XCON R. Even Internet-Draft Polycom Expires: November 30, 2004 N. Ismail Cisco Systems, Inc. June 2004 Conferencing Scenarios
draft-ietf-xcon-conference-scenarios-01.txtdraft-ietf-xcon-conference-scenarios-02.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering 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. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on November 30, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document describes multimedia conferencing scenarios. It describes both basic and advance conferencing scenarios involving voice, video, text and interactive text sessions. These conferencing scenarios 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 2. Simple Conferencing scenarios . . . . . . . . . . . . . . . 3 2.1 Ad-hoc conference . . . . . . . . . . . . . . . . . . . . 4 2.2 Extension of a Point to point calls to a multipoint call . 4 2.3 Reserved conference . . . . . . . . . . . . . . . . . . . 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 simple and advanced participants . . . . . 5 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 . . . . . . . . . . . . . 8 4.1 Video mixing scenarios . . . . . . . . . . . . . . . . . . 9 4.2 Typical video conferencing scenario . . . . . . . . . . . 10 4.3 Conference Sidebar scenario . . . . . . . . . . . . . . . 10 4.4 Coaching scenario . . . . . . . . . . . . . . . . . . . . 11 4.5 Presentation and QA session . . . . . . . . . . . . . . . 11 4.6 Presence enabled ad-hoc conference . . . . . . . . . . . . 12 4.7 Group chat text conferencing . . . . . . . . . . . . . . . 12 4.8 Interactive text . . . . . . . . . . . . . . . . . . . . . 12 4.9 Moderated group chat . . . . . . . . . . . . . . . . . . . 13 4.10 Text sidebars . . . . . . . . . . . . . . . . . . . . . 13 4.11 Advanced media control features . . . . . . . . . . . . 13 5. Security Considerations . . . . . . . . . . . . . . . . . . 13 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . 14 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 8. Informative References . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . 15 1. Introduction This document describes multimedia conferencing scenarios. The development of these conferencing scenarios is intended to help with definition and evaluation of the requirements for the centralized conferencing (XCON) working group. Although this document uses definitions, conventions and architectures described in the SIP Conferencing Framework document, these scenarios are not SIP-specific. The document describes basic and advance conferencing scenarios. The advanced scenarios will assume that the endpoint functionality is based on the future set of XCON protocols that will be needed in order to participate in the conference and take advantage of the conference functionality. However, note that many of these features can be implemented today using an IVR or web interface to control the conferencing application. The entities comprising the conference will be the "focus" that is the center point for signaling and the participants. A special participant is the participant who initiated the conference. The scenarios described are to demonstrate different conferencing services that can be offered in 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 applicable to audio only as well as for audio and video conferences. Multimedia conferences may include any combination of different media types like audio, video, text, interactive text, or presentations graphics. The conference scenarios are similar but the media handling may be dependent on the media type. 2. Simple Conferencing scenarios These scenarios enable a basic endpoint without any specific conferencing extensions to create, join and participate in a conference. The endpoint may use out of band signaling to participate in a conference but this is not a mandatory requirement. The focus will have all the functionality it needs in order to supply the service offered to the participants. A typical minimum requirement is that the participant support DTMF tones/signal or provide voice responses to an IVR system. 2.1 Ad-hoc conference A user has a service provisioned to him that enables him to start an ad-hoc conference when he calls the focus. When the participant wants to start a conference he calls the conference service. The participant may be identified by different means including 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 the functionality of a focus and thus can create ad-hoc conference using his own endpoint functionality. An example of such a conference is an audio conference initiated by one of the participants who has a conference service that enables him to start a conference when he calls a specific URI. The conference may be created by the first person calling this URI or it may be created only after the owner is authenticated using an IVR system, the other participants may get an announcement and are placed on hold if they call the conference before the owner. 2.2 Extension of a Point to point calls to a multipoint call This is a simple case. The initiating participant is in a call with one party and wants to add another party to the call. The initiating participant cannot provide the focus functionality on his endpoint nor can the other participant. If neither also support call transfer, the only way to create this conference is by disconnecting and using the methods described in 2.1. The information about the conference will be conveyed in the point-to-point call. The focus may support dial out allowing the initiating participant to call the third party. 2.3 Reserved conference The reservation for this type of conference is typically done by an out of band mechanism and 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 using email, IM, etc. The participants join using the conference identification. The conference identification must be routable enabling the allocation of a focus with free resources at the time when the conference will actually run. The focus can also dial out to the conference participants. The endpoints may not be aware that they are in a conference. The participants may know via announcement from the conference that they are in a conference and who are the other participants. 3. Advanced Conferencing scenarios These scenarios will assume endpoints that support at least call transfer service and a way to communicate information on events from the focus to the endpoint. The focus has the ability to discover the capabilities of the participants, to identify if they support the call transfer. This section will specify in each scenario the dependencies. An advance conference can be initiated by a endpoint that has advanced features but some endpoints in the conference may have less functionality. 3.1 Extending a point-to-point call to a multipoint call The initiating participant is in a point-to-point call and want to add a third participant. The initiating participant can start a multipoint call on a conferencing bridge known to him. The extension can be without consultation, which means that he moves the point-to-point call to the focus and then adds the third party (this can be done in various ways). The extension can be done with consultation, which means that he puts his current party on hold calls, the third party and asks him to join the conference and then transfers all the participants to the conferencing bridge. 3.2 Lecture mode conferences This conference scenario enables a conference with a lecturer that present a topic and can allow questions. The lecturer needs to know who are the participants and to be able to give them the right to speak. The right to speak can be based on floor control but can also be based on an out of band mechanism. In general, the lecturer will be seen/heard by the conference participants and often will share a presentation or application with the other participants. A participant joining this type of conference can get the identity of the lecturer and often the identities of the audience participants. This type of conference may have multiple media streams. For example, if simultaneous language translation is available, a participant will have the option of selecting the appropriate language audio stream. Multiple video streams could include the speaker's face and a whiteboard/demonstration stream. 3.3 Conference with simple and advanced participants A focus can include participants that are a mix of simple and advanced participants. Those participants may be basic participants or the GW function may proxy the advanced functionality between the different protocols and the focus. For example, an IVR system or a web page interface can be used to provide additional functionality. 3.4 A reserved or ad-hoc conference with conference aware participants. The initiating participant will call the focus using for example a unique identifier in order to start the conference. The focus may use some authenticating method to qualify the participant. The other participants may call the focus and join the conference. The focus will be able to find the capabilities of the participants. In case of a reserved conference the focus will start the conference at the scheduled time. The participants may join by call the conference URI or the focus may call them. The conference may have privilege levels associated with a specific conference or participant. The privileges will be for the initiating participant and for a regular participant; the initiating participant may delegate privileges to the other participants. The privileges will allow functionality as defined in the next section. 3.5 Advanced conference features The following scenarios can be used in all the advance conferencing scenarios. In the examples given in this section, when referring to a participant that has a functionality it means a participant with the right privileges. These scenarios may be available in the advanced conferencing scenarios and are common in many conferencing applications. This is not a requirement list but some examples of how specific functionality are being used in a conference. Add Participants - A participant may add a new participant to the focus. This can be done, for example, by instructing the focus to call the participant or by the participant calling the 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 get also the text stream. The text sidebar may be using RFC 2973 interactive text. Authenticate participants - A participant can authenticate other participants that want to join the focus. This can be done implicitly by assigning a password to the conference and letting the focus authenticate the new participants or explicitly by directing the authentication requests to the initiating participant who will authenticate each user. Controlling the presentation of media - during the conference the participant may be able to manage whose media is being sent to each participant. For example the participant may be able to decide that he wants to be the speaker and all the rest are listeners he may also specify whose media he wants to receive. The participant may be able to mute a media stream during the conference. Giving privileges - the participant may want, during the conference, to give a privilege to another participant. The assigning of privileges may be implicit when requested or explicit by asking the participant to grant a privilege. Side conferences or sidebars - the participant may want to create a side conference that include some of the participants. When the side conference is done the participants will return to the main conference. A side bar may have the same functionality as the main conference. There can be some sidebars scenarios. The simple one will be based on capabilities of two participants to have two calls at the same time and they will have a point to point call in parallel to the main conference, it is an end point implementation to decide if to mix both calls streams or to enable the user to switch between them. The sidebar scenario that will use the focus will use the same call he is in and let the focus create the sidebar and compose the relevant sidebar stream mixes. These mixes can include the main conference as an incoming stream to the mix. A way to signal the creation of the sidebar and how to invite participants and control the mixes should be available. For example, participants in an audio sidebar can generally not be heard by the rest of the conference. However, the main conference audio may be mixed in the sidebar, but at a low volume, or in a different channel. A sidebar can 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. Focus information - When a participant joins the focus he is announced to the participants. An announcement may be available when he leaves the focus. The participants may query the focus for its current participants. This presence information can be used by applications. Extending of a conference - Reserved conferences and ad-hoc conferences may have a time limit. The focus will inform the participants when the limit is close and may allow the extension of the conference. Adding and removing a media type to the conference - a participant may want to start a power point presentation during a conference. He may want to distribute this new media to all the participants. The participant will request from the focus to start the new media channel and to allow him to send data in the new channel. Audio only participants - In a multimedia conference some of the users who want to join has no way to send and receive all the media types. Typically they can send and receive audio. Such participants will join the conference as audio only participants. The general case is that users may send and receive only part of the media streams available in the multi media conference. Passive participants - In a conference some participants may be listeners to all or part of the media streams. They may be invisible to all the other participants. Recorders - A recorder can be added to the conference. A recorder can record all streams or a subset of the streams. A recorder is a case of a passive participant. Whisper/Private Message - A participant can send 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. 4. Scenarios for media policy control During a conference media streams may be controlled by authorized users using either a media control protocol or a third party application. This section will describe some typical media control scenarios. The conference can be of any size starting from small conferences (3-5 participants) through medium size of up to 16 participants and large conferences. Some of the media control scenarios are typical to specific conference size. As a general rule larger conferences scenarios tend to be more centrally managed or structured. The scenarios apply to audio conferences as well as to multimedia conferences. There are some specific information about the mixed video layout and about interactive text discussed bellow. 4.1 Video mixing scenarios For video the user selects one of a set of pre-defined video presentations offered by the server. Each video presentation is identified by a textual description as well as an image specifying how the presentation looks like on the screen. In this scenario by choosing a video presentation the user chooses how many video streams (participants) will be viewed at once and the layout of these video streams on the screen. The contents of each sub-window can be defined by a conference policy or controlled by authorized participants. In other aspects like number of different mixes in the conference and a custom mix for each user, these functionality are similar to audio mixing and are based on server capabilities and authorization. Note that for non-centralized mixing if the endpoint mixer does not support the media presentation of the conference, the participant can get the default media presentation offered by the endpoint mixer. The following are a list of typical video presentations; there are other layouts available today in commercial products: - Single view: This presentation typically shows the video of the loudest speaker - Dual View: This presentation shows two streams. If the streams are to be multiplexed in one image (typical of centralized servers) the multiplexing can be: 1. Side by side with no altered aspect ratio and hence blanking of parts of the image might be necessary if the streams are to be combined as one image. 2. Side by side windows with altered aspect ratios and hence blanking parts of the image is not necessary. The mixer handles the cropping of the images. 3. One above the other windows with no altered aspect ratio 4. One above the other windows with altered aspect ratio - Quadrate view: This presentation shows 4 streams. If the streams are to be multiplexed into one image (centralized server) they will be arranged in a 2x2 style. Note that in this style the aspect ratios are maintained. - 9 sub-picture view: This presentation shows 9 streams. If the streams are to be multiplexed in one image they will be arranged in a 3x3 style. In the multiplexing case cropping is performed under the discretion of the mixer. - 16 sub-picture view: This presentation shows 16 streams. If the streams are to be multiplexed into one image they will be arranged in a 4x4 style. In this style the aspect ratios are maintained and no cropping or blanking is needed. - 5+1 sub-picture view: This presentation shows 6 streams. If the streams are to be multiplexed into one image then the pictures are laid so that one sub-window occupies four ninth of the screen while the other five occupy a ninth of the screen each. 4.2 Typical video conferencing scenario In this scenario the audio is typically an n-1 audio mixing. Every participant will get a mixed audio of N loudest participants but his own audio will not be part of the received mix. All the participants will see the current speaker and he will see the previous speaker. This mode is typical to small conference. User with correct authorization can exclude one or more users from the audio or video mix. An indication might be displayed to the affected users indicating that they are not being seen/heard. User with correct authorization can manipulate the gain level associated with one or more audio streams in the mix. 4.3 Conference Sidebar scenario An authorized user creates a side bar. The user selects whether the sidebar should include the media from the main conference or not and the audio gain level associated with the main conference audio. A user invites participants to the sidebar and upon acceptance they start receiving the sidebar media as specified by the sidebar creator. If the new participant is not a participant of the conference but rather just the sidebar the participant will only receive the sidebar media without the media of the main conference being mixed. A user with the right authorization can move another participant into the sidebar with no indication in which case the user will suddenly start receiving the sidebar media. Sidebar participants with the right authorization can select to hear or not hear the main conference audio mixed with the sidebar audio A participant can be a participant to more than one sidebar but can only actively participate in one. A participant can jump back and forth between the main conference and one or more sidebars to actively participate. 4.4 Coaching scenario This is a call center or a remote training session where there is a supervisor that can monitor. There are the supervised users that may be the call center operators or the teachers The supervisor will be a hidden participant and will not be part of the participant roster. The supervised users might get an announcement/tone indicating that the supervisor has joined. The other participants do not hear the announcement. Supervisor listens/sees to the session but can only be heard/seen by the supervised user. Supervisor can become a normal participant in which case the participants will see the supervisor as part of the roster and will start hearing and seeing him. 4.5 Presentation and QA session An example is a panel earning call scenario in which a group of presenters deliver material to a group of people. After the presentation is finished a QA session is opened. The conference is created as a panel and the panel participants are identified. Only their streams will be mixed. After the end of the presentation the session chair changes the conference type to normal and now streams from all users may be mixed. A floor control protocol can be used instead of changing the conference type. The chair can grant the right to speak by adding just the participant whose turn is to ask a question to the conference mix. 4.6 Presence enabled ad-hoc conference A presence enabled ad-hoc conference, sometimes described as "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, which results in the media being sent to the other participants in the conference. These types of conferences tend to be long lived, hence the need for presence to ensure that the other participants are still available. The ad-hoc nature of the conference means that the participant list can be changed at any time. 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. "Nick names" or aliases are often chosen by participants or assigned by the focus and used as handles within the room. 4.8 Interactive text Interactive text is using RTP to carry text one character at a time providing real-time interactivity, as described in RFC2793.  The interactive text session may be the main conference itself, or it may be used in conjunction with other media types. Interactive text may serve as text stream representing the audio in the conference using some translation services. There can be more then 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 transcoder have similar functionality to transcoders between different audio or video algorithms. The conference participants should be able to select to receive those text streams with the conference audio or without it. 4.9 Moderated group chat A moderated group chat scenario for text messaging is similar to group chat but with all text messages sent to the group being filtered/approved by a moderator. Note that the moderator can be a human or an application. The moderator also often has the ability to remove participants and provide feedback on their submissions (e.g. provide warnings before removal). 4.10 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 which is providing anonymity/ aliases to participants can also provide anonymous/alias sidebars. A text sidebar can also benefit from other security/logging/recording services provided by the focus. Another use of a text sidebar is a text only conversation/discussion between two or more conference participants while at the same time following the main conference without being distracted by additional audio. 4.11 Advanced media control features The following features can be used in all the conferencing scenarios. Announcement - The conference moderator may be able to play announcements to all the conference participants. The announcement may be pre-recorded or composed by the moderator before sending them. 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 in the time, the moderator wants to record an audio message like "in 5 minutes, everyone please come back to the main meeting" and then play that message to all of the breakout sessions. 5. Security Considerations 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, is used by the focus to admit or deny participation in a conference. For the conference policy to be implemented, the focus needs to be able to authenticate potential participants. The methods used will depend on the signaling protocols used by the focus. This can include a challenge/response mechanism, certificates, shared secret, asserted identity, etc. These conference specific security requirements are discussed further in the XCON requirements and framework documents. 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. 8 Informative References  Rosenberg, J., "A Framework for Conferencing with the Session Initiation Protocol", draft- ietf-sipping-conferencing-framework-01 (work in progress), October 2003.  Hellstrom, G., "RTP Payload for Text Conversation", RFC 2793, May 2000. Authors' Addresses Roni Even Polycom 94 Derech Em Hamoshavot Petach Tikva 49130 Israel EMail: email@example.com Nermeen Ismail Cisco Systems, Inc. 170 West Tasman Drive San Jose 95134 CA USA EMail: firstname.lastname@example.org Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in 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 made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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