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rfc:rfc4597

Network Working Group R. Even Request for Comments: 4597 Polycom Category: Informational N. Ismail

                                                   Cisco Systems, Inc.
                                                             July 2006
                       Conferencing Scenarios

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2006).

Abstract

 This document describes multimedia conferencing scenarios.  It
 describes both basic and advanced conferencing scenarios involving
 voice, video, text, and interactive text sessions.  These scenarios
 will help with the definition and evaluation of the protocols being
 developed in the centralized conferencing XCON working group.

Even & Ismail Informational [Page 1] RFC 4597 Conference Scenarios July 2006

Table of Contents

 1. Introduction ....................................................3
 2. Basic Conferencing Scenarios ....................................3
    2.1. Ad Hoc Conferences .........................................4
    2.2. Extension of a Point-to-Point Call to a Multipoint Call ....4
    2.3. Reserved Conferences .......................................4
 3. Advanced Conferencing Scenarios .................................5
    3.1. Extending a Point-to-Point Call to a Multipoint Call .......5
    3.2. Lecture Mode Conferences ...................................5
    3.3. Conference with Conference-Aware and Unaware Participants ..6
    3.4. A Reserved or Ad Hoc Conference with
         Conference-Aware Participants ..............................6
    3.5. Advanced Conference Features ...............................6
 4. Scenarios for Media Policy Control ..............................9
    4.1. Video Mixing Scenarios ....................................10
    4.2. Typical Video Conferencing Scenario .......................11
    4.3. Conference Sidebar Scenario ...............................11
    4.4. Coaching Scenario .........................................12
    4.5. Presentation and Q & A Session ............................12
    4.6. Presence-Enabled Ad Hoc Conference ........................13
    4.7. Group Chat Text Conferencing ..............................13
    4.8. Interactive Text ..........................................13
    4.9. Moderated Group Chat ......................................14
    4.10. Text Sidebars ............................................14
    4.11. Conference Announcements .................................14
 5. Security Considerations ........................................14
 6. Acknowledgements ...............................................15
 7. Informative References .........................................15

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1. Introduction

 This document describes multimedia conferencing scenarios.  The
 development of these scenarios is intended to help with the
 definition and evaluation of the requirements for the centralized
 conferencing (XCON) working group.  Although this document uses some
 definitions and conventions described in the SIP Conferencing
 Framework document [1], these scenarios are not specific to SIP.  The
 document describes basic and advanced conferencing scenarios.  The
 advanced scenarios assume that the user agents support the set of
 XCON protocols, identified in the Framework and Data Model for
 Centralized Conferencing [3], in order to take advantage of the
 conference functionality.  However, note that many of these features
 can be implemented today by using an interactive voice response (IVR)
 or web interface to control the conferencing application.
 The entities comprising the Conferencing System are the conference
 that is the center point for signaling and the participants.  The
 participant who initiated the conference is called the initiating
 participant.
 The scenarios described here demonstrate different conferencing
 services.  These services can be offered in a multimedia environment
 that benefits 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 to audio and video conferences.
 Multimedia conferences may include any combination of different media
 types such as audio, video, text, interactive text, or presentation
 graphics.  The conference scenarios are similar, but the media
 handling may be dependent on the media type.

2. Basic Conferencing Scenarios

 These scenarios enable a conference-unaware participant to create,
 join, and participate in a conference.  The participant may use out-
 of-band signaling to participate in a conference, but this is not
 mandatory.  The Conferencing System has all the functionality it
 needs in order to supply the service offered to the participants.
 Typical minimum requirements are that the participant support dual-
 tone multi-frequency (DTMF) tones/signal or provide voice responses
 to an IVR system.

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2.1. Ad Hoc Conferences

 A participant has a service provisioned to him that enables him to
 start an ad hoc conference when he calls the Conferencing System.
 When the participant wants to start a conference, he calls the
 conference service.  The participant may be identified by different
 means, including request destination, authenticated identity, 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 Conferencing System functionality and thus
 can create an ad hoc conference using his own user agent.  An example
 of such a conference is an audio conference initiated by a
 participant 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.  In the
 latter case, 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 Call to a Multipoint Call

 This is a basic case.  The initiating participant (PA) is in a
 point-to-point call with another participant (PB).  PA wants to add a
 third participant (PC) to the call.  PA cannot provide the
 Conferencing System functionality on his user agent nor can the other
 participant PB.  PA and PB do not support call transfer.  PA has a
 conferencing service that uses the methods described in 2.1.  PA
 conveys the conference information to PB in the point-to-point call.
 Both participants disconnect and call the Conferencing System.  The
 Conferencing System may support dial-out (for example, via DTMF),
 allowing the initiating participant PA to call the third party PC
 through the Conferencing System.

2.3. Reserved Conferences

 The reservation for this type of conference is typically done by an
 out-of-band mechanism in advance of the actual conference time.  The
 conference identification, which may be a URI or a phone number with
 a pin number, is allocated by the reservation system.  It is sent to
 all participants through email, IM, etc.  The participants join by
 using the conference identification.  The conference identification
 must be routable, enabling the allocation of a conference with free
 resources at the time when the conference actually runs.  The
 Conferencing System can also dial out to the conference participants.
 The participants may not be informed that they are in a conference,

Even & Ismail Informational [Page 4] RFC 4597 Conference Scenarios July 2006

 since their User Agent is not conference aware.  The participants may
 know, via announcement from the Conferencing System, that they are in
 a conference and who the other participants are.

3. Advanced Conferencing Scenarios

 These scenarios assume user agents that support at least call
 transfer service and a way to communicate information on events from
 the Conferencing System to the user agent.  The Conferencing System
 may have the ability to discover the capabilities of the
 participants, for example, whether they support call transfer.  This
 section specifies the dependencies in each scenario.  An advanced
 conference can be initiated only by a user agent that has 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

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

3.2. Lecture Mode Conferences

 This conference scenario enables a conference with a lecturer who
 presents a topic and can allow questions.  The lecturer needs to know
 who the participants are and needs to be able to give them the right
 to speak.  The right to speak can be based on floor control or an
 out-of-band mechanism.
 In general, the lecturer is seen/heard by the conference participants
 and often shares 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 has the option of selecting the appropriate language
 audio stream.  Multiple video streams could include the speaker's
 face and a whiteboard/demonstration stream.

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3.3. Conference with Conference-Aware and Unaware Participants

 A conference can include a mix of participants that are conference-
 aware and unaware.  Conference-unaware participants may be using a
 proxy function that proxies the advanced functionality between the
 different protocols and the Conferencing 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

 In order to start the conference, the initiating participant calls
 the Conferencing System using, for example, a unique identifier.  The
 Conferencing System may use some authenticating method to qualify the
 participant.  The other participants may call the Conferencing System
 and join the conference.  The Conferencing System is able to find the
 capabilities of the participants.  In case of a reserved conference,
 the Conferencing System starts the conference at the scheduled time.
 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
 privileges are for the initiating participant and for a regular
 participant; the initiating participant may delegate privileges to
 the other participants.  The privileges allow functionality as
 defined in the next section.

3.5. Advanced Conference Features

 The following features can be used in all the advanced 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.  This is not a requirement list, rather some examples
 of how specific functions may be used in a conference.
 o  Add Participants - A participant may add a new participant to the
    conference.  This can be done, for example, by instructing the
    Conferencing System to call the participant or by the first
    participant calling the new participant and pointing him to the
    conference.
 o  Delete Participant - A participant may delete participants from
    the conference if he can identify them.

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 o  Changing User Agent/Modes - During the course of a conference, a
    participant may switch between user agents 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 desktop phone.  Or a participant may join with a
    phone, discover that the conference has video streams available,
    and switch to a video phone.
 o  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 is
    unable to understand the conversation properly, and he learns that
    there is also an interactive text available.  He will ask to
    receive the text stream also.
 o  Authenticate participants - A participant can authenticate other
    participants who want to join the conference.  This can be done,
    for example, in a video conferencing session by creating a sidebar
    between the two participants, allowing the authenticating
    participant to talk with the new participant and verify his
    identity.
 o  Authorize participants - A participant can authorize other
    participants in order to allow them to join the conference.  This
    can be done implicitly by assigning a password to the conference
    or to each participant and letting the Conferencing System decide
    if the new participant is allowed to join.  The authorization can
    be done explicitly by directing the entered password to the
    initiating participant who will authorize each participant.  The
    conferencing system may use an authentication mechanism to
    authenticate the participants.
 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 to be
    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 - During the conference, the participant may
    want 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.

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 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 finished, the
    participants return to the main conference.  A sidebar may have
    the same functionality as the main conference.  There can be
    several sidebar scenarios:
    1.  A basic sidebar requires that two participants have the
        capability to have two calls at the same time, with a point-
        to-point call in parallel to the main conference.  It is user
        agent implementation-specific whether both calls' streams are
        mixed automatically or the participants are allowed to
        manually switch between them.
    2.  A conferencing-system-based sidebar uses the Conferencing
        System to create the sidebar and compose the relevant sidebar
        stream mixes.  These mixes can include the main conference as
        an incoming stream to the mix.  Mechanisms to signal the
        creation of the sidebar, invite participants, and control the
        mixes should be available.
        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.  As 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 cannot 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
    want to distribute this new media to all the participants.  The
    participant asks the Conferencing System to start the new media
    channel and to allow him to send data in the new channel.

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 o  Audio-only participants - In a multimedia conference, some of the
    participants who want to join may have no way to send and receive
    all the media types.  Typically, they can send and receive audio.
    Such participants join the conference as audio-only participants.
    The general case is that participants may send and receive only
    part of the media streams available in the multimedia conference.
 o  Passive participants - In a conference, some participants may be
    listeners to all or part of the media streams, but may be
    invisible to all other participants.
 o  Recorders - A recorder can be added to the conference.  A recorder
    can record all streams or a subset of the streams.  Recorders may
    be turned on and off during the conference.  Recorders may be used
    for a "role call" scenario in order to record a participant's
    name.  This name can be announced at a later stage automatically
    or based on a participant request.  A recorder is a case of a
    passive participant.
 o  Whisper/Private Message - A participant can send a one-way message
    (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 participant may ask for assistance from a human
    operator during the conference.

4. Scenarios for Media Policy Control

 During a conference, media streams may be controlled by authorized
 participants using either a media control protocol or a third-party
 application.  This section describes some typical media control
 scenarios.  The conference can be of any size.  Some of the media
 control scenarios are typical of specific conference sizes.  As a
 general 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 participants may be put on hold and get "music on hold".
 The scenarios apply to audio conferences as well as to multimedia
 conferences.  In the sections below, there is some specific
 information about the mixed video layout and interactive text.

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4.1. Video Mixing Scenarios

 For video, the participant selects one of a set of predefined video
 presentations offered by the server.  Each video presentation is
 identified by a textual description as well as an image specifying
 how the presentation appears on the screen.  In this scenario, by
 choosing a video presentation, the participant chooses how many video
 streams (participants) are 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
 and/or controlled by authorized participants.  It may also be
 possible to have multiple mixes per conference, possibly as many as
 there are participants.  (Note that the same flexibility may be
 afforded to audio mixes as well.)
 The following is a list of typical video presentations.  Other
 layouts are available today in commercial products.
  1. Single view: This presentation typically shows the video of the

loudest speaker.

  1. 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 windows, with no altered aspect ratio.  Thus,
       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.  Thus,
       blanking parts of the image is not necessary.  The mixer
       handles the cropping of the images.
   3.  One window above the other, with no altered aspect ratio.
   4.  One window above the other, with altered aspect ratios.
  1. Quadrate view: This presentation shows 4 streams. If the streams

are multiplexed into one image (centralized server), they are

   arranged in a 2x2 style.  Note that in this style the aspect ratios
   are maintained.
  1. 9 sub-picture view: This presentation shows 9 streams. If the

streams are to be multiplexed in one image, they are arranged in a

   3x3 style.  In the multiplexing case, cropping is performed under
   the discretion of the mixer.

Even & Ismail Informational [Page 10] RFC 4597 Conference Scenarios July 2006

  1. 16 sub-picture view: This presentation shows 16 streams. If the

streams are to be multiplexed into one image, they are arranged in

   a 4x4 style.  In this style, the aspect ratios are maintained, and
   no cropping or blanking is needed.
  1. 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 4/9 of the screen while each
   of the other five occupies 1/9 of the screen.

4.2. Typical Video Conferencing Scenario

 This scenario is known as voice-activated video switch.  Every
 participant hears the N loudest participants but does not hear
 himself.  All the participants see the loudest speaker; the loudest
 speaker may see the previous loudest speaker.  This mode is typical
 for a small conference.
 A participant with proper authorization can exclude one or more
 participants from the audio or video mix.  An indication that they
 are not being seen/heard might be displayed to the affected
 participants.
 A participant with proper authorization can manipulate the gain level
 associated with one or more audio streams in the mix.

4.3. Conference Sidebar Scenario

 An authorized participant creates a sidebar.  The participant 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.
 A participant 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 is just a participant of the sidebar, the participant
 only receives the sidebar media without the media of the main
 conference.
 A participant with the right authorization can move another
 participant into the sidebar with no indication, in which case the
 participant suddenly starts receiving the sidebar media.
 Sidebar participants with the right authorization can select to hear
 or not to hear the main conference audio mixed with the sidebar
 audio.

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 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.

4.4. Coaching Scenario

 This is a call center or a remote training session where there is a
 supervisor who can monitor the conference.  The supervised
 participants may be the call center operators or the teachers.  A
 participant in the conference may be a supervised participant or a
 "customer".
 The supervisor is a hidden participant and is not part of the
 participant roster.
 The supervised participants might get an announcement/tone indicating
 that the supervisor has joined.  The other participants do not hear
 the announcement.
 The supervisor listens to or sees the session but can only be heard
 or seen by the supervised participant.
 The supervisor can become a normal participant, in which case the
 participants see the supervisor as part of the roster and start
 hearing and seeing him.

4.5. Presentation and Q & A Session

 An example is an earning call scenario in which a group of presenters
 delivers material to a group of people.  After the presentation is
 finished, a Q & A session is opened.
 The conference is created as a panel, and the panel participants are
 identified.  Only their streams are mixed.
 After the end of the presentation, the session chair changes the
 conference type to normal, and now streams from all participants may
 be mixed.  Alternatively, a floor control protocol can be used.  The
 chair can grant the right to speak by adding the participant, whose
 turn it is to ask a question, to the conference mix.

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4.6. Presence-Enabled Ad Hoc Conference

 A presence-enabled ad hoc conference, sometimes described as "walkie
 talkie" service, 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, 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; as a result, the media is 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.  Floor control can be
 used to allow other participants to speak, as the conference is
 usually half-duplex in nature.

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
 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 into interactive text.  "Nicknames"
 or aliases are often chosen by participants or assigned by the
 Conferencing System and used as handles within the room.

4.8. Interactive Text

 Interactive text uses RTP to carry text one character at a time,
 providing real-time interactivity, as described in RFC 4103 [2].  The
 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 to represent the audio in the conference using some
 translation services.  There can be more than one such stream where
 each text stream is in a different language.  These text streams may
 be used as subtitles to the audio stream.  The translation from to
 text to speech and back is done by transcoders.  These transcoders
 have similar functionality to transcoders between different audio or
 video algorithms.
 The conference participants should be able to select to receive text
 streams with the conference audio or those without it.

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4.9. Moderated Group Chat

 A moderated group chat scenario for text messaging is similar to
 group chat, but all text messages sent to the group are 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).

4.10. Text Sidebars

 Interactive 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 that 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 Conferencing System.
 Another use of a text sidebar is a text-only conversation/discussion
 between two or more conference participants who are following the
 main conference at the same time.

4.11. Conference Announcements

 The conference moderator may be able to play announcements to all the
 conference participants.  An announcement may be prerecorded or
 composed by the moderator before it is sent.  The announcements may
 be text, audio, or audio-visual.  An example is a conference with
 several audio break-out sessions going on.  At some point, 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 the breakout sessions.

5. Security Considerations

 Conferences generally have authorization rules about who may or may
 not join a conference, what type of media may or may not be used,
 etc.  This information, sometimes called the conference policy or
 common conference information, is used by the Conferencing System to
 admit or deny participation in a conference.  For the conference
 policy to be implemented, the Conferencing System needs to be able to
 authenticate potential participants.  The methods used depend on the
 signaling protocols used by the conference.  This can include a
 challenge/response mechanism, certificates, shared secret, asserted
 identity, etc.

Even & Ismail Informational [Page 14] RFC 4597 Conference Scenarios July 2006

 Conferences often require that their content be confidential.  In
 addition, secure authorization of participants is incomplete if
 access to the media can be gained by unauthorized participants.
 Functions for securing the media and for key management and
 distribution to authorized participants need to be provided by the
 Conferencing System.  In some cases, the functions used for
 participant authorization can be leveraged for this purpose.
 Privacy is an important aspect of conferencing.  Users may wish to
 join a conference without anyone knowing that they have joined, in
 order to silently listen in.  In other applications, a participant
 may wish just to hide their identity from other participants, but
 otherwise let them know of their presence.  These functions need to
 be provided by the Conferencing System.
 These conference-specific security requirements are discussed further
 in the XCON framework document.

6. Acknowledgements

 Thanks to Brian Rosen for contributing conferencing scenarios.
 Thanks to Alan Johnston for going over the document and adding some
 more scenarios; to Keith Lantz, Mary Barnes, and Dave Morgan for
 carefully reading the document.

7. Informative References

 [1]  Rosenberg, J., "A Framework for Conferencing with the Session
      Initiation Protocol (SIP)", RFC 4353, February 2006.
 [2]  Hellstrom, G. and P. Jones, "RTP Payload for Text Conversation",
      RFC 4103, June 2005.
 [3]  Barnes, M., "A Framework and Data Model for Centralized
      Conferencing", Work in Progress, June 2006.

Even & Ismail Informational [Page 15] RFC 4597 Conference Scenarios July 2006

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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 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Even & Ismail Informational [Page 17]

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