idnits 2.17.1 draft-ietf-mediactrl-architecture-04.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** It looks like you're using RFC 3978 boilerplate. You should update this to the boilerplate described in the IETF Trust License Policy document (see https://trustee.ietf.org/license-info), which is required now. -- Found old boilerplate from RFC 3978, Section 5.1 on line 15. -- Found old boilerplate from RFC 3978, Section 5.5, updated by RFC 4748 on line 1128. -- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 1139. -- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 1146. -- Found old boilerplate from RFC 3979, Section 5, paragraph 3 on line 1152. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (November 27, 2008) is 5629 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'ACCEPTED' is mentioned on line 849, but not defined == Outdated reference: A later version (-12) exists of draft-ietf-mediactrl-sip-control-framework-07 == Outdated reference: A later version (-32) exists of draft-ietf-xcon-common-data-model-12 -- Obsolete informational reference (is this intentional?): RFC 793 (Obsoleted by RFC 9293) -- Obsolete informational reference (is this intentional?): RFC 2976 (Obsoleted by RFC 6086) -- Obsolete informational reference (is this intentional?): RFC 4346 (Obsoleted by RFC 5246) -- Obsolete informational reference (is this intentional?): RFC 4474 (Obsoleted by RFC 8224) -- Obsolete informational reference (is this intentional?): RFC 4566 (Obsoleted by RFC 8866) -- Obsolete informational reference (is this intentional?): RFC 4582 (Obsoleted by RFC 8855) -- Obsolete informational reference (is this intentional?): RFC 4583 (Obsoleted by RFC 8856) -- Obsolete informational reference (is this intentional?): RFC 4960 (Obsoleted by RFC 9260) Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 15 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MediaCtrl T. Melanchuk, Ed. 3 Internet-Draft Rain Willow Communications 4 Intended status: Informational November 27, 2008 5 Expires: May 31, 2009 7 An Architectural Framework for Media Server Control 8 draft-ietf-mediactrl-architecture-04 10 Status of this Memo 12 By submitting this Internet-Draft, each author represents that any 13 applicable patent or other IPR claims of which he or she is aware 14 have been or will be disclosed, and any of which he or she becomes 15 aware will be disclosed, in accordance with Section 6 of BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on May 31, 2009. 35 Abstract 37 This document describes an Architectural Framework for Media Server 38 Control. The primary focus will be to define logical entities that 39 exist within the context of Media Server control, and define the 40 appropriate naming conventions and interactions between them. 42 Table of Contents 44 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 45 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 46 3. Architecture Overview . . . . . . . . . . . . . . . . . . . . 6 47 4. SIP Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 10 48 5. Media Control for IVR Services . . . . . . . . . . . . . . . . 13 49 5.1. Basic IVR Services . . . . . . . . . . . . . . . . . . . . 14 50 5.2. IVR Services with Mid-call Controls . . . . . . . . . . . 14 51 5.3. Advanced IVR Services . . . . . . . . . . . . . . . . . . 14 52 6. Media Control for Conferencing Services . . . . . . . . . . . 15 53 6.1. Creating a New Conference . . . . . . . . . . . . . . . . 17 54 6.2. Adding a Participant To a Conference . . . . . . . . . . . 17 55 6.3. Media Controls . . . . . . . . . . . . . . . . . . . . . . 18 56 6.4. Floor Control . . . . . . . . . . . . . . . . . . . . . . 19 57 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 25 58 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 59 9. Security Considerations . . . . . . . . . . . . . . . . . . . 27 60 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 28 61 11. Informative References . . . . . . . . . . . . . . . . . . . . 29 62 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 32 63 Intellectual Property and Copyright Statements . . . . . . . . . . 33 65 1. Introduction 67 Application Servers host one or more instances of a communications 68 application. Media Servers provide real time media processing 69 functions. This documents presents the core architectural framework 70 to allow Application Servers to control Media Servers. An overview 71 of the architecture describing the core logical entities and their 72 interactions is presented in Section 3. The requirements for Media 73 Server control are defined in [RFC5167]. 75 The Session Initiation Protocol (SIP) [RFC3261] is used as the 76 session establishment protocol within this architecture. Application 77 Servers use it both to terminate media streams on Media Servers and 78 to create and manage control channels for Media Server control 79 between themselves and Media Servers. The detailed model for Media 80 Server control together with a description of SIP usage is presented 81 in Section 4. 83 Several services are described using the framework defined in this 84 document. Use cases for Inter-Active Voice Response (IVR) services 85 are described in Section 5 and conferencing use cases are described 86 in Section 6. 88 2. Terminology 90 The following terms are defined for use in this document in the 91 context of Media Server control: 93 Application Server (AS): A functional entity that hosts one or more 94 instances of a communication application. The application server 95 may include the conference policy server, the focus, and the 96 conference notification server, as defined in [RFC4353]. Also, it 97 may include communication applications that use IVR or 98 announcement services. 100 Media Functions: Functions available on a Media Server that are used 101 to supply media services to the AS. Some examples are Dual-Tone 102 Multi-Frequency (DTMF) detection, mixing, transcoding, playing 103 announcement, recording, etc. 105 Media Resource Broker (MRB): A logical entity that is responsible 106 for both the collection of appropriate published Media Server (MS) 107 information and supplying of appropriate MS information to 108 consuming entities. The MRB is an optional entity and will be 109 discussed in a separate document. 111 Media Server (MS): The media server includes the mixer as defined in 112 [RFC4353]. The media server plays announcements, it processes 113 media streams for functions like Dual Tone Multi-Frequency (DTMF) 114 detection and transcoding. The media server may also record media 115 streams for supporting IVR functions like announcing conference 116 participants. In the architecture for the 3GPP IP Multimedia 117 Subsystem (IMS) a Media Server is referred to as a Media Resource 118 Function (MRF). 120 Media Services: Application service requiring media functions such 121 as Interactive Voice Response (IVR) or Media conferencing. 123 Media Session: From the Session Description Protocol (SDP) 124 specification [RFC4566]: "A multimedia session is a set of 125 multimedia senders and receivers and the data streams flowing from 126 senders to receivers. A multimedia conference is an example of a 127 multimedia session." 129 MS Control Channel: A reliable transport connection between the AS 130 and MS used to exchange MS Control PDUs. Implementations must 131 support the Transport Control Protocol (TCP) [RFC0793] and may 132 support the Stream Control Transmission Protocol (SCTP) [RFC4960]. 133 Implementations must support TLS [RFC4346] as a transport-level 134 security mechanism although its use in deployments is optional. 136 MS Control Dialog: A SIP dialog that is used for establishing a 137 control channel between the UA and the MS. 139 MS Control Protocol: The protocol used for by an AS to control a MS. 140 The MS Control Protocol assumes a reliable underlying transport 141 protocol for the MS Control Channel. 143 MS Media Dialog: A SIP dialog between the AS and Media Server that 144 is used for establishing media sessions between a user device such 145 as a SIP phone and the Media Server. 147 The definitions for AS, MS, and MRB above are taken from [RFC5167]. 149 3. Architecture Overview 151 A Media Server (MS) is a network device that processes media streams. 152 Examples of media processing functionality may include: 154 o Control of the Real-Time Protocol (RTP) [RFC3550] streams such as 155 video fast update and flow control using Real-Time Control 156 Protocol (RTCP) feedback [RFC4585]. 158 o Mixing of incoming media streams. 160 o Media stream source (for multimedia announcements). 162 o Media stream processing (e.g. transcoding, DTMF detection). 164 o Media stream sink (for multimedia recordings) 166 A MS supplies one or more media processing functionalities, which may 167 include others than those illustrated above, to an Application Server 168 (AS). An AS is able to send a particular call to a suitable MS, 169 either through discovery of the capabilities that a specific MS 170 provides or through the use of a Media Resource Broker. 172 The type of processing that a Media Server performs on media streams 173 is specified and controlled by an Application Server. Application 174 Servers are logical entities that are capable of running one or more 175 instances of a communications application. Examples of Application 176 Servers that may interact with a Media Server are an AS acting as a 177 Conference 'Focus' as defined in [RFC4353] or an IVR application 178 using a Media Server to play announcements and detect DTMF key 179 presses. 181 Application servers use SIP to establish control channels between 182 themselves and MSs. A MS Control Channel implements a reliable 183 transport protocol that is is used to carry the MS Control Protocol. 184 A SIP dialog used to establish a control channel is referred to as a 185 MS Control Dialog. 187 Application Servers terminate SIP [RFC3261] signaling from SIP User 188 Agents and may terminate other signaling outside the scope of this 189 document. They use SIP Third Party Call Control [RFC3725] (3PCC) to 190 establish, maintain, and tear down media streams from those SIP UAs 191 to a Media Server. A SIP dialog used by an AS to establish a media 192 session on an MS is referred to as a MS Media Dialog. 194 Media streams go directly between SIP User Agents and Media Servers. 195 Media Servers support multiple types of media. Common supported RTP 196 media types include audio and video but others such as text and the 197 Binary Floor Control Protocol (BFCP) [RFC4583] are also possible. 198 This basic architecture, showing session establishment signaling 199 between a single AS and MS is shown in Figure 1 below. 201 +-------------+ +--------------+ 202 | | SIP (MS Control Dialog) | | 203 | Application |<----------------------->| Media | 204 | Server | | Server | 205 | |<----------------------->| | 206 +-------------+ SIP (MS Media Dialog) +--------------+ 207 ^ ^ 208 \ | RTP/SRTP 209 \ | audio/ 210 \ | video/etc) 211 \ | 212 \ v 213 \ +--------------+ 214 \ SIP | | 215 +-------------->| SIP | 216 | User Agent | 217 | | 218 +--------------+ 220 Figure 1: Basic Signalling Architecture 222 The architecture must support a many-to-many relationship between 223 Application Servers and Media Servers. In real world deployments, an 224 Application Server may interact with multiple Media Servers and/or a 225 Media Server may be controlled by more than one Application Server. 227 Application Servers can use the SIP URI as described in [RFC4240] to 228 request basic functions from Media Servers. Basic functions are 229 characterized as requiring no mid-call interactions between the AS 230 and MS. Examples of these functions are simple announcement playing 231 or basic conference mixing where the AS does not need to explicitly 232 control the mixing. 234 Most services however have interactions between the AS and MS during 235 a call or conference. The type of interactions can be generalized as 236 follows: 238 o commands from an AS to an MS to request the application or 239 configuration of a function. The request may apply to a single 240 media stream, multiple media streams associated with multiple SIP 241 dialogs, or to properties of a conference mix. 243 o responses from an MS to an AS reporting on the status of 244 particular command. 246 o notifications from an MS to an AS that report results from 247 commands or notify changes to subscribed status. 249 Commands, responses, and notifications are transported using one or 250 more dedicated control channels between the Application Server and 251 the Media Server. Dedicated control channels provide reliable, 252 sequenced, peer to peer transport for Media Server control 253 interactions. Implementations must support the Transport Control 254 Protocol (TCP) [RFC0793] and may support the Stream Control 255 Transmission Protocol (SCTP) [RFC4960]. Because MS control requires 256 sequenced reliable delivery of messages, unreliable protocols such as 257 the User Datagram Protocol (UDP) are not suitable. Implementations 258 must support TLS [RFC4346] as a transport-level security mechanism 259 although its use in deployments is optional. A dedicated control 260 channel is shown in Figure 2 below. 262 +-------------+ +--------------+ 263 | | | | 264 | Application | MS ctrl channel | Media | 265 | Server |<------------------->| Server | 266 | | | | 267 +-------------+ +--------------+ 268 ^ ^ ^ 269 RTP/SRTP | | | 270 (audio/ | | | 271 video/etc) | | | 272 | | v 273 +---|-v-------+ 274 +-|---v-------+ | 275 +-|-----------+ | | 276 | | | | 277 | SIP | | | 278 | User Agent | |-+ 279 | |-+ 280 +-------------+ 282 Figure 2: Media Server Control Architecture 284 Both Application Servers and Media Servers may interact with other 285 servers for specific purposes beyond the scope of this document. For 286 example Application Servers will often communicate with other 287 infrastructure components that are usually based on deployment 288 requirements with links to back-office data stores and applications. 289 Media Servers will often retrieve announcements from external file 290 servers. Also, many Media Servers support IVR dialog services using 291 VoiceXML [W3C.REC-voicexml20-20040316]. In this case the MS 292 interacts with other servers using HTTP during standard VoiceXML 293 processing. VoiceXML Media Servers may also interact with speech 294 engines, for example using MRCPv2, for speech recognition and 295 generation purposes. 297 Some specific types of interactions between Application and Media 298 servers are also out of scope this document. MS resource reservation 299 is one such interaction. Also, any interactions between Application 300 Servers, or between Media Servers, are also out of scope. 302 4. SIP Usage 304 The Session Initiation Protocol (SIP) [RFC3261] was developed by the 305 IETF for the purposes of initiating, managing and terminating 306 multimedia sessions. The popularity of SIP has grown dramatically 307 since its inception and is now the primary Voice over IP (VoIP) 308 protocol. This includes being selected as the basis for 309 architectures such as the IP Multimedia Subsystem (IMS) in 3GPP and 310 included in many of the early live deployments of VoIP related 311 systems. Media servers are not a new concept in IP telephony 312 networks and there have been numerous signaling protocols and 313 techniques proposed for their control. The most popular techniques 314 to date have used a combination of SIP and various markup languages 315 to convey media service requests and responses. 317 As discussed in Section 3 and illustrated in Figure 1, the logical 318 architecture described by this document involves interactions between 319 an Application Server (AS) and a Media Server (MS). The SIP 320 interactions can be broken into 'MS media dialogs' - used between an 321 AS and a MS to establish media sessions between an endpoint and a 322 Media Server, and 'MS control dialogs' - which are used to establish 323 and maintain MS control channels. 325 SIP is the primary signaling protocol for session signaling and is 326 used for all media sessions directed towards a Media Server as 327 described in this document. Media Servers may support other 328 signaling protocols but this type of interaction is not considered 329 here. Application Servers may terminate non-SIP signaling protocols 330 but must gateway those requests to SIP when interacting with a Media 331 Server. 333 SIP will also be used for the creation, management and termination of 334 the dedicated MS control channel(s). Control channel(s) provide 335 reliable sequenced delivery of MS Control Protocol messages. The 336 Application and Media Servers use the SDP attributes defined in 337 [RFC4145] to allow SIP negotiation of the control channel. A control 338 channel is closed when SIP terminates the corresponding MS control 339 dialog. Further details and example flows are provided in the SIP 340 Control Framework [I-D.ietf-mediactrl-sip-control-framework]. The 341 SIP Control Framework also includes basic control message semantics 342 corresponding to the types of interactions identified in Section 3. 343 It uses the concept of "packages" to allow domain specific protocols 344 to be defined using the Extensible Markup Language (XML) 345 [W3C.REC-xml-20060816] format. The MS Control Protocol is made up of 346 one or more packages for the SIP Control Framework. 348 Using SIP for both media and control dialogs provides a number of 349 inherent benefits over other potential techniques. These include: 351 1. The use of SIP location and rendezvous capabilities, as defined 352 in [RFC3263]. This provides core mechanisms for routing a SIP 353 request based on techniques such as DNS SRV and NAPTR records. 354 The SIP infrastructure makes heavy use of such techniques. 356 2. The security and identity properties of SIP. For example, using 357 TLS for reliably and securely connecting to another SIP based 358 entity. The SIP protocol has a number of Identity mechanisms 359 that can be used. [RFC3261] provides an intra-domain digest- 360 based mechanism and [RFC4474] defines a certificate based inter- 361 domain identity mechanism. SIP with S/MIME provides the ability 362 to secure payloads using encrypted and signed certificate 363 techniques. 365 3. SIP has extremely powerful and dynamic media negotiation 366 properties as defined in [RFC3261] and [RFC3264]. 368 4. The ability to select an appropriate SIP entity based on 369 capability sets as discussed in [RFC3840]. This provides a 370 powerful function that allows Media Servers to convey a specific 371 capability set. An AS is then free to select an appropriate MS 372 based on its requirements. 374 5. Using SIP also provides consistency with IETF protocols and 375 usages. SIP was intended to be used for the creation and 376 management of media sessions and this provides a correct usage of 377 the protocol. 379 As mentioned previously in this section, Media services using SIP are 380 fairly well understood. Some previous proposals suggested using the 381 SIP INFO [RFC2976] method as the transport vehicle between the AS and 382 MS. Using SIP INFO in this way is not advised for a number of 383 reasons which include: 385 o INFO is an opaque request with no specific semantics. A SIP 386 endpoint that receives an INFO request does not know what to do 387 with it based on SIP signaling. 389 o SIP INFO was not created to carry generic session control 390 information along the signaling path and it should only really be 391 used for optional application information e.g. carrying mid-call 392 PSTN signaling messages between PSTN gateways. 394 o SIP INFO traverses the signaling path which is an inefficient use 395 for control messages which can be routed directly between the AS 396 and MS. 398 o [RFC3261] contains rules when using an un-reliable protocol such 399 as UDP. When a packet reaches a size close to the Maximum 400 Transmission Unit (MTU) the protocol should be changed to TCP. 401 This type of operation is not ideal when constantly dealing with 402 large payloads such as XML formatted MS control messages. 404 5. Media Control for IVR Services 406 One of the functions of a Media Server is to assist an Application 407 Server implementing IVR services by performing media processing 408 functions on media streams. Although IVR is somewhat generic 409 terminology, the scope of media functions provided by a MS addresses 410 the needs for user interaction dialogs. These functions include 411 media transcoding, basic announcements, user input detection (via 412 DTMF or speech) and media recording. 414 A particular IVR or user dialog application typically requires the 415 use of several specific media functions, as described above. The 416 range and complexity of IVR dialogs can vary significantly, from a 417 simple single announcement play-back to complex voice mail 418 applications. 420 As previously discussed, an AS uses SIP [RFC3261] and SDP [RFC4566] 421 to establish and configure media sessions to a Media Server. An AS 422 uses the MS control channel, established using SIP, to invoke IVR 423 requests and to receive responses and notifications. This topology 424 is shown in Figure 3 below. 426 +-------------+ SIP +-------------+ 427 | Application |<---------------------------->| Media | 428 | Server | (media & MS Control dialogs) | Server | 429 | | | | 430 | | MS Control Protocol (IVR) | | 431 | |<---------------------------->| (IVR media | 432 | (App logic) | (CtrlChannel) | functions) | 433 +-------------+ +-------------+ 434 ^ ^^ 435 \ || R 436 \ || T 437 \ || P 438 \ || / 439 \ || S 440 \ || R 441 \ || T 442 \ || P 443 \ vv 444 \ call signaling +-----------+ 445 ---------------------------->| UE | 446 (e.g. SIP) +-----------+ 448 Figure 3: IVR Topology 450 The variety in complexity of Application Server IVR services requires 451 support for different levels of media functions from the Media Server 452 as described in the following sub-sections. 454 5.1. Basic IVR Services 456 For simple basic announcement requests the MS control channel, as 457 depicted in Figure 3 above, is not required. Simple announcement 458 requests may be invoked on the Media Server using the SIP URI 459 mechanism defined in [RFC4240]. This interface allows no user input 460 digit detection and collection and no mid-call dialog control. 461 However, many applications only require basic media services and the 462 processing burden on the Media Server to support more complex 463 interactions with the AS would not be needed in this case. 465 5.2. IVR Services with Mid-call Controls 467 For more complex IVR dialogs which require mid-call interaction and 468 control between the Application Server and the Media Server, the MS 469 control channel (as shown in Figure 3 above) is used to invoke 470 specific media functions on the Media Server. These functions 471 include, but are not limited to, complex announcements with barge-in 472 facility, user input detection and reporting (e.g. DTMF) to an 473 Application Server, DTMF and speech activity controlled recordings, 474 etc. Composite services, such as play-collect and play-record, are 475 also addressed by this model. 477 Mid-call control also allows Application Servers to subscribe to IVR 478 related events and for the Media Server to notify these events when 479 they occur. Examples of such events are announcement completion 480 events, record completion events, and reporting of collected DTMF 481 digits. 483 5.3. Advanced IVR Services 485 Although IVR Services with Mid-call Control, as described above, 486 provides a comprehensive set of media functions expected from a Media 487 Server, the Advanced IVR Services model allows a higher level of 488 abstraction describing application logic, as provided by VoiceXML, to 489 be executed on the Media Server. Invocation of VoiceXML IVR dialogs 490 may be via the 'Prompt and Collect' mechanism of [RFC4240]. 491 Additionally, the IVR control protocol can be extended to allow 492 VoiceXML requests to also be invoked over the MS control channel. 493 VoiceXML IVR services invoked on the Media Server may require an HTTP 494 interface (not shown in Figure 3) between the Media Server and one or 495 more back-end servers that host or generate VoiceXML documents. 496 These server(s) may or may not be physically separate from the 497 Application Sever. 499 6. Media Control for Conferencing Services 501 [RFC4353] describes the overall architecture and protocol components 502 needed for multipoint conferencing using SIP. The framework for 503 centralized conferencing [I-D.ietf-xcon-framework] 504 [draft-ietf-xcon-framework-08] extends the framework to include a 505 protocol between the user and the conferencing server. [RFC4353] 506 describes the conferencing server decomposition but leaves the 507 specifics open. 509 This section describes the decomposition and discusses the 510 functionality of the decomposed functional units. The conferencing 511 factory and the conference focus are part of the Application Server 512 described in this document. 514 An Application Server uses SIP Third Party Call Control [RFC3725] to 515 establish media sessions from SIP user agents to a Media Server. The 516 same mechanism is used by the Application Server as described in this 517 section to add/remove participants to/from a conference, as well as 518 to handle the involved media streams set up on a per-user basis. 519 Since the XCON framework has been conceived as protocol-agnostic when 520 talking about the Call Signaling Protocol used by users to join a 521 conference, an XCON-compliant Application Server will have to take 522 care of gatewaying non-SIP signaling negotiations, in order to set up 523 and make available valid SIP media sessions between itself and the 524 Media Server, while still keeping the non-SIP interaction with the 525 user in a transparent way. 527 +------------+ +------------+ 528 | | SIP (2m+1c) | | 529 | Application|-------------| Media | 530 | Server | | Server | 531 | (Focus) |-------------| (Mixer) | 532 | | CtrlChannel | | 533 +------------+ +------------+ 534 | \ .. . 535 | \\ RTP... . 536 | \\ .. . 537 | H.323 \\ ... . 538 SIP | \\ ... .RTP 539 | ..\ . 540 | ... \\ . 541 | ... \\ . 542 | .. \\ . 543 | ... \\ . 544 | .. \ . 545 +-----------+ +-----------+ 546 |Participant| |Participant| 547 +-----------+ +-----------+ 549 Figure 4: Conference Topology 551 To complement the functionality provided by 3PCC and by XCON control 552 protocol, the Application Server makes use of a dedicated Media 553 Server control channel in order to set up and manage media 554 conferences on the Media Server. Figure 4 shows the signaling and 555 media paths for a two participant conference. The three SIP dialogs 556 between the AS and MS establish two media sessions (2m) from 557 participants, one originally signaled using H.323 and then gatewayed 558 into SIP and one signaled directly in SIP, and one control session 559 (1c). 561 As a conference focus, the Application Server is responsible for 562 setting up and managing a media conference on the Media Servers, in 563 order to make sure that the all media streams provided in a 564 conference are available to its participants. This is achieved by 565 using the services of one or more mixer entities, as described in 566 RFC4353, whose role as part of the Media Server is described in this 567 section. Services required by the Application Server include, but 568 are not limited to, means to set up, handle and destroy a new media 569 conference, adding and removing participants from a conference, 570 managing media streams in a conference, controlling the layout and 571 the mixing configuration for each involved media, allowing per-user 572 custom media profiles and so on. 574 As a mixer entity, in such a multimedia conferencing scenario the 575 Media Server receives a set of media streams of the same type (after 576 transcoding if needed) and then takes care of combining the received 577 media in a type-specific manner, redistributing the result to each 578 authorized participant. The way each media stream is combined, as 579 well as the media-related policies, is properly configured and 580 handled by the Application Server by means of a dedicated MS control 581 channel. 583 To summarize the AS needs to be able to manage Media Servers at a 584 conference and participant level. 586 6.1. Creating a New Conference 588 When a new conference is created, as a result of a previous 589 conference scheduling or of first participant dialing in to a 590 specified URI, the Application Server must take care of appropriately 591 creating a media conference on the Media Server. It does so by 592 sending an explicit request to the Media Server. This can be by 593 means of a MS control channel message. This request may contain 594 detailed information upon the desired settings and policies for the 595 conference (e.g. the media to involve, the mixing configuration for 596 them, relevant identifiers, etc.). The Media Server validates such a 597 request and takes care of allocating the needed resources to set up 598 the media conference. 600 There is another way using SIP-based mechanisms such as [RFC4240] or 601 [RFC4579] using pre-defined conference profiles and then using the MS 602 control channel afterwards to control the conference if needed. 604 Once done, the MS informs the Application Server about the result of 605 the request. Each conference will be referred to by a specific 606 identifier, which both the Application Server and the Media Server 607 will include in subsequent transactions related to the same 608 conference (e.g. to modify the settings of an extant conference). 610 6.2. Adding a Participant To a Conference 612 As stated before, an Application Server uses SIP 3PCC to establish 613 media sessions from SIP user agents to a Media Server. The URI that 614 the AS uses in the INVITE to the MS may be one associated with the 615 conference on the MS. More likely however, the media sessions are 616 first established to the Media Server using a URI for the Media 617 Server and then subsequently joined to the conference using the MS 618 Control Protocol. This allows IVR dialogs to be performed prior to 619 joining the conference. 621 The AS as a 3PCC correlates the media session negotiation between the 622 UA and the MS, in order to appropriately establish all the needed 623 media streams based on the conference policies. 625 6.3. Media Controls 627 The XCON Common Data Model [I-D.ietf-xcon-common-data-model] 628 currently defines some basic media-related controls, which 629 conference-aware participants can take advantage of in several ways, 630 e.g. by means of a XCON conference control protocol or IVR dialogs. 631 These controls include the possibility to modify the participants' 632 own volume for audio in the conference, configure the desired layout 633 for incoming video streams, mute/unmute oneself and pause/unpause 634 one's own video stream. Such controls are exploited by conference- 635 aware participants through the use of dedicated conference control 636 protocol requests to the Application Server. The Application Server 637 takes care of validating such requests and translates them into the 638 Media Server Control Protocol, before forwarding them over the MS 639 Control Channel to the MS. According to the directives provided by 640 the Application Server, the Media Server manipulates the involved 641 media streams accordingly. 643 +------------+ +------------+ 644 | | 'Include audio | | 645 | Application| sent by user X | Media | 646 | Server | in conf Y mix' | Server | 647 | (Focus) |----------------->| (Mixer) | 648 | | (MS CtrlChn) | | 649 +------^-----+ +------------+ 650 | .. 651 | ... 652 | 'Unmute me' ... RTP 653 | (XCON) ... 654 | ... 655 | ... 656 +-----------+ ... 657 |Participant|... 658 +-----------+ 660 Figure 5: Conferencing Example: Unmuting A Participant 662 The Media Server may need to inform the AS of events like in-band 663 DTMF tones during the conference. 665 6.4. Floor Control 667 The XCON framework introduces "floor control" functionality as an 668 enhancement upon [RFC4575]. Floor control is a means to manage joint 669 or exclusive access to shared resources in a (multiparty) 670 conferencing environment. Floor control is not a mandatory mechanism 671 for a conferencing system implementation, but it provides advanced 672 media input control features for conference-aware users. Such 673 mechanism allows for a coordinated and moderated access to any set of 674 resources provided by the conferencing system. To do so, a so-called 675 floor is associated to a set of resources, thus representing for 676 users the right to access and manipulate the related resources 677 themselves. In order to take advantage of the floor control 678 functionality, a specific protocol, the Binary Floor Control 679 Protocol, has been specified [RFC4582]. [RFC4583] provides a way for 680 SIP UAs to set up a BFCP connection towards the Floor Control Server 681 and exploit floor control by means of a COMEDIA [RFC4145] 682 negotiation. 684 In the context of the AS-MS interaction, floor control constitutes a 685 further means to control users' media streams. A typical example is 686 a floor associated with the right to access the shared audio channel 687 in a conference. A user who is granted such a floor is granted by 688 the conferencing system the right to talk, which means that its audio 689 frames are included by the MS in the overall audio conference mix. 690 Similarly, when the floor is revoked the user is muted in the 691 conference, and its audio is excluded from the final mix. 693 The BFCP defines a Floor Control Server (FCS) and the Floor chair. 694 It is clear that the floor chair making decisions about floor 695 requests is part of the application logic. This implies that when 696 the floor chair role in a conference is automated, it will normally 697 be part of the AS. 699 The example makes it clear that there can be a direct or indirect 700 interaction between the Floor Control Server and the Media Server, in 701 order to correctly bind each floor to its related set of media 702 resources. Besides, a similar interaction is needed between the 703 Floor Control Server and the Application Server as well, since the 704 latter must be aware of all the associations between floors and 705 resources, in order to opportunely orchestrate the related bindings 706 with the element responsible for such resources (e.g. the Media 707 Server when talking about audio and/or video streams) and the 708 operations upon them (e.g. mute/unmute a user in a conference). For 709 this reason, the Floor Control Server can be co-located with either 710 the Media Server or the Application Server, as long as both elements 711 are allowed to interact with the Floor Control Server by means of 712 some kind of protocol. 714 In the following lines, both the approaches will be described, in 715 order to better explain the interactions between the involved 716 components in both the topologies. 718 When the AS and the FCS are co-located, the scenario is quite 719 straightforward. In fact it can be considered as a variation of the 720 case depicted in Figure 5. The only relevant difference is that in 721 this case the action the AS commands on the control channel is 722 triggered by a change in the floor control status instead of a 723 specific control requested by a participant himself. The sequence 724 diagram in Figure 6 describes the interaction between the involved 725 parties in a typical scenario. It assumes that a BFCP connection 726 between the UA and the FCS (which as we assume is co-located with the 727 AS) has already been negotiated and established, and that the UA has 728 been made aware of all the relevant identifiers and floors-resources- 729 associations (e.g. by means of [RFC4583]). It also assumes that the 730 AS has previously configured the media mixing on the MS using the MS 731 control channel. Every frame the UA might be sending on the related 732 media stream is currently being dropped by the MS, since the UA still 733 isn't authorized to use the resource. For a SIP UA, this state could 734 be consequent to a 'sendonly' field associated to the media stream in 735 a re-INVITE originated by the MS. It is worth pointing out that the 736 AS has to make sure that no user-provided control mechanism, e.g. the 737 CCP mixing controls, can override the floor control, when it is 738 exploited. 740 UA AS MS 741 (Floor Participant) (FCS) 742 | | | 743 |<===================== One-way RTP stream ======================| 744 | | | 745 | FloorRequest(BFCP) | | 746 |------------------------------------>| | 747 | | | 748 | FloorRequestStatus[PENDING](BFCP) | | 749 |<------------------------------------| | 750 | |--+ apply | 751 | | | policies | 752 | |<-+ to request | 753 | | | 754 | FloorRequestStatus[ACCEPTED](BFCP) | | 755 |<------------------------------------| | 756 | | | 757 . . . 758 . . . 759 | | | 760 | FloorRequestStatus[GRANTED](BFCP) | | 761 |<------------------------------------| | 762 | | 'Unmute UA' (CtrlChn) | 763 | |------------------------->| 764 | | | 765 |<==================== Bidirectional RTP stream ================>| 766 | | | 767 . . . 768 . . . 770 Figure 6: Conferencing Example: Floor Control Call Flow 772 A UA, which also acts as a floor participant, sends a 'FloorRequest' 773 to the floor control server (FCS, which is co-located with the AS), 774 stating his will to be granted the floor associated with the audio 775 stream in the conference. The AS answers the UA with a 776 'FloorRequestStatus' message with a PENDING status, meaning that a 777 decision upon the request has not been taken yet. The AS, according 778 to the BFCP policies for this conference, takes a decision upon the 779 request, i.e. accepting it. Note that this decision might be relayed 780 to another participant in case he has previously been assigned as 781 chair of the floor. Assuming the request has been accepted, the AS 782 notifies the UA about the decision with a new 'FloorRequestStatus', 783 this time with an ACCEPTED status in it. The ACCEPTED status of 784 course only means that the request has been accepted, which doesn't 785 mean the floor has been granted yet. Once the queue management in 786 the FCS, according to the specified algorithms for scheduling, states 787 that the floor request previously made by the UA can be granted, the 788 AS sends a new 'FloorRequestStatus' to the UA with a GRANTED status, 789 and takes care of unmuting the user in the conference by sending a 790 directive to the MS through the control channel. Once the UA 791 receives the notification stating his request has been granted, he 792 can start sending its media, aware of the fact that now his media 793 stream won't be dropped by the MS. In case the session has been 794 previously updated with a 'sendonly' associated to the media stream, 795 the MS must originate a further re-INVITE stating that the media 796 stream flow is now bidirectional ('sendrecv'). 798 As mentioned before, this scenario envisages an automated floor chair 799 role, where it's the AS, according to some policies, which takes 800 decisions upon floor requests. The case of a chair role impersonated 801 by a real person is exactly the same, with the difference that the 802 incoming request is not directly handled by the AS according to its 803 policies, but it is instead forwarded to the floor control 804 participant the chair UA is exploiting. The decision upon the 805 request is then communicated by the chair UA to the AS-FCS by means 806 of a ChairAction message. 808 The rest of this section will instead explore the other scenario, 809 which assumes the interaction between AS-FCS to happen through the MS 810 control channel. This scenario is compliant with the H.248.19 811 document related to conferencing in 3GPP. The following sequence 812 diagram describes the interaction between the involved parties in the 813 same use-case scenario that has been explored for the previous 814 topology: consequently, the diagram makes exactly the same 815 assumptions that have been made for the previously described 816 scenario. This means that it again assumes that a BFCP connection 817 between the UA and the FCS has already been negotiated and 818 established, and that the UA has been made aware of all the relevant 819 identifiers and floors-resources-associations. It also assumes that 820 the AS has previously configured the media mixing on the MS using the 821 MS control channel. This time it includes identifying the BFCP 822 moderated resources, establishing basic policies and instructions 823 about chair identifiers for each resource, and subscribing to events 824 of interest, considering the FCS is not co-located with the AS 825 anymore. Additionally, a BFCP session has been established between 826 the AS (which in this scenario acts as a floor chair), and the FCS 827 (MS). Every frame the UA might be sending on the related media 828 stream is currently being dropped by the MS, since the UA still isn't 829 authorized to use the resource. For a SIP UA, this state could be 830 consequent to a 'sendonly' field associated to the media stream in a 831 re-INVITE originated by the MS. It is again worth pointing out that 832 the AS has to make sure that no user-provided control mechanism, e.g. 833 the CCP mixing controls, can override the floor control, when it is 834 exploited. 836 UA AS MS 837 (Floor Participant) (Floor Chair) (FCS) 838 | | | 839 |<===================== One-way RTP stream ======================| 840 | | | 841 | FloorRequest(BFCP) | | 842 |--------------------------------------------------------------->| 843 | | | 844 | | FloorRequestStatus[PENDING](BFCP) | 845 |<---------------------------------------------------------------| 846 | | FloorRequestStatus[PENDING](BFCP) | 847 | |<-----------------------------------| 848 | | | 849 | | ChairAction[ACCEPTED] (BFCP) | 850 | |----------------------------------->| 851 | | ChairActionAck (BFCP) | 852 | |<-----------------------------------| 853 | | | 854 | | FloorRequestStatus[ACCEPTED](BFCP) | 855 |<---------------------------------------------------------------| 856 | | | 857 . . . 858 . . . 859 | | | 860 | | FloorRequestStatus[GRANTED](BFCP) | 861 |<---------------------------------------------------------------| 862 | | 'Floor has been granted' (CtrlChn) | 863 | |<-----------------------------------| 864 | | | 865 |<==================== Bidirectional RTP stream ================>| 866 | | | 867 . . . 868 . . . 870 Figure 7: Conferencing Example: Floor Control Call Flow 872 A UA, which also acts as a floor participant, sends a 'FloorRequest' 873 to the floor control server (FCS, which is collocated with the MS), 874 stating his will to be granted the floor associated with the audio 875 stream in the conference. The MS answers the UA with a 876 'FloorRequestStatus' message with a PENDING status, meaning that a 877 decision upon the request has not been taken yet. It then notifies 878 the AS, which in this example handles the floor chair role, about the 879 new request by forwarding there the received request. The AS, 880 according to the BFCP policies for this conference, takes a decision 881 upon the request, i.e. accepting it. It informs the MS about its 882 decision through a BFCP 'ChairAction' message. The MS then 883 acknowledges the 'ChairAction' message and then notifies the UA about 884 the decision with a new 'FloorRequestStatus', this time with an 885 ACCEPTED status in it. The ACCEPTED status of course only means that 886 the request has been accepted, which doesn't mean the floor has been 887 granted yet. Once the queue management in the MS, according to the 888 specified algorithms for scheduling, states that the floor request 889 previously made by the UA can be granted, the MS sends a new 890 'FloorRequestStatus' to the UA with a GRANTED status, and takes care 891 of unmuting the user in the conference. Once the UA receives the 892 notification stating his request has been granted, he can start 893 sending its media, aware of the fact that now his media stream won't 894 be dropped by the MS. In case the session has been previously 895 updated with a 'sendonly' associated to the media stream, the MS must 896 originate a further re-INVITE stating that the media stream flow is 897 now bidirectional ('sendrecv'). 899 This scenario envisages an automated floor chair role, where it's the 900 AS, according to some policies, which takes decisions upon floor 901 requests. Again, the case of a chair role impersonated by a real 902 person is exactly the same, with the difference that the incoming 903 request is not forwarded to the AS but to the floor control 904 participant the chair UA is exploiting. The decision upon the 905 request is communicated by means of a ChairAction message in the same 906 way. 908 Another typical scenario is a BFCP-moderated conference with no chair 909 managing floor requests. In such a scenario, the MS has to take care 910 of incoming requests according to some predefined policies, e.g. 911 always accepting new requests. In this case, no decisions are 912 required by external entities, since all is instantly decided by 913 means of policies in the MS. 915 As stated before, the case of the FCS co-located with the AS is much 916 simpler to understand and exploit. When the AS has full control upon 917 the FCS, including its queues management, the AS directly instructs 918 the MS according to the floor status changes, e.g. by instructing the 919 MS through the control channel to unmute a user who has been granted 920 the floor associated to the audio media stream. 922 7. Acknowledgments 924 The authors would like to thank Spencer Dawkins for detailed reviews 925 and comments, Gary Munson for suggestions, and Xiao Wang for review 926 and feedback. 928 8. IANA Considerations 930 This document has no actions for IANA. 932 9. Security Considerations 934 This document describes the architectural framework to be used for 935 Media Server control. Its focus is the interactions between 936 Application Servers and Media Servers. User Agents interact with 937 Application Servers by means of signaling protocols such as SIP. 938 These interactions are beyond the scope of this document. 939 Applications Servers are responsible for utilizing the security 940 mechanisms of their signaling protocols, combined with application 941 specific policy, to insure they grant service only to authorized 942 users. Media interactions between User Agents and Media Servers are 943 also outside the scope of this document. Those interactions are at 944 the behest of Application Servers which must ensure that appropriate 945 security mechanisms are used. For example, if the MS is acting as 946 the FCS, then the BFCP connection between the User Agent and the MS, 947 is established to the MS by the AS using SIP and the SDP mechanisms 948 described in [RFC4583]. BFCP [RFC4582] strongly imposes the use of 949 TLS for BFCP. 951 Media Servers are valuable network resources and need to be protected 952 against unauthorized access. Application Servers use SIP and related 953 standards to establish both control channels to Media Servers, and to 954 establish media sessions, including BFCP sessions, between a MS and 955 end users. Media servers use the security mechanisms of SIP to 956 authenticate requests from Application servers and to insure the 957 integrity of those requests. Leveraging the security mechanisms of 958 SIP insures that only authorized Application Servers are allowed to 959 establish sessions to a MS, and to access MS resources through those 960 sessions. 962 Control channels between an AS and MS carry the MS control protocol 963 which affects both the service seen by end users and the resources 964 used on a Media Server. TLS [RFC4346] must be implemented as the 965 transport-level security mechanism for control channels to guarantee 966 the integrity of MS control interactions. 968 The resources of a MS can be shared by more than one AS. Media 969 Servers must prevent one AS from accessing and manipulating the 970 resources that have been assigned to another AS. This may be 971 achieved by an MS associating ownership of a resource to the AS that 972 originally allocates it, and then insuring that future requests 973 involving that resource correlate to the AS that owns and is 974 responsible for it. 976 10. Contributors 978 This document is a product of the Media Control Architecture Design 979 Team. In addition to the editor, the following individuals comprised 980 the design team and made substantial textual contributions to this 981 document: 983 Chris Boulton: cboulton@ubiquity.net 985 Martin Dolly: mdolly@att.com 987 Roni Even: roni.even@polycom.co.il 989 Lorenzo Miniero: lorenzo.miniero@unina.it 991 Adnan Saleem: Adnan.Saleem@radisys.com 993 11. Informative References 995 [I-D.ietf-mediactrl-sip-control-framework] 996 Boulton, C., Melanchuk, T., and S. McGlashan, "Media 997 Control Channel Framework", 998 draft-ietf-mediactrl-sip-control-framework-07 (work in 999 progress), November 2008. 1001 [I-D.ietf-xcon-common-data-model] 1002 Novo, O., Camarillo, G., Morgan, D., Even, R., and J. 1003 Urpalainen, "Conference Information Data Model for 1004 Centralized Conferencing (XCON)", 1005 draft-ietf-xcon-common-data-model-12 (work in progress), 1006 October 2008. 1008 [I-D.ietf-xcon-framework] 1009 Barnes, M., Boulton, C., and O. Levin, "A Framework for 1010 Centralized Conferencing", draft-ietf-xcon-framework-11 1011 (work in progress), April 2008. 1013 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, 1014 RFC 793, September 1981. 1016 [RFC2976] Donovan, S., "The SIP INFO Method", RFC 2976, 1017 October 2000. 1019 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1020 A., Peterson, J., Sparks, R., Handley, M., and E. 1021 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1022 June 2002. 1024 [RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation 1025 Protocol (SIP): Locating SIP Servers", RFC 3263, 1026 June 2002. 1028 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 1029 with Session Description Protocol (SDP)", RFC 3264, 1030 June 2002. 1032 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 1033 Jacobson, "RTP: A Transport Protocol for Real-Time 1034 Applications", STD 64, RFC 3550, July 2003. 1036 [RFC3725] Rosenberg, J., Peterson, J., Schulzrinne, H., and G. 1037 Camarillo, "Best Current Practices for Third Party Call 1038 Control (3pcc) in the Session Initiation Protocol (SIP)", 1039 BCP 85, RFC 3725, April 2004. 1041 [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, 1042 "Indicating User Agent Capabilities in the Session 1043 Initiation Protocol (SIP)", RFC 3840, August 2004. 1045 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 1046 the Session Description Protocol (SDP)", RFC 4145, 1047 September 2005. 1049 [RFC4240] Burger, E., Van Dyke, J., and A. Spitzer, "Basic Network 1050 Media Services with SIP", RFC 4240, December 2005. 1052 [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security 1053 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 1055 [RFC4353] Rosenberg, J., "A Framework for Conferencing with the 1056 Session Initiation Protocol (SIP)", RFC 4353, 1057 February 2006. 1059 [RFC4474] Peterson, J. and C. Jennings, "Enhancements for 1060 Authenticated Identity Management in the Session 1061 Initiation Protocol (SIP)", RFC 4474, August 2006. 1063 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 1064 Description Protocol", RFC 4566, July 2006. 1066 [RFC4575] Rosenberg, J., Schulzrinne, H., and O. Levin, "A Session 1067 Initiation Protocol (SIP) Event Package for Conference 1068 State", RFC 4575, August 2006. 1070 [RFC4579] Johnston, A. and O. Levin, "Session Initiation Protocol 1071 (SIP) Call Control - Conferencing for User Agents", 1072 BCP 119, RFC 4579, August 2006. 1074 [RFC4582] Camarillo, G., Ott, J., and K. Drage, "The Binary Floor 1075 Control Protocol (BFCP)", RFC 4582, November 2006. 1077 [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format 1078 for Binary Floor Control Protocol (BFCP) Streams", 1079 RFC 4583, November 2006. 1081 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 1082 "Extended RTP Profile for Real-time Transport Control 1083 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, 1084 July 2006. 1086 [RFC4960] Stewart, R., "Stream Control Transmission Protocol", 1087 RFC 4960, September 2007. 1089 [RFC5167] Dolly, M. and R. Even, "Media Server Control Protocol 1090 Requirements", RFC 5167, March 2008. 1092 [W3C.REC-voicexml20-20040316] 1093 Rehor, K., Danielsen, P., Burnett, D., McGlashan, S., 1094 Ferrans, J., Porter, B., Lucas, B., Hunt, A., Carter, J., 1095 and S. Tryphonas, "Voice Extensible Markup Language 1096 (VoiceXML) Version 2.0", World Wide Web Consortium 1097 Recommendation REC-voicexml20-20040316, March 2004, 1098 . 1100 [W3C.REC-xml-20060816] 1101 Yergeau, F., Paoli, J., Bray, T., Sperberg-McQueen, C., 1102 and E. Maler, "Extensible Markup Language (XML) 1.0 1103 (Fourth Edition)", World Wide Web Consortium 1104 Recommendation REC-xml-20060816, August 2006, 1105 . 1107 Author's Address 1109 Tim Melanchuk (editor) 1110 Rain Willow Communications 1112 Email: tim.melanchuk@gmail.com 1114 Full Copyright Statement 1116 Copyright (C) The IETF Trust (2008). 1118 This document is subject to the rights, licenses and restrictions 1119 contained in BCP 78, and except as set forth therein, the authors 1120 retain all their rights. 1122 This document and the information contained herein are provided on an 1123 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1124 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 1125 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 1126 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 1127 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1128 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1130 Intellectual Property 1132 The IETF takes no position regarding the validity or scope of any 1133 Intellectual Property Rights or other rights that might be claimed to 1134 pertain to the implementation or use of the technology described in 1135 this document or the extent to which any license under such rights 1136 might or might not be available; nor does it represent that it has 1137 made any independent effort to identify any such rights. Information 1138 on the procedures with respect to rights in RFC documents can be 1139 found in BCP 78 and BCP 79. 1141 Copies of IPR disclosures made to the IETF Secretariat and any 1142 assurances of licenses to be made available, or the result of an 1143 attempt made to obtain a general license or permission for the use of 1144 such proprietary rights by implementers or users of this 1145 specification can be obtained from the IETF on-line IPR repository at 1146 http://www.ietf.org/ipr. 1148 The IETF invites any interested party to bring to its attention any 1149 copyrights, patents or patent applications, or other proprietary 1150 rights that may cover technology that may be required to implement 1151 this standard. Please address the information to the IETF at 1152 ietf-ipr@ietf.org.