draft-ietf-xcon-conference-scenarios-03.txt   draft-ietf-xcon-conference-scenarios-04.txt 
XCON R. Even XCON R. Even
Internet-Draft Polycom Internet-Draft Polycom
Expires: September 26, 2005 N. Ismail Expires: October 27, 2005 N. Ismail
Cisco Systems, Inc. Cisco Systems, Inc.
March 28, 2005 April 25, 2005
Conferencing Scenarios Conferencing Scenarios
draft-ietf-xcon-conference-scenarios-03.txt draft-ietf-xcon-conference-scenarios-04.txt
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Abstract Abstract
This document describes multimedia conferencing scenarios. It This document describes multimedia conferencing scenarios. It
describes both basic and advance conferencing scenarios involving describes both basic and advanced conferencing scenarios involving
voice, video, text and interactive text sessions. These conferencing voice, video, text and interactive text sessions. These conferencing
scenarios will help with the definition and evaluation of the scenarios will help with the definition and evaluation of the
protocols being developed in the centralized conferencing XCON protocols being developed in the centralized conferencing XCON
working group. working group.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Simple Conferencing scenarios . . . . . . . . . . . . . . . 3 2. Basic Conferencing scenarios . . . . . . . . . . . . . . . . 3
2.1 Ad-hoc conference . . . . . . . . . . . . . . . . . . . . 4 2.1 Ad-hoc conference . . . . . . . . . . . . . . . . . . . . 4
2.2 Extension of a Point to point calls to a multipoint call . 4 2.2 Extension of a Point to point calls to a multipoint call . 4
2.3 Reserved conference . . . . . . . . . . . . . . . . . . . 4 2.3 Reserved conference . . . . . . . . . . . . . . . . . . . 4
3. Advanced Conferencing scenarios . . . . . . . . . . . . . . 5 3. Advanced Conferencing scenarios . . . . . . . . . . . . . . 5
3.1 Extending a point-to-point call to a multipoint call . . . 5 3.1 Extending a point-to-point call to a multipoint call . . . 5
3.2 Lecture mode conferences . . . . . . . . . . . . . . . . . 5 3.2 Lecture mode conferences . . . . . . . . . . . . . . . . . 5
3.3 Conference with simple and advanced participants . . . . . 5 3.3 Conference with conference aware and unaware
participants . . . . . . . . . . . . . . . . . . . . . . . 6
3.4 A reserved or ad-hoc conference with conference-aware 3.4 A reserved or ad-hoc conference with conference-aware
participants. . . . . . . . . . . . . . . . . . . . . . . 6 participants. . . . . . . . . . . . . . . . . . . . . . . 6
3.5 Advanced conference features . . . . . . . . . . . . . . . 6 3.5 Advanced conference features . . . . . . . . . . . . . . . 6
4. Scenarios for media policy control . . . . . . . . . . . . . 8 4. Scenarios for media policy control . . . . . . . . . . . . . 9
4.1 Video mixing scenarios . . . . . . . . . . . . . . . . . . 9 4.1 Video mixing scenarios . . . . . . . . . . . . . . . . . . 9
4.2 Typical video conferencing scenario . . . . . . . . . . . 10 4.2 Typical video conferencing scenario . . . . . . . . . . . 10
4.3 Conference Sidebar scenario . . . . . . . . . . . . . . . 10 4.3 Conference Sidebar scenario . . . . . . . . . . . . . . . 10
4.4 Coaching scenario . . . . . . . . . . . . . . . . . . . . 11 4.4 Coaching scenario . . . . . . . . . . . . . . . . . . . . 11
4.5 Presentation and QA session . . . . . . . . . . . . . . . 11 4.5 Presentation and QA session . . . . . . . . . . . . . . . 11
4.6 Presence-enabled ad-hoc conference . . . . . . . . . . . . 12 4.6 Presence-enabled ad-hoc conference . . . . . . . . . . . . 12
4.7 Group chat text conferencing . . . . . . . . . . . . . . . 12 4.7 Group chat text conferencing . . . . . . . . . . . . . . . 12
4.8 Interactive text . . . . . . . . . . . . . . . . . . . . . 12 4.8 Interactive text . . . . . . . . . . . . . . . . . . . . . 12
4.9 Moderated group chat . . . . . . . . . . . . . . . . . . . 13 4.9 Moderated group chat . . . . . . . . . . . . . . . . . . . 13
4.10 Text sidebars . . . . . . . . . . . . . . . . . . . . . 13 4.10 Text sidebars . . . . . . . . . . . . . . . . . . . . . 13
4.11 Advanced media control features . . . . . . . . . . . . 13 4.11 Conference announcements . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 14 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 14
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
8. Informative References . . . . . . . . . . . . . . . . . . . 14 8. Informative References . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . 16
1. Introduction 1. Introduction
This document describes multimedia conferencing scenarios. The This document describes multimedia conferencing scenarios. The
development of these conferencing scenarios is intended to help with development of these conferencing scenarios is intended to help with
definition and evaluation of the requirements for the centralized definition and evaluation of the requirements for the centralized
conferencing (XCON) working group. Although this document uses conferencing (XCON) working group. Although this document uses some
definitions, conventions and architectures described in the SIP definitions and conventions described in the SIP Conferencing
Conferencing Framework document[1], these scenarios are not Framework document[1], these scenarios are not SIP-specific. The
SIP-specific. The document describes basic and advanced conferencing document describes basic and advanced conferencing scenarios. The
scenarios. The advanced scenarios will assume that the endpoint advanced scenarios assume that the user agents support the set of
functionality is based on the future set of XCON protocols that will XCON protocols, identified in the Framework and Data Model for
be needed in order to participate in the conference and take Centralized Conferencing [3], in order to take advantage of the
advantage of the conference functionality. However, note that many conference functioality. However, note that many of these features
of these features can be implemented today using an IVR or web can be implemented today using an IVR or web interface to control the
interface to control the conferencing application. conferencing application.
The entities comprising the conference will be the "focus" that is The entities comprising the Conferencing System are the conference
the center point for signaling and the participants. A special that is the center point for signaling and the participants. The
participant is the participant who initiated the conference. The participant who initiated the conference is referenced as the
scenarios described are in order to demonstrate different initiating participant.
conferencing services. These conferencing services can be offered in
a multimedia environment that will benefit from having some support
in the endpoints 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 The scenarios described demonstrate different conferencing services.
applicable to audio only as well as for audio and video conferences. These conferencing services can be offered in a multimedia
environment that benefit from having some support in the user agents
that enable more robust and easier to use conferencing services. It
is up to the conferencing system manufacturers and the conferencing
service provider to decide what services can be built and which
services are offered to the end users.
The scenarios describe multimedia examples but they are applicable to
audio only as well as for audio and video conferences.
Multimedia conferences may include any combination of different media Multimedia conferences may include any combination of different media
types like audio, video, text, interactive text, or presentation types like audio, video, text, interactive text, or presentation
graphics. The conference scenarios are similar but the media graphics. The conference scenarios are similar but the media
handling may be dependent on the media type. handling may be dependent on the media type.
2. Simple Conferencing scenarios 2. Basic Conferencing scenarios
These scenarios enable a basic endpoint without any specific These scenarios enable a conference unaware participant to create,
conferencing extensions to create, join and participate in a join and participate in a conference. The participant may use out of
conference. The endpoint may use out of band signaling to band signaling to participate in a conference but this is not a
participate in a conference but this is not a mandatory requirement. mandatory requirement. The Conferencing System has all the
The focus will have all the functionality it needs in order to supply functionality it needs in order to supply the service offered to the
the service offered to the participants. A typical minimum participants. A typical minimum requirement is that the participant
requirement is that the participant support DTMF tones/signal or support DTMF tones/signal or provide voice responses to an IVR
provide voice responses to an IVR system. system.
2.1 Ad-hoc conference 2.1 Ad-hoc conference
A user has a service provisioned to him that enables him to start an A participant has a service provisioned to him that enables him to
ad-hoc conference when he calls the focus. When the participant start an ad-hoc conference when he calls the Conferencing System.
wants to start a conference he calls the conference service. The When the participant wants to start a conference he calls the
participant may be identified by different means including request conference service. The participant may be identified by different
destination, authenticated identity, or an IVR system using DTMF. means including request destination, authenticated identity, or an
The conference is created automatically with the predefined IVR system using DTMF. The conference is created automatically with
functionality. The participant who has such a service notifies the the predefined functionality. The participant who has such a service
other participants how to call the conference via external means such notifies the other participants how to call the conference via
as instant message or email. The participant may have the external means such as instant message or email. The participant may
functionality of a focus and thus can create ad-hoc conference using have the functionality of a Conferencing System and thus can create
his own endpoint functionality. An example of such a conference is ad-hoc conference using his own user agent functionality. An example
an audio conference initiated by one of the participants who has a of such a conference is an audio conference initiated by one of the
conference service that enables him to start a conference when he participants who has a conference service that enables him to start a
calls a specific URI. The conference may be created by the first conference when he calls a specific URI. The conference may be
person calling this URI or it may be created only after the owner is created by the first person calling this URI or it may be created
authenticated using an IVR system. In the latter case, the other only after the owner is authenticated using an IVR system. In the
participants may get an announcement and are placed on hold if they latter case, the other participants may get an announcement and are
call the conference before the owner. placed on hold if they call the conference before the owner.
2.2 Extension of a Point to point calls to a multipoint call 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 This is a basic case. The initiating participant (PA) is in a point
one party and wants to add another party to the call. The initiating to point call with another participant (PB). PA wants to add a third
participant cannot provide the focus functionality on his endpoint participant (PC) to the call. The initiating participant (PA) cannot
nor can the other participant. If neither also supports call provide the Conferencing System functionality on his user agent nor
transfer, the only way to create this conference is by disconnecting can the other participant (PB). PA and PB do not supports call
and using the methods described in 2.1. The information about the transfer. PA has a conferencing service using the methods described
conference will be conveyed in the point-to-point call. The focus in 2.1. PA conveys the conference information to PB in the point-to-
may support dial out, allowing the initiating participant to call the point call. Both participant disconnect and call the Conferencing
third party. System. The Conferencing System may support dial out, for example
via DTMF, allowing the initiating participant to call the third party
through the Conferencing System.
2.3 Reserved conference 2.3 Reserved conference
The reservation for this type of conference is typically done by an The reservation for this type of conference is typically done by an
out of band mechanism and in advance of the actual conference time. out of band mechanism and in advance of the actual conference time.
The conference identification, which may be a URI or a phone number The conference identification, which may be a URI or a phone number
with a pin number, is allocated by the reservation system. It is with a pin number, is allocated by the reservation system. It is
sent to all participants using email, IM, etc. The participants join sent to all participants using email, IM, etc. The participants join
using the conference identification. The conference identification using the conference identification. The conference identification
must be routable enabling the allocation of a focus with free must be routable enabling the allocation of a conference with free
resources at the time when the conference will actually run. The resources at the time when the conference actually run. The
focus can also dial out to the conference participants. The Conferencing System can also dial out to the conference participants.
endpoints may not be aware that they are in a conference. The The participants may not be informed that they are in a conference
participants may know via announcement from the conference that they since their User Agent is not conference aware. The participants may
are in a conference and who the other participants are. know, via announcement from the Conferenceing System, that they are
in a conference and who the other participants are.
3. Advanced Conferencing scenarios 3. Advanced Conferencing scenarios
These scenarios will assume endpoints that support at least call These scenarios assume user agents that support at least call
transfer service and a way to communicate information on events from transfer service and a way to communicate information on events from
the focus to the endpoint. The focus has the ability to discover the the Conferencing System to the user agent. The Conferencing System
capabilities of the participants, to identify if they support call may have the ability to discover the capabilities of the
transfer. This section will specify in each scenario the participants, for example, to identify if they support call transfer.
dependencies. An advanced conference can be initiated only by an This section specifies in each scenario the dependencies. An
endpoint that has advanced features, but some endpoints in the advanced conference can be initiated only by an user agent that has
conference may have less functionality. advanced features, but some user agents in the conference may have
less functionality.
3.1 Extending a point-to-point call to a multipoint call 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 The initiating participant is in a point-to-point call and wants to
add a third participant. The initiating participant can start a add a third participant. The initiating participant can start a
multipoint call on a conferencing bridge known to him. The extension multipoint call on a conferencing bridge known to him. The extension
can be without consultation, which means that he moves the can be without consultation, which means that he moves the point-to-
point-to-point call to the focus and then adds the third party (this point call to the Conferencing System and then adds the third party
can be done in various ways). Alternatively the extension can be (this can be done in various ways). Alternatively the extension can
done with consultation, which means that he puts his current party on be done with consultation, which means that he puts his current party
hold, calls the third party and asks him to join the conference, and on hold, calls the third party and asks him to join the conference,
then transfers all the participants to the conferencing bridge. and then transfers all the participants to the Conferencing System.
3.2 Lecture mode conferences 3.2 Lecture mode conferences
This conference scenario enables a conference with a lecturer who This conference scenario enables a conference with a lecturer who
presents a topic and can allow questions. The lecturer needs to know presents a topic and can allow questions. The lecturer needs to know
who the participants are and to be able to give them the right to who the participants are and to be able to give them the right to
speak. The right to speak can be based on floor control or an out of speak. The right to speak can be based on floor control or an out of
band mechanism. band mechanism.
In general, the lecturer will be seen/heard by the conference In general, the lecturer is seen/heard by the conference participants
participants and often will share a presentation or application with and often shares a presentation or application with the other
the other participants. participants.
A participant joining this type of conference can get the identity of A participant joining this type of conference can get the identity of
the lecturer and often the identities of the audience participants. the lecturer and often the identities of the audience participants.
This type of conference may have multiple media streams. For This type of conference may have multiple media streams. For
example, if simultaneous language translation is available, a example, if simultaneous language translation is available, a
participant will have the option of selecting the appropriate participant has the option of selecting the appropriate language
language audio stream. Multiple video streams could include the audio stream. Multiple video streams could include the speaker's
speaker's face and a whiteboard/demonstration stream. face and a whiteboard/demonstration stream.
3.3 Conference with simple and advanced participants 3.3 Conference with conference aware and unaware participants
A focus can include participants that are a mix of simple and A conference can include participants that are a mix of conference
advanced participants. Those participants may be basic participants aware and unaware participants. Those participants may be conference
or the GW function may proxy the advanced functionality between the unaware participants using a proxy function that proxies the advanced
different protocols and the focus. For example, an IVR system or a functionality between the different protocols and the Conferencing
web page interface can be used to provide additional functionality. System. 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. 3.4 A reserved or ad-hoc conference with conference-aware participants.
The initiating participant will call the focus using, for example, a The initiating participant calls the Conferencing System using, for
unique identifier in order to start the conference. The focus may example, a unique identifier in order to start the conference. The
use some authenticating method to qualify the participant. The other Conferencing System may use some authenticating method to qualify the
participants may call the focus and join the conference. The focus participant. The other participants may call the Conferencing System
will be able to find the capabilities of the participants. In case and join the conference. The Conferencing System is able to find the
of a reserved conference the focus will start the conference at the capabilities of the participants. In case of a reserved conference
scheduled time. The participants may join by calling the conference the Conferencing System starts the conference at the scheduled time.
URI or the focus may call them. The conference may have privilege The participants may join by calling the conference URI or the
Conferencing System may call them. The conference may have privilege
levels associated with a specific conference or participant. The levels associated with a specific conference or participant. The
privileges will be for the initiating participant and for a regular privileges are for the initiating participant and for a regular
participant; the initiating participant may delegate privileges to participant; the initiating participant may delegate privileges to
the other participants. The privileges will allow functionality as the other participants. The privileges allow functionality as
defined in the next section. defined in the next section.
3.5 Advanced conference features 3.5 Advanced conference features
The following scenarios can be used in all the advanced conferencing The following features can be used in all the advanced conferencing
scenarios. In the examples given in this section, when referring to scenarios. In the examples given in this section, when referring to
a participant that has a functionality it means a participant with a participant that has a functionality it means a participant with
the right privileges. These scenarios may be available in the the right privileges. These scenarios may be available in the
advanced conferencing scenarios and are common in many conferencing advanced conferencing scenarios and are common in many conferencing
applications. This is not a requirement list, rather some examples applications. This is not a requirement list, rather some examples
of how specific functionality are being used in a conference. of how specific functions may be 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 first participant calling the new
participant and pointing him to the conference. The participant may
delete participants from the focus if he can identify them.
Changing Devices/Modes - 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 and 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.
Changing Media - During the conference a participant may be able to
select different media streams than the one he had when he joined the
conference. An example is a participant that initially joined the
conference as an audio participant. The participant was not able to
understand the conversation properly and he learned that there is
also an interactive text available, the participant asked to receive
also the text stream. The text sidebar may be using RFC 2973
interactive text.
Authenticate participants - A participant can authenticate other
participants who 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
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 o Add Participants - A participant may add a new participant to the
side conference that include some of the participants. When the side conference. This can be done, for example, by instructing the
conference is done the participants will return to the main Conferencing System to call the participant or by the first
conference. A sidebar may have the same functionality as the main participant calling the new participant and pointing him to the
conference. There can be some sidebars scenarios. The simple one conference.
will be based on capabilities of two participants to have two calls o Delete Participant - A participant may delete participants from
at the same time and they will have a point to point call in parallel the conference if he can identify them.
to the main conference. This is an end point implementation o Changing User Agent/Modes - During the course of a conference, a
specific, to decide if to mix both calls streams or to enable the participant may switch between user agents with different
user to switch between them. The sidebar scenario that will use the capabilities while still remaining part of the conference. For
focus will use the same call he is in and let the focus create the example, a participant may initially join using a mobile phone and
sidebar and compose the relevant sidebar stream mixes. These mixes then switch to a desk top phone. Or a participant may join with a
can include the main conference as an incoming stream to the mix. A phone, discover that the conference has video streams available,
way to signal the creation of the sidebar and how to invite and switch to a video phone.
participants and control the mixes should be available. For example, o Changing Media - During the conference a participant may be able
participants in an audio sidebar can generally not be heard by the to select different media streams than the one he had when he
rest of the conference. However, the main conference audio may be joined the conference. An example is a participant that initially
mixed in the sidebar, but at a low volume, or in a different channel. joined the conference as an audio participant. The participant is
For example, a sidebar can have a different media type from the main unable to understand the conversation properly and he learns that
conference - a video call can have an audio sidebar where the other there is also an interactive text available, he will ask to
participants can see the sidebar participants talking but can not receive also the text stream.
hear them; or an audio or video conference may have a text sidebar. o Authenticate participants - A participant can authenticate other
participants who want to join the conference. This can be done
implicitly by assigning a password to the conference and letting
the Conferencing System authenticate the new participants or
explicitly by directing the authentication requests to the
initiating participant who authenticates each participant.
o 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 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.
o 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.
o Side conferences or sidebars - The participant may want to create
a side conference that include some of the main conference
participants. When the side conference is done the participants
return to the main conference. A sidebar may have the same
functionality as the main conference. There can be several
sidebars scenarios:
Focus information - When a participant joins the focus he is 1. Basic sidebar is based on the capabilities of two participants
announced to the participants. An announcement may be available when to have two calls at the same time, with a point to point call
he leaves the focus. The participants may query the focus for its in parallel to the main conference. It is user agent
current participants. This presence information can be used by implementation specific whether to automaticly mix both call's
applications. streams or allow the participant to manually switch between
them.
Extending of a conference - Reserved conferences and ad-hoc 2. Conferencing System based sidebar uses the Conferencing System
conferences may have a time limit. The focus will inform the to create the sidebar and compose the relevant sidebar stream
participants when the limit is approaching and may allow the mixes. These mixes can include the main conference as an
extension of the conference. incoming stream to the mix. Mechanisms to signal the creation
of the sidebar, invite participants and control the mixes
should be available.
Adding and removing a media type to the conference - A participant For example, participants in an audio sidebar may not be heard
by the rest of the conference. However, the main conference
audio may be mixed in the sidebar, but at a lower volume, or in
a different channel. Another example, a sidebar can have a
different media type from the main conference; 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.
o Conference information - When a participant joins the conference
he is announced to the participants. An announcement may be
available when he leaves the conference. The participants may
query the conferencing system for the current participants of a
specific conference. This conference information may include
other information, for example, the media streams available in the
conference.
o Extending of a conference - Reserved conferences and ad-hoc
conferences may have a time limit. The Conferencing System
informs the participants when the limit is approaching and may
allow the extension of the conference.
o Adding and removing a media type to the conference - A participant
may want to start a data presentation during a conference. He may may want to start a data presentation during a conference. He may
want to distribute this new media to all the participants. The want to distribute this new media to all the participants. The
participant will ask the focus to start the new media channel and to participant asks the Conferencing System to start the new media
allow him to send data in the new channel. channel and to allow him to send data in the new channel.
o Audio-only participants - In a multimedia conference some of the
Audio-only participants - In a multimedia conference some of the participants who want to join may have no way to send and receive
users who want to join may have no way to send and receive all the all the media types. Typically they can send and receive audio.
media types. Typically they can send and receive audio. Such Such participants join the conference as audio-only participants.
participants will join the conference as audio-only participants. The general case is that participants may send and receive only
The general case is that users may send and receive only part of the part of the media streams available in the multi media conference.
media streams available in the multi media conference. o Passive participants - In a conference some participants may be
Passive participants - In a conference some participants may be
listeners to all or part of the media streams, but be invisible to listeners to all or part of the media streams, but be invisible to
all the other participants. all the other participants.
o Recorders - A recorder can be added to the conference. A recorder
Recorders - A recorder can be added to the conference. A recorder can record all streams or a subset of the streams. Recoreders may
can record all streams or a subset of the streams. A recorder is a be turned on and off during the conference. Recorders may be used
case of a passive participant. for "role call" scenario in order to recored a participant name.
This name can be annpunced at a later stage automaticly or based
Whisper/Private Message - A participant can send a one way message on a participant request. A recorder is a case of a passive
(text, audio, or even some other media) to another participant that participant.
is immediately rendered. This differs from a sidebar in that it is o Whisper/Private Message - A participant can send a one way message
immediate and creates no long-lived session. (text, audio, or even some other media) to another participant
that is immediately rendered. This differs from a sidebar in that
it is immediate and creates no long-lived session.
o Human operator - A aprticipant may ask for assistence from a human
operator during the conference.
4. Scenarios for media policy control 4. Scenarios for media policy control
During a conference media streams may be controlled by authorized During a conference media streams may be controlled by authorized
users using either a media control protocol or a third party participants using either a media control protocol or a third party
application. This section will describe some typical media control application. This section describes some typical media control
scenarios. The conference can be of any size starting from small scenarios. The conference can be of any size. Some of the media
conferences (3-5 participants) through medium size of up to 16 control scenarios are typical to specific conference sizes. As a
participants and large conferences. Some of the media control general rule larger conferences scenarios tend to be more centrally
scenarios are typical to specific conference sizes. As a general managed or structured.
rule larger conferences scenarios tend to be more centrally managed
or structured. The mixing of media in a conference may start when the conference
starts or when the initiating participant joins. In the later case,
early aprticipant may be put on hold and get "music on hold".
The scenarios apply to audio conferences as well as to multimedia The scenarios apply to audio conferences as well as to multimedia
conferences. There are some specific information about the mixed conferences. There are some specific information about the mixed
video layout and about interactive text discussed bellow. video layout and about interactive text discussed below.
4.1 Video mixing scenarios 4.1 Video mixing scenarios
For video the user selects one of a set of pre-defined video For video the participant selects one of a set of pre-defined video
presentations offered by the server. Each video presentation is presentations offered by the server. Each video presentation is
identified by a textual description as well as an image specifying identified by a textual description as well as an image specifying
how the presentation looks like on the screen. In this scenario by how the presentation appears on the screen. In this scenario by
choosing a video presentation the user chooses how many video streams choosing a video presentation the participant chooses how many video
(participants) will be viewed at once and the layout of these video streams (participants) are viewed at once and the layout of these
streams on the screen. video streams on the screen.
The contents of each sub-window can be defined by a conference policy The contents of each sub-window can be defined by a conference policy
or controlled by authorized participants. Other aspects like number and/or controlled by authorized participants. It may also be
of different mixes in the conference and a custom mix for each possible to have multiple mixes per conference, possibly as many as
participant, these functionalities are applicable also to audio there are participants. (Note that the same flexibility may be
mixing and are based on server capabilities and authorization. afforded to audio mixes as well.).
The following are a list of typical video presentations; there are The following are a list of typical video presentations; there are
other layouts available today in commercial products: other layouts available today in commercial products:
- Single view: This presentation typically shows the video of the - Single view: This presentation typically shows the video of the
loudest speaker loudest speaker
- Dual View: This presentation shows two streams. If the streams are - Dual View: This presentation shows two streams. If the streams are
to be multiplexed in one image (typical of centralized servers) the to be multiplexed in one image (typical of centralized servers) the
multiplexing can be: multiplexing can be:
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2. Side by side windows with altered aspect ratios and hence 2. Side by side windows with altered aspect ratios and hence
blanking parts of the image is not necessary. The mixer handles the blanking parts of the image is not necessary. The mixer handles the
cropping of the images. cropping of the images.
3. One above the other windows with no altered aspect ratio 3. One above the other windows with no altered aspect ratio
4. One above the other windows with altered aspect ratio 4. One above the other windows with altered aspect ratio
- Quadrate view: This presentation shows 4 streams. If the streams - Quadrate view: This presentation shows 4 streams. If the streams
are to be multiplexed into one image (centralized server) they will are multiplexed into one image (centralized server) they are arranged
be arranged in a 2x2 style. Note that in this style the aspect in a 2x2 style. Note that in this style the aspect ratios are
ratios are maintained. maintained.
- 9 sub-picture view: This presentation shows 9 streams. If the - 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 streams are to be multiplexed in one image they are arranged in a 3x3
3x3 style. In the multiplexing case cropping is performed under the style. In the multiplexing case cropping is performed under the
discretion of the mixer. discretion of the mixer.
- 16 sub-picture view: This presentation shows 16 streams. If the - 16 sub-picture view: This presentation shows 16 streams. If the
streams are to be multiplexed into one image they will be arranged in streams are to be multiplexed into one image they are arranged in a
a 4x4 style. In this style the aspect ratios are maintained and no 4x4 style. In this style the aspect ratios are maintained and no
cropping or blanking is needed. cropping or blanking is needed.
- 5+1 sub-picture view: This presentation shows 6 streams. If the - 5+1 sub-picture view: This presentation shows 6 streams. If the
streams are to be multiplexed into one image then the pictures are streams are to be multiplexed into one image then the pictures are
laid so that one sub-window occupies 4/9 of the screen while the laid so that one sub-window occupies 4/9 of the screen while the
other five occupy 1/9 of the screen each. other five occupy 1/9 of the screen each.
4.2 Typical video conferencing scenario 4.2 Typical video conferencing scenario
In this scenario the audio is typically an n-1 audio mix. Every This scenario is known as voice activated video switch. Every
participant will get a mixed audio of N loudest participants but his participant hears the N loudest participants but he does not hear
own audio will not be part of the received mix. All the participants himself. All the participants see the loudest speaker; the loudest
will see the current speaker and he will see the previous speaker. speaker may see the previous loudest speaker. This mode is typical
This mode is typical to small conference. to small conference.
User with correct authorization can exclude one or more users from A participant with proper authorization can exclude one or more
the audio or video mix. An indication might be displayed to the participants from the audio or video mix. An indication might be
affected users indicating that they are not being seen/heard. displayed to the affected participants indicating that they are not
being seen/heard.
User with correct authorization can manipulate the gain level A participant with proper authorization can manipulate the gain level
associated with one or more audio streams in the mix. associated with one or more audio streams in the mix.
4.3 Conference Sidebar scenario 4.3 Conference Sidebar scenario
An authorized user creates a side bar. The user selects whether the An authorized participant creates a side bar. The participant
sidebar should include the media from the main conference or not and selects whether the sidebar should include the media from the main
the audio gain level associated with the main conference audio. conference or not and the audio gain level associated with the main
conference audio.
A user invites participants to the sidebar and upon acceptance they A participant invites participants to the sidebar and upon acceptance
start receiving the sidebar media as specified by the sidebar they start receiving the sidebar media as specified by the sidebar
creator. If the new participant is not a participant of the creator. If the new participant is not a participant of the
conference but rather just the sidebar the participant will only conference, but just the sidebar, the participant only receives the
receive the sidebar media without the media of the main conference if sidebar media without the media of the main conference.
it was part of the sidebar mix.
A user with the right authorization can move another participant into A participant with the right authorization can move another
the sidebar with no indication in which case the user will suddenly participant into the sidebar with no indication, in which case the
start receiving the sidebar media. participant suddenly start receiving the sidebar media.
Sidebar participants with the right authorization can select to hear Sidebar participants with the right authorization can select to hear
or not hear the main conference audio mixed with the sidebar audio 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 A participant can be a participant to more than one sidebar but can
only actively participate in one. only actively participate in one.
A participant can jump back and forth between the main conference and A participant can jump back and forth between the main conference and
one or more sidebars to actively participate. one or more sidebars.
4.4 Coaching scenario 4.4 Coaching scenario
This is a call center or a remote training session where there is a This is a call center or a remote training session where there is a
supervisor who can monitor the conference. There are the supervised supervisor who can monitor the conference. There are the supervised
users that may be the call center operators or the teachers. A participants that may be the call center operators or the teachers.
participant is the conference may be a supervised user or a A participant is the conference may be a supervised participant or a
"customer". "customer".
The supervisor will be a hidden participant and will not be part of The supervisor is a hidden participant and is not part of the
the participant roster. participant roster.
The supervised users might get an announcement/tone indicating that The supervised participants might get an announcement/tone indicating
the supervisor has joined. The other participants do not hear the that the supervisor has joined. The other participants do not hear
announcement. the announcement.
The supervisor listens/sees to the session but can only be heard/seen The supervisor listens to / sees the session but can only be heard /
by the supervised user. seen by the supervised participant.
The supervisor can become a normal participant, in which case the The supervisor can become a normal participant, in which case the
participants will see the supervisor as part of the roster and will participants see the supervisor as part of the roster and start
start hearing and seeing him. hearing and seeing him.
4.5 Presentation and QA session 4.5 Presentation and QA session
An example is an earning call scenario in which a group of presenters An example is an earning call scenario in which a group of presenters
deliver material to a group of people. After the presentation is deliver material to a group of people. After the presentation is
finished a QA session is opened. finished a QA session is opened.
The conference is created as a panel and the panel participants are The conference is created as a panel and the panel participants are
identified. Only their streams will be mixed. identified. Only their streams are mixed.
After the end of the presentation the session chair changes the After the end of the presentation the session chair changes the
conference type to normal and now streams from all users may be conference type to normal and now streams from all participants may
mixed. be mixed. Alternatively a floor control protocol can be used. The
chair can grant the right to speak by adding the participant, whose
A floor control protocol can be used instead of changing the turn it is to ask a question, to the conference mix.
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 4.6 Presence-enabled ad-hoc conference
A presence-enabled ad-hoc conference, sometimes described as "walkie A presence-enabled ad-hoc conference, sometimes described as "walkie
talkie" service, is a scenario in which a participant sends media to talkie" service, is a scenario in which a participant sends media to
the other participants of the conference after receiving a the other participants of the conference after receiving a
confirmation of the other participants' availability. For example, a confirmation of the other participants' availability. For example, a
participant presses a talk button, which checks the presence of the participant presses a talk button, which checks the presence of the
participants to see if they are available for communication. If they participants to see if they are available for communication. If they
are, a confirmation tone is played and the participant can then talk, are, a confirmation tone is played and the participant can then talk,
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Group chat is a common scenario for text messaging in which a Group chat is a common scenario for text messaging in which a
participant joins (or enters) a chat room in which text messages from participant joins (or enters) a chat room in which text messages from
participants are rendered in a single window and attributed to the participants are rendered in a single window and attributed to the
participant that sent the message. Changes in conference membership participant that sent the message. Changes in conference membership
are often announced in the text window itself (e.g. "Alice has just 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 entered the room. Bob has just departed."). Note that a real-time
transcription/closed captioning service can provide a similar window transcription/closed captioning service can provide a similar window
in which audio media is converted into interactive text. "Nick in which audio media is converted into interactive text. "Nick
names" or aliases are often chosen by participants or assigned by the names" or aliases are often chosen by participants or assigned by the
focus and used as handles within the room. Conferencing System and used as handles within the room.
4.8 Interactive text 4.8 Interactive text
Interactive text is using RTP to carry text one character at a time Interactive text is using RTP to carry text one character at a time
providing real-time interactivity, as described in RFC2793[2]. The providing real-time interactivity, as described in RFC2793[2]. The
interactive text session may be the main conference itself, or it may interactive text session may be the main conference itself, or it may
be used in conjunction with other media types. Interactive text may be used in conjunction with other media types. Interactive text may
be used to represent the audio in the conference using some be used to represent the audio in the conference using some
translation services. There can be more than one such stream where translation services. There can be more than one such stream where
each text stream is in a different language. These text streams may each text stream is in a different language. These text streams may
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4.10 Text sidebars 4.10 Text sidebars
Interactive text or instant messaging sidebars are perhaps the most Interactive text or instant messaging sidebars are perhaps the most
common sidebars in conferences today. Often the text sessions are common sidebars in conferences today. Often the text sessions are
separate from the conference. However, there are some advantages to 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 having text sessions be a sidebar and as a result a part of the main
conference. For example, a conference which is providing anonymity/ conference. For example, a conference which is providing anonymity/
aliases to participants can also provide anonymous/alias sidebars. A aliases to participants can also provide anonymous/alias sidebars. A
text sidebar can also benefit from other security/logging/recording text sidebar can also benefit from other security/logging/recording
services provided by the focus. services provided by the Conferencing System.
Another use of a text sidebar is a text-only conversation/discussion Another use of a text sidebar is a text-only conversation/discussion
between two or more conference participants who at the same time are between two or more conference participants who at the same time are
following the main conference. following the main conference.
4.11 Advanced media control features 4.11 Conference announcements
The following features can be used in all the conferencing scenarios.
Announcement - The conference moderator may be able to play The conference moderator may be able to play announcements to all the
announcements to all the conference participants. The announcement conference participants. The announcement may be pre-recorded or
may be pre-recorded or composed by the moderator before sending them. composed by the moderator before sending them. The announcements may
The announcements may be text, audio or audio visual. An example is be text, audio or audio visual. An example is a conference with
a conference with several audio break-out sessions going on. At some several audio break-out sessions going on. At some point in the
point in the time, the moderator wants to record an audio message time, the moderator wants to record an audio message like "in 5
like "in 5 minutes, everyone please come back to the main meeting" minutes, everyone please come back to the main meeting" and then play
and then play that message to all of the breakout sessions. that message to all of the breakout sessions.
5. Security Considerations 5. Security Considerations
Conferences generally have authorization rules about who may or may Conferences generally have authorization rules about who may or may
not join a conference, what type of media may or may not be used, not join a conference, what type of media may or may not be used,
etc. This information, sometimes called the conference policy, is etc. This information, sometimes called the conference policy or
used by the focus to admit or deny participation in a conference. common conference information, is used by the Conferencing System to
For the conference policy to be implemented, the focus needs to be admit or deny participation in a conference. For the conference
able to authenticate potential participants. The methods used will policy to be implemented, the Conferencing System needs to be able to
depend on the signaling protocols used by the focus. This can authenticate potential participants. The methods used depend on the
include a challenge/response mechanism, certificates, shared secret, signaling protocols used by the conference. This can include a
asserted identity, etc. These conference-specific security challenge/response mechanism, certificates, shared secret, asserted
requirements are discussed further in the XCON requirements and identity, etc. These conference-specific security requirements are
framework documents. discussed further in the XCON requirements and framework documents.
6. IANA Considerations 6. IANA Considerations
There are no IANA considerations associated with this specification. There are no IANA considerations associated with this specification.
7. Acknowledgements 7. Acknowledgements
Thanks to Brian Rosen for contributing conferencing scenarios. Thanks to Brian Rosen for contributing conferencing scenarios.
Thanks to Alan Johnston for going over the document and adding some Thanks to Alan Johnston for going over the document and adding some
more scenarios; to Keith Lantz for carefully reading the document. more scenarios; to Keith Lantz, Mary Barnes and Dave Morgan for
carefully reading the document.
8 Informative References 8. Informative References
[1] Rosenberg, J., "A Framework for Conferencing with the Session [1] Rosenberg, J., "A Framework for Conferencing with the Session
Initiation Protocol", Initiation Protocol",
draft-ietf-sipping-conferencing-framework-04 (work in progress), draft-ietf-sipping-conferencing-framework-04 (work in progress),
October 2003. October 2003.
[2] Hellstrom, G., "RTP Payload for Text Conversation", RFC 2793, [2] Hellstrom, G., "RTP Payload for Text Conversation", RFC 2793,
May 2000. May 2000.
[3] Barnes, M., Boulton, C., and O. Levin, "A Framework and Data
Model for Centralized Conferencing",
draft-barnes-xcon-framework-02 (work in progress),
February 2005.
Authors' Addresses Authors' Addresses
Roni Even Roni Even
Polycom Polycom
94 Derech Em Hamoshavot 94 Derech Em Hamoshavot
Petach Tikva 49130 Petach Tikva 49130
Israel Israel
EMail: roni.even@polycom.co.il Email: roni.even@polycom.co.il
Nermeen Ismail Nermeen Ismail
Cisco Systems, Inc. Cisco Systems, Inc.
170 West Tasman Drive 170 West Tasman Drive
San Jose 95134 San Jose 95134
CA USA CA USA
EMail: nismail@cisco.com Email: nismail@cisco.com
Intellectual Property Statement Intellectual Property Statement
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Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
 End of changes. 

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