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Versions: 00 01 02 03 04 05 rfc4597                                     
XCON                                                             R. Even
Internet-Draft                                                   Polycom
Expires: May 1, 2004                                           N. Ismail
                                                     Cisco Systems, Inc.
                                                           November 2003


                         Conferencing Scenarios
              draft-ietf-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.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on May 1, 2004.

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 and the protocol
   associated with the 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.   Advanced Conferencing scenarios  . . . . . . . . . . . . . .   4
   3.1  Extending a point-to-point call to a multipoint call . . . .   5
   3.2  Lecture mode conferences . . . . . . . . . . . . . . . . . .   5
   3.3  Conference with non-SIP participants . . . . . . . . . . . .   5
   3.4  A reserved or ad-hoc conference with conference aware
        participants.  . . . . . . . . . . . . . . . . . . . . . . .   5
   3.5  Advanced conference features . . . . . . . . . . . . . . . .   6
   4.   Scenarios for media policy control . . . . . . . . . . . . .   8
   4.1  Video mixing scenarios . . . . . . . . . . . . . . . . . . .   8
   4.2  Typical video conferencing scenario  . . . . . . . . . . . .   9
   4.3  Conference Sidebar scenario  . . . . . . . . . . . . . . . .  10
   4.4  Coaching scenario  . . . . . . . . . . . . . . . . . . . . .  10
   4.5  Presentation and QA session  . . . . . . . . . . . . . . . .  11
   4.6  Presence enabled ad-hoc conference . . . . . . . . . . . . .  11
   4.7  Group chat text conferencing . . . . . . . . . . . . . . . .  11
   4.8  Moderated group chat . . . . . . . . . . . . . . . . . . . .  12
   4.9  Text sidebars  . . . . . . . . . . . . . . . . . . . . . . .  12
   4.10 Advanced media control features  . . . . . . . . . . . . . .  12
   5.   Security Considerations  . . . . . . . . . . . . . . . . . .  12
   6.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  13
        References . . . . . . . . . . . . . . . . . . . . . . . . .  13
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  13
        Intellectual Property and Copyright Statements . . . . . . .  14





















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1. Introduction

   This document describes SIP conferencing scenarios.  The development
   of these conferencing scenarios is intended to help with definition
   and evaluation of the requirements for the centralized conferencing
   (XCON) working group.  This document uses definitions, conventions
   and architectures described in the SIP Conferencing Framework
   document[1].  The document describes basic and advance conferencing
   scenarios.  The advanced scenarios will assume that the endpoint
   functionality is based on the future set of XCON protocols that will
   be needed in order to participate in the conference and take
   advantage of the conference functionality.  However, note that many
   of these features can be implemented today using an IVR or web
   interface to control the conferencing application.

   The entities composing the conference will be the "focus" that is the
   center point for signaling and the participants.  A special
   participant is the participant 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.

   The scenarios will describe multimedia examples but they are
   applicable to audio only as well as for audio and video conferences.

2. Simple Conferencing scenarios

   These scenarios will assume a UA that support basic SIP functionality
   as described in RFC3261[2]  and RFC3264 [3] .  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
   participants.  A typical minimum requirement is that the participant
   support DTMF tones/signal or provide voice responses to an IVR
   system..

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 participant
   wants to start a conference he calls the conference service.  The
   participant may be identified by different means including the



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   Request-URI or To header fields, the Contact or From header fields or
   an IVR system  using DTMF.  The conference is created automatically
   with the predefined functionality.  The participant who has such a
   service notifies the other participants how to call the conference
   via external means such as instant message or email.  The participant
   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
   participants who has a conference service that enables him to start a
   conference when he calls a specific URI.  The conference may be
   created by the first person calling this URI 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 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 participant is in a call with
   one party and wants to add another party to the call.  The initiating
   participant cannot provide the focus functioality on his UA nor can
   the other participant.  If neither also support call transfer, the
   only way to create this conference is by disconnecting and using the
   methods desribed in 2.1.  The information about the conference will
   be conveyed in the point-to-point call.  The focus may support dial
   out allowing the initiating participant to call the third party.

2.3 Reserved conference

   The reservation for this type of conference is typically done by out
   of band mechanism and in advance of the actual conference time.  The
   conference identification, which may may be a URI or a phone number
   with a  pin number, is allocated by the reservation system.  It is
   sent to all participants using email, IM, etc.  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 participants.  The
   endpoints may 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 participants

3. Advanced Conferencing scenarios

   These scenarios will assume endpoints that support at least call
   transfer service and a way to communicate information on events from
   the focus to the UA.  The focus has the ability to discover the
   capabilities of the participants, to identify if they support the
   call transfer.  This section will specify in each scenario the



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   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 participant is in a point-to-point call and want to
   add a third participant.  The initiating participant 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 participants to the conferencing bridge.

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.

   In general, the lecturer will be seen/heard by the conference
   participants and often will share a presentation  or application with
   the other participants.

   A participant joining this type of conference can get the identity of
   the lecturer and often the identities of the audience participants.

   This type of conference may have multiple media streams.  For
   example, if simultaneous language translation is available, a
   participant will have the option of selecting the appropriate
   language audio stream.  Multiple video streams could include the
   speaker‚ÇÖs face and a whiteboard/demonstration stream.

3.3 Conference with non-SIP participants

   A focus can include  participants that are not SIP UAs that are
   joining the focus via a gateway function.  Those participants may be
   basic participants or the GW function will proxy the advanced
   functionality between the different protocols and the SIP focus.
   For example, an IVR system or a web page interface can be used to
   provide additional functionality.

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




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   The initiating participant 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 participant.  The other
   participants may call the focus and join the conference.  The focus
   will be able to find the capabilities of the participants.  In case
   of a reserved conference the focus will start the conference at the
   scheduled time.  The participants may join by call the conference URI
   or the focus may call them.  The conference may have privilege levels
   associated with a specific conference or participant.  The privileges
   will be for the initiating participant and for a regular participant;
   the initiating participant may delegate privileges to the other
   participants.  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 participant that has a functionality it means a participant 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 participant may add a new participant to the
   focus.  This can be done, for example, by instructing the focus to
   call the participant or by the participant calling the participant
   and pointing him to the conference.  The participant may delete
   participants from the focus if he can identify them.

   Changing Devices/Modes ‚Çô During the course of a conference, a
   participant may switch between devices with different capabilities
   while still remaining part of the conference.  For example, a
   participant may initially join using a mobile phone then switch to a
   desk top phone.  Or a participant may join with a phone, discover
   that the conference has video streams available, and switch to a
   video phone.

   Authenticate participants - A participant can authenticate
   participants that want to join the focus.  This can be done
   implicitly by assigning a password to the conference and letting the
   focus authenticate the new participants or explicitly by directing
   the authentication requests to the initiating participant who will
   authenticate each user.

   Controlling the presentation of media - during the conference the
   participant may be able to manage whose media is being sent to each
   participant.  For example the participant may be able to decide that



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   he wants to be the speaker and all the rest are listeners he may also
   specify whose media he wants to receive.  The participant may be able
   to mute a media stream during the conference.

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

   Side conferences or sidebars - the participant may want to create a
   side conference that include some of the participants and when the
   side conference is done the participants 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 participants and control
   the mixes should be available.  For example, participants in an audio
   sidebar can generally not be heard by the rest of the conference.
   However, the main conference audio may be mixed in the sidebar, but
   at a low volume, or in a different channel.  A sidebar can be a
   different media type from the main conference ‚Çô a video call can
   have an audio sidebar where the other participants can see the
   sidebar participants talking but can not hear them.  Or an audio or
   video conference may have a text sidebar.

   Focus information - When a participant joins the focus he is
   announced to the participants.  An announcement may be available when
   he leaves the focus.  The participants may query the focus for its
   current participants.  This presence information can be used by
   applications.

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

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



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   Audio only participants - In a multimedia conference some of the
   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



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   support the media presentation of the conference, the participant can
   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



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   participant will get a mixed audio of N loudest participants but his
   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 participant 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



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   the supervisor has joined.  The other participants do not hear the
   announcement.

   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 participants 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.

4.6 Presence enabled ad-hoc conference

   A presence enabled ad-hoc conference, sometimes described as Push To
   Talk (PTT) is a scenario in which a participant sends media to the
   other participants of the conference after receiving a confirmation
   of the other participants availability.  For example, as implemented
   in cell phones, a participant presses a talk button which checks the
   presence of the participants to see if they are available for
   communication.  If they are, a confirmation tone is played and the
   participant can then talk, which results in the media being sent to
   the other participants in the conference.  These types of conferences
   tend to be long lived, hence the need for presence to ensure that the
   other participants are still available.  The ad-hoc nature of the
   conference means that the participant list can be changed at any
   time.

4.7 Group chat text conferencing

   Group chat is a common scenario for text messaging in which a
   participant joins (or enters) a chat room in which text messages from



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   participants are rendered in a single window and attributed to the
   participant that sent the message.  Changes in conference membership
   are often announced in the text window itself (e.g.  "Alice has just
   entered the room.  Bob has just departed.")  Note that a real-time
   transcription/closed captioning service can provide a similar window
   in which audio media is converted to text.

4.8 Moderated group chat

   A moderated group chat scenario for text messaging is similar to
   group chat but with all text messages sent to the group being
   filtered/approved by a moderator.  Note that the moderator can be a
   human or an application.  The moderator also often has the ability to
   remove participants and provide feedback on their submissions (e.g.
   provide warnings before removal).

4.9 Text sidebars

   Text or instant messaging sidebars are perhaps the most common
   sidebars in conferences today.  Often the text sessions are separate
   from the conference.  However, there are some advantages to having
   text sessions be a sidebar and as a result a part of the main
   conference.  For example, a conference which is providing anonymity/
   aliases to participants can also provide anonymous/alias sidebars.  A
   text sidebar can also benefit from other security/logging/recording
   services provided by the focus.

4.10 Advanced media control features

   The following features can be used in all the conferenceing
   scenarios.

   Announcement - The conference moderator may be able to play
   announcments to all the conference participants.  The announcement
   may be pre-recorded or composed by the moderator before sending them.
   The annoucments may be text, audio or audio visual.  An example is a
   conference with several audio break out sessions going on.  At some
   point in the time, the moderator wants to record an audio message
   like "in 5 minutes, everyone please come back to the main meeting"
   and then play that message to all of the breakout sessions.

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





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6. Acknowledgements

   Thanks to Brian Rosen for contributing conferencing scenarios.

   Thanks to Alan Johnston for going over the document and adding some
   more scenarios.

References

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

   [2]  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.

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


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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Internet-Draft            Conference Scenarios             November 2003


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Acknowledgement

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