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


                         Conferencing Scenarios
              draft-even-xcon-conference-scenarios- 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.

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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 describes SIP conferencing scenarios.  It will describe
   basic and advance conferencing scenarios.  These conferencing
   scenarios will help with definition and evaluation of the
   requirements for SIP conferencing framework.









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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Simple Conferencing scenarios  . . . . . . . . . . . . . . . .  3
   2.1 Ad-hoc conference  . . . . . . . . . . . . . . . . . . . . . .  3
   2.2 Extension of a Point to point calls to a multipoint call . . .  4
   2.3 Reserved conference  . . . . . . . . . . . . . . . . . . . . .  4
   3.  Advance Conferencing scenarios . . . . . . . . . . . . . . . .  4
   3.1 Extending a point-to-point call to a multipoint call . . . . .  4
   3.2 Lecture mode conferences . . . . . . . . . . . . . . . . . . .  5
   3.3 Conference with non-SIP members  . . . . . . . . . . . . . . .  5
   3.4 A reserved or ad-hoc conference with conference aware
       members. . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.5 Advanced conference features . . . . . . . . . . . . . . . . .  5
   4.  Scenarios for media policy control . . . . . . . . . . . . . .  7
   4.1 Video mixing scenarios . . . . . . . . . . . . . . . . . . . .  7
   4.2 Typical video conferencing scenario  . . . . . . . . . . . . .  8
   4.3 Conference Sidebar scenario  . . . . . . . . . . . . . . . . .  9
   4.4 Coaching scenario  . . . . . . . . . . . . . . . . . . . . . .  9
   4.5 Presentation and QA session  . . . . . . . . . . . . . . . . . 10
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
       References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11
       Intellectual Property and Copyright Statements . . . . . . . . 12



























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1. Introduction

   This document describes SIP conferencing scenarios.  It will describe
   basic and advance conferencing scenarios.  These conferencing
   scenarios will help with the definition and the evaluation of the
   requirements for SIP conferencing framework.  The advanced scenarios
   will assume the UA functionality based on relevant SIP RFCs that will
   be needed in order to participate in the conference and take
   advantage of the conference functionality.  The entities composing
   the conference will be the "focus" that is the center point for
   signaling and the members.  A special member is the member who
   initiated the conference.  The scenarios described are to demonstrate
   different conferencing services that can be offered in the SIP
   environment that will benefit from having some support in the UAs
   that will enable more robust and easier to use conferencing services.
   It will be up to the conferencing bridge manufacturers and the
   service provider to decide what services can be built and which
   services will be offered to the end users.

2. Simple Conferencing scenarios

   These scenarios will assume a UA that support basic SIP functionality
   as described in RFC3261[1]  and RFC3264 [2] .  The reason for these
   scenarios is to enable a basic UA without any specific conferencing
   extensions to create, join and participate in a conference.  The UA
   may use an out of band signaling to participate in a conference but
   this is not a mandatory requirement.  The focus will have all the
   functionality it needs in order to supply the service offered to the
   members.  The UA shall be able to provide DTMF tones.

2.1 Ad-hoc conference

   A user has a service provisioned to him that enables him to start an
   ad-hoc conference when he calls the focus.  When the member wants to
   start a conference he calls the conference service.  The member may
   be identified by different means including the called number, the
   calling number or an IVR system  using in-band DTMF tones.  The
   conference is created automatically with the predefined
   functionality.  The member who has such a service notifies the other
   participants how to call the conference via an external mean like
   email.  The member may have the functionality of a focus and thus can
   create ad-hoc conference using his own UA functionality.  An example
   of such a conference is an audio conference initiated by one of the
   members who has a conference service that enables him to start a
   conference when he calls a specific number (or URI).  The conference
   may be created by the first person calling this number or it may be
   created only after the owner is authenticated using an IVR system,
   the other participants may get an announcement and are placed on hold



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   if they call the conference before the owner.

2.2 Extension of a Point to point calls to a multipoint call

   This is a simple case.  The initiating member is in a call with one
   party and wants to add another party to the call.  The initiating
   member cannot handle the focus on his UA nor can the other member.
   Both of them cannot support call transfer.  The way to do this
   conference is by disconnecting and using the above method.  The
   information about the conference will be conveyed in the
   point-to-point call.  The focus may support dial out allowing the
   initiating member to call the third party.

2.3 Reserved conference

   The reservation was done by out of band mechanism.  The conference
   identification is allocated by the reservation system.  It is sent to
   all participants.  The participants join using the conference
   identification.  The conference identification must be routable
   enabling the allocation of a focus with free resources at the time
   when the conference will actually run.  The focus can also dial out
   to the conference members.  The UAs will not be aware that they are
   in a conference.  The participants may know via announcement from the
   conference that they are in a conference and who are the other
   members

3. Advance Conferencing scenarios

   These scenarios will assume UAs that support at least call transfer
   service and a way to communicate information on events from the focus
   to the UA.  The focus will be able to know the capabilities of the
   members to identify if they support the call transfer.  The section
   will specify in each scenario the dependencies.  An advance
   conference can be initiated by a UA that has advanced features but
   some UAs in the conference may have lesser functionality.

3.1 Extending a point-to-point call to a multipoint call

   The initiating member is in a point-to-point call and want to add a
   third member.  The initiating member can start a multipoint call on a
   conferencing bridge known to him.  The extension can be without
   consultation, which means that he moves the point-to-point call to
   the focus and then adds the third party (this can be done in various
   ways).  The extension can be done with consultation, which means that
   he puts his current party on hold calls, the third party and asks him
   to join the conference and then transfers all the members to the
   conferencing bridge.




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3.2 Lecture mode conferences

   This conference scenario enables a conference with a lecturer that
   present a topic and can allow questions.  The lecturer needs to know
   who are the participants and to be able to give them the right to
   speak.  The right to speak can be based on floor control but can also
   be based on out of band mechanism.

3.3 Conference with non-SIP members

   A focus can include  participants that are not SIP UAs that are
   joining the focus via a gateway function.  Those members may be basic
   participants or the GW function will proxy the advanced functionality
   between the different protocols and the SIP focus.

3.4 A reserved or ad-hoc conference with conference aware members.

   The initiating member will call the focus using for example a unique
   identifier in order to start the conference.  The focus may use some
   authenticating method to qualify the member.  The other participants
   may call the focus and join the conference.  The focus will be able
   to find the capabilities of the members.  In case of a reserved
   conference the focus will start the conference at the scheduled time.
   The members may join by call the conference ID or the focus may call
   them.  The conference may have privilege levels associated with a
   specific conference or member.  The privileges will be for the
   initiating member and for a regular member; the initiating member may
   delegate privileges to the other members.  The privileges will allow
   functionality as defined in the next section.

3.5 Advanced conference features

   The following scenarios can be used in all the advance conferencing
   scenarios.  In the examples given in this section, when referring to
   a member that has a functionality it means a member with the right
   privileges.  These scenarios may be available in the advanced
   conferencing scenarios and are common in many conferencing
   applications.  These are not a requirement list but some examples of
   how specific functionality is being used in a conference.

   Add Participants - A member may add a new member to the focus.  This
   can be done, for example, by instructing the focus to call the
   participant or by the member calling the participant and pointing him
   to the conference.  The member may delete participants from the focus
   if he can identify them.

   Authenticate participants - A member can authenticate members that
   want to join the focus.  This can be done implicitly by assigning a



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   password to the conference and letting the focus authenticate the new
   members or explicitly by directing the authentication requests to the
   initiating member who will authenticate each user.

   Controlling the presentation of media - during the conference the
   member may be able to manage whose media is being sent to each
   participant.  For example the member may be able to decide that he
   wants to be the speaker and all the rest are listeners he may also
   specify whose media he wants to receive.  The member may be able to
   mute a media stream during the conference.

   Giving privileges - the member may want, during the conference, to
   give a privilege to another member.  The assigning of privileges may
   be implicit when requested or explicit by asking the member to grant
   a privilege.

   Side conferences or sidebars - the member may want to create a side
   conference that include some of the participants and when the side
   conference is done the members will return to the main conference.  A
   side bar may have the same functionality as the main conference.
   There can be some sidebars scenarios.  The simple one will be based
   on capabilities of two participants to have two calls at the same
   time and they will have a point to point call in parallel to the main
   conference, it is an end point implementation to decide if to mix
   both calls streams or to enable the user to switch between them.  The
   sidebar scenario that will use the focus will use the same call he is
   in and let the focus create the sidebar and compose the relevant
   sidebar stream mixes.  These mixes can include the main conference as
   an incoming stream to the mix.  The way to signal the creation of the
   sidebar and how to invite members and control the mixes should be
   available.

   Focus information - When a member joins the focus he is announced to
   the members.  An announcement may be available when he leaves the
   focus.  The members may query the focus for its current members.

   Extending of a conference - Reserved conferences and ad-hoc
   conferences may have a time limit.  The focus will inform the members
   when the limit is close and may allow the extension of the
   conference.

   Adding and removing a media type to the conference - a member may
   want to start a power point presentation during a conference.  He may
   want to distribute this new media to all the members.  The member
   will request from the focus to start the new media channel and to
   allow him to send data in the new channel.

   Audio only participants - In a multimedia conference some of the



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   users who wants to join has no way to send and receive all the media.
   Typically they can send and receive audio.  Such participants will
   join the conference as audio only participants.  The general case is
   that users may send and receive only part of the media streams
   available in the multi media conference.

   Passive participants - In a conference some participants may be
   listeners to all or part of the media streams.  They may be invisible
   to all the other participants.

   Recorders - A recorder can be added to the conference.  A recorder
   can record all streams or a subset of the streams.  A recorder is a
   case of a passive participant.

4. Scenarios for media policy control

   On going conferences media streams may be controlled by authorized
   users using either a media control protocol or a third party
   application.  This section will describe some typical media control
   scenarios.  The conference can be of any size starting from small
   conferences (3-5 participants) through medium size of up to 16
   participants and large conferences.  Some of the media control
   scenarios are typical to specific conference size.  As a general rule
   larger conferences scenarios tend to be more centrally managed or
   structured.

   The scenarios apply to audio conferences as well as to multimedia
   conferences.  There are some specific information about the  mixed
   video layout discussed bellow.

4.1 Video mixing scenarios

   For video the user selects one of a set of pre-defined video
   presentations offered by the server.  Each video presentation is
   identified by a textual description as well as an image specifying
   how the presentation looks like on the screen.  In this scenario by
   choosing a video presentation the user chooses how many video streams
   (participants) will be viewed at once and the layout of these video
   streams on the screen.

   The contents of each sub-window can be defined by a conference policy
   or controlled by authorized participants.  In other aspects like
   number of different mixes in the conference and a custom mix for each
   user, these functionality are similar to audio mixing and are based
   on server capabilities and authorization.

   Note that for non-centralized mixing if the endpoint mixer does not
   support the media presentation of the conference, the participant can



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   get the default media presentation offered by the endpoint mixer.

   The following are a list of typical video presentations; there are
   other layouts available today in commercial products:

   - Single view: This presentation typically shows the video of the
   loudest speaker

   - Dual View: This presentation shows two streams.  If the streams are
   to be multiplexed in one image (typical of centralized servers) the
   multiplexing can be:

   1.  Side by side with no altered aspect ratio and hence blanking of
   parts of the image might be necessary if the streams are to be
   combined as one image.

   2.  Side by side windows with altered aspect ratios and hence
   blanking parts of the image is not necessary.  The mixer handles the
   cropping of the images.

   3.  One above the other windows with no altered aspect ratio

   4.  One above the other windows with altered aspect ratio

   - Quadrate view: This presentation shows 4 streams.  If the streams
   are to be multiplexed into one image (centralized server) they will
   be arranged in a 2x2 style.  Note that in this style the aspect
   ratios are maintained.

   - 9 sub-picture view: This presentation shows 9 streams.  If the
   streams are to be multiplexed in one image they will be arranged in a
   3x3 style.  In the multiplexing case cropping is performed under the
   discretion of the mixer.

   - 16 sub-picture view: This presentation shows 16 streams.  If the
   streams are to be multiplexed into one image they will be arranged in
   a 4x4 style.  In this style the aspect ratios are maintained and no
   cropping or blanking is needed.

   - 5+1 sub-picture view: This presentation shows 6 streams.  If the
   streams are to be multiplexed into one image then the pictures are
   laid so that one sub-window occupies four ninth of the screen while
   the other five occupy a ninth of the screen each.

4.2 Typical video conferencing scenario

   In this scenario the audio is typically an n-1 audio mixing.  Every
   participant will get a mixed audio of N loudest participants but his



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   own audio will not be part of the received mix.  All the participants
   will see the current speaker and he will see the previous speaker.
   This mode is typical to small conference.

   User with correct authorization can exclude one or more users from
   the audio or video mix.  An indication might be displayed to the
   affected users indicating that they are not being seen/heard.

   User with correct authorization can manipulate the gain level
   associated with one or more audio streams in the mix.

4.3 Conference Sidebar scenario

   An authorized user creates a side bar.  The user selects whether the
   sidebar should include the media from the main conference or not and
   the audio gain level associated with the main conference audio.

   User invites participants to the sidebar and upon acceptance they
   start receiving the sidebar media as specified by the sidebar
   creator.  If the new participant is not a member of the conference
   but rather just the sidebar the participant will only receive the
   sidebar media without the media of the main conference being mixed.

   User with the right authorization can move another participant into
   the sidebar with no indication in which case the user will suddenly
   start receiving the sidebar media.

   Sidebar participants with the right authorization can select to hear
   or not hear the main conference audio mixed with the sidebar audio

   A participant can be a participant to more than one sidebar but can
   only actively participate in one.

   A participant can jump back and forth between the main conference and
   one or more sidebars to actively participate.

4.4 Coaching scenario

   This is a call center or a remote training session where there is a
   supervisor that can monitor.  There are the supervised users that may
   be the call center operators or the teachers

   The supervisor will be a hidden participant and will not be part of
   the participant roster.

   The supervised users might get an announcement/tone indicating that
   the supervisor has joined.  The other participants do not hear the
   announcement.



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   Supervisor listens/sees to the session but can only be heard/seen by
   the supervised user.

   Supervisor can become a normal participant in which case the
   participants will see the supervisor as part of the roster and will
   start hearing and seeing him.

4.5 Presentation and QA session

   An example is a panel earning call scenario in which a group of
   presenters deliver material to a group of people.  After the
   presentation is finished a QA session is opened.

   The conference is created as a panel and the panel members are
   identified.  Only their streams will be mixed.

   After the end of the presentation the session chair changes the
   conference type to normal and now streams from all users may be
   mixed.

   A floor control protocol can be used instead of changing the
   conference type.  The chair can grant the right to speak by adding
   just the participant whose turn is to ask a question to the
   conference mix.

5. Security Considerations

   No specific security considerations for this draft.  Security
   consideration will be available in the relevant drafts that will
   compose the suggested solution

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












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Authors' Addresses

   Roni Even
   Polycom
   94 Derech Em Hamoshavot
   Petach Tikva  49130
   Israel

   EMail: roni.even@polycom.co.il


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

   EMail: nismail@cisco.com

































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Intellectual Property Statement

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

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































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