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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force SIPPING WG 3 Internet Draft J. Rosenberg 4 dynamicsoft 5 H. Schulzrinne 6 Columbia U. 7 draft-ietf-sipping-conference-package-00.txt 8 June 24, 2002 9 Expires: December 2002 11 A Session Initiation Protocol (SIP) Event Package for Conference State 13 STATUS OF THIS MEMO 15 This document is an Internet-Draft and is in full conformance with 16 all provisions of Section 10 of RFC2026. 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 To view the list Internet-Draft Shadow Directories, see 32 http://www.ietf.org/shadow.html. 34 Abstract 36 This document defines a conference event package for the SIP Events 37 architecture, along with a data format used in notifications for this 38 package. The conference package allows users to subscribe to a SIP 39 URI that is associated with a conference. Notifications are sent 40 about changes in the membership of this conference, changes in active 41 speaker, and media mixing information. 43 Table of Contents 45 1 Introduction ........................................ 4 46 2 Terminology ......................................... 4 47 3 Conference Event Package ............................ 4 48 3.1 Event Package Name .................................. 5 49 3.2 Event Package Parameters ............................ 5 50 3.3 SUBSCRIBE Bodies .................................... 5 51 3.4 Subscription Duration ............................... 6 52 3.5 NOTIFY Bodies ....................................... 6 53 3.6 Notifier Processing of SUBSCRIBE Requests ........... 6 54 3.7 Notifier Generation of NOTIFY Requests .............. 6 55 3.8 Subscriber Processing of NOTIFY Requests ............ 6 56 3.9 Handling of Forked Requests ......................... 7 57 3.10 Rate of Notifications ............................... 7 58 3.11 State Agents ........................................ 7 59 4 Conference Data Format .............................. 7 60 4.1 Structute of the Format ............................. 8 61 4.1.1 User Element ........................................ 8 62 4.1.2 Status .............................................. 9 63 4.1.3 Dialog .............................................. 9 64 4.1.4 Media Status ........................................ 9 65 4.2 Constructing Coherent State ......................... 9 66 4.3 Schema .............................................. 10 67 4.4 Example ............................................. 13 68 5 Security Considerations ............................. 13 69 6 IANA Considerations ................................. 13 70 6.1 application/conference-info+xml MIME Registration 71 ................................................................ 13 72 6.2 URN Sub-Namespace Registration for 73 urn:ietf:params:xml:ns:conference-info ......................... 14 74 7 Acknowledgements .................................... 15 75 8 Authors Addresses ................................... 15 76 9 Normative References ................................ 15 77 10 Informative References .............................. 16 79 1 Introduction 81 The SIP Events framework [1] defines general mechanisms for 82 subscription to, and notification of, events within SIP networks. It 83 introduces the notion of a package, which is a specific 84 "instantiation" of the events mechanism for a well-defined set of 85 events. Packages have been defined for user presence [9], watcher 86 information [10], and message waiting indicators [11], amongst 87 others. Here, we define an event package for SIP conferences. This 88 package will work for any conference in which there is a central 89 signaling element [12]. 91 The conferencing package allows a subscriber to learn about the 92 identities of participants and their status in the conference, the 93 dialogs that are used by each user, the media makeup of the 94 conference, and the mixing matrix (i.e., who is receiving whose 95 audio). This information is vital to building conferencing 96 applications using SIP. 98 2 Terminology 100 In this document, the key words "MUST", "MUST NOT", "REQUIRED", 101 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", 102 and "OPTIONAL" are to be interpreted as described in RFC 2119 [2] and 103 indicate requirement levels for compliant implementations. 105 3 Conference Event Package 107 The conference event package allows a user to subscribe to a 108 conference. In SIP, conferences are represented by URIs. These URIs 109 route to a SIP user agent that is responsible for ensuring that all 110 users in the conference can communicate with each other. Detailed 111 information on conferencing models can be found in [12]. This package 112 can work with any of the tightly-coupled models described in that 113 specification. However, the conference server may not have complete 114 information on the media makeup of the conference. This is the case 115 for multicast-based conferences, where the server cannot know the 116 mixing matrix for the conference. In this case, that information 117 would simply not be reported through this package. 119 The specific information conveyed in notifications in this package 120 is: 122 o The SIP URI identifying the user. 124 o The dialog state associated with that users attachment to the 125 conference. 127 o Their status in the conference (active, declined, departed). 129 o Their status in terms of receiving media in the conference. 131 This section provides the details for defining a SIP Events package, 132 as specified by [1]. 134 3.1 Event Package Name 136 The name of this event package is "conference". This package name is 137 carried in the Event and Allow-Events header, as defined in [1]. 139 3.2 Event Package Parameters 141 A single parameter, "recurse" is defined for this package. When 142 present, it informs the server that it should check whether any 143 participants in the conference are themselves conferences, and if so, 144 generate a subscription to their conference state with the "recurse" 145 attribute. The users reported in notifications from this recursed 146 subscription are reported to the original subscriber. The result is 147 that the list of users reported to the subscriber represents the 148 complete user list even when cascaded conferences are used. 150 Example: 152 Event: conference;recurse 154 3.3 SUBSCRIBE Bodies 156 A SUBSCRIBE for a dialog package MAY contain a body. This body 157 defines a filter to apply to the subscription. 159 A SUBSCRIBE for a conference package MAY be sent without a body. This 160 implies the default subscription filtering policy. The default policy 161 is: 163 o Notifications are generated every time there is any change in 164 the set of users participating in the conference, or a change 165 their state (dialog state, media mixing state, etc.) 167 o Notifications do not normally contain full state; rather, they 168 only indicate the state of the participant whose state has 169 changed. The exception is a NOTIFY sent in response to a 170 SUBSCRIBE. These NOTIFYs contain the complete view of 171 conference state. 173 o For a given user, the notifications contain the identity 174 information and status. 176 3.4 Subscription Duration 178 The default expiration time for a subscription to a conference is one 179 hour. Of course, once the conference ends, all subscriptions to that 180 particular conference are terminated, with a reason of "noresource" 181 [1]. 183 3.5 NOTIFY Bodies 185 The body of the notification contains a conference information 186 document. All implementations MUST support the type 187 "application/conference-info+xml", defined in Section 4. Other 188 formats MAY be supported. 190 When a client generates a SUBSCRIBE request, and that request 191 contains an Accept header, the "application/conference-info+xml" 192 format MUST be included in the header. Other formats MAY be listed. 193 The default value for the Accept header when it is not present in a 194 request is "application/conference-info+xml". 196 Of course, the notifications generated by the server MUST be in one 197 of the formats specified in the Accept header in the SUBSCRIBE 198 request. 200 3.6 Notifier Processing of SUBSCRIBE Requests 202 The conference information contains very sensitive information. 203 Therefore, all subscriptions SHOULD be authenticated and then 204 authorized before approval. Authorization policy is at the discretion 205 of the administrator, as always. However, a few recommendations can 206 be made. 208 It is RECOMMENDED that all users in the conference be allowed to 209 subscribe to the conference. 211 3.7 Notifier Generation of NOTIFY Requests 213 Notifications SHOULD be generated for the conference whenever a new 214 participant joins, a participant leaves, and a dial-out attempt 215 succeeds or fails. Notifications MAY be generated for the conference 216 whenever the media mixing status of a user changes. 218 3.8 Subscriber Processing of NOTIFY Requests 220 The SIP Events framework expects packages to specify how a subscriber 221 processes NOTIFY requests in any package specific ways, and in 222 particular, how it uses the NOTIFY requests to contruct a coherent 223 view of the state of the subscribed resource. 225 Typically, the NOTIFY for the conference package will only contain 226 information about those users whose state in the conference has 227 changed. To construct a coherent view of the total state of all 228 users, a subscriber to the dialog package will need to combine 229 NOTIFYs received over time. 231 Notifications within this package can convey partial information; 232 that is, they can indicate information about a subset of the state 233 associated with the subscription. This means that an explicit 234 algorithm needs to be defined in order to construct coherent and 235 consistent state. The details of this mechanism are specific to the 236 particular document type. See Section 4.2 for information on 237 constructing coherent information from an application/conference- 238 info+xml document. 240 3.9 Handling of Forked Requests 242 By their nature, the conferences supported by this package are 243 centralized. Therefore, SUBSCRIBE requests for a conference should 244 not generally fork. Users of this package MUST NOT install more than 245 a single subscription as a result of a single SUBSCRIBE request. 247 3.10 Rate of Notifications 249 For reasons of congestion control, it is important that the rate of 250 notifications not become excessive. As a result, it is RECOMMENDED 251 that the server not generate notifications for a single subscriber at 252 a rate faster than once every 5 seconds. 254 3.11 State Agents 256 Conference state is ideally maintained in the element in which the 257 conference resides. Therefore, the elements that maintain the 258 conference are the ones best suited to handle subscriptions to it. 259 Therefore, the usage of state agents is NOT RECOMMENDED for this 260 package. 262 4 Conference Data Format 264 Conference information is an XML document [3] that MUST be well- 265 formed and SHOULD be valid. Dialog information documents MUST be 266 based on XML 1.0 and MUST be encoded using UTF-8. This specification 267 makes use of XML namespaces for identifying dialog information 268 documents and document fragments. The namespace URI for elements 269 defined by this specification is a URN [4], using the namespace 270 identifier 'ietf' defined by [5] and extended by [6]. This URN is: 272 urn:ietf:params:xml:ns:conference-info 274 A conference information document begins with the root element tag 275 "conference-info". 277 4.1 Structute of the Format 279 Conference information begins with the top level element 280 "conference-info". This element has three mandatory attributes: 282 version: This attribute allows the recipient of conference 283 information documents to properly order them. Versions 284 start at 0, and increment by one for each new document sent 285 to a subscriber. Versions are scoped within a subscription. 286 Versions MUST be representable using a 32 bit integer. 288 state: This attribute indicates whether the document contains 289 the full conference information, or whether it contains 290 only information on those users whose state have changed 291 since the previous document (partial). 293 entity: This attribute contains a URI that identifies the 294 conference whose information is reported in the remainder 295 of the document. 297 The "conference-info" element has zero or more "user" sub-elements 298 which contain information on the users in the conference. 300 4.1.1 User Element 302 Each user element has zero or one "status" elements, indicating their 303 status in the conference, zero or one "dialog" elements, indicating 304 their dialog information, and zero or one "media-state" elements, 305 indicating their media reception information. 307 The user element has one mandatory attribute, "uri" that indicates 308 the URI for the user in the conference. This is a logical identifier, 309 not a machine specific one (i.e., its taken from the To/From, not the 310 Contact). The optional attribute "display-name" contains a display 311 name for the user. The standard "xml:lang" language attribute can 312 also be present to indicate the language of the display name. 314 4.1.2 Status 316 The status element contains the status of the user in the conference. 317 The following statuses are defined: 319 active: The user is in an active dialog with the conference 320 host. 322 departed: The user sent a BYE, thus leaving the conference. 324 booted: The user was sent a BYE by the conference host, booting 325 them out of the conference. 327 failed: The server tried to bring the user into the conference, 328 but its attempt to contact the specific user resulted in a 329 non-200 class final response. 331 4.1.3 Dialog 333 The dialog element is defined in [7]. 335 4.1.4 Media Status 337 The "media-status" element indicates the types of media that the user 338 is currently receiving in the conference. It consists of a series of 339 "media-stream" sub-elements, each of one describes a particular media 340 stream. Each "media-stream" element has a mandatory "media-type" 341 attribute that indicates the MIME media type for the stream. There is 342 also an optional "send-status" and "recv-status" attribute which 343 attribute which indicates the status of the media to/from that user. 345 If the "send-status" is "received-by-all", it means that the media 346 for that stream that is being generated by the user is being mixed by 347 the server and sent to all recipients. "muted" means that no one is 348 receiving their media. If it is "unknown", the server does not know 349 the status, perhaps because the media is being distributed via 350 multicast or multi-unicast. 352 If the "recv-status" is "receiving-all" it means that the user is 353 hearing all other participants. If it is "anchor-only", the user is 354 hearing media from just a single participant. If it is "unknown", the 355 server does not know the status, perhaps because the media is being 356 distributed via multicast or multi-unicast. 358 4.2 Constructing Coherent State 360 The conference information subscriber maintains a table for the list 361 of users in the conference. The table contains a row for each user. 363 Each row is indexed by a URI, present in the "uri" attribute of the 364 "user" element. The contents of each row contain the state of that 365 user as conveyed in the document. The table is also associated with a 366 version number. The version number MUST be initialized with the value 367 of the "version" attribute from the "conference-info" element in the 368 first document received. Each time a new document is received, the 369 value of the local version number, and the "version" attribute in the 370 new document, are compared. If the value in the new document is one 371 higher than the local version number, the local version number is 372 increased by one, and the document is processed. If the value in the 373 document is more than one higher than the local version number, the 374 local version number is set to the value in the new document, the 375 document is processed, and the subscriber SHOULD generate a refresh 376 request to trigger a full state notification. If the value in the 377 document is less than the local version, the document is discarded 378 without processing. 380 The processing of the conference information document depends on 381 whether it contains full or partial state. If it contains full state, 382 indicated by the value of the "state" attribute in the "conference- 383 info" element, the contents of the table are flushed. They are 384 repopulated from the document. A new row in the table is created for 385 each "user" element. If the document contains partial state, as 386 indicated by the value of the "state" attribute in the "conference- 387 info" element, the document is used to update the table. For each 388 "user" element in the document, the subscriber checks to see whether 389 a row exists for that user. This check is done by comparing the URI 390 in the "uri" attribute of the "user" element with the URI associated 391 with the row. If the user doesn't exist in the table, a row is added, 392 and its state is set to the information from that "user" element. If 393 the user does exist, its state is updated to be the information from 394 that "user" element. If a row is updated or created, such that its 395 state is now booted, failed or departed, that entry MAY be removed 396 from the table at any time. 398 4.3 Schema 400 The following is the schema for the application/conference-info+xml 401 type: 403 404 411 412 415 416 419 420 421 422 424 426 427 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 449 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 473 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 500 OPEN ISSUE: We need to register the schema for the dialog 501 info package in order to have a stable reference for it in 502 the conference info schema above. 504 4.4 Example 506 The following is an example conference information document: 508 509 510 active 511 512 513 514 515 516 active 517 518 520 This document describes a conference with two users, both of which 521 are active. 523 5 Security Considerations 525 Subscriptions to conference state can reveal very sensitive 526 information. For this reason, the document recommends authentication 527 and authorization, and provides guidelines on sensible authorization 528 policies. 530 Since the data in notifications is sensitive as well, end-to-end SIP 531 encryption mechanisms using S/MIME SHOULD be used to protect it. 533 6 IANA Considerations 535 This document registers a new MIME type, application/conference- 536 info+xml and registers a new XML namespace. 538 6.1 application/conference-info+xml MIME Registration 540 MIME media type name: application 542 MIME subtype name: conference-info+xml 544 Mandatory parameters: none 546 Optional parameters: Same as charset parameter application/xml 547 as specified in RFC 3023 [8]. 549 Encoding considerations: Same as encoding considerations of 550 application/xml as specified in RFC 3023 [8]. 552 Security considerations: See Section 10 of RFC 3023 [8] and 553 Section 5 of this specification. 555 Interoperability considerations: none. 557 Published specification: This document. 559 Applications which use this media type: This document type has 560 been used to support SIP conferencing applications. 562 Additional Information: 564 Magic Number: None 566 File Extension: .cif or .xml 568 Macintosh file type code: "TEXT" 570 Personal and email address for further information: Jonathan 571 Rosenberg, 573 Intended usage: COMMON 575 Author/Change controller: The IETF. 577 6.2 URN Sub-Namespace Registration for 578 urn:ietf:params:xml:ns:conference-info 580 This section registers a new XML namespace, as per the guidelines in 581 [6]. 583 URI: The URI for this namespace is 584 urn:ietf:params:xml:ns:conference-info. 586 Registrant Contact: IETF, SIMPLE working group, 587 , Jonathan Rosenberg 588 . 590 XML: 592 BEGIN 593 594 596 597 598 600 Dialog Information Namespace 601 603

Namespace for Dialog Information

604

application/conference-info+xml

605

See RFCXXXX.

606 607 608 END 610 7 Acknowledgements 612 The authors would like to thank Dan Petrie ans Sean Olson for their 613 comments. 615 8 Authors Addresses 617 Jonathan Rosenberg 618 dynamicsoft 619 72 Eagle Rock Avenue 620 First Floor 621 East Hanover, NJ 07936 622 email: jdrosen@dynamicsoft.com 624 Henning Schulzrinne 625 Columbia University 626 M/S 0401 627 1214 Amsterdam Ave. 628 New York, NY 10027-7003 629 email: schulzrinne@cs.columbia.edu 631 9 Normative References 633 [1] A. Roach, "SIP-specific event notification," Internet Draft, 634 Internet Engineering Task Force, Mar. 2002. Work in progress. 636 [2] S. Bradner, "Key words for use in RFCs to indicate requirement 637 levels," RFC 2119, Internet Engineering Task Force, Mar. 1997. 639 [3] W. W. W. C. (W3C), "Extensible markup language (xml) 1.0." The 640 XML 1.0 spec can be found at http://www.w3.org/TR/1998/REC-xml- 641 19980210. 643 [4] R. Moats, "URN syntax," RFC 2141, Internet Engineering Task 644 Force, May 1997. 646 [5] R. Moats, "A URN namespace for IETF documents," RFC 2648, 647 Internet Engineering Task Force, Aug. 1999. 649 [6] M. Mealling, "The IANA XML registry," Internet Draft, Internet 650 Engineering Task Force, Nov. 2001. Work in progress. 652 [7] J. Rosenberg and H. Schulzrinne, "A session initiation protocol 653 (SIP) event package for dialog state," Internet Draft, Internet 654 Engineering Task Force, June 2002. Work in progress. 656 [8] M. Murata, S. S. Laurent, and D. Kohn, "XML media types," RFC 657 3023, Internet Engineering Task Force, Jan. 2001. 659 10 Informative References 661 [9] J. Rosenberg, "Session initiation protocol (SIP) extensions for 662 presence," Internet Draft, Internet Engineering Task Force, May 2002. 663 Work in progress. 665 [10] J. Rosenberg, "A session initiation protocol (SIP)event 666 template-package for watcher information," Internet Draft, Internet 667 Engineering Task Force, May 2002. Work in progress. 669 [11] R. Mahy, "A message summary and message waiting indication event 670 package for the session initiation protocol (SIP)," Internet Draft, 671 Internet Engineering Task Force, June 2002. Work in progress. 673 [12] J. Rosenberg and H. Schulzrinne, "Models for multi party 674 conferencing in SIP," Internet Draft, Internet Engineering Task 675 Force, Nov. 2001. Work in progress. 677 Full Copyright Statement 679 Copyright (c) The Internet Society (2002). All Rights Reserved. 681 This document and translations of it may be copied and furnished to 682 others, and derivative works that comment on or otherwise explain it 683 or assist in its implementation may be prepared, copied, published 684 and distributed, in whole or in part, without restriction of any 685 kind, provided that the above copyright notice and this paragraph are 686 included on all such copies and derivative works. However, this 687 document itself may not be modified in any way, such as by removing 688 the copyright notice or references to the Internet Society or other 689 Internet organizations, except as needed for the purpose of 690 developing Internet standards in which case the procedures for 691 copyrights defined in the Internet Standards process must be 692 followed, or as required to translate it into languages other than 693 English. 695 The limited permissions granted above are perpetual and will not be 696 revoked by the Internet Society or its successors or assigns. 698 This document and the information contained herein is provided on an 699 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 700 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 701 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 702 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 703 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.