of different mixers in a conference is
   preconfigured as part of the media conference policy.  Mixers MAY be
   dynamically created and destroyed during the conference lifetime.
   This document will not describe the data model itself.

6. Media Policy Requirements

   All the requirements are based on having a privilege mechanism that
   authorizes users to access and manipulate the media policy data.  The
   requirements are for the manipulations that can be done on the media
   distrbution by the mixer using the CPCP protocol.  The protocol
   itself is not in the scope of this document.  Authorization is also
   part of CPCP.  The requirements are not for the mixer itself.

6.1 Genera Media Policy Requirements

   REQ-GP1: An authorized participant MUST be able to specify its own
   unique topology.

   REQ-GP2: It MUST be possible for a group of users to receive the same
   mix.  This mix may be a conference common mix.

   REQ-GP3:It MUST be possible, using the protocol,  to dynamically
   modify the number of contributing streams associated with a mixer.

   REQ-GP4: It MUST be possible, using the protocol, to define the
   mixing function for each participant in the conference.

   REQ-GP6: It SHOULD be possible to send a participant multiple streams
   from one mixer.  This requirement is to enable support for end- point
   mixing.

   REQ-GP7: It SHOULD be possible to define relationships between
   different mixers.  The relationships can be time synchronized such as
   specifying that the audio mixer and video mixer is a pair to
   establish lip-synchs.

   REQ-GP8: It SHOULD be possible to define the number of different
   topologies and the number of streams in each of them that will be
   mixed in a mixer.  For example the conference will support only one
   video topology that will go to all the participants, the video
   topology will support 2x2 display, or each participant will be able
   to receive his own audio topology that will include up to 4
   contributing sources.

   REQ-GP9: It SHOULD be possible to have more then one stream from the
   same type (video or audio) coming from the same user and to mix them
   separatly.  For example one video stream will be the video camera



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   showing the speakerwhile the other may be a presntation or a second
   camera showing the whole room.

6.2 Video specific requirements

   Video is a bit different than audio when mixing is concerned.  In
   multipoint video the common mixing modes are:

   Video switching where one of the contributing sources is sent to all
   participants, the video source may be forced by the media policy
   control protocol or may be dynamic by using for example a voice
   activated video switching mode where the participants will see the
   loudest speaker.

   "Continuous presence" or tiled windows display where the topology is
   composing one video stream that has a layout defining the shape and
   position of viewing windows that will be displayed to the
   participants.  The layout includes N viewing windows so that in each
   of the windows there is one contributing stream.  Even though the
   viewing windows can be of any shape we will address in this work only
   rectangular windows of any size.  The windows may overlap.

   The section defines the specific requirements for media policy and
   media policy control to enable "Continuous presence"

   REQ-V1: It should be possible to define rectangular overlapping
   windows in a video mix.

   REQ-V2: It should be possible to map a stream to a window based on
   some mode like having one window display the loudest speaker or the
   floor holder while for the remaining windows fixed input streams are
   used.

   REQ-V3: It should be possible for authorized participants to change
   the layout of the video topology.

   REQ-V4: It should be possible for authorized participants to define
   the mapping of a stream to a window.

7. Security Considerations

   The media policy control protocol may enables unauthorized users to
   manipulate the media mixing of conferences, this may enable them to
   listen to conference or eject unsolicited media streams.  The
   protocol should provide authentication of the users.  The media
   policy data may include information about the sources and targets of
   mixer, if this information will be transferred in the protocol in the
   clear that may cause a security risk.  The protocol should allow for



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   encryption of the media policy transferred in the media policy
   control protocol.

References

   [1]  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.

   [2]  Rosenberg, J., "A Framework  for Conferencing with the Session
        Initiation Protocol", draft-
        rosenberg-sipping-conferencing-framework-01 (work in progress),
        February 2003.

   [3]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
        Session Description Protocol (SDP)", RFC 3264, June 2002.

   [4]  Rosenberg, J. and H. Schulzrinne, "A  session initiation
        protocol (SIP) event package for conference state", , June 2002.


Authors' Addresses

   Roni Even
   Polycom
   94 Derech Em Hamoshavot
   Petach Tikva  49130
   Israel

   EMail: roni.even@polycom.co.il


   Orit Levin
   RADVISION
   266 Harristown Road
   Glen Rock
   NJ  USA

   EMail: orit@radvision.com


   Nermeen Ismail
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose  95134
   CA USA

   EMail: nismail@cisco.com



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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

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   Internet Society.











































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