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If these are generic example addresses, they should be changed to use any of the ranges defined in RFC 6890 (or successor): 192.0.2.x, 198.51.100.x or 203.0.113.x. -- The document has examples using IPv4 documentation addresses according to RFC6890, but does not use any IPv6 documentation addresses. Maybe there should be IPv6 examples, too? Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 6, 2015) is 3215 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFCXXXX' is mentioned on line 1208, but not defined == Outdated reference: A later version (-37) exists of draft-ietf-mmusic-rfc4566bis-15 ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) ** Obsolete normative reference: RFC 5245 (Obsoleted by RFC 8445, RFC 8839) == Outdated reference: A later version (-54) exists of draft-ietf-mmusic-sdp-bundle-negotiation-22 Summary: 3 errors (**), 0 flaws (~~), 6 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group E. Ivov 3 Internet-Draft Jitsi 4 Intended status: Standards Track T. Stach 5 Expires: January 7, 2016 Unaffiliated 6 E. Marocco 7 Telecom Italia 8 C. Holmberg 9 Ericsson 10 July 6, 2015 12 A Session Initiation Protocol (SIP) usage for Trickle ICE 13 draft-ietf-mmusic-trickle-ice-sip-02 15 Abstract 17 The Interactive Connectivity Establishment (ICE) protocol describes a 18 Network Address Translator (NAT) traversal mechanism for UDP-based 19 multimedia sessions established with the Offer/Answer model. The ICE 20 extension for Incremental Provisioning of Candidates (Trickle ICE) 21 defines a mechanism that allows ICE agents to shorten session 22 establishment delays by making the candidate gathering and 23 connectivity checking phases of ICE non-blocking and by executing 24 them in parallel. 26 This document defines usage semantics for Trickle ICE with the 27 Session Initiation Protocol (SIP). 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on January 7, 2016. 46 Copyright Notice 48 Copyright (c) 2015 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4 66 3.1. Rationale. Why INFO . . . . . . . . . . . . . . . . . . . 5 67 3.2. Discovery issues . . . . . . . . . . . . . . . . . . . . 6 68 3.3. Relationship with the Offer/Answer Model . . . . . . . . 7 69 4. Incremental Signalling of ICE candidates . . . . . . . . . . 9 70 4.1. Establishing the dialog . . . . . . . . . . . . . . . . . 9 71 4.1.1. Asserting dialog state through reliable Offer/Answer 72 delivery . . . . . . . . . . . . . . . . . . . . . . 9 73 4.1.2. Asserting dialog state through unreliable 74 Offer/Answer delivery . . . . . . . . . . . . . . . . 10 75 4.1.3. Initiating Trickle ICE without an SDP Answer . . . . 12 76 4.1.4. Considerations for 3PCC . . . . . . . . . . . . . . . 13 77 4.2. Delivering candidates in INFO messages . . . . . . . . . 15 78 5. Initial discovery of Trickle ICE support . . . . . . . . . . 18 79 5.1. Provisioning support for Trickle ICE . . . . . . . . . . 18 80 5.2. Trickle ICE discovery with GRUU . . . . . . . . . . . . . 19 81 5.3. Trickle ICE discovery through other protocols . . . . . . 20 82 5.4. Fallback to Half Trickle . . . . . . . . . . . . . . . . 20 83 6. Considerations for RTP and RTCP multiplexing . . . . . . . . 22 84 7. Considerations for Media Multiplexing . . . . . . . . . . . . 22 85 8. Content Type 'application/sdpfrag' . . . . . . . . . . . . . 23 86 8.1. Overall Description . . . . . . . . . . . . . . . . . . . 23 87 8.2. Grammar . . . . . . . . . . . . . . . . . . . . . . . . . 24 88 9. Info Package . . . . . . . . . . . . . . . . . . . . . . . . 24 89 9.1. Overall Description . . . . . . . . . . . . . . . . . . . 24 90 9.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 24 91 9.3. Info Package Name . . . . . . . . . . . . . . . . . . . . 25 92 9.4. Info Package Parameters . . . . . . . . . . . . . . . . . 25 93 9.5. SIP Option Tags . . . . . . . . . . . . . . . . . . . . . 25 94 9.6. Info Message Body Parts . . . . . . . . . . . . . . . . . 25 95 9.7. Info Package Usage Restrictions . . . . . . . . . . . . . 26 96 9.8. Rate of INFO Requests . . . . . . . . . . . . . . . . . . 27 97 9.9. Info Package Security Considerations . . . . . . . . . . 27 98 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 99 10.1. application/sdpfrag MIME Type . . . . . . . . . . . . . 27 100 10.2. SIP Info Package 'trickle-ice' . . . . . . . . . . . . . 28 101 10.3. SIP Option Tag 'trickle-ice' . . . . . . . . . . . . . . 29 102 11. Security Considerations . . . . . . . . . . . . . . . . . . . 29 103 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 29 104 13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 29 105 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 106 14.1. Normative References . . . . . . . . . . . . . . . . . . 30 107 14.2. Informative References . . . . . . . . . . . . . . . . . 31 108 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 110 1. Introduction 112 The Interactive Connectivity Establishment protocol [RFC5245] (a.k.a. 113 Vanilla ICE) describes a mechanism for NAT traversal that consists of 114 three main phases: a phase where an agent gathers a set of candidate 115 transport addresses (source IP address, port and transport protocol), 116 a second phase where these candidates are sent to a remote agent and 117 this gathering procedure is repeated and, finally, a third phase 118 where connectivity between all candidates in both sets is checked 119 (connectivity checks). Once these phases have been completed, and 120 only then, can both agents begin communication. According to the 121 Vanilla ICE specification the three phases above happen 122 consecutively, in a blocking way, which can introduce undesirable 123 latency during session establishment. 125 The Trickle ICE extension defined in [I-D.ietf-mmusic-trickle-ice] 126 defines generic semantics required for these ICE phases to happen 127 simultaneously, in a non-blocking way and hence speed up session 128 establishment. 130 This specification defines a usage of Trickle ICE with the Session 131 Initiation Protocol (SIP)[RFC3261]. It describes how ICE candidates 132 are to be incrementally exchanged with SIP INFO requests and how the 133 Half Trickle and Full Trickle modes defined in 134 [I-D.ietf-mmusic-trickle-ice] are to be used by SIP User Agents (UAs) 135 depending on their expectations for support of Trickle ICE by a 136 remote agent. 138 This document defines a new Info Package as specified in [RFC6086] 139 for use with Trickle ICE. 141 2. Terminology 143 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 144 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 145 document are to be interpreted as described in [RFC2119]. 147 This specification makes use of all terminology defined by the 148 protocol for Interactive Connectivity Establishment in [RFC5245] and 149 its Trickle ICE extension [I-D.ietf-mmusic-trickle-ice]. It is 150 assumed that the reader will be familiar with the terminology from 151 both of them. 153 3. Protocol Overview 155 The semantics that Vanilla ICE [RFC5245] defines for exchanging ICE 156 candidates are exclusively based on use of Offers and Answers as per 157 [RFC3264] over the Session Description Protocol (SDP) [RFC4566]. 158 This specification extends these mechanism by allowing ICE candidates 159 to also be sent in parallel to the Offer/Answer negotiation or after 160 the completion of Offer/Answer negotiation. This extension is done 161 through the use of SIP INFO messages and a newly defined Info Package 162 [RFC6086]. 164 Typically, in cases where Trickle ICE is fully supported, a candidate 165 exchange would happen along the following lines: The Offerer would 166 send an INVITE containing a subset of candidates and then wait for an 167 early dialog to be established. Once that happens, it will be able 168 to continue sending candidates through in INFO requests and within 169 the same dialog. 171 Similarly, an Answerer can start or continue "trickling" ICE 172 candidates using INFO messages within the dialog established by its 173 18x provisional response. Figure 1 shows such a sample exchange: 175 STUN/Turn STUN/TURN 176 Servers Alice Bob Servers 177 | | | | 178 | STUN Bi.Req. | INVITE (Offer) | | 179 |<--------------|------------------------>| | 180 | | 183 (Answer) | TURN Alloc Req | 181 | STUN Bi.Resp. |<------------------------|--------------->| 182 |-------------->| INFO/OK (SRFLX Cand.) | | 183 | |------------------------>| TURN Alloc Resp| 184 | | INFO/OK (Relay Cand.) |<---------------| 185 | |<------------------------| | 186 | | | | 187 | | More Cands & ConnChecks| | 188 | |<=======================>| | 189 | | | | 190 | | 200 OK | | 191 | |<------------------------| | 192 | | ACK | | 193 | |------------------------>| | 194 | | | | 195 | | 5245 SIP re-INVITE | | 196 | |------------------------>| | 197 | | 200 OK | | 198 | |<------------------------| | 199 | | ACK | | 200 | |------------------------>| | 201 | | | | 202 | |<===== MEDIA FLOWS =====>| | 203 | | | | 205 Figure 1: Sample Trickle ICE scenario with SIP 207 3.1. Rationale. Why INFO 209 The decision to use SIP INFO requests as a candidate transport method 210 is based primarily on their lightweight nature. Once a dialog has 211 been established, INFO messages can be exchanged both ways with no 212 restrictions on timing and frequency and no risk of collision. 214 On the other hand, using Offer/Answer and UPDATE requests, which from 215 an [RFC5245] perspective is the traditional way of transporting ICE 216 candidates, introduces the following complications: 218 Need for a non-blocking mechanism: [RFC3264] defines Offer/Answer 219 as a strictly sequential mechanism. There can only be a maximum 220 of one exchange at any point of time. Both sides cannot 221 simultaneously send Offers nor can they generate multiple Offers 222 prior to receiving an Answer. Using UPDATEs for candidate 223 transport would therefore imply the implementation of a candidate 224 pool at every agent where candidates can be stored until it is 225 once again that agent's "turn" to emit an Answer or a new Offer. 226 Such an approach would introduce non-negligible complexity for no 227 additional value. 229 Elevated risk of glare: The sequential nature of Offer/Answer also 230 makes it impossible for both sides to send Offers simultaneously. 231 What's worse is that there are no mechanisms in SIP to actually 232 prevent that. [RFC3261], where the situation of Offers crossing 233 on the wire is described as "glare", only defines a procedure for 234 addressing the issue after it has occurred. According to that 235 procedure both Offers are invalidated and both sides need to retry 236 the negotiation after a period between 0 and 4 seconds. The high 237 likelihood for glare to occur and the average two second backoff 238 intervals would imply Trickle ICE processing duration would not 239 only fail to improve but actually exceed those of Vanilla ICE. 241 INFO messages decouple the exchange of candidates from the Offer/ 242 Answer negotiation and are subject to none of the glare issues 243 described above, which makes them a very convenient and lightweight 244 mechanism for asynchronous delivery of candidates. 246 Using in-dialog INFO messages also provides a way of guaranteeing 247 that candidates are delivered end-to-end, between the same entities 248 that are actually in the process of initiating a session. The 249 alternative would have implied requiring support for Globally 250 Routable UA URI (GRUU) [RFC5627] which, given GRUUs relatively low 251 adoption levels, would have constituted too strong of constraint to 252 the adoption of Trickle ICE. 254 3.2. Discovery issues 256 In order for to benefit from Trickle ICE's full potential and reduce 257 session establishment latency to a minimum, Trickle ICE agents need 258 to generate SDP Offers and Answers that contain incomplete, 259 potentially empty sets of candidates. Such Offers and Answers can 260 only be handled meaningfully by agents that actually support 261 incremental candidate provisioning, which implies the need to confirm 262 such support before actually using it. 264 Contrary to other protocols, like XMPP [RFC6120], where "in advance" 265 capability discovery is widely implemented, the mechanisms that allow 266 this for SIP (i.e., a combination of UA Capabilities [RFC3840] and 267 GRUU [RFC5627]) have only seen low levels of adoption. This presents 268 an issue for Trickle ICE implementations as SIP UAs do not have an 269 obvious means of verifying that their peer will support incremental 270 candidate provisioning. 272 The Half Trickle mode of operation defined in the Trickle ICE 273 specification [I-D.ietf-mmusic-trickle-ice] provides one way around 274 this, by requiring first Offers to contain a complete set of ICE 275 candidates and only using incremental provisioning for the rest of 276 the sessions. 278 While using Half Trickle does provide a working solution it also 279 comes at the price of increased latency. Section 5 therefore makes 280 several alternative suggestions that enable SIP UAs to engage in Full 281 Trickle right from their first Offer: Section 5.1 discusses the use 282 of on-line provisioning as a means of allowing use of Trickle ICE for 283 all endpoints in controlled environments. Section 5.2 describes 284 anticipatory discovery for implementations that actually do support 285 GRUU and UA Capabilities and Section 5.4 discusses the implementation 286 and use of Half Trickle by SIP UAs where none of the above are an 287 option. 289 3.3. Relationship with the Offer/Answer Model 291 It is important to note that this specification does not require, 292 define, or even assume any mechanisms that would have an impact on 293 the Offer/Answer model beyond the way it is already used by Vanilla 294 ICE [RFC5245]. From the perspective of all SIP middle boxes and 295 proxies, and with the exception of the actual INFO messages, 296 signalling in general and Offer/Answer exchanges in particular would 297 look the same way for Trickle ICE as they would for Vanilla ICE. 299 +-------------------------------+ +-------------------------------+ 300 | Alice +--------------+ | | +--------------+ Bob | 301 | | Offer/Answer | | | | Offer/Answer | | 302 | +-------+ | Module | | | | Module | +-------+ | 303 | | ICE | +--------------+ | | +--------------+ | ICE | | 304 | | Agent | | | | | | Agent | | 305 | +-------+ | | | | +-------+ | 306 +-------------------------------+ +-------------------------------+ 307 | | | | 308 | | INVITE (Offer) | | 309 | |--------------------->| | 310 | | 183 (Answer) | | 311 | |<---------------------| | 312 | | | | 313 | | 314 | SIP INFO (more candidates) | 315 |----------------------------------------------------->| 316 | SIP INFO (more candidates) | 317 |<-----------------------------------------------------| 318 | | 319 | STUN Binding Requests/Responses | 320 |----------------------------------------------------->| 321 | STUN Binding Requests/Responses | 322 |<-----------------------------------------------------| 323 | | 324 | | | | 325 | | 5245 SIP re-INVITE | | 326 | |--------------------->| | 327 | | 200 OK | | 328 | |<---------------------| | 330 Figure 2: Distinguishing between Trickle ICE and traditional 331 signalling. 333 It is important to note that, as displayed on Figure 2, exchanging 334 candidates through SIP INFO messages are best represented as 335 signalling between ICE agents and not between the traditional SIP and 336 Offer/Answer modules of SIP User Agents. Such INFO requests do not 337 impact the state of Offer/Answer, nor do they have an impact on the 338 version number in the "o=" line. In that regard they are actually 339 comparable to Peer Reflexive candidates that ICE agents can discover 340 during ICE processing. 342 4. Incremental Signalling of ICE candidates 344 Trickle ICE agents will construct Offers and Answers as specified in 345 [I-D.ietf-mmusic-trickle-ice] with the following additional SIP- 346 specific additions: 348 1. Trickle ICE agents MUST indicate support for Trickle ICE by 349 including the option-tag 'trickle-ice' in a SIP Supported: header 350 field within all SIP INVITE requests and responses. 352 2. Trickle ICE agents MAY exchange additional ICE candidates using 353 INFO requests within an existing invite dialog usage (including 354 an early dialog) as specified in [RFC6086]. The INFO messages 355 carry an Info-Package: trickle-ice. Trickle ICE agents MUST be 356 prepared to receive INFO requests within that same dialog usage, 357 containing additional candidates or an indication for the end of 358 such candidates 360 3. Trickle ICE agents MAY exchange additional ICE candidates before 361 the Answerer has sent the Answer provided that an invite dialog 362 usage is established at both Trickle ICE agents. Note that in 363 case of forking multiple early dialogs will exist. 365 The following section provide further details on how Trickle ICE 366 agents establish the INVITE dialog usage such that they can trickle 367 candidates. 369 4.1. Establishing the dialog 371 In order for SIP UAs to be able to start trickling, the following two 372 conditions need to be satisfied: 374 o Trickle ICE support in the peer agent MUST be confirmed. 376 o The SIP dialog at both sides MUST be at least in the early state. 378 Section 5 discusses in detail the various options for satisfying the 379 first of the above conditions. Regardless of those mechanisms 380 however, agents are certain to have a clear understanding of whether 381 their peers support trickle ICE once an Offer and an Answer have been 382 exchanged, which also allows for ICE processing to commence (see 383 Figure 3). 385 4.1.1. Asserting dialog state through reliable Offer/Answer delivery 386 Alice Bob 387 | | 388 | INVITE (Offer) | 389 |------------------------>| 390 | 183 (Answer) | 391 |<------------------------| 392 | PRACK/OK | 393 |------------------------>| 394 | | 395 +----------------------------------------+ 396 |Alice and Bob know that both can trickle| 397 |and know that the dialog is in the early| 398 |state. Send INFO! | 399 +----------------------------------------+ 400 | | 401 | INFO/OK (SRFLX Cand.) | 402 |------------------------>| 403 | INFO/OK (SRFLX Cand.) | 404 |<------------------------| 405 | | 407 Figure 3: SIP Offerer can freely trickle as soon as it receives an 408 Answer. 410 Satisfying both conditions is also relatively trivial for ICE agents 411 that have sent an Offer in an INVITE and that have received an Answer 412 in a reliable provisioanl response. It is guaranteed to have 413 confirmed support for Trickle ICE within the Answerer (or lack 414 thereof) and to have fully initialized the SIP dialog at both ends. 415 Offerers and Answerers in the above situation can therefore freely 416 commence trickling within the newly established dialog. 418 4.1.2. Asserting dialog state through unreliable Offer/Answer delivery 420 The situation is a bit more delicate for agents that have received an 421 Offer in an INVITE request and have sent an Answer in an unreliable 422 provisional response because, once the response has been sent, the 423 Answerer does no know when or if it has been received (Figure 4). 425 Alice Bob 426 | | 427 | INVITE (Offer) | 428 |------------------------>| 429 | 183 (Answer) | 430 |<------------------------| 431 | | 432 | +----------------------+ 433 | |Bob: I don't know if | 434 | |Alice got my 183 or if| 435 | |her dialog is already | 436 | |in the early state. | 437 | | Can I send INFO??? | 438 | +----------------------+ 439 | | 441 Figure 4: A SIP UA that sent an Answer in an unreliable provisional 442 response does not know if it was received and if the dialog at the 443 side of the Offerer has entered the early state 445 In order to clear this ambiguity as soon as possible, the answerer 446 needs to retransmit the provisional response with the exponential 447 backoff timers described in [RFC3262]. Retransmits MUST cease on 448 receipt of a INFO request or on transmission of the answer in a 2xx 449 response. This is similar to the procedure described in section 450 12.1.1 of [RFC5245] except that the STUN binding Request is replaced 451 by the INFO request. 453 The Offerer MUST send a Trickle ICE INFO request as soon as they 454 receive an SDP Answer in an unreliable provisional response. This 455 INFO message can repeat the candidates that were already provided in 456 the Offer (as would be the case when Half Trickle is performed or 457 when new candidates have not been learned since then) or they can 458 also deliver new new candidates (if available). An end-of-candidates 459 indication MAY be included in case candidate discovery has ended in 460 the mean time. 462 As soon as an Answerer has received such an INFO request, the 463 Answerer has an indication that a dialog is well established at both 464 ends and MAY begin trickling (Figure 5). 466 Alice Bob 467 | | 468 | INVITE (Offer) | 469 |------------------------>| 470 | 183 (Answer) | 471 |<------------------------| 472 | INFO/OK (SRFLX Cand.) | 473 |------------------------>| 474 | | 475 | +----------------------+ 476 | |Bob: Now I know Alice| 477 | | is ready. Send INFO! | 478 | +----------------------+ 479 | INFO/OK (SRFLX Cand.) | 480 |<------------------------| 481 | | 482 | 200/ACK (Answer) | 483 |<------------------------| 485 Figure 5: A SIP UA that received an INFO request after sending an 486 unreliable provisional response knows that the dialog at the side of 487 the receiver has entered the early state 489 When sending the Answer in the 200 OK response, the Answerers MUST 490 repeat exactly the same Answer that was previously sent in the 491 unreliable provisional response in order to fulfill the corresponding 492 requirements in [RFC3264]. In other words, that Offerer needs to be 493 prepared to receive less candidates in that repeated Answer than 494 previously exchanged via trickling. 496 4.1.3. Initiating Trickle ICE without an SDP Answer 498 The possibility to convey arbitrary SDP fragments in SIPfrag message 499 bodies [I-D.ivov-mmusic-sdpfrag] allows ICE agents to initiate 500 trickling without actually sending an Answer. Trickle ICE Agents MAY 501 therefore respond to INVITEs with provisional responses without an 502 Answer that only serve for establishing an early dialog. 504 Agents that choose to establish the dialog in this way, M UST 505 retransmit these responses with the exponential backoff timers 506 described in [RFC3262]. Retransmits MUST cease on receipt of an INFO 507 request or on transmission of the answer in a 2xx response. This is 508 again similar to the procedure described in section 12.1.1 of 509 [RFC5245] except that an Answer is not yet provided. 511 Alice Bob 512 | | 513 | INVITE (Offer) | 514 |------------------------>| 515 | 183 (-) | 516 |<------------------------| 517 | INFO/OK (SRFLX Cand.) | 518 |------------------------>| 519 | | 520 | +----------------------+ 521 | |Bob: Now I know again| 522 | | that Alice is ready. | 523 | | Send INFO! | 524 | +----------------------+ 525 | INFO/OK (SRFLX Cand.) | 526 |<------------------------| 527 | 183 (Answer) opt. | 528 |<------------------------| 529 | INFO/OK (SRFLX Cand.) | 530 |<------------------------| 531 | 200/ACK (Answer) | 532 |<------------------------| 534 Figure 6: A SIP UA sends an unreliable provisional response without 535 an Answer for establishing an early dialog 537 When sending the Answer the agent MUST repeat all previously sent 538 candidates, if any, and MAY include all newly gathered candidates 539 since the last INFO request was sent. If that answer was sent in a 540 unreliable provisional response, the Answerers MUST repeat exactly 541 the same Answer in the 200 OK response in order to fulfill the 542 corresponding requirements in [RFC3264]. In other words, an Offerer 543 needs to be prepared to receive less candidates in that repeated 544 Answer than previously exchanged via trickling. 546 4.1.4. Considerations for 3PCC 548 Agents that have sent an Offer in a reliable provisional response and 549 that receive an Answer in a PRACK are also in a situation where 550 support for Trickle ICE is confirmed and the SIP dialog is guaranteed 551 to be in a state that would allow in-dialog INFO requests (see 552 Figure 7). 554 Alice Bob 555 | | 556 | INVITE | 557 |------------------------>| 558 | 183 (Offer) | 559 |<------------------------| 560 | PRACK (Answer) | 561 |------------------------>| 562 | | 563 | +----------------------+ 564 | |Bob: I know Alice can| 565 | |trickle and I know her| 566 | |dialog is in the early| 567 | |state. Send INFO! | 568 | +----------------------+ 569 | | 570 | INFO/OK (SRFLX Cand.) | 571 |<------------------------| 572 | | 573 | INFO/OK (SRFLX Cand.) | 574 |------------------------>| 575 | 200 OK/ACK | 576 |<------------------------| 578 Figure 7: A SIP Offerer in a 3PCC scenario can also freely start 579 trickling as soon as it receives an Answer. 581 Trickle Agents that send an Offer in a 200 OK and receive an Answer 582 in an ACK can still create a dialog and confirm support for Trickle 583 ICE by sending an unreliable provisional response similar to 584 Section 4.1.3. According to [RFC3261], this unreliable response MUST 585 NOT contain an Offer. 587 The Trickle Agent (at the UAS) retransmits the provisional response 588 with the exponential backoff timers described in [RFC3262]. 589 Retransmits MUST cease on receipt of a INFO request or on 590 transmission of the answer in a 2xx response. The peer Trickle Agent 591 (at the UAC) MUST send a Trickle ICE INFO request as soon as they 592 receive an unreliable provisional response (see Figure 8). 594 Alice Bob 595 | | 596 | INVITE | 597 |------------------------>| 598 | 183 (-) | 599 |<------------------------| 600 | INFO/OK (SRFLX Cand.) | 601 |------------------------>| 602 | | 603 | +-----------------------+ 604 | |Bob: I know Alice can | 605 | |trickle and I know her | 606 | |dialog is in the early | 607 | |state. | 608 | |INFO can be sent. | 609 | +-----------------------+ 610 | | 611 | INFO/OK (SRFLX Cand.) | 612 |<------------------------| 613 | | 614 | 200 (Offer) | 615 |<------------------------| 616 | ACK (Answer) | 617 |------------------------>| 618 | | 620 Figure 8: A SIP UAC in a 3PCC scenario can also freely start 621 trickling as soon as it receives an unreliable provisional response. 623 4.2. Delivering candidates in INFO messages 625 Whenever new ICE candidates become available for sending, agents 626 would encode them in "a=candidate" lines as described by 627 [I-D.ietf-mmusic-trickle-ice]. For example: 629 a=candidate:2 1 UDP 1694498815 192.0.2.3 5000 typ srflx 630 raddr 10.0.1.1 rport 8998 632 The use of SIP INFO requests happens within the context of the Info 633 Package as defined Section 9. The MIME type for their payload MUST 634 be set to 'application/sdpfrag' as defined in Section 8. 636 Since neither the "a=candidate" nor the "a=end-of-candidates" 637 attributes contain information that would allow correlating them to a 638 specific "m=" line, this is handled through the use of pseudo "m=" 639 lines and identification tags in "a=mid:" attributes as defined in 641 [RFC5888]. Pseudo "m=" lines follow the SDP syntax for "m=" lines as 642 defined in [I-D.ietf-mmusic-rfc4566bis], but provide no semantics 643 other than indicating to which "m=" line a candidate belongs. 644 Consequently, the receiving agent MUST ignore the remaining content 645 of the pseudo m-line. This guarantees that the 'application/sdpfrag' 646 bodies do not interfere with the Offer/Answer procedures as specified 647 in [RFC3264]. 649 When sending the INFO request, the agent MAY, if already known to the 650 agent, include the same content into the pseudo m-line as for the 651 corresponding Offer or Answer. However, since Trickle-ICE might be 652 decoupled from the Offer/Answer negotiation this content might be 653 unknown to the agent. In this case, the agent MUST include the 654 following default values. 656 o The media is set to 'audio'. 658 o The port value is set to '9'. 660 o The proto value is set to 'RTP/AVP'. 662 o The fmt SHOULD appear only once and is set to '0' 664 Agents MUST include a pseudo "m=" line and an identification tag in a 665 "a=mid:" attribute for every "m=" line whose candidate list they 666 intend to update. Such "a=mid:" attributes MUST immediately precede 667 the list of candidates for that specific "m=" line. All 668 "a=candidate" or "a=end-of-candidates" attributes following an 669 "a=mid:" attribute, up until (and excluding) the next occurrence of 670 an "a=mid:" attribute, pertain to the "m=" line identified by that 671 identification tag. An "a=end-of-candidates" attribute, preceding 672 any "a=mid:" attributes, indicates the end of all trickling from that 673 agent, as opposed to end of trickling for a specific "m=" line, which 674 would be indicated by a media level "a=end-of-candidates" attribute. 676 The use of "a=mid:" attributes allows for a structure similar to the 677 one in SDP Offers and Answers where separate media-level and session- 678 level sections can be distinguished. In the current case, lines 679 preceding any "a=mid:" attributes are considered to be session-level. 680 Lines appearing in between or after "a=mid:" attributes will be 681 interpreted as media-level. 683 Note that while this specification uses the "a=mid:" attribute 684 from [RFC5888], it does not define any grouping semantics. 685 Consequently, using the "a=group:" attribute from that same 686 specification is neither needed nor used in Trickle ICE for SIP. 688 All INFO requests MUST carry the "a=ice-pwd:" and "a=ice-ufrag:" 689 attributes that would allow mapping them to a specific ICE 690 generation. INFO requests containing "a=ice-pwd:" and "a=ice-ufrag:" 691 attributes that do not match those of the current ICE processing 692 session MUST be discarded. The "a=ice-pwd:" and "a=ice-ufrag:" 693 attributes MUST appear at the same level as the ones in the Offer/ 694 Answer exchange. In other words, if they were present as sesssion- 695 level attributes there, they will also appear at the beginning of all 696 INFO message payloads, preceding all "a=mid:" attributes. If they 697 were originally exchanged as media level attributes, potentially 698 overriding session-level values, then they will also be included in 699 INFO message payloads, following the corresponding "a=mid:" 700 attribute. 702 In every INFO request agents MUST include all local candidates they 703 have previously signalled. This is necessary in order to more easily 704 avoid problems that would arise from unreliability. Misordering can 705 be detected through the CSeq: header field in the INFO request. 707 When receiving INFO requests carrying any candidates, agents will 708 therefore first identify and discard the SDP lines containing 709 candidates they have already received in previous INFO requests or in 710 the Offer/Answer exchange preceding them. Two candidates are 711 considered to be equal if their IP address port, transport and 712 component ID are the same. After identifying and discarding known 713 candidates, agents will then process the remaining, actually new 714 candidates according to the rules described in 715 [I-D.ietf-mmusic-trickle-ice]. 717 The following example shows the content of one sample candidate 718 delivering INFO request: 720 INFO sip:alice@example.com SIP/2.0 721 ... 722 Info-Package: trickle-ice 723 Content-type: application/sdp 724 Content-Disposition: Info-Package 725 Content-length: ... 727 a=ice-pwd:asd88fgpdd777uzjYhagZg 728 a=ice-ufrag:8hhY 729 m=audio 9 RTP/AVP 0 730 a=mid:1 731 a=candidate:1 1 UDP 1658497328 192.168.100.33 5000 typ host 732 a=candidate:2 1 UDP 1658497328 96.1.2.3 5000 typ srflx 733 raddr 10.0.1.1 rport 8998 734 a=end-of-candidates 735 m=audio 9 RTP/AVP 0 736 a=mid:2 737 a=candidate:2 1 UDP 1658497328 96.1.2.3 5002 typ srflx 738 raddr 10.0.1.1 rport 9000 739 a=end-of-candidates 741 5. Initial discovery of Trickle ICE support 743 SIP User Agents (UAs) that support and intend to use trickle ICE are 744 REQUIRED by [I-D.ietf-mmusic-trickle-ice] to indicate that in their 745 Offers and Answers using the following attribute: "a=ice- 746 options:trickle". This makes discovery fairly straightforward for 747 Answerers or for cases where Offers need to be generated within 748 existing dialogs (i.e., when sending re-INVITE requests). In both 749 scenarios prior SDP would have provided the necessary information. 751 Obviously, prior SDP is not available at the time a first Offer is 752 being constructed and it is therefore impossible for ICE agents to 753 determine support for incremental provisioning that way. The 754 following options are suggested as ways of addressing this issue. 756 5.1. Provisioning support for Trickle ICE 758 In certain situations it may be possible for integrators deploying 759 Trickle ICE to know in advance that some or all endpoints reachable 760 from within the deployment will support Trickle ICE. This is likely 761 to be the case, for example, for WebRTC clients that will always be 762 communicating with other WebRTC clients or known Session Border 763 Controllers (SBC) with support for this specification. 765 While the exact mechanism for allowing such provisioning is out of 766 scope here, this specification encourages trickle ICE implementations 767 to allow the option in the way they find most appropriate. 769 5.2. Trickle ICE discovery with GRUU 771 [RFC3840] provides a way for SIP user agents to query for support of 772 specific capabilities using, among others, OPTIONS requests. GRUU 773 support on the other hand allows SIP requests to be addressed to 774 specific UAs (as opposed to arbitrary instances of an address of 775 record). Combining the two and using the "trickle-ice" option tag 776 defined in Section 9.5 provides SIP UAs with a way of learning the 777 capabilities of specific US instances and then addressing them 778 directly with INVITE requests that require SIP support. 780 Such targeted trickling may happen in different ways. One option 781 would be for a SIP UA to learn the GRUU instance ID of a peer through 782 presence and to then query its capabilities direction with an OPTIONS 783 request. Alternately, it can also just send an OPTIONS request to 784 the AOR it intends to contact and then inspect the returned 785 response(s) for support of both GRUU and Trickle ICE (Figure 9). 787 Alice Bob 788 | | 789 | OPTIONS sip:b1@example.com SIP/2.0 | 790 |-------------------------------------------------->| 791 | | 792 | 200 OK | 793 | Contact: sip:b1@example.com;gr=hha9s8d-999a | 794 | ;audio;video|;trickle-ice;... | 795 |<--------------------------------------------------| 796 | | 797 | INVITE sip:b1@example.com;gr=hha9s8d-999a SIP/2.0 | 798 |-------------------------------------------------->| 799 | | 800 | 183 (Answer) | 801 |<--------------------------------------------------| 802 | INFO/OK (Trickling) | 803 |<------------------------------------------------->| 804 | | 805 | ... | 806 | | 808 Figure 9: Trickle ICE support discovery with OPTIONS and GRUU 810 Confirming support for Trickle ICE through [RFC3840] gives SIP UAs 811 the options to engage in Full Trickle negotiation (as opposed to the 812 more lengthy Half Trickle) from the very first Offer they send. 814 5.3. Trickle ICE discovery through other protocols 816 Protocols like XMPP [RFC6120] define advanced discovery mechanisms 817 that allow specific features to be queried priory to actually 818 attempting to use them. Solutions like [RFC7081] define ways of 819 using SIP and XMPP together which also provides a way for dual stack 820 SIP+XMPP endpoints to make use of such features and verify Trickle 821 ICE support for a specific SIP endpoint through XMPP. [TODO expand 822 on a specific way to do this or declare as out of scope] 824 5.4. Fallback to Half Trickle 826 In cases where none of the other mechanisms in this section are 827 acceptable, SIP UAs should use the Half Trickle mode defined in 828 [I-D.ietf-mmusic-trickle-ice]. With Half Trickle, agents initiate 829 sessions the same way they would when using Vanilla ICE [RFC5245]. 830 This means that, prior to actually sending an Offer, agents would 831 first gather ICE candidates in a blocking way and then send them all 832 in that Offer. The blocking nature of the process would likely imply 833 that some amount of latency will be accumulated and it is advised 834 that agents try to anticipate it where possible, like for example, 835 when user actions indicate a high likelyhood for an imminent call 836 (e.g., activity on a keypad or a phone going offhook). 838 Using Half Trickle would result in Offers that are compatible with 839 both Vanilla ICE and legacy [RFC3264] endpoints. 841 STUN/Turn STUN/TURN 842 Servers Alice Bob Servers 843 | | | | 844 |<--------------| | | 845 | | | | 846 | | | | 847 | Candidate | | | 848 | | | | 849 | | | | 850 | Discovery | | | 851 | | | | 852 | | | | 853 |-------------->| INVITE (Offer) | | 854 | |------------------------>| | 855 | | 183 (Answer) |-------------->| 856 | |<------------------------| | 857 | | | | 858 | | INFO (more candidates) | Candidate | 859 | |<------------------------| | 860 | | Connectivity Checks | | 861 | |<=======================>| Discovery | 862 | | INFO (more candidates) | | 863 | |<------------------------| | 864 | | Connectivity Checks |<--------------| 865 | |<=======================>| | 866 | | | | 867 | | 200 OK | | 868 | |<------------------------| | 869 | | | | 870 | | 5245 SIP re-INVITE | | 871 | |------------------------>| | 872 | | 200 OK | | 873 | |<------------------------| | 874 | | | | 875 | | | | 876 | |<===== MEDIA FLOWS =====>| | 877 | | | | 879 Figure 10: Example - A typical (Half) Trickle ICE exchange with SIP 881 It is worth reminding that once a single Offer or Answer had been 882 exchanged within a specific dialog, support for Trickle ICE will have 883 been determined. No further use of Half Trickle will therefore be 884 necessary within that same dialog and all subsequent exchanges can 885 use the Full Trickle mode of operation. 887 6. Considerations for RTP and RTCP multiplexing 889 [OPEN ISSUE: These considerations are of general relevance 890 and might be better suited for draft-ietf-mmusic-trickle-ice.] 892 The following consideration describe options for Trickle-ICE in order 893 to give some guidance to implementors on how trickling can be 894 optimized with respect to providing RTCP candidates. However, these 895 considerations are neither meant to be exhaustive nor guaranteed to 896 be suitable for all sorts of deployments. 898 Handling of RTP and RCTP multiplexing [RFC5761] is already considered 899 in sections 4.1.1.1, 4.3, and 5.7.1 of [RFC5245], respectively. 900 These considerations are still valid for Trickle ICE, however, 901 trickling provides more flexibility for the sequence of candidate 902 exchange, e.g. in case of RTCP multiplexing. 904 While a Half Trickle Offerer would have to send an offer compliant to 905 [RFC5245] including candidates for all components, this flexibility 906 allows a Full Trickle Offerer to initially send only RTP candidates 907 (component 1) if it assumes that RTCP multiplexing is supported by 908 the Answerer. A Full Trickle Offerer would need to start gathering 909 and trickling RTCP candidates (component 2) only after having 910 received an indication in the answer that the answerer unexpectedly 911 does not support RTCP multiplexing. 913 A Trickle answerer MAY include an "a=rtcp-mux" attribute [RFC5761] in 914 the application/sdp-frag body if it supports and uses RTP and RCTP 915 multiplexing. Receipt of this attribute at the Offerer in an INFO 916 request prior to the Answer indicates that the Answerer supports and 917 uses RTP and RCTP multiplexing. The Offerer can use this information 918 e.g. for stopping gathering of RTCP candidates and/or for freeing 919 corresponding resources. 921 7. Considerations for Media Multiplexing 923 [OPEN ISSUE: These considerations are of general relevance 924 and might be better suited for draft-ietf-mmusic-trickle-ice.] 926 The following consideration describe options for Trickle-ICE in order 927 to give some guidance to implementors on how trickling can be 928 optimized with respect to providing candidates in case of Media 929 Multiplexing [I-D.ietf-mmusic-sdp-bundle-negotiation]. However, 930 these considerations are neither meant to be exhaustive nor 931 guaranteed to be suitable for all sorts of deployments. 933 ICE candidate exchange is already considered in section 11 of 934 [I-D.ietf-mmusic-sdp-bundle-negotiation]. These considerations are 935 still valid for Trickle ICE, however, trickling provides more 936 flexibility for the sequence of candidate exchange, especially in 937 Full Trickle mode. 939 Except for bundle-only m-lines, a Half Trickle Offerer would have to 940 send an offer with candidates for all bundled m-lines. The 941 additional flexibility, however, allows a Full Trickle Offerer to 942 initially send only candidates for the m-line with the suggested 943 offerer BUNDLE address. 945 Latest on receipt of the answer, the Offerer will detect if BUNDLE is 946 supported and if the suggested offerer BUNDLE address was selected. 947 In this case the Offerer does need to trickle further candidates for 948 the remaining m-lines in a bundle. However, if BUNDLE is not 949 supported, the Full Trickle Offerer needs to gather and trickle 950 candidates for the remaining m-lines as necessary. If the answerer 951 selects a Offerer BUNDLE address different from suggested Offerer 952 BUNDLE address, the Full Trickle Offerer needs to gather and trickle 953 candidates for the m-line that carries the selected Offerer BUNDLE 954 address. 956 A Trickle answerer MAY include an "a=group: BUNDLE" attribute 957 [I-D.ietf-mmusic-sdp-bundle-negotiation] in the application/sdp-frag 958 body if it supports and uses bundling. When doing so, the Answerer 959 MUST include all identification-tags in the same order that is used 960 or will be used in the Answer. 962 Receipt of this attribute at the Offerer in an INFO request prior to 963 the Answer indicates that the Answerer supports and uses bundling. 964 The Offerer can use this information e.g. for stopping the gathering 965 of candidates for the remaining m-lines in a bundle and/or for 966 freeing corresponding resources. 968 8. Content Type 'application/sdpfrag' 970 8.1. Overall Description 972 A valid application/sdpfrag part could be obtained by starting with 973 some valid SDP session description [I-D.ietf-mmusic-rfc4566bis] and 974 deleting any number of lines. 976 The exact content of an 'application/sdpfrag' body MUST be specified 977 the using protocol. This document specifies the content for usage 978 with Trickle ICE. 980 8.2. Grammar 982 This section provides an Augmented BNF grammar for SDP. ABNF is 983 defined in [RFC5234]. 985 The ABNF of an 'application/sdpfrag' body is based on 986 [I-D.ietf-mmusic-rfc4566bis] with the following modification 988 ; SDPfrag Syntax 989 sdp-frag = *1proto-version 990 *1origin-field 991 *1session-name-field 992 *1information-field 993 *1uri-field 994 *1email-fields 995 *1phone-fields 996 *1connection-field 997 *1bandwidth-fields 998 *1time-fields 999 *1key-field 1000 *1attribute-fields 1001 *1media-descriptions 1003 9. Info Package 1005 9.1. Overall Description 1007 This specification defines an Info Package for use by SIP user agents 1008 implementing Trickle ICE. INFO requests carry ICE candidates 1009 discovered after the peer user agents have confirmed mutual support 1010 for Trickle ICE. 1012 9.2. Applicability 1014 The purpose of the ICE protocol is to establish a media path in the 1015 presence of NAT and firewalls. The candidates are transported in 1016 INFO requests and are part of this establishment. 1018 Candidates sent by a Trickle ICE agent after the Offer, follow the 1019 same signalling path and reach the same entity as the Offer itself. 1020 While it is true that GRUUs can be used to achieve this, one of the 1021 goals of this specification is to allow operation of Trickle ICE in 1022 as many environments as possible including those without GRUU 1023 support. Using out-of-dialog SUBSCRIBE/NOTIFY requests would not 1024 satisfy this goal. 1026 9.3. Info Package Name 1028 This document defines a SIP Info Package as per [RFC6086]. The Info 1029 Package token name for this package is "trickle-ice" 1031 9.4. Info Package Parameters 1033 This document does not define any Info Package parameters. 1035 9.5. SIP Option Tags 1037 [RFC6086] allows Info Package specifications to define SIP option- 1038 tags. This specification extends the option-tag construct of the SIP 1039 grammar as follows: 1041 option-tag /= "trickle-ice" 1043 SIP entities that support this specification MUST place the 'trickle- 1044 ice' option-tag in a SIP Supported: header field within all SIP 1045 INVITE requests and responses. 1047 When responding to, or generating a SIP OPTIONS request a SIP entity 1048 MUST also include the 'trickle-ice' option-tag in a SIP Supported: 1049 header field. 1051 9.6. Info Message Body Parts 1053 Entities implementing this specification MUST include SDP encoded ICE 1054 candidates in all SIP INFO requests. The MIME type for the payload 1055 MUST be of type 'application/sdpfrag' as defined in Section 4.2 and 1056 [I-D.ietf-mmusic-trickle-ice]. 1058 The Trickle-ICE Info Package uses only a subset of the possible SDP 1059 Fragments that are allowed based on the grammar defined in 1060 Section 8.2. The package uses only media descriptions and certain 1061 attributes that are needed or useful for trickling candidates. This 1062 subset adheres to the following grammar. 1064 ; Syntax 1065 trickle-ice-sdpfrag = session-level-fields 1066 pseudo-media-descriptions 1067 session-level-fields = [bundle-group-attribute CRLF] 1068 [ice-lite-attribute CRLF] 1069 ice-pwd-attribute CRLF 1070 ice-ufrag-attribute CRLF 1071 [ice-options-attribute CRLF] 1072 [end-of-candidates-attribute CRLF] 1073 extension-attribute-fields ; for future extensions 1074 ice-lite-attribute = %s"a=" ice-lite 1075 ice-pwd-attribute = %s"a=" ice-pwd-att 1076 ice-ufrag-attribute = %s"a=" ice-ufrag-att 1077 ice-options-attribute = %s"a=" ice-options 1078 bundle-group-attribute = "a=group:" bundle-semantics 1079 *(SP identification-tag) 1080 bundle-semantics = "BUNDLE" 1081 end-of-candidates-attribute = %s"a=" end-of-candidates-att 1082 extension-attribute-fields = attribute-fields 1084 pseudo-media-descriptions = *( media-field 1085 trickle-ice-attribute-fields 1086 [extension-attribute-fields] ) ; for future extensions 1087 trickle-ice-attribute-fields = mid-attribute CRLF 1088 ["a=rtcp-mux" CRLF] 1089 *(candidate-attributes CRLF) 1090 [remote-candidate-attribute CRLF] 1091 [end-of-candidates-attribute CRLF] 1092 remote-candidate-attribute = %s"a=" remote-candidate-att 1093 candidate-attributes = %s"a=" candidate-attribute 1095 with ice-lite, ice-pwd-att, remote-candidate-att, ice-ufrag-att, ice- 1096 options, candidate-attribute remote-candidate-att from [RFC5245], 1097 identification-tag, mid-attribute ; from [RFC5888], media-field, 1098 attribute-fields from [I-D.ietf-mmusic-rfc4566bis] and end-of- 1099 candidates-att from [I-D.ietf-mmusic-trickle-ice]. The indicator for 1100 case-sensitivity %s is defined in [RFC7405]. 1102 [NOTE: end-of-candidates-att currently lacks a formal definition in 1103 [I-D.ietf-mmusic-trickle-ice]] 1105 9.7. Info Package Usage Restrictions 1107 This document does not define any Info Package Usage Restrictions. 1109 9.8. Rate of INFO Requests 1111 A Trickle ICE Agent with many network interfaces might create an 1112 excessive rate of INFO requests if every newly detected candidate is 1113 trickled individually without aggregation. Therefore, Trickle ICE 1114 Agent SHOULD wait for XXX ms or longer after the latest INFO request 1115 was sent before for sending newly detected candidates in a subsequent 1116 INFO request. 1118 [OPEN ISSUE: What rate will give a good trade-off? 100ms, 200ms?] 1120 9.9. Info Package Security Considerations 1122 See section Section 11 1124 10. IANA Considerations 1126 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 1127 document.] 1129 10.1. application/sdpfrag MIME Type 1131 Type name: application 1133 Subtype name: sdpfrag 1135 Required parameters: None. 1137 Optional parameters: None. 1139 Encoding considerations: 1141 SDP files are primarily UTF-8 format text. The "a=charset:" 1142 attribute may be used to signal the presence of other character 1143 sets in certain parts of an SDP file (see 1144 [I-D.ietf-mmusic-rfc4566bis]). Arbitrary binary content cannot 1145 be directly represented in SDP. 1147 Security considerations: 1149 See [I-D.ietf-mmusic-rfc4566bis]) and RFCXXXX 1151 Interoperability considerations: 1153 See RFCXXXX 1155 Published specification: 1157 See RFCXXXX 1159 Applications which use this media type: 1161 Voice over IP, video teleconferencing, streaming media, instant 1162 messaging, Trickle-ICE among others. 1164 Additional information: 1166 Magic number(s): none 1168 File extension(s): none 1170 Macintosh File Type Code(s): none 1172 Person and email address to contact for further information: 1174 IETF MMUSIC working group mmusic@ietf.org 1176 Intended usage: 1178 Trickle-ICE for SIP as specified in RFCXXXX. Further usages 1179 need a specification on the exact content of an 'application/ 1180 sdpfrag' body in the using protocol. 1182 Author/Change controller: 1184 IETF MMUSIC working group mmusic@ietf.org 1186 10.2. SIP Info Package 'trickle-ice' 1188 This document defines a new SIP Info Package named 'trickle-ice' and 1189 updates the Info Packages Registry with the following entry. 1191 +-------------+-----------+ 1192 | Name | Reference | 1193 +-------------+-----------+ 1194 | trickle-ice | [RFCXXXX] | 1195 | | | 1196 +-------------+-----------+ 1198 10.3. SIP Option Tag 'trickle-ice' 1200 This specification registers a new SIP option tag 'trickle-ice' as 1201 per the guidelines in Section 27.1 of [RFC3261] and updates the 1202 "Option Tags" section of the SIP Parameter Registry with the 1203 following entry: 1205 +-------------+-------------------------------------------+-----------+ 1206 | Name | Description | Reference | 1207 +-------------+-------------------------------------------+-----------+ 1208 | trickle-ice | This option tag is used to indicate that | [RFCXXXX] | 1209 | | a UA supports and understands Trickle-ICE | | 1210 +-------------+-------------------------------------------+-----------+ 1212 11. Security Considerations 1214 The Security Considerations of [RFC5245], [RFC6086], 1215 [I-D.ietf-mmusic-trickle-ice] apply. This document clarifies how the 1216 above specifications are used together for trickling candidates and 1217 does not create addtitional security risks. 1219 12. Acknowledgements 1221 The authors would like to thank Paul Kyzivat and Jonathan Lennox and 1222 Martin Thomson for making various suggestions for improvements and 1223 optimisations. Adam Roach was co-author of [I-D.ivov-mmusic-sdpfrag] 1224 which was merged into this document. 1226 13. Change Log 1228 [RFC EDITOR NOTE: Please remove this section when publishing]. 1230 Changes from draft-ietf-mmusic-trickle-ice-sip-01 1232 o Editorial Clean up 1234 o IANA Consideration added 1235 o Security Consideration added 1237 o RTCP and BUNDLE Consideration added with rules for including 1238 "a=rtcp-mux" and ""a=group: BUNDLLE" attributes 1240 o 3PCC Consideration added 1242 o Clarified that 18x w/o answer is sufficient to create a dialog 1243 that allows for trickling to start 1245 o Added remaining Info Package definition sections as outlined in 1246 section 10 of [RFC6086] 1248 o Added definition of application/sdpfrag making draft-ivov-mmusic- 1249 sdpfrag obsolete 1251 o Added pseudo m-lines as additional separator in sdpfrag bodies for 1252 Trickle ICE 1254 o Added ABNF for sdp-frag bodies and Trickle-ICE package 1256 14. References 1258 14.1. Normative References 1260 [I-D.ietf-mmusic-rfc4566bis] 1261 Handley, M., Jacobson, V., Perkins, C., and A. Begen, 1262 "SDP: Session Description Protocol", draft-ietf-mmusic- 1263 rfc4566bis-15 (work in progress), May 2015. 1265 [I-D.ietf-mmusic-trickle-ice] 1266 Ivov, E., Rescorla, E., and J. Uberti, "Trickle ICE: 1267 Incremental Provisioning of Candidates for the Interactive 1268 Connectivity Establishment (ICE) Protocol", draft-ietf- 1269 mmusic-trickle-ice-02 (work in progress), January 2015. 1271 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1272 Requirement Levels", BCP 14, RFC 2119, March 1997. 1274 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1275 A., Peterson, J., Sparks, R., Handley, M., and E. 1276 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1277 June 2002. 1279 [RFC3262] Rosenberg, J. and H. Schulzrinne, "Reliability of 1280 Provisional Responses in Session Initiation Protocol 1281 (SIP)", RFC 3262, June 2002. 1283 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 1284 with Session Description Protocol (SDP)", RFC 3264, June 1285 2002. 1287 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 1288 Description Protocol", RFC 4566, July 2006. 1290 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 1291 Specifications: ABNF", STD 68, RFC 5234, January 2008. 1293 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 1294 (ICE): A Protocol for Network Address Translator (NAT) 1295 Traversal for Offer/Answer Protocols", RFC 5245, April 1296 2010. 1298 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description 1299 Protocol (SDP) Grouping Framework", RFC 5888, June 2010. 1301 [RFC6086] Holmberg, C., Burger, E., and H. Kaplan, "Session 1302 Initiation Protocol (SIP) INFO Method and Package 1303 Framework", RFC 6086, January 2011. 1305 [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF", RFC 1306 7405, December 2014. 1308 14.2. Informative References 1310 [I-D.ietf-mmusic-sdp-bundle-negotiation] 1311 Holmberg, C., Alvestrand, H., and C. Jennings, 1312 "Negotiating Media Multiplexing Using the Session 1313 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- 1314 negotiation-22 (work in progress), June 2015. 1316 [I-D.ivov-mmusic-sdpfrag] 1317 Ivov, E. and A. Roach, "Internet Media Type application/ 1318 sdpfrag", draft-ivov-mmusic-sdpfrag-00 (work in progress), 1319 February 2015. 1321 [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, 1322 "Indicating User Agent Capabilities in the Session 1323 Initiation Protocol (SIP)", RFC 3840, August 2004. 1325 [RFC5627] Rosenberg, J., "Obtaining and Using Globally Routable User 1326 Agent URIs (GRUUs) in the Session Initiation Protocol 1327 (SIP)", RFC 5627, October 2009. 1329 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and 1330 Control Packets on a Single Port", RFC 5761, April 2010. 1332 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence 1333 Protocol (XMPP): Core", RFC 6120, March 2011. 1335 [RFC7081] Ivov, E., Saint-Andre, P., and E. Marocco, "CUSAX: 1336 Combined Use of the Session Initiation Protocol (SIP) and 1337 the Extensible Messaging and Presence Protocol (XMPP)", 1338 RFC 7081, November 2013. 1340 Authors' Addresses 1342 Emil Ivov 1343 Jitsi 1344 Strasbourg 67000 1345 France 1347 Phone: +33 6 72 81 15 55 1348 Email: emcho@jitsi.org 1350 Thomas Stach 1351 Unaffiliated 1352 Vienna 1130 1353 Austria 1355 Email: thomass.stach@gmail.com 1357 Enrico Marocco 1358 Telecom Italia 1359 Via G. Reiss Romoli, 274 1360 Turin 10148 1361 Italy 1363 Email: enrico.marocco@telecomitalia.it 1365 Christer Holmberg 1366 Ericsson 1367 Hirsalantie 11 1368 Jorvas 02420 1369 Finland 1371 Email: christer.holmberg@ericsson.com