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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Nandakumar 3 Internet-Draft Cisco 4 Intended status: Standards Track December 11, 2014 5 Expires: June 14, 2015 7 A Framework for SDP Attributes when Multiplexing 8 draft-ietf-mmusic-sdp-mux-attributes-06 10 Abstract 12 The Session Description Protocol (SDP) provides mechanisms to 13 describe attributes of multimedia sessions and of individual media 14 streams (e.g., Real-time Transport Protocol (RTP) sessions) within a 15 multimedia session. [I-D.ietf-mmusic-sdp-bundle-negotiation] 16 provides SDP extensions to negotiate the usage of single 5-tuple for 17 sending and receiving media associated with multiple media 18 descriptions ("m=" lines). Such a mechanism has made it necessary to 19 understand the semantic implications of the SDP attributes associated 20 with the RTP Media Streams multiplexed over a single underlying 21 transport layer flow. 23 The purpose of this specification is to provide a framework for 24 analyzing the multiplexing characteristics of SDP attributes. This 25 specification also categorizes the existing SDP attributes based on 26 the framework described herein. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at http://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on June 14, 2015. 45 Copyright Notice 47 Copyright (c) 2014 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 This document may contain material from IETF Documents or IETF 61 Contributions published or made publicly available before November 62 10, 2008. The person(s) controlling the copyright in some of this 63 material may not have granted the IETF Trust the right to allow 64 modifications of such material outside the IETF Standards Process. 65 Without obtaining an adequate license from the person(s) controlling 66 the copyright in such materials, this document may not be modified 67 outside the IETF Standards Process, and derivative works of it may 68 not be created outside the IETF Standards Process, except to format 69 it for publication as an RFC or to translate it into languages other 70 than English. 72 Table of Contents 74 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 75 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 76 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 6 77 4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . 7 78 4.1. Category: NORMAL . . . . . . . . . . . . . . . . . . . . 7 79 4.2. Category: NOT RECOMMENDED . . . . . . . . . . . . . . . . 8 80 4.3. Category: IDENTICAL . . . . . . . . . . . . . . . . . . . 8 81 4.4. Category: SUM . . . . . . . . . . . . . . . . . . . . . . 8 82 4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 9 83 4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 10 84 4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 11 85 4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 12 86 4.9. Category: TBD . . . . . . . . . . . . . . . . . . . . . . 12 87 5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 12 88 5.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 13 89 5.2. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 14 90 5.3. RFC5761 - Multiplexing RTP and RTCP . . . . . . . . . . . 15 91 5.4. RFC3312 - Integration of Resource Management and (SIP) . 15 92 5.5. RFC4574 - SDP Label Attribute . . . . . . . . . . . . . . 16 93 5.6. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 16 94 5.7. RFC4568 - SDP Security Descriptions . . . . . . . . . . . 17 95 5.8. RFC5762 - RTP over DCCP . . . . . . . . . . . . . . . . . 17 96 5.9. RFC6773 - DCCP-UDP Encapsulation . . . . . . . . . . . . 18 97 5.10. RFC5506 - Reduced-Size RTCP in RTP Profile . . . . . . . 19 98 5.11. RFC6787 - Media Resource Control Protocol Version 2 . . . 19 99 5.12. RFC5245 - Interactive Connectivity Establishment (ICE) . 20 100 5.13. RFC5285 - RTP Header Extensions . . . . . . . . . . . . . 21 101 5.14. RFC3605 - RTCP attribute in SDP . . . . . . . . . . . . . 22 102 5.15. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 22 103 5.16. RFC7273 - RTP Clock Source Signalling . . . . . . . . . . 23 104 5.17. RFC6236 - Image Attributes in SDP . . . . . . . . . . . . 24 105 5.18. RFC7197 - Duplication Delay Attribute in SDP . . . . . . 24 106 5.19. RFC7266 - RTCP XR Blocks for MOS Metric Reporting . . . 24 107 5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions . . 25 108 5.21. RFC6230 - Media Control Channel Framework . . . . . . . . 25 109 5.22. RFC6364 - SDP Elements for FEC Framework . . . . . . . . 26 110 5.23. RFC4796 - Content Attribute . . . . . . . . . . . . . . . 26 111 5.24. RFC3407 - SDP Simple Capability Declaration . . . . . . . 27 112 5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP 113 Sessions . . . . . . . . . . . . . . . . . . . . . . . . 27 114 5.26. RFC6714 - MSRP-CEMA . . . . . . . . . . . . . . . . . . . 28 115 5.27. RFC4583 - SDP Format for BFCP Streams . . . . . . . . . . 28 116 5.28. RFC5547 - SDP Offer/Answer for File Transfer . . . . . . 29 117 5.29. RFC6849 - SDP and RTP Media Loopback Extension . . . . . 29 118 5.30. RFC5760 - RTCP with Unicast Feedback . . . . . . . . . . 30 119 5.31. RFC3611 - RTCP XR . . . . . . . . . . . . . . . . . . . . 30 120 5.32. RFC5939 - SDP Capability Negotiation . . . . . . . . . . 30 121 5.33. RFC6871- SDP Media Capabilities Negotiation . . . . . . . 31 122 5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP . . 32 123 5.35. RFC4567 - Key Management Extensions for SDP and RTSP . . 33 124 5.36. RFC4572 - Comedia over TLS in SDP . . . . . . . . . . . . 34 125 5.37. RFC4570 - SDP Source Filters . . . . . . . . . . . . . . 34 126 5.38. RFC6128 - RTCP Port for Multicast Sessions . . . . . . . 35 127 5.39. RFC6189 - ZRTP . . . . . . . . . . . . . . . . . . . . . 35 128 5.40. RFC4145 - Connection-Oriented Media . . . . . . . . . . . 35 129 5.41. RFC6947 - The SDP ALTC Attribute . . . . . . . . . . . . 36 130 5.42. RFC7195 - SDP Extension for Circuit Switched Bearers 131 in PSTN . . . . . . . . . . . . . . . . . . . . . . . . . 36 132 5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP) . . 37 133 5.44. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . 37 134 5.45. RFC6193 - Media Description for IKE in SDP . . . . . . . 38 135 5.46. RFC2326 - Real Time Streaming Protocol . . . . . . . . . 39 136 5.47. RFC6064 - SDP and RTSP Extensions for 3GPP . . . . . . . 39 137 5.48. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . . 42 138 5.49. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 45 139 5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . . 45 140 5.51. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 45 141 5.52. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 46 142 5.53. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 46 143 5.54. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 47 144 5.55. ITU-T Q.1970 . . . . . . . . . . . . . . . . . . . . . . 48 145 5.56. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 49 146 5.57. RFC4975 - The Message Session Relay Protocol . . . . . . 50 147 5.58. Historical Attributes . . . . . . . . . . . . . . . . . . 50 148 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 50 149 6.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 51 150 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . 51 151 6.3. RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . 52 152 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 52 153 7.1. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 52 154 7.2. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 53 155 7.3. RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . 54 156 7.4. RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . . 54 157 7.5. RFC6642 - Third-Party Loss Report . . . . . . . . . . . . 55 158 7.6. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 56 159 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 56 160 8.1. RFC5888 - SDP Grouping Framework . . . . . . . . . . . . 56 161 8.2. RFC3524 - Mapping Media Streams to Resource 162 Reservation Flows . . . . . . . . . . . . . . . . . . . . 57 163 8.3. RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . 57 164 8.4. RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . . 58 165 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP . . 58 166 8.6. RFC7104 - Duplication Grouping Semantics in the SDP . . 59 167 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 59 168 9.1. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 59 169 9.2. RFC7104 - Duplication Grouping Semantics in the SDP . . . 59 170 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 60 171 10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 60 172 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 60 173 11.1. RFC4566 SDP: Session Description Protocol . . . . . . . 60 174 12. content Attribute Analysis . . . . . . . . . . . . . . . . . 61 175 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 61 176 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 61 177 13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . 61 178 14. Multiplexing Considerations for Encapsulating Attributes . . 62 179 14.1. RFC3407 - cpar Attribute Analysis . . . . . . . . . . . 62 180 14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 63 181 14.2.1. Recommendation - Procedures for Potential 182 Configuration Pairing . . . . . . . . . . . . . . . 64 183 14.2.1.1. Example: Transport Capability Multiplexing . . . 65 184 14.2.1.2. Example: Attribute Capability Multiplexing . . . 66 185 14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 66 186 14.3.1. Recommendation: Dealing with Payload Type Numbers . 66 187 14.3.1.1. Example: Attribute Capability Under Shared 188 Payload Type . . . . . . . . . . . . . . . . . . 67 190 14.3.2. Recommendation: Dealing with Latent Configurations . 68 191 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 68 192 15.1. New 'Multiplexing Categories' subregistry . . . . . . . 68 193 15.2. 'Mux Category' column for subregistries . . . . . . . . 69 194 15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 69 195 15.2.2. Table: att-field (session level) . . . . . . . . . . 70 196 15.2.3. Table: att-field (both session and media level) . . 71 197 15.2.4. Table: att-field (media level only) . . . . . . . . 72 198 15.2.5. Table: att-field (source level) . . . . . . . . . . 75 199 15.2.6. Table: content SDP Parameters . . . . . . . . . . . 76 200 15.2.7. Table: Semantics for the 'group' SDP Attribute . . . 76 201 15.2.8. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 77 202 15.2.9. Table: 'ack' and 'nack' Attribute Values . . . . . . 77 203 15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . . 77 204 15.2.11. Table: 'cs-correlation' Attribute Values . . . . . . 78 205 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 78 206 15.2.13. Table: SDP/RTSP key management protocol identifiers 78 207 15.2.14. Table: Codec Control Messages . . . . . . . . . . . 79 208 15.2.15. Table: QoS Mechanism Tokens . . . . . . . . . . . . 79 209 15.2.16. Table: SDP Capability Negotiation Option Tags . . . 79 210 15.2.17. Table: Timestamp Reference Clock Source Parameters . 80 211 15.2.18. Table: Media Clock Source Parameters . . . . . . . . 80 212 16. Security Considerations . . . . . . . . . . . . . . . . . . . 81 213 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 81 214 18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 81 215 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 84 216 19.1. Normative References . . . . . . . . . . . . . . . . . . 84 217 19.2. Informative References . . . . . . . . . . . . . . . . . 84 218 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 90 220 1. Introduction 222 SDP defines several attributes for capturing characteristics that 223 apply to the individual media descriptions (described by "m=" lines") 224 and the overall multimedia session. Typically different media types 225 (audio, video, etc.) described using different media descriptions 226 represent separate RTP Sessions that are carried over individual 227 transport layer flows. However 228 [I-D.ietf-mmusic-sdp-bundle-negotiation] defines a way to use a 229 single address:port combination (BUNDLE address) for receiving media 230 associated with multiple SDP media descriptions. This would for e.g. 231 allow the usage of a single set of ICE [RFC5245] candidates for 232 multiple media descriptions. This in turn has made necessary to 233 understand the interpretation and usage of the SDP attributes defined 234 for the multiplexed media descriptions. 236 Given the number of SDP attributes registered with the [IANA] and 237 possibility of new attributes being defined in the future, there is 238 need for generic future-proof framework to analyze these attributes 239 for their applicability in the transport multiplexing use-cases. 241 The document starts with providing the motivation for requiring such 242 a framework. This is followed by introduction to the SDP attribute 243 analysis framework/procedures, following which several sections 244 applies the framework to the SDP attributes registered with the 245 [IANA]. 247 2. Terminology 249 5-tuple: A collection of the following values: source address, source 250 port, destination address, destination port, and transport-layer 251 protocol. 253 The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", 254 "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be 255 interpreted as described in [RFC2119]. 257 3. Motivation 259 The time and complications of setting up ICE [RFC5245] and DTLS-SRTP 260 [RFC5763] transports for use by RTP, and conservation of ports, forms 261 an requirement to try and reduce the number of transport level flows 262 needed. This has resulted in the definition of ways, such as, 263 [I-D.ietf-mmusic-sdp-bundle-negotiation] to multiplex RTP over a 264 single transport flow in order to preserve network resources such as 265 port numbers. This imposes further restrictions on applicability of 266 the SDP attributes as they are defined today. 268 The specific problem is that there are attribute combinations which 269 make sense when specified on independent "m= " lines -- as with 270 classical SDP -- that do not make sense when those "m=" lines are 271 then multiplexed over the same transport. To give an obvious 272 example, ICE permits each "m=" line to have an independently 273 specified ice-ufrag attribute. However, if the media from multiple 274 "m=" lines is multiplexed over the same ICE component, then the 275 meaning of media-level ice-ufrag attributes becomes muddled. 277 As of today there are close to 250 SDP attributes registered with the 278 [IANA] and more will be added in the future. There is no clearly 279 defined procedure to establish the validity/applicability of these 280 attribute when used with transport multiplexing. 282 4. SDP Attribute Analysis Framework 284 Attributes in an SDP session description can be defined at the 285 session-level and media-level. These attributes could be 286 semantically grouped as noted below. 288 o Attributes related to media content such as media type, encoding 289 schemes, payload types. 291 o Attributes specifying media transport characteristics like RTP/ 292 RTCP port numbers, network addresses, QOS. 294 o Metadata description attributes capturing session timing and 295 origin information. 297 o Attributes establishing relationships between media streams such 298 as grouping framework 300 With the above semantic grouping as a reference, the proposed 301 framework classifies each attribute into one of the following 302 categories: 304 4.1. Category: NORMAL 306 Attributes that can be independently specified when multiplexing and 307 retain their original semantics. 309 In the example given below, the direction and label attributes are 310 independently specified for audio and video "m=" lines. These 311 attributes are not impacted by multiplexing these media streams over 312 a single transport layer flow. 314 v=0 315 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 316 s= 317 c=IN IP4 host.atlanta.example.com 318 t=0 0 319 m=audio 49172 RTP/AVP 99 320 a=sendonly 321 a=label:1 322 a=rtpmap:99 iLBC/8000 323 m=video 49172 RTP/AVP 31 324 a=recvonly 325 a=label:2 326 a=rtpmap:31 H261/90000 328 4.2. Category: NOT RECOMMENDED 330 Attributes that are recommended against multiplexing since their 331 usage under multiplexing might lead to incorrect behavior. 333 Example: Multiplexing media descriptions having attribute zrtp-hash 334 defined with the media descriptions lacking it, would either 335 complicate the handling of multiplexed streams or might fail 336 multiplexing altogether. 338 v=0 339 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com 340 s= 341 c=IN IP4 client.biloxi.example.com 342 t=0 0 343 m=audio 3456 RTP/AVP 97 // with zrtp 344 a=rtpmap:97 iLBC/8000 345 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2 346 df881ae642c371ba46df 347 m=video 34567 RTP/AVP 31 //without zrtp 348 a=rtpmap:31 H261/90000 350 4.3. Category: IDENTICAL 352 Attributes and their associated values (if any) that MUST be 353 identical across all the media descriptions being multiplexed. 355 Attributes such as rtcp-mux fall into this category. Since RTCP 356 reporting is done per RTP Session, RTCP Multiplexing MUST be enabled 357 for both the audio and video "m=" lines if they are transported over 358 a single 5-tuple. 360 v=0 361 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com 362 s= 363 c=IN IP4 client.biloxi.example.com 364 t=0 0 365 m=audio 34567 RTP/AVP 97 366 a=rtcp-mux 367 m=video 34567 RTP/AVP 31 368 a=rtpmap:31 H261/90000 369 a=rtcp-mux 371 4.4. Category: SUM 373 Attributes can be set as they are normally used but software using 374 them in the multiplexing scenario, MUST apply the sum of all the 375 attributes being multiplexed instead of trying to use them 376 independently. This is typically used for bandwidth or other rate 377 limiting attributes to the underlying transport. 379 The software parsing the SDP sample below, should use the aggregate 380 Application Specific (AS) bandwidth value from the individual media 381 descriptions to determine the AS value for the multiplexed session. 382 Thus the calculated AS value would be 256+64 bytes for the given 383 example. 385 v=0 386 o=test 2890844526 2890842807 IN IP4 126.16.64.4 387 c=IN IP4 client.biloxi.example.com 388 t=0 0 389 m=audio 49170 RTP/AVP 0 390 b=AS:64 391 m=video 51372 RTP/AVP 31 392 b=AS:256 394 4.5. Category: TRANSPORT 396 Attributes that can be set normally for multiple items in a 397 multiplexed group but the software MUST pick just one of the 398 attributes of the given type for use. The one chosen is the 399 attribute associated with the "m=" line that represents the 400 information being used for the transport of the RTP. 402 In the example below, "a=crypto" attribute is defined for both the 403 audio and the video "m=" lines. The video media line's a=crypto 404 attribute is chosen since its mid value (bar) appears first in the 405 a=group:BUNDLE line. This is due to BUNDLE grouping semantic 406 [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values 407 from "m=" line corresponding to the mid appearing first on the 408 a=group:BUNDLE line to be considered for setting up the RTP 409 Transport. 411 v=0 412 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 413 s= 414 c=IN IP4 host.atlanta.example.com 415 t=0 0 416 a=group:BUNDLE bar foo 417 m=audio 49172 RTP/AVP 99 418 a=mid:foo 419 a=crypto:1 AES_CM_128_HMAC_SHA1_80 420 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32 421 a=rtpmap:99 iLBC/8000 422 m=video 51374 RTP/AVP 31 423 a=mid:bar 424 a=crypto:1 AES_CM_128_HMAC_SHA1_80 425 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 426 a=rtpmap:96 H261/90000 428 4.6. Category: INHERIT 430 Attributes that encapsulate other SDP attributes or parameters. 431 These attributes inherit their multiplexing characteristics from the 432 attributes or parameters they encapsulate. Such attributes as of 433 today, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of a 434 generic framework for indicating and negotiating transport, media and 435 media format related capabilities in the SDP. 437 The inheritance manifests itself when the encapsulated attribute or 438 parameter is being leveraged. In the case of SDP Capability 439 Negotiation [RFC5939] for example, this occurs when a capability 440 (encapsulating attribute) is used as part of a configuration; the 441 configuration inherits the multiplexing category of each of its 442 constituent (encapsulated) attributes and parameters. This in turn 443 may place constraints on what constitutes a valid configuration from 444 a multiplexing point of view, e.g. because some attributes must be 445 IDENTICAL (see Section 14 for further details). 447 v=0 448 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 449 s= 450 c=IN IP4 host.atlanta.example.com 451 t=0 0 452 m=video 3456 RTP/AVP 100 453 a=rtpmap:100 VP8/90000 454 a=fmtp:100 max-fr=30;max-fs=8040 455 a=sqn: 0 456 a=cdsc: 1 video RTP/AVP 100 457 a=cpar: a=rtcp-mux 458 m=video 3456 RTP/AVP 101 459 a=rtpmap:101 VP8/90000 460 a=fmtp:100 max-fr=15;max-fs=1200 461 a=cdsc: 2 video RTP/AVP 101 462 a=cpar: a=rtcp-mux 464 In the above example, the category IDENTICAL is inherited for the 465 cpar encapsulated rtcp-mux attribute. 467 4.7. Category: IDENTICAL-PER-PT 469 Attributes that define the RTP payload configuration on per Payload 470 Type basis and MUST have identical values across all the media 471 descriptions for a given RTP Payload Type when repeated. These 472 Payload Types identify the same codec configuration as defined in the 473 Section 10.1.2 of [I-D.ietf-mmusic-sdp-bundle-negotiation] under this 474 context. 476 In the SDP example below, Payload Types 96 and 97 are repeated across 477 all the video "m=" lines and all the payload specific parameters (ex: 478 rtpmap, fmtp) are identical. 480 v=0 481 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 482 s= 483 c=IN IP4 host.atlanta.example.com 484 t=0 0 485 a=group:BUNDLE cam1, cam2 486 m= video 96 97 487 a=mid:cam1 488 a=rtpmap:96 H264/90000 489 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 490 max-mbps=108000; max-br=1000 491 a=rtpmap:97 H264/90000 492 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 493 max-mbps=7200; max-br=200 494 m= video 96 97 495 a=mid:cam2 496 a=rtpmap:96 H264/90000 497 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 498 max-mbps=108000; max-br=1000 499 a=rtpmap:97 H264/90000 500 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 501 max-mbps=7200; max-br=200 503 4.8. Category: SPECIAL 505 Attributes where the text in the specification defining the attribute 506 must be consulted for further handling when multiplexed. 508 As an example, for the attribute extmap, the specification defining 509 the extension must be referred to understand the multiplexing 510 implications. 512 4.9. Category: TBD 514 Attributes that have not been analyzed under the proposed 515 multiplexing framework yet. For the purposes of implementations it 516 is advised to consider "NOT RECOMMENDED" as the category when 517 multiplexing these attributes. 519 5. Analysis of Existing Attributes 521 This section analyzes attributes listed in [IANA], grouped under the 522 IETF document that defines them. 524 The "Level" column indicates whether the attribute is currently 525 specified as: 527 o S -- Session level 528 o M -- Media level 530 o B -- Both 532 o SR -- Source-level (for a single SSRC) 534 The "Mux Category" column identifies multiplexing category assigned 535 per attribute and the "Notes" column captures additional informative 536 details regarding the assigned category, wherever necessary. 538 5.1. RFC4566 - SDP: Session Description Protocol 540 [RFC4566] defines the Session Description Protocol (SDP) that is 541 intended for describing multimedia sessions for the purposes of 542 session announcement, session invitation, and other forms of 543 multimedia session initiation. 545 +-----------------+---------------------+-------+-------------------+ 546 | Name | Notes | Level | Mux Category | 547 +-----------------+---------------------+-------+-------------------+ 548 | sendrecv | Not impacted | B | NORMAL | 549 | | | | | 550 | sendonly | Not impacted | B | NORMAL | 551 | | | | | 552 | recvonly | Not impacted | B | NORMAL | 553 | | | | | 554 | inactive | Not impacted | B | NORMAL | 555 | | | | | 556 | cat | Not impacted | S | NORMAL | 557 | | | | | 558 | ptime | The attribute value | M | IDENTICAL-PER-PT | 559 | | must be same for a | | | 560 | | given codec | | | 561 | | configuration | | | 562 | | | | | 563 | maxptime | The attribute value | M | IDENTICAL-PER-PT | 564 | | must be same for a | | | 565 | | given codec | | | 566 | | configuration | | | 567 | | | | | 568 | orient | Not Impacted | M | NORMAL | 569 | | | | | 570 | framerate | The attribute value | M | IDENTICAL-PER-PT | 571 | | must be same for a | | | 572 | | given codec | | | 573 | | configuration | | | 574 | | | | | 575 | quality | Not Impacted | M | NORMAL | 576 | | | | | 577 | rtpmap | The attribute value | M | IDENTICAL-PER-PT | 578 | | must be same for a | | | 579 | | given codec | | | 580 | | configuration | | | 581 | | | | | 582 | fmtp | The attribute value | M | IDENTICAL-PER-PT | 583 | | must be same for a | | | 584 | | given codec | | | 585 | | configuration | | | 586 | | | | | 587 | keywds | Not impacted | S | NORMAL | 588 | | | | | 589 | type | Not Impacted | S | NORMAL | 590 | | | | | 591 | type:broadcast | Not Impacted | S | NORMAL | 592 | | | | | 593 | type:H332 | Not Impacted | S | NORMAL | 594 | | | | | 595 | type:meeting | Not Impacted | S | NORMAL | 596 | | | | | 597 | type:moderated | Not Impacted | S | NORMAL | 598 | | | | | 599 | type:test | Not Impacted | S | NORMAL | 600 | | | | | 601 | tool | Not Impacted | S | NORMAL | 602 | | | | | 603 | charset | Not Impacted | S | NORMAL | 604 | | | | | 605 | sdplang | Not Impacted | B | NORMAL | 606 | | | | | 607 | lang | Not Impacted | B | NORMAL | 608 | | | | | 609 +-----------------+---------------------+-------+-------------------+ 611 RFC4566 Attribute Analysis 613 5.2. RFC4585 - RTP/AVPF 615 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 616 enables receivers to provide, statistically, more immediate feedback 617 to the senders and thus allows for short-term adaptation and 618 efficient feedback-based repair mechanisms to be implemented. 620 +----------+----------------------------+-------+-------------------+ 621 | Name | Notes | Level | Mux Category | 622 +----------+----------------------------+-------+-------------------+ 623 | rtcp-fb | Since RTCP feedback | M | IDENTICAL-PER-PT | 624 | | attributes are Payload | | | 625 | | Type (PT) scoped, their | | | 626 | | values MUST be identical | | | 627 | | for a given PT across the | | | 628 | | multiplexed "m=" lines. | | | 629 | | | | | 630 +----------+----------------------------+-------+-------------------+ 632 RFC4585 Attribute Analysis 634 5.3. RFC5761 - Multiplexing RTP and RTCP 636 [RFC5761] discusses issues that arise when multiplexing RTP data 637 packets and RTP Control Protocol (RTCP) packets on a single UDP port. 638 It describes when such multiplexing is and is not appropriate, and it 639 explains how the Session Description Protocol (SDP) can be used to 640 signal multiplexed sessions. 642 +-----------+----------------------------------+-------+------------+ 643 | Name | Notes | Level | Mux | 644 | | | | Category | 645 +-----------+----------------------------------+-------+------------+ 646 | rtcp-mux | RTP and RTCP Multiplexing | M | IDENTICAL | 647 | | affects the entire RTP Session | | | 648 | | | | | 649 +-----------+----------------------------------+-------+------------+ 651 RFC5761 Attribute Analysis 653 5.4. RFC3312 - Integration of Resource Management and (SIP) 655 [RFC3312] defines a generic framework for preconditions, which are 656 extensible through IANA registration. This document also discusses 657 how network quality of service can be made a precondition for 658 establishment of sessions initiated by the Session Initiation 659 Protocol (SIP). These preconditions require that the participant 660 reserve network resources before continuing with the session. 662 +-------+-----------------------+-------+------------------+ 663 | Name | Notes | Level | Mux Category | 664 +-------+-----------------------+-------+------------------+ 665 | des | Refer to notes below | M | NOT RECOMMENDED | 666 | | | | | 667 | conf | Refer to notes below | M | NOT RECOMMENDED | 668 | | | | | 669 | curr | Refer to notes below | M | NOT RECOMMENDED | 670 | | | | | 671 +-------+-----------------------+-------+------------------+ 673 RFC3312 Attribute Analysis 675 A mismatched set of preconditions across media descriptions results 676 in Session establishment failures due to inability in meeting the 677 right resource reservations requested. 679 5.5. RFC4574 - SDP Label Attribute 681 [RFC4574] defines a new Session Description Protocol (SDP) media- 682 level attribute: "label". The "label" attribute carries a pointer to 683 a media stream in the context of an arbitrary network application 684 that uses SDP. The sender of the SDP document can attach the "label" 685 attribute to a particular media stream or streams. The application 686 can then use the provided pointer to refer to each particular media 687 stream in its context. 689 +--------+---------------+-------+--------------+ 690 | Name | Notes | Level | Mux Category | 691 +--------+---------------+-------+--------------+ 692 | label | Not Impacted | M | NORMAL | 693 | | | | | 694 +--------+---------------+-------+--------------+ 696 RFC4574 Attribute Analysis 698 5.6. RFC5432 - QoS Mechanism Selection in SDP 700 [RFC5432] defines procedures to negotiate QOS mechanisms using the 701 Session Description Protocol (SDP) offer/answer model. 703 +----------------+------------------------+-------+--------------+ 704 | Name | Notes | Level | Mux Category | 705 +----------------+------------------------+-------+--------------+ 706 | qos-mech-send | Refer to notes below | B | NORMAL | 707 | | | | | 708 | qos-mech-recv | Refer to notes below. | B | NORMAL | 709 | | | | | 710 +----------------+------------------------+-------+--------------+ 712 RFC5432 Attribute Analysis 714 A single DSCP code point per flow being multiplexed doesn't impact 715 multiplexing since QOS mechanisms are signaled/scoped per flow. For 716 scenarios that involves having different DSCP code points for packets 717 being transmitted over the same 5-tuple, issues as discussed in 718 [I.D-draft-ietf-dart-dscp-rtp] needs to be taken into consideration. 720 5.7. RFC4568 - SDP Security Descriptions 722 [RFC4568] defines a Session Description Protocol (SDP) cryptographic 723 attribute for unicast media streams. The attribute describes a 724 cryptographic key and other parameters that serve to configure 725 security for a unicast media stream in either a single message or a 726 roundtrip exchange. 728 +---------+------------------------------------+-------+------------+ 729 | Name | Notes | Level | Mux | 730 | | | | Category | 731 +---------+------------------------------------+-------+------------+ 732 | crypto | crypto attribute must be the one | M | TRANSPORT | 733 | | that corresponds to the "m=" line | | | 734 | | chosen for setting up the | | | 735 | | underlying transport flow | | | 736 | | | | | 737 +---------+------------------------------------+-------+------------+ 739 RFC4568 Attribute Analysis 741 5.8. RFC5762 - RTP over DCCP 743 The Real-time Transport Protocol (RTP) is a widely used transport for 744 real-time multimedia on IP networks. The Datagram Congestion Control 745 Protocol (DCCP) is a transport protocol that provides desirable 746 services for real-time applications. [RFC5762] specifies a mapping 747 of RTP onto DCCP, along with associated signaling, such that real- 748 time applications can make use of the services provided by DCCP. 750 +--------------------+---------------------+---------+--------------+ 751 | Name | Notes | Current | Mux Category | 752 +--------------------+---------------------+---------+--------------+ 753 | dccp-service-code | If RFC6773 is not | M | NOT | 754 | | being used in | | RECOMMENDED | 755 | | addition to | | | 756 | | RFC5762, the port | | | 757 | | in the "m=" line is | | | 758 | | a DCCP port. DCCP | | | 759 | | being a connection | | | 760 | | oriented protocol, | | | 761 | | it does not allow | | | 762 | | multiple | | | 763 | | connections on the | | | 764 | | same 5-tuple | | | 765 | | | | | 766 +--------------------+---------------------+---------+--------------+ 768 RFC5762 Attribute Analysis 770 If RFC6773 is being used in addition to RFC5762 and provided that 771 DCCP-in-UDP layer has additional demultiplexing, then it may be 772 possible to use different DCCP service codes for each DCCP flow, 773 given each uses a different DCCP port. Although doing so might 774 conflict with the media type of the "m=" line. None of this is 775 standardized yet and it wouldn't work as explained. Hence 776 multiplexing must not be performed even in this alternate scenario. 778 5.9. RFC6773 - DCCP-UDP Encapsulation 780 [RFC6773] document specifies an alternative encapsulation of the 781 Datagram Congestion Control Protocol (DCCP), referred to as DCCP-UDP. 782 This encapsulation allows DCCP to be carried through the current 783 generation of Network Address Translation (NAT) middle boxes without 784 modification of those middle boxes. 786 +------------+-------------------------------+-------+--------------+ 787 | Name | Notes | Level | Mux Category | 788 +------------+-------------------------------+-------+--------------+ 789 | dccp-port | Multiplexing must not be | M | NOT | 790 | | performed due to potential | | RECOMMENDED | 791 | | conflict between the port | | | 792 | | used for DCCP | | | 793 | | en/decapsulation and the RTP | | | 794 | | | | | 795 +------------+-------------------------------+-------+--------------+ 797 RFC6773 Attribute Analysis 799 RFC6773 is about tunneling DCCP in UDP, with the UDP port being the 800 port of the DCCP en-/de-capsulation service. This encapsulation 801 allows arbitrary DCCP packets to be encapsulated and the DCCP port 802 chosen may conflict with the port chosen for the RTP traffic. 804 For multiplexing several DCCP-in-UDP encapsulations on the same UDP 805 port, with no RTP traffic on the same port implies collapsing several 806 DCCP port spaces together. This may or may not work depending on the 807 nature of DCCP encapsulations and ports choices thus rendering it to 808 be very application dependent. 810 5.10. RFC5506 - Reduced-Size RTCP in RTP Profile 812 [RFC5506] discusses benefits and issues that arise when allowing 813 Real-time Transport Protocol (RTCP) packets to be transmitted with 814 reduced size. 816 +-------------+--------------------------------+-------+------------+ 817 | Name | Notes | Level | Mux | 818 | | | | Category | 819 +-------------+--------------------------------+-------+------------+ 820 | rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL | 821 | | entire RTP Session | | | 822 | | | | | 823 +-------------+--------------------------------+-------+------------+ 825 RFC5506 Attribute Analysis 827 5.11. RFC6787 - Media Resource Control Protocol Version 2 829 The Media Resource Control Protocol Version 2 (MRCPv2) allows client 830 hosts to control media service resources such as speech synthesizers, 831 recognizers, verifiers, and identifiers residing in servers on the 832 network. MRCPv2 is not a "stand-alone" protocol -- it relies on 833 other protocols, such as the Session Initiation Protocol (SIP), to 834 coordinate MRCPv2 clients and servers and manage sessions between 835 them, and the Session Description Protocol (SDP) to describe, 836 discover, and exchange capabilities. It also depends on SIP and SDP 837 to establish the media sessions and associated parameters between the 838 media source or sink and the media server. Once this is done, the 839 MRCPv2 exchange operates over the control session established above, 840 allowing the client to control the media processing resources on the 841 speech resource server. [RFC6787] defines attributes for this 842 purpose. 844 +-----------+---------------+-------+--------------+ 845 | Name | Notes | Level | Mux Category | 846 +-----------+---------------+-------+--------------+ 847 | resource | Not Impacted | M | NORMAL | 848 | | | | | 849 | channel | Not Impacted | M | NORMAL | 850 | | | | | 851 | cmid | Not Impacted | M | NORMAL | 852 | | | | | 853 +-----------+---------------+-------+--------------+ 855 RFC6787 Attribute Analysis 857 5.12. RFC5245 - Interactive Connectivity Establishment (ICE) 859 [RFC5245] describes a protocol for Network Address Translator(NAT) 860 traversal for UDP-based multimedia sessions established with the 861 offer/answer model. This protocol is called Interactive Connectivity 862 Establishment (ICE). ICE makes use of the Session Traversal 863 Utilities for NAT (STUN) protocol and its extension,Traversal Using 864 Relay NAT (TURN). ICE can be used by any protocol utilizing the 865 offer/answer model, such as the Session Initiation Protocol (SIP). 867 +--------------------+-------------------------+-------+------------+ 868 | Name | Notes | Level | Mux | 869 | | | | Category | 870 +--------------------+-------------------------+-------+------------+ 871 | ice-lite | Not Impacted | S | NORMAL | 872 | | | | | 873 | ice-options | Not Impacted | S | NORMAL | 874 | | | | | 875 | ice-mismatch | Not Impacted | S | NORMAL | 876 | | | | | 877 | ice-pwd | ice-pwd must be the one | B | TRANSPORT | 878 | | that corresponds to the | | | 879 | | "m=" line chosen for | | | 880 | | setting up the | | | 881 | | underlying transport | | | 882 | | flow | | | 883 | | | | | 884 | ice-ufrag | ice-ufrag must be the | B | TRANSPORT | 885 | | one that corresponds to | | | 886 | | the "m=" line chosen | | | 887 | | for setting up the | | | 888 | | underlying transport | | | 889 | | flow | | | 890 | | | | | 891 | candidate | ice candidate must be | M | TRANSPORT | 892 | | the one that | | | 893 | | corresponds to the "m=" | | | 894 | | line chosen for setting | | | 895 | | up the underlying | | | 896 | | transport flow | | | 897 | | | | | 898 | remote-candidates | ice remote candidate | M | TRANSPORT | 899 | | must be the one that | | | 900 | | corresponds to the "m=" | | | 901 | | line chosen for setting | | | 902 | | up the underlying | | | 903 | | transport flow | | | 904 | | | | | 905 +--------------------+-------------------------+-------+------------+ 907 RFC5245 Attribute Analysis 909 5.13. RFC5285 - RTP Header Extensions 911 [RFC5285] provides a general mechanism to use the header extension 912 feature of RTP (the Real-Time Transport Protocol). It provides the 913 option to use a small number of small extensions in each RTP packet, 914 where the universe of possible extensions is large and registration 915 is de-centralized. The actual extensions in use in a session are 916 signaled in the setup information for that session. 918 +---------+-------------------------------------+-------+-----------+ 919 | Name | Notes | Level | Mux | 920 | | | | Category | 921 +---------+-------------------------------------+-------+-----------+ 922 | extmap | Specific RTP extension document | B | SPECIAL | 923 | | must be referred | | | 924 | | | | | 925 +---------+-------------------------------------+-------+-----------+ 927 RFC5285 Attribute Analysis 929 5.14. RFC3605 - RTCP attribute in SDP 931 Originally, SDP assumed that RTP and RTCP were carried on consecutive 932 ports. However, this is not always true when NATs are involved. 933 [RFC3605] specifies an early mechanism to indicate the RTCP port. 935 +-------+--------------------------------------+-------+------------+ 936 | Name | Notes | Level | Mux | 937 | | | | Category | 938 +-------+--------------------------------------+-------+------------+ 939 | rtcp | Identical attribute value must be | M | IDENTICAL | 940 | | used since the RTCP port affects the | | | 941 | | entire RTP session. | | | 942 | | | | | 943 +-------+--------------------------------------+-------+------------+ 945 RFC3605 Attribute Analysis 947 5.15. RFC5576 - Source-Specific SDP Attributes 949 [RFC5576] defines a mechanism to describe RTP media sources, which 950 are identified by their synchronization source (SSRC) identifiers, in 951 SDP, to associate attributes with these sources, and to express 952 relationships among sources. It also defines several source-level 953 attributes that can be used to describe properties of media sources. 955 +----------------+----------------------+-------+-------------------+ 956 | Name | Notes | Level | Mux Category | 957 +----------------+----------------------+-------+-------------------+ 958 | ssrc | Refer to Notes below | M | NORMAL | 959 | | | | | 960 | ssrc-group | Refer to section | M | NORMAL | 961 | | Section 9 for | | | 962 | | specific analysis of | | | 963 | | the grouping | | | 964 | | semantics | | | 965 | | | | | 966 | cname | Not Impacted | SR | NORMAL | 967 | | | | | 968 | previous-ssrc | Refer to notes below | SR | NORMAL | 969 | | | | | 970 | fmtp | The attribute value | SR | IDENTICAL-PER-PT | 971 | | must be same for a | | | 972 | | given codec | | | 973 | | configuration | | | 974 | | | | | 975 +----------------+----------------------+-------+-------------------+ 977 RFC5576 Attribute Analysis 979 If SSRCs are repeated across "m=" lines being multiplexed, they must 980 all represent the same underlying RTP Source. 982 5.16. RFC7273 - RTP Clock Source Signalling 984 [RFC7273] specifies Session Description Protocol (SDP) signalling 985 that identifies timestamp reference clock sources and SDP signalling 986 that identifies the media clock sources in a multimedia session. 988 +------------+---------------+-------+--------------+ 989 | Name | Notes | Level | Mux Category | 990 +------------+---------------+-------+--------------+ 991 | ts-refclk | Not Impacted | B | NORMAL | 992 | | | | | 993 | mediaclk | Not Impacted | B | NORMAL | 994 | | | | | 995 +------------+---------------+-------+--------------+ 997 RFC7273 Attribute Analysis 999 5.17. RFC6236 - Image Attributes in SDP 1001 [RFC6236] proposes a new generic session setup attribute to make it 1002 possible to negotiate different image attributes such as image size. 1003 A possible use case is to make it possible for a low-end hand-held 1004 terminal to display video without the need to rescale the 1005 image,something that may consume large amounts of memory and 1006 processing power. The document also helps to maintain an optimal 1007 bitrate for video as only the image size that is desired by the 1008 receiver is transmitted. 1010 +------------+--------------------------+-------+-------------------+ 1011 | Name | Notes | Level | Mux Category | 1012 +------------+--------------------------+-------+-------------------+ 1013 | imageattr | The attribute value must | M | IDENTICAL-PER-PT | 1014 | | be same for a given | | | 1015 | | codec configuration | | | 1016 | | | | | 1017 +------------+--------------------------+-------+-------------------+ 1019 RFC6236 Attribute Analysis 1021 5.18. RFC7197 - Duplication Delay Attribute in SDP 1023 [RFC7197] defines an attribute to indicate the presence of temporally 1024 redundant media streams and the duplication delay in the Session 1025 Description Protocol. 1027 +--------------------+---------------+-------+--------------+ 1028 | Name | Notes | Level | Mux Category | 1029 +--------------------+---------------+-------+--------------+ 1030 | duplication-delay | Not Impacted | B | NORMAL | 1031 | | | | | 1032 +--------------------+---------------+-------+--------------+ 1034 RFC7197 Attribute Analysis 1036 5.19. RFC7266 - RTCP XR Blocks for MOS Metric Reporting 1038 [RFC7266] defines an RTP Control Protocol (RTCP) Extended Report (XR) 1039 Block including two new segment types and associated Session 1040 Description Protocol (SDP) parameters that allow the reporting of 1041 mean opinion score (MOS) Metrics for use in a range of RTP 1042 applications. 1044 +-------------+---------------+-------+--------------+ 1045 | Name | Notes | Level | Mux Category | 1046 +-------------+---------------+-------+--------------+ 1047 | calgextmap | Not Impacted | B | NORMAL | 1048 | | | | | 1049 +-------------+---------------+-------+--------------+ 1051 RFC7266 Attribute Analysis 1053 5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions 1055 [RFC6285] describes a method using the existing RTP and RTP Control 1056 Protocol (RTCP) machinery that reduces the acquisition delay. In 1057 this method, an auxiliary unicast RTP session carrying the Reference 1058 Information to the receiver precedes or accompanies the multicast 1059 stream. This unicast RTP flow can be transmitted at a faster than 1060 natural bitrate to further accelerate the acquisition. The 1061 motivating use case for this capability is multicast applications 1062 that carry real-time compressed audio and video. 1064 +---------------+-------------------+-------+------------------+ 1065 | Name | Notes | Level | Mux Category | 1066 +---------------+-------------------+-------+------------------+ 1067 | rams-updates | Not recommended | M | NOT RECOMMENDED | 1068 | | | | | 1069 +---------------+-------------------+-------+------------------+ 1071 RFC6285 Attribute Analysis 1073 5.21. RFC6230 - Media Control Channel Framework 1075 [RFC6230] describes a framework and protocol for application 1076 deployment where the application programming logic and media 1077 processing are distributed. This implies that application 1078 programming logic can seamlessly gain access to appropriate resources 1079 that are not co-located on the same physical network entity. The 1080 framework uses the Session Initiation Protocol (SIP) to establish an 1081 application-level control mechanism between application servers and 1082 associated external servers such as media servers. 1084 +---------+---------------+-------+--------------+ 1085 | Name | Notes | Level | Mux Category | 1086 +---------+---------------+-------+--------------+ 1087 | cfw-id | Not Impacted | M | NORMAL | 1088 | | | | | 1089 +---------+---------------+-------+--------------+ 1091 RFC6230 Attribute Analysis 1093 5.22. RFC6364 - SDP Elements for FEC Framework 1095 [RFC6364] specifies the use of the Session Description Protocol (SDP) 1096 to describe the parameters required to signal the Forward Error 1097 Correction (FEC) Framework Configuration Information between the 1098 sender(s) and receiver(s). This document also provides examples that 1099 show the semantics for grouping multiple source and repair flows 1100 together for the applications that simultaneously use multiple 1101 instances of the FEC Framework. 1103 +------------------+-----------------------------+-------+----------+ 1104 | Name | Notes | Level | Mux | 1105 | | | | Category | 1106 +------------------+-----------------------------+-------+----------+ 1107 | fec-source-flow | Specific FEC scheme | M | SPECIAL | 1108 | | document needs to be | | | 1109 | | referred | | | 1110 | | | | | 1111 | fec-repair-flow | Specific FEC scheme | M | SPECIAL | 1112 | | document needs to be | | | 1113 | | referred | | | 1114 | | | | | 1115 | repair-window | Specific FEC scheme | M | SPECIAL | 1116 | | document needs to be | | | 1117 | | referred | | | 1118 | | | | | 1119 +------------------+-----------------------------+-------+----------+ 1121 RFC6364 Attribute Analysis 1123 5.23. RFC4796 - Content Attribute 1125 [RFC4796] defines a new Session Description Protocol (SDP) media- 1126 level attribute, 'content'. The 'content' attribute defines the 1127 content of the media stream to a more detailed level than the media 1128 description line. The sender of an SDP session description can 1129 attach the 'content' attribute to one or more media streams. The 1130 receiving application can then treat each media stream differently 1131 (e.g., show it on a big or small screen) based on its content. 1133 +----------+---------------+-------+--------------+ 1134 | Name | Notes | Level | Mux Category | 1135 +----------+---------------+-------+--------------+ 1136 | content | Not Impacted | M | NORMAL | 1137 | | | | | 1138 +----------+---------------+-------+--------------+ 1140 RFC4796 Attribute Analysis 1142 5.24. RFC3407 - SDP Simple Capability Declaration 1144 [RFC3407] defines a set of Session Description Protocol (SDP) 1145 attributes that enables SDP to provide a minimal and backwards 1146 compatible capability declaration mechanism. 1148 +----------+------------------------+-------+--------------+ 1149 | Name | Notes | Level | Mux Category | 1150 +----------+------------------------+-------+--------------+ 1151 | sqn | Not Impacted | B | NORMAL | 1152 | | | | | 1153 | cdsc | Not Impacted. | B | NORMAL | 1154 | | | | | 1155 | cpar | Refer to Section 14 | B | INHERIT | 1156 | | | | | 1157 | cparmin | Refer to notes below | B | SPECIAL | 1158 | | | | | 1159 | cparmax | Refer to notes below | B | SPECIAL | 1160 | | | | | 1161 +----------+------------------------+-------+--------------+ 1163 RFC3407 Attribute Analysis 1165 Since the attributes (a=cparmin and a=cparmax) define minimum and 1166 maximum numerical values associated with the attributes described in 1167 a=cpar, it is recommended to consult the document defining the 1168 attribute. 1170 5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions 1172 [RFC6284] presents a port mapping solution that allows RTP receivers 1173 to choose their own ports for an auxiliary unicast session in RTP 1174 applications using both unicast and multicast services. The solution 1175 provides protection against denial-of-service or packet amplification 1176 attacks that could be used to cause one or more RTP packets to be 1177 sent to a victim client. 1179 +------------------+-------------------------+-------+--------------+ 1180 | Name | Notes | Level | Mux Category | 1181 +------------------+-------------------------+-------+--------------+ 1182 | portmapping-req | Not recommended, if | M | NOT | 1183 | | port mapping is | | RECOMMENDED | 1184 | | required by the | | | 1185 | | application | | | 1186 | | | | | 1187 +------------------+-------------------------+-------+--------------+ 1189 RFC6284 Attribute Analysis 1191 5.26. RFC6714 - MSRP-CEMA 1193 [RFC6714] defines a Message Session Relay Protocol (MSRP) extension, 1194 Connection Establishment for Media Anchoring (CEMA). Support of this 1195 extension is OPTIONAL. The extension allows middle boxes to anchor 1196 the MSRP connection, without the need for middle boxes to modify the 1197 MSRP messages; thus, it also enables secure end-to-end MSRP 1198 communication in networks where such middle boxes are deployed. This 1199 document also defines a Session Description Protocol (SDP) attribute, 1200 'msrp-cema', that MSRP endpoints use to indicate support of the CEMA 1201 extension. 1203 +------------+---------------+-------+--------------+ 1204 | Name | Notes | Level | Mux Category | 1205 +------------+---------------+-------+--------------+ 1206 | msrp-cema | Not Impacted | M | NORMAL | 1207 | | | | | 1208 +------------+---------------+-------+--------------+ 1210 RFC6714 Attribute Analysis 1212 5.27. RFC4583 - SDP Format for BFCP Streams 1214 [RFC4583] document specifies how to describe Binary Floor Control 1215 Protocol (BFCP) streams in Session Description Protocol (SDP) 1216 descriptions. User agents using the offer/answer model to establish 1217 BFCP streams use this format in their offers and answers. 1219 +------------+---------------------------------+-------+------------+ 1220 | Name | Notes | Level | Mux | 1221 | | | | Category | 1222 +------------+---------------------------------+-------+------------+ 1223 | floorctrl | must be repeated across all the | M | IDENTICAL | 1224 | | multiplexed "m=" lines | | | 1225 | | | | | 1226 | confid | Not Impacted | M | NORMAL | 1227 | | | | | 1228 | userid | Not Impacted | M | NORMAL | 1229 | | | | | 1230 | floorid | The floorid MUST be globally | M | NORMAL | 1231 | | unique | | | 1232 | | | | | 1233 +------------+---------------------------------+-------+------------+ 1235 RFC4583 Attribute Analysis 1237 5.28. RFC5547 - SDP Offer/Answer for File Transfer 1239 [RFC5547] provides a mechanism to negotiate the transfer of one or 1240 more files between two endpoints by using the Session Description 1241 Protocol (SDP) offer/answer model specified in [RFC3264]. 1243 +----------------------+---------------+-------+--------------+ 1244 | Name | Notes | Level | Mux Category | 1245 +----------------------+---------------+-------+--------------+ 1246 | file-selector | Not Impacted | M | NORMAL | 1247 | | | | | 1248 | file-transfer-id | Not Impacted | M | NORMAL | 1249 | | | | | 1250 | file-disposition | Not Impacted | M | NORMAL | 1251 | | | | | 1252 | file-date | Not Impacted | M | NORMAL | 1253 | | | | | 1254 | file-iconfile-range | Not Impacted | M | NORMAL | 1255 | | | | | 1256 +----------------------+---------------+-------+--------------+ 1258 RFC5547 Attribute Analysis 1260 5.29. RFC6849 - SDP and RTP Media Loopback Extension 1262 [RFC6849] adds new SDP media types and attributes, which enable 1263 establishment of media sessions where the media is looped back to the 1264 transmitter. Such media sessions will serve as monitoring and 1265 troubleshooting tools by providing the means for measurement of more 1266 advanced VoIP, Real-time Text, and Video over IP performance metrics. 1268 +---------------------------+----------------+-------+--------------+ 1269 | Name | Notes | Level | Mux Category | 1270 +---------------------------+----------------+-------+--------------+ 1271 | loopback rtp-pkt-loopback | Not Impacted | M | NORMAL | 1272 | | | | | 1273 | loopback rtp-media- | Not Impacted | M | NORMAL | 1274 | loopback | | | | 1275 | | | | | 1276 | loopback-source | Not Impacted | M | NORMAL | 1277 | | | | | 1278 | loopback-mirror | Not Impacted | M | NORMAL | 1279 | | | | | 1280 +---------------------------+----------------+-------+--------------+ 1282 RFC6849 Analysis 1284 5.30. RFC5760 - RTCP with Unicast Feedback 1286 [RFC5760] specifies an extension to the Real-time Transport Control 1287 Protocol (RTCP) to use unicast feedback to a multicast sender. The 1288 proposed extension is useful for single-source multicast sessions 1289 such as Source-Specific Multicast (SSM) communication where the 1290 traditional model of many-to-many group communication is either not 1291 available or not desired. 1293 +---------------+------------------------------+-------+------------+ 1294 | Name | Notes | Level | Mux | 1295 | | | | Category | 1296 +---------------+------------------------------+-------+------------+ 1297 | rtcp-unicast | The attribute must be | M | IDENTICAL | 1298 | | reported across all "m=" | | | 1299 | | lines multiplexed | | | 1300 | | | | | 1301 +---------------+------------------------------+-------+------------+ 1303 RFC5760 Attribute Analysis 1305 5.31. RFC3611 - RTCP XR 1307 [RFC3611] defines the Extended Report (XR) packet type for the RTP 1308 Control Protocol (RTCP), and defines how the use of XR packets can be 1309 signaled by an application if it employs the Session Description 1310 Protocol (SDP). 1312 +----------+---------------+-------+--------------+ 1313 | Name | Notes | Level | Mux Category | 1314 +----------+---------------+-------+--------------+ 1315 | rtcp-xr | Not Impacted | B | NORMAL | 1316 | | | | | 1317 +----------+---------------+-------+--------------+ 1319 RFC3611 Attribute Analysis 1321 5.32. RFC5939 - SDP Capability Negotiation 1323 [RFC5939] defines a general SDP Capability Negotiation framework. It 1324 also specifies how to provide attributes and transport protocols as 1325 capabilities and negotiate them using the framework. Extensions for 1326 other types of capabilities (e.g., media types and media formats) may 1327 be provided in other documents. 1329 +---------+-------------------------------+-------+--------------+ 1330 | Name | Notes | Level | Mux Category | 1331 +---------+-------------------------------+-------+--------------+ 1332 | pcfg | Refer to Section Section 14 | M | SPECIAL | 1333 | | | | | 1334 | acfg | Refer to Section Section 14 | M | SPECIAL | 1335 | | | | | 1336 | csup | Not Impacted | B | NORMAL | 1337 | | | | | 1338 | creq | Not Impacted | B | NORMAL | 1339 | | | | | 1340 | acap | Refer to section Section 14 | B | INHERIT | 1341 | | | | | 1342 | tcap | Refer to section Section 14 | B | INHERIT | 1343 | | | | | 1344 | cap-v0 | Not Impacted | B | NORMAL | 1345 | | | | | 1346 +---------+-------------------------------+-------+--------------+ 1348 RFC5939 Attribute Analysis 1350 5.33. RFC6871- SDP Media Capabilities Negotiation 1352 Session Description Protocol (SDP) capability negotiation provides a 1353 general framework for indicating and negotiating capabilities in SDP. 1354 The base framework defines only capabilities for negotiating 1355 transport protocols and attributes. [RFC6871] extends the framework 1356 by defining media capabilities that can be used to negotiate media 1357 types and their associated parameters. 1359 +---------+-----------------------------+-------+-------------------+ 1360 | Name | Notes | Level | Mux Category | 1361 +---------+-----------------------------+-------+-------------------+ 1362 | rmcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT | 1363 | | | | | 1364 | omcap | Not Impacted | B | NORMAL | 1365 | | | | | 1366 | mfcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT | 1367 | | | | | 1368 | mscap | Refer to Section Section 14 | B | INHERIT | 1369 | | | | | 1370 | lcfg | Refer to Section Section 14 | B | SPECIAL | 1371 | | | | | 1372 | sescap | Refer to notes below | S | NOT RECOMMENDED | 1373 | | | | | 1374 | med-v0 | Not Impacted | S | NORMAL | 1375 | | | | | 1376 +---------+-----------------------------+-------+-------------------+ 1378 RFC6871 - Attribute Analysis 1380 The "sescap" attribute is NOT RECOMMENDED for use with multiplexing. 1381 The reason is that it requires the use of unique configuration 1382 numbers across the entire SDP (per [RFC6871]) as opposed to within a 1383 media description only (per [RFC5939]). As described in Section 14, 1384 the use of identical configuration numbers between multiplexed 1385 (bundled) media descriptions is the default way of indicating 1386 compatible configurations in a bundle. 1388 5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP 1390 [RFC7006] extends the SDP capability negotiation framework to allow 1391 endpoints to negotiate three additional SDP capabilities. In 1392 particular, this memo provides a mechanism to negotiate bandwidth 1393 ("b=" line), connection data ("c=" line), and session or media titles 1394 ("i=" line for each session or media). 1396 +----------+-----------------------------------+-------+------------+ 1397 | Name | Notes | Level | Mux | 1398 | | | | Category | 1399 +----------+-----------------------------------+-------+------------+ 1400 | bcap | Inherit the category SUM as | B | INHERIT | 1401 | | applicable to b= attribute | | | 1402 | | | | | 1403 | bcap-v0 | Not Impacted | B | NORMAL | 1404 | | | | | 1405 | ccap | The connection address type must | B | IDENTICAL | 1406 | | be identical across all the | | | 1407 | | multiplexed "m=" lines | | | 1408 | | | | | 1409 | ccap-v0 | Not Impacted | B | NORMAL | 1410 | | | | | 1411 | icap | Not Impacted | B | NORMAL | 1412 | | | | | 1413 | icap-v0 | Not Impacted | B | NORMAL | 1414 | | | | | 1415 +----------+-----------------------------------+-------+------------+ 1417 RFC7006 - Attribute Analysis 1419 5.35. RFC4567 - Key Management Extensions for SDP and RTSP 1421 [RFC4567] defines general extensions for Session Description Protocol 1422 (SDP) and Real Time Streaming Protocol (RTSP) to carry messages, as 1423 specified by a key management protocol, in order to secure the media. 1424 These extensions are presented as a framework, to be used by one or 1425 more key management protocols. As such, their use is meaningful only 1426 when complemented by an appropriate key management protocol. 1428 +-----------+----------------------------------+-------+------------+ 1429 | Name | Notes | Level | Mux | 1430 | | | | Category | 1431 +-----------+----------------------------------+-------+------------+ 1432 | key-mgmt | Key management protocol must be | B | IDENTICAL | 1433 | | identical across all the "m=" | | | 1434 | | lines | | | 1435 | | | | | 1436 | mikey | Key management protocol must be | B | IDENTICAL | 1437 | | identical across all the "m=" | | | 1438 | | lines | | | 1439 | | | | | 1440 +-----------+----------------------------------+-------+------------+ 1442 RFC4567 Attribute Analysis 1444 5.36. RFC4572 - Comedia over TLS in SDP 1446 [RFC4572] specifies how to establish secure connection-oriented media 1447 transport sessions over the Transport Layer Security (TLS) protocol 1448 using the Session Description Protocol (SDP). It defines a new SDP 1449 protocol identifier, 'TCP/TLS'. It also defines the syntax and 1450 semantics for an SDP 'fingerprint' attribute that identifies the 1451 certificate that will be presented for the TLS session. This 1452 mechanism allows media transport over TLS connections to be 1453 established securely, so long as the integrity of session 1454 descriptions is assured. 1456 +--------------+-------------------------------+-------+------------+ 1457 | Name | Notes | Level | Mux | 1458 | | | | Category | 1459 +--------------+-------------------------------+-------+------------+ 1460 | fingerprint | fingerprint value from the | B | TRANSPORT | 1461 | | "m=" line defining the | | | 1462 | | underlying transport is | | | 1463 | | chosen | | | 1464 | | | | | 1465 +--------------+-------------------------------+-------+------------+ 1467 RFC4572 Attribute Analysis 1469 5.37. RFC4570 - SDP Source Filters 1471 [RFC4570] describes how to adapt the Session Description Protocol 1472 (SDP) to express one or more source addresses as a source filter for 1473 one or more destination "connection" addresses. It defines the 1474 syntax and semantics for an SDP "source-filter" attribute that may 1475 reference either IPv4 or IPv6 address(es) as either an inclusive or 1476 exclusive source list for either multicast or unicast destinations. 1477 In particular, an inclusive source-filter can be used to specify a 1478 Source-Specific Multicast (SSM) session. 1480 +----------------+-----------------------------+-------+------------+ 1481 | Name | Notes | Level | Mux | 1482 | | | | Category | 1483 +----------------+-----------------------------+-------+------------+ 1484 | source-filter | The attribute must be | B | IDENTICAL | 1485 | | repeated across all "m=" | | | 1486 | | lines multiplexed | | | 1487 | | | | | 1488 +----------------+-----------------------------+-------+------------+ 1490 RFC4570 Attribute Analysis 1492 5.38. RFC6128 - RTCP Port for Multicast Sessions 1494 The Session Description Protocol (SDP) has an attribute that allows 1495 RTP applications to specify an address and a port associated with the 1496 RTP Control Protocol (RTCP) traffic. In RTP-based source-specific 1497 multicast (SSM) sessions, the same attribute is used to designate the 1498 address and the RTCP port of the Feedback Target in the SDP 1499 description. However, the RTCP port associated with the SSM session 1500 itself cannot be specified by the same attribute to avoid ambiguity, 1501 and thus, is required to be derived from the "m=" line of the media 1502 description. Deriving the RTCP port from the "m=" line imposes an 1503 unnecessary restriction. [RFC6128] removes this restriction by 1504 introducing a new SDP attribute. 1506 +-----------------+----------------------------+-------+------------+ 1507 | Name | Notes | Level | Mux | 1508 | | | | Category | 1509 +-----------------+----------------------------+-------+------------+ 1510 | multicast-rtcp | Multicast RTCP port must | B | IDENTICAL | 1511 | | be identical across all | | | 1512 | | the "m=" lines | | | 1513 | | | | | 1514 +-----------------+----------------------------+-------+------------+ 1516 RFC6128 Attribute Analysis 1518 5.39. RFC6189 - ZRTP 1520 [RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman 1521 exchange to agree on a session key and parameters for establishing 1522 unicast Secure Real-time Transport Protocol (SRTP) sessions for Voice 1523 over IP (VoIP) applications. 1525 +------------+-------------------------------+-------+--------------+ 1526 | Name | Notes | Level | Mux Category | 1527 +------------+-------------------------------+-------+--------------+ 1528 | zrtp-hash | Complicates if all the "m=" | M | NOT | 1529 | | lines are not authenticated | | RECOMMENDED | 1530 | | | | | 1531 +------------+-------------------------------+-------+--------------+ 1533 RFC6189 Attribute Analysis 1535 5.40. RFC4145 - Connection-Oriented Media 1537 [RFC4145] describes how to express media transport over TCP using the 1538 Session Description Protocol (SDP). It defines the SDP 'TCP' 1539 protocol identifier, the SDP 'setup' attribute, which describes the 1540 connection setup procedure, and the SDP 'connection' attribute, which 1541 handles connection reestablishment. 1543 +-------------+--------------------------------+-------+------------+ 1544 | Name | Notes | Level | Mux | 1545 | | | | Category | 1546 +-------------+--------------------------------+-------+------------+ 1547 | setup | must be identical across all | B | IDENTICAL | 1548 | | "m=" lines | | | 1549 | | | | | 1550 | connection | must be identical across all | B | IDENTICAL | 1551 | | "m=" lines | | | 1552 | | | | | 1553 +-------------+--------------------------------+-------+------------+ 1555 RFC4145 Attribute Analysis 1557 5.41. RFC6947 - The SDP ALTC Attribute 1559 [RFC6947] proposes a mechanism that allows the same SDP offer to 1560 carry multiple IP addresses of different address families (e.g., IPv4 1561 and IPv6). The proposed attribute, the "altc" attribute, solves the 1562 backward-compatibility problem that plagued Alternative Network 1563 Address Types (ANAT) due to their syntax. 1565 +-------+--------------------------------------+-------+------------+ 1566 | Name | Notes | Level | Mux | 1567 | | | | Category | 1568 +-------+--------------------------------------+-------+------------+ 1569 | altc | The IP Address and port must be the | M | TRANSPORT | 1570 | | one that corresponds to the "m=" | | | 1571 | | line chosen for setting up the | | | 1572 | | underlying transport flow | | | 1573 | | | | | 1574 +-------+--------------------------------------+-------+------------+ 1576 RFC6947 Attribute Analysis 1578 5.42. RFC7195 - SDP Extension for Circuit Switched Bearers in PSTN 1580 [RFC7195] describes use cases, requirements, and protocol extensions 1581 for using the Session Description Protocol (SDP) offer/answer model 1582 for establishing audio and video media streams over circuit-switched 1583 bearers in the Public Switched Telephone Network (PSTN). 1585 +--------------------------+---------------+-------+--------------+ 1586 | Name | Notes | Level | Mux Category | 1587 +--------------------------+---------------+-------+--------------+ 1588 | cs-correlation:callerid | Not Impacted | M | NORMAL | 1589 | | | | | 1590 | cs-correlation:uuie | Not Impacted | M | NORMAL | 1591 | | | | | 1592 | cs-correlation:dtmf | Not Impacted | M | NORMAL | 1593 | | | | | 1594 | cs-correlation:external | Not Impacted | M | NORMAL | 1595 | | | | | 1596 +--------------------------+---------------+-------+--------------+ 1598 RFC7195 Attribute Analysis 1600 5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP) 1602 [RFC7272] defines a new RTP Control Protocol (RTCP) Packet Type and 1603 an RTCP Extended Report (XR) Block Type to be used for achieving 1604 Inter-Destination Media Synchronization (IDMS). 1606 +------------+---------------+-------+--------------+ 1607 | Name | Notes | Level | Mux Category | 1608 +------------+---------------+-------+--------------+ 1609 | rtcp-idms | Not Impacted | M | NORMAL | 1610 | | | | | 1611 +------------+---------------+-------+--------------+ 1613 RFC7272 Attribute Analysis 1615 5.44. RFC5159 - OMA BCAST SDP Attributes 1617 [RFC5159] provides descriptions of Session Description Protocol (SDP) 1618 attributes used by the Open Mobile Alliance's Broadcast Service and 1619 Content Protection specification. 1621 +---------------------+---------------+-------+--------------+ 1622 | Name | Notes | Level | Mux Category | 1623 +---------------------+---------------+-------+--------------+ 1624 | bcastversion | Not Impacted | S | NORMAL | 1625 | | | | | 1626 | stkmstream | Not Impacted | B | NORMAL | 1627 | | | | | 1628 | SRTPAuthentication | Not Impacted | M | NORMAL | 1629 | | | | | 1630 | SRTPROCTxRate | Not Impacted | M | NORMAL | 1631 | | | | | 1632 +---------------------+---------------+-------+--------------+ 1634 RFC5159 Attribute Analysis 1636 5.45. RFC6193 - Media Description for IKE in SDP 1638 [RFC6193] specifies how to establish a media session that represents 1639 a virtual private network using the Session Initiation Protocol for 1640 the purpose of on-demand media/application sharing between peers. It 1641 extends the protocol identifier of the Session Description Protocol 1642 (SDP) so that it can negotiate use of the Internet Key Exchange 1643 Protocol (IKE) for media sessions in the SDP offer/answer model. 1645 +-------------------+--------------------------+-------+------------+ 1646 | Name | Notes | Level | Mux | 1647 | | | | Category | 1648 +-------------------+--------------------------+-------+------------+ 1649 | ike-setup | Attribute must be | B | IDENTICAL | 1650 | | identical across all the | | | 1651 | | "m=" lines | | | 1652 | | | | | 1653 | psk-fingerprint | Attribute must be | B | IDENTICAL | 1654 | | identical across all the | | | 1655 | | "m=" lines | | | 1656 | | | | | 1657 | ike-esp | Attribute must be | B | IDENTICAL | 1658 | | identical across all the | | | 1659 | | "m=" lines | | | 1660 | | | | | 1661 | ike-esp-udpencap | Attribute must be | B | IDENTICAL | 1662 | | identical across all the | | | 1663 | | "m=" lines | | | 1664 | | | | | 1665 +-------------------+--------------------------+-------+------------+ 1667 RFC6193 Attribute Analysis 1669 With the above SDP constraints, a session multiplexed with multiple 1670 "m=" lines will use only one IPSec association for all of the "m=" 1671 lines. 1673 5.46. RFC2326 - Real Time Streaming Protocol 1675 The Real Time Streaming Protocol, or RTSP, is an application-level 1676 protocol for control over the delivery of data with real-time 1677 properties. RTSP provides an extensible framework to enable 1678 controlled, on-demand delivery of real-time data, such as audio and 1679 video. 1681 +----------+---------------------------------+-------+--------------+ 1682 | Name | Notes | Level | Mux Category | 1683 +----------+---------------------------------+-------+--------------+ 1684 | etag | RTSP is not supported for RTP | B | NOT | 1685 | | Stream multiplexing | | RECOMMENDED | 1686 | | | | | 1687 | range | RTSP is not supported for RTP | B | NOT | 1688 | | Stream multiplexing | | RECOMMENDED | 1689 | | | | | 1690 | control | RTSP is not supported for RTP | B | NOT | 1691 | | Stream multiplexing | | RECOMMENDED | 1692 | | | | | 1693 | mtag | RTSP is not supported for RTP | B | NOT | 1694 | | Stream multiplexing | | RECOMMENDED | 1695 | | | | | 1696 +----------+---------------------------------+-------+--------------+ 1698 RFC2326 Attribute Analysis 1700 [RFC2326] defines SDP attributes that are applicable in the 1701 declarative usage of SDP alone. For purposes of this document, only 1702 the Offer/Answer usage of SDP is considered as mandated by 1703 [I-D.ietf-mmusic-sdp-bundle-negotiation]. 1705 5.47. RFC6064 - SDP and RTSP Extensions for 3GPP 1707 The Packet-switched Streaming Service (PSS) and the Multimedia 1708 Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session 1709 Description Protocol (SDP) and Real Time Streaming Protocol (RTSP) 1710 with some extensions. [RFC6064] provides information about these 1711 extensions and registers the RTSP and SDP extensions with IANA. 1713 +-------------------------------+------------+-------+--------------+ 1714 | Name | Notes | Level | Mux Category | 1715 +-------------------------------+------------+-------+--------------+ 1716 | X-predecbufsize | Refer to | M | NOT | 1717 | | notes | | RECOMMENDED | 1718 | | below | | | 1719 | | | | | 1720 | X-initpredecbufperiod | Refer to | M | NOT | 1721 | | notes | | RECOMMENDED | 1722 | | below | | | 1723 | | | | | 1724 | X-initpostdecbufperiod | Refer to | M | NOT | 1725 | | notes | | RECOMMENDED | 1726 | | below | | | 1727 | | | | | 1728 | X-decbyterate | Refer to | M | NOT | 1729 | | notes | | RECOMMENDED | 1730 | | below | | | 1731 | | | | | 1732 | 3gpp-videopostdecbufsize | Refer to | M | NOT | 1733 | | notes | | RECOMMENDED | 1734 | | below | | | 1735 | | | | | 1736 | framesize | Refer to | M | NOT | 1737 | | notes | | RECOMMENDED | 1738 | | below | | | 1739 | | | | | 1740 | 3GPP-Integrity-Key | Refer to | S | NOT | 1741 | | notes | | RECOMMENDED | 1742 | | below | | | 1743 | | | | | 1744 | 3GPP-SDP-Auth | Refer to | S | NOT | 1745 | | notes | | RECOMMENDED | 1746 | | below | | | 1747 | | | | | 1748 | 3GPP-SRTP-Config | Refer to | M | NOT | 1749 | | notes | | RECOMMENDED | 1750 | | below | | | 1751 | | | | | 1752 | alt | Refer to | M | NOT | 1753 | | notes | | RECOMMENDED | 1754 | | below | | | 1755 | | | | | 1756 | alt-default-id | Refer to | M | NOT | 1757 | | notes | | RECOMMENDED | 1758 | | below | | | 1759 | | | | | 1760 | alt-group | Refer to | M | NOT | 1761 | | notes | | RECOMMENDED | 1762 | | below | | | 1763 | | | | | 1764 | 3GPP-Adaptation-Support | Refer to | M | NOT | 1765 | | notes | | RECOMMENDED | 1766 | | below | | | 1767 | | | | | 1768 | 3GPP-Asset-Information | Refer to | B | NOT | 1769 | | notes | | RECOMMENDED | 1770 | | below | | | 1771 | | | | | 1772 | mbms-mode | Refer to | B | NOT | 1773 | | notes | | RECOMMENDED | 1774 | | below | | | 1775 | | | | | 1776 | mbms-flowid | Refer to | M | NOT | 1777 | | notes | | RECOMMENDED | 1778 | | below | | | 1779 | | | | | 1780 | mbms-repair | Refer to | B | NOT | 1781 | | notes | | RECOMMENDED | 1782 | | below | | | 1783 | | | | | 1784 | 3GPP-QoE-Metrics | Refer to | M | NOT | 1785 | | notes | | RECOMMENDED | 1786 | | below | | | 1787 | | | | | 1788 | 3GPP-QoE-Metrics:Corruption | Refer to | M | NOT | 1789 | duration | notes | | RECOMMENDED | 1790 | | below | | | 1791 | | | | | 1792 | 3GPP-QoE-Metrics:Rebuffering | Refer to | M | NOT | 1793 | duration | notes | | RECOMMENDED | 1794 | | below | | | 1795 | | | | | 1796 | 3GPP-QoE-Metrics:Initial | Refer to | M | NOT | 1797 | buffering duration | notes | | RECOMMENDED | 1798 | | below | | | 1799 | | | | | 1800 | 3GPP-QoE-Metrics:Successive | Refer to | M | NOT | 1801 | loss of RTP packets | notes | | RECOMMENDED | 1802 | | below | | | 1803 | | | | | 1804 | 3GPP-QoE-Metrics:Frame rate | Refer to | M | NOT | 1805 | deviation | notes | | RECOMMENDED | 1806 | | below | | | 1807 | | | | | 1808 | 3GPP-QoE-Metrics:Jitter | Refer to | M | NOT | 1809 | duration | notes | | RECOMMENDED | 1810 | | below | | | 1811 | | | | | 1812 | 3GPP-QoE-Metrics:Content | Refer to | B | NOT | 1813 | Switch Time | notes | | RECOMMENDED | 1814 | | below | | | 1815 | | | | | 1816 | 3GPP-QoE-Metrics:Average | Refer to | M | NOT | 1817 | Codec Bitrate | notes | | RECOMMENDED | 1818 | | below | | | 1819 | | | | | 1820 | 3GPP-QoE-Metrics:Codec | Refer to | M | NOT | 1821 | Information | notes | | RECOMMENDED | 1822 | | below | | | 1823 | | | | | 1824 | 3GPP-QoE-Metrics:Buffer | Refer to | M | NOT | 1825 | Status | notes | | RECOMMENDED | 1826 | | below | | | 1827 | | | | | 1828 +-------------------------------+------------+-------+--------------+ 1830 RFC6064 Attribute Analysis 1832 [RFC6064] defines SDP attributes that are applicable in the 1833 declarative usage of SDP alone. For purposes of this document, only 1834 the Offer/Answer usage of SDP is considered as mandated by 1835 [I-D.ietf-mmusic-sdp-bundle-negotiation]. 1837 5.48. RFC3108 - ATM SDP 1839 [RFC3108] describes conventions for using the Session Description 1840 Protocol (SDP) described for controlling ATM Bearer Connections, and 1841 any associated ATM Adaptation Layer (AAL). 1843 +------------------------+------------------+-------+---------------+ 1844 | Name | Notes | Level | Mux Category | 1845 +------------------------+------------------+-------+---------------+ 1846 | aalType | Refer to notes | B | NOT | 1847 | | below | | RECOMMENDED | 1848 | eecid | Refer to notes | B | NOT | 1849 | | below | | RECOMMENDED | 1850 | capability | Refer to notes | B | NOT | 1851 | | below | | RECOMMENDED | 1852 | qosClass | Refer to notes | B | NOT | 1853 | | below | | RECOMMENDED | 1854 | bcob | Refer to notes | B | NOT | 1855 | | below | | RECOMMENDED | 1856 | stc | Refer to notes | B | NOT | 1857 | | below | | RECOMMENDED | 1858 | upcc | Refer to notes | B | NOT | 1859 | | below | | RECOMMENDED | 1860 | atmQOSparms | Refer to notes | B | NOT | 1861 | | below | | RECOMMENDED | 1862 | atmTrfcDesc | Refer to notes | B | NOT | 1863 | | below | | RECOMMENDED | 1864 | abrParms | Refer to notes | B | NOT | 1865 | | below | | RECOMMENDED | 1866 | abrSetup | Refer to notes | B | NOT | 1867 | | below | | RECOMMENDED | 1868 | bearerType | Refer to notes | B | NOT | 1869 | | below | | RECOMMENDED | 1870 | lij | Refer to notes | B | NOT | 1871 | | below | | RECOMMENDED | 1872 | anycast | Refer to notes | B | NOT | 1873 | | below | | RECOMMENDED | 1874 | cache | Refer to notes | B | NOT | 1875 | | below | | RECOMMENDED | 1876 | bearerSigIE | Refer to notes | B | NOT | 1877 | | below | | RECOMMENDED | 1878 | aalApp | Refer to notes | B | NOT | 1879 | | below | | RECOMMENDED | 1880 | cbrRate | Refer to notes | B | NOT | 1881 | | below | | RECOMMENDED | 1882 | sbc | Refer to notes | B | NOT | 1883 | | below | | RECOMMENDED | 1884 | clkrec | Refer to notes | B | NOT | 1885 | | below | | RECOMMENDED | 1886 | fec | Refer to notes | B | NOT | 1887 | | below | | RECOMMENDED | 1888 | prtfl | Refer to notes | B | NOT | 1889 | | below | | RECOMMENDED | 1890 | structure | Refer to notes | B | NOT | 1891 | | below | | RECOMMENDED | 1892 | cpsSDUsize | Refer to notes | B | NOT | 1893 | | below | | RECOMMENDED | 1894 | aal2CPS | Refer to notes | B | NOT | 1895 | | below | | RECOMMENDED | 1896 | aal2CPSSDUrate | Refer to notes | B | NOT | 1897 | | below | | RECOMMENDED | 1898 | aal2sscs3661unassured | Refer to notes | B | NOT | 1899 | | below | | RECOMMENDED | 1900 | aal2sscs3661assured | Refer to notes | B | NOT | 1901 | | below | | RECOMMENDED | 1902 | aal2sscs3662 | Refer to notes | B | NOT | 1903 | | below | | RECOMMENDED | 1904 | aal5sscop | Refer to notes | B | NOT | 1905 | | below | | RECOMMENDED | 1906 | atmmap | Refer to notes | B | NOT | 1907 | | below | | RECOMMENDED | 1908 | silenceSupp | Refer to notes | B | NOT | 1909 | | below | | RECOMMENDED | 1910 | ecan | Refer to notes | B | NOT | 1911 | | below | | RECOMMENDED | 1912 | gc | Refer to notes | B | NOT | 1913 | | below | | RECOMMENDED | 1914 | profileDesc | Refer to notes | B | NOT | 1915 | | below | | RECOMMENDED | 1916 | vsel | Refer to notes | B | NOT | 1917 | | below | | RECOMMENDED | 1918 | dsel | Refer to notes | B | NOT | 1919 | | below | | RECOMMENDED | 1920 | fsel | Refer to notes | B | NOT | 1921 | | below | | RECOMMENDED | 1922 | onewaySel | Refer to notes | B | NOT | 1923 | | below | | RECOMMENDED | 1924 | codecconfig | Refer to notes | B | NOT | 1925 | | below | | RECOMMENDED | 1926 | isup_usi | Refer to notes | B | NOT | 1927 | | below | | RECOMMENDED | 1928 | uiLayer1_Prot | Refer to notes | B | NOT | 1929 | | below | | RECOMMENDED | 1930 | chain | Refer to notes | B | NOT | 1931 | | below | | RECOMMENDED | 1932 | | | | | 1933 +------------------------+------------------+-------+---------------+ 1935 RFC3108 Attribute Analysis 1937 RFC3108 describes conventions for using the Session Description 1938 Protocol (SDP) for characterizing ATM bearer connections using an 1939 AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5, 1940 bearer connections can be used to transport single media streams. In 1941 addition, for AAL1 and AAL2, multiple media streams may be 1942 multiplexed into a bearer connection. For all adaptation types 1943 (AAL1, AAL2 and AAL5), bearer connections may be bundled into a 1944 single media group. In all cases addressed by RFC3108, a real-time 1945 media stream (voice, video, voiceband data, pseudo-wire and others) 1946 or a multiplex of media streams is mapped directly into an ATM 1947 connection. RFC3108 does not address cases where ATM serves as a 1948 low-level transport pipe for IP packets which in turn may carry one 1949 or more real-time (e.g. VoIP) media sessions with a life-cycle 1950 different from that of the underlying ATM transport. 1952 [I-D.ietf-mmusic-sdp-bundle-negotiation] is applicable only for 1953 nettypes IN and address types "IP4" or "IP6". 1955 5.49. 3GPP TS 26.114 1957 [R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and 1958 interaction 1960 +----------------------+-------------------------+-------+----------+ 1961 | Name | Notes | Level | Mux | 1962 | | | | Category | 1963 +----------------------+-------------------------+-------+----------+ 1964 | 3gpp_sync_info | Usage defined for the | M | NORMAL | 1965 | | IP Multimedia Subsystem | | | 1966 | | | | | 1967 | 3gpp_MaxRecvSDUSize | Usage defined for the | M | NORMAL | 1968 | | IP Multimedia Subsystem | | | 1969 | | | | | 1970 +----------------------+-------------------------+-------+----------+ 1972 3GPP TS 26.114 Attribute Analysis 1974 5.50. 3GPP TS 183.063 1976 [R3GPPTS183.063] Telecommunications and Internet converged Services 1977 and Protocols for Advanced Networking (TISPAN); 1979 +---------------------+---------------+-------+--------------+ 1980 | Name | Notes | Level | Mux Category | 1981 +---------------------+---------------+-------+--------------+ 1982 | PSCid | Not Impacted | S | NORMAL | 1983 | | | | | 1984 | bc_service | Not Impacted | S | NORMAL | 1985 | | | | | 1986 | bc_program | Not Impacted | S | NORMAL | 1987 | | | | | 1988 | bc_service_package | Not Impacted | S | NORMAL | 1989 | | | | | 1990 +---------------------+---------------+-------+--------------+ 1992 3GPP TS 183.063 Attribute Analysis 1994 5.51. 3GPP TS 24.182 1996 [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting 1997 tones 1998 +-------------+---------------------------------+-------+-----------+ 1999 | Name | Notes | Level | Mux | 2000 | | | | Category | 2001 +-------------+---------------------------------+-------+-----------+ 2002 | g.3gpp.cat | Usage defined for the IP | M | NORMAL | 2003 | | Multimedia Subsystem | | | 2004 | | | | | 2005 +-------------+---------------------------------+-------+-----------+ 2007 3GPP TS 24.182 Attribute Analysis 2009 5.52. 3GPP TS 24.183 2011 [R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing 2012 Signal 2014 +-------------+---------------------------------+-------+-----------+ 2015 | Name | Notes | Level | Mux | 2016 | | | | Category | 2017 +-------------+---------------------------------+-------+-----------+ 2018 | g.3gpp.crs | Usage defined for the IP | M | NORMAL | 2019 | | Multimedia Subsystem | | | 2020 | | | | | 2021 +-------------+---------------------------------+-------+-----------+ 2023 3GPP TS 24.183 Attribute Analysis 2025 5.53. 3GPP TS 24.229 2027 [R3GPPTS24.229] specifies IP multimedia call control protocol based 2028 on Session Initial protocol and Session Description Protocol. 2030 +------------------+---------------------------+-------+------------+ 2031 | Name | Notes | Level | Mux | 2032 | | | | Category | 2033 +------------------+---------------------------+-------+------------+ 2034 | secondary-realm | secondary-realm must be | M | TRANSPORT | 2035 | | the one that corresponds | | | 2036 | | to the "m=" line chosen | | | 2037 | | for setting up the | | | 2038 | | underlying transport flow | | | 2039 | | | | | 2040 | visited-realm | visited-realm must be | M | TRANSPORT | 2041 | | the one that corresponds | | | 2042 | | to the "m=" line chosen | | | 2043 | | for setting up the | | | 2044 | | underlying transport flow | | | 2045 | | | | | 2046 | omr-m-cksum | Not Impacted | M | NORMAL | 2047 | | | | | 2048 | omr-s-cksum | Not Impacted | M | NORMAL | 2049 | | | | | 2050 | omr-m-att | Not Impacted | M | NORMAL | 2051 | | | | | 2052 | omr-s-att | Not Impacted | M | NORMAL | 2053 | | | | | 2054 | omr-m-bw | Not Impacted | M | NORMAL | 2055 | | | | | 2056 | omr-s-bw | Not Impacted | M | NORMAL | 2057 | | | | | 2058 | omr-codecs | Not Impacted | M | NORMAL | 2059 | | | | | 2060 +------------------+---------------------------+-------+------------+ 2062 3GPP TS 24.229 Attribute Analysis 2064 5.54. ITU T.38 2066 [T.38] defines procedures for real-time Group 3 facsimile 2067 communications over IP networks. 2069 +------------------------+---------------+-------+--------------+ 2070 | Name | Notes | Level | Mux Category | 2071 +------------------------+---------------+-------+--------------+ 2072 | T38FaxVersion | Not Impacted | S | NORMAL | 2073 | | | | | 2074 | T38MaxBitRate | Not Impacted | S | NORMAL | 2075 | | | | | 2076 | T38FaxFillBitRemoval | Not Impacted | S | NORMAL | 2077 | | | | | 2078 | T38FaxTranscodingMMR | Not Impacted | S | NORMAL | 2079 | | | | | 2080 | T38FaxTranscodingJBIG | Not Impacted | S | NORMAL | 2081 | | | | | 2082 | T38FaxRateManagement | Not Impacted | S | NORMAL | 2083 | | | | | 2084 | T38FaxMaxBuffer | Not Impacted | S | NORMAL | 2085 | | | | | 2086 | T38FaxMaxDatagram | Not Impacted | S | NORMAL | 2087 | | | | | 2088 | T38FaxUdpEC | Not Impacted | S | NORMAL | 2089 | | | | | 2090 | T38FaxMaxIFP | Not Impacted | S | NORMAL | 2091 | | | | | 2092 | T38FaxUdpECDepth | Not Impacted | S | NORMAL | 2093 | | | | | 2094 | T38FaxUdpFECMaxSpan | Not Impacted | S | NORMAL | 2095 | | | | | 2096 | T38ModemType | Not Impacted | S | NORMAL | 2097 | | | | | 2098 | T38VendorInfo | Not Impacted | S | NORMAL | 2099 | | | | | 2100 +------------------------+---------------+-------+--------------+ 2102 ITU T.38 Attribute Analysis 2104 The ITU T.38 attributes are clearly unaffected by multiplexing and 2105 are specific to the working of the fax protocol itself. 2107 5.55. ITU-T Q.1970 2109 [Q.1970] defines BICC IP bearer control protocol. 2111 +--------+---------------------------------------+-------+----------+ 2112 | Name | Notes | Level | Mux | 2113 | | | | Category | 2114 +--------+---------------------------------------+-------+----------+ 2115 | ipbcp | ipbcp version identifies type of | S | SPECIAL | 2116 | | IPBCP message used in BICC (ITU-T | | | 2117 | | Q.1901) environment which are limited | | | 2118 | | to single media payload. Pertinent | | | 2119 | | ITU.T specifications needs to be | | | 2120 | | referred while multiplexing | | | 2121 | | | | | 2122 +--------+---------------------------------------+-------+----------+ 2124 ITU-T Q.1970 Attribute Analysis 2126 5.56. ITU-T H.248.15 2128 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248 2129 package attribute 2131 +-----------+------------------------------------+-------+----------+ 2132 | Name | Notes | Level | Mux | 2133 | | | | Category | 2134 +-----------+------------------------------------+-------+----------+ 2135 | h248item | It is only applicable for | B | SPECIAL | 2136 | | signaling the inclusion of H.248 | | | 2137 | | extension packages to a gateway | | | 2138 | | via the local and remote | | | 2139 | | descriptors. The attribute itself | | | 2140 | | is unaffected by multiplexing, but | | | 2141 | | the packaged referenced in a | | | 2142 | | specific use of the attribute may | | | 2143 | | be impacted. Further analysis of | | | 2144 | | each package is needed to | | | 2145 | | determine if there is an issue. | | | 2146 | | This is only a concern in | | | 2147 | | environments using a decomposed | | | 2148 | | server/gateway with H.248 signaled | | | 2149 | | between them. The ITU-T will need | | | 2150 | | to do further analysis of various | | | 2151 | | packages when they specify how to | | | 2152 | | signal the use of multiplexing to | | | 2153 | | a gateway | | | 2154 | | | | | 2155 +-----------+------------------------------------+-------+----------+ 2157 ITU-T H.248.15 Attribute Analysis 2159 5.57. RFC4975 - The Message Session Relay Protocol 2161 [RFC4975] the Message Session Relay Protocol, a protocol for 2162 transmitting a series of related instant messages in the context of a 2163 session. Message sessions are treated like any other media stream 2164 when set up via a rendezvous or session creation protocol such as the 2165 Session Initiation Protocol. 2167 +-----------------------+---------------+-------+--------------+ 2168 | Name | Notes | Level | Mux Category | 2169 +-----------------------+---------------+-------+--------------+ 2170 | accept-types | Not Impacted | M | NORMAL | 2171 | | | | | 2172 | accept-wrapped-types | Not Impacted | M | NORMAL | 2173 | | | | | 2174 | max-size | Not Impacted | M | NORMAL | 2175 | | | | | 2176 | path | Not Impacted | M | NORMAL | 2177 | | | | | 2178 +-----------------------+---------------+-------+--------------+ 2180 RFC4975 Attribute Analysis 2182 5.58. Historical Attributes 2184 This section specifies analysis for the attributes that are included 2185 for historic usage alone by the [IANA]. 2187 +----------+----------------------+-------+------------------+ 2188 | Name | Notes | Level | Mux Category | 2189 +----------+----------------------+-------+------------------+ 2190 | rtpred1 | Historic attributes | M | NOT RECOMMENDED | 2191 | | | | | 2192 | rtpred2 | Historic attributes | M | NOT RECOMMENDED | 2193 | | | | | 2194 +----------+----------------------+-------+------------------+ 2196 Historical Attribute Analysis 2198 6. bwtype Attribute Analysis 2200 This section specifies handling of specific bandwidth attributes when 2201 used in multiplexing scenarios. 2203 6.1. RFC4566 - SDP: Session Description Protocol 2205 [RFC4566] defines the Session Description Protocol (SDP) that is 2206 intended for describing multimedia sessions for the purposes of 2207 session announcement, session invitation, and other forms of 2208 multimedia session initiation. 2210 +------------+-----------------------------------+-------+----------+ 2211 | Name | Notes | Level | Mux | 2212 | | | | Category | 2213 +------------+-----------------------------------+-------+----------+ 2214 | bwtype:CT | Not Impacted | S | NORMAL | 2215 | | | | | 2216 | bwtype:AS | For the media level usage, the | B | SUM | 2217 | | aggregate of individual bandwidth | | | 2218 | | values is considered | | | 2219 | | | | | 2220 +------------+-----------------------------------+-------+----------+ 2222 RFC4566 bwtype Analysis 2224 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth 2226 [RFC3556] defines an extension to the Session Description Protocol 2227 (SDP) to specify two additional modifiers for the bandwidth 2228 attribute. These modifiers may be used to specify the bandwidth 2229 allowed for RTP Control Protocol (RTCP) packets in a Real-time 2230 Transport Protocol (RTP) session. 2232 +------------+-----------------------------------+-------+----------+ 2233 | Name | Notes | Level | Mux | 2234 | | | | Category | 2235 +------------+-----------------------------------+-------+----------+ 2236 | bwtype:RS | Session level usage represents | B | SUM | 2237 | | session aggregate and media level | | | 2238 | | usage indicates SUM of the | | | 2239 | | individual values while | | | 2240 | | multiplexing | | | 2241 | | | | | 2242 | bwtype:RR | Session level usage represents | B | SUM | 2243 | | session aggregate and media level | | | 2244 | | usage indicates SUM of the | | | 2245 | | individual values while | | | 2246 | | multiplexing | | | 2247 | | | | | 2248 +------------+-----------------------------------+-------+----------+ 2250 RFC3556 bwtype Analysis 2252 6.3. RFC3890 - Bandwidth Modifier for SDP 2254 [RFC3890] defines a Session Description Protocol (SDP) Transport 2255 Independent Application Specific Maximum (TIAS) bandwidth modifier 2256 that does not include transport overhead; instead an additional 2257 packet rate attribute is defined. The transport independent bit-rate 2258 value together with the maximum packet rate can then be used to 2259 calculate the real bit-rate over the transport actually used. 2261 +------------------+-----------------------------+-------+----------+ 2262 | Name | Notes | Level | Mux | 2263 | | | | Category | 2264 +------------------+-----------------------------+-------+----------+ 2265 | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL | 2266 | | clearly defined | | | 2267 | | Offer/Answer usage. | | | 2268 | | | | | 2269 | bwtype:maxprate | The usage of TIAS and | B | SPECIAL | 2270 | | maxprate is not well | | | 2271 | | defined under multiplexing | | | 2272 | | | | | 2273 +------------------+-----------------------------+-------+----------+ 2275 RFC3890 bwtype Analysis 2277 The intention of TIAS is that the media level bit-rate is multiplied 2278 with the known per-packet overhead for the selected transport and the 2279 maxprate value to determine the worst case bit-rate from the 2280 transport to more accurately capture the required usage. Summing 2281 TIAS values independently across "m=" lines and multiplying the 2282 computed sum with maxprate and the per-packet overhead would inflate 2283 the value significantly. Instead performing multiplication and 2284 adding the individual values is a more appropriate usage. 2286 7. rtcp-fb Attribute Analysis 2288 This section analyzes rtcp-fb SDP attributes. 2290 7.1. RFC4585 - RTP/AVPF 2292 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 2293 enables receivers to provide, statistically, more immediate feedback 2294 to the senders and thus allows for short-term adaptation and 2295 efficient feedback-based repair mechanisms to be implemented. 2297 +----------+----------------------------+-------+-------------------+ 2298 | Name | Notes | Level | Mux Category | 2299 +----------+----------------------------+-------+-------------------+ 2300 | ack rpsi | The attribute value must | M | IDENTICAL-PER-PT | 2301 | | be same for a given codec | | | 2302 | | configuration | | | 2303 | | | | | 2304 | ack app | Feedback parameters must | M | SPECIAL | 2305 | | be handled in the app | | | 2306 | | specific way when | | | 2307 | | multiplexed | | | 2308 | | | | | 2309 | nack | The attribute value must | M | IDENTICAL-PER-PT | 2310 | | be same for a given codec | | | 2311 | | configuration | | | 2312 | | | | | 2313 | nack pli | The attribute value must | M | IDENTICAL-PER-PT | 2314 | | be same for a given codec | | | 2315 | | configuration | | | 2316 | | | | | 2317 | nack sli | The attribute value must | M | IDENTICAL-PER-PT | 2318 | | be same for a given codec | | | 2319 | | configuration | | | 2320 | | | | | 2321 | nack | The attribute value must | M | IDENTICAL-PER-PT | 2322 | rpsi | be same for a given codec | | | 2323 | | configuration | | | 2324 | | | | | 2325 | nack app | Feedback parameters must | M | SPECIAL | 2326 | | be handled in the app | | | 2327 | | specific way when | | | 2328 | | multiplexed | | | 2329 | | | | | 2330 | trr-int | The attribute value must | M | IDENTICAL-PER-PT | 2331 | | be same for a given codec | | | 2332 | | configuration | | | 2333 | | | | | 2334 +----------+----------------------------+-------+-------------------+ 2336 RFC4585 Attribute Analysis 2338 7.2. RFC5104 - Codec Control Messages in AVPF 2340 [RFC5104] specifies a few extensions to the messages defined in the 2341 Audio-Visual Profile with Feedback (AVPF). They are helpful 2342 primarily in conversational multimedia scenarios where centralized 2343 multipoint functionalities are in use. However, some are also usable 2344 in smaller multicast environments and point-to-point calls. 2346 +------+--------------------------------+-------+-------------------+ 2347 | Name | Notes | Level | Mux Category | 2348 +------+--------------------------------+-------+-------------------+ 2349 | ccm | The attribute value must be | M | IDENTICAL-PER-PT | 2350 | | same for a given codec | | | 2351 | | configuration | | | 2352 | | | | | 2353 +------+--------------------------------+-------+-------------------+ 2355 RFC5104 Attribute Analysis 2357 7.3. RFC6285 - Unicast-Based RAMS 2359 [RFC6285] describes a method using the existing RTP and RTP Control 2360 Protocol (RTCP) machinery that reduces the acquisition delay. In 2361 this method, an auxiliary unicast RTP session carrying the Reference 2362 Information to the receiver precedes or accompanies the multicast 2363 stream. This unicast RTP flow can be transmitted at a faster than 2364 natural bitrate to further accelerate the acquisition. The 2365 motivating use case for this capability is multicast applications 2366 that carry real-time compressed audio and video. 2368 +-------+-------------------------------+-------+-------------------+ 2369 | Name | Notes | Level | Mux Category | 2370 +-------+-------------------------------+-------+-------------------+ 2371 | nack | The attribute value must be | M | IDENTICAL-PER-PT | 2372 | rai | same for a given codec | | | 2373 | | configuration | | | 2374 | | | | | 2375 +-------+-------------------------------+-------+-------------------+ 2377 RFC6285 Attribute Analysis 2379 7.4. RFC6679 - ECN for RTP over UDP/IP 2381 [RFC6679] specifies how Explicit Congestion Notification (ECN) can be 2382 used with the Real-time Transport Protocol (RTP) running over UDP, 2383 using the RTP Control Protocol (RTCP) as a feedback mechanism. It 2384 defines a new RTCP Extended Report (XR) block for periodic ECN 2385 feedback, a new RTCP transport feedback message for timely reporting 2386 of congestion events, and a Session Traversal Utilities for NAT 2387 (STUN) extension used in the optional initialization method using 2388 Interactive Connectivity Establishment (ICE). 2390 +------------------+---------------------------+-------+------------+ 2391 | Name | Notes | Level | Mux | 2392 | | | | Category | 2393 +------------------+---------------------------+-------+------------+ 2394 | ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL | 2395 | | the RTP Session level | | | 2396 | | | | | 2397 | nack ecn | This attribute enables | M | IDENTICAL | 2398 | | ECN at the RTP session | | | 2399 | | level | | | 2400 | | | | | 2401 +------------------+---------------------------+-------+------------+ 2403 RFC6679 Attribute Analysis 2405 7.5. RFC6642 - Third-Party Loss Report 2407 In a large RTP session using the RTP Control Protocol (RTCP) feedback 2408 mechanism defined in [RFC4585], a feedback target may experience 2409 transient overload if some event causes a large number of receivers 2410 to send feedback at once. This overload is usually avoided by 2411 ensuring that feedback reports are forwarded to all receivers, 2412 allowing them to avoid sending duplicate feedback reports. However, 2413 there are cases where it is not recommended to forward feedback 2414 reports, and this may allow feedback implosion. [RFC6642] memo 2415 discusses these cases and defines a new RTCP Third-Party Loss Report 2416 that can be used to inform receivers that the feedback target is 2417 aware of some loss event, allowing them to suppress feedback. 2418 Associated Session Description Protocol (SDP) signaling is also 2419 defined. 2421 +--------+------------------------------+-------+-------------------+ 2422 | Name | Notes | Level | Mux Category | 2423 +--------+------------------------------+-------+-------------------+ 2424 | nack | The attribute value must be | M | IDENTICAL-PER-PT | 2425 | tllei | same for a given codec | | | 2426 | | configuration | | | 2427 | | | | | 2428 | nack | The attribute value must be | M | IDENTICAL-PER-PT | 2429 | pslei | same for a given codec | | | 2430 | | configuration | | | 2431 | | | | | 2432 +--------+------------------------------+-------+-------------------+ 2434 RFC6642 Attribute Analysis 2436 7.6. RFC5104 - Codec Control Messages in AVPF 2438 [RFC5104] specifies a few extensions to the messages defined in the 2439 Audio-Visual Profile with Feedback (AVPF). They are helpful 2440 primarily in conversational multimedia scenarios where centralized 2441 multipoint functionalities are in use. However, some are also usable 2442 in smaller multicast environments and point-to-point calls. 2444 +--------+------------------------------+-------+-------------------+ 2445 | Name | Notes | Level | Mux Category | 2446 +--------+------------------------------+-------+-------------------+ 2447 | ccm | The attribute value must be | M | IDENTICAL-PER-PT | 2448 | fir | same for a given codec | | | 2449 | | configuration | | | 2450 | | | | | 2451 | ccm | The attribute value must be | M | IDENTICAL-PER-PT | 2452 | tmmbr | same for a given codec | | | 2453 | | configuration | | | 2454 | | | | | 2455 | ccm | The attribute value must be | M | IDENTICAL-PER-PT | 2456 | tstr | same for a given codec | | | 2457 | | configuration | | | 2458 | | | | | 2459 | ccm | The attribute value must be | M | IDENTICAL-PER-PT | 2460 | vbcm | same for a given codec | | | 2461 | | configuration | | | 2462 | | | | | 2463 +--------+------------------------------+-------+-------------------+ 2465 RFC5104 Attribute Analysis 2467 8. group Attribute Analysis 2469 This section analyzes SDP "group" attribute semantics. 2471 8.1. RFC5888 - SDP Grouping Framework 2473 [RFC5888] defines a framework to group "m" lines in the Session 2474 Description Protocol (SDP) for different purposes. 2476 +------------+---------------+-------+--------------+ 2477 | Name | Notes | Level | Mux Category | 2478 +------------+---------------+-------+--------------+ 2479 | group:LS | Not Impacted | S | NORMAL | 2480 | | | | | 2481 | group:FID | Not Impacted | S | NORMAL | 2482 | | | | | 2483 +------------+---------------+-------+--------------+ 2485 RFC5888 Attribute Analysis 2487 8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows 2489 [RFC3524] defines an extension to the Session Description Protocol 2490 (SDP) grouping framework. It allows requesting a group of media 2491 streams to be mapped into a single resource reservation flow. The 2492 SDP syntax needed is defined, as well as a new "semantics" attribute 2493 called Single Reservation Flow (SRF). 2495 +------------+---------------+-------+--------------+ 2496 | Name | Notes | Level | Mux Category | 2497 +------------+---------------+-------+--------------+ 2498 | group:SRF | Not Impacted | S | NORMAL | 2499 | | | | | 2500 +------------+---------------+-------+--------------+ 2502 RFC3524 Attribute Analysis 2504 8.3. RFC4091 - ANAT Semantics 2506 [RFC4091] defines the Alternative Network Address Types (ANAT) 2507 semantics for the Session Description Protocol (SDP) grouping 2508 framework. The ANAT semantics allow alternative types of network 2509 addresses to establish a particular media stream. 2511 +-------------+---------------------------+-------+-----------------+ 2512 | Name | Notes | Level | Mux Category | 2513 +-------------+---------------------------+-------+-----------------+ 2514 | group:ANAT | ANAT semantics is | S | NOT RECOMMENDED | 2515 | | obseleted | | | 2516 | | | | | 2517 +-------------+---------------------------+-------+-----------------+ 2519 RFC4091 Attribute Analysis 2521 8.4. RFC5956 - FEC Grouping Semantics in SDP 2523 [RFC5956] defines the semantics for grouping the associated source 2524 and FEC-based (Forward Error Correction) repair flows in the Session 2525 Description Protocol (SDP). The semantics defined in the document 2526 are to be used with the SDP Grouping Framework (RFC 5888). These 2527 semantics allow the description of grouping relationships between the 2528 source and repair flows when one or more source and/or repair flows 2529 are associated in the same group, and they provide support for 2530 additive repair flows. SSRC-level (Synchronization Source) grouping 2531 semantics are also defined in this document for Real-time Transport 2532 Protocol (RTP) streams using SSRC multiplexing. 2534 +---------------+---------------+-------+--------------+ 2535 | Name | Notes | Level | Mux Category | 2536 +---------------+---------------+-------+--------------+ 2537 | group:FEC-FR | Not Impacted | S | NORMAL | 2538 | | | | | 2539 +---------------+---------------+-------+--------------+ 2541 RFC5956 Attribute Analysis 2543 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP 2545 [RFC5583] defines semantics that allow for signaling the decoding 2546 dependency of different media descriptions with the same media type 2547 in the Session Description Protocol (SDP). This is required, for 2548 example, if media data is separated and transported in different 2549 network streams as a result of the use of a layered or multiple 2550 descriptive media coding process. 2552 +--------+------------------------------+-------+-------------------+ 2553 | Name | Notes | Level | Mux Category | 2554 +--------+------------------------------+-------+-------------------+ 2555 | depend | The attribute value must be | M | IDENTICAL-PER-PT | 2556 | lay | same for a given codec | | | 2557 | | configuration | | | 2558 | | | | | 2559 | depend | The attribute value must be | M | IDENTICAL-PER-PT | 2560 | mdc | same for a given codec | | | 2561 | | configuration | | | 2562 | | | | | 2563 +--------+------------------------------+-------+-------------------+ 2565 RFC5583 Attribute Analysis 2567 8.6. RFC7104 - Duplication Grouping Semantics in the SDP 2569 [RFC7104] defines the semantics for grouping redundant streams in the 2570 Session Description Protocol (SDP). The semantics defined in this 2571 document are to be used with the SDP Grouping Framework. Grouping 2572 semantics at the Synchronization Source (SSRC) level are also defined 2573 in this document for RTP streams using SSRC multiplexing. 2575 +------------+---------------+-------+--------------+ 2576 | Name | Notes | Level | Mux Category | 2577 +------------+---------------+-------+--------------+ 2578 | group:DUP | Not Impacted | S | NORMAL | 2579 | | | | | 2580 +------------+---------------+-------+--------------+ 2582 RFC7104 Attribute Analysis 2584 9. ssrc-group Attribute Analysis 2586 This section analyzes "ssrc-group" semantics. 2588 9.1. RFC5576 - Source-Specific SDP Attributes 2590 [RFC5576] defines a mechanism to describe RTP media sources, which 2591 are identified by their synchronization source (SSRC) identifiers, in 2592 SDP, to associate attributes with these sources, and to express 2593 relationships among sources. It also defines several source-level 2594 attributes that can be used to describe properties of media sources. 2596 +-------------------+---------------+-------+--------------+ 2597 | Name | Notes | Level | Mux Category | 2598 +-------------------+---------------+-------+--------------+ 2599 | ssrc-group:FID | Not Impacted | SR | NORMAL | 2600 | | | | | 2601 | ssrc-group:FEC | Not Impacted | SR | NORMAL | 2602 | | | | | 2603 | ssrc-groupFEC-FR | Not Impacted | SR | NORMAL | 2604 | | | | | 2605 +-------------------+---------------+-------+--------------+ 2607 RFC5576 Attribute Analysis 2609 9.2. RFC7104 - Duplication Grouping Semantics in the SDP 2611 [RFC7104] defines the semantics for grouping redundant streams in the 2612 Session Description Protocol (SDP). The semantics defined in this 2613 document are to be used with the SDP Grouping Framework. Grouping 2614 semantics at the Synchronization Source (SSRC) level are also defined 2615 in this document for RTP streams using SSRC multiplexing. 2617 +-----------------+---------------+-------+--------------+ 2618 | Name | Notes | Level | Mux Category | 2619 +-----------------+---------------+-------+--------------+ 2620 | ssrc-group:DUP | Not Impacted | SR | NORMAL | 2621 | | | | | 2622 +-----------------+---------------+-------+--------------+ 2624 RFC7104 Attribute Analysis 2626 10. QoS Mechanism Token Analysis 2628 This section analyzes QoS tokes specified with SDP. 2630 10.1. RFC5432 - QoS Mechanism Selection in SDP 2632 [RFC5432] defines procedures to negotiate QOS mechanisms using the 2633 Session Description Protocol (SDP) offer/answer model. 2635 +-------+---------------+-------+--------------+ 2636 | Name | Notes | Level | Mux Category | 2637 +-------+---------------+-------+--------------+ 2638 | rsvp | Not Impacted | B | NORMAL | 2639 | | | | | 2640 | nsis | Not Impacted | B | NORMAL | 2641 | | | | | 2642 +-------+---------------+-------+--------------+ 2644 RFC5432 Attribute Analysis 2646 11. k= Attribute Analysis 2648 11.1. RFC4566 SDP: Session Description Protocol 2650 [RFC4566] defines the Session Description Protocol (SDP) that is 2651 intended for describing multimedia sessions for the purposes of 2652 session announcement, session invitation, and other forms of 2653 multimedia session initiation. 2655 +------+------------------------------------+-------+---------------+ 2656 | Name | Notes | Level | Mux Category | 2657 +------+------------------------------------+-------+---------------+ 2658 | k= | It is NOT recommended to use this | S | NOT | 2659 | | attribute | | RECOMMENDED | 2660 | | | | | 2661 +------+------------------------------------+-------+---------------+ 2663 RFC4566 Attribute Analysis 2665 12. content Attribute Analysis 2667 12.1. RFC4796 2669 [RFC4796] defines a new Session Description Protocol (SDP) media- 2670 level attribute, 'content'. The 'content' attribute defines the 2671 content of the media stream to a more detailed level than the media 2672 description line. The sender of an SDP session description can 2673 attach the 'content' attribute to one or more media streams. The 2674 receiving application can then treat each media stream differently 2675 (e.g., show it on a big or small screen) based on its content. 2677 +------------------+---------------+-------+--------------+ 2678 | Name | Notes | Level | Mux Category | 2679 +------------------+---------------+-------+--------------+ 2680 | content:slides | Not Impacted | M | NORMAL | 2681 | | | | | 2682 | content:speaker | Not Impacted | M | NORMAL | 2683 | | | | | 2684 | content:main | Not Impacted | M | NORMAL | 2685 | | | | | 2686 | content:sl | Not Impacted | M | NORMAL | 2687 | | | | | 2688 | content:alt | Not Impacted | M | NORMAL | 2689 | | | | | 2690 +------------------+---------------+-------+--------------+ 2692 RFC4796 Attribute Analysis 2694 13. Payload Formats 2696 13.1. RFC5109 - RTP Payload Format for Generic FEC 2698 [RFC5109] describes a payload format for generic Forward Error 2699 Correction (FEC) for media data encapsulated in RTP. It is based on 2700 the exclusive-or (parity) operation. The payload format allows end 2701 systems to apply protection using various protection lengths and 2702 levels, in addition to using various protection group sizes to adapt 2703 to different media and channel characteristics. It enables complete 2704 recovery of the protected packets or partial recovery of the critical 2705 parts of the payload depending on the packet loss situation. 2707 +---------------------+----------------------+-------+--------------+ 2708 | Name | Notes | Level | Mux Category | 2709 +---------------------+----------------------+-------+--------------+ 2710 | audio/ulpfec | Not recommended for | M | NOT | 2711 | | multiplexing due to | | RECOMMENDED | 2712 | | reuse of SSRCs | | | 2713 | | | | | 2714 | video/ulpfec | Not recommended for | M | NOT | 2715 | | multiplexing due to | | RECOMMENDED | 2716 | | reuse of SSRCs | | | 2717 | | | | | 2718 | text/ulpfec | Not recommended for | M | NOT | 2719 | | multiplexing due to | | RECOMMENDED | 2720 | | reuse of SSRCs | | | 2721 | | | | | 2722 | application/ulpfec | Not recommended for | M | NOT | 2723 | | multiplexing due to | | RECOMMENDED | 2724 | | reuse of SSRCs | | | 2725 | | | | | 2726 +---------------------+----------------------+-------+--------------+ 2728 RFC5109 Payload Format Analysis 2730 14. Multiplexing Considerations for Encapsulating Attributes 2732 This sections deals with recommendations for defining the 2733 multiplexing characteristics of the SDP attributes that encapsulate 2734 other SDP attributes/parameters. Such attributes as of today, for 2735 example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of 2736 a generic framework for indicating and negotiating transport, media 2737 and media format related capabilities in the SDP. 2739 The behavior of such attributes under multiplexing is in turn defined 2740 by the multiplexing behavior of the attributes they encapsulate which 2741 are made known once the Offer/Answer negotiation process is 2742 completed. 2744 14.1. RFC3407 - cpar Attribute Analysis 2746 [RFC3407] capability parameter attribute (a=cpar) encapsulates b= 2747 (bandwidth) or an a= attribute. For bandwidth attribute 2748 encapsulation, the category SUM is inherited. For the case of a= 2749 attribute, the category corresponding to the SDP attribute being 2750 encapsulated is inherited. 2752 v=0 2753 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2754 s= 2755 c=IN IP4 host.atlanta.example.com 2756 t=0 0 2757 m=video 3456 RTP/AVP 100 2758 a=rtpmap:100 VP8/90000 2759 a=sqn: 0 2760 a=cdsc: 1 video RTP/AVP 100 2761 a=cpar: a=rtcp-mux 2762 m=video 3456 RTP/AVP 101 2763 a=rtpmap:101 VP8/90000 2764 a=fmtp:100 max-fr=15;max-fs=1200 2765 a=cdsc: 2 video RTP/AVP 101 2766 a=cpar: a=rtcp-mux 2768 In the above example,the category IDENTICAL is inherited for the cpar 2769 encapsulated rtcp-mux attribute. 2771 14.2. RFC5939 Analysis 2773 [RFC5939] defines a general SDP capability negotiation framework. It 2774 also specifies how to provide transport protocols and SDP attributes 2775 as capabilities and negotiate them using the framework. 2777 For this purpose, [RFC5939] defines the following 2779 o A set of capabilities for the session and its associated media 2780 stream components, supported by each side. The attribute 2781 ("a=acap") defines how to list an attribute name and its 2782 associated value (if any) as a capability. The attribute 2783 ("a=tcap") defines how to list transport protocols (e.g., "RTP/ 2784 AVP") as capabilities. 2786 o A set of potential configurations ("a=pcfg") provided by the 2787 offerer to indicate whcich combination of those capabilities can 2788 be used for the session and its associated media stream 2789 components. Potential configurations are not ready for use until 2790 fully negotiated. They provide an alternative that may be used, 2791 subject to SDP capability negotiation procedures. In particular 2792 the answerer may choose one of the potential configurations for 2793 use as part of the current Offer/Answer exchange. 2795 o An actual configuration ("a=acfg") for the session and its 2796 associated media stream components. The actual configuration 2797 identifies the potential configuration that was negotiated for 2798 use. Use of an actual configuration does not require any further 2799 negotiation. 2801 o A negotiation process that takes the current actual and the set of 2802 potential configurations (combinations of capabilities) as input 2803 and provides the negotiated actual configurations as output. In 2804 [RFC5939] the negotiation process is done independently for each 2805 media description. 2807 14.2.1. Recommendation - Procedures for Potential Configuration Pairing 2809 This section provides recommendations for entities generating and 2810 processing SDP under the generic capability negotiation framework as 2811 defined in [RFC5939] under the context of media stream multiplexing. 2813 These recommendations are provided for the purposes of enabling the 2814 Offerer to make sure that the generated potential configurations 2815 between the multiplexed streams can (easily) be negotiated to be 2816 consistent between those streams. In particular, the procedures aim 2817 to simplify Answerer's procedure to choose potential configurations 2818 that are consistent across all the multiplexed media descriptions. 2820 A potential configuration selects a set of attributes and parameters 2821 that become part of the media description when negotiated. When 2822 multiplexing media descriptions with potential configurations 2823 specified, there may be a need for coordinating this selection 2824 between multiplexed media descriptions ensuring right multiplexing 2825 behavior. 2827 Although it is possible to analyze the various potential 2828 configurations in multiplexed media descriptions to find combinations 2829 that satisfy such constraints, it can quickly become complicated to 2830 do so. 2832 The procedures defined in [RFC5939] state that each potential 2833 configuration in the SDP has a unique configuration number, however 2834 the scope of uniqueness is limited to each media description. To 2835 make it simple for the answerer to chose valid combinations of 2836 potential configurations across media descriptions in a given bundle 2837 group, we provide a simple rule for constructing potential 2838 configurations 2840 o Let m-bundle be the set of media descriptions that form a given 2841 bundle . 2843 o Let m-bundle-pcfg be the set of media descriptions in m-bundle 2844 that include one or more potential configurations. 2846 o Each media description in m-bundle-pcfg must have at least one 2847 potential configuration with the same configuration number (e.g. 2848 "1"). 2850 o For each potential configuration with configuration number x in m- 2851 bundle-pcfg, the offerer MUST ensure that if the answerer chooses 2852 configuration number x in each of the media descriptions in m- 2853 bundle-pcfg, then the resulting SDP will have all multiplexing 2854 constraints satisfied for those media descriptions. 2856 o Since it is nearly impossible to define a generic mechanism for 2857 various capability extensions, this document does't provide 2858 procedures for dealing with the capability extension attributes. 2859 However, Section 14.3 provide analysis of media capability 2860 extension attributes as defined in [RFC6871]. 2862 The above allows the answerer to easily find multiplexing compatible 2863 combinations of potential configurations:- The answerer simply choses 2864 a potential configuration (number) that is present in all of the 2865 media descriptions with potential configurations in the bundle. 2867 Note that it is still possible for the offerer to provide additional 2868 potential configurations with independent configuration numbers. The 2869 answerer will have to perform more complicated analysis to determine 2870 valid multiplexed combinations of those. 2872 14.2.1.1. Example: Transport Capability Multiplexing 2874 v=0 2875 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2876 s= 2877 c=IN IP4 host.atlanta.example.com 2878 t=0 0 2879 a=tcap:1 RTP/SAVPF 2880 a=tcap:2 RTP/SAVP 2881 a=group:BUNDLE audio video 2882 m= audio 2883 a=mid:audio 2884 a=pcfg:1 t=1 2885 a=pcfg:2 2886 m= video 2887 a=mid:video 2888 a=pcfg:1 t=1 2889 a=pcfg:2 t=2 2891 In the example above, the potential configurations that offer 2892 transport protocol capability of RTP/SAVPF has the same configuration 2893 number "1" in both the audio and video media descriptions. 2895 14.2.1.2. Example: Attribute Capability Multiplexing 2897 v=0 2898 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2899 s= 2900 c=IN IP4 host.atlanta.example.com 2901 t=0 0 2902 a=acap:1 a=rtcp-mux 2903 a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80 2904 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 2905 a=group:BUNDLE audio video 2906 m= audio 49172 RTP/AVP 99 2907 a=mid:audio 2908 a=pcfg:1 a=1 2909 a=pcfg:2 2910 m= video 560024 RTP/AVP 100 2911 a=mid:video 2912 a=pcfg:1 a=1 2913 a=pcfg:2 a=2 2915 In the example above, the potential configuration number "1" is 2916 repeated while referring to attribute capability a=rtcp-mux, since 2917 the behavior is IDENTICAL for the attribute a=rtcp-mux under 2918 multiplexing. 2920 14.3. RFC6871 Analysis 2922 [RFC6871] extends capability negotiation framework described in 2923 [RFC5939] by defining media capabilities that can be used to indicate 2924 and negotiate media types and their associated format parameters. It 2925 also allows indication of latent configurations and session 2926 capabilities. 2928 14.3.1. Recommendation: Dealing with Payload Type Numbers 2930 [RFC6871] defines a new payload type ("pt") parameter to be used with 2931 the potential, actual and latent configuration parameters. The 2932 parameter associates RTP payload type numbers with the referenced 2933 RTP-based media format capabilities ("a=rmcap") defined in [RFC6871] 2934 and is appropriate only when the transport protocol uses RTP. This 2935 means that the same payload type number can be assigned as part of 2936 potential or actual configurations in different media descriptions in 2937 a bundle. There are rules for the usage of identical Payload Type 2938 values across multiplexed "m=" lines as described in 2939 [I-D.ietf-mmusic-sdp-bundle-negotiation], which must be followed here 2940 as well. As described in Section 14.2.1, the use of identical 2941 configuration numbers for compatible configurations in different 2942 media descriptions that are part of the bundle provides a way to 2943 ensure that the answerer can easily pick compatible configurations 2944 here as well. 2946 14.3.1.1. Example: Attribute Capability Under Shared Payload Type 2948 The attributes (a=rmcap, a=mfcap) follow the above recommendations 2949 under multiplexing. 2951 v=0 2952 o=- 25678 753849 IN IP4 192.0.2.1 2953 s= 2954 c=IN IP4 192.0.2.1 2955 t=0 0 2956 a=creq:med-v0 2957 m=audio 54322 RTP/AVP 96 2958 a=rtpmap:96 AMR-WB/16000/1 2959 a=fmtp:96 mode-change-capability=1; max-red=220; 2960 mode-set=0,2,4,7 2961 a=rmcap:1,3 audio AMR-WB/16000/1 2962 a=rmcap:2 audio AMR/8000/1 2963 a=mfcap:1,2 mode-change-capability=1 2964 a=mfcap:3 mode-change-capability=2 2965 a=pcfg:1 m=1 pt=1:96 2966 a=pcfg:2 m=2 pt=2:97 2967 a=pcfg:3 m=3 pt=3:98 2968 m=audio 54322 RTP/AVP 96 2969 a=rtpmap:96 AMR-WB/16000/1 2970 a=fmtp:96 mode-change-capability=1; max-red=220; 2971 mode-set=0,2,4,7 2972 a=rmcap:4 audio AMR/8000/1 2973 a=rmcap:5 audio OPUS/48000/2 2974 a=mfcap:5 minptime=40 2975 a=mfcap:4 mode-change-capability=1 2976 a=pcfg:1 m=4 pt=4:97 2977 a=pcfg:4 m=5 pt=5:101 2979 In the example above, the potential configuration number "1" is 2980 repeated when referring to media and media format capability used for 2981 the Payload Type 97. This implies that both the media capability 2 2982 and 4 along with their media format capabilities must refer to the 2983 same codec configuration, as per the definition of IDENTICAL-PER-PT. 2985 14.3.2. Recommendation: Dealing with Latent Configurations 2987 [RFC6871] adds the notion of a latent configurations, which provides 2988 configuration information that may be used to guide a subsequent 2989 offer/exchange, e.g. by adding another media stream or use 2990 alternative codec combinations not currently offered. Latent 2991 configurations have configuration numbers which cannot overlap with 2992 the potential configuration numbers [RFC6871]. Supported 2993 combinations of potential and latent configurations are indicated by 2994 use of the "a=sescap" attribute, however use of this attribute is not 2995 recommended with multiplexed media, since it requires the use of 2996 unique configuration numbers across the SDP. Taken together, this 2997 means there is no well-defined way to indicate supported combinations 2998 of latent configurations, or combinations of latent and potential 2999 configurations with multiplexed media. It is still allowed to use 3000 the latent configuration attribute, however the limitations above 3001 will apply. To determine valid combinations, actual negotiation will 3002 have to be attempted subsequently instead. 3004 15. IANA Considerations 3006 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 3007 document.] 3009 The IANA is requested to add a new column named "Mux Category" to 3010 several of the subregistries in the "Session Description Protocol 3011 (SDP) Parameters" registry. Section 15.1 defines a new subregistry 3012 for identifying the initial registrations for various multiplexing 3013 categories applicable, as proposed in this document. 3015 The tables in Section 15.2 identify name of an entry in the existing 3016 subregistry and specify the value to put in the new "Mux Category" 3017 column of the associated IANA registry. Any entries in the existing 3018 tables that do not have a value for the "Mux Category" specified in 3019 this RFC will get a value of "TBD". Future specifications can change 3020 the "TBD" entries to the correct value. 3022 15.1. New 'Multiplexing Categories' subregistry 3024 A new sub-registry needs to be defined called the "Multiplexing 3025 Categories", with the following registrations created initially: 3026 "NORMAL", "NOT RECOMMENDED", "IDENTICAL", "TRANSPORT", "SUM", 3027 "INHERIT", "IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this 3028 document. 3030 Initial value registration for "Multiplexing Categories". 3032 +-------------------------+-----------+ 3033 | Multiplexing Categories | Reference | 3034 +-------------------------+-----------+ 3035 | NORMAL | RFCXXXX | 3036 | NOT RECOMMENDED | RFCXXXX | 3037 | IDENTICAL | RFCXXXX | 3038 | TRANSPORT | RFCXXXX | 3039 | SUM | RFCXXXX | 3040 | INHERIT | RFCXXXX | 3041 | IDENTICAL-PER-PT | RFCXXXX | 3042 | SPECIAL | RFCXXXX | 3043 | TBD | RFCXXXX | 3044 +-------------------------+-----------+ 3046 Further entries may be registered on a first-come first-serve basis. 3047 Each registration needs to indicate the multiplexing category value 3048 to be added to the "Multiplexing Categories" subregistry as defined 3049 in this section. 3051 Such a registration must also indicate the applicability of the newly 3052 defined multiplexing category value to various subregistries defined 3053 at "Session Description Protocol (SDP) Parameters". 3055 The general registration procedures of [RFC4566] apply. 3057 15.2. 'Mux Category' column for subregistries 3059 Each sub-section identifies a subregistry in the "Session Description 3060 Protocol (SDP) Parameters" registry. The tables list the column that 3061 identifies the SDP attribute name/Token/Value from the corresponding 3062 subregistries and the values to be used for the new "Mux Category" 3063 column to be added. 3065 15.2.1. Table: SDP bwtype 3067 The following values are to be added to the 'SDP bwtype' subregistry 3068 in the "Session Description Protocol (SDP) Parameters" registry. The 3069 references should be updated to point at this RFC as well as the 3070 previous references. 3072 +----------+--------------+ 3073 | SDP Name | Mux Category | 3074 +----------+--------------+ 3075 | CT | NORMAL | 3076 | AS | SUM | 3077 | RS | SUM | 3078 | RR | SUM | 3079 | TIAS | SPECIAL | 3080 +----------+--------------+ 3082 15.2.2. Table: att-field (session level) 3084 The following values are to be added to the "att-field (session 3085 level)" subregistry in the "Session Description Protocol (SDP) 3086 Parameters" registry. The references should be updated to point at 3087 this RFC as well as the previous references. 3089 +---------------------+------------------+ 3090 | SDP Name | Mux Category | 3091 +---------------------+------------------+ 3092 | cat | NORMAL | 3093 | keywds | NORMAL | 3094 | type | NORMAL | 3095 | type:broadcast | NORMAL | 3096 | type:H332 | NORMAL | 3097 | type:meeting | NORMAL | 3098 | type:moderated | NORMAL | 3099 | type:test | NORMAL | 3100 | charset | NORMAL | 3101 | charset:iso8895-1 | NORMAL | 3102 | tool | NORMAL | 3103 | ipbcp | SPECIAL | 3104 | group | NORMAL | 3105 | ice-lite | NORMAL | 3106 | ice-options | NORMAL | 3107 | bcastversion | NORMAL | 3108 | 3GPP-Integrity-Key | NOT RECOMMENDED | 3109 | 3GPP-SDP-Auth | NOT RECOMMENDED | 3110 | alt-group | NOT RECOMMENDED | 3111 | PSCid | NORMAL | 3112 | bc_service | NORMAL | 3113 | bc_program | NORMAL | 3114 | bc_service_package | NORMAL | 3115 | sescap | NOT RECOMMENDED | 3116 | rtsp-ice-d-m | NOT RECOMMENDED | 3117 +---------------------+------------------+ 3119 15.2.3. Table: att-field (both session and media level) 3121 The following values are to be added to the "att-field (both session 3122 and media level)" subregistry in the "Session Description Protocol 3123 (SDP) Parameters" registry. The references should be updated to 3124 point at this RFC as well as the previous references. 3126 +-------------------------+-------------------+ 3127 | SDP Name | Mux Category | 3128 +-------------------------+-------------------+ 3129 | recvonly | NORMAL | 3130 | sendrecv | NORMAL | 3131 | sendonly | NORMAL | 3132 | sdplang | NORMAL | 3133 | lang | NORMAL | 3134 | h248item | SPECIAL | 3135 | sqn | NORMAL | 3136 | cdsc | NORMAL | 3137 | cpar | INHERIT | 3138 | cparmin | SPECIAL | 3139 | cparmax | SPECIAL | 3140 | rtcp-xr | NORMAL | 3141 | maxprate | SPECIAL | 3142 | setup | IDENTICAL | 3143 | connection | IDENTICAL | 3144 | key-mgmt | IDENTICAL | 3145 | source-filter | IDENTICAL | 3146 | inactive | NORMAL | 3147 | fingerprint | TRANSPORT | 3148 | flute-tsi | TBD | 3149 | flute-ch | TBD | 3150 | FEC-declaration | TBD | 3151 | FEC-OTI-extension | TBD | 3152 | content-desc | TBD | 3153 | ice-pwd | TRANSPORT | 3154 | ice-ufrag | TRANSPORT | 3155 | stkmstream | NORMAL | 3156 | extmap | SPECIAL | 3157 | qos-mech-send | NORMAL | 3158 | qos-mech-recv | NORMAL | 3159 | csup | NORMAL | 3160 | creq | NORMAL | 3161 | acap | INHERIT | 3162 | tcap | INHERIT | 3163 | 3GPP-QoE-Metrics | NOT RECOMMENDED | 3164 | 3GPP-Asset-Information | NOT RECOMMENDED | 3165 | mbms-mode | NOT RECOMMENDED | 3166 | mbms-repair | NOT RECOMMENDED | 3167 | ike-setup | IDENTICAL | 3168 | psk-fingerprint | IDENTICAL | 3169 | multicast-rtcp | IDENTICAL | 3170 | rmcap | IDENTICAL-PER-PT | 3171 | omcap | NORMAL | 3172 | mfcap | IDENTICAL-PER-PT | 3173 | mscap | INHERIT | 3174 | 3gpp.iut.replication | TBD | 3175 | bcap | INHERIT | 3176 | ccap | IDENTICAL | 3177 | icap | NORMAL | 3178 | 3gpp_sync_info | NORMAL | 3179 | 3gpp_MaxRecvSDUSize | NORMAL | 3180 | etag | NOT RECOMMENDED | 3181 | duplication-delay | NORMAL | 3182 | range | NOT RECOMMENDED | 3183 | control | NOT RECOMMENDED | 3184 | mtag | NOT RECOMMENDED | 3185 | ts-refclk | NORMAL | 3186 | mediaclk | NORMAL | 3187 | calgextmap | NORMAL | 3188 +-------------------------+-------------------+ 3190 15.2.4. Table: att-field (media level only) 3192 The following values are to be added to the "att-field (media level 3193 only)" registry in the "Session Description Protocol (SDP) 3194 Parameters" registry. The references should be updated to point at 3195 this RFC as well as the previous references. 3197 +---------------------------+-------------------+ 3198 | SDP Name | Mux Category | 3199 +---------------------------+-------------------+ 3200 | ptime | IDENTICAL-PER-PT | 3201 | orient | NORMAL | 3202 | orient:portrait | NORMAL | 3203 | orient:landscape | NORMAL | 3204 | orient:seascape | NORMAL | 3205 | framerate | IDENTICAL-PER-PT | 3206 | quality | NORMAL | 3207 | rtpmap | IDENTICAL-PER-PT | 3208 | fmtp | IDENTICAL-PER-PT | 3209 | rtpred1 | NOT RECOMMENDED | 3210 | rtpred2 | NOT RECOMMENDED | 3211 | T38FaxVersion | NORMAL | 3212 | T38MaxBitRate | NORMAL | 3213 | T38FaxFillBitRemoval | NORMAL | 3214 | T38FaxTranscodingMMR | NORMAL | 3215 | T38FaxTranscodingJBIG | NORMAL | 3216 | T38FaxRateManagement | NORMAL | 3217 | T38FaxMaxBuffer | NORMAL | 3218 | T38FaxMaxDatagram | NORMAL | 3219 | T38FaxUdpEC | NORMAL | 3220 | maxptime | IDENTICAL-PER-PT | 3221 | des | NOT RECOMMENDED | 3222 | curr | NOT RECOMMENDED | 3223 | conf | NOT RECOMMENDED | 3224 | mid | NORMAL | 3225 | rtcp | IDENTICAL | 3226 | rtcp-fb | IDENTICAL-PER-PT | 3227 | label | NORMAL | 3228 | T38VendorInfo | NORMAL | 3229 | crypto | TRANSPORT | 3230 | eecid | NOT RECOMMENDED | 3231 | aalType | NOT RECOMMENDED | 3232 | capability | NOT RECOMMENDED | 3233 | qosClass | NOT RECOMMENDED | 3234 | bcob | NOT RECOMMENDED | 3235 | stc | NOT RECOMMENDED | 3236 | upcc | NOT RECOMMENDED | 3237 | atmQOSparms | NOT RECOMMENDED | 3238 | atmTrfcDesc | NOT RECOMMENDED | 3239 | abrParms | NOT RECOMMENDED | 3240 | abrSetup | NOT RECOMMENDED | 3241 | bearerType | NOT RECOMMENDED | 3242 | lij | NOT RECOMMENDED | 3243 | anycast | NOT RECOMMENDED | 3244 | cache | NOT RECOMMENDED | 3245 | bearerSigIE | NOT RECOMMENDED | 3246 | aalApp | NOT RECOMMENDED | 3247 | cbrRate | NOT RECOMMENDED | 3248 | sbc | NOT RECOMMENDED | 3249 | clkrec | NOT RECOMMENDED | 3250 | fec | NOT RECOMMENDED | 3251 | prtfl | NOT RECOMMENDED | 3252 | structure | NOT RECOMMENDED | 3253 | cpsSDUsize | NOT RECOMMENDED | 3254 | all2CPS | NOT RECOMMENDED | 3255 | all2CPSSDUrate | NOT RECOMMENDED | 3256 | aal2sscs3661unassured | NOT RECOMMENDED | 3257 | aal2sscs3661assured | NOT RECOMMENDED | 3258 | aal2sscs3662 | NOT RECOMMENDED | 3259 | aal5sscop | NOT RECOMMENDED | 3260 | atmmap | NOT RECOMMENDED | 3261 | silenceSupp | NOT RECOMMENDED | 3262 | ecan | NOT RECOMMENDED | 3263 | gc | NOT RECOMMENDED | 3264 | profileDesc | NOT RECOMMENDED | 3265 | vsel | NOT RECOMMENDED | 3266 | dsel | NOT RECOMMENDED | 3267 | fsel | NOT RECOMMENDED | 3268 | onewaySel | NOT RECOMMENDED | 3269 | codecConfig | NOT RECOMMENDED | 3270 | isup_usi | NOT RECOMMENDED | 3271 | uiLayer1_Prot | NOT RECOMMENDED | 3272 | chain | NOT RECOMMENDED | 3273 | floorctrl | IDENTICAL | 3274 | confid | NORMAL | 3275 | userid | NORMAL | 3276 | floorid | NORMAL | 3277 | FEC | NORMAL | 3278 | accept-types | NORMAL | 3279 | accept-wrapped-types | NORMAL | 3280 | max-size | NORMAL | 3281 | path | NORMAL | 3282 | dccp-service-code | NOT RECOMMENDED | 3283 | rtcp-mux | IDENTICAL | 3284 | candidate | TRANSPORT | 3285 | ice-mismatch | NORMAL | 3286 | remote-candidates | TRANSPORT | 3287 | SRTPAuthentication | NORMAL | 3288 | SRTPROCTxRate | NORMAL | 3289 | rtcp-rsize | IDENTICAL | 3290 | file-selector | NORMAL | 3291 | file-transfer-id | NORMAL | 3292 | file-disposition | NORMAL | 3293 | file-date | NORMAL | 3294 | file-icon | NORMAL | 3295 | file-range | NORMAL | 3296 | depend | IDENTICAL-PER-PT | 3297 | ssrc | NORMAL | 3298 | ssrc-group | NORMAL | 3299 | rtcp-unicast | IDENTICAL | 3300 | pcfg | SPECIAL | 3301 | acfg | SPECIAL | 3302 | zrtp-hash | NOT RECOMMENDED | 3303 | X-predecbufsize | NOT RECOMMENDED | 3304 | X-initpredecbufperiod | NOT RECOMMENDED | 3305 | X-initpostdecbufperiod | NOT RECOMMENDED | 3306 | X-decbyterate | NOT RECOMMENDED | 3307 | 3gpp-videopostdecbufsize | NOT RECOMMENDED | 3308 | framesize | NOT RECOMMENDED | 3309 | 3GPP-SRTP-Config | NOT RECOMMENDED | 3310 | alt | NOT RECOMMENDED | 3311 | alt-default-id | NOT RECOMMENDED | 3312 | 3GPP-Adaption-Support | NOT RECOMMENDED | 3313 | mbms-flowid | NOT RECOMMENDED | 3314 | fec-source-flow | SPECIAL | 3315 | fec-repair-flow | SPECIAL | 3316 | repair-window | SPECIAL | 3317 | rams-updates | NOT RECOMMENDED | 3318 | imageattr | IDENTICAL-PER-PT | 3319 | cfw-id | NORMAL | 3320 | portmapping-req | NOT RECOMMENDED | 3321 | g.3gpp.cat | NORMAL | 3322 | g.3gpp.crs | NORMAL | 3323 | ecn-capable-rtp | IDENTICAL | 3324 | visited-realm | TRANSPORT | 3325 | secondary-realm | TRANSPORT | 3326 | omr-s-cksum | NORMAL | 3327 | omr-m-cksum | NORMAL | 3328 | omr-codecs | NORMAL | 3329 | omr-m-att | NORMAL | 3330 | omr-s-att | NORMAL | 3331 | omr-m-bw | NORMAL | 3332 | omr-s-bw | NORMAL | 3333 | msrp-cema | NORMAL | 3334 | dccp-port | NOT RECOMMENDED | 3335 | resource | NORMAL | 3336 | channel | NORMAL | 3337 | cmid | NORMAL | 3338 | content | NORMAL | 3339 | lcfg | SPECIAL | 3340 | loopback | NORMAL | 3341 | loopback-source | NORMAL | 3342 | loopback-mirror | NORMAL | 3343 | chatroom | TBD | 3344 | altc | TRANSPORT | 3345 | T38FaxMaxIFP | NORMAL | 3346 | T38FaxUdpECDepth | NORMAL | 3347 | T38FaxUdpFECMaxSpan | NORMAL | 3348 | T38ModemType | NORMAL | 3349 | cs-correlation | NORMAL | 3350 | rtcp-idms | NORMAL | 3351 +---------------------------+-------------------+ 3353 15.2.5. Table: att-field (source level) 3355 The following values are to be added to the "att-field (source 3356 level)" registry in the "Session Description Protocol (SDP) 3357 Parameters" registry. The references should be updated to point at 3358 this RFC as well as the previous references. 3360 +----------------+-------------------+ 3361 | SDP Name | Mux Category | 3362 +----------------+-------------------+ 3363 | cname | NORMAL | 3364 | previous-ssrc | NORMAL | 3365 | fmtp | IDENTICAL-PER-PT | 3366 | ts-refclk | NORMAL | 3367 | mediaclk | NORMAL | 3368 +----------------+-------------------+ 3370 15.2.6. Table: content SDP Parameters 3372 The following values are to be added to the "content SDP Parameters" 3373 subregistry in the "Session Description Protocol (SDP) Parameters" 3374 registry. The references should be updated to point at this RFC as 3375 well as the previous references. 3377 +----------+--------------+ 3378 | SDP Name | Mux Category | 3379 +----------+--------------+ 3380 | slides | NORMAL | 3381 | speaker | NORMAL | 3382 | sl | NORMAL | 3383 | main | NORMAL | 3384 | alt | NORMAL | 3385 +----------+--------------+ 3387 15.2.7. Table: Semantics for the 'group' SDP Attribute 3389 The following values are to be added to the "Semantics for the 3390 "group" SDP Attribute" subregistry in the "Session Description 3391 Protocol (SDP) Parameters" registry. The references should be 3392 updated to point at this RFC as well as the previous references. 3394 +---------+------------------+ 3395 | Token | Mux Category | 3396 +---------+------------------+ 3397 | LS | NORMAL | 3398 | FID | NORMAL | 3399 | SRF | NORMAL | 3400 | ANAT | NOT RECOMMENDED | 3401 | FEC | NORMAL | 3402 | FEC-FR | NORMAL | 3403 | CS | NORMAL | 3404 | DDP | NORMAL | 3405 | DUP | NORMAL | 3406 +---------+------------------+ 3408 15.2.8. Table: 'rtcp-fb' Attribute Values 3410 The following values are to be added to the " 'rtcp-fb' Attribute 3411 Values" subregistry in the "Session Description Protocol (SDP) 3412 Parameters" registry. The references should be updated to point at 3413 this RFC as well as the previous references. 3415 +------------+-------------------+ 3416 | Value Name | Mux Category | 3417 +------------+-------------------+ 3418 | ack | IDENTICAL-PER-PT | 3419 | app | SPECIAL | 3420 | ccm | IDENTICAL-PER-PT | 3421 | nack | IDENTICAL-PER-PT | 3422 | trr-int | IDENTICAL-PER-PT | 3423 +------------+-------------------+ 3425 15.2.9. Table: 'ack' and 'nack' Attribute Values 3427 The following values are to be added to the " 'ack' and 'nack' 3428 Attribute Values" subregistry in the "Session Description Protocol 3429 (SDP) Parameters" registry. The references should be updated to 3430 point at this RFC as well as the previous references. 3432 +------------+-------------------+ 3433 | Value Name | Mux Category | 3434 +------------+-------------------+ 3435 | sli | IDENTICAL-PER-PT | 3436 | pli | IDENTICAL-PER-PT | 3437 | rpsi | IDENTICAL-PER-PT | 3438 | app | SPECIAL | 3439 | rai | IDENTICAL-PER-PT | 3440 | tllei | IDENTICAL-PER-PT | 3441 | pslei | IDENTICAL-PER-PT | 3442 | ecn | IDENTICAL | 3443 +------------+-------------------+ 3445 15.2.10. Table: 'depend' SDP Attribute Values 3447 The following values are to be added to the " 'depend' SDP Attribute 3448 Values" subregistry in the "Session Description Protocol (SDP) 3449 Parameters" registry. The references should be updated to point at 3450 this RFC as well as the previous references. 3452 +-------+-------------------+ 3453 | Token | Mux Category | 3454 +-------+-------------------+ 3455 | lay | IDENTICAL-PER-PT | 3456 | mdc | IDENTICAL-PER-PT | 3457 +-------+-------------------+ 3459 15.2.11. Table: 'cs-correlation' Attribute Values 3461 The following values are to be added to the " "cs-correlation" 3462 Attribute Values" subregistry in the "Session Description Protocol 3463 (SDP) Parameters" registry. The references should be updated to 3464 point at this RFC as well as the previous references. 3466 +-----------+--------------+ 3467 | Value | Mux Category | 3468 +-----------+--------------+ 3469 | callerid | NORMAL | 3470 | uuie | NORMAL | 3471 | dtmf | NORMAL | 3472 | external | NORMAL | 3473 +-----------+--------------+ 3475 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 3477 The following values are to be added to the Semantics for the 3478 "Semantics for the "ssrc-group" SDP Attribute" subregistry in the 3479 "Session Description Protocol (SDP) Parameters" registry. The 3480 references should be updated to point at this RFC as well as the 3481 previous references. 3483 +---------+--------------+ 3484 | Token | Mux Category | 3485 +---------+--------------+ 3486 | FID | NORMAL | 3487 | FEC | NORMAL | 3488 | FEC-FR | NORMAL | 3489 | DUP | NORMAL | 3490 +---------+--------------+ 3492 15.2.13. Table: SDP/RTSP key management protocol identifiers 3494 The following values are to be added to the "SDP/RTSP key management 3495 protocol identifiers" subregistry in the "Session Description 3496 Protocol (SDP) Parameters" registry. The references should be 3497 updated to point at this RFC as well as the previous references. 3499 +------------+--------------+ 3500 | Value Name | Mux Category | 3501 +------------+--------------+ 3502 | mikey | IDENTICAL | 3503 +------------+--------------+ 3505 15.2.14. Table: Codec Control Messages 3507 The following values are to be added to the "Codec Control Messages" 3508 subregistry in the "Session Description Protocol (SDP) Parameters" 3509 registry. The references should be updated to point at this RFC as 3510 well as the previous references. 3512 +------------+-------------------+ 3513 | Value Name | Mux Category | 3514 +------------+-------------------+ 3515 | fir | IDENTICAL-PER-PT | 3516 | tmmbr | IDENTICAL-PER-PT | 3517 | tstr | IDENTICAL-PER-PT | 3518 | vbcm | IDENTICAL-PER-PT | 3519 +------------+-------------------+ 3521 15.2.15. Table: QoS Mechanism Tokens 3523 The following values are to be added to the "QoS Mechanism Tokens" 3524 subregistry in the "Session Description Protocol (SDP) Parameters" 3525 registry. The references should be updated to point at this RFC as 3526 well as the previous references. 3528 +---------------+--------------+ 3529 | QoS Mechanism | Mux Category | 3530 +---------------+--------------+ 3531 | rsvp | NORMAL | 3532 | nsis | NORMAL | 3533 +---------------+--------------+ 3535 15.2.16. Table: SDP Capability Negotiation Option Tags 3537 The following values are to be added to the "SDP Capability 3538 Negotiation Option Tags" subregistry in the "Session Description 3539 Protocol (SDP) Parameters" registry. The references should be 3540 updated to point at this RFC as well as the previous references. 3542 +---------------+--------------+ 3543 | QoS Mechanism | Mux Category | 3544 +---------------+--------------+ 3545 | cap-v0 | NORMAL | 3546 | med-v0 | NORMAL | 3547 | bcap-v0 | NORMAL | 3548 | ccap-v0 | NORMAL | 3549 | icap-v0 | NORMAL | 3550 +---------------+--------------+ 3552 15.2.17. Table: Timestamp Reference Clock Source Parameters 3554 The following values are to be added to the "Timestamp Reference 3555 Clock Source Parameters" subregistry in the "Session Description 3556 Protocol (SDP) Parameters" registry. The references should be 3557 updated to point at this RFC as well as the previous references. 3559 +----------+--------------+ 3560 | Name | Mux Category | 3561 +----------+--------------+ 3562 | ntp | NORMAL | 3563 | ptp | NORMAL | 3564 | gps | NORMAL | 3565 | gal | NORMAL | 3566 | glonass | NORMAL | 3567 | local | NORMAL | 3568 | private | NORMAL | 3569 +----------+--------------+ 3571 15.2.18. Table: Media Clock Source Parameters 3573 The following values are to be added to the "Media Clock Source 3574 Parameters" subegistry in the "Session Description Protocol (SDP) 3575 Parameters" registry. The references should be updated to point at 3576 this RFC as well as the previous references. 3578 +-----------+--------------+ 3579 | Name | Mux Category | 3580 +-----------+--------------+ 3581 | sender | NORMAL | 3582 | direct | NORMAL | 3583 | IEEE1722 | NORMAL | 3584 +-----------+--------------+ 3586 16. Security Considerations 3588 This document does not add any new security considerations beyond the 3589 existing considerations in the RFCs for protocols that are being 3590 multiplexed together. 3592 The ways that SRTP streams are keyed is not believed to create any 3593 two-time pad vulnerability for the currently defined SRTP keying 3594 mechanism. 3596 17. Acknowledgments 3598 I would like to thank Cullen Jennings, Flemming Andreasen for 3599 suggesting the categories, contributing text and reviewing the draft. 3600 I would also link to thank Magnus Westerlund, Christer Holmberg, 3601 Jonathan Lennox, Bo Burman, Ari Keranen, and Dan Wing on suggesting 3602 structural changes helping improve the document readability. 3604 I would like also to thank following experts on their inputs and 3605 reviews as listed - Flemming Andreasen(5.24,5.32,5.33,14), Rohan 3606 Mahy(5.57), Eric Burger(5.26),Christian Huitema(5.14), Christer 3607 Holmberg(5.21,5.26,5.51,5.52), Richard Ejzak (5.44,5.53,5.54), Colin 3608 Perkins(5.7,5.8,5.9,5.58), Magnus 3609 Westerlund(5.2,5.3,5.9,5.27,5.47,6.1,6.2,6.3,8.3,7), Roni 3610 Evens(5.12,5.27,8.4), Subha Dhesikan(5.6,10), Dan 3611 Wing(5.7,5.12,5.35,5.39,5.45), Cullen Jennings (5.40), Ali C 3612 Begen(5.1,5.20,5.22,5.25,5.38,7.3,8.2,8.4,8.6,9.2,13.1), Bo Burman 3613 (7.2,7.6), Charles Eckel(5.15,5.27,5.28,9.1,8.5), Paul Kyzivat(5.24), 3614 Ian Johansson(5.15), Saravanan Shanmugham(5.11), Paul E Jones(5.30), 3615 Rajesh Kumar(5.48), Jonathan Lennox(5.36,5,15,9.1,11.1), Mo 3616 Zanaty(5.4,5.5,5.23,8.1,8.3,8.5,12.1), Christian Huitema (5.14), Qin 3617 Wu (5.47 PM-Dir review), Hans Stokking(5.43,5.16), Christian Groves 3618 (5.48,5.55) 3620 18. Change Log 3622 [RFC EDITOR NOTE: Please remove this section when publishing] 3624 Changes from draft-ietf-mmusic-sdp-mux-attributes-05 3626 o Incorporated review comments from Christian Grooves and Ari 3627 Keranen. 3629 o Fixed more nits to prep for the LastCall. 3631 Changes from draft-ietf-mmusic-sdp-mux-attributes-04 3633 o Fixed minor nits overall. 3635 o Updated Acknowledgement Sections 3637 o Last Call Version. 3639 Changes from draft-ietf-mmusic-sdp-mux-attributes-03 3641 o More re-work on the IANA section. 3643 o Clean ups preparing for the last call. 3645 Changes from draft-ietf-mmusic-sdp-mux-attributes-02 3647 o Incorporated suggestions from Flemming on Capability Negotiation. 3649 o Closed open issues from IETF90 3651 o Added IANA section to list the categories for all the SDP 3652 attributes anlayzed 3654 o Lots of cleanup 3656 o Reformatted Refernces section to use short-form notation 3658 Changes from draft-ietf-mmusic-sdp-mux-attributes-01 3660 o Updated section 15 to provide detailed recommendation on dealing 3661 with encapsulating attributes. Also updated sections 5.20, 5.28, 3662 5.29 to refer to Section 15. 3664 o Added new categories IDENTICAL-PER-PT and INHERIT 3666 o Updated Sections 16 to add the new categories. 3668 o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the 3669 category IDENTICAL-PER-PT. 3671 o Reformatted section 4 to add individual categories to their own 3672 sections. 3674 Changes from draft-ietf-mmusic-sdp-mux-attributes-00 3676 o Added Section 15 to provide recommendations on multiplexing SDP 3677 encapsulating attributes. Also updated sections 5.20, 5.28, 5.29 3678 to refer to Section 15. 3680 o Updated Section 5.38 to incorporate PM-dir review inputs from Qin 3681 Wu 3683 o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more 3684 clarity. 3686 o Fixed few nits regarding sentence clarity and fill-in the NOTES 3687 section where information was lacking. 3689 Changes from draft-nandakumar-mmusic-mux-attributes-05 3691 o Renamed the document to be a WG document. 3693 o Added Section 14. 3695 o Updated Open Issues based on IETF88 discussions. 3697 Changes from draft-nandakumar-mmusic-mux-attributes-04 3699 o Added few OPEN ISSUES that needs to be discussed. 3701 o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4, 3702 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1 3704 o Updated Table Column name Current to Level and improved TRANSPORT 3705 category explanation on suggestions form Dan Wing. 3707 o Grouped all the rtcp-fb attribute analysis under a single section 3708 as suggested by Magnus/ 3710 Changes from draft-nandakumar-mmusic-mux-attributes-03 3712 o Maintenance change to clean up grammatical nits and wordings. 3714 Changes from draft-nandakumar-mmusic-mux-attributes-02 3716 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34, 3717 5.37,5.40,5.41,5.42,5.43,5.44,5.45,6.1,6.2,6.3,8,3,12.1 based on 3718 the inputs from the respective RFC Authors. 3720 Changes from draft-nandakumar-mmusic-mux-attributes-01 3722 o Replaced Category BAD with NOT RECOMMENDED. 3724 o Added Category TBD. 3726 o Updated IANA Consideration Section. 3728 Changes from draft-nandakumar-mmusic-mux-attributes-00 3730 o Added new section for dealing with FEC payload types. 3732 19. References 3734 19.1. Normative References 3736 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3737 Requirement Levels", BCP 14, RFC 2119, March 1997. 3739 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 3740 Description Protocol", RFC 4566, July 2006. 3742 19.2. Informative References 3744 [H.248.15] 3745 "Gateway control protocol: SDP H.248 package attribute", 3746 . 3748 [I-D.ietf-mmusic-sdp-bundle-negotiation] 3749 Holmberg, C., Alvestrand, H., and C. Jennings, 3750 "Negotiating Media Multiplexing Using the Session 3751 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- 3752 negotiation-12 (work in progress), October 2014. 3754 [I.D-draft-ietf-dart-dscp-rtp] 3755 Black, D. and P. Jones, "The Session Description Protocol 3756 (SDP) Content Attribute", draft-ietf-dart-dscp-rtp-07 3757 (work in progress), September 2014. 3759 [IANA] "Session Description Protocol (SDP) Parameters", 3760 . 3763 [Q.1970] "Q.1970 : BICC IP bearer control protocol", 3764 . 3766 [R3GPPTS183.063] 3767 "TISPAN - IMS based ITPV Stage 3 specification.", 3768 . 3771 [R3GPPTS24.182] 3772 "IP Multimedia Subsystem (IMS) Customized Alerting Tones 3773 (CAT); Protocol specification", 3774 . 3776 [R3GPPTS24.183] 3777 "IP Multimedia Subsystem (IMS) Customized Ringing Signal 3778 (CRS); Protocol specification", 3779 . 3781 [R3GPPTS24.229] 3782 "IP multimedia call control protocol based on Session 3783 Initiation Protocol (SIP) and Session Description Protocol 3784 (SDP);", 3785 . 3787 [R3GPPTS26.114] 3788 "IP multimedia Subsystem : Media Handling and 3789 interaction", 3790 . 3792 [RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time 3793 Streaming Protocol (RTSP)", RFC 2326, April 1998. 3795 [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the 3796 Session Description Protocol (SDP) for ATM Bearer 3797 Connections", RFC 3108, May 2001. 3799 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 3800 with Session Description Protocol (SDP)", RFC 3264, June 3801 2002. 3803 [RFC3312] Camarillo, G., Marshall, W., and J. Rosenberg, 3804 "Integration of Resource Management and Session Initiation 3805 Protocol (SIP)", RFC 3312, October 2002. 3807 [RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple 3808 Capability Declaration", RFC 3407, October 2002. 3810 [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to 3811 Resource Reservation Flows", RFC 3524, April 2003. 3813 [RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth 3814 Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC 3815 3556, July 2003. 3817 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute 3818 in Session Description Protocol (SDP)", RFC 3605, October 3819 2003. 3821 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control 3822 Protocol Extended Reports (RTCP XR)", RFC 3611, November 3823 2003. 3825 [RFC3890] Westerlund, M., "A Transport Independent Bandwidth 3826 Modifier for the Session Description Protocol (SDP)", RFC 3827 3890, September 2004. 3829 [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network 3830 Address Types (ANAT) Semantics for the Session Description 3831 Protocol (SDP) Grouping Framework", RFC 4091, June 2005. 3833 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 3834 the Session Description Protocol (SDP)", RFC 4145, 3835 September 2005. 3837 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E. 3838 Carrara, "Key Management Extensions for Session 3839 Description Protocol (SDP) and Real Time Streaming 3840 Protocol (RTSP)", RFC 4567, July 2006. 3842 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session 3843 Description Protocol (SDP) Security Descriptions for Media 3844 Streams", RFC 4568, July 2006. 3846 [RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol 3847 (SDP) Source Filters", RFC 4570, July 2006. 3849 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 3850 Transport Layer Security (TLS) Protocol in the Session 3851 Description Protocol (SDP)", RFC 4572, July 2006. 3853 [RFC4574] Levin, O. and G. Camarillo, "The Session Description 3854 Protocol (SDP) Label Attribute", RFC 4574, August 2006. 3856 [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format 3857 for Binary Floor Control Protocol (BFCP) Streams", RFC 3858 4583, November 2006. 3860 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 3861 "Extended RTP Profile for Real-time Transport Control 3862 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 3863 2006. 3865 [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description 3866 Protocol (SDP) Content Attribute", RFC 4796, February 3867 2007. 3869 [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message 3870 Session Relay Protocol (MSRP)", RFC 4975, September 2007. 3872 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 3873 "Codec Control Messages in the RTP Audio-Visual Profile 3874 with Feedback (AVPF)", RFC 5104, February 2008. 3876 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error 3877 Correction", RFC 5109, December 2007. 3879 [RFC5159] Dondeti, L. and A. Jerichow, "Session Description Protocol 3880 (SDP) Attributes for Open Mobile Alliance (OMA) Broadcast 3881 (BCAST) Service and Content Protection", RFC 5159, March 3882 2008. 3884 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 3885 (ICE): A Protocol for Network Address Translator (NAT) 3886 Traversal for Offer/Answer Protocols", RFC 5245, April 3887 2010. 3889 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP 3890 Header Extensions", RFC 5285, July 2008. 3892 [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of 3893 Service (QoS) Mechanism Selection in the Session 3894 Description Protocol (SDP)", RFC 5432, March 2009. 3896 [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size 3897 Real-Time Transport Control Protocol (RTCP): Opportunities 3898 and Consequences", RFC 5506, April 2009. 3900 [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S., 3901 and P. Kyzivat, "A Session Description Protocol (SDP) 3902 Offer/Answer Mechanism to Enable File Transfer", RFC 5547, 3903 May 2009. 3905 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific 3906 Media Attributes in the Session Description Protocol 3907 (SDP)", RFC 5576, June 2009. 3909 [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding 3910 Dependency in the Session Description Protocol (SDP)", RFC 3911 5583, July 2009. 3913 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control 3914 Protocol (RTCP) Extensions for Single-Source Multicast 3915 Sessions with Unicast Feedback", RFC 5760, February 2010. 3917 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and 3918 Control Packets on a Single Port", RFC 5761, April 2010. 3920 [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control 3921 Protocol (DCCP)", RFC 5762, April 2010. 3923 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework 3924 for Establishing a Secure Real-time Transport Protocol 3925 (SRTP) Security Context Using Datagram Transport Layer 3926 Security (DTLS)", RFC 5763, May 2010. 3928 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description 3929 Protocol (SDP) Grouping Framework", RFC 5888, June 2010. 3931 [RFC5939] Andreasen, F., "Session Description Protocol (SDP) 3932 Capability Negotiation", RFC 5939, September 2010. 3934 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in 3935 the Session Description Protocol", RFC 5956, September 3936 2010. 3938 [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions 3939 Defined for 3GPP Packet-Switched Streaming Service and 3940 Multimedia Broadcast/Multicast Service", RFC 6064, January 3941 2011. 3943 [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source- 3944 Specific Multicast (SSM) Sessions", RFC 6128, February 3945 2011. 3947 [RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media 3948 Path Key Agreement for Unicast Secure RTP", RFC 6189, 3949 April 2011. 3951 [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for 3952 the Internet Key Exchange Protocol (IKE) in the Session 3953 Description Protocol (SDP)", RFC 6193, April 2011. 3955 [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media 3956 Control Channel Framework", RFC 6230, May 2011. 3958 [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image 3959 Attributes in the Session Description Protocol (SDP)", RFC 3960 6236, May 2011. 3962 [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping 3963 between Unicast and Multicast RTP Sessions", RFC 6284, 3964 June 2011. 3966 [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax, 3967 "Unicast-Based Rapid Acquisition of Multicast RTP 3968 Sessions", RFC 6285, June 2011. 3970 [RFC6364] Begen, A., "Session Description Protocol Elements for the 3971 Forward Error Correction (FEC) Framework", RFC 6364, 3972 October 2011. 3974 [RFC6642] Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP) 3975 Extension for a Third-Party Loss Report", RFC 6642, June 3976 2012. 3978 [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., 3979 and K. Carlberg, "Explicit Congestion Notification (ECN) 3980 for RTP over UDP", RFC 6679, August 2012. 3982 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection 3983 Establishment for Media Anchoring (CEMA) for the Message 3984 Session Relay Protocol (MSRP)", RFC 6714, August 2012. 3986 [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A 3987 Datagram Congestion Control Protocol UDP Encapsulation for 3988 NAT Traversal", RFC 6773, November 2012. 3990 [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control 3991 Protocol Version 2 (MRCPv2)", RFC 6787, November 2012. 3993 [RFC6849] Kaplan, H., Hedayat, K., Venna, N., Jones, P., and N. 3994 Stratton, "An Extension to the Session Description 3995 Protocol (SDP) and Real-time Transport Protocol (RTP) for 3996 Media Loopback", RFC 6849, February 2013. 3998 [RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session 3999 Description Protocol (SDP) Media Capabilities 4000 Negotiation", RFC 6871, February 2013. 4002 [RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S. 4003 Veikkolainen, "The Session Description Protocol (SDP) 4004 Alternate Connectivity (ALTC) Attribute", RFC 6947, May 4005 2013. 4007 [RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman, 4008 "Miscellaneous Capabilities Negotiation in the Session 4009 Description Protocol (SDP)", RFC 7006, September 2013. 4011 [RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping 4012 Semantics in the Session Description Protocol", RFC 7104, 4013 January 2014. 4015 [RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session 4016 Description Protocol (SDP) Extension for Setting Audio and 4017 Video Media Streams over Circuit-Switched Bearers in the 4018 Public Switched Telephone Network (PSTN)", RFC 7195, May 4019 2014. 4021 [RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay 4022 Attribute in the Session Description Protocol", RFC 7197, 4023 April 2014. 4025 [RFC7266] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control 4026 Protocol (RTCP) Extended Report (XR) Blocks for Mean 4027 Opinion Score (MOS) Metric Reporting", RFC 7266, June 4028 2014. 4030 [RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O., 4031 Boronat, F., Montagud, M., and K. Gross, "Inter- 4032 Destination Media Synchronization (IDMS) Using the RTP 4033 Control Protocol (RTCP)", RFC 7272, June 2014. 4035 [RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H. 4036 Stokking, "RTP Clock Source Signalling", RFC 7273, June 4037 2014. 4039 [T.38] "Procedures for real-time Group 3 facsimile communication 4040 over IP networks", . 4042 Author's Address 4044 Suhas Nandakumar 4045 Cisco 4046 170 West Tasman Drive 4047 San Jose, CA 95134 4048 USA 4050 Email: snandaku@cisco.com