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Ismail 5 Cisco Systems, Inc. 6 September 6, 2005 8 Conferencing Scenarios 9 draft-ietf-xcon-conference-scenarios-05.txt 11 Status of this Memo 13 By submitting this Internet-Draft, each author represents that any 14 applicable patent or other IPR claims of which he or she is aware 15 have been or will be disclosed, and any of which he or she becomes 16 aware will be disclosed, in accordance with Section 6 of BCP 79. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at 29 http://www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on March 10, 2006. 36 Copyright Notice 38 Copyright (C) The Internet Society (2005). 40 Abstract 42 This document describes multimedia conferencing scenarios. It 43 describes both basic and advanced conferencing scenarios involving 44 voice, video, text and interactive text sessions. These conferencing 45 scenarios will help with the definition and evaluation of the 46 protocols being developed in the centralized conferencing XCON 47 working group. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. Basic Conferencing scenarios . . . . . . . . . . . . . . . . . 3 53 2.1. Ad-hoc conference . . . . . . . . . . . . . . . . . . . . 4 54 2.2. Extension of a Point to point calls to a multipoint 55 call . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 56 2.3. Reserved conference . . . . . . . . . . . . . . . . . . . 4 57 3. Advanced Conferencing scenarios . . . . . . . . . . . . . . . 5 58 3.1. Extending a point-to-point call to a multipoint call . . . 5 59 3.2. Lecture mode conferences . . . . . . . . . . . . . . . . . 5 60 3.3. Conference with conference aware and unaware 61 participants . . . . . . . . . . . . . . . . . . . . . . . 6 62 3.4. A reserved or ad-hoc conference with conference-aware 63 participants. . . . . . . . . . . . . . . . . . . . . . . 6 64 3.5. Advanced conference features . . . . . . . . . . . . . . . 6 65 4. Scenarios for media policy control . . . . . . . . . . . . . . 9 66 4.1. Video mixing scenarios . . . . . . . . . . . . . . . . . . 9 67 4.2. Typical video conferencing scenario . . . . . . . . . . . 10 68 4.3. Conference Sidebar scenario . . . . . . . . . . . . . . . 11 69 4.4. Coaching scenario . . . . . . . . . . . . . . . . . . . . 11 70 4.5. Presentation and QA session . . . . . . . . . . . . . . . 12 71 4.6. Presence-enabled ad-hoc conference . . . . . . . . . . . . 12 72 4.7. Group chat text conferencing . . . . . . . . . . . . . . . 12 73 4.8. Interactive text . . . . . . . . . . . . . . . . . . . . . 13 74 4.9. Moderated group chat . . . . . . . . . . . . . . . . . . . 13 75 4.10. Text sidebars . . . . . . . . . . . . . . . . . . . . . . 13 76 4.11. Conference announcements . . . . . . . . . . . . . . . . . 13 77 5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 78 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 80 8. Informative References . . . . . . . . . . . . . . . . . . . . 14 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 82 Intellectual Property and Copyright Statements . . . . . . . . . . 16 84 1. Introduction 86 This document describes multimedia conferencing scenarios. The 87 development of these conferencing scenarios is intended to help with 88 definition and evaluation of the requirements for the centralized 89 conferencing (XCON) working group. Although this document uses some 90 definitions and conventions described in the SIP Conferencing 91 Framework document[1], these scenarios are not SIP-specific. The 92 document describes basic and advanced conferencing scenarios. The 93 advanced scenarios assume that the user agents support the set of 94 XCON protocols, identified in the Framework and Data Model for 95 Centralized Conferencing [3], in order to take advantage of the 96 conference functionality. However, note that many of these features 97 can be implemented today using an IVR or web interface to control the 98 conferencing application. 100 The entities comprising the Conferencing System are the conference 101 that is the center point for signaling and the participants. The 102 participant who initiated the conference is referenced as the 103 initiating participant. 105 The scenarios described demonstrate different conferencing services. 106 These conferencing services can be offered in a multimedia 107 environment that benefit from having some support in the user agents 108 that enable more robust and easier to use conferencing services. It 109 is up to the conferencing system manufacturers and the conferencing 110 service provider to decide what services can be built and which 111 services are offered to the end users. 113 The scenarios describe multimedia examples but they are applicable to 114 audio only as well as for audio and video conferences. 116 Multimedia conferences may include any combination of different media 117 types like audio, video, text, interactive text, or presentation 118 graphics. The conference scenarios are similar but the media 119 handling may be dependent on the media type. 121 2. Basic Conferencing scenarios 123 These scenarios enable a conference unaware participant to create, 124 join and participate in a conference. The participant may use out of 125 band signaling to participate in a conference but this is not a 126 mandatory requirement. The Conferencing System has all the 127 functionality it needs in order to supply the service offered to the 128 participants. A typical minimum requirement is that the participant 129 support DTMF tones/signal or provide voice responses to an IVR 130 system. 132 2.1. Ad-hoc conference 134 A participant has a service provisioned to him that enables him to 135 start an ad-hoc conference when he calls the Conferencing System. 136 When the participant wants to start a conference he calls the 137 conference service. The participant may be identified by different 138 means including request destination, authenticated identity, or an 139 IVR system using DTMF. The conference is created automatically with 140 the predefined functionality. The participant who has such a service 141 notifies the other participants how to call the conference via 142 external means such as instant message or email. The participant may 143 have the functionality of a Conferencing System and thus can create 144 ad-hoc conference using his own user agent functionality. An example 145 of such a conference is an audio conference initiated by one of the 146 participants who has a conference service that enables him to start a 147 conference when he calls a specific URI. The conference may be 148 created by the first person calling this URI or it may be created 149 only after the owner is authenticated using an IVR system. In the 150 latter case, the other participants may get an announcement and are 151 placed on hold if they call the conference before the owner. 153 2.2. Extension of a Point to point calls to a multipoint call 155 This is a basic case. The initiating participant (PA) is in a point 156 to point call with another participant (PB). PA wants to add a third 157 participant (PC) to the call. The initiating participant (PA) cannot 158 provide the Conferencing System functionality on his user agent nor 159 can the other participant (PB). PA and PB do not supports call 160 transfer. PA has a conferencing service using the methods described 161 in 2.1. PA conveys the conference information to PB in the point-to- 162 point call. Both participant disconnect and call the Conferencing 163 System. The Conferencing System may support dial out, for example 164 via DTMF, allowing the initiating participant to call the third party 165 through the Conferencing System. 167 2.3. Reserved conference 169 The reservation for this type of conference is typically done by an 170 out of band mechanism and in advance of the actual conference time. 171 The conference identification, which may be a URI or a phone number 172 with a pin number, is allocated by the reservation system. It is 173 sent to all participants using email, IM, etc. The participants join 174 using the conference identification. The conference identification 175 must be routable enabling the allocation of a conference with free 176 resources at the time when the conference actually run. The 177 Conferencing System can also dial out to the conference participants. 178 The participants may not be informed that they are in a conference 179 since their User Agent is not conference aware. The participants may 180 know, via announcement from the Conferencing System, that they are in 181 a conference and who the other participants are. 183 3. Advanced Conferencing scenarios 185 These scenarios assume user agents that support at least call 186 transfer service and a way to communicate information on events from 187 the Conferencing System to the user agent. The Conferencing System 188 may have the ability to discover the capabilities of the 189 participants, for example, to identify if they support call transfer. 190 This section specifies in each scenario the dependencies. An 191 advanced conference can be initiated only by an user agent that has 192 advanced features, but some user agents in the conference may have 193 less functionality. 195 3.1. Extending a point-to-point call to a multipoint call 197 The initiating participant is in a point-to-point call and wants to 198 add a third participant. The initiating participant can start a 199 multipoint call on a conferencing bridge known to him. The extension 200 can be without consultation, which means that he moves the point-to- 201 point call to the Conferencing System and then adds the third party 202 (this can be done in various ways). Alternatively the extension can 203 be done with consultation, which means that he puts his current party 204 on hold, calls the third party and asks him to join the conference, 205 and then transfers all the participants to the Conferencing System. 207 3.2. Lecture mode conferences 209 This conference scenario enables a conference with a lecturer who 210 presents a topic and can allow questions. The lecturer needs to know 211 who the participants are and to be able to give them the right to 212 speak. The right to speak can be based on floor control or an out of 213 band mechanism. 215 In general, the lecturer is seen/heard by the conference participants 216 and often shares a presentation or application with the other 217 participants. 219 A participant joining this type of conference can get the identity of 220 the lecturer and often the identities of the audience participants. 222 This type of conference may have multiple media streams. For 223 example, if simultaneous language translation is available, a 224 participant has the option of selecting the appropriate language 225 audio stream. Multiple video streams could include the speaker's 226 face and a whiteboard/demonstration stream. 228 3.3. Conference with conference aware and unaware participants 230 A conference can include participants that are a mix of conference 231 aware and unaware participants. Those participants may be conference 232 unaware participants using a proxy function that proxies the advanced 233 functionality between the different protocols and the Conferencing 234 System. For example, an IVR system or a web page interface can be 235 used to provide additional functionality. 237 3.4. A reserved or ad-hoc conference with conference-aware 238 participants. 240 The initiating participant calls the Conferencing System using, for 241 example, a unique identifier in order to start the conference. The 242 Conferencing System may use some authenticating method to qualify the 243 participant. The other participants may call the Conferencing System 244 and join the conference. The Conferencing System is able to find the 245 capabilities of the participants. In case of a reserved conference 246 the Conferencing System starts the conference at the scheduled time. 247 The participants may join by calling the conference URI or the 248 Conferencing System may call them. The conference may have privilege 249 levels associated with a specific conference or participant. The 250 privileges are for the initiating participant and for a regular 251 participant; the initiating participant may delegate privileges to 252 the other participants. The privileges allow functionality as 253 defined in the next section. 255 3.5. Advanced conference features 257 The following features can be used in all the advanced conferencing 258 scenarios. In the examples given in this section, when referring to 259 a participant that has a functionality it means a participant with 260 the right privileges. These scenarios may be available in the 261 advanced conferencing scenarios and are common in many conferencing 262 applications. This is not a requirement list, rather some examples 263 of how specific functions may be used in a conference. 265 o Add Participants - A participant may add a new participant to the 266 conference. This can be done, for example, by instructing the 267 Conferencing System to call the participant or by the first 268 participant calling the new participant and pointing him to the 269 conference. 270 o Delete Participant - A participant may delete participants from 271 the conference if he can identify them. 272 o Changing User Agent/Modes - During the course of a conference, a 273 participant may switch between user agents with different 274 capabilities while still remaining part of the conference. For 275 example, a participant may initially join using a mobile phone and 276 then switch to a desk top phone. Or a participant may join with a 277 phone, discover that the conference has video streams available, 278 and switch to a video phone. 279 o Changing Media - During the conference a participant may be able 280 to select different media streams than the one he had when he 281 joined the conference. An example is a participant that initially 282 joined the conference as an audio participant. The participant is 283 unable to understand the conversation properly and he learns that 284 there is also an interactive text available, he will ask to 285 receive also the text stream. 286 o Authenticate participants - A participant can authenticate other 287 participants who want to join the conference. This can be done, 288 for example, in a video conferencing session by creating a sidebar 289 between the two participants allowing the authenticating 290 participant to talk with the new participant and verify his 291 identity. 292 o Authorize participants - A participant can authorize other 293 participants in order to allow them to join the conference. This 294 can be done implicitly by assigning a password to the conference 295 or to each participant and letting the Conferencing System decide 296 if the new participant is allowed to join. the authorization can 297 be done explicitly by directing the entered password to the 298 initiating participant who will authorize each participant. The 299 conferencing system may use an authentication mechanism to 300 authenticate the participants. 301 o Controlling the presentation of media - During the conference the 302 participant may be able to manage whose media is being sent to 303 each participant. For example, the participant may be able to 304 decide that he wants to be the speaker and all the rest are 305 listeners; he may also specify whose media he wants to receive. 306 The participant may be able to mute a media stream during the 307 conference. 308 o Giving privileges - The participant may want, during the 309 conference, to give a privilege to another participant. The 310 assigning of privileges may be implicit when requested or explicit 311 by asking the participant to grant a privilege. 312 o Side conferences or sidebars - The participant may want to create 313 a side conference that include some of the main conference 314 participants. When the side conference is done the participants 315 return to the main conference. A sidebar may have the same 316 functionality as the main conference. There can be several 317 sidebars scenarios: 319 1. Basic sidebar is based on the capabilities of two participants 320 to have two calls at the same time, with a point to point call 321 in parallel to the main conference. It is user agent 322 implementation specific whether to automatically mix both 323 call's streams or allow the participant to manually switch 324 between them. 326 2. Conferencing System based sidebar uses the Conferencing System 327 to create the sidebar and compose the relevant sidebar stream 328 mixes. These mixes can include the main conference as an 329 incoming stream to the mix. Mechanisms to signal the creation 330 of the sidebar, invite participants and control the mixes 331 should be available. 333 For example, participants in an audio sidebar may not be heard 334 by the rest of the conference. However, the main conference 335 audio may be mixed in the sidebar, but at a lower volume, or in 336 a different channel. Another example, a sidebar can have a 337 different media type from the main conference; a video call can 338 have an audio sidebar where the other participants can see the 339 sidebar participants talking but can not hear them; or an audio 340 or video conference may have a text sidebar. 341 o Conference information - When a participant joins the conference 342 he is announced to the participants. An announcement may be 343 available when he leaves the conference. The participants may 344 query the conferencing system for the current participants of a 345 specific conference. This conference information may include 346 other information, for example, the media streams available in the 347 conference. 348 o Extending of a conference - Reserved conferences and ad-hoc 349 conferences may have a time limit. The Conferencing System 350 informs the participants when the limit is approaching and may 351 allow the extension of the conference. 352 o Adding and removing a media type to the conference - A participant 353 may want to start a data presentation during a conference. He may 354 want to distribute this new media to all the participants. The 355 participant asks the Conferencing System to start the new media 356 channel and to allow him to send data in the new channel. 357 o Audio-only participants - In a multimedia conference some of the 358 participants who want to join may have no way to send and receive 359 all the media types. Typically they can send and receive audio. 360 Such participants join the conference as audio-only participants. 361 The general case is that participants may send and receive only 362 part of the media streams available in the multi media conference. 363 o Passive participants - In a conference some participants may be 364 listeners to all or part of the media streams, but be invisible to 365 all the other participants. 366 o Recorders - A recorder can be added to the conference. A recorder 367 can record all streams or a subset of the streams. Recorders may 368 be turned on and off during the conference. Recorders may be used 369 for "role call" scenario in order to record a participant name. 370 This name can be announced at a later stage automatically or based 371 on a participant request. A recorder is a case of a passive 372 participant. 373 o Whisper/Private Message - A participant can send a one way message 374 (text, audio, or even some other media) to another participant 375 that is immediately rendered. This differs from a sidebar in that 376 it is immediate and creates no long-lived session. 377 o Human operator - A participant may ask for assistance from a human 378 operator during the conference. 380 4. Scenarios for media policy control 382 During a conference media streams may be controlled by authorized 383 participants using either a media control protocol or a third party 384 application. This section describes some typical media control 385 scenarios. The conference can be of any size. Some of the media 386 control scenarios are typical to specific conference sizes. As a 387 general rule larger conferences scenarios tend to be more centrally 388 managed or structured. 390 The mixing of media in a conference may start when the conference 391 starts or when the initiating participant joins. In the later case, 392 early participant may be put on hold and get "music on hold". 394 The scenarios apply to audio conferences as well as to multimedia 395 conferences. There are some specific information about the mixed 396 video layout and about interactive text discussed below. 398 4.1. Video mixing scenarios 400 For video the participant selects one of a set of pre-defined video 401 presentations offered by the server. Each video presentation is 402 identified by a textual description as well as an image specifying 403 how the presentation appears on the screen. In this scenario by 404 choosing a video presentation the participant chooses how many video 405 streams (participants) are viewed at once and the layout of these 406 video streams on the screen. 408 The contents of each sub-window can be defined by a conference policy 409 and/or controlled by authorized participants. It may also be 410 possible to have multiple mixes per conference, possibly as many as 411 there are participants. (Note that the same flexibility may be 412 afforded to audio mixes as well.). 414 The following are a list of typical video presentations; there are 415 other layouts available today in commercial products: 417 - Single view: This presentation typically shows the video of the 418 loudest speaker 419 - Dual View: This presentation shows two streams. If the streams are 420 to be multiplexed in one image (typical of centralized servers) the 421 multiplexing can be: 423 1. Side by side with no altered aspect ratio and hence blanking of 424 parts of the image might be necessary if the streams are to be 425 combined as one image. 427 2. Side by side windows with altered aspect ratios and hence 428 blanking parts of the image is not necessary. The mixer handles the 429 cropping of the images. 431 3. One above the other windows with no altered aspect ratio 433 4. One above the other windows with altered aspect ratio 435 - Quadrate view: This presentation shows 4 streams. If the streams 436 are multiplexed into one image (centralized server) they are arranged 437 in a 2x2 style. Note that in this style the aspect ratios are 438 maintained. 440 - 9 sub-picture view: This presentation shows 9 streams. If the 441 streams are to be multiplexed in one image they are arranged in a 3x3 442 style. In the multiplexing case cropping is performed under the 443 discretion of the mixer. 445 - 16 sub-picture view: This presentation shows 16 streams. If the 446 streams are to be multiplexed into one image they are arranged in a 447 4x4 style. In this style the aspect ratios are maintained and no 448 cropping or blanking is needed. 450 - 5+1 sub-picture view: This presentation shows 6 streams. If the 451 streams are to be multiplexed into one image then the pictures are 452 laid so that one sub-window occupies 4/9 of the screen while the 453 other five occupy 1/9 of the screen each. 455 4.2. Typical video conferencing scenario 457 This scenario is known as voice activated video switch. Every 458 participant hears the N loudest participants but he does not hear 459 himself. All the participants see the loudest speaker; the loudest 460 speaker may see the previous loudest speaker. This mode is typical 461 to small conference. 463 A participant with proper authorization can exclude one or more 464 participants from the audio or video mix. An indication might be 465 displayed to the affected participants indicating that they are not 466 being seen/heard. 468 A participant with proper authorization can manipulate the gain level 469 associated with one or more audio streams in the mix. 471 4.3. Conference Sidebar scenario 473 An authorized participant creates a side bar. The participant 474 selects whether the sidebar should include the media from the main 475 conference or not and the audio gain level associated with the main 476 conference audio. 478 A participant invites participants to the sidebar and upon acceptance 479 they start receiving the sidebar media as specified by the sidebar 480 creator. If the new participant is not a participant of the 481 conference, but just the sidebar, the participant only receives the 482 sidebar media without the media of the main conference. 484 A participant with the right authorization can move another 485 participant into the sidebar with no indication, in which case the 486 participant suddenly start receiving the sidebar media. 488 Sidebar participants with the right authorization can select to hear 489 or not hear the main conference audio mixed with the sidebar audio 491 A participant can be a participant to more than one sidebar but can 492 only actively participate in one. 494 A participant can jump back and forth between the main conference and 495 one or more sidebars. 497 4.4. Coaching scenario 499 This is a call center or a remote training session where there is a 500 supervisor who can monitor the conference. There are the supervised 501 participants that may be the call center operators or the teachers. 502 A participant in the conference may be a supervised participant or a 503 "customer". 505 The supervisor is a hidden participant and is not part of the 506 participant roster. 508 The supervised participants might get an announcement/tone indicating 509 that the supervisor has joined. The other participants do not hear 510 the announcement. 512 The supervisor listens to / sees the session but can only be heard / 513 seen by the supervised participant. 515 The supervisor can become a normal participant, in which case the 516 participants see the supervisor as part of the roster and start 517 hearing and seeing him. 519 4.5. Presentation and QA session 521 An example is an earning call scenario in which a group of presenters 522 deliver material to a group of people. After the presentation is 523 finished a QA session is opened. 525 The conference is created as a panel and the panel participants are 526 identified. Only their streams are mixed. 528 After the end of the presentation the session chair changes the 529 conference type to normal and now streams from all participants may 530 be mixed. Alternatively a floor control protocol can be used. The 531 chair can grant the right to speak by adding the participant, whose 532 turn it is to ask a question, to the conference mix. 534 4.6. Presence-enabled ad-hoc conference 536 A presence-enabled ad-hoc conference, sometimes described as "walkie 537 talkie" service, is a scenario in which a participant sends media to 538 the other participants of the conference after receiving a 539 confirmation of the other participants' availability. For example, a 540 participant presses a talk button, which checks the presence of the 541 participants to see if they are available for communication. If they 542 are, a confirmation tone is played and the participant can then talk, 543 which results in the media being sent to the other participants in 544 the conference. These types of conferences tend to be long lived, 545 hence the need for presence to ensure that the other participants are 546 still available. The ad-hoc nature of the conference means that the 547 participant list can be changed at any time. Floor control can be 548 used to allow other participants to speak, as the conference is 549 usually half-duplex in nature. 551 4.7. Group chat text conferencing 553 Group chat is a common scenario for text messaging in which a 554 participant joins (or enters) a chat room in which text messages from 555 participants are rendered in a single window and attributed to the 556 participant that sent the message. Changes in conference membership 557 are often announced in the text window itself (e.g. "Alice has just 558 entered the room. Bob has just departed."). Note that a real-time 559 transcription/closed captioning service can provide a similar window 560 in which audio media is converted into interactive text. "Nick 561 names" or aliases are often chosen by participants or assigned by the 562 Conferencing System and used as handles within the room. 564 4.8. Interactive text 566 Interactive text is using RTP to carry text one character at a time 567 providing real-time interactivity, as described in RFC2793[2]. The 568 interactive text session may be the main conference itself, or it may 569 be used in conjunction with other media types. Interactive text may 570 be used to represent the audio in the conference using some 571 translation services. There can be more than one such stream where 572 each text stream is in a different language. These text streams may 573 be used as subtitles to the audio stream. The translation from to 574 text to speech and back is done by transcoders. Those transcoder 575 have similar functionality to transcoders between different audio or 576 video algorithms. 578 The conference participants should be able to select to receive those 579 text streams with the conference audio or without it. 581 4.9. Moderated group chat 583 A moderated group chat scenario for text messaging is similar to 584 group chat but with all text messages sent to the group being 585 filtered/approved by a moderator. Note that the moderator can be a 586 human or an application. The moderator also often has the ability to 587 remove participants and provide feedback on their submissions (e.g. 588 provide warnings before removal). 590 4.10. Text sidebars 592 Interactive text or instant messaging sidebars are perhaps the most 593 common sidebars in conferences today. Often the text sessions are 594 separate from the conference. However, there are some advantages to 595 having text sessions be a sidebar and as a result a part of the main 596 conference. For example, a conference which is providing anonymity/ 597 aliases to participants can also provide anonymous/alias sidebars. A 598 text sidebar can also benefit from other security/logging/recording 599 services provided by the Conferencing System. 601 Another use of a text sidebar is a text-only conversation/discussion 602 between two or more conference participants who at the same time are 603 following the main conference. 605 4.11. Conference announcements 607 The conference moderator may be able to play announcements to all the 608 conference participants. The announcement may be pre-recorded or 609 composed by the moderator before sending them. The announcements may 610 be text, audio or audio visual. An example is a conference with 611 several audio break-out sessions going on. At some point in the 612 time, the moderator wants to record an audio message like "in 5 613 minutes, everyone please come back to the main meeting" and then play 614 that message to all of the breakout sessions. 616 5. Security Considerations 618 Conferences generally have authorization rules about who may or may 619 not join a conference, what type of media may or may not be used, 620 etc. This information, sometimes called the conference policy or 621 common conference information, is used by the Conferencing System to 622 admit or deny participation in a conference. For the conference 623 policy to be implemented, the Conferencing System needs to be able to 624 authenticate potential participants. The methods used depend on the 625 signaling protocols used by the conference. This can include a 626 challenge/response mechanism, certificates, shared secret, asserted 627 identity, etc. These conference-specific security requirements are 628 discussed further in the XCON requirements and framework documents. 630 6. IANA Considerations 632 There are no IANA considerations associated with this specification. 634 7. Acknowledgements 636 Thanks to Brian Rosen for contributing conferencing scenarios. 638 Thanks to Alan Johnston for going over the document and adding some 639 more scenarios; to Keith Lantz, Mary Barnes and Dave Morgan for 640 carefully reading the document. 642 8. Informative References 644 [1] Rosenberg, J., "A Framework for Conferencing with the Session 645 Initiation Protocol", 646 draft-ietf-sipping-conferencing-framework-04 (work in progress), 647 October 2003. 649 [2] Hellstrom, G., "RTP Payload for Text Conversation", RFC 2793, 650 May 2000. 652 [3] Barnes, M., Boulton, C., and O. Levin, "A Framework and Data 653 Model for Centralized Conferencing", 654 draft-barnes-xcon-framework-02 (work in progress), 655 February 2005. 657 Authors' Addresses 659 Roni Even 660 Polycom 661 94 Derech Em Hamoshavot 662 Petach Tikva 49130 663 Israel 665 Email: roni.even@polycom.co.il 667 Nermeen Ismail 668 Cisco Systems, Inc. 669 170 West Tasman Drive 670 San Jose 95134 671 CA USA 673 Email: nismail@cisco.com 675 Intellectual Property Statement 677 The IETF takes no position regarding the validity or scope of any 678 Intellectual Property Rights or other rights that might be claimed to 679 pertain to the implementation or use of the technology described in 680 this document or the extent to which any license under such rights 681 might or might not be available; nor does it represent that it has 682 made any independent effort to identify any such rights. Information 683 on the procedures with respect to rights in RFC documents can be 684 found in BCP 78 and BCP 79. 686 Copies of IPR disclosures made to the IETF Secretariat and any 687 assurances of licenses to be made available, or the result of an 688 attempt made to obtain a general license or permission for the use of 689 such proprietary rights by implementers or users of this 690 specification can be obtained from the IETF on-line IPR repository at 691 http://www.ietf.org/ipr. 693 The IETF invites any interested party to bring to its attention any 694 copyrights, patents or patent applications, or other proprietary 695 rights that may cover technology that may be required to implement 696 this standard. 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