XCONNetwork Working Group R. EvenInternet-DraftRequest for Comments: 4597 PolycomExpires: March 10, 2006Category: Informational N. Ismail Cisco Systems, Inc.September 6, 2005July 2006 Conferencing Scenariosdraft-ietf-xcon-conference-scenarios-05.txtStatus ofthisThis MemoBy submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents ofThis memo provides information for the InternetEngineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time.community. Itis inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The listdoes not specify an Internet standard ofcurrent Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The listany kind. Distribution ofInternet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 10, 2006.this memo is unlimited. Copyright Notice Copyright (C) The Internet Society(2005).(2006). Abstract This document describes multimedia conferencing scenarios. It describes both basic and advanced conferencing scenarios involving voice, video,texttext, and interactive text sessions. Theseconferencingscenarios will help with the definition and evaluation of the protocols being developed in the centralized conferencing XCON working group. Table of Contents 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 3....................................................3 2. Basic Conferencingscenarios . . . . . . . . . . . . . . . . . 3Scenarios ....................................3 2.1.Ad-hoc conference . . . . . . . . . . . . . . . . . . . . 4Ad Hoc Conferences .........................................4 2.2. Extension of aPoint to point callsPoint-to-Point Call to amultipoint call . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Multipoint Call ....4 2.3. Reservedconference . . . . . . . . . . . . . . . . . . . 4Conferences .......................................4 3. Advanced Conferencingscenarios . . . . . . . . . . . . . . . 5Scenarios .................................5 3.1. Extending apoint-to-point callPoint-to-Point Call to amultipoint call . . . 5Multipoint Call .......5 3.2. Lecturemode conferences . . . . . . . . . . . . . . . . . 5Mode Conferences ...................................5 3.3. Conference withconference awareConference-Aware andunaware participants . . . . . . . . . . . . . . . . . . . . . . . 6Unaware Participants ..6 3.4. AreservedReserved orad-hoc conferenceAd Hoc Conference withconference-aware participants. . . . . . . . . . . . . . . . . . . . . . . 6Conference-Aware Participants ..............................6 3.5. Advancedconference features . . . . . . . . . . . . . . . 6Conference Features ...............................6 4. Scenarios formedia policy control . . . . . . . . . . . . . . 9Media Policy Control ..............................9 4.1. Videomixing scenarios . . . . . . . . . . . . . . . . . . 9Mixing Scenarios ....................................10 4.2. Typicalvideo conferencing scenario . . . . . . . . . . . 10Video Conferencing Scenario .......................11 4.3. Conference Sidebarscenario . . . . . . . . . . . . . . . 11Scenario ...............................11 4.4. Coachingscenario . . . . . . . . . . . . . . . . . . . . 11Scenario .........................................12 4.5. Presentation andQA session . . . . . . . . . . . . . . . 12Q & A Session ............................12 4.6.Presence-enabled ad-hoc conference . . . . . . . . . . . . 12Presence-Enabled Ad Hoc Conference ........................13 4.7. Groupchat text conferencing . . . . . . . . . . . . . . . 12Chat Text Conferencing ..............................13 4.8. Interactivetext . . . . . . . . . . . . . . . . . . . . . 13Text ..........................................13 4.9. Moderatedgroup chat . . . . . . . . . . . . . . . . . . . 13Group Chat ......................................14 4.10. Textsidebars . . . . . . . . . . . . . . . . . . . . . . 13Sidebars ............................................14 4.11. Conferenceannouncements . . . . . . . . . . . . . . . . . 13Announcements .................................14 5. Security Considerations. . . . . . . . . . . . . . . . . . . 14........................................14 6.IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 7.Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . 14 8................................................15 7. Informative References. . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . . . . 16.........................................15 1. Introduction This document describes multimedia conferencing scenarios. The development of theseconferencingscenarios 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 Frameworkdocument[1],document [1], these scenarios are notSIP-specific.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 anIVRinteractive 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 isreferenced ascalled the initiating participant. The scenarios described here demonstrate different conferencing services. Theseconferencingservices can be offered in a multimedia environment thatbenefitbenefits from having some support in the user agents that enable more robust andeasier to useeasier-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 multimediaexamplesexamples, but they are applicable to audio only as well asforto audio and video conferences. Multimedia conferences may include any combination of different media typeslikesuch as audio, video, text, interactive text, or presentation graphics. The conference scenarios aresimilarsimilar, but the media handling may be dependent on the media type. 2. Basic ConferencingscenariosScenarios These scenarios enable aconference unawareconference-unaware participant to create,joinjoin, and participate in a conference. The participant may useout of bandout- of-band signaling to participate in aconferenceconference, but this is nota mandatory requirement.mandatory. The Conferencing System has all the functionality it needs in order to supply the service offered to the participants.A typicalTypical minimumrequirement isrequirements are that the participant supportDTMFdual- tone multi-frequency (DTMF) tones/signal or provide voice responses to an IVR system. 2.1.Ad-hoc conferenceAd Hoc Conferences A participant has a service provisioned to him that enables him to start anad-hocad hoc conference when he calls the Conferencing System. When the participant wants to start aconferenceconference, he calls the conference service. The participant may be identified by differentmeansmeans, 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 havethe functionality of aConferencing System functionality and thus can createad-hocan ad hoc conference using his own useragent functionality.agent. An example of such a conference is an audio conference initiated byone of the participantsa 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 thisURIURI, 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 aPoint to point callsPoint-to-Point Call to amultipoint callMultipoint Call This is a basic case. The initiating participant (PA) is in apoint to pointpoint-to-point call with another participant (PB). PA wants to add a third participant (PC) to the call.The initiating participant (PA)PA cannot provide the Conferencing System functionality on his user agent nor can the other participant(PB).PB. PA and PB do notsupportssupport call transfer. PA has a conferencing serviceusingthat uses the methods described in 2.1. PA conveys the conference information to PB in thepoint-to- pointpoint-to-point call. Bothparticipantparticipants disconnect and call the Conferencing System. The Conferencing System may supportdial out, for exampledial-out (for example, viaDTMF,DTMF), allowing the initiating participant PA to call the third party PC through the Conferencing System. 2.3. ReservedconferenceConferences The reservation for this type of conference is typically done by anout of bandout-of-band mechanismandin 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 participantsusingthrough email, IM, etc. The participants join by using the conference identification. The conference identification must beroutableroutable, enabling the allocation of a conference with free resources at the time when the conference actuallyrun.runs. The Conferencing System can also dial out to the conference participants. The participants may not be informed that they are in aconferenceconference, 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 ConferencingscenariosScenarios 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,to identify ifwhether they support call transfer. This section specifies the dependencies in eachscenario the dependencies.scenario. An advanced conference can be initiated only byana user agent that has advanced features, but some user agents in the conference may have less functionality. 3.1. Extending apoint-to-point callPoint-to-Point Call to amultipoint callMultipoint Call The initiating participant PA is in a point-to-point call and wants to add a third participant.The initiating participantPA can start a multipoint call on a conferencing bridge known to him. The extension can be without consultation, which means thathePA moves thepoint-to- pointpoint-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 thathePA puts his current party on hold, calls the thirdparty andparty, asks him to join the conference, and then transfers all the participants to the Conferencing System. 3.2. Lecturemode conferencesMode 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 anout of bandout-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. 3.3. Conference withconference awareConference-Aware andunaware participantsUnaware Participants A conference can includeparticipants that area mix ofconferenceparticipants that are conference- aware andunaware participants. Thoseunaware. Conference-unaware participants may beconference unaware participantsusing 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. AreservedReserved orad-hoc conferenceAd Hoc Conference withconference-aware participants. TheConference-Aware Participants In order to start the conference, the initiating participant calls the Conferencing System using, for example, a uniqueidentifier in order to start the conference.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 reservedconferenceconference, the Conferencing System starts the conference at the scheduled time. The participants may join by calling the conferenceURIURI, 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. Advancedconference featuresConference 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 afunctionalityfunctionality, 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. 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 adesk topdesktop 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 theconferenceconference, 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 conversationproperlyproperly, and he learns that there is also an interactive textavailable, heavailable. He will ask to receivealsothe textstream.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 twoparticipantsparticipants, 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.theThe 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 theconferenceconference, 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 restareto 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 -The participant may want, duringDuring 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. 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 isdonefinished, the participants return to the main conference. A sidebar may have the same functionality as the main conference. There can be severalsidebarssidebar scenarios: 1.BasicA basic sidebaris based on the capabilities ofrequires that two participants have the capability to have two calls at the same time, with apoint to pointpoint- to-point call in parallel to the main conference. It is user agentimplementation specificimplementation-specific whetherto automatically mixbothcall'scalls' streams are mixed automatically orallowtheparticipantparticipants are allowed to manually switch between them. 2.Conferencing System basedA 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, inviteparticipantsparticipants, 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.AnotherAs another example, a sidebar can have a different media type from the mainconference;conference: a video call can have an audio sidebar where the other participants can see the sidebar participants talking butcan notcannot hear them; or an audio or video conference may have a text sidebar. o Conference information - When a participant joins theconferenceconference, 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 andad-hocad 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. o Audio-only participants - In a multimediaconferenceconference, some of the participants who want to join may have no way to send and receive all the media types.TypicallyTypically, 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 themulti mediamultimedia conference. o Passive participants - In aconferenceconference, some participants may be listeners to all or part of the media streams, but may be invisible to alltheother 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 aparticipantparticipant'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 aone wayone-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 formedia policy controlMedia Policy Control During aconferenceconference, media streams may be controlled by authorized participants using either a media control protocol or athird partythird-party application. This section describes some typical media control scenarios. The conference can be of any size. Some of the media control scenarios are typicaltoof specific conference sizes. As a generalrulerule, 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, earlyparticipantparticipants may be put on hold and get "music on hold". The scenarios apply to audio conferences as well as to multimedia conferences.There areIn the sections below, there is some specific information about the mixed video layout andaboutinteractivetext discussed below.text. 4.1. Videomixing scenariosMixing Scenarios Forvideovideo, the participant selects one of a set ofpre-definedpredefined 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 thisscenarioscenario, by choosing a videopresentationpresentation, 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 aswell.).well.) The followingareis a list of typical videopresentations; there are otherpresentations. Other layouts are available today in commercialproducts:products. - Single view: This presentation typically shows the video of the loudestspeakerspeaker. - DualView:view: This presentation shows two streams. If the streams are to be multiplexed in one image (typical of centralizedservers)servers), the multiplexing can be: 1.Side by sideSide-by-side windows, with no altered aspectratio and henceratio. Thus, blanking of parts of the image might be necessary if the streams are to be combined as one image. 2.Side by side windowsSide-by-side windows, with altered aspectratios and henceratios. Thus, blanking parts of the image is not necessary. The mixer handles the cropping of the images. 3. One window above theother windowsother, with no altered aspectratioratio. 4. One window above theother windowsother, with altered aspectratioratios. - Quadrate view: This presentation shows 4 streams. If the streams are multiplexed into one image (centralizedserver)server), they are 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 oneimageimage, they are arranged in a 3x3 style. In the multiplexingcasecase, 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 oneimageimage, they are arranged in a 4x4 style. In thisstylestyle, the aspect ratios aremaintainedmaintained, 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 oneimageimage, then the pictures are laid so that one sub-window occupies 4/9 of the screen while each of the other fiveoccupyoccupies 1/9 of thescreen each.screen. 4.2. Typicalvideo conferencing scenarioVideo Conferencing Scenario This scenario is known asvoice activatedvoice-activated video switch. Every participant hears the N loudest participants buthedoes not hear himself. All the participants see the loudest speaker; the loudest speaker may see the previous loudest speaker. This mode is typicaltofor 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 affectedparticipants indicating that they are not being seen/heard.participants. A participant with proper authorization can manipulate the gain level associated with one or more audio streams in the mix. 4.3. Conference SidebarscenarioScenario An authorized participant creates aside bar.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 thesidebarsidebar, 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 suddenlystartstarts 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 sidebaraudioaudio. 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. CoachingscenarioScenario This is a call center or a remote training session where there is a supervisor who can monitor the conference.There are theThe supervised participantsthatmay 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 andQA sessionQ & A Session An example is an earning call scenario in which a group of presentersdeliverdelivers material to a group of people. After the presentation isfinishedfinished, aQAQ & A session is opened. The conference is created as apanelpanel, and the panel participants are identified. Only their streams are mixed. After the end of thepresentationpresentation, the session chair changes the conference type tonormalnormal, and now streams from all participants may be mixed.AlternativelyAlternatively, 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. 4.6.Presence-enabled ad-hoc conferencePresence-Enabled Ad Hoc Conference A presence-enabledad-hocad 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 isplayedplayed, and the participant can thentalk, which results intalk; as a result, the mediabeingis 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. Thead-hocad 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. Groupchat text conferencingChat 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.(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."Nick names""Nicknames" or aliases are often chosen by participants or assigned by the Conferencing System and used as handles within the room. 4.8. InteractivetextText Interactive textis usinguses RTP to carry text one character at atimetime, providing real-time interactivity, as described inRFC2793[2].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.Those transcoderThese transcoders have similar functionality to transcoders between different audio or video algorithms. The conference participants should be able to select to receivethosetext streams with the conference audio or those without it. 4.9. Moderatedgroup chatGroup Chat A moderated group chat scenario for text messaging is similar to groupchatchat, butwithall text messages sent to the groupbeing filtered/approvedare 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.(e.g., provide warnings before removal). 4.10. TextsidebarsSidebars 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 conferencewhichthat 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 whoat the same timeare following the mainconference.conference at the same time. 4.11. ConferenceannouncementsAnnouncements The conference moderator may be able to play announcements to all the conference participants.TheAn announcement may bepre-recordedprerecorded or composed by the moderator beforesending them.it is sent. The announcements may be text,audioaudio, oraudio visual.audio-visual. An example is a conference with several audio break-out sessions going on. At somepoint in the time,point, the moderator wants to record an audio message like"in"In 5 minutes, everyone please come back to the main meeting" and then play that message to allofthe 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. 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 XCONrequirements andframeworkdocuments.document. 6.IANA Considerations There are no IANA considerations associated with this specification. 7.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, MaryBarnesBarnes, and Dave Morgan for carefully reading the document.8.7. Informative References [1] Rosenberg, J., "A Framework for Conferencing with the Session InitiationProtocol", draft-ietf-sipping-conferencing-framework-04 (work in progress), October 2003.Protocol (SIP)", RFC 4353, February 2006. [2] Hellstrom,G.,G. and P. Jones, "RTP Payload for Text Conversation", RFC2793, May 2000.4103, June 2005. [3] Barnes, M.,Boulton, C., and O. Levin,"A Framework and Data Model for Centralized Conferencing",draft-barnes-xcon-framework-02 (workWork inprogress), February 2005.Progress, June 2006. Authors' Addresses Roni Even Polycom 94 Derech Em Hamoshavot Petach Tikva 49130 IsraelEmail:EMail: roni.even@polycom.co.il Nermeen Ismail Cisco Systems, Inc. 170 West Tasman Drive San Jose 95134 CA USAEmail:EMail: nismail@cisco.com Full Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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