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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MMUSIC Working Group C. Holmberg 3 Internet-Draft Ericsson 4 Updates: 3264 (if approved) H. Alvestrand 5 Intended status: Standards Track Google 6 Expires: October 16, 2016 C. Jennings 7 Cisco 8 April 14, 2016 10 Negotiating Media Multiplexing Using the Session Description Protocol 11 (SDP) 12 draft-ietf-mmusic-sdp-bundle-negotiation-28.txt 14 Abstract 16 This specification defines a new Session Description Protocol (SDP) 17 Grouping Framework extension, 'BUNDLE'. The extension can be used 18 with the SDP Offer/Answer mechanism to negotiate the usage of a 19 single address:port combination (BUNDLE address) for receiving media, 20 referred to as bundled media, specified by multiple SDP media 21 descriptions ("m=" lines). 23 To assist endpoints in negotiating the use of bundle this 24 specification defines a new SDP attribute, 'bundle-only', which can 25 be used to request that specific media is only used if bundled. 27 There are multiple ways to correlate the bundled RTP packets with the 28 appropriate media descriptions. This specification defines a new 29 Real-time Transport Protocol (RTP) source description (SDES) item and 30 a new RTP header extension that provides an additional way to do this 31 correlation by using them to carry a value that associates the RTP/ 32 RTCP packets with a specific media description. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at http://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on October 16, 2016. 50 Copyright Notice 52 Copyright (c) 2016 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 68 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 6 70 4. Applicability Statement . . . . . . . . . . . . . . . . . . . 7 71 5. SDP Grouping Framework BUNDLE Extension . . . . . . . . . . . 7 72 6. SDP 'bundle-only' Attribute . . . . . . . . . . . . . . . . . 7 73 7. SDP Information Considerations . . . . . . . . . . . . . . . 8 74 7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 8 75 7.2. Connection Data (c=) . . . . . . . . . . . . . . . . . . 9 76 7.3. Bandwidth (b=) . . . . . . . . . . . . . . . . . . . . . 9 77 7.4. Attributes (a=) . . . . . . . . . . . . . . . . . . . . . 9 78 8. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 9 79 8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 9 80 8.2. Mux Category Considerations . . . . . . . . . . . . . . . 10 81 8.3. Generating the Initial SDP Offer . . . . . . . . . . . . 10 82 8.3.1. General . . . . . . . . . . . . . . . . . . . . . . . 10 83 8.3.2. Suggesting the offerer BUNDLE address . . . . . . . . 11 84 8.4. Generating the SDP Answer . . . . . . . . . . . . . . . . 11 85 8.4.1. General . . . . . . . . . . . . . . . . . . . . . . . 11 86 8.4.2. Answerer Selection of Offerer Bundle Address . . . . 12 87 8.4.3. Answerer Selection of Answerer BUNDLE Address . . . . 13 88 8.4.4. Moving A Media Description Out Of A BUNDLE Group . . 13 89 8.4.5. Rejecting A Media Description In A BUNDLE Group . . . 14 90 8.5. Offerer Processing of the SDP Answer . . . . . . . . . . 14 91 8.6. Modifying the Session . . . . . . . . . . . . . . . . . . 14 92 8.6.1. General . . . . . . . . . . . . . . . . . . . . . . . 14 93 8.6.2. Suggesting a new offerer BUNDLE address . . . . . . . 15 94 8.6.3. Adding a media description to a BUNDLE group . . . . 15 95 8.6.4. Moving A Media Description Out Of A BUNDLE Group . . 16 96 8.6.5. Disabling A Media Description In A BUNDLE Group . . . 16 97 9. Protocol Identification . . . . . . . . . . . . . . . . . . . 17 98 9.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 17 99 9.2. STUN, DTLS, SRTP . . . . . . . . . . . . . . . . . . . . 17 100 10. RTP Considerations . . . . . . . . . . . . . . . . . . . . . 18 101 10.1. Single RTP Session . . . . . . . . . . . . . . . . . . . 18 102 10.1.1. General . . . . . . . . . . . . . . . . . . . . . . 18 103 10.1.2. Payload Type (PT) Value Reuse . . . . . . . . . . . 19 104 10.2. Associating RTP/RTCP Packets With Correct SDP Media 105 Description . . . . . . . . . . . . . . . . . . . . . . 19 106 10.3. RTP/RTCP Multiplexing . . . . . . . . . . . . . . . . . 20 107 10.3.1. General . . . . . . . . . . . . . . . . . . . . . . 20 108 10.3.2. SDP Offer/Answer Procedures . . . . . . . . . . . . 20 109 11. ICE Considerations . . . . . . . . . . . . . . . . . . . . . 22 110 11.1. General . . . . . . . . . . . . . . . . . . . . . . . . 22 111 11.2. SDP Offer/Answer Procedures . . . . . . . . . . . . . . 23 112 11.2.1. General . . . . . . . . . . . . . . . . . . . . . . 23 113 11.2.2. Generating the Initial SDP Offer . . . . . . . . . . 23 114 11.2.3. Generating the SDP Answer . . . . . . . . . . . . . 24 115 11.2.4. Offerer Processing of the SDP Answer . . . . . . . . 24 116 11.2.5. Modifying the Session . . . . . . . . . . . . . . . 24 117 12. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 24 118 13. Update to RFC 3264 . . . . . . . . . . . . . . . . . . . . . 25 119 13.1. General . . . . . . . . . . . . . . . . . . . . . . . . 25 120 13.2. Original text of section 5.1 (2nd paragraph) of RFC 3264 25 121 13.3. New text replacing section 5.1 (2nd paragraph) of RFC 122 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 25 123 13.4. Original text of section 8.2 (2nd paragraph) of RFC 3264 26 124 13.5. New text replacing section 8.2 (2nd paragraph) of RFC 125 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 26 126 13.6. Original text of section 8.4 (6th paragraph) of RFC 3264 26 127 13.7. New text replacing section 8.4 (6th paragraph) of RFC 128 3264 . . . . . . . . . . . . . . . . . . . . . . . . . . 26 129 14. RTP/RTCP extensions for identification-tag transport . . . . 27 130 14.1. General . . . . . . . . . . . . . . . . . . . . . . . . 27 131 14.2. RTCP MID SDES Item . . . . . . . . . . . . . . . . . . . 28 132 14.3. RTP MID Header Extension . . . . . . . . . . . . . . . . 28 133 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 134 15.1. New SDES item . . . . . . . . . . . . . . . . . . . . . 29 135 15.2. New RTP Header Extension URI . . . . . . . . . . . . . . 29 136 15.3. New SDP Attribute . . . . . . . . . . . . . . . . . . . 29 137 15.4. New SDP Group Semantics . . . . . . . . . . . . . . . . 30 138 16. Security Considerations . . . . . . . . . . . . . . . . . . . 30 139 17. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 31 140 17.1. Example: Bundle Address Selection . . . . . . . . . . . 31 141 17.2. Example: BUNDLE Extension Rejected . . . . . . . . . . . 33 142 17.3. Example: Offerer Adds A Media Description To A BUNDLE 143 Group . . . . . . . . . . . . . . . . . . . . . . . . . 34 145 17.4. Example: Offerer Moves A Media Description Out Of A 146 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 36 147 17.5. Example: Offerer Disables A Media Description Within A 148 BUNDLE Group . . . . . . . . . . . . . . . . . . . . . . 37 149 18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 39 150 19. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 39 151 20. References . . . . . . . . . . . . . . . . . . . . . . . . . 46 152 20.1. Normative References . . . . . . . . . . . . . . . . . . 46 153 20.2. Informative References . . . . . . . . . . . . . . . . . 47 154 Appendix A. Design Considerations . . . . . . . . . . . . . . . 48 155 A.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 48 156 A.2. UA Interoperability . . . . . . . . . . . . . . . . . . . 49 157 A.3. Usage of port number value zero . . . . . . . . . . . . . 50 158 A.4. B2BUA And Proxy Interoperability . . . . . . . . . . . . 50 159 A.4.1. Traffic Policing . . . . . . . . . . . . . . . . . . 51 160 A.4.2. Bandwidth Allocation . . . . . . . . . . . . . . . . 51 161 A.5. Candidate Gathering . . . . . . . . . . . . . . . . . . . 52 162 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52 164 1. Introduction 166 This specification defines a way to use a single address:port 167 combination (BUNDLE address) for receiving media specified by 168 multiple SDP media descriptions ("m=" lines). 170 This specification defines a new SDP Grouping Framework [RFC5888] 171 extension called 'BUNDLE'. The extension can be used with the 172 Session Description Protocol (SDP) Offer/Answer mechanism [RFC3264] 173 to negotiate the usage of a BUNDLE group. Within the BUNDLE group, a 174 BUNDLE address is used for receiving media specified by multiple "m=" 175 lines. This is referred to as bundled media. 177 The offerer and answerer [RFC3264] use the BUNDLE extension to 178 negotiate the BUNDLE addresses, one for the offerer (offerer BUNDLE 179 address) and one for the answerer (answerer BUNDLE address), to be 180 used for receiving the bundled media specified by a BUNDLE group. 181 Once the offerer and the answerer have negotiated a BUNDLE group, 182 they associate their respective BUNDLE address with each "m=" line in 183 the BUNDLE group. The BUNDLE addresses are used to receive all media 184 specified by the BUNDLE group. 186 The use of a BUNDLE group and a BUNDLE address also allows the usage 187 of a single set of Interactive Connectivity Establishment (ICE) 188 [I-D.ietf-ice-rfc5245bis] candidates for multiple "m=" lines. 190 This specification also defines a new SDP attribute, 'bundle-only', 191 which can be used to request that specific media is only used if kept 192 within a BUNDLE group. 194 As defined in RFC 4566 [RFC4566], the semantics of assigning the same 195 port value to multiple "m=" lines are undefined, and there is no 196 grouping defined by such means. Instead, an explicit grouping 197 mechanism needs to be used to express the intended semantics. This 198 specification provides such an extension. 200 This specification also updates sections 5.1, 8.1 and 8.2 of RFC 3264 201 [RFC3264]. The update allows an answerer to assign a non-zero port 202 value to an "m=" line in an SDP answer, even if the "m=" line in the 203 associated SDP offer contained a zero port value. 205 This specification also defines a new Real-time Transport Protocol 206 (RTP) [RFC3550] source description (SDES) item and a new RTP header 207 extension that can be used to carry a value that associates RTP/RTCP 208 packets with a specific media description. This can be used to 209 correlate a RTP packet with the correct media. 211 SDP bodies can contain multiple BUNDLE groups. A given BUNDLE 212 address MUST only be associated with a single BUNDLE group. The 213 procedures in this specification apply independently to a given 214 BUNDLE group. All RTP based media flows described by a single BUNDLE 215 group belong to a single RTP session [RFC3550]. 217 The BUNDLE extension is backward compatible. Endpoints that do not 218 support the extension are expected to generate offers and answers 219 without an SDP 'group:BUNDLE' attribute, and are expected to 220 associate a unique address with each "m=" line within an offer and 221 answer, according to the procedures in [RFC4566] and [RFC3264] 223 2. Terminology 225 "m=" line: SDP bodies contain one or more media descriptions. Each 226 media description is identified by an SDP "m=" line. 228 5-tuple: A collection of the following values: source address, source 229 port, destination address, destination port, and transport-layer 230 protocol. 232 Unique address: An IP address and port combination that is associated 233 with only one "m=" line in an offer or answer. 235 Shared address: An IP address and port combination that is associated 236 with multiple "m=" lines within an offer or answer. 238 Offerer BUNDLE-tag: The first identification-tag in a given SDP 239 'group:BUNDLE' attribute identification-tag list in an offer. 241 Answerer BUNDLE-tag: The first identification-tag in a given SDP 242 'group:BUNDLE' attribute identification-tag list in an answer. 244 Offerer BUNDLE address: Within a given BUNDLE group, an IP address 245 and port combination used by an offerer to receive all media 246 specified by each "m=" line within the BUNDLE group. 248 Answerer BUNDLE address: Within a given BUNDLE group, an IP address 249 and port combination used by an answerer to receive all media 250 specified by each "m=" line within the BUNDLE group. 252 BUNDLE group: A set of "m=" lines, created using an SDP Offer/Answer 253 exchange, which uses the same BUNDLE address for receiving media. 255 Bundled "m=" line: An "m=" line, whose identification-tag is placed 256 in an SDP 'group:BUNDLE' attribute identification-tag list in an 257 offer or answer. 259 Bundle-only "m=" line: A bundled "m=" line with an associated SDP 260 'bundle-only' attribute. 262 Bundled media: All media specified by a given BUNDLE group. 264 Initial offer: The first offer, within an SDP session (e.g. a SIP 265 dialog when the Session Initiation Protocol (SIP) [RFC3261] is used 266 to carry SDP), in which the offerer indicates that it wants to create 267 a given BUNDLE group. 269 Subsequent offer: An offer which contains a BUNDLE group that has 270 been created as part of a previous offer/answer exchange. 272 Identification-tag: A unique token value that is used to identify an 273 "m=" line. The SDP 'mid' attribute [RFC5888], associated with an 274 "m=" line, carries an unique identification-tag. The session-level 275 SDP 'group' attribute [RFC5888] carries a list of identification- 276 tags, identifying the "m=" lines associated with that particular 277 'group' attribute. 279 3. Conventions 281 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 282 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 283 document are to be interpreted as described in BCP 14, RFC 2119 284 [RFC2119]. 286 4. Applicability Statement 288 The mechanism in this specification only applies to the Session 289 Description Protocol (SDP) [RFC4566], when used together with the SDP 290 offer/answer mechanism [RFC3264]. Declarative usage of SDP is out of 291 scope of this document, and is thus undefined. 293 5. SDP Grouping Framework BUNDLE Extension 295 This section defines a new SDP Grouping Framework extension 296 [RFC5888], 'BUNDLE'. The BUNDLE extension can be used with the SDP 297 Offer/Answer mechanism to negotiate the usage of a single 298 address:port combination (BUNDLE address) for receiving bundled 299 media. 301 A single address:port combination is also used for sending bundled 302 media. The address:port combination used for sending bundled media 303 MAY be the same as the BUNDLE address, used to receive bundled media, 304 depending on whether symmetric RTP [RFC4961] is used. 306 All media specified by a BUNDLE group share a single 5-tuple, i.e. in 307 addition to using a single address:port combination all bundled media 308 MUST be transported using the same transport-layer protocol (e.g. 309 UDP or TCP). 311 The BUNDLE extension is indicated using an SDP 'group' attribute with 312 a "BUNDLE" semantics value [RFC5888]. An identification-tag is 313 associated with each bundled "m=" line, and each identification-tag 314 is listed in the SDP 'group:BUNDLE' attribute identification-tag 315 list. Each "m=" line whose identification-tag is listed in the 316 identification-tag list is associated with a given BUNDLE group. 318 SDP bodies can contain multiple BUNDLE groups. Any given bundled 319 "m=" line MUST NOT be associated with more than one BUNDLE group. 321 Section 8 defines the detailed SDP Offer/Answer procedures for the 322 BUNDLE extension. 324 6. SDP 'bundle-only' Attribute 326 This section defines a new SDP media-level attribute [RFC4566], 327 'bundle-only'. 'bundle-only' is a property attribute [RFC4566], and 328 hence has no value. 330 Name: bundle-only 332 Value: N/A 334 Usage Level: media 336 Charset Dependent: no 338 Example: 340 a=bundle-only 342 In order to ensure that an answerer that does not support the BUNDLE 343 extension always rejects a bundled "m=" line, the offerer can assign 344 a zero port value to the "m=" line. According to [RFC4566] an 345 answerer will reject such "m=" line. By associating an SDP 'bundle- 346 only' attribute with such "m=" line, the offerer can request that the 347 answerer accepts the "m=" line if the answerer supports the Bundle 348 extension, and if the answerer keeps the "m=" line within the 349 associated BUNDLE group. 351 NOTE: Once the offerer BUNDLE address has been selected, the offerer 352 does not need to include the 'bundle-only' attribute in subsequent 353 offers. By associating the offerer BUNDLE address with an "m=" line 354 of a subsequent offer, the offerer will ensure that the answerer will 355 either keep the "m=" line within the BUNDLE group, or the answerer 356 will have to reject the "m=" line. 358 The usage of the 'bundle-only' attribute is only defined for a 359 bundled "m=" line with a zero port value, within an offer. Other 360 usage is unspecified. 362 Section 8 defines the detailed SDP Offer/Answer procedures for the 363 'bundle-only' attribute. 365 7. SDP Information Considerations 367 7.1. General 369 This section describes restrictions associated with the usage of SDP 370 parameters within a BUNDLE group. It also describes, when parameter 371 and attribute values have been associated with each bundled "m=" 372 line, how to calculate a value for the whole BUNDLE group. 374 7.2. Connection Data (c=) 376 The "c=" line nettype value [RFC4566] associated with a bundled "m=" 377 line MUST be 'IN'. 379 The "c=" line addrtype value [RFC4566] associated with a bundled "m=" 380 line MUST be 'IP4' or 'IP6'. The same value MUST be associated with 381 each "m=" line. 383 NOTE: Extensions to this specification can specify usage of the 384 BUNDLE mechanism for other nettype and addrtype values than the ones 385 listed above. 387 7.3. Bandwidth (b=) 389 An offerer and answerer MUST use the rules and restrictions defined 390 in [I-D.ietf-mmusic-sdp-mux-attributes] for when associating the SDP 391 bandwidth (b=) line with bundled "m=" lines. 393 7.4. Attributes (a=) 395 An offerer and answerer MUST use the rules and restrictions defined 396 in [I-D.ietf-mmusic-sdp-mux-attributes] for when associating SDP 397 attributes with bundled "m=" lines. 399 8. SDP Offer/Answer Procedures 401 8.1. General 403 This section describes the SDP Offer/Answer [RFC3264] procedures for: 405 o Negotiating and creating of a BUNDLE group; and 407 o Selecting the BUNDLE addresses (offerer BUNDLE address and 408 answerer BUNDLE address); and 410 o Adding an "m=" line to a BUNDLE group; and 412 o Moving an "m=" line out of a BUNDLE group; and 414 o Disabling an "m=" line within a BUNDLE group. 416 The generic rules and procedures defined in [RFC3264] and [RFC5888] 417 also apply to the BUNDLE extension. For example, if an offer is 418 rejected by the answerer, the previously negotiated SDP parameters 419 and characteristics (including those associated with a BUNDLE group) 420 apply. Hence, if an offerer generates an offer in which the offerer 421 wants to create a BUNDLE group, and the answerer rejects the offer, 422 the BUNDLE group is not created. 424 The procedures in this section are independent of the media type or 425 "m=" line proto value represented by a bundled "m=" line. Section 10 426 defines additional considerations for RTP based media. Section 6 427 defines additional considerations for the usage of the SDP 'bundle- 428 only' attribute. Section 11 defines additional considerations for 429 the usage of Interactive Connectivity Establishment (ICE) 430 [I-D.ietf-ice-rfc5245bis] mechanism. 432 SDP offers and answers can contain multiple BUNDLE groups. The 433 procedures in this section apply independently to a given BUNDLE 434 group. 436 8.2. Mux Category Considerations 438 When an offerer associates a shared address with a bundled "m=" line, 439 the offerer shall associate IDENTICAL and TRANSPORT mux category SDP 440 attributes [I-D.ietf-mmusic-sdp-mux-attributes] with the "m=" line 441 only if the "m=" line is associated with the offerer BUNDLE-tag. 442 Otherwise the offerer MUST NOT associate such SDP attributes with the 443 "m=" line. 445 When an answerer associates a shared address with a bundled "m=" 446 line, the answerer shall associate IDENTICAL and TRANSPORT category 447 SDP attributes with the "m=" line only if the "m=" line is associated 448 with the answerer BUNDLE-tag. Otherwise the answerer MUST NOT 449 associate such SDP attributes with the "m=" line. 451 NOTE: As bundled "m=" lines associated with a shared address will 452 share the same IDENTICAL and TRANSPORT mux category SDP attributes, 453 and attribute values, there is no need to associate such SDP 454 attributes with each "m=" line. 456 8.3. Generating the Initial SDP Offer 458 8.3.1. General 460 When an offerer generates an initial offer, in order to create a 461 BUNDLE group, it MUST: 463 o Assign a unique address to each "m=" line within the offer, 464 following the procedures in [RFC3264], unless the media line is a 465 'bundle-only' "m=" line (see below); and 467 o Add an SDP 'group:BUNDLE' attribute to the offer; and 468 o Place the identification-tag of each bundled "m=" line in the SDP 469 'group:BUNDLE' attribute identification-tag list; and 471 o Indicate which unique address the offerer suggests as the offerer 472 BUNDLE address [Section 8.3.2]. 474 If the offerer wants to request that the answerer accepts a given 475 bundled "m=" line only if the answerer keeps the "m=" line within the 476 BUNDLE group, the offerer MUST: 478 o Associate an SDP 'bundle-only' attribute [Section 8.3.2] with the 479 "m=" line; and 481 o Assign a zero port value to the "m=" line. 483 NOTE: If the offerer assigns a zero port value to an "m=" line, but 484 does not also associate an SDP 'bundle-only' attribute with the "m=" 485 line, it is an indication that the offerer wants to disable the "m=" 486 line [Section 8.6.5]. 488 [Section 17.1] shows an example of an initial offer. 490 8.3.2. Suggesting the offerer BUNDLE address 492 In the offer, the address associated with the "m=" line associated 493 with the offerer BUNDLE-tag indicates the address that the offerer 494 suggests as the offerer BUNDLE address. 496 The "m=" line associated with the offerer BUNDLE-tag MUST NOT contain 497 a zero port value or an SDP 'bundle-only' attribute. 499 8.4. Generating the SDP Answer 501 8.4.1. General 503 When an answerer generates an answer that contains a BUNDLE group, 504 the following general SDP grouping framework restrictions, defined in 505 [RFC5888], also apply to the BUNDLE group: 507 o The answerer MUST NOT include a BUNDLE group in the answer, unless 508 the offerer requested the BUNDLE group to be created in the 509 corresponding offer; and 511 o The answerer MUST NOT include an "m=" line within a BUNDLE group, 512 unless the offerer requested the "m=" line to be within that 513 BUNDLE group in the corresponding offer. 515 If the answer contains a BUNDLE group, the answerer MUST: 517 o Select an Offerer BUNDLE Address [Section 8.4.2]; and 519 o Select an Answerer BUNDLE Address [Section 8.4.3]; 521 The answerer is allowed to select a new Answerer BUNDLE address each 522 time it generates an answer to an offer. 524 If the answerer does not want to keep an "m=" line within a BUNDLE 525 group, it MUST: 527 o Move the "m=" line out of the BUNDLE group [Section 8.4.4]; or 529 o Reject the "m=" line [Section 8.4.5]; 531 If the answerer keeps a bundle-only "m=" line within the BUNDLE 532 group, it follows the procedures (associates the answerer BUNDLE 533 address with the "m=" line etc) for any other "m=" line kept within 534 the BUNDLE group. 536 If the answerer does not want to keep a bundle-only "m=" line within 537 the BUNDLE group, it MUST reject the "m=" line [Section 8.4.5]. 539 The answerer MUST NOT associate an SDP 'bundle-only' attribute with 540 any "m=" line in an answer. 542 NOTE: If a bundled "m=" line in an offer contains a zero port value, 543 but the "m=" line does not contain an SDP 'bundle-only' attribute, it 544 is an indication that the offerer wants to disable the "m=" line 545 [Section 8.6.5]. 547 8.4.2. Answerer Selection of Offerer Bundle Address 549 In an offer, the address (unique or shared) associated with the 550 bundled "m=" line associated with the offerer BUNDLE-tag indicates 551 the address that the offerer suggests as the offerer BUNDLE address 552 [Section 8.3.2]. The answerer MUST check whether that "m=" line 553 fulfils the following criteria: 555 o The answerer will not move the "m=" line out of the BUNDLE group 556 [Section 8.4.4]; and 558 o The answerer will not reject the "m=" line [Section 8.4.5]; and 560 o The "m=" line does not contain a zero port value. 562 If all of the criteria above are fulfilled, the answerer MUST select 563 the address associated with the "m=" line as the offerer BUNDLE 564 address. In the answer, the answerer BUNDLE-tag represents the "m=" 565 line, and the address associated with the "m=" line in the offer 566 becomes the offerer BUNDLE address. 568 If one or more of the criteria are not fulfilled, the answerer MUST 569 select the next identification-tag in the identification-tag list, 570 and perform the same criteria check for the "m=" line associated with 571 that identification-tag. If there are no more identification-tags in 572 the identification-tag list, the answerer MUST NOT create the BUNDLE 573 group. In addition, unless the answerer rejects the whole offer, the 574 answerer MUST apply the answerer procedures for moving an "m=" line 575 out of a BUNDLE group [Section 8.4.4] to each bundled "m=" line in 576 the offer when creating the answer. 578 [Section 17.1] shows an example of an offerer BUNDLE address 579 selection. 581 8.4.3. Answerer Selection of Answerer BUNDLE Address 583 When the answerer selects a BUNDLE address for itself, referred to as 584 the answerer BUNDLE address, it MUST associate that address with each 585 bundled "m=" line within the created BUNDLE group in the answer. 587 The answerer MUST NOT associate the answerer BUNDLE address with an 588 "m=" line that is not within the BUNDLE group, or to an "m=" line 589 that is within another BUNDLE group. 591 [Section 17.1] shows an example of an answerer BUNDLE address 592 selection. 594 8.4.4. Moving A Media Description Out Of A BUNDLE Group 596 When an answerer wants to move an "m=" line out of a BUNDLE group, it 597 MUST first check the following criteria: 599 o In the corresponding offer, the "m=" line is associated with a 600 shared address (e.g. a previously selected offerer BUNDLE 601 address); or 603 o In the corresponding offer, if an SDP 'bundle-only' attribute is 604 associated with the "m=" line, and if the "m=" line contains a 605 zero port value. 607 If either criteria above is fulfilled, the answerer MUST reject the 608 "m=" line [Section 8.4.5]. 610 Otherwise, if in the corresponding offer the "m=" line is associated 611 with a unique address, the answerer MUST associate a unique address 612 with the "m=" line in the answer (the answerer does not reject the 613 "m=" line). 615 In addition, in either case above, the answerer MUST NOT place the 616 identification-tag, associated with the moved "m=" line, in the SDP 617 'group' attribute identification-tag list associated with the BUNDLE 618 group. 620 8.4.5. Rejecting A Media Description In A BUNDLE Group 622 When an answerer rejects an "m=" line, it MUST associate an address 623 with a zero port value with the "m=" line in the answer, according to 624 the procedures in [RFC4566]. 626 In addition, the answerer MUST NOT place the identification-tag, 627 associated with the rejected "m=" line, in the SDP 'group' attribute 628 identification-tag list associated with the BUNDLE group. 630 8.5. Offerer Processing of the SDP Answer 632 When an offerer receives an answer, if the answer contains a BUNDLE 633 group, the offerer MUST check that any bundled "m=" line in the 634 answer was indicated as bundled in the corresponding offer. If there 635 is no mismatch, the offerer MUST use the offerer BUNDLE address, 636 selected by the answerer [Section 8.4.2], as the address for each 637 bundled "m=" line. 639 NOTE: As the answerer might reject one or more bundled "m=" lines, or 640 move a bundled "m=" line out of a BUNDLE group, each bundled "m=" 641 line in the offer might not be indicated as bundled in the answer. 643 If the answer does not contain a BUNDLE group, the offerer MUST 644 process the answer as a normal answer. 646 8.6. Modifying the Session 648 8.6.1. General 650 When an offerer generates a subsequent offer, it MUST associate the 651 previously selected offerer BUNDLE address [Section 8.4.2] with each 652 bundled "m=" line (including any bundle-only "m=" line), except if: 654 o The offerer suggests a new offerer BUNDLE address [Section 8.6.2]; 655 or 657 o The offerer wants to add a bundled "m=" line to the BUNDLE group 658 [Section 8.6.3]; or 660 o The offerer wants to move a bundled "m=" line out of the BUNDLE 661 group [Section 8.6.4]; or 663 o The offerer wants to disable the bundled "m=" line 664 [Section 8.6.5]. 666 In addition, the offerer MUST select an offerer BUNDLE-tag 667 [Section 8.3.2] associated with the previously selected offerer 668 BUNDLE address, unless the offerer suggests a new offerer BUNDLE 669 address. 671 8.6.2. Suggesting a new offerer BUNDLE address 673 When an offerer generates an offer, in which it suggests a new 674 offerer BUNDLE address [Section 8.3.2], the offerer MUST: 676 o Assign the address (shared address) to each "m=" line within the 677 BUNDLE group; or 679 o Assign the address (unique address) to one bundled "m=" line. 681 In addition, the offerer MUST indicate that the address is the new 682 suggested offerer BUNDLE address [Section 8.3.2]. 684 NOTE: Unless the offerer associates the new suggested offerer BUNDLE 685 address with each bundled "m=" line, it can associate unique 686 addresses with any number of bundled "m=" lines (and the previously 687 selected offerer BUNDLE address to any remaining bundled "m=" line) 688 if it wants to suggest multiple alternatives for the new offerer 689 BUNDLE address. 691 8.6.3. Adding a media description to a BUNDLE group 693 When an offerer generates an offer, in which it wants to add a 694 bundled "m=" line to a BUNDLE group, the offerer MUST: 696 o Assign a unique address to the added "m=" line; or 698 o Assign the previously selected offerer BUNDLE address to the added 699 "m=" line; or 701 o If the offerer associates a new (shared address) suggested offerer 702 BUNDLE address with each bundled "m=" line [Section 8.6.2], also 703 associate that address with the added "m=" line. 705 In addition, the offerer MUST extend the SDP 'group:BUNDLE' attribute 706 identification-tag list with the BUNDLE group [Section 8.3.2] by 707 adding the identification-tag associated with the added "m=" line to 708 the list. 710 NOTE: Assigning a unique address to the "m=" line allows the answerer 711 to move the "m=" line out of the BUNDLE group [Section 8.4.4], 712 without having to reject the "m=" line. 714 If the offerer associates a unique address with the added "m=" line, 715 and if the offerer suggests that address as the new offerer BUNDLE 716 address [Section 8.6.2], the offerer BUNDLE-tag MUST represent the 717 added "m=" line [Section 8.3.2]. 719 If the offerer associates a new suggested offerer BUNDLE address with 720 each bundled "m=" line [Section 8.6.2], including the added "m=" 721 line, the offerer BUNDLE-tag MAY represent the added "m=" line 722 [Section 8.3.2]. 724 [Section 17.3] shows an example where an offerer sends an offer in 725 order to add a bundled "m=" line to a BUNDLE group. 727 8.6.4. Moving A Media Description Out Of A BUNDLE Group 729 When an offerer generates an offer, in which it wants to move a 730 bundled "m=" line out of a BUNDLE group it was added to in a previous 731 offer/answer transaction, the offerer: 733 o MUST associate a unique address with the "m=" line; and 735 o MUST NOT place the identification-tag associated with the "m=" 736 line in the SDP 'group:BUNDLE' attribute identification-tag list 737 associated with the BUNDLE group. 739 NOTE: If the removed "m=" line is associated with the previously 740 selected BUNDLE-tag, the offerer needs to suggest a new BUNDLE-tag 741 [Section 8.3.2]. 743 NOTE: If an "m=" line, when being moved out of a BUNDLE group, is 744 added to another BUNDLE group, the offerer applies the procedures in 745 [Section 8.6.3] to the "m=" line. 747 [Section 17.4] shows an example of an offer for moving an "m=" line 748 out of a BUNDLE group. 750 8.6.5. Disabling A Media Description In A BUNDLE Group 752 When an offerer generates an offer, in which it wants to disable a 753 bundled "m=" line (added to the BUNDLE group in a previous offer/ 754 answer transaction), the offerer: 756 o MUST associate an address with a zero port value with the "m=" 757 line, following the procedures in [RFC4566]; and 759 o MUST NOT place the identification-tag associated with the "m=" 760 line in the SDP 'group:BUNDLE' attribute identification-tag list 761 associated with the BUNDLE group. 763 [Section 17.5] shows an example of an offer for disabling an "m=" 764 line within a BUNDLE group. 766 9. Protocol Identification 768 9.1. General 770 Each "m=" line within a BUNDLE group MUST use the same transport- 771 layer protocol. If bundled "m=" lines use different protocols on top 772 of the transport-layer protocol, there MUST exist a publicly 773 available specification which describes a mechanism, for this 774 particular protocol combination, how to associate received data with 775 the correct protocol. 777 In addition, if received data can be associated with more than one 778 bundled "m=" line, there MUST exist a publicly available 779 specification which describes a mechanism for associating the 780 received data with the correct "m=" line. 782 This document describes a mechanism to identify the protocol of 783 received data among the STUN, DTLS and SRTP protocols (in any 784 combination), when UDP is used as transport-layer protocol, but does 785 not describe how to identify different protocols transported on DTLS. 786 While the mechanism is generally applicable to other protocols and 787 transport-layers protocols, any such use requires further 788 specification around how to multiplex multiple protocols on a given 789 transport-layer protocols, and how to associate received data with 790 the correct protocols. 792 9.2. STUN, DTLS, SRTP 794 Section 5.1.2 of [RFC5764] describes a mechanism to identify the 795 protocol of a received packet among the STUN, Datagram Transport 796 Layer Security (DTLS) and SRTP protocols (in any combination). If an 797 offer or answer includes bundled "m=" lines that represent these 798 protocols, the offerer or answerer MUST support the mechanism 799 described in [RFC5764], and no explicit negotiation is required in 800 order to indicate support and usage of the mechanism. 802 [RFC5764] does not describe how to identify different protocols 803 transported on DTLS, only how to identify the DTLS protocol itself. 805 If multiple protocols are transported on DTLS, there MUST exist a 806 specification describing a mechanism for identifying each individual 807 protocol. In addition, if a received DTLS packet can be associated 808 with more than one "m=" line, there MUST exist a specification which 809 describes a mechanism for associating the received DTLS packet with 810 the correct "m=" line. 812 [Section 10.2] describes how to associate a received (S)RTP packet 813 with the correct "m=" line. 815 10. RTP Considerations 817 10.1. Single RTP Session 819 10.1.1. General 821 All RTP-based media within a single BUNDLE group belong to a single 822 RTP session [RFC3550]. Disjoint BUNDLE groups will form multiple RTP 823 sessions, one per BUNDLE group. 825 Since a single RTP session is used for each bundle group, all "m=" 826 lines representing RTP-based media in a bundle group will share a 827 single SSRC numbering space [RFC3550]. 829 The following rules and restrictions apply for a single RTP session: 831 o A specific payload type value can be used in multiple bundled "m=" 832 lines if each codec associated with the payload type number shares 833 an identical codec configuration [Section 10.1.2]. 835 o The proto value in each bundled RTP-based "m=" line MUST be 836 identical (e.g. RTP/AVPF). 838 o The RTP MID header extension MUST be enabled, by associating an 839 SDP 'extmap' attribute [RFC5285], with a 'urn:ietf:params:rtp- 840 hdrext:sdes:mid' URI value, with each bundled RTP-based "m=" line 841 in every offer and answer. 843 o A given SSRC MUST NOT transmit RTP packets using payload types 844 that originate from different bundled "m=" lines. 846 NOTE: The last bullet above is to avoid sending multiple media types 847 from the same SSRC. If transmission of multiple media types are done 848 with time overlap, RTP and RTCP fail to function. Even if done in 849 proper sequence this causes RTP Timestamp rate switching issues 850 [RFC7160]. However, once an SSRC has left the RTP session (by 851 sending an RTCP BYE packet), that SSRC value can later be reused by 852 another source(possibly associated with a different bundled "m=" 853 line. 855 10.1.2. Payload Type (PT) Value Reuse 857 Multiple bundled "m=" lines might represent RTP based media. As all 858 RTP based media specified by a BUNDLE group belong to the same RTP 859 session, in order for a given payload type value to be used inside 860 more than one bundled "m=" line, all codecs associated with the 861 payload type number MUST share an identical codec configuration. 862 This means that the codecs MUST share the same media type, encoding 863 name, clock rate and any parameter that can affect the codec 864 configuration and packetization. 865 [I-D.ietf-mmusic-sdp-mux-attributes] lists SDP attributes, whose 866 attribute values must be identical for all codecs that use the same 867 payload type value. 869 10.2. Associating RTP/RTCP Packets With Correct SDP Media Description 871 There are multiple mechanisms that can be used by an endpoint in 872 order to associate received RTP/RTCP packets with a bundled "m=" 873 line. Such mechanisms include using the payload type value carried 874 inside the RTP packets, the SSRC values carried inside the RTP 875 packets, and other "m=" line specific information carried inside the 876 RTP packets. 878 As all RTP/RTCP packets associated with a BUNDLE group are received 879 (and sent) using single address:port combinations, the local 880 address:port combination cannot be used to associate received RTP 881 packets with the correct "m=" line. 883 As described in [Section 10.1.2], the same payload type value might 884 be used inside RTP packets described by multiple "m=" lines. In such 885 cases, the payload type value cannot be used to associate received 886 RTP packets with the correct "m=" line. 888 An offerer and answerer can inform each other which SSRC values they 889 will use for RTP and RTCP by using the SDP 'ssrc' attribute 890 [RFC5576]. To allow for proper association with this mechanism, the 891 'ssrc' attribute needs to be associated with each "m=" line that 892 shares a payload type with any other "m=" line in the same bundle. 893 As the SSRC values will be carried inside the RTP/RTCP packets, the 894 offerer and answerer can then use that information to associate 895 received RTP packets with the correct "m=" line. However, an offerer 896 will not know which SSRC values the answerer will use until it has 897 received the answer providing that information. Due to this, before 898 the offerer has received the answer, the offerer will not be able to 899 associate received RTP/RTCP packets with the correct "m=" line using 900 the SSRC values. 902 In order for an offerer and answerer to always be able to associate 903 received RTP and RTCP packets with the correct "m=" line, an offerer 904 and answerer using the BUNDLE extension MUST support the mechanism 905 defined in Section 14, where the remote endpoint inserts the 906 identification-tag associated with an "m=" line in RTP and RTCP 907 packets associated with that "m=" line. 909 10.3. RTP/RTCP Multiplexing 911 10.3.1. General 913 Within a BUNDLE group, the offerer and answerer MUST enable RTP/RTCP 914 multiplexing [RFC5761] for the RTP-based media specified by the 915 BUNDLE group. 917 When RTP/RTCP multiplexing is enabled, the same address:port 918 combination will be used for sending all RTP packets and the RTCP 919 packets associated with the BUNDLE group. Each endpoint will send 920 the packets towards the BUNDLE address of the other endpoint. The 921 same address:port combination MAY be used for receiving RTP packets 922 and RTCP packets. 924 10.3.2. SDP Offer/Answer Procedures 926 10.3.2.1. General 928 This section describes how an offerer and answerer use the SDP 'rtcp- 929 mux' attribute [RFC5761] to negotiate usage of RTP/RTCP multiplexing 930 for RTP-based media specified by a BUNDLE group. 932 The procedures in this section only apply to RTP-based "m=" lines. 934 10.3.2.2. Generating the Initial SDP Offer 936 When an offerer generates an initial offer, the offerer MUST 937 associate an SDP 'rtcp-mux' attribute [RFC5761] with each bundled 938 RTP-based "m=" line (including any bundle-only "m=" line) in the 939 offer. 941 If an offerer wants to indicate exclusive support of RTP/RTCP 942 multiplexing [I-D.ietf-mmusic-mux-exclusive] for one or more "m=" 943 lines within the BUNDLE group, the offerer MUST associate an SDP 944 'rtcp-mux-exclusive' attribute with those "m=" lines. 946 NOTE: The offerer might also associate an SDP 'rtcp' attribute 947 [RFC3605] with a bundled "m=" line, excluding a bundle-only "m=" 948 line, in order to provide a fallback port for RTCP. However, the 949 fallback port will only be used in case the answerer does not include 950 the "m=" line in the BUNDLE group in the associated answer. 952 In the initial offer, the address:port combination for RTCP MUST be 953 unique in each bundled RTP-based "m=" line (excluding a 'bundle-only' 954 "m=" line), similar to RTP. 956 10.3.2.3. Generating the SDP Answer 958 When an answerer generates an answer, if the answerer accepts an RTP- 959 based "m=" line within a BUNDLE group, the answerer MUST enable usage 960 of RTP/RTCP multiplexing. The answerer MUST associate an SDP "rtcp- 961 mux" attribute with the "m=" line in the answer. In addition, if the 962 "m=" line in the corresponding offer contained an SDP "rtcp-mux- 963 exclusive" attribute, the answerer MUST associate an SDP "rtcp-mux- 964 exclusive" attribute with the "m=" line in the answer. 966 If an RTP-based "m=" line in the corresponding offer did not contain 967 an SDP "rtcp-mux" attribute, the answerer MUST NOT accept the "m=" 968 line within a BUNDLE group in the answer. 970 If an RTP-based "m=" line in the corresponding offer contained an SDP 971 "rtcp-mux-exclusive" attribute, and if the answerer moves the "m=" 972 line out of the BUNDLE group in the answer Section 8.4.4, the 973 answerer MUST still either enable RTP/RTCP multiplexing, or reject 974 the "m=" line Section 8.4.5. 976 When the answerer accepts the usage of RTP/RTCP multiplexing within 977 the BUNDLE group, it MUST associate an SDP 'rtcp-mux' attribute with 978 each bundled RTP-based "m=" line in the answer. In addition, if the 979 "m=" line in the corresponding offer contained an SDP 'rtcp-mux- 980 exclusive' attribute, the answerer MUST associated an SDP 'rtcp-mux- 981 exclusive' attribute with the corresponding "m=" line in the answer, 982 as described in. 984 The answerer MUST NOT associate an SDP 'rtcp' attribute with any 985 bundled "m=" line in the answer. The answerer will use the port 986 value of the selected offerer BUNDLE address for sending RTP and RTCP 987 packets associated with each RTP-based bundled "m=" line towards the 988 offerer. 990 If the usage of RTP/RTCP multiplexing within a BUNDLE group has been 991 negotiated in a previous offer/answer transaction, the answerer MUST 992 associate an SDP 'rtcp-mux' attribute with each bundled RTP-based 993 "m=" line in the answer. 995 10.3.2.4. Offerer Processing of the SDP Answer 997 When an offerer receives an answer, if the answerer has accepted the 998 usage of RTP/RTCP multiplexing (see Section 10.3.2.3), the answerer 999 follows the procedures for RTP/RTCP multiplexing defined in 1000 [RFC5761]. The offerer will use the port value associated with the 1001 answerer BUNDLE address for sending RTP and RTCP packets associated 1002 with each RTP-based bundled "m=" line towards the answerer. 1004 NOTE: It is considered a protocol error if the answerer has not 1005 accepted the usage of RTP/RTCP multiplexing for RTP-based "m=" lines 1006 that the answerer included in the BUNDLE group. 1008 10.3.2.5. Modifying the Session 1010 When an offerer generates a subsequent offer, it MUST associate an 1011 SDP 'rtcp-mux' attribute with each RTP-based bundled "m=" line 1012 (including any bundled "m=" line that the offerer wants to add to the 1013 BUNDLE group), unless the offerer wants to disable or remove the "m=" 1014 line from the BUNDLE group. 1016 11. ICE Considerations 1018 11.1. General 1020 This section describes how to use the BUNDLE grouping extension 1021 together with the Interactive Connectivity Establishment (ICE) 1022 mechanism [I-D.ietf-ice-rfc5245bis]. 1024 The generic procedures for negotiating usage of ICE using SDP, 1025 defined in [I-D.ietf-mmusic-ice-sip-sdp], also apply to usage of ICE 1026 with BUNDLE, with the following exceptions: 1028 o When BUNDLE addresses for a BUNDLE group have been selected for 1029 both endpoints, ICE connectivity checks and keep-alives only need 1030 to be performed for the whole BUNDLE group, instead of per bundled 1031 "m=" line. 1033 o Among bundled "m=" lines with which the offerer has associated a 1034 shared address, the offerer only associates ICE-related media- 1035 level SDP attributes with the "m=" line associated with the 1036 offerer BUNDLE-tag. 1038 o Among bundled "m=" lines with which the answerer has associated a 1039 shared address, the answerer only associates ICE-related media- 1040 level SDP attributes with the "m=" line associated with the 1041 answerer BUNDLE-tag. 1043 Support and usage of ICE mechanism together with the BUNDLE extension 1044 is OPTIONAL. 1046 11.2. SDP Offer/Answer Procedures 1048 11.2.1. General 1050 When an offerer associates a unique address with a bundled "m=" line 1051 (excluding any bundle-only "m=" line), the offerer MUST associate SDP 1052 'candidate' attributes (and other applicable ICE-related media-level 1053 SDP attributes), containing unique ICE properties (candidates etc), 1054 with the "m=" line, according to the procedures in 1055 [I-D.ietf-mmusic-ice-sip-sdp]. 1057 When an offerer associates a shared address with a bundled "m=" line, 1058 if the "m=" line is associated with the offerer BUNDLE-tag, the 1059 offerer MUST associate SDP 'candidate' attributes (and other 1060 applicable ICE-related media-level SDP attributes), containing shared 1061 ICE properties, with the "m=" line. If the "m=" line is not 1062 associated with the offerer BUNDLE-tag, the offerer MUST NOT 1063 associate ICE-related SDP attributes with the "m=" line. 1065 When an answerer associates a shared address with a bundled "m=" 1066 line, if the "m=" line is associated with the answerer BUNDLE-tag, 1067 the answerer MUST associate SDP 'candidate' attributes (and other 1068 applicable ICE-related media-level SDP attributes), containing shared 1069 ICE properties, with the "m=" line. If the "m=" line is not 1070 associated with the answerer BUNDLE-tag, the answerer MUST NOT 1071 associate ICE-related SDP attributes with the "m=" line. 1073 NOTE: As most ICE-related media-level SDP attributes belong to the 1074 TRANSPORT mux category [I-D.ietf-mmusic-sdp-mux-attributes], the 1075 offerer and answerer follow the rules in Section 8.2. However, in 1076 the case of ICE-related media-level attributes, the rules apply to 1077 all attributes (see note below), even if they belong to a different 1078 mux category. 1080 NOTE: The following ICE-related media-level SDP attributes are 1081 defined in [I-D.ietf-mmusic-ice-sip-sdp]: 'candidiate', 'remote- 1082 candidates', 'ice-mismatch', 'ice-ufrag', 'ice-pwd', and 'ice- 1083 pacing'. 1085 11.2.2. Generating the Initial SDP Offer 1087 When an offerer generates an initial offer, the offerer MUST 1088 associate ICE-related media-level SDP attributes with each bundled 1089 "m=" line, according to [Section 11.2.1]. 1091 11.2.3. Generating the SDP Answer 1093 When an answerer generates an answer that contains a BUNDLE group, 1094 the answerer MUST associated ICE-related SDP attributes with the "m=" 1095 line associated with the answerer BUNDLE-tag, according to 1096 [Section 11.2.1]. 1098 11.2.4. Offerer Processing of the SDP Answer 1100 When an offerer receives an answer, if the answerer supports and uses 1101 the ICE mechanism and the BUNDLE extension, the offerer MUST 1102 associate the ICE properties associated with the offerer BUNDLE 1103 address, selected by the answerer [Section 8.4.2], with each bundled 1104 "m=" line. 1106 11.2.5. Modifying the Session 1108 When an offerer generates a subsequent offer, it MUST associated 1109 unique or shared ICE properties to one or more bundled "m=" lines, 1110 according to [Section 11.2.1]. 1112 12. DTLS Considerations 1114 One or more media streams within a BUNDLE group might use the 1115 Datagram Transport Layer Security (DTLS) protocol [RFC6347] in order 1116 to encrypt the data, or to negotiate encryption keys if another 1117 encryption mechanism is used to encrypt media. 1119 When DTLS is used within a BUNDLE group, the following rules apply: 1121 o There can only be one DTLS association [RFC6347] associated with 1122 the BUNDLE group; and 1124 o Each usage of the DTLS association within the BUNDLE group MUST 1125 use the same mechanism for determining which endpoints (the 1126 offerer or answerer) becomes DTLS client and DTLS server; and 1128 o Each usage of the DTLS association within the Bundle group MUST 1129 use the same mechanism for determining whether an offer or answer 1130 will trigger the establishment of a new DTLS association, or 1131 whether an existing DTLS association will be used; and 1133 o If the DTLS client supports DTLS-SRTP [RFC5764] it MUST include 1134 the 'use_srtp' extension [RFC5764] in the DTLS ClientHello message 1135 [RFC5764], The client MUST include the extension even if the usage 1136 of DTLS-SRTP is not negotiated as part of the multimedia session 1137 (e.g. SIP session [RFC3261]. 1139 NOTE: The inclusion of the 'use_srtp' extension during the initial 1140 DTLS handshake ensures that a DTLS renegotiation will not be required 1141 in order to include the extension, in case DTLS-SRTP encrypted media 1142 is added to the BUNDLE group later during the multimedia session. 1144 13. Update to RFC 3264 1146 13.1. General 1148 This section replaces the text of the following sections of RFC 3264: 1150 o Section 5.1 (Unicast Streams). 1152 o Section 8.2 (Removing a Media Stream). 1154 o Section 8.4 (Putting a Unicast Media Stream on Hold). 1156 13.2. Original text of section 5.1 (2nd paragraph) of RFC 3264 1158 For recvonly and sendrecv streams, the port number and address in the 1159 offer indicate where the offerer would like to receive the media 1160 stream. For sendonly RTP streams, the address and port number 1161 indirectly indicate where the offerer wants to receive RTCP reports. 1162 Unless there is an explicit indication otherwise, reports are sent to 1163 the port number one higher than the number indicated. The IP address 1164 and port present in the offer indicate nothing about the source IP 1165 address and source port of RTP and RTCP packets that will be sent by 1166 the offerer. A port number of zero in the offer indicates that the 1167 stream is offered but MUST NOT be used. This has no useful semantics 1168 in an initial offer, but is allowed for reasons of completeness, 1169 since the answer can contain a zero port indicating a rejected stream 1170 (Section 6). Furthermore, existing streams can be terminated by 1171 setting the port to zero (Section 8). In general, a port number of 1172 zero indicates that the media stream is not wanted. 1174 13.3. New text replacing section 5.1 (2nd paragraph) of RFC 3264 1176 For recvonly and sendrecv streams, the port number and address in the 1177 offer indicate where the offerer would like to receive the media 1178 stream. For sendonly RTP streams, the address and port number 1179 indirectly indicate where the offerer wants to receive RTCP reports. 1180 Unless there is an explicit indication otherwise, reports are sent to 1181 the port number one higher than the number indicated. The IP address 1182 and port present in the offer indicate nothing about the source IP 1183 address and source port of RTP and RTCP packets that will be sent by 1184 the offerer. A port number of zero in the offer by default indicates 1185 that the stream is offered but MUST NOT be used, but an extension 1186 mechanism might specify different semantics for the usage of a zero 1187 port value. Furthermore, existing streams can be terminated by 1188 setting the port to zero (Section 8). In general, a port number of 1189 zero by default indicates that the media stream is not wanted. 1191 13.4. Original text of section 8.2 (2nd paragraph) of RFC 3264 1193 A stream that is offered with a port of zero MUST be marked with port 1194 zero in the answer. Like the offer, the answer MAY omit all 1195 attributes present previously, and MAY list just a single media 1196 format from amongst those in the offer. 1198 13.5. New text replacing section 8.2 (2nd paragraph) of RFC 3264 1200 A stream that is offered with a port of zero MUST by default be 1201 marked with port zero in the answer, unless an extension mechanism, 1202 which specifies semantics for the usage of a non-zero port value, is 1203 used. If the stream is marked with port zero in the answer, the 1204 answer MAY omit all attributes present previously, and MAY list just 1205 a single media format from amongst those in the offer." 1207 13.6. Original text of section 8.4 (6th paragraph) of RFC 3264 1209 RFC 2543 [10] specified that placing a user on hold was accomplished 1210 by setting the connection address to 0.0.0.0. Its usage for putting 1211 a call on hold is no longer recommended, since it doesn't allow for 1212 RTCP to be used with held streams, doesn't work with IPv6, and breaks 1213 with connection oriented media. However, it can be useful in an 1214 initial offer when the offerer knows it wants to use a particular set 1215 of media streams and formats, but doesn't know the addresses and 1216 ports at the time of the offer. Of course, when used, the port 1217 number MUST NOT be zero, which would specify that the stream has been 1218 disabled. An agent MUST be capable of receiving SDP with a 1219 connection address of 0.0.0.0, in which case it means that neither 1220 RTP nor RTCP should be sent to the peer. 1222 13.7. New text replacing section 8.4 (6th paragraph) of RFC 3264 1224 RFC 2543 [10] specified that placing a user on hold was accomplished 1225 by setting the connection address to 0.0.0.0. Its usage for putting 1226 a call on hold is no longer recommended, since it doesn't allow for 1227 RTCP to be used with held streams, doesn't work with IPv6, and breaks 1228 with connection oriented media. However, it can be useful in an 1229 initial offer when the offerer knows it wants to use a particular set 1230 of media streams and formats, but doesn't know the addresses and 1231 ports at the time of the offer. Of course, when used, the port 1232 number MUST NOT be zero, if it would specify that the stream has been 1233 disabled. However, an extension mechanism might specify different 1234 semantics of the zero port number usage. An agent MUST be capable of 1235 receiving SDP with a connection address of 0.0.0.0, in which case it 1236 means that neither RTP nor RTCP should be sent to the peer. 1238 14. RTP/RTCP extensions for identification-tag transport 1240 14.1. General 1242 SDP Offerers and Answerers [RFC3264] can associate identification- 1243 tags with "m=" lines within SDP Offers and Answers, using the 1244 procedures in [RFC5888]. Each identification-tag uniquely represents 1245 an "m=" line. 1247 This section defines a new RTCP SDES item [RFC3550], 'MID', which is 1248 used to carry identification-tags within RTCP SDES packets. This 1249 section also defines a new RTP header extension [RFC5285], which is 1250 used to carry identification-tags in RTP packets. 1252 The SDES item and RTP header extension make it possible for a 1253 receiver to associate received RTCP- and RTP packets with a specific 1254 "m=" line, with which the receiver has associated an identification- 1255 tag, even if those "m=" lines are part of the same RTP session. A 1256 media recipient informs the media sender about the identification-tag 1257 associated with an "m=" line through the use of an 'mid' attribute 1258 [RFC5888]. The media sender then inserts the identification-tag in 1259 RTCP and RTP packets sent to the media recipient. 1261 NOTE: This text above defines how identification-tags are carried in 1262 SDP Offers and Answers. The usage of other signalling protocols for 1263 carrying identification-tags is not prevented, but the usage of such 1264 protocols is outside the scope of this document. 1266 [RFC3550] defines general procedures regarding the RTCP transmission 1267 interval. The RTCP MID SDES item SHOULD be sent in the first few 1268 RTCP packets sent on joining the session, and SHOULD be sent 1269 regularly thereafter. The exact number of RTCP packets in which this 1270 SDES item is sent is intentionally not specified here, as it will 1271 depend on the expected packet loss rate, the RTCP reporting interval, 1272 and the allowable overhead. 1274 The RTP MID header extension SHOULD be included in some RTP packets 1275 at the start of the session and whenever the SSRC changes. It might 1276 also be useful to include the header extension in RTP packets that 1277 comprise random access points in the media (e.g., with video 1278 I-frames). The exact number of RTP packets in which this header 1279 extension is sent is intentionally not specified here, as it will 1280 depend on expected packet loss rate and loss patterns, the overhead 1281 the application can tolerate, and the importance of immediate receipt 1282 of the identification-tag. 1284 For robustness purpose, endpoints need to be prepared for situations 1285 where the reception of the identification-tag is delayed, and SHOULD 1286 NOT terminate sessions in such cases, as the identification-tag is 1287 likely to arrive soon. 1289 14.2. RTCP MID SDES Item 1291 0 1 2 3 1292 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 1293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1294 | MID=TBD | length | identification-tag ... 1295 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1297 The identification-tag payload is UTF-8 encoded, as in SDP. 1299 The identification-tag is not zero terminated. 1301 [RFC EDITOR NOTE: Please replace TBD with the assigned SDES 1302 identifier value.] 1304 14.3. RTP MID Header Extension 1306 The payload, containing the identification-tag, of the RTP MID header 1307 extension element can be encoded using either the one-byte or two- 1308 byte header [RFC5285]. The identification-tag payload is UTF-8 1309 encoded, as in SDP. 1311 The identification-tag is not zero terminated. Note, that set of 1312 header extensions included in the packet needs to be padded to the 1313 next 32-bit boundary using zero bytes [RFC5285]. 1315 As the identification-tag is included in either an RTCP SDES item or 1316 an RTP header extension, or both, there should be some consideration 1317 about the packet expansion caused by the identification-tag. To 1318 avoid Maximum Transmission Unit (MTU) issues for the RTP packets, the 1319 header extension's size needs to be taken into account when encoding 1320 the media. 1322 It is recommended that the identification-tag is kept short. Due to 1323 the properties of the RTP header extension mechanism, when using the 1324 one-byte header, a tag that is 1-3 bytes will result in that a 1325 minimal number of 32-bit words are used for the RTP header extension, 1326 in case no other header extensions are included at the same time. 1327 Note, do take into account that some single characters when UTF-8 1328 encoded will result in multiple octets. 1330 15. IANA Considerations 1332 15.1. New SDES item 1334 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 1335 document.] 1337 [RFC EDITOR NOTE: Please replace TBD with the assigned SDES 1338 identifier value.] 1340 This document adds the MID SDES item to the IANA "RTCP SDES item 1341 types" registry as follows: 1343 Value: TBD 1344 Abbrev.: MID 1345 Name: Media Identification 1346 Reference: RFCXXXX 1348 15.2. New RTP Header Extension URI 1350 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 1351 document.] 1353 This document defines a new extension URI in the RTP Compact Header 1354 Extensions subregistry of the Real-Time Transport Protocol (RTP) 1355 Parameters registry, according to the following data: 1357 Extension URI: urn:ietf:params:rtp-hdrext:sdes:mid 1358 Description: Media identification 1359 Contact: christer.holmberg@ericsson.com 1360 Reference: RFCXXXX 1362 15.3. New SDP Attribute 1364 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 1365 document.] 1367 This document defines a new SDP media-level attribute, 'bundle-only', 1368 according to the following data: 1370 Attribute name: bundle-only 1371 Type of attribute: media 1372 Subject to charset: No 1373 Purpose: Request a media description to be accepted 1374 in the answer only if kept within a BUNDLE 1375 group by the answerer. 1376 Appropriate values: N/A 1377 Contact name: Christer Holmberg 1378 Contact e-mail: christer.holmberg@ericsson.com 1379 Reference: RFCXXXX 1381 15.4. New SDP Group Semantics 1383 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 1384 document.] 1386 This document registers the following semantics with IANA in the 1387 "Semantics for the "group" SDP Attribute" subregistry (under the 1388 "Session Description Protocol (SDP) Parameters" registry: 1390 Semantics Token Reference 1391 ------------------------------------- ------ --------- 1392 Media bundling BUNDLE [RFCXXXX] 1394 16. Security Considerations 1396 The security considerations defined in [RFC3264] and [RFC5888] apply 1397 to the BUNDLE extension. Bundle does not change which information 1398 flows over the network but only changes which addresses and ports 1399 that information is flowing on and thus has very little impact on the 1400 security of the RTP sessions. 1402 When the BUNDLE extension is used, a single set of security 1403 credentials might be used for all media streams specified by a BUNDLE 1404 group. 1406 When the BUNDLE extension is used, the number of SSRC values within a 1407 single RTP session increases, which increases the risk of SSRC 1408 collision. [RFC4568] describes how SSRC collision may weaken SRTP 1409 and SRTCP encryption in certain situations. 1411 17. Examples 1413 17.1. Example: Bundle Address Selection 1415 The example below shows: 1417 o An offer, in which the offerer associates a unique address with 1418 each bundled "m=" line within the BUNDLE group. 1420 o An answer, in which the answerer selects the offerer BUNDLE 1421 address, and in which selects its own BUNDLE address (the answerer 1422 BUNDLE address) and associates it with each bundled "m=" line 1423 within the BUNDLE group. 1425 SDP Offer (1) 1427 v=0 1428 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 1429 s= 1430 c=IN IP4 atlanta.example.com 1431 t=0 0 1432 a=group:BUNDLE foo bar 1433 m=audio 10000 RTP/AVP 0 8 97 1434 b=AS:200 1435 a=mid:foo 1436 a=rtpmap:0 PCMU/8000 1437 a=rtpmap:8 PCMA/8000 1438 a=rtpmap:97 iLBC/8000 1439 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1440 m=video 10002 RTP/AVP 31 32 1441 b=AS:1000 1442 a=mid:bar 1443 a=rtpmap:31 H261/90000 1444 a=rtpmap:32 MPV/90000 1445 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1447 SDP Answer (2) 1449 v=0 1450 o=bob 2808844564 2808844564 IN IP4 biloxi.example.com 1451 s= 1452 c=IN IP4 biloxi.example.com 1453 t=0 0 1454 a=group:BUNDLE foo bar 1455 m=audio 20000 RTP/AVP 0 1456 b=AS:200 1457 a=mid:foo 1458 a=rtpmap:0 PCMU/8000 1459 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1460 m=video 20000 RTP/AVP 32 1461 b=AS:1000 1462 a=mid:bar 1463 a=rtpmap:32 MPV/90000 1464 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1466 17.2. Example: BUNDLE Extension Rejected 1468 The example below shows: 1470 o An offer, in which the offerer associates a unique address with 1471 each bundled "m=" line within the BUNDLE group. 1473 o An answer, in which the answerer rejects the offered BUNDLE group, 1474 and associates a unique address with each "m=" line (following 1475 normal RFC 3264 procedures). 1477 SDP Offer (1) 1479 v=0 1480 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 1481 s= 1482 c=IN IP4 atlanta.example.com 1483 t=0 0 1484 a=group:BUNDLE foo bar 1485 m=audio 10000 RTP/AVP 0 8 97 1486 b=AS:200 1487 a=mid:foo 1488 a=rtpmap:0 PCMU/8000 1489 a=rtpmap:8 PCMA/8000 1490 a=rtpmap:97 iLBC/8000 1491 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1492 m=video 10002 RTP/AVP 31 32 1493 b=AS:1000 1494 a=mid:bar 1495 a=rtpmap:31 H261/90000 1496 a=rtpmap:32 MPV/90000 1497 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1499 SDP Answer (2) 1501 v=0 1502 o=bob 2808844564 2808844564 IN IP4 biloxi.example.com 1503 s= 1504 c=IN IP4 biloxi.example.com 1505 t=0 0 1506 m=audio 20000 RTP/AVP 0 1507 b=AS:200 1508 a=rtpmap:0 PCMU/8000 1509 m=video 30000 RTP/AVP 32 1510 b=AS:1000 1511 a=rtpmap:32 MPV/90000 1513 17.3. Example: Offerer Adds A Media Description To A BUNDLE Group 1515 The example below shows: 1517 o A subsequent offer (the BUNDLE group has been created as part of a 1518 previous offer/answer transaction), in which the offerer adds a 1519 new "m=" line, represented by the "zen" identification-tag, to a 1520 previously negotiated BUNDLE group, associates a unique address 1521 with the added "m=" line, and associates the previously selected 1522 offerer BUNDLE address with each of the other bundled "m=" lines 1523 within the BUNDLE group. 1525 o An answer, in which the answerer associates the answerer BUNDLE 1526 address with each bundled "m=" line (including the newly added 1527 "m=" line) within the BUNDLE group. 1529 SDP Offer (1) 1531 v=0 1532 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 1533 s= 1534 c=IN IP4 atlanta.example.com 1535 t=0 0 1536 a=group:BUNDLE foo bar zen 1537 m=audio 10000 RTP/AVP 0 8 97 1538 b=AS:200 1539 a=mid:foo 1540 a=rtpmap:0 PCMU/8000 1541 a=rtpmap:8 PCMA/8000 1542 a=rtpmap:97 iLBC/8000 1543 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1544 m=video 10000 RTP/AVP 31 32 1545 b=AS:1000 1546 a=mid:bar 1547 a=rtpmap:31 H261/90000 1548 a=rtpmap:32 MPV/90000 1549 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1550 m=video 20000 RTP/AVP 66 1551 b=AS:1000 1552 a=mid:zen 1553 a=rtpmap:66 H261/90000 1554 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1556 SDP Answer (2) 1558 v=0 1559 o=bob 2808844564 2808844564 IN IP4 biloxi.example.com 1560 s= 1561 c=IN IP4 biloxi.example.com 1562 t=0 0 1563 a=group:BUNDLE foo bar zen 1564 m=audio 20000 RTP/AVP 0 1565 b=AS:200 1566 a=mid:foo 1567 a=rtpmap:0 PCMU/8000 1568 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1569 m=video 20000 RTP/AVP 32 1570 b=AS:1000 1571 a=mid:bar 1572 a=rtpmap:32 MPV/90000 1573 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1574 m=video 20000 RTP/AVP 66 1575 b=AS:1000 1576 a=mid:zen 1577 a=rtpmap:66 H261/90000 1578 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1580 17.4. Example: Offerer Moves A Media Description Out Of A BUNDLE Group 1582 The example below shows: 1584 o A subsequent offer (the BUNDLE group has been created as part of a 1585 previous offer/answer transaction), in which the offerer moves a 1586 bundled "m=" line out of a BUNDLE group, associates a unique 1587 address with the moved "m=" line, and associates the offerer 1588 BUNDLE address with each other bundled "m=" line within the BUNDLE 1589 group. 1591 o An answer, in which the answerer moves the "m=" line out of the 1592 BUNDLE group, associates unique address with the moved "m=" line, 1593 and associates the answerer BUNDLE address with each of the 1594 remaining bundled "m=" line within the BUNDLE group. 1596 SDP Offer (1) 1598 v=0 1599 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 1600 s= 1601 c=IN IP4 atlanta.example.com 1602 t=0 0 1603 a=group:BUNDLE foo bar 1604 m=audio 10000 RTP/AVP 0 8 97 1605 b=AS:200 1606 a=mid:foo 1607 a=rtpmap:0 PCMU/8000 1608 a=rtpmap:8 PCMA/8000 1609 a=rtpmap:97 iLBC/8000 1610 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1611 m=video 10000 RTP/AVP 31 32 1612 b=AS:1000 1613 a=mid:bar 1614 a=rtpmap:31 H261/90000 1615 a=rtpmap:32 MPV/90000 1616 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1617 m=video 50000 RTP/AVP 66 1618 b=AS:1000 1619 a=mid:zen 1620 a=rtpmap:66 H261/90000 1622 SDP Answer (2) 1624 v=0 1625 o=bob 2808844564 2808844564 IN IP4 biloxi.example.com 1626 s= 1627 c=IN IP4 biloxi.example.com 1628 t=0 0 1629 a=group:BUNDLE foo bar 1630 m=audio 20000 RTP/AVP 0 1631 b=AS:200 1632 a=mid:foo 1633 a=rtpmap:0 PCMU/8000 1634 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1635 m=video 20000 RTP/AVP 32 1636 b=AS:1000 1637 a=mid:bar 1638 a=rtpmap:32 MPV/90000 1639 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1640 m=video 60000 RTP/AVP 66 1641 b=AS:1000 1642 a=mid:zen 1643 a=rtpmap:66 H261/90000 1645 17.5. Example: Offerer Disables A Media Description Within A BUNDLE 1646 Group 1648 The example below shows: 1650 o A subsequent offer (the BUNDLE group has been created as part of a 1651 previous offer/answer transaction), in which the offerer disables 1652 a bundled "m=" line within BUNDLE group, assigns a zero port 1653 number to the disabled "m=" line, and associates the offerer 1654 BUNDLE address with each of the other bundled "m=" lines within 1655 the BUNDLE group. 1657 o An answer, in which the answerer moves the disabled "m=" line out 1658 of the BUNDLE group, assigns a zero port value to the disabled 1659 "m=" line, and associates the answerer BUNDLE address with each of 1660 the remaining bundled "m=" line within the BUNDLE group. 1662 SDP Offer (1) 1664 v=0 1665 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 1666 s= 1667 c=IN IP4 atlanta.example.com 1668 t=0 0 1669 a=group:BUNDLE foo bar 1670 m=audio 10000 RTP/AVP 0 8 97 1671 b=AS:200 1672 a=mid:foo 1673 a=rtpmap:0 PCMU/8000 1674 a=rtpmap:8 PCMA/8000 1675 a=rtpmap:97 iLBC/8000 1676 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1677 m=video 10000 RTP/AVP 31 32 1678 b=AS:1000 1679 a=mid:bar 1680 a=rtpmap:31 H261/90000 1681 a=rtpmap:32 MPV/90000 1682 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1683 m=video 0 RTP/AVP 66 1684 a=mid:zen 1685 a=rtpmap:66 H261/90000 1687 SDP Answer (2) 1689 v=0 1690 o=bob 2808844564 2808844564 IN IP4 biloxi.example.com 1691 s= 1692 c=IN IP4 biloxi.example.com 1693 t=0 0 1694 a=group:BUNDLE foo bar 1695 m=audio 20000 RTP/AVP 0 1696 b=AS:200 1697 a=mid:foo 1698 a=rtpmap:0 PCMU/8000 1699 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1700 m=video 20000 RTP/AVP 32 1701 b=AS:1000 1702 a=mid:bar 1703 a=rtpmap:32 MPV/90000 1704 a=extmap 1 urn:ietf:params:rtp-hdrext:sdes:mid 1705 m=video 0 RTP/AVP 66 1706 a=mid:zen 1707 a=rtpmap:66 H261/90000 1709 18. Acknowledgements 1711 The usage of the SDP grouping extension for negotiating bundled media 1712 is based on a similar alternatives proposed by Harald Alvestrand and 1713 Cullen Jennings. The BUNDLE extension described in this document is 1714 based on the different alternative proposals, and text (e.g. SDP 1715 examples) have been borrowed (and, in some cases, modified) from 1716 those alternative proposals. 1718 The SDP examples are also modified versions from the ones in the 1719 Alvestrand proposal. 1721 Thanks to Paul Kyzivat, Martin Thomson, Flemming Andreasen, Thomas 1722 Stach, Ari Keranen, Adam Roach, Christian Groves, Roman Shpount, 1723 Suhas Nandakumar, Nils Ohlmeier, Jens Guballa, Raju Makaraju and 1724 Justin Uberti for reading the text, and providing useful feedback. 1726 Thanks to Magnus Westerlund, Colin Perkins and Jonathan Lennox for 1727 providing help and text on the RTP/RTCP procedures. 1729 Thanks to Spotify for providing music for the countless hours of 1730 document editing. 1732 19. Change Log 1734 [RFC EDITOR NOTE: Please remove this section when publishing] 1736 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-27 1738 o - Yet another terminology change. 1740 o - Mux category considerations added. 1742 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-26 1744 o - ICE considerations modified: ICE-related SDP attributes only 1745 added to the bundled m- line representing the selected BUNDLE 1746 address. 1748 o - Reference to draft-ietf-mmusic-ice-sip-sdp added. 1750 o - Reference to RFC 5245 replaced with reference to draft-ietf-ice- 1751 rfc5245bis. 1753 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-25 1755 o - RTP/RTCP mux procedures updated with exclusive RTP/RTCP mux 1756 considerations. 1758 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-24 1760 o - Reference and procedures associated with exclusive RTP/RTCP mux 1761 added 1763 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-23 1765 o - RTCP-MUX mandatory for bundled RTP m- lines 1767 o - Editorial fixes based on comments from Flemming Andreasen 1769 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-22 1771 o - Correction of Ari's family name 1773 o - Editorial fixes based on comments from Thomas Stach 1775 o - RTP/RTCP correction based on comment from Magnus Westerlund 1777 o -- http://www.ietf.org/mail-archive/web/mmusic/current/ 1778 msg14861.html 1780 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-21 1782 o - Correct based on comment from Paul Kyzivat 1784 o -- 'received packets' replaced with 'received data' 1786 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-20 1788 o - Clarification based on comment from James Guballa 1790 o - Clarification based on comment from Flemming Andreasen 1792 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-19 1794 o - DTLS Considerations section added. 1796 o - BUNDLE semantics added to the IANA Considerations 1797 o - Changes based on WGLC comments from Adam Roach 1799 o -- http://www.ietf.org/mail-archive/web/mmusic/current/ 1800 msg14673.html 1802 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-18 1804 o - Changes based on agreements at IETF#92 1806 o -- BAS Offer removed, based on agreement at IETF#92. 1808 o -- Procedures regarding usage of SDP "b=" line is replaced with a 1809 reference to to draft-ietf-mmusic-sdp-mux-attributes. 1811 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-17 1813 o - Editorial changes based on comments from Magnus Westerlund. 1815 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-16 1817 o - Modification of RTP/RTCP multiplexing section, based on comments 1818 from Magnus Westerlund. 1820 o - Reference updates. 1822 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-15 1824 o - Editorial fix. 1826 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-14 1828 o - Editorial changes. 1830 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-13 1832 o Changes to allow a new suggested offerer BUNDLE address to be 1833 assigned to each bundled m- line. 1835 o Changes based on WGLC comments from Paul Kyzivat 1837 o - Editorial fixes 1839 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-12 1841 o Usage of SDP 'extmap' attribute added 1843 o SDP 'bundle-only' attribute scoped with "m=" lines with a zero 1844 port value 1846 o Changes based on WGLC comments from Thomas Stach 1848 o - ICE candidates not assigned to bundle-only m- lines with a zero 1849 port value 1851 o - Editorial changes 1853 o Changes based on WGLC comments from Colin Perkins 1855 o - Editorial changes: 1857 o -- "RTP SDES item" -> "RTCP SDES item" 1859 o -- "RTP MID SDES item" -> "RTCP MID SDES item" 1861 o - Changes in section 10.1.1: 1863 o -- "SHOULD NOT" -> "MUST NOT" 1865 o -- Additional text added to the Note 1867 o - Change to section 13.2: 1869 o -- Clarify that mid value is not zero terminated 1871 o - Change to section 13.3: 1873 o -- Clarify that mid value is not zero terminated 1875 o -- Clarify padding 1877 o Changes based on WGLC comments from Paul Kyzivat 1879 o - Editorial changes: 1881 o Changes based on WGLC comments from Jonathan Lennox 1883 o - Editorial changes: 1885 o - Defintion of SDP bundle-only attribute alligned with structure 1886 in 4566bis draft 1888 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-11 1890 o Editorial corrections based on comments from Harald Alvestrand. 1892 o Editorial corrections based on comments from Cullen Jennings. 1894 o Reference update (RFC 7160). 1896 o Clarification about RTCP packet sending when RTP/RTCP multiplexing 1897 is not used (http://www.ietf.org/mail-archive/web/mmusic/current/ 1898 msg13765.html). 1900 o Additional text added to the Security Considerations. 1902 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-10 1904 o SDP bundle-only attribute added to IANA Considerations. 1906 o SDES item and RTP header extension added to Abstract and 1907 Introduction. 1909 o Modification to text updating section 8.2 of RFC 3264. 1911 o Reference corrections. 1913 o Editorial corrections. 1915 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-09 1917 o Terminology change: "bundle-only attribute assigned to m= line" to 1918 "bundle-only attribute associated with m= line". 1920 o Editorial corrections. 1922 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-08 1924 o Editorial corrections. 1926 o - "of"->"if" (8.3.2.5). 1928 o - "optional"->"OPTIONAL" (9.1). 1930 o - Syntax/ABNF for 'bundle-only' attribute added. 1932 o - SDP Offer/Answer sections merged. 1934 o - 'Request new offerer BUNDLE address' section added 1936 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-07 1938 o OPEN ISSUE regarding Receiver-ID closed. 1940 o - RTP MID SDES Item. 1942 o - RTP MID Header Extension. 1944 o OPEN ISSUE regarding insertion of SDP 'rtcp' attribute in answers 1945 closed. 1947 o - Indicating that, when rtcp-mux is used, the answerer MUST NOT 1948 include an 'rtcp' attribute in the answer, based on the procedures 1949 in section 5.1.3 of RFC 5761. 1951 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-06 1953 o Draft title changed. 1955 o Added "SDP" to section names containing "Offer" or "Answer". 1957 o Editorial fixes based on comments from Paul Kyzivat 1958 (http://www.ietf.org/mail-archive/web/mmusic/current/ 1959 msg13314.html). 1961 o Editorial fixed based on comments from Colin Perkins 1962 (http://www.ietf.org/mail-archive/web/mmusic/current/ 1963 msg13318.html). 1965 o - Removed text about extending BUNDLE to allow multiple RTP 1966 sessions within a BUNDLE group. 1968 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-05 1970 o Major re-structure of SDP Offer/Answer sections, to align with RFC 1971 3264 structure. 1973 o Additional definitions added. 1975 o - Shared address. 1977 o - Bundled "m=" line. 1979 o - Bundle-only "m=" line. 1981 o - Offerer suggested BUNDLE mid. 1983 o - Answerer selected BUNDLE mid. 1985 o Q6 Closed (IETF#88): An Offerer MUST NOT assign a shared address 1986 to multiple "m=" lines until it has received an SDP Answer 1987 indicating support of the BUNDLE extension. 1989 o Q8 Closed (IETF#88): An Offerer can, before it knows whether the 1990 Answerer supports the BUNDLE extension, assign a zero port value 1991 to a 'bundle-only' "m=" line. 1993 o SDP 'bundle-only' attribute section added. 1995 o Connection data nettype/addrtype restrictions added. 1997 o RFC 3264 update section added. 1999 o Indicating that a specific payload type value can be used in 2000 multiple "m=" lines, if the value represents the same codec 2001 configuration in each "m=" line. 2003 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-04 2005 o Updated Offerer procedures (http://www.ietf.org/mail- 2006 archive/web/mmusic/current/msg12293.html). 2008 o Updated Answerer procedures (http://www.ietf.org/mail- 2009 archive/web/mmusic/current/msg12333.html). 2011 o Usage of SDP 'bundle-only' attribute added. 2013 o Reference to Trickle ICE document added. 2015 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-02 2017 o Mechanism modified, to be based on usage of SDP Offers with both 2018 different and identical port number values, depending on whether 2019 it is known if the remote endpoint supports the extension. 2021 o Cullen Jennings added as co-author. 2023 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-01 2025 o No changes. New version due to expiration. 2027 Changes from draft-ietf-mmusic-sdp-bundle-negotiation-00 2029 o No changes. New version due to expiration. 2031 Changes from draft-holmberg-mmusic-sdp-multiplex-negotiation-00 2033 o Draft name changed. 2035 o Harald Alvestrand added as co-author. 2037 o "Multiplex" terminology changed to "bundle". 2039 o Added text about single versus multiple RTP Sessions. 2041 o Added reference to RFC 3550. 2043 20. References 2045 20.1. Normative References 2047 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2048 Requirement Levels", BCP 14, RFC 2119, 2049 DOI 10.17487/RFC2119, March 1997, 2050 . 2052 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 2053 with Session Description Protocol (SDP)", RFC 3264, 2054 DOI 10.17487/RFC3264, June 2002, 2055 . 2057 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 2058 Jacobson, "RTP: A Transport Protocol for Real-Time 2059 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 2060 July 2003, . 2062 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute 2063 in Session Description Protocol (SDP)", RFC 3605, 2064 DOI 10.17487/RFC3605, October 2003, 2065 . 2067 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 2068 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 2069 July 2006, . 2071 [RFC4961] Wing, D., "Symmetric RTP / RTP Control Protocol (RTCP)", 2072 BCP 131, RFC 4961, DOI 10.17487/RFC4961, July 2007, 2073 . 2075 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 2076 (ICE): A Protocol for Network Address Translator (NAT) 2077 Traversal for Offer/Answer Protocols", RFC 5245, 2078 DOI 10.17487/RFC5245, April 2010, 2079 . 2081 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP 2082 Header Extensions", RFC 5285, DOI 10.17487/RFC5285, July 2083 2008, . 2085 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and 2086 Control Packets on a Single Port", RFC 5761, 2087 DOI 10.17487/RFC5761, April 2010, 2088 . 2090 [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer 2091 Security (DTLS) Extension to Establish Keys for the Secure 2092 Real-time Transport Protocol (SRTP)", RFC 5764, 2093 DOI 10.17487/RFC5764, May 2010, 2094 . 2096 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description 2097 Protocol (SDP) Grouping Framework", RFC 5888, 2098 DOI 10.17487/RFC5888, June 2010, 2099 . 2101 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 2102 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 2103 January 2012, . 2105 [I-D.ietf-ice-rfc5245bis] 2106 Keranen, A. and J. Rosenberg, "Interactive Connectivity 2107 Establishment (ICE): A Protocol for Network Address 2108 Translator (NAT) Traversal", draft-ietf-ice-rfc5245bis-01 2109 (work in progress), December 2015. 2111 [I-D.ietf-mmusic-sdp-mux-attributes] 2112 Nandakumar, S., "A Framework for SDP Attributes when 2113 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12 2114 (work in progress), January 2016. 2116 [I-D.ietf-mmusic-mux-exclusive] 2117 Holmberg, C., "Indicating Exclusive Support of RTP/RTCP 2118 Multiplexing using SDP", draft-ietf-mmusic-mux- 2119 exclusive-03 (work in progress), February 2016. 2121 [I-D.ietf-mmusic-ice-sip-sdp] 2122 Petit-Huguenin, M., Keranen, A., and S. Nandakumar, "Using 2123 Interactive Connectivity Establishment (ICE) with Session 2124 Description Protocol (SDP) offer/answer and Session 2125 Initiation Protocol (SIP)", draft-ietf-mmusic-ice-sip- 2126 sdp-07 (work in progress), October 2015. 2128 20.2. Informative References 2130 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 2131 A., Peterson, J., Sparks, R., Handley, M., and E. 2132 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 2133 DOI 10.17487/RFC3261, June 2002, 2134 . 2136 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session 2137 Description Protocol (SDP) Security Descriptions for Media 2138 Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, 2139 . 2141 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific 2142 Media Attributes in the Session Description Protocol 2143 (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009, 2144 . 2146 [RFC7160] Petit-Huguenin, M. and G. Zorn, Ed., "Support for Multiple 2147 Clock Rates in an RTP Session", RFC 7160, 2148 DOI 10.17487/RFC7160, April 2014, 2149 . 2151 [I-D.ietf-mmusic-trickle-ice] 2152 Ivov, E., Rescorla, E., and J. Uberti, "Trickle ICE: 2153 Incremental Provisioning of Candidates for the Interactive 2154 Connectivity Establishment (ICE) Protocol", draft-ietf- 2155 mmusic-trickle-ice-02 (work in progress), January 2015. 2157 Appendix A. Design Considerations 2159 A.1. General 2161 One of the main issues regarding the BUNDLE grouping extensions has 2162 been whether, in SDP Offers and SDP Answers, the same port value 2163 should be inserted in "m=" lines associated with a BUNDLE group, as 2164 the purpose of the extension is to negotiate the usage of a single 2165 address:port combination for media specified by the "m=" lines. 2166 Issues with both approaches, discussed in the Appendix have been 2167 raised. The outcome was to specify a mechanism which uses SDP Offers 2168 with both different and identical port values. 2170 Below are the primary issues that have been considered when defining 2171 the "BUNDLE" grouping extension: 2173 o 1) Interoperability with existing UAs. 2175 o 2) Interoperability with intermediary B2BUA- and proxy entities. 2177 o 3) Time to gather, and the number of, ICE candidates. 2179 o 4) Different error scenarios, and when they occur. 2181 o 5) SDP Offer/Answer impacts, including usage of port number value 2182 zero. 2184 NOTE: Before this document is published as an RFC, this 2185 Appendix might be removed. 2187 A.2. UA Interoperability 2189 Consider the following SDP Offer/Answer exchange, where Alice sends 2190 an SDP Offer to Bob: 2192 SDP Offer 2194 v=0 2195 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 2196 s= 2197 c=IN IP4 atlanta.example.com 2198 t=0 0 2199 m=audio 10000 RTP/AVP 97 2200 a=rtpmap:97 iLBC/8000 2201 m=video 10002 RTP/AVP 97 2202 a=rtpmap:97 H261/90000 2204 SDP Answer 2206 v=0 2207 o=bob 2808844564 2808844564 IN IP4 biloxi.example.com 2208 s= 2209 c=IN IP4 biloxi.example.com 2210 t=0 0 2211 m=audio 20000 RTP/AVP 97 2212 a=rtpmap:97 iLBC/8000 2213 m=video 20002 RTP/AVP 97 2214 a=rtpmap:97 H261/90000 2216 RFC 4961 specifies a way of doing symmetric RTP but that is an a 2217 later invention to RTP and Bob can not assume that Alice supports RFC 2218 4961. This means that Alice may be sending RTP from a different port 2219 than 10000 or 10002 - some implementation simply send the RTP from an 2220 ephemeral port. When Bob's endpoint receives an RTP packet, the only 2221 way that Bob know if it should be passed to the video or audio codec 2222 is by looking at the port it was received on. This lead some SDP 2223 implementations to use the fact that each "m=" line had a different 2224 port number to use that port number as an index to find the correct m 2225 line in the SDP. As a result, some implementations that do support 2226 symmetric RTP and ICE still use a SDP data structure where SDP with 2227 "m=" lines with the same port such as: 2229 SDP Offer 2231 v=0 2232 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 2233 s= 2234 c=IN IP4 atlanta.example.com 2235 t=0 0 2236 m=audio 10000 RTP/AVP 97 2237 a=rtpmap:97 iLBC/8000 2238 m=video 10000 RTP/AVP 98 2239 a=rtpmap:98 H261/90000 2241 will result in the second "m=" line being considered an SDP error 2242 because it has the same port as the first line. 2244 A.3. Usage of port number value zero 2246 In an SDP Offer or SDP Answer, the media specified by an "m=" line 2247 can be disabled/rejected by setting the port number value to zero. 2248 This is different from e.g. using the SDP direction attributes, where 2249 RTCP traffic will continue even if the SDP "inactive" attribute is 2250 indicated for the associated "m=" line. 2252 If each "m=" line associated with a BUNDLE group would contain 2253 different port values, and one of those port values would be used for 2254 a BUNDLE address associated with the BUNDLE group, problems would 2255 occur if an endpoint wants to disable/reject the "m=" line associated 2256 with that port, by setting the port value to zero. After that, no 2257 "m=" line would contain the port value which is used for the BUNDLE 2258 address. In addition, it is unclear what would happen to the ICE 2259 candidates associated with the "m=" line, as they are also used for 2260 the BUNDLE address. 2262 A.4. B2BUA And Proxy Interoperability 2264 Some back to back user agents may be configured in a mode where if 2265 the incoming call leg contains an SDP attribute the B2BUA does not 2266 understand, the B2BUS still generates that SDP attribute in the Offer 2267 for the outgoing call leg. Consider an B2BUA that did not understand 2268 the SDP "rtcp" attribute, defined in RFC 3605, yet acted this way. 2269 Further assume that the B2BUA was configured to tear down any call 2270 where it did not see any RTCP for 5 minutes. In this cases, if the 2271 B2BUA received an Offer like: 2273 SDP Offer 2275 v=0 2276 o=alice 2890844526 2890844526 IN IP4 atlanta.example.com 2277 s= 2278 c=IN IP4 atlanta.example.com 2279 t=0 0 2280 m=audio 49170 RTP/AVP 0 2281 a=rtcp:53020 2283 It would be looking for RTCP on port 49172 but would not see any 2284 because the RTCP would be on port 53020 and after five minutes, it 2285 would tear down the call. Similarly, an SBC that did not understand 2286 BUNDLE yet put BUNDLE in it's offer may be looking for media on the 2287 wrong port and tear down the call. It is worth noting that a B2BUA 2288 that generated an Offer with capabilities it does not understand is 2289 not compliant with the specifications. 2291 A.4.1. Traffic Policing 2293 Sometimes intermediaries do not act as B2BUA, in the sense that they 2294 don't modify SDP bodies, nor do they terminate SIP dialogs. Still, 2295 however, they may use SDP information (e.g. IP address and port) in 2296 order to control traffic gating functions, and to set traffic 2297 policing rules. There might be rules which will trigger a session to 2298 be terminated in case media is not sent or received on the ports 2299 retrieved from the SDP. This typically occurs once the session is 2300 already established and ongoing. 2302 A.4.2. Bandwidth Allocation 2304 Sometimes intermediaries do not act as B2BUA, in the sense that they 2305 don't modify SDP bodies, nor do they terminate SIP dialogs. Still, 2306 however, they may use SDP information (e.g. codecs and media types) 2307 in order to control bandwidth allocation functions. The bandwidth 2308 allocation is done per "m=" line, which means that it might not be 2309 enough if media specified by all "m=" lines try to use that 2310 bandwidth. That may either simply lead to bad user experience, or to 2311 termination of the call. 2313 A.5. Candidate Gathering 2315 When using ICE, an candidate needs to be gathered for each port. 2316 This takes approximately 20 ms extra for each extra "m=" line due to 2317 the NAT pacing requirements. All of this gather can be overlapped 2318 with other things while the page is loading to minimize the impact. 2319 If the client only wants to generate TURN or STUN ICE candidates for 2320 one of the "m=" lines and then use trickle ICE 2321 [I-D.ietf-mmusic-trickle-ice] to get the non host ICE candidates for 2322 the rest of the "m=" lines, it MAY do that and will not need any 2323 additional gathering time. 2325 Some people have suggested a TURN extension to get a bunch of TURN 2326 allocation at once. This would only provide a single STUN result so 2327 in cases where the other end did not support BUNDLE, may cause more 2328 use of the TURN server but would be quick in the cases where both 2329 sides supported BUNDLE and would fall back to a successful call in 2330 the other cases. 2332 Authors' Addresses 2334 Christer Holmberg 2335 Ericsson 2336 Hirsalantie 11 2337 Jorvas 02420 2338 Finland 2340 Email: christer.holmberg@ericsson.com 2342 Harald Tveit Alvestrand 2343 Google 2344 Kungsbron 2 2345 Stockholm 11122 2346 Sweden 2348 Email: harald@alvestrand.no 2350 Cullen Jennings 2351 Cisco 2352 400 3rd Avenue SW, Suite 350 2353 Calgary, AB T2P 4H2 2354 Canada 2356 Email: fluffy@iii.ca