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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 19, 2016 5 Expires: June 22, 2017 7 A Framework for SDP Attributes when Multiplexing 8 draft-ietf-mmusic-sdp-mux-attributes-16 10 Abstract 12 The purpose of this specification is to provide a framework for 13 analyzing the multiplexing characteristics of Session Description 14 Protocol (SDP) attributes when SDP is used to negotiate the usage of 15 single 5-tuple for sending and receiving media associated with 16 multiple media descriptions. 18 This specification also categorizes the existing SDP attributes based 19 on the framework described herein. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on June 22, 2017. 38 Copyright Notice 40 Copyright (c) 2016 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 56 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 57 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 6 58 4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . 6 59 4.1. Category: NORMAL . . . . . . . . . . . . . . . . . . . . 7 60 4.2. Category: CAUTION . . . . . . . . . . . . . . . . . . . . 7 61 4.3. Category: IDENTICAL . . . . . . . . . . . . . . . . . . . 8 62 4.4. Category: SUM . . . . . . . . . . . . . . . . . . . . . . 8 63 4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 9 64 4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 10 65 4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 10 66 4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 11 67 4.9. Category: TBD . . . . . . . . . . . . . . . . . . . . . . 11 68 5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 12 69 5.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 12 70 5.2. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 14 71 5.3. RFC5761: Multiplexing RTP and RTCP . . . . . . . . . . . 14 72 5.4. RFC3312: Integration of Resource Management and SIP . . . 14 73 5.5. RFC4574: SDP Label Attribute . . . . . . . . . . . . . . 15 74 5.6. RFC5432: QOS Mechanism Selection in SDP . . . . . . . . . 15 75 5.7. RFC4568: SDP Security Descriptions . . . . . . . . . . . 16 76 5.8. RFC5762: RTP over DCCP . . . . . . . . . . . . . . . . . 16 77 5.9. RFC6773: DCCP-UDP Encapsulation . . . . . . . . . . . . . 17 78 5.10. RFC5506: Reduced-Size RTCP in RTP Profile . . . . . . . . 18 79 5.11. RFC6787: Media Resource Control Protocol Version 2 . . . 18 80 5.12. RFC5245: ICE . . . . . . . . . . . . . . . . . . . . . . 19 81 5.13. RFC5285: RTP Header Extensions . . . . . . . . . . . . . 20 82 5.14. RFC3605: RTCP attribute in SDP . . . . . . . . . . . . . 21 83 5.15. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 21 84 5.16. RFC7273: RTP Clock Source Signalling . . . . . . . . . . 22 85 5.17. RFC6236: Image Attributes in SDP . . . . . . . . . . . . 23 86 5.18. RFC7197: Duplication Delay Attribute in SDP . . . . . . . 24 87 5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting . . . . 24 88 5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions . . 24 89 5.21. RFC6230: Media Control Channel Framework . . . . . . . . 25 90 5.22. RFC6364: SDP Elements for FEC Framework . . . . . . . . . 25 91 5.23. RFC4796: Content Attribute . . . . . . . . . . . . . . . 26 92 5.24. RFC3407: SDP Simple Capability Declaration . . . . . . . 26 93 5.25. RFC6284: Port Mapping between Unicast and Multicast RTP 94 Sessions . . . . . . . . . . . . . . . . . . . . . . . . 27 95 5.26. RFC6714: MSRP-CEMA . . . . . . . . . . . . . . . . . . . 28 96 5.27. RFC4583: SDP Format for BFCP Streams . . . . . . . . . . 28 97 5.28. RFC5547: SDP Offer/Answer for File Transfer . . . . . . . 29 98 5.29. RFC6849: SDP and RTP Media Loopback Extension . . . . . . 29 99 5.30. RFC5760: RTCP with Unicast Feedback . . . . . . . . . . . 30 100 5.31. RFC3611: RTCP XR . . . . . . . . . . . . . . . . . . . . 30 101 5.32. RFC5939: SDP Capability Negotiation . . . . . . . . . . . 31 102 5.33. RFC6871: SDP Media Capabilities Negotiation . . . . . . . 31 103 5.34. RFC7006: Miscellaneous Capabilities Negotiation SDP . . . 32 104 5.35. RFC4567: Key Management Extensions for SDP and RTSP . . . 33 105 5.36. RFC4572: Comedia over TLS in SDP . . . . . . . . . . . . 34 106 5.37. RFC4570: SDP Source Filters . . . . . . . . . . . . . . . 34 107 5.38. RFC6128: RTCP Port for Multicast Sessions . . . . . . . . 35 108 5.39. RFC6189: ZRTP . . . . . . . . . . . . . . . . . . . . . . 35 109 5.40. RFC4145: Connection-Oriented Media . . . . . . . . . . . 36 110 5.41. RFC6947: The SDP altc Attribute . . . . . . . . . . . . . 36 111 5.42. RFC7195: SDP Extension for Circuit Switched Bearers 112 in PSTN . . . . . . . . . . . . . . . . . . . . . . . . . 37 113 5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP) . . . 37 114 5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP 115 Attributes . . . . . . . . . . . . . . . . . . . . . . . 38 116 5.45. RFC6193: Media Description for IKE in SDP . . . . . . . . 38 117 5.46. RFC2326: Real Time Streaming Protocol . . . . . . . . . . 39 118 5.47. RFC6064: SDP and RTSP Extensions for 3GPP . . . . . . . . 40 119 5.48. RFC3108: ATM SDP . . . . . . . . . . . . . . . . . . . . 42 120 5.49. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 44 121 5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . . 45 122 5.51. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 45 123 5.52. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 46 124 5.53. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 46 125 5.54. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 47 126 5.55. ITU-T Q.1970 . . . . . . . . . . . . . . . . . . . . . . 49 127 5.56. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 49 128 5.57. RFC4975: The Message Session Relay Protocol . . . . . . . 50 129 5.58. Historical Attributes . . . . . . . . . . . . . . . . . . 51 130 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 51 131 6.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 52 132 6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth . . . 52 133 6.3. RFC3890: Bandwidth Modifier for SDP . . . . . . . . . . . 53 134 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 53 135 7.1. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 53 136 7.2. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 54 137 7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP 138 Sessions (RAMS) . . . . . . . . . . . . . . . . . . . . . 55 139 7.4. RFC6679: ECN for RTP over UDP/IP . . . . . . . . . . . . 55 140 7.5. RFC6642: Third-Party Loss Report . . . . . . . . . . . . 56 141 7.6. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 57 142 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 57 143 8.1. RFC5888: SDP Grouping Framework . . . . . . . . . . . . . 57 144 8.2. RFC3524: Mapping Media Streams to Resource 145 Reservation Flows . . . . . . . . . . . . . . . . . . . . 58 146 8.3. RFC4091: ANAT Semantics . . . . . . . . . . . . . . . . . 58 147 8.4. RFC5956: FEC Grouping Semantics in SDP . . . . . . . . . 58 148 8.5. RFC5583: Signaling Media Decoding Dependency in SDP . . . 59 149 8.6. RFC7104: Duplication Grouping Semantics in the SDP . . . 59 150 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 60 151 9.1. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 60 152 9.2. RFC7104: Duplication Grouping Semantics in the SDP . . . 60 153 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 61 154 10.1. RFC5432: QoS Mechanism Selection in SDP . . . . . . . . 61 155 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 61 156 11.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 62 157 12. content Attribute Analysis . . . . . . . . . . . . . . . . . 62 158 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 62 159 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 63 160 13.1. RFC5109: RTP Payload Format for Generic FEC . . . . . . 63 161 14. Multiplexing Considerations for Encapsulating Attributes . . 63 162 14.1. RFC3407: cpar Attribute Analysis . . . . . . . . . . . . 64 163 14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 64 164 14.2.1. Recommendation: Procedures for Potential 165 Configuration Pairing . . . . . . . . . . . . . . . 65 166 14.2.1.1. Example: Transport Capability Multiplexing . . . 66 167 14.2.1.2. Example: Attribute Capability Multiplexing . . . 67 168 14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 68 169 14.3.1. Recommendation: Dealing with Payload Type Numbers . 68 170 14.3.1.1. Example: Attribute Capability Under Shared 171 Payload Type . . . . . . . . . . . . . . . . . . 68 172 14.3.2. Recommendation: Dealing with Latent Configurations . 69 173 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 70 174 15.1. New 'Multiplexing Categories' subregistry . . . . . . . 70 175 15.2. 'Mux Category' column for subregistries . . . . . . . . 71 176 15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 71 177 15.2.2. Table: att-field (session level) . . . . . . . . . . 71 178 15.2.3. Table: att-field (both session and media level) . . 72 179 15.2.4. Table: att-field (media level only) . . . . . . . . 74 180 15.2.5. Table: att-field (source level) . . . . . . . . . . 77 181 15.2.6. Table: content SDP Parameters . . . . . . . . . . . 78 182 15.2.7. Table: Semantics for the 'group' SDP Attribute . . . 78 183 15.2.8. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 79 184 15.2.9. Table: 'ack' and 'nack' Attribute Values . . . . . . 79 185 15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . . 79 186 15.2.11. Table: 'cs-correlation' Attribute Values . . . . . . 80 187 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 80 188 15.2.13. Table: SDP/RTSP key management protocol identifiers 80 189 15.2.14. Table: Codec Control Messages . . . . . . . . . . . 81 190 15.2.15. Table: QoS Mechanism Tokens . . . . . . . . . . . . 81 191 15.2.16. Table: SDP Capability Negotiation Option Tags . . . 81 192 15.2.17. Table: Timestamp Reference Clock Source Parameters . 82 193 15.2.18. Table: Media Clock Source Parameters . . . . . . . . 82 194 16. Security Considerations . . . . . . . . . . . . . . . . . . . 83 195 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 83 196 18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 83 197 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 87 198 19.1. Normative References . . . . . . . . . . . . . . . . . . 87 199 19.2. Informative References . . . . . . . . . . . . . . . . . 87 200 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 95 202 1. Introduction 204 SDP defines several attributes for capturing characteristics that 205 apply to the individual media descriptions (described by "m=" lines") 206 and the overall multimedia session. Typically different media types 207 (audio, video, etc.) described using different media descriptions 208 represent separate RTP sessions that are carried over individual 209 transport layer flows. However 210 [I-D.ietf-mmusic-sdp-bundle-negotiation] defines a way to use a 211 single address:port combination (BUNDLE address) for receiving media 212 associated with multiple SDP media descriptions. This would, for 213 example allow the usage of a single set of Interactive Connectivity 214 Establishment (ICE) [RFC5245] candidates for multiple media 215 descriptions. This in turn has made it necessary to understand the 216 interpretation and usage of the SDP attributes defined for the 217 multiplexed media descriptions. 219 Given the number of SDP attributes registered with the [IANA] and 220 possibility of new attributes being defined in the future, there is 221 need for a framework to analyze these attributes for their 222 applicability in the transport multiplexing use-cases. 224 The document starts with providing the motivation for requiring such 225 a framework. This is followed by introduction to the SDP attribute 226 analysis framework/procedures, following which several sections apply 227 the framework to the SDP attributes registered with the [IANA]. 229 2. Terminology 231 5-tuple: A collection of the following values: source address, source 232 port, destination address, destination port, and transport-layer 233 protocol. 235 3GPP: Third Generation Partnership Project; see http://www.3gpp.org 236 for more information about this organization. 238 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 239 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 240 document are to be interpreted as described in [RFC2119]. 242 3. Motivation 244 The time and complications of setting up ICE [RFC5245] and Datagram 245 Transport Layer Security (DTLS) based Secure Real-time Transport 246 Protocol (SRTP) [RFC5763] transports for use by RTP, reasons to 247 conserve ports bindings on the Network Address Translators (NAT), 248 forms a requirement to try and reduce the number of transport level 249 flows needed. This has resulted in the definition of ways, such as 250 [I-D.ietf-mmusic-sdp-bundle-negotiation] to multiplex RTP over a 251 single transport flow in order to preserve network resources such as 252 port numbers. This imposes further restrictions on applicability of 253 the SDP attributes as they are defined today. 255 The specific problem is that there are attribute combinations which 256 make sense when specified on independent "m=" lines -- as with 257 classical SDP -- that do not make sense when those "m=" lines are 258 then multiplexed over the same transport. To give an obvious 259 example, ICE permits each "m=" line to have an independently 260 specified ice-ufrag attribute. However, if the media from multiple 261 "m=" lines is multiplexed over the same ICE component, then the 262 meaning of media-level ice-ufrag attributes becomes muddled. 264 At the time of writing this document there are close to 250 SDP 265 attributes registered with the [IANA] and more will be added in the 266 future. There is no clearly defined procedure to establish the 267 validity/applicability of these attributes when used with transport 268 multiplexing. 270 4. SDP Attribute Analysis Framework 272 Attributes in an SDP session description can be defined at the 273 session-level or media-level or source-level. Informally, there are 274 various semantic groupings for these attributes. One such grouping 275 could be notes as below: 277 o Attributes related to media content such as media type, encoding 278 schemes and payload types. 280 o Attributes specifying media transport characteristics like RTP/RTP 281 Control Protocol (RTCP) port numbers, network addresses and QOS. 283 o Metadata description attributes capturing session timing and 284 origin information. 286 o Attributes establishing relationships between media descriptions 287 such as grouping framework [RFC5888] 289 The proposed framework analyzes the SDP attributes usage under 290 multiplexing and assigns each SDP attribute to an appropriate 291 multiplexing category. Since the multiplexing categories defined in 292 this specification are independent of any informal semantic groupings 293 of the SDP attributes, the categorizations assigned are normative. 295 4.1. Category: NORMAL 297 The attributes in the NORMAL category can be independently specified 298 when multiplexed and they retain their original semantics. 300 In the example given below, the direction and label attributes are 301 independently specified for audio and video "m=" lines. These 302 attributes are not impacted by multiplexing these media streams over 303 a single transport layer flow. 305 v=0 306 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 307 s= 308 c=IN IP4 host.atlanta.example.com 309 t=0 0 310 m=audio 49172 RTP/AVP 99 311 a=sendonly 312 a=label:1 313 a=rtpmap:99 iLBC/8000 314 m=video 49172 RTP/AVP 31 315 a=recvonly 316 a=label:2 317 a=rtpmap:31 H261/90000 319 4.2. Category: CAUTION 321 The attributes in the CAUTION category are advised against 322 multiplexing since their usage under multiplexing might lead to 323 incorrect behavior. 325 Example: Multiplexing media descriptions over a single Datagram 326 Congestion Control Protocol (DCCP) transport [RFC5762] is not 327 recommended since DCCP being a connection oriented protocol doesn't 328 allow multiple connections on the same 5-tuple. 330 v=0 331 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com 332 s= 333 c=IN IP4 client.biloxi.example.com 334 t=0 0 335 m=video 5004 DCCP/RTP/AVP 99 336 a=rtpmap:99 h261/9000 337 a=dccp-service-code:SC=x52545056 338 a=setup:passive 339 a=connection:new 340 m=video 5004 DCCP/RTP/AVP 100 341 a=rtpmap:100 h261/9000 342 a=dccp-service-code:SC=x5254504f 343 a=setup:passive 344 a=connection:new 346 4.3. Category: IDENTICAL 348 The attributes and their associated values (if any) in the IDENTICAL 349 category MUST be repeated across all the media descriptions under 350 multiplexing. 352 Attributes such as rtcp-mux fall into this category. Since RTCP 353 reporting is done per RTP session, RTCP Multiplexing MUST be enabled 354 for both the audio and video "m=" lines if they are transported over 355 a single 5-tuple. 357 v=0 358 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com 359 s= 360 c=IN IP4 client.biloxi.example.com 361 t=0 0 362 m=audio 34567 RTP/AVP 97 363 a=rtcp-mux 364 m=video 34567 RTP/AVP 31 365 a=rtpmap:31 H261/90000 366 a=rtcp-mux 368 4.4. Category: SUM 370 The attributes in the SUM category can be set as they are normally 371 used but software using them in the multiplexing scenario MUST apply 372 the sum of all the attributes being multiplexed instead of trying to 373 use them independently. This is typically used for bandwidth or 374 other rate limiting attributes to the underlying transport. 376 The software parsing the SDP sample below, should use the aggregate 377 Application Specific (AS) bandwidth value from the individual media 378 descriptions to determine the AS value for the multiplexed session. 379 Thus the calculated AS value would be 256+64 kilobits per second for 380 the given example. 382 v=0 383 o=test 2890844526 2890842807 IN IP4 client.biloxi.example.com 384 c=IN IP4 client.biloxi.example.com 385 t=0 0 386 m=audio 49170 RTP/AVP 0 387 b=AS:64 388 m=video 51372 RTP/AVP 31 389 b=AS:256 391 4.5. Category: TRANSPORT 393 The attributes in the TRANSPORT category can be set normally for 394 multiple items in a multiplexed group but the software MUST pick the 395 one that's associated with the "m=" line whose information is used 396 for setting up the underlying transport. 398 In the example below, "a=crypto" attribute is defined for both the 399 audio and the video "m=" lines. The video media line's a=crypto 400 attribute is chosen since its mid value (bar) appears first in the 401 a=group:BUNDLE line. This is due to BUNDLE grouping semantic 402 [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values 403 from "m=" line corresponding to the mid appearing first on the 404 a=group:BUNDLE line to be considered for setting up the RTP 405 Transport. 407 v=0 408 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 409 s= 410 c=IN IP4 host.atlanta.example.com 411 t=0 0 412 a=group:BUNDLE bar foo 413 m=audio 49172 RTP/AVP 99 414 a=mid:foo 415 a=crypto:1 AES_CM_128_HMAC_SHA1_80 416 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32 417 a=rtpmap:99 iLBC/8000 418 m=video 51374 RTP/AVP 31 419 a=mid:bar 420 a=crypto:1 AES_CM_128_HMAC_SHA1_80 421 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 422 a=rtpmap:96 H261/90000 424 4.6. Category: INHERIT 426 The attributes in the INHERIT category encapsulate other SDP 427 attributes or parameters. These attributes inherit their 428 multiplexing characteristics from the attributes or parameters they 429 encapsulate. Such attributes are defined in [RFC3407], [RFC5939] and 430 [RFC6871] as part of a generic framework for indicating and 431 negotiating transport, media, and media format related capabilities 432 in the SDP. 434 The inheritance manifests itself when the encapsulated attribute or 435 parameter is being leveraged. In the case of SDP Capability 436 Negotiation [RFC5939] for example, this occurs when a capability 437 (encapsulating attribute) is used as part of a configuration; the 438 configuration inherits the multiplexing category of each of its 439 constituent (encapsulated) attributes and parameters. The inherited 440 attributes MUST be coherent in order to form a valid configuration 441 from a multiplexing point of view (see Section 14 for further 442 details). 444 v=0 445 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 446 s= 447 c=IN IP4 host.atlanta.example.com 448 t=0 0 449 m=video 3456 RTP/AVP 100 450 a=rtpmap:100 VP8/90000 451 a=fmtp:100 max-fr=30;max-fs=8040 452 a=sqn: 0 453 a=cdsc: 1 video RTP/AVP 100 454 a=cpar: a=rtcp-mux 455 m=video 3456 RTP/AVP 101 456 a=rtpmap:101 VP8/90000 457 a=fmtp:100 max-fr=15;max-fs=1200 458 a=cdsc: 2 video RTP/AVP 101 459 a=cpar: a=rtcp-mux 461 In the above example, the category IDENTICAL is inherited by the cpar 462 encapsulated rtcp-mux attribute. 464 4.7. Category: IDENTICAL-PER-PT 466 The attributes in the IDENTICAL-PER-PT category define the RTP 467 payload configuration on per Payload Type basis and MUST have 468 identical values across all the media descriptions for a given RTP 469 Payload Type when repeated. These Payload Types identify the same 470 codec configuration as defined in the Section 10.1.2 of 471 [I-D.ietf-mmusic-sdp-bundle-negotiation] under this context. 473 In the SDP example below, Payload Types 96 and 97 are repeated across 474 all the video "m=" lines and all the payload specific parameters (ex: 475 rtpmap, fmtp) are identical (Note: some line breaks included are due 476 to formatting only). 478 v=0 479 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 480 s= 481 c=IN IP4 host.atlanta.example.com 482 t=0 0 483 a=group:BUNDLE cam1 cam2 484 m=video 96 97 485 a=mid:cam1 486 a=rtpmap:96 H264/90000 487 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 488 max-mbps=108000; max-br=1000 489 a=rtpmap:97 H264/90000 490 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 491 max-mbps=7200; max-br=200 492 m=video 96 97 493 a=mid:cam2 494 a=rtpmap:96 H264/90000 495 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 496 max-mbps=108000; max-br=1000 497 a=rtpmap:97 H264/90000 498 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 499 max-mbps=7200; max-br=200 501 4.8. Category: SPECIAL 503 For the attributes in the SPECIAL category, the text in the 504 specification defining the attribute MUST be consulted for further 505 handling when multiplexed. 507 As an exampe, for the attribute extmap [RFC5285], the specification 508 defining the extension needs to be referred to understand the 509 multiplexing implications. 511 4.9. Category: TBD 513 The attributes in the TBD category have not been analyzed under the 514 proposed multiplexing framework and SHOULD NOT be multiplexed. 516 5. Analysis of Existing Attributes 518 This section analyzes attributes listed in [IANA], grouped under the 519 IETF document that defines them. 521 The "Level" column indicates whether the attribute is currently 522 specified as: 524 o S -- Session level 526 o M -- Media level 528 o B -- Both (Implies either a session level or a media level 529 attribute) 531 o SR -- Source-level (for a single SSRC) [RFC5576] 533 The "Mux Category" column identifies multiplexing category assigned 534 per attribute and the "Notes" column captures additional informative 535 details regarding the assigned category, wherever necessary. 537 5.1. RFC4566: SDP 539 [RFC4566] defines SDP that is intended for describing multimedia 540 sessions for the purposes of session announcement, session 541 invitation, and other forms of multimedia session initiation. 543 +-----------------+---------------------+-------+-------------------+ 544 | Name | Notes | Level | Mux Category | 545 +-----------------+---------------------+-------+-------------------+ 546 | sendrecv | Not impacted | B | NORMAL | 547 | | | | | 548 | sendonly | Not impacted | B | NORMAL | 549 | | | | | 550 | recvonly | Not impacted | B | NORMAL | 551 | | | | | 552 | inactive | Not impacted | B | NORMAL | 553 | | | | | 554 | cat | Not impacted | S | NORMAL | 555 | | | | | 556 | ptime | The attribute value | M | IDENTICAL-PER-PT | 557 | | MUST be same for a | | | 558 | | given codec | | | 559 | | configuration | | | 560 | | | | | 561 | maxptime | The attribute value | M | IDENTICAL-PER-PT | 562 | | MUST be same for a | | | 563 | | given codec | | | 564 | | configuration | | | 565 | | | | | 566 | orient | Not Impacted | M | NORMAL | 567 | | | | | 568 | framerate | The attribute value | M | IDENTICAL-PER-PT | 569 | | MUST be same for a | | | 570 | | given codec | | | 571 | | configuration | | | 572 | | | | | 573 | quality | Not Impacted | M | NORMAL | 574 | | | | | 575 | rtpmap | The attribute value | M | IDENTICAL-PER-PT | 576 | | MUST be same for a | | | 577 | | given codec | | | 578 | | configuration | | | 579 | | | | | 580 | fmtp | The attribute value | M | IDENTICAL-PER-PT | 581 | | MUST be same for a | | | 582 | | given codec | | | 583 | | configuration | | | 584 | | | | | 585 | keywds | Not impacted | S | NORMAL | 586 | | | | | 587 | type | Not Impacted | S | NORMAL | 588 | | | | | 589 | type:broadcast | Not Impacted | S | NORMAL | 590 | | | | | 591 | type:H332 | Not Impacted | S | NORMAL | 592 | | | | | 593 | type:meeting | Not Impacted | S | NORMAL | 594 | | | | | 595 | type:moderated | Not Impacted | S | NORMAL | 596 | | | | | 597 | type:test | Not Impacted | S | NORMAL | 598 | | | | | 599 | tool | Not Impacted | S | NORMAL | 600 | | | | | 601 | charset | Not Impacted | S | NORMAL | 602 | | | | | 603 | sdplang | Not Impacted | B | NORMAL | 604 | | | | | 605 | lang | Not Impacted | B | NORMAL | 606 | | | | | 607 +-----------------+---------------------+-------+-------------------+ 609 5.1 RFC4566 Attribute Analysis 611 5.2. RFC4585: RTP/AVPF 613 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 614 enables receivers to provide, statistically, more immediate feedback 615 to the senders and thus allows for short-term adaptation and 616 efficient feedback-based repair mechanisms to be implemented. 618 +----------+----------------------------+-------+-------------------+ 619 | Name | Notes | Level | Mux Category | 620 +----------+----------------------------+-------+-------------------+ 621 | rtcp-fb | Since RTCP feedback | M | IDENTICAL-PER-PT | 622 | | attributes are Payload | | | 623 | | Type (PT) scoped, their | | | 624 | | values MUST be identical | | | 625 | | for a given PT across the | | | 626 | | multiplexed "m=" lines. | | | 627 | | | | | 628 +----------+----------------------------+-------+-------------------+ 630 5.2 RFC4585 Attribute Analysis 632 5.3. RFC5761: Multiplexing RTP and RTCP 634 [RFC5761] discusses issues that arise when multiplexing RTP data 635 packets and RTP Control Protocol (RTCP) packets on a single UDP port. 636 It describes when such multiplexing is and is not appropriate, and it 637 explains how the SDP can be used to signal multiplexed sessions. 639 +-----------+----------------------------------+-------+------------+ 640 | Name | Notes | Level | Mux | 641 | | | | Category | 642 +-----------+----------------------------------+-------+------------+ 643 | rtcp-mux | RTP and RTCP Multiplexing | M | IDENTICAL | 644 | | affects the entire RTP session | | | 645 | | | | | 646 +-----------+----------------------------------+-------+------------+ 648 5.3 RFC5761 Attribute Analysis 650 5.4. RFC3312: Integration of Resource Management and SIP 652 [RFC3312] defines a generic framework for preconditions, which are 653 extensible through IANA registration. This document also discusses 654 how network quality of service can be made a precondition for 655 establishment of sessions initiated by the Session Initiation 656 Protocol (SIP). These preconditions require that the participant 657 reserve network resources before continuing with the session. 659 +-------+-----------------------+-------+--------------+ 660 | Name | Notes | Level | Mux Category | 661 +-------+-----------------------+-------+--------------+ 662 | des | Refer to notes below | M | CAUTION | 663 | | | | | 664 | conf | Refer to notes below | M | CAUTION | 665 | | | | | 666 | curr | Refer to notes below | M | CAUTION | 667 | | | | | 668 +-------+-----------------------+-------+--------------+ 670 5.4 RFC3312 Attribute Analysis 672 NOTE: A mismatched set of preconditions across media descriptions 673 results in Session establishment failures due to inability to meet 674 right resource reservations requested. 676 5.5. RFC4574: SDP Label Attribute 678 [RFC4574] defines a new SDP media-level attribute: "label". The 679 "label" attribute carries a pointer to a media stream in the context 680 of an arbitrary network application that uses SDP. The sender of the 681 SDP document can attach the "label" attribute to a particular media 682 stream or streams. The application can then use the provided pointer 683 to refer to each particular media stream in its context. 685 +--------+---------------+-------+--------------+ 686 | Name | Notes | Level | Mux Category | 687 +--------+---------------+-------+--------------+ 688 | label | Not Impacted | M | NORMAL | 689 | | | | | 690 +--------+---------------+-------+--------------+ 692 5.5 RFC4574 Attribute Analysis 694 5.6. RFC5432: QOS Mechanism Selection in SDP 696 [RFC5432] defines procedures to negotiate QOS mechanisms using the 697 SDP offer/answer model. 699 +----------------+-----------------------+-------+--------------+ 700 | Name | Notes | Level | Mux Category | 701 +----------------+-----------------------+-------+--------------+ 702 | qos-mech-send | Refer to Section 10 | B | TRANSPORT | 703 | | | | | 704 | qos-mech-recv | Refer to Section 10 | B | TRANSPORT | 705 | | | | | 706 +----------------+-----------------------+-------+--------------+ 708 5.6 RFC5432 Attribute Analysis 710 5.7. RFC4568: SDP Security Descriptions 712 [RFC4568] defines a SDP cryptographic attribute for unicast media 713 streams. The attribute describes a cryptographic key and other 714 parameters that serve to configure security for a unicast media 715 stream in either a single message or a roundtrip exchange. 717 +---------+------------------------------------+-------+------------+ 718 | Name | Notes | Level | Mux | 719 | | | | Category | 720 +---------+------------------------------------+-------+------------+ 721 | crypto | crypto attribute MUST be the one | M | TRANSPORT | 722 | | that corresponds to the "m=" line | | | 723 | | chosen for setting up the | | | 724 | | underlying transport flow | | | 725 | | | | | 726 +---------+------------------------------------+-------+------------+ 728 5.7 RFC4568 Attribute Analysis 730 5.8. RFC5762: RTP over DCCP 732 RTP is a widely used transport for real-time multimedia on IP 733 networks. DCCP is a transport protocol that provides desirable 734 services for real-time applications. [RFC5762] specifies a mapping 735 of RTP onto DCCP, along with associated signaling, such that real- 736 time applications can make use of the services provided by DCCP. 738 +--------------------+-------------------------+---------+----------+ 739 | Name | Notes | Current | Mux | 740 | | | | Category | 741 +--------------------+-------------------------+---------+----------+ 742 | dccp-service-code | If RFC6773 is not being | M | CAUTION | 743 | | used in addition to | | | 744 | | RFC5762, the port in | | | 745 | | the "m=" line is a DCCP | | | 746 | | port. DCCP being a | | | 747 | | connection oriented | | | 748 | | protocol does not allow | | | 749 | | multiple connections on | | | 750 | | the same 5-tuple | | | 751 | | | | | 752 +--------------------+-------------------------+---------+----------+ 754 5.8 RFC5762 Attribute Analysis 756 NOTE: If RFC6773 is being used in addition to RFC5762 and provided 757 that DCCP-in-UDP layer has additional demultiplexing, then it can be 758 possible to use different DCCP service codes for each DCCP flow, 759 given each uses a different DCCP port. Although doing so might 760 conflict with the media type of the "m=" line. None of this is 761 standardized yet and it wouldn't work as explained. Hence performing 762 multiplexing is not recommended even in this alternate scenario. 764 5.9. RFC6773: DCCP-UDP Encapsulation 766 [RFC6773] specifies an alternative encapsulation of DCCP, referred to 767 as DCCP-UDP. This encapsulation allows DCCP to be carried through 768 the current generation of Network Address Translation (NAT) middle 769 boxes without modification of those middle boxes. 771 +------------+-----------------------------------+-------+----------+ 772 | Name | Notes | Level | Mux | 773 | | | | Category | 774 +------------+-----------------------------------+-------+----------+ 775 | dccp-port | Multiplexing is not recommended | M | CAUTION | 776 | | due to potential conflict between | | | 777 | | the port used for DCCP | | | 778 | | en/decapsulation and the RTP | | | 779 | | | | | 780 +------------+-----------------------------------+-------+----------+ 782 5.9 RFC6773 Attribute Analysis 784 NOTE: RFC6773 is about tunneling DCCP in UDP, with the UDP port being 785 the port of the DCCP en-/de-capsulation service. This encapsulation 786 allows arbitrary DCCP packets to be encapsulated and the DCCP port 787 chosen can conflict with the port chosen for the RTP traffic. For 788 multiplexing several DCCP-in-UDP encapsulations on the same UDP port 789 with no RTP traffic on the same port implies collapsing several DCCP 790 port spaces together. This can or cannot work depending on the 791 nature of DCCP encapsulation and ports choices thus rendering it to 792 be very application dependent. 794 5.10. RFC5506: Reduced-Size RTCP in RTP Profile 796 [RFC5506] discusses benefits and issues that arise when allowing RTCP 797 packets to be transmitted with reduced size. 799 +-------------+--------------------------------+-------+------------+ 800 | Name | Notes | Level | Mux | 801 | | | | Category | 802 +-------------+--------------------------------+-------+------------+ 803 | rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL | 804 | | entire RTP session | | | 805 | | | | | 806 +-------------+--------------------------------+-------+------------+ 808 5.10 RFC5506 Attribute Analysis 810 5.11. RFC6787: Media Resource Control Protocol Version 2 812 The Media Resource Control Protocol Version 2 (MRCPv2) allows client 813 hosts to control media service resources such as speech synthesizers, 814 recognizers, verifiers, and identifiers residing in servers on the 815 network. MRCPv2 is not a "stand-alone" protocol -- it relies on 816 other protocols, such as the SIP, to coordinate MRCPv2 clients and 817 servers, and manage session between them, and SDP to describe, 818 discover, and exchange capabilities. It also depends on SIP and SDP 819 to establish the media sessions and associated parameters between the 820 media source or sink and the media server. Once this is done, the 821 MRCPv2 exchange operates over the control session established above, 822 allowing the client to control the media processing resources on the 823 speech resource server. [RFC6787] defines attributes for this 824 purpose. 826 +-----------+---------------+-------+--------------+ 827 | Name | Notes | Level | Mux Category | 828 +-----------+---------------+-------+--------------+ 829 | resource | Not Impacted | M | NORMAL | 830 | | | | | 831 | channel | Not Impacted | M | NORMAL | 832 | | | | | 833 | cmid | Not Impacted | M | NORMAL | 834 | | | | | 835 +-----------+---------------+-------+--------------+ 837 5.11 RFC6787 Attribute Analysis 839 5.12. RFC5245: ICE 841 [RFC5245] describes a protocol for NAT traversal for UDP-based 842 multimedia sessions established with the offer/answer model. ICE 843 makes use of the Session Traversal Utilities for NAT (STUN) protocol 844 and its extension, Traversal Using Relay NAT (TURN). ICE can be used 845 by any protocol utilizing the offer/answer model, such as the SIP. 847 +--------------------+-------------------------+-------+------------+ 848 | Name | Notes | Level | Mux | 849 | | | | Category | 850 +--------------------+-------------------------+-------+------------+ 851 | ice-lite | Not Impacted | S | NORMAL | 852 | | | | | 853 | ice-options | Not Impacted | S | NORMAL | 854 | | | | | 855 | ice-mismatch | Not Impacted | S | NORMAL | 856 | | | | | 857 | ice-pwd | ice-pwd MUST be the one | B | TRANSPORT | 858 | | that corresponds to the | | | 859 | | "m=" line chosen for | | | 860 | | setting up the | | | 861 | | underlying transport | | | 862 | | flow | | | 863 | | | | | 864 | ice-ufrag | ice-ufrag MUST be the | B | TRANSPORT | 865 | | one that corresponds to | | | 866 | | the "m=" line chosen | | | 867 | | for setting up the | | | 868 | | underlying transport | | | 869 | | flow | | | 870 | | | | | 871 | candidate | ice candidate MUST be | M | TRANSPORT | 872 | | the one that | | | 873 | | corresponds to the "m=" | | | 874 | | line chosen for setting | | | 875 | | up the underlying | | | 876 | | transport flow | | | 877 | | | | | 878 | remote-candidates | ice remote candidate | M | TRANSPORT | 879 | | MUST be the one that | | | 880 | | corresponds to the "m=" | | | 881 | | line chosen for setting | | | 882 | | up the underlying | | | 883 | | transport flow | | | 884 | | | | | 885 +--------------------+-------------------------+-------+------------+ 887 5.12 RFC5245 Attribute Analysis 889 5.13. RFC5285: RTP Header Extensions 891 [RFC5285] provides a general mechanism to use the header extension 892 feature of RTP. It provides the option to use a small number of 893 small extensions in each RTP packet, where the universe of possible 894 extensions is large and registration is de-centralized. The actual 895 extensions in use in a session are signaled in the setup information 896 for that session. 898 +---------+--------------------------------------+-------+----------+ 899 | Name | Notes | Level | Mux | 900 | | | | Category | 901 +---------+--------------------------------------+-------+----------+ 902 | extmap | Refer to the document defining the | B | SPECIAL | 903 | | specific RTP Extension | | | 904 | | | | | 905 +---------+--------------------------------------+-------+----------+ 907 5.13 RFC5285 Attribute Analysis 909 5.14. RFC3605: RTCP attribute in SDP 911 Originally, SDP assumed that RTP and RTCP were carried on consecutive 912 ports. However, this is not always true when NATs are involved. 913 [RFC3605] specifies an early mechanism to indicate the RTCP port. 915 +-------+--------------------------------------+-------+------------+ 916 | Name | Notes | Level | Mux | 917 | | | | Category | 918 +-------+--------------------------------------+-------+------------+ 919 | rtcp | RTCP Port MUST be the one that | M | TRANSPORT | 920 | | corresponds to the "m=" line chosen | | | 921 | | for setting up the underlying | | | 922 | | transport flow. | | | 923 | | | | | 924 +-------+--------------------------------------+-------+------------+ 926 5.14 RFC3605 Attribute Analysis 928 5.15. RFC5576: Source-Specific SDP Attributes 930 [RFC5576] defines a mechanism to describe RTP media sources, which 931 are identified by their synchronization source (SSRC) identifiers, in 932 SDP, to associate attributes with these sources, and to express 933 relationships among sources. It also defines several source-level 934 attributes that can be used to describe properties of media sources. 936 +----------------+----------------------+-------+-------------------+ 937 | Name | Notes | Level | Mux Category | 938 +----------------+----------------------+-------+-------------------+ 939 | ssrc | Refer to Notes below | M | NORMAL | 940 | | | | | 941 | ssrc-group | Refer to Section 9 | M | NORMAL | 942 | | for specific | | | 943 | | analysis of the | | | 944 | | grouping semantics | | | 945 | | | | | 946 | cname | Not Impacted | SR | NORMAL | 947 | | | | | 948 | previous-ssrc | Refer to notes below | SR | NORMAL | 949 | | | | | 950 | fmtp | The attribute value | SR | IDENTICAL-PER-PT | 951 | | MUST be same for a | | | 952 | | given codec | | | 953 | | configuration | | | 954 | | | | | 955 +----------------+----------------------+-------+-------------------+ 957 5.15 RFC5576 Attribute Analysis 959 NOTE: If SSRCs are repeated across "m=" lines being multiplexed, they 960 MUST all represent the same underlying RTP Source. 962 5.16. RFC7273: RTP Clock Source Signalling 964 [RFC7273] specifies SDP signalling that identifies timestamp 965 reference clock sources and SDP signalling that identifies the media 966 clock sources in a multimedia session. 968 +--------------------+---------------+-------+--------------+ 969 | Name | Notes | Level | Mux Category | 970 +--------------------+---------------+-------+--------------+ 971 | ts-refclk | Not Impacted | B | NORMAL | 972 | | | | | 973 | mediaclk | Not Impacted | B | NORMAL | 974 | | | | | 975 | ts-refclk:ntp | Not Impacted | B | NORMAL | 976 | | | | | 977 | ts-refclk:ptp | Not Impacted | B | NORMAL | 978 | | | | | 979 | ts-refclk:gps | Not Impacted | B | NORMAL | 980 | | | | | 981 | ts-refclk:gal | Not Impacted | B | NORMAL | 982 | | | | | 983 | ts-refclk:glonass | Not Impacted | B | NORMAL | 984 | | | | | 985 | ts-refclk:local | Not Impacted | B | NORMAL | 986 | | | | | 987 | ts-refclk:private | Not Impacted | B | NORMAL | 988 | | | | | 989 | mediaclk:sender | Not Impacted | B | NORMAL | 990 | | | | | 991 | mediaclk:direct | Not Impacted | B | NORMAL | 992 | | | | | 993 | mediaclk:IEEE1722 | Not Impacted | B | NORMAL | 994 | | | | | 995 +--------------------+---------------+-------+--------------+ 997 5.16 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 image, 1005 something that may consume large amounts of memory and processing 1006 power. The document also helps to maintain an optimal bitrate for 1007 video as only the image size that is desired by the receiver is 1008 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 5.17 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 SDP. 1026 +--------------------+---------------+-------+--------------+ 1027 | Name | Notes | Level | Mux Category | 1028 +--------------------+---------------+-------+--------------+ 1029 | duplication-delay | Not Impacted | B | NORMAL | 1030 | | | | | 1031 +--------------------+---------------+-------+--------------+ 1033 5.18 RFC7197 Attribute Analysis 1035 5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting 1037 [RFC7266] defines an RTCP Extended Report (XR) Block including two 1038 new segment types and associated SDP parameters that allow the 1039 reporting of mean opinion score (MOS) Metrics for use in a range of 1040 RTP applications. 1042 +-------------+---------------+-------+--------------+ 1043 | Name | Notes | Level | Mux Category | 1044 +-------------+---------------+-------+--------------+ 1045 | calgextmap | Not Impacted | B | NORMAL | 1046 | | | | | 1047 +-------------+---------------+-------+--------------+ 1049 5.19 RFC7266 Attribute Analysis 1051 5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions 1053 [RFC6285] describes a method using the existing RTP and RTCP 1054 machinery that reduces the acquisition delay. In this method, an 1055 auxiliary unicast RTP session carrying the Reference Information to 1056 the receiver precedes or accompanies the multicast stream. This 1057 unicast RTP flow can be transmitted at a faster than natural bitrate 1058 to further accelerate the acquisition. The motivating use case for 1059 this capability is multicast applications that carry real-time 1060 compressed audio and video. 1062 +---------------+-------------------+-------+--------------+ 1063 | Name | Notes | Level | Mux Category | 1064 +---------------+-------------------+-------+--------------+ 1065 | rams-updates | Not recommended | M | CAUTION | 1066 | | | | | 1067 +---------------+-------------------+-------+--------------+ 1069 5.20 RFC6285 Attribute Analysis 1071 5.21. RFC6230: Media Control Channel Framework 1073 [RFC6230] describes a framework and protocol for application 1074 deployment where the application programming logic and media 1075 processing are distributed. This implies that application 1076 programming logic can seamlessly gain access to appropriate resources 1077 that are not co-located on the same physical network entity. The 1078 framework uses SIP to establish an application-level control 1079 mechanism between application servers and associated external servers 1080 such as media servers. 1082 +---------+---------------+-------+--------------+ 1083 | Name | Notes | Level | Mux Category | 1084 +---------+---------------+-------+--------------+ 1085 | cfw-id | Not Impacted | M | NORMAL | 1086 | | | | | 1087 +---------+---------------+-------+--------------+ 1089 5.21 RFC6230 Attribute Analysis 1091 5.22. RFC6364: SDP Elements for FEC Framework 1093 [RFC6364] specifies the use of SDP to describe the parameters 1094 required to signal the Forward Error Correction (FEC) Framework 1095 Configuration Information between the sender(s) and receiver(s). 1096 This document also provides examples that show the semantics for 1097 grouping multiple source and repair flows together for the 1098 applications that simultaneously use multiple instances of the FEC 1099 Framework. 1101 +------------------+-----------------------------+-------+----------+ 1102 | Name | Notes | Level | Mux | 1103 | | | | Category | 1104 +------------------+-----------------------------+-------+----------+ 1105 | fec-source-flow | Refer to the document | M | SPECIAL | 1106 | | defining specific FEC | | | 1107 | | Scheme | | | 1108 | | | | | 1109 | fec-repair-flow | Refer to the document | M | SPECIAL | 1110 | | defining specific FEC | | | 1111 | | Scheme | | | 1112 | | | | | 1113 | repair-window | Refer to the document | M | SPECIAL | 1114 | | defining specific FEC | | | 1115 | | Scheme | | | 1116 | | | | | 1117 +------------------+-----------------------------+-------+----------+ 1119 5.22 RFC6364 Attribute Analysis 1121 5.23. RFC4796: Content Attribute 1123 [RFC4796] defines a new SDP media-level attribute, 'content'. The 1124 'content' attribute defines the content of the media stream to a more 1125 detailed level than the media description line. The sender of an SDP 1126 session description can attach the 'content' attribute to one or more 1127 media streams. The receiving application can then treat each media 1128 stream differently (e.g., show it on a big or small screen) based on 1129 its content. 1131 +----------+---------------+-------+--------------+ 1132 | Name | Notes | Level | Mux Category | 1133 +----------+---------------+-------+--------------+ 1134 | content | Not Impacted | M | NORMAL | 1135 | | | | | 1136 +----------+---------------+-------+--------------+ 1138 5.23 RFC4796 Attribute Analysis 1140 5.24. RFC3407: SDP Simple Capability Declaration 1142 [RFC3407] defines a set of SDP attributes that enables SDP to provide 1143 a minimal and backwards compatible capability declaration mechanism. 1145 +----------+------------------------+-------+--------------+ 1146 | Name | Notes | Level | Mux Category | 1147 +----------+------------------------+-------+--------------+ 1148 | sqn | Not Impacted | B | NORMAL | 1149 | | | | | 1150 | cdsc | Not Impacted. | B | NORMAL | 1151 | | | | | 1152 | cpar | Refer to Section 14 | B | INHERIT | 1153 | | | | | 1154 | cparmin | Refer to notes below | B | SPECIAL | 1155 | | | | | 1156 | cparmax | Refer to notes below | B | SPECIAL | 1157 | | | | | 1158 +----------+------------------------+-------+--------------+ 1160 5.24 RFC3407 Attribute Analysis 1162 NOTE: The attributes (a=cparmin and a=cparmax) define minimum and 1163 maximum numerical values associated with the attributes described in 1164 a=cpar. 1166 Since the cpar attribute can either define a 'b=' attribute or any 1167 'a=' attribute, the multiplexing category depends on actual attribute 1168 being encapsulated and the implications of the numerical values 1169 assigned. Hence it is recommended to consult the specification 1170 defining attributes (cparmin/cparmax) to further analyze their 1171 behavior under multiplexing. 1173 5.25. RFC6284: Port Mapping between Unicast and Multicast RTP Sessions 1175 [RFC6284] presents a port mapping solution that allows RTP receivers 1176 to choose their own ports for an auxiliary unicast session in RTP 1177 applications using both unicast and multicast services. The solution 1178 provides protection against denial-of-service or packet amplification 1179 attacks that could be used to cause one or more RTP packets to be 1180 sent to a victim client. 1182 +------------------+-----------------------------+-------+----------+ 1183 | Name | Notes | Level | Mux | 1184 | | | | Category | 1185 +------------------+-----------------------------+-------+----------+ 1186 | portmapping-req | Not recommended, if port | M | CAUTION | 1187 | | mapping is required by the | | | 1188 | | application | | | 1189 | | | | | 1190 +------------------+-----------------------------+-------+----------+ 1192 5.25 RFC6284 Attribute Analysis 1194 5.26. RFC6714: MSRP-CEMA 1196 [RFC6714] defines a Message Session Relay Protocol (MSRP) extension, 1197 Connection Establishment for Media Anchoring (CEMA). Support of this 1198 extension is optional. The extension allows middle boxes to anchor 1199 the MSRP connection, without the need for middle boxes to modify the 1200 MSRP messages; thus, it also enables secure end-to-end MSRP 1201 communication in networks where such middle boxes are deployed. This 1202 document also defines a SDP attribute, 'msrp-cema', that MSRP 1203 endpoints use to indicate support of the CEMA extension. 1205 +------------+-----------------------+-------+--------------+ 1206 | Name | Notes | Level | Mux Category | 1207 +------------+-----------------------+-------+--------------+ 1208 | msrp-cema | Refer to notes below | M | TBD | 1209 | | | | | 1210 +------------+-----------------------+-------+--------------+ 1212 5.26 RFC6714 Attribute Analysis 1214 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1215 there exists no publicly available specification that defines 1216 procedures for multiplexing/demultiplexing MRSP flows over a single 1217 5-tuple. Once such a specification is available, the multiplexing 1218 categories assignments for the attributes in this section could be 1219 revisited. 1221 5.27. RFC4583: SDP Format for BFCP Streams 1223 [RFC4583] document specifies how to describe Binary Floor Control 1224 Protocol (BFCP) streams in SDP descriptions. User agents using the 1225 offer/answer model to establish BFCP streams use this format in their 1226 offers and answers. 1228 +------------+-----------------------+-------+--------------+ 1229 | Name | Notes | Level | Mux Category | 1230 +------------+-----------------------+-------+--------------+ 1231 | floorctrl | Refer to notes below | M | TBD | 1232 | | | | | 1233 | confid | Not Impacted | M | NORMAL | 1234 | | | | | 1235 | userid | Not Impacted | M | NORMAL | 1236 | | | | | 1237 | floorid | Not Impacted | M | NORMAL | 1238 | | | | | 1239 +------------+-----------------------+-------+--------------+ 1241 5.27 RFC4583 Attribute Analysis 1243 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1244 there exists no publicly available specification that defines 1245 procedures for multiplexing/demultiplexing BFCP streams over a single 1246 5-tuple. Once such a specification is available, the multiplexing 1247 categories assignments for the attributes in this section could be 1248 revisited. 1250 5.28. RFC5547: SDP Offer/Answer for File Transfer 1252 [RFC5547] provides a mechanism to negotiate the transfer of one or 1253 more files between two endpoints by using the SDP offer/answer model 1254 specified in [RFC3264]. 1256 +-------------------+-----------------------+-------+--------------+ 1257 | Name | Notes | Level | Mux Category | 1258 +-------------------+-----------------------+-------+--------------+ 1259 | file-selector | Refer to notes below | M | TBD | 1260 | | | | | 1261 | file-transfer-id | Refer to notes below | M | TBD | 1262 | | | | | 1263 | file-disposition | Refer to notes below | M | TBD | 1264 | | | | | 1265 | file-date | Refer to notes below | M | TBD | 1266 | | | | | 1267 | file-icon | Refer to notes below | M | TBD | 1268 | | | | | 1269 | file-range | Refer to notes below | M | TBD | 1270 | | | | | 1271 +-------------------+-----------------------+-------+--------------+ 1273 5.28 RFC5547 Attribute Analysis 1275 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1276 there exists no publicly available specification that defines 1277 procedures for multiplexing/demultiplexing MRSP flows over a single 1278 5-tuple. Once such a specification is available, the multiplexing 1279 categories assignments for attributes in this section could be 1280 revisited. 1282 5.29. RFC6849: SDP and RTP Media Loopback Extension 1284 [RFC6849] adds new SDP media types and attributes, which enable 1285 establishment of media sessions where the media is looped back to the 1286 transmitter. Such media sessions will serve as monitoring and 1287 troubleshooting tools by providing the means for measurement of more 1288 advanced Voice over IP (VoIP), Real-time Text, and Video over IP 1289 performance metrics. 1291 +---------------------+-----------------+-------+-------------------+ 1292 | Name | Notes | Level | Mux Category | 1293 +---------------------+-----------------+-------+-------------------+ 1294 | loopback rtp-pkt- | The attribute | M | IDENTICAL-PER-PT | 1295 | loopback | value MUST be | | | 1296 | | same for a | | | 1297 | | given codec | | | 1298 | | configuration | | | 1299 | | | | | 1300 | loopback rtp-media- | The attribute | M | IDENTICAL-PER-PT | 1301 | loopback | value MUST be | | | 1302 | | same for a | | | 1303 | | given codec | | | 1304 | | configuration | | | 1305 | | | | | 1306 | loopback-source | Not Impacted | M | NORMAL | 1307 | | | | | 1308 | loopback-mirror | Not Impacted | M | NORMAL | 1309 | | | | | 1310 +---------------------+-----------------+-------+-------------------+ 1312 5.29 RFC6849 Analysis 1314 5.30. RFC5760: RTCP with Unicast Feedback 1316 [RFC5760] specifies an extension to RTCP to use unicast feedback to a 1317 multicast sender. The proposed extension is useful for single-source 1318 multicast sessions such as Source-Specific Multicast (SSM) 1319 communication where the traditional model of many-to-many group 1320 communication is either not available or not desired. 1322 +---------------+------------------------------+-------+------------+ 1323 | Name | Notes | Level | Mux | 1324 | | | | Category | 1325 +---------------+------------------------------+-------+------------+ 1326 | rtcp-unicast | The attribute MUST be | M | IDENTICAL | 1327 | | reported across all "m=" | | | 1328 | | lines multiplexed | | | 1329 | | | | | 1330 +---------------+------------------------------+-------+------------+ 1332 5.30 RFC5760 Attribute Analysis 1334 5.31. RFC3611: RTCP XR 1336 [RFC3611] defines the Extended Report (XR) packet type for RTCP, and 1337 defines how the use of XR packets can be signaled by an application 1338 if it employs the Session Description Protocol (SDP). 1340 +----------+---------------+-------+--------------+ 1341 | Name | Notes | Level | Mux Category | 1342 +----------+---------------+-------+--------------+ 1343 | rtcp-xr | Not Impacted | B | NORMAL | 1344 | | | | | 1345 +----------+---------------+-------+--------------+ 1347 5.31 RFC3611 Attribute Analysis 1349 5.32. RFC5939: SDP Capability Negotiation 1351 [RFC5939] defines a general SDP Capability Negotiation framework. It 1352 also specifies how to provide attributes and transport protocols as 1353 capabilities and negotiate them using the framework. Extensions for 1354 other types of capabilities (e.g., media types and media formats) may 1355 be provided in other documents. 1357 +---------+-----------------------+-------+--------------+ 1358 | Name | Notes | Level | Mux Category | 1359 +---------+-----------------------+-------+--------------+ 1360 | pcfg | Refer to Section 14 | M | SPECIAL | 1361 | | | | | 1362 | acfg | Refer to Section 14 | M | SPECIAL | 1363 | | | | | 1364 | csup | Not Impacted | B | NORMAL | 1365 | | | | | 1366 | creq | Not Impacted | B | NORMAL | 1367 | | | | | 1368 | acap | Refer to Section 14 | B | INHERIT | 1369 | | | | | 1370 | tcap | Refer to Section 14 | B | INHERIT | 1371 | | | | | 1372 | cap-v0 | Not Impacted | B | NORMAL | 1373 | | | | | 1374 +---------+-----------------------+-------+--------------+ 1376 5.32 RFC5939 Attribute Analysis 1378 5.33. RFC6871: SDP Media Capabilities Negotiation 1380 SDP capability negotiation provides a general framework for 1381 indicating and negotiating capabilities in SDP. The base framework 1382 defines only capabilities for negotiating transport protocols and 1383 attributes. [RFC6871] extends the framework by defining media 1384 capabilities that can be used to negotiate media types and their 1385 associated parameters. 1387 +---------+-----------------------+-------+-------------------+ 1388 | Name | Notes | Level | Mux Category | 1389 +---------+-----------------------+-------+-------------------+ 1390 | rmcap | Refer to Section 14 | B | IDENTICAL-PER-PT | 1391 | | | | | 1392 | omcap | Not Impacted | B | NORMAL | 1393 | | | | | 1394 | mfcap | Refer to Section 14 | B | IDENTICAL-PER-PT | 1395 | | | | | 1396 | mscap | Refer to Section 14 | B | INHERIT | 1397 | | | | | 1398 | lcfg | Refer to Section 14 | B | SPECIAL | 1399 | | | | | 1400 | sescap | Refer to notes below | S | CAUTION | 1401 | | | | | 1402 | med-v0 | Not Impacted | S | NORMAL | 1403 | | | | | 1404 +---------+-----------------------+-------+-------------------+ 1406 5.33 RFC6871 - Attribute Analysis 1408 NOTE: The "sescap" attribute is not recommended for use with 1409 multiplexing. The reason is that it requires the use of unique 1410 configuration numbers across the entire SDP (per [RFC6871]) as 1411 opposed to within a media description only (per [RFC5939]). As 1412 described in Section 14, the use of identical configuration numbers 1413 between multiplexed (bundled) media descriptions is the default way 1414 of indicating compatible configurations in a bundle. 1416 5.34. RFC7006: Miscellaneous Capabilities Negotiation SDP 1418 [RFC7006] extends the SDP capability negotiation framework to allow 1419 endpoints to negotiate three additional SDP capabilities. In 1420 particular, this memo provides a mechanism to negotiate bandwidth 1421 ("b=" line), connection data ("c=" line), and session or media titles 1422 ("i=" line for each session or media). 1424 +----------+-----------------------------------+-------+------------+ 1425 | Name | Notes | Level | Mux | 1426 | | | | Category | 1427 +----------+-----------------------------------+-------+------------+ 1428 | bcap | Inherit the category SUM as | B | INHERIT | 1429 | | applicable to b= attribute | | | 1430 | | | | | 1431 | bcap-v0 | Not Impacted | B | NORMAL | 1432 | | | | | 1433 | ccap | The connection address type MUST | B | IDENTICAL | 1434 | | be identical across all the | | | 1435 | | multiplexed "m=" lines | | | 1436 | | | | | 1437 | ccap-v0 | Not Impacted | B | NORMAL | 1438 | | | | | 1439 | icap | Not Impacted | B | NORMAL | 1440 | | | | | 1441 | icap-v0 | Not Impacted | B | NORMAL | 1442 | | | | | 1443 +----------+-----------------------------------+-------+------------+ 1445 5.34 RFC7006 - Attribute Analysis 1447 5.35. RFC4567: Key Management Extensions for SDP and RTSP 1449 [RFC4567] defines general extensions for SDP and Real Time Streaming 1450 Protocol (RTSP) to carry messages, as specified by a key management 1451 protocol, in order to secure the media. These extensions are 1452 presented as a framework, to be used by one or more key management 1453 protocols. As such, their use is meaningful only when complemented 1454 by an appropriate key management protocol. 1456 +-----------+----------------------------------+-------+------------+ 1457 | Name | Notes | Level | Mux | 1458 | | | | Category | 1459 +-----------+----------------------------------+-------+------------+ 1460 | key-mgmt | Key management protocol MUST be | B | IDENTICAL | 1461 | | identical across all the "m=" | | | 1462 | | lines | | | 1463 | | | | | 1464 | mikey | Key management protocol MUST be | B | IDENTICAL | 1465 | | identical across all the "m=" | | | 1466 | | lines | | | 1467 | | | | | 1468 +-----------+----------------------------------+-------+------------+ 1470 5.35 RFC4567 Attribute Analysis 1472 5.36. RFC4572: Comedia over TLS in SDP 1474 [RFC4572] specifies how to establish secure connection-oriented media 1475 transport sessions over the Transport Layer Security (TLS) protocol 1476 using SDP. It defines a new SDP protocol identifier, 'TCP/TLS'. It 1477 also defines the syntax and semantics for an SDP 'fingerprint' 1478 attribute that identifies the certificate that will be presented for 1479 the TLS session. This mechanism allows media transport over TLS 1480 connections to be established securely, so long as the integrity of 1481 session descriptions is assured. 1483 +--------------+-------------------------------+-------+------------+ 1484 | Name | Notes | Level | Mux | 1485 | | | | Category | 1486 +--------------+-------------------------------+-------+------------+ 1487 | fingerprint | fingerprint value MUST be the | B | TRANSPORT | 1488 | | one that corresponds to the | | | 1489 | | "m=" line chosen for setting | | | 1490 | | up the underlying transport | | | 1491 | | flow | | | 1492 | | | | | 1493 +--------------+-------------------------------+-------+------------+ 1495 5.36 RFC4572 Attribute Analysis 1497 5.37. RFC4570: SDP Source Filters 1499 [RFC4570] describes how to adapt SDP to express one or more source 1500 addresses as a source filter for one or more destination "connection" 1501 addresses. It defines the syntax and semantics for an SDP "source- 1502 filter" attribute that may reference either IPv4 or IPv6 address(es) 1503 as either an inclusive or exclusive source list for either multicast 1504 or unicast destinations. In particular, an inclusive source-filter 1505 can be used to specify a Source-Specific Multicast (SSM) session. 1507 +----------------+-----------------------------+-------+------------+ 1508 | Name | Notes | Level | Mux | 1509 | | | | Category | 1510 +----------------+-----------------------------+-------+------------+ 1511 | source-filter | The attribute MUST be | B | IDENTICAL | 1512 | | repeated across all "m=" | | | 1513 | | lines multiplexed | | | 1514 | | | | | 1515 +----------------+-----------------------------+-------+------------+ 1517 5.37 RFC4570 Attribute Analysis 1519 5.38. RFC6128: RTCP Port for Multicast Sessions 1521 SDP has an attribute that allows RTP applications to specify an 1522 address and a port associated with the RTCP traffic. In RTP-based 1523 source-specific multicast (SSM) sessions, the same attribute is used 1524 to designate the address and the RTCP port of the Feedback Target in 1525 the SDP description. However, the RTCP port associated with the SSM 1526 session itself cannot be specified by the same attribute to avoid 1527 ambiguity, and thus, is required to be derived from the "m=" line of 1528 the media description. Deriving the RTCP port from the "m=" line 1529 imposes an unnecessary restriction. [RFC6128] removes this 1530 restriction by introducing a new SDP attribute. 1532 +-----------------+----------------------------+-------+------------+ 1533 | Name | Notes | Level | Mux | 1534 | | | | Category | 1535 +-----------------+----------------------------+-------+------------+ 1536 | multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL | 1537 | | be identical across all | | | 1538 | | the "m=" lines | | | 1539 | | | | | 1540 +-----------------+----------------------------+-------+------------+ 1542 5.38 RFC6128 Attribute Analysis 1544 5.39. RFC6189: ZRTP 1546 [RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman 1547 exchange to agree on a session key and parameters for establishing 1548 unicast SRTP sessions for (VoIP applications. 1550 +------------+---------------------------------+-------+------------+ 1551 | Name | Notes | Level | Mux | 1552 | | | | Category | 1553 +------------+---------------------------------+-------+------------+ 1554 | zrtp-hash | zrtp-hash attribute MUST be the | M | TRANSPORT | 1555 | | one that corresponds to the | | | 1556 | | "m=" line chosen for setting up | | | 1557 | | the underlying transport flow | | | 1558 | | | | | 1559 +------------+---------------------------------+-------+------------+ 1561 5.39 RFC6189 Attribute Analysis 1563 5.40. RFC4145: Connection-Oriented Media 1565 [RFC4145] describes how to express media transport over TCP using 1566 SDP. It defines the SDP 'TCP' protocol identifier, the SDP 'setup' 1567 attribute, which describes the connection setup procedure, and the 1568 SDP 'connection' attribute, which handles connection reestablishment. 1570 +-------------+--------------------------------+-------+------------+ 1571 | Name | Notes | Level | Mux | 1572 | | | | Category | 1573 +-------------+--------------------------------+-------+------------+ 1574 | setup | The setup attribute MUST be | B | TRANSPORT | 1575 | | the one that corresponds to | | | 1576 | | the "m=" line chosen for | | | 1577 | | setting up the underlying | | | 1578 | | transport flow. | | | 1579 | | | | | 1580 | connection | The connection attribute MUST | B | TRANSPORT | 1581 | | be the one that corresponds to | | | 1582 | | the "m=" line chosen for | | | 1583 | | setting up the underlying | | | 1584 | | transport flow. | | | 1585 | | | | | 1586 +-------------+--------------------------------+-------+------------+ 1588 5.40 RFC4145 Attribute Analysis 1590 5.41. RFC6947: The SDP altc Attribute 1592 [RFC6947] proposes a mechanism that allows the same SDP offer to 1593 carry multiple IP addresses of different address families (e.g., IPv4 1594 and IPv6). The proposed attribute, the "altc" attribute, solves the 1595 backward-compatibility problem that plagued Alternative Network 1596 Address Types (ANAT) due to their syntax. 1598 +-------+--------------------------------------+-------+------------+ 1599 | Name | Notes | Level | Mux | 1600 | | | | Category | 1601 +-------+--------------------------------------+-------+------------+ 1602 | altc | The IP Address and port MUST be the | M | TRANSPORT | 1603 | | one that corresponds to the "m=" | | | 1604 | | line chosen for setting up the | | | 1605 | | underlying transport flow | | | 1606 | | | | | 1607 +-------+--------------------------------------+-------+------------+ 1609 5.41 RFC6947 Attribute Analysis 1611 5.42. RFC7195: SDP Extension for Circuit Switched Bearers in PSTN 1613 [RFC7195] describes use cases, requirements, and protocol extensions 1614 for using SDP offer/answer model for establishing audio and video 1615 media streams over circuit-switched bearers in the Public Switched 1616 Telephone Network (PSTN). 1618 +--------------------------+-------------------+-------+------------+ 1619 | Name | Notes | Level | Mux | 1620 | | | | Category | 1621 +--------------------------+-------------------+-------+------------+ 1622 | cs-correlation:callerid | Refer to notes | M | TBD | 1623 | | below | | | 1624 | | | | | 1625 | cs-correlation:uuie | Refer to notes | M | TBD | 1626 | | below | | | 1627 | | | | | 1628 | cs-correlation:dtmf | Refer to notes | M | TBD | 1629 | | below | | | 1630 | | | | | 1631 | cs-correlation:external | Refer to notes | M | TBD | 1632 | | below | | | 1633 | | | | | 1634 +--------------------------+-------------------+-------+------------+ 1636 5.42 RFC7195 Attribute Analysis 1638 NOTE: [RFC7195] defines SDP attributes for establishing audio and 1639 video media streams over circuit-switched bearers by defining a new 1640 nettype value "PSTN". However, section 7.2 of 1641 [I-D.ietf-mmusic-sdp-bundle-negotiation] requires the "c=" line 1642 nettype value of "IN". If in future there exists a specification 1643 that defines procedures to multiplex media streams over nettype 1644 "PSTN", the multiplexing categories for attributes in this section 1645 could be revisited. 1647 5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP) 1649 [RFC7272] defines a new RTCP Packet Type and an RTCP Extended Report 1650 (XR) Block Type to be used for achieving Inter-Destination Media 1651 Synchronization (IDMS). 1653 +------------+---------------+-------+--------------+ 1654 | Name | Notes | Level | Mux Category | 1655 +------------+---------------+-------+--------------+ 1656 | rtcp-idms | Not Impacted | M | NORMAL | 1657 | | | | | 1658 +------------+---------------+-------+--------------+ 1660 5.43 RFC7272 Attribute Analysis 1662 5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP 1663 Attributes 1665 [RFC5159] provides descriptions of SDP attributes used by the Open 1666 Mobile Alliance's Broadcast Service and Content Protection 1667 specification. 1669 +---------------------+-----------------------+-------+-------------+ 1670 | Name | Notes | Level | Mux | 1671 | | | | Category | 1672 +---------------------+-----------------------+-------+-------------+ 1673 | bcastversion | Not Impacted | S | NORMAL | 1674 | | | | | 1675 | stkmstream | Not Impacted | B | NORMAL | 1676 | | | | | 1677 | SRTPAuthentication | Needs further | M | TBD | 1678 | | analysis | | | 1679 | | | | | 1680 | SRTPROCTxRate | Needs further | M | TBD | 1681 | | analysis | | | 1682 | | | | | 1683 +---------------------+-----------------------+-------+-------------+ 1685 5.44 RFC5159 Attribute Analysis 1687 5.45. RFC6193: Media Description for IKE in SDP 1689 [RFC6193] specifies how to establish a media session that represents 1690 a virtual private network using the Session Initiation Protocol for 1691 the purpose of on-demand media/application sharing between peers. It 1692 extends the protocol identifier of SDP so that it can negotiate use 1693 of the Internet Key Exchange Protocol (IKE) for media sessions in the 1694 SDP offer/answer model. 1696 +-------------------+----------------------------+-------+----------+ 1697 | Name | Notes | Level | Mux | 1698 | | | | Category | 1699 +-------------------+----------------------------+-------+----------+ 1700 | ike-setup | Unlikely to use IKE in the | B | CAUTION | 1701 | | context of multiplexing | | | 1702 | | | | | 1703 | psk-fingerprint | Unlikely to use IKE in the | B | CAUTION | 1704 | | context of multiplexing | | | 1705 | | | | | 1706 | ike-esp | Unlikely to use IKE in the | B | CAUTION | 1707 | | context of multiplexing | | | 1708 | | | | | 1709 | ike-esp-udpencap | Unlikely to use IKE in the | B | CAUTION | 1710 | | context of multiplexing | | | 1711 | | | | | 1712 +-------------------+----------------------------+-------+----------+ 1714 5.45 RFC6193 Attribute Analysis 1716 5.46. RFC2326: Real Time Streaming Protocol 1718 The Real Time Streaming Protocol, or RTSP, is an application-level 1719 protocol for control over the delivery of data with real-time 1720 properties. RTSP provides an extensible framework to enable 1721 controlled, on-demand delivery of real-time data, such as audio and 1722 video. 1724 +----------+------------------------------------+-------+-----------+ 1725 | Name | Notes | Level | Mux | 1726 | | | | Category | 1727 +----------+------------------------------------+-------+-----------+ 1728 | etag | RTSP is not supported for RTP | B | CAUTION | 1729 | | Stream multiplexing | | | 1730 | | | | | 1731 | range | RTSP is not supported for RTP | B | CAUTION | 1732 | | Stream multiplexing | | | 1733 | | | | | 1734 | control | RTSP is not supported for RTP | B | CAUTION | 1735 | | Stream multiplexing | | | 1736 | | | | | 1737 | mtag | RTSP is not supported for RTP | B | CAUTION | 1738 | | Stream multiplexing | | | 1739 | | | | | 1740 +----------+------------------------------------+-------+-----------+ 1742 5.46 RFC2326 Attribute Analysis 1744 NOTE: [RFC2326] defines SDP attributes that are applicable in the 1745 declarative usage of SDP alone. For purposes of this document, only 1746 the Offer/Answer usage of SDP is considered as mandated by 1747 [I-D.ietf-mmusic-sdp-bundle-negotiation]. 1749 5.47. RFC6064: SDP and RTSP Extensions for 3GPP 1751 The Packet-switched Streaming Service (PSS) and the Multimedia 1752 Broadcast/Multicast Service (MBMS) defined by 3GPP use SDP and RTSP 1753 with some extensions. [RFC6064] provides information about these 1754 extensions and registers the RTSP and SDP extensions with IANA. 1756 +--------------------------------+---------------+-------+----------+ 1757 | Name | Notes | Level | Mux | 1758 | | | | Category | 1759 +--------------------------------+---------------+-------+----------+ 1760 | X-predecbufsize | Refer to | M | CAUTION | 1761 | | notes below | | | 1762 | | | | | 1763 | X-initpredecbufperiod | Refer to | M | CAUTION | 1764 | | notes below | | | 1765 | | | | | 1766 | X-initpostdecbufperiod | Refer to | M | CAUTION | 1767 | | notes below | | | 1768 | | | | | 1769 | X-decbyterate | Refer to | M | CAUTION | 1770 | | notes below | | | 1771 | | | | | 1772 | 3gpp-videopostdecbufsize | Refer to | M | CAUTION | 1773 | | notes below | | | 1774 | | | | | 1775 | framesize | Refer to | M | CAUTION | 1776 | | notes below | | | 1777 | | | | | 1778 | 3GPP-Integrity-Key | Refer to | S | CAUTION | 1779 | | notes below | | | 1780 | | | | | 1781 | 3GPP-SDP-Auth | Refer to | S | CAUTION | 1782 | | notes below | | | 1783 | | | | | 1784 | 3GPP-SRTP-Config | Refer to | M | CAUTION | 1785 | | notes below | | | 1786 | | | | | 1787 | alt | Refer to | M | CAUTION | 1788 | | notes below | | | 1789 | | | | | 1790 | alt-default-id | Refer to | M | CAUTION | 1791 | | notes below | | | 1792 | | | | | 1793 | alt-group | Refer to | S | CAUTION | 1794 | | notes below | | | 1795 | | | | | 1796 | 3GPP-Adaptation-Support | Refer to | M | CAUTION | 1797 | | notes below | | | 1798 | | | | | 1799 | 3GPP-Asset-Information | Refer to | B | CAUTION | 1800 | | notes below | | | 1801 | | | | | 1802 | mbms-mode | Refer to | B | CAUTION | 1803 | | notes below | | | 1804 | | | | | 1805 | mbms-flowid | Refer to | M | CAUTION | 1806 | | notes below | | | 1807 | | | | | 1808 | mbms-repair | Refer to | B | CAUTION | 1809 | | notes below | | | 1810 | | | | | 1811 | 3GPP-QoE-Metrics | Refer to | M | CAUTION | 1812 | | notes below | | | 1813 | | | | | 1814 | 3GPP-QoE-Metrics:Corruption | Refer to | M | CAUTION | 1815 | duration | notes below | | | 1816 | | | | | 1817 | 3GPP-QoE-Metrics:Rebuffering | Refer to | M | CAUTION | 1818 | duration | notes below | | | 1819 | | | | | 1820 | 3GPP-QoE-Metrics:Initial | Refer to | M | CAUTION | 1821 | buffering duration | notes below | | | 1822 | | | | | 1823 | 3GPP-QoE-Metrics:Successive | Refer to | M | CAUTION | 1824 | loss of RTP packets | notes below | | | 1825 | | | | | 1826 | 3GPP-QoE-Metrics:Frame rate | Refer to | M | CAUTION | 1827 | deviation | notes below | | | 1828 | | | | | 1829 | 3GPP-QoE-Metrics:Jitter | Refer to | M | CAUTION | 1830 | duration | notes below | | | 1831 | | | | | 1832 | 3GPP-QoE-Metrics:Content | Refer to | B | CAUTION | 1833 | Switch Time | notes below | | | 1834 | | | | | 1835 | 3GPP-QoE-Metrics:Average Codec | Refer to | M | CAUTION | 1836 | Bitrate | notes below | | | 1837 | | | | | 1838 | 3GPP-QoE-Metrics:Codec | Refer to | M | CAUTION | 1839 | Information | notes below | | | 1840 | | | | | 1841 | 3GPP-QoE-Metrics:Buffer Status | Refer to | M | CAUTION | 1842 | | notes below | | | 1843 | | | | | 1844 +--------------------------------+---------------+-------+----------+ 1846 5.47 RFC6064 Attribute Analysis 1848 NOTE: [RFC6064] defines SDP attributes that are applicable in the 1849 declarative usage of SDP alone. For purposes of this document, only 1850 the Offer/Answer usage of SDP is considered as mandated by 1851 [I-D.ietf-mmusic-sdp-bundle-negotiation]. 1853 5.48. RFC3108: ATM SDP 1855 [RFC3108] describes conventions for using SDP described for 1856 controlling ATM Bearer Connections, and any associated ATM Adaptation 1857 Layer (AAL). 1859 +------------------------+--------------------+-------+-------------+ 1860 | Name | Notes | Level | Mux | 1861 | | | | Category | 1862 +------------------------+--------------------+-------+-------------+ 1863 | aalType | Refer to notes | B | CAUTION | 1864 | | below | | | 1865 | eecid | Refer to notes | B | CAUTION | 1866 | | below | | | 1867 | capability | Refer to notes | B | CAUTION | 1868 | | below | | | 1869 | qosClass | Refer to notes | B | CAUTION | 1870 | | below | | | 1871 | bcob | Refer to notes | B | CAUTION | 1872 | | below | | | 1873 | stc | Refer to notes | B | CAUTION | 1874 | | below | | | 1875 | upcc | Refer to notes | B | CAUTION | 1876 | | below | | | 1877 | atmQOSparms | Refer to notes | B | CAUTION | 1878 | | below | | | 1879 | atmTrfcDesc | Refer to notes | B | CAUTION | 1880 | | below | | | 1881 | abrParms | Refer to notes | B | CAUTION | 1882 | | below | | | 1883 | abrSetup | Refer to notes | B | CAUTION | 1884 | | below | | | 1885 | bearerType | Refer to notes | B | CAUTION | 1886 | | below | | | 1887 | lij | Refer to notes | B | CAUTION | 1888 | | below | | | 1889 | anycast | Refer to notes | B | CAUTION | 1890 | | below | | | 1891 | cache | Refer to notes | B | CAUTION | 1892 | | below | | | 1893 | bearerSigIE | Refer to notes | B | CAUTION | 1894 | | below | | | 1895 | aalApp | Refer to notes | B | CAUTION | 1896 | | below | | | 1897 | cbrRate | Refer to notes | B | CAUTION | 1898 | | below | | | 1899 | sbc | Refer to notes | B | CAUTION | 1900 | | below | | | 1901 | clkrec | Refer to notes | B | CAUTION | 1902 | | below | | | 1903 | fec | Refer to notes | B | CAUTION | 1904 | | below | | | 1905 | prtfl | Refer to notes | B | CAUTION | 1906 | | below | | | 1907 | structure | Refer to notes | B | CAUTION | 1908 | | below | | | 1909 | cpsSDUsize | Refer to notes | B | CAUTION | 1910 | | below | | | 1911 | aal2CPS | Refer to notes | B | CAUTION | 1912 | | below | | | 1913 | aal2CPSSDUrate | Refer to notes | B | CAUTION | 1914 | | below | | | 1915 | aal2sscs3661unassured | Refer to notes | B | CAUTION | 1916 | | below | | | 1917 | aal2sscs3661assured | Refer to notes | B | CAUTION | 1918 | | below | | | 1919 | aal2sscs3662 | Refer to notes | B | CAUTION | 1920 | | below | | | 1921 | aal5sscop | Refer to notes | B | CAUTION | 1922 | | below | | | 1923 | atmmap | Refer to notes | B | CAUTION | 1924 | | below | | | 1925 | silenceSupp | Refer to notes | B | CAUTION | 1926 | | below | | | 1927 | ecan | Refer to notes | B | CAUTION | 1928 | | below | | | 1929 | gc | Refer to notes | B | CAUTION | 1930 | | below | | | 1931 | profileDesc | Refer to notes | B | CAUTION | 1932 | | below | | | 1933 | vsel | Refer to notes | B | CAUTION | 1934 | | below | | | 1935 | dsel | Refer to notes | B | CAUTION | 1936 | | below | | | 1937 | fsel | Refer to notes | B | CAUTION | 1938 | | below | | | 1939 | onewaySel | Refer to notes | B | CAUTION | 1940 | | below | | | 1941 | codecconfig | Refer to notes | B | CAUTION | 1942 | | below | | | 1943 | isup_usi | Refer to notes | B | CAUTION | 1944 | | below | | | 1945 | uiLayer1_Prot | Refer to notes | B | CAUTION | 1946 | | below | | | 1947 | chain | Refer to notes | B | CAUTION | 1948 | | below | | | 1949 | | | | | 1950 +------------------------+--------------------+-------+-------------+ 1952 5.48 RFC3108 Attribute Analysis 1954 NOTE: RFC3108 describes conventions for using SDP for characterizing 1955 ATM bearer connections using an AAL1, AAL2 or AAL5 adaptation layers. 1956 For AAL1, AAL2 and AAL5, bearer connections can be used to transport 1957 single media streams. In addition, for AAL1 and AAL2, multiple media 1958 streams can be multiplexed into a bearer connection. For all 1959 adaptation types (AAL1, AAL2 and AAL5), bearer connections can be 1960 bundled into a single media group. In all cases addressed by 1961 RFC3108, a real-time media stream (voice, video, voiceband data, 1962 pseudo-wire, and others) or a multiplex of media streams is mapped 1963 directly into an ATM connection. RFC3108 does not address cases 1964 where ATM serves as a low-level transport pipe for IP packets which 1965 in turn can carry one or more real-time (e.g. VoIP) media sessions 1966 with a life-cycle different from that of the underlying ATM 1967 transport. 1969 5.49. 3GPP TS 26.114 1971 [R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and 1972 interaction 1973 +----------------------+-------------------------+-------+----------+ 1974 | Name | Notes | Level | Mux | 1975 | | | | Category | 1976 +----------------------+-------------------------+-------+----------+ 1977 | 3gpp_sync_info | Usage defined for the | M | NORMAL | 1978 | | IP Multimedia Subsystem | | | 1979 | | | | | 1980 | 3gpp_MaxRecvSDUSize | Usage defined for the | M | NORMAL | 1981 | | IP Multimedia Subsystem | | | 1982 | | | | | 1983 +----------------------+-------------------------+-------+----------+ 1985 5.49 3GPP TS 26.114 Attribute Analysis 1987 5.50. 3GPP TS 183.063 1989 [R3GPPTS183.063] Telecommunications and Internet converged Services 1990 and Protocols for Advanced Networking (TISPAN); 1992 +---------------------+---------------+-------+--------------+ 1993 | Name | Notes | Level | Mux Category | 1994 +---------------------+---------------+-------+--------------+ 1995 | PSCid | Not Impacted | S | NORMAL | 1996 | | | | | 1997 | bc_service | Not Impacted | S | NORMAL | 1998 | | | | | 1999 | bc_program | Not Impacted | S | NORMAL | 2000 | | | | | 2001 | bc_service_package | Not Impacted | S | NORMAL | 2002 | | | | | 2003 +---------------------+---------------+-------+--------------+ 2005 5.50 3GPP TS 183.063 Attribute Analysis 2007 5.51. 3GPP TS 24.182 2009 [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting 2010 tones 2011 +-------------+---------------------------------+-------+-----------+ 2012 | Name | Notes | Level | Mux | 2013 | | | | Category | 2014 +-------------+---------------------------------+-------+-----------+ 2015 | g.3gpp.cat | Usage defined for the IP | M | NORMAL | 2016 | | Multimedia Subsystem | | | 2017 | | | | | 2018 +-------------+---------------------------------+-------+-----------+ 2020 5.51 3GPP TS 24.182 Attribute Analysis 2022 5.52. 3GPP TS 24.183 2024 [R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing 2025 Signal 2027 +-------------+---------------------------------+-------+-----------+ 2028 | Name | Notes | Level | Mux | 2029 | | | | Category | 2030 +-------------+---------------------------------+-------+-----------+ 2031 | g.3gpp.crs | Usage defined for the IP | M | NORMAL | 2032 | | Multimedia Subsystem | | | 2033 | | | | | 2034 +-------------+---------------------------------+-------+-----------+ 2036 5.52 3GPP TS 24.183 Attribute Analysis 2038 5.53. 3GPP TS 24.229 2040 [R3GPPTS24.229] specifies IP multimedia call control protocol based 2041 on Session Initial protocol and Session Description Protocol. 2043 +------------------+---------------------------+-------+------------+ 2044 | Name | Notes | Level | Mux | 2045 | | | | Category | 2046 +------------------+---------------------------+-------+------------+ 2047 | secondary-realm | secondary-realm MUST be | M | TRANSPORT | 2048 | | the one that corresponds | | | 2049 | | to the "m=" line chosen | | | 2050 | | for setting up the | | | 2051 | | underlying transport flow | | | 2052 | | | | | 2053 | visited-realm | visited-realm MUST be the | M | TRANSPORT | 2054 | | one that corresponds to | | | 2055 | | the "m=" line chosen for | | | 2056 | | setting up the underlying | | | 2057 | | transport flow | | | 2058 | | | | | 2059 | omr-m-cksum | Not Impacted | M | NORMAL | 2060 | | | | | 2061 | omr-s-cksum | Not Impacted | M | NORMAL | 2062 | | | | | 2063 | omr-m-att | Not Impacted | M | NORMAL | 2064 | | | | | 2065 | omr-s-att | Not Impacted | M | NORMAL | 2066 | | | | | 2067 | omr-m-bw | Not Impacted | M | NORMAL | 2068 | | | | | 2069 | omr-s-bw | Not Impacted | M | NORMAL | 2070 | | | | | 2071 | omr-codecs | Not Impacted | M | NORMAL | 2072 | | | | | 2073 +------------------+---------------------------+-------+------------+ 2075 5.53 3GPP TS 24.229 Attribute Analysis 2077 5.54. ITU T.38 2079 [T.38] defines procedures for real-time Group 3 facsimile 2080 communications over IP networks. 2082 +------------------------+--------------------+-------+-------------+ 2083 | Name | Notes | Level | Mux | 2084 | | | | Category | 2085 +------------------------+--------------------+-------+-------------+ 2086 | T38FaxVersion | Refer to notes | M | TBD | 2087 | | below | | | 2088 | | | | | 2089 | T38MaxBitRate | Refer to notes | M | TBD | 2090 | | below | | | 2091 | | | | | 2092 | T38FaxFillBitRemoval | Refer to notes | M | TBD | 2093 | | below | | | 2094 | | | | | 2095 | T38FaxTranscodingMMR | Refer to notes | M | TBD | 2096 | | below | | | 2097 | | | | | 2098 | T38FaxTranscodingJBIG | Refer to notes | M | TBD | 2099 | | below | | | 2100 | | | | | 2101 | T38FaxRateManagement | Refer to notes | M | TBD | 2102 | | below | | | 2103 | | | | | 2104 | T38FaxMaxBuffer | Refer to notes | M | TBD | 2105 | | below | | | 2106 | | | | | 2107 | T38FaxMaxDatagram | Refer to notes | M | TBD | 2108 | | below | | | 2109 | | | | | 2110 | T38FaxUdpEC | Refer to notes | M | TBD | 2111 | | below | | | 2112 | | | | | 2113 | T38FaxMaxIFP | Refer to notes | M | TBD | 2114 | | below | | | 2115 | | | | | 2116 | T38FaxUdpECDepth | Refer to notes | M | TBD | 2117 | | below | | | 2118 | | | | | 2119 | T38FaxUdpFECMaxSpan | Refer to notes | M | TBD | 2120 | | below | | | 2121 | | | | | 2122 | T38ModemType | Refer to notes | M | TBD | 2123 | | below | | | 2124 | | | | | 2125 | T38VendorInfo | Refer to notes | M | TBD | 2126 | | below | | | 2127 | | | | | 2128 +------------------------+--------------------+-------+-------------+ 2130 5.54 ITU T.38 Attribute Analysis 2132 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 2133 there exists no publicly available specification that defines 2134 procedures for multiplexing/demultiplexing fax protocols flows over a 2135 single 5-tuple. Once such a specification is available, the 2136 multiplexing category assignments for the attributes in this section 2137 could be revisited. 2139 5.55. ITU-T Q.1970 2141 [Q.1970] defines Bearer Independent Call Control (BICC) IP bearer 2142 control protocol. 2144 +--------+---------------------------------------+-------+----------+ 2145 | Name | Notes | Level | Mux | 2146 | | | | Category | 2147 +--------+---------------------------------------+-------+----------+ 2148 | ipbcp | ipbcp version identifies type of IP | S | SPECIAL | 2149 | | bearer control protocol (IPBCP) | | | 2150 | | message used in BICC (ITU-T Q.1901) | | | 2151 | | environment which are limited to | | | 2152 | | single media payload. Refer to the | | | 2153 | | pertinent ITU-T specifications while | | | 2154 | | multiplexing | | | 2155 | | | | | 2156 +--------+---------------------------------------+-------+----------+ 2158 5.55 ITU-T Q.1970 Attribute Analysis 2160 5.56. ITU-T H.248.15 2162 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248 2163 package attribute 2164 +-----------+------------------------------------+-------+----------+ 2165 | Name | Notes | Level | Mux | 2166 | | | | Category | 2167 +-----------+------------------------------------+-------+----------+ 2168 | h248item | It is only applicable for | B | SPECIAL | 2169 | | signaling the inclusion of H.248 | | | 2170 | | extension packages to a gateway | | | 2171 | | via the local and remote | | | 2172 | | descriptors. The attribute itself | | | 2173 | | is unaffected by multiplexing, but | | | 2174 | | the packaged referenced in a | | | 2175 | | specific use of the attribute can | | | 2176 | | be impacted. Further analysis of | | | 2177 | | each package is needed to | | | 2178 | | determine if there is an issue. | | | 2179 | | This is only a concern in | | | 2180 | | environments using a decomposed | | | 2181 | | server/gateway with H.248 signaled | | | 2182 | | between them. The ITU-T will need | | | 2183 | | to do further analysis of various | | | 2184 | | packages when they specify how to | | | 2185 | | signal the use of multiplexing to | | | 2186 | | a gateway | | | 2187 | | | | | 2188 +-----------+------------------------------------+-------+----------+ 2190 5.56 ITU-T H.248.15 Attribute Analysis 2192 5.57. RFC4975: The Message Session Relay Protocol 2194 [RFC4975] the Message Session Relay Protocol, a protocol for 2195 transmitting a series of related instant messages in the context of a 2196 session. Message sessions are treated like any other media stream 2197 when set up via a rendezvous or session creation protocol such as the 2198 Session Initiation Protocol. 2200 +-----------------------+---------------------+-------+-------------+ 2201 | Name | Notes | Level | Mux | 2202 | | | | Category | 2203 +-----------------------+---------------------+-------+-------------+ 2204 | accept-types | Refer to notes | M | TBD | 2205 | | below | | | 2206 | | | | | 2207 | accept-wrapped-types | Refer to notes | M | TBD | 2208 | | below | | | 2209 | | | | | 2210 | max-size | Refer to notes | M | TBD | 2211 | | below | | | 2212 | | | | | 2213 | path | Refer to notes | M | TBD | 2214 | | below | | | 2215 | | | | | 2216 +-----------------------+---------------------+-------+-------------+ 2218 5.57 RFC4975 Attribute Analysis 2220 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 2221 there exists no publicly available specification that defines 2222 procedures for multiplexing/demultiplexing MRSP flows over a single 2223 5-tuple. Once such a specification is available, the multiplexing 2224 categories assignments for the attributes in this section could be 2225 revisited. 2227 5.58. Historical Attributes 2229 This section specifies analysis for the attributes that are included 2230 for historic usage alone by the [IANA]. 2232 +----------+----------------------+-------+--------------+ 2233 | Name | Notes | Level | Mux Category | 2234 +----------+----------------------+-------+--------------+ 2235 | rtpred1 | Historic attributes | M | CAUTION | 2236 | | | | | 2237 | rtpred2 | Historic attributes | M | CAUTION | 2238 | | | | | 2239 +----------+----------------------+-------+--------------+ 2241 5.58 Historical Attribute Analysis 2243 6. bwtype Attribute Analysis 2245 This section specifies handling of specific bandwidth attributes when 2246 used in multiplexing scenarios. 2248 6.1. RFC4566: SDP 2250 [RFC4566] defines SDP that is intended for describing multimedia 2251 sessions for the purposes of session announcement, session 2252 invitation, and other forms of multimedia session initiation. 2254 +------------+-----------------------------------+-------+----------+ 2255 | Name | Notes | Level | Mux | 2256 | | | | Category | 2257 +------------+-----------------------------------+-------+----------+ 2258 | bwtype:CT | Not Impacted | S | NORMAL | 2259 | | | | | 2260 | bwtype:AS | For the media level usage, the | B | SUM | 2261 | | aggregate of individual bandwidth | | | 2262 | | values is considered | | | 2263 | | | | | 2264 +------------+-----------------------------------+-------+----------+ 2266 6.1 RFC4566 bwtype Analysis 2268 6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth 2270 [RFC3556] defines an extension to SDP to specify two additional 2271 modifiers for the bandwidth attribute. These modifiers may be used 2272 to specify the bandwidth allowed for RTCP packets in a RTP session. 2274 +------------+-----------------------------------+-------+----------+ 2275 | Name | Notes | Level | Mux | 2276 | | | | Category | 2277 +------------+-----------------------------------+-------+----------+ 2278 | bwtype:RS | Session level usage represents | B | SUM | 2279 | | session aggregate and media level | | | 2280 | | usage indicates SUM of the | | | 2281 | | individual values while | | | 2282 | | multiplexing | | | 2283 | | | | | 2284 | bwtype:RR | Session level usage represents | B | SUM | 2285 | | session aggregate and media level | | | 2286 | | usage indicates SUM of the | | | 2287 | | individual values while | | | 2288 | | multiplexing | | | 2289 | | | | | 2290 +------------+-----------------------------------+-------+----------+ 2292 6.2 RFC3556 bwtype Analysis 2294 6.3. RFC3890: Bandwidth Modifier for SDP 2296 [RFC3890] defines SDP Transport Independent Application Specific 2297 Maximum (TIAS) bandwidth modifier that does not include transport 2298 overhead; instead an additional packet rate attribute is defined. 2299 The transport independent bit-rate value together with the maximum 2300 packet rate can then be used to calculate the real bit-rate over the 2301 transport actually used. 2303 +--------------+---------------------------------+-------+----------+ 2304 | Name | Notes | Level | Mux | 2305 | | | | Category | 2306 +--------------+---------------------------------+-------+----------+ 2307 | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL | 2308 | | defined under Offer/Answer | | | 2309 | | usage. | | | 2310 | | | | | 2311 | maxprate | The usage of TIAS and maxprate | B | SPECIAL | 2312 | | is not well defined under | | | 2313 | | multiplexing | | | 2314 | | | | | 2315 +--------------+---------------------------------+-------+----------+ 2317 6.3 RFC3890 bwtype Analysis 2319 NOTE: The intention of TIAS is that the media level bit-rate is 2320 multiplied with the known per-packet overhead for the selected 2321 transport and the maxprate value to determine the worst case bit-rate 2322 from the transport to more accurately capture the required usage. 2323 Summing TIAS values independently across "m=" lines and multiplying 2324 the computed sum with maxprate and the per-packet overhead would 2325 inflate the value significantly. Instead performing multiplication 2326 and adding the individual values is a more appropriate usage. 2328 7. rtcp-fb Attribute Analysis 2330 This section analyzes rtcp-fb SDP attributes. 2332 7.1. RFC4585: RTP/AVPF 2334 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 2335 enables receivers to provide, statistically, more immediate feedback 2336 to the senders and thus allows for short-term adaptation and 2337 efficient feedback-based repair mechanisms to be implemented. 2339 +----------+----------------------------+-------+-------------------+ 2340 | Name | Notes | Level | Mux Category | 2341 +----------+----------------------------+-------+-------------------+ 2342 | ack rpsi | The attribute value MUST | M | IDENTICAL-PER-PT | 2343 | | be same for a given codec | | | 2344 | | configuration | | | 2345 | | | | | 2346 | ack app | Feedback parameters MUST | M | SPECIAL | 2347 | | be handled in the app | | | 2348 | | specific way when | | | 2349 | | multiplexed | | | 2350 | | | | | 2351 | nack | The attribute value MUST | M | IDENTICAL-PER-PT | 2352 | | be same for a given codec | | | 2353 | | configuration | | | 2354 | | | | | 2355 | nack pli | The attribute value MUST | M | IDENTICAL-PER-PT | 2356 | | be same for a given codec | | | 2357 | | configuration | | | 2358 | | | | | 2359 | nack sli | The attribute value MUST | M | IDENTICAL-PER-PT | 2360 | | be same for a given codec | | | 2361 | | configuration | | | 2362 | | | | | 2363 | nack | The attribute value MUST | M | IDENTICAL-PER-PT | 2364 | rpsi | be same for a given codec | | | 2365 | | configuration | | | 2366 | | | | | 2367 | nack app | Feedback parameters MUST | M | SPECIAL | 2368 | | be handled in the app | | | 2369 | | specific way when | | | 2370 | | multiplexed | | | 2371 | | | | | 2372 | trr-int | The attribute value MUST | M | IDENTICAL-PER-PT | 2373 | | be same for a given codec | | | 2374 | | configuration | | | 2375 | | | | | 2376 +----------+----------------------------+-------+-------------------+ 2378 7.1 RFC4585 Attribute Analysis 2380 7.2. RFC5104: Codec Control Messages in AVPF 2382 [RFC5104] specifies a few extensions to the messages defined in the 2383 Audio-Visual Profile with Feedback (AVPF). They are helpful 2384 primarily in conversational multimedia scenarios where centralized 2385 multipoint functionalities are in use. However, some are also usable 2386 in smaller multicast environments and point-to-point calls. 2388 +------+--------------------------------+-------+-------------------+ 2389 | Name | Notes | Level | Mux Category | 2390 +------+--------------------------------+-------+-------------------+ 2391 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2392 | | same for a given codec | | | 2393 | | configuration | | | 2394 | | | | | 2395 +------+--------------------------------+-------+-------------------+ 2397 7.2 RFC5104 Attribute Analysis 2399 7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP Sessions 2400 (RAMS) 2402 [RFC6285] describes a method using the existing RTP and RTCP 2403 machinery that reduces the acquisition delay. In this method, an 2404 auxiliary unicast RTP session carrying the Reference Information to 2405 the receiver precedes or accompanies the multicast stream. This 2406 unicast RTP flow can be transmitted at a faster than natural bitrate 2407 to further accelerate the acquisition. The motivating use case for 2408 this capability is multicast applications that carry real-time 2409 compressed audio and video. 2411 +-------+-------------------------------+-------+-------------------+ 2412 | Name | Notes | Level | Mux Category | 2413 +-------+-------------------------------+-------+-------------------+ 2414 | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | 2415 | rai | same for a given codec | | | 2416 | | configuration | | | 2417 | | | | | 2418 +-------+-------------------------------+-------+-------------------+ 2420 7.3 RFC6285 Attribute Analysis 2422 7.4. RFC6679: ECN for RTP over UDP/IP 2424 [RFC6679] specifies how Explicit Congestion Notification (ECN) can be 2425 used with the RTP running over UDP, using the RTCP as a feedback 2426 mechanism. It defines a new RTCP Extended Report (XR) block for 2427 periodic ECN feedback, a new RTCP transport feedback message for 2428 timely reporting of congestion events, and a STUN extension used in 2429 the optional initialization method using ICE. 2431 +------------------+---------------------------+-------+------------+ 2432 | Name | Notes | Level | Mux | 2433 | | | | Category | 2434 +------------------+---------------------------+-------+------------+ 2435 | ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL | 2436 | | the RTP session level | | | 2437 | | | | | 2438 | nack ecn | This attribute enables | M | IDENTICAL | 2439 | | ECN at the RTP session | | | 2440 | | level | | | 2441 | | | | | 2442 +------------------+---------------------------+-------+------------+ 2444 7.4 RFC6679 Attribute Analysis 2446 7.5. RFC6642: Third-Party Loss Report 2448 In a large RTP session using the RTCP feedback mechanism defined in 2449 [RFC4585], a feedback target may experience transient overload if 2450 some event causes a large number of receivers to send feedback at 2451 once. This overload is usually avoided by ensuring that feedback 2452 reports are forwarded to all receivers, allowing them to avoid 2453 sending duplicate feedback reports. However, there are cases where 2454 it is not recommended to forward feedback reports, and this may allow 2455 feedback implosion. [RFC6642] memo discusses these cases and defines 2456 a new RTCP Third-Party Loss Report that can be used to inform 2457 receivers that the feedback target is aware of some loss event, 2458 allowing them to suppress feedback. Associated SDP signaling is also 2459 defined. 2461 +--------+------------------------------+-------+-------------------+ 2462 | Name | Notes | Level | Mux Category | 2463 +--------+------------------------------+-------+-------------------+ 2464 | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | 2465 | tllei | same for a given codec | | | 2466 | | configuration | | | 2467 | | | | | 2468 | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | 2469 | pslei | same for a given codec | | | 2470 | | configuration | | | 2471 | | | | | 2472 +--------+------------------------------+-------+-------------------+ 2474 7.5 RFC6642 Attribute Analysis 2476 7.6. RFC5104: Codec Control Messages in AVPF 2478 [RFC5104] specifies a few extensions to the messages defined in the 2479 Audio-Visual Profile with Feedback (AVPF). They are helpful 2480 primarily in conversational multimedia scenarios where centralized 2481 multipoint functionalities are in use. However, some are also usable 2482 in smaller multicast environments and point-to-point calls. 2484 +--------+------------------------------+-------+-------------------+ 2485 | Name | Notes | Level | Mux Category | 2486 +--------+------------------------------+-------+-------------------+ 2487 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2488 | fir | same for a given codec | | | 2489 | | configuration | | | 2490 | | | | | 2491 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2492 | tmmbr | same for a given codec | | | 2493 | | configuration | | | 2494 | | | | | 2495 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2496 | tstr | same for a given codec | | | 2497 | | configuration | | | 2498 | | | | | 2499 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2500 | vbcm | same for a given codec | | | 2501 | | configuration | | | 2502 | | | | | 2503 +--------+------------------------------+-------+-------------------+ 2505 7.6 RFC5104 Attribute Analysis 2507 8. group Attribute Analysis 2509 This section analyzes SDP "group" attribute semantics [RFC5888]. 2511 8.1. RFC5888: SDP Grouping Framework 2513 [RFC5888] defines a framework to group "m" lines in SDP for different 2514 purposes. 2516 +------------+---------------+-------+--------------+ 2517 | Name | Notes | Level | Mux Category | 2518 +------------+---------------+-------+--------------+ 2519 | group:LS | Not Impacted | S | NORMAL | 2520 | | | | | 2521 | group:FID | Not Impacted | S | NORMAL | 2522 | | | | | 2523 +------------+---------------+-------+--------------+ 2525 8.1 RFC5888 Attribute Analysis 2527 8.2. RFC3524: Mapping Media Streams to Resource Reservation Flows 2529 [RFC3524] defines an extension to the SDP grouping framework. It 2530 allows requesting a group of media streams to be mapped into a single 2531 resource reservation flow. The SDP syntax needed is defined, as well 2532 as a new "semantics" attribute called Single Reservation Flow (SRF). 2534 +------------+---------------+-------+--------------+ 2535 | Name | Notes | Level | Mux Category | 2536 +------------+---------------+-------+--------------+ 2537 | group:SRF | Not Impacted | S | NORMAL | 2538 | | | | | 2539 +------------+---------------+-------+--------------+ 2541 8.2 RFC3524 Attribute Analysis 2543 8.3. RFC4091: ANAT Semantics 2545 [RFC4091] defines ANAT semantics for the SDP grouping framework. The 2546 ANAT semantics allow alternative types of network addresses to 2547 establish a particular media stream. 2549 +-------------+------------------------------+-------+--------------+ 2550 | Name | Notes | Level | Mux Category | 2551 +-------------+------------------------------+-------+--------------+ 2552 | group:ANAT | ANAT semantics is obsoleted | S | CAUTION | 2553 | | | | | 2554 +-------------+------------------------------+-------+--------------+ 2556 8.3 RFC4091 Attribute Analysis 2558 8.4. RFC5956: FEC Grouping Semantics in SDP 2560 [RFC5956] defines the semantics for grouping the associated source 2561 and FEC-based (Forward Error Correction) repair flows in SDP. The 2562 semantics defined in the document are to be used with the SDP 2563 Grouping Framework [RFC5888]. These semantics allow the description 2564 of grouping relationships between the source and repair flows when 2565 one or more source and/or repair flows are associated in the same 2566 group, and they provide support for additive repair flows. SSRC- 2567 level (Synchronization Source) grouping semantics are also defined in 2568 this document for RTP streams using SSRC multiplexing. 2570 +---------------+---------------+-------+--------------+ 2571 | Name | Notes | Level | Mux Category | 2572 +---------------+---------------+-------+--------------+ 2573 | group:FEC-FR | Not Impacted | S | NORMAL | 2574 | | | | | 2575 +---------------+---------------+-------+--------------+ 2577 8.4 RFC5956 Attribute Analysis 2579 8.5. RFC5583: Signaling Media Decoding Dependency in SDP 2581 [RFC5583] defines semantics that allow for signaling the decoding 2582 dependency of different media descriptions with the same media type 2583 in SDP. This is required, for example, if media data is separated 2584 and transported in different network streams as a result of the use 2585 of a layered or multiple descriptive media coding process. 2587 +------------+--------------------------+-------+-------------------+ 2588 | Name | Notes | Level | Mux Category | 2589 +------------+--------------------------+-------+-------------------+ 2590 | group:DDP | Not Impacted | S | NORMAL | 2591 | | | | | 2592 | depend lay | The attribute value MUST | M | IDENTICAL-PER-PT | 2593 | | be same for a given | | | 2594 | | codec configuration | | | 2595 | | | | | 2596 | depend mdc | The attribute value MUST | M | IDENTICAL-PER-PT | 2597 | | be same for a given | | | 2598 | | codec configuration | | | 2599 | | | | | 2600 +------------+--------------------------+-------+-------------------+ 2602 8.5 RFC5583 Attribute Analysis 2604 8.6. RFC7104: Duplication Grouping Semantics in the SDP 2606 [RFC7104] defines the semantics for grouping redundant streams in 2607 SDP, The semantics defined in this document are to be used with the 2608 SDP Grouping Framework. Grouping semantics at the SSRC)level are 2609 also defined in this document for RTP streams using SSRC 2610 multiplexing. 2612 +------------+---------------+-------+--------------+ 2613 | Name | Notes | Level | Mux Category | 2614 +------------+---------------+-------+--------------+ 2615 | group:DUP | Not Impacted | S | NORMAL | 2616 | | | | | 2617 +------------+---------------+-------+--------------+ 2619 8.6 RFC7104 Attribute Analysis 2621 9. ssrc-group Attribute Analysis 2623 This section analyzes "ssrc-group" semantics. 2625 9.1. RFC5576: Source-Specific SDP Attributes 2627 [RFC5576] defines a mechanism to describe RTP media sources, which 2628 are identified by their synchronization source (SSRC) identifiers, in 2629 SDP, to associate attributes with these sources, and to express 2630 relationships among sources. It also defines several source-level 2631 attributes that can be used to describe properties of media sources. 2633 +--------------------+---------------+-------+--------------+ 2634 | Name | Notes | Level | Mux Category | 2635 +--------------------+---------------+-------+--------------+ 2636 | ssrc-group:FID | Not Impacted | SR | NORMAL | 2637 | | | | | 2638 | ssrc-group:FEC | Not Impacted | SR | NORMAL | 2639 | | | | | 2640 | ssrc-group:FEC-FR | Not Impacted | SR | NORMAL | 2641 | | | | | 2642 +--------------------+---------------+-------+--------------+ 2644 9.1 RFC5576 Attribute Analysis 2646 9.2. RFC7104: Duplication Grouping Semantics in the SDP 2648 [RFC7104] defines the semantics for grouping redundant streams in 2649 SDP. The semantics defined in this document are to be used with the 2650 SDP Grouping Framework. Grouping semantics at the Synchronization 2651 Source (SSRC) level are also defined in this document for RTP streams 2652 using SSRC multiplexing. 2654 +-----------------+---------------+-------+--------------+ 2655 | Name | Notes | Level | Mux Category | 2656 +-----------------+---------------+-------+--------------+ 2657 | ssrc-group:DUP | Not Impacted | SR | NORMAL | 2658 | | | | | 2659 +-----------------+---------------+-------+--------------+ 2661 9.2 RFC7104 Attribute Analysis 2663 10. QoS Mechanism Token Analysis 2665 This section analyzes QoS tokes specified with SDP. 2667 10.1. RFC5432: QoS Mechanism Selection in SDP 2669 [RFC5432] defines procedures to negotiate QOS mechanisms using the 2670 SDP offer/answer model. 2672 +-------+--------------------------------------+-------+------------+ 2673 | Name | Notes | Level | Mux | 2674 | | | | Category | 2675 +-------+--------------------------------------+-------+------------+ 2676 | rsvp | rsvp attribute MUST be the one that | B | TRANSPORT | 2677 | | corresponds to the "m=" line chosen | | | 2678 | | for setting up the underlying | | | 2679 | | transport flow | | | 2680 | | | | | 2681 | nsis | rsvp attribute MUST be the one that | B | TRANSPORT | 2682 | | corresponds to the "m=" line chosen | | | 2683 | | for setting up the underlying | | | 2684 | | transport | | | 2685 | | | | | 2686 +-------+--------------------------------------+-------+------------+ 2688 10.1 RFC5432 Attribute Analysis 2690 NOTE: A single Differentiated Services Code Point (DSCP) code point 2691 per flow being multiplexed doesn't impact multiplexing since QOS 2692 mechanisms are signaled/scoped per flow. For scenarios that involve 2693 having different DSCP code points for packets being transmitted over 2694 the same 5-tuple, issues as discussed in [RFC7657] need to be taken 2695 into consideration. 2697 11. k= Attribute Analysis 2698 11.1. RFC4566: SDP 2700 [RFC4566] defines SDP that is intended for describing multimedia 2701 sessions for the purposes of session announcement, session 2702 invitation, and other forms of multimedia session initiation. 2704 +------+-----------------------------------------+-------+----------+ 2705 | Name | Notes | Level | Mux | 2706 | | | | Category | 2707 +------+-----------------------------------------+-------+----------+ 2708 | k= | It is not recommended to use this | S | CAUTION | 2709 | | attribute under multiplexing | | | 2710 | | | | | 2711 +------+-----------------------------------------+-------+----------+ 2713 11.1 RFC4566 Attribute Analysis 2715 12. content Attribute Analysis 2717 12.1. RFC4796 2719 [RFC4796] defines a new SDP media-level attribute, 'content'. The 2720 'content' attribute defines the content of the media stream to a more 2721 detailed level than the media description line. The sender of an SDP 2722 session description can attach the 'content' attribute to one or more 2723 media streams. The receiving application can then treat each media 2724 stream differently (e.g., show it on a big or small screen) based on 2725 its content. 2727 +------------------+---------------+-------+--------------+ 2728 | Name | Notes | Level | Mux Category | 2729 +------------------+---------------+-------+--------------+ 2730 | content:slides | Not Impacted | M | NORMAL | 2731 | | | | | 2732 | content:speaker | Not Impacted | M | NORMAL | 2733 | | | | | 2734 | content:main | Not Impacted | M | NORMAL | 2735 | | | | | 2736 | content:sl | Not Impacted | M | NORMAL | 2737 | | | | | 2738 | content:alt | Not Impacted | M | NORMAL | 2739 | | | | | 2740 +------------------+---------------+-------+--------------+ 2742 12.1 RFC4796 Attribute Analysis 2744 13. Payload Formats 2746 13.1. RFC5109: RTP Payload Format for Generic FEC 2748 [RFC5109] describes a payload format for generic Forward Error 2749 Correction (FEC) for media data encapsulated in RTP. It is based on 2750 the exclusive-or (parity) operation. The payload format allows end 2751 systems to apply protection using various protection lengths and 2752 levels, in addition to using various protection group sizes to adapt 2753 to different media and channel characteristics. It enables complete 2754 recovery of the protected packets or partial recovery of the critical 2755 parts of the payload depending on the packet loss situation. 2757 +---------------------+--------------------------+-------+----------+ 2758 | Name | Notes | Level | Mux | 2759 | | | | Category | 2760 +---------------------+--------------------------+-------+----------+ 2761 | audio/ulpfec | Not recommended for | M | CAUTION | 2762 | | multiplexing due to | | | 2763 | | reuse of SSRCs | | | 2764 | | | | | 2765 | video/ulpfec | Not recommended for | M | CAUTION | 2766 | | multiplexing due to | | | 2767 | | reuse of SSRCs | | | 2768 | | | | | 2769 | text/ulpfec | Not recommended for | M | CAUTION | 2770 | | multiplexing due to | | | 2771 | | reuse of SSRCs | | | 2772 | | | | | 2773 | application/ulpfec | Not recommended for | M | CAUTION | 2774 | | multiplexing due to | | | 2775 | | reuse of SSRCs | | | 2776 | | | | | 2777 +---------------------+--------------------------+-------+----------+ 2779 13.1 RFC5109 Payload Format Analysis 2781 14. Multiplexing Considerations for Encapsulating Attributes 2783 This sections deals with recommendations for defining the 2784 multiplexing characteristics of the SDP attributes that encapsulate 2785 other SDP attributes/parameters. Such attributes as of today, for 2786 example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of 2787 a generic framework for indicating and negotiating transport, media, 2788 and media format related capabilities in the SDP. 2790 The behavior of such attributes under multiplexing is in turn defined 2791 by the multiplexing behavior of the attributes they encapsulate which 2792 are made known once the Offer/Answer negotiation process is 2793 completed. 2795 14.1. RFC3407: cpar Attribute Analysis 2797 [RFC3407] capability parameter attribute (a=cpar) encapsulates b= 2798 (bandwidth) or an a= attribute. For bandwidth attribute 2799 encapsulation, the category SUM is inherited. For the case of a= 2800 attribute, the category corresponding to the SDP attribute being 2801 encapsulated is inherited. 2803 v=0 2804 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2805 s= 2806 c=IN IP4 host.atlanta.example.com 2807 t=0 0 2808 m=video 3456 RTP/AVP 100 2809 a=rtpmap:100 VP8/90000 2810 a=sqn: 0 2811 a=cdsc: 1 video RTP/AVP 100 2812 a=cpar: a=rtcp-mux 2813 m=video 3456 RTP/AVP 101 2814 a=rtpmap:101 VP8/90000 2815 a=fmtp:100 max-fr=15;max-fs=1200 2816 a=cdsc: 2 video RTP/AVP 101 2817 a=cpar: a=rtcp-mux 2819 In the above example,the category IDENTICAL is inherited for the cpar 2820 encapsulated rtcp-mux attribute. 2822 14.2. RFC5939 Analysis 2824 [RFC5939] defines a general SDP capability negotiation framework. It 2825 also specifies how to provide transport protocols and SDP attributes 2826 as capabilities and negotiate them using the framework. 2828 For this purpose, [RFC5939] defines the following 2830 o A set of capabilities for the session and its associated media 2831 stream components, supported by each side. The attribute 2832 ("a=acap") defines how to list an attribute name and its 2833 associated value (if any) as a capability. The attribute 2834 ("a=tcap") defines how to list transport protocols (e.g., "RTP/ 2835 AVP") as capabilities. 2837 o A set of potential configurations ("a=pcfg") provided by the 2838 offerer to indicate which combinations of those capabilities can 2839 be used for the session and its associated media stream 2840 components. Potential configurations are not ready for use until 2841 fully negotiated. They provide an alternative that MAY be used, 2842 subject to SDP capability negotiation procedures. In particular 2843 the answerer MAY choose one of the potential configurations for 2844 use as part of the current Offer/Answer exchange. 2846 o An actual configuration ("a=acfg") for the session and its 2847 associated media stream components. The actual configuration 2848 identifies the potential configuration that was negotiated for 2849 use. Use of an actual configuration does not require any further 2850 negotiation. 2852 o A negotiation process that takes the current actual and the set of 2853 potential configurations (combinations of capabilities) as input 2854 and provides the negotiated actual configurations as output. In 2855 [RFC5939] the negotiation process is done independently for each 2856 media description. 2858 14.2.1. Recommendation: Procedures for Potential Configuration Pairing 2860 This section provides recommendations for entities generating and 2861 processing SDP under the generic capability negotiation framework as 2862 defined in [RFC5939] under the context of media stream multiplexing. 2864 These recommendations are provided for the purposes of enabling the 2865 Offerer to make sure that the generated potential configurations 2866 between the multiplexed streams can (easily) be negotiated to be 2867 consistent between those streams. In particular, the procedures aim 2868 to simplify Answerer's procedure to choose potential configurations 2869 that are consistent across all the multiplexed media descriptions. 2871 A potential configuration selects a set of attributes and parameters 2872 that become part of the media description when negotiated. When 2873 multiplexing media descriptions with potential configurations 2874 specified, there MAY be a need for coordinating this selection 2875 between multiplexed media descriptions to ensure the right 2876 multiplexing behavior. 2878 Although it is possible to analyze the various potential 2879 configurations in multiplexed media descriptions to find combinations 2880 that satisfy such constraints, it can quickly become complicated to 2881 do so. 2883 The procedures defined in [RFC5939] state that each potential 2884 configuration in the SDP has a unique configuration number, however 2885 the scope of uniqueness is limited to each media description. To 2886 make it simple for the answerer to chose valid combinations of 2887 potential configurations across media descriptions in a given bundle 2888 group, we provide a simple rule for constructing potential 2889 configurations 2891 o Let m-bundle be the set of media descriptions that form a given 2892 bundle . 2894 o Let m-bundle-pcfg be the set of media descriptions in m-bundle 2895 that include one or more potential configurations. 2897 o Each media description in m-bundle-pcfg MUST have at least one 2898 potential configuration with the same configuration number (e.g. 2899 "1"). 2901 o For each potential configuration with configuration number x in m- 2902 bundle-pcfg, the offerer MUST ensure that if the answerer chooses 2903 configuration number x in each of the media descriptions in m- 2904 bundle-pcfg, then the resulting SDP will have all multiplexing 2905 constraints satisfied for those media descriptions. 2907 o Since it is nearly impossible to define a generic mechanism for 2908 various capability extensions, this document does't provide 2909 procedures for dealing with the capability extension attributes. 2910 However, Section 14.3 provide analysis of media capability 2911 extension attributes as defined in [RFC6871]. 2913 The above allows the answerer to easily find multiplexing compatible 2914 combinations of potential configurations: The answerer simply choses 2915 a potential configuration (number) that is present in all of the 2916 media descriptions with potential configurations in the bundle. 2918 Note that it is still possible for the offerer to provide additional 2919 potential configurations with independent configuration numbers. The 2920 answerer will have to perform more complicated analysis to determine 2921 valid multiplexed combinations of those. 2923 14.2.1.1. Example: Transport Capability Multiplexing 2924 v=0 2925 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2926 s= 2927 c=IN IP4 host.atlanta.example.com 2928 t=0 0 2929 a=tcap:1 RTP/SAVPF 2930 a=tcap:2 RTP/SAVP 2931 a=group:BUNDLE audio video 2932 m=audio 2933 a=mid:audio 2934 a=pcfg:1 t=1 2935 a=pcfg:2 2936 m=video 2937 a=mid:video 2938 a=pcfg:1 t=1 2939 a=pcfg:2 t=2 2941 In the example above, the potential configurations that offer 2942 transport protocol capability of RTP/SAVPF has the same configuration 2943 number "1" in both the audio and video media descriptions. 2945 14.2.1.2. Example: Attribute Capability Multiplexing 2947 v=0 2948 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2949 s= 2950 c=IN IP4 host.atlanta.example.com 2951 t=0 0 2952 a=acap:1 a=rtcp-mux 2953 a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80 2954 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 2955 a=group:BUNDLE audio video 2956 m=audio 49172 RTP/AVP 99 2957 a=mid:audio 2958 a=pcfg:1 a=1 2959 a=pcfg:2 2960 m=video 560024 RTP/AVP 100 2961 a=mid:video 2962 a=pcfg:1 a=1 2963 a=pcfg:2 a=2 2965 In the example above, the potential configuration number "1" is 2966 repeated while referring to attribute capability a=rtcp-mux, since 2967 the behavior is IDENTICAL for the attribute a=rtcp-mux under 2968 multiplexing. 2970 14.3. RFC6871 Analysis 2972 [RFC6871] extends the capability negotiation framework described in 2973 [RFC5939] by defining media capabilities that can be used to indicate 2974 and negotiate media types and their associated format parameters. It 2975 also allows indication of latent configurations and session 2976 capabilities. 2978 14.3.1. Recommendation: Dealing with Payload Type Numbers 2980 [RFC6871] defines a new payload type ("pt") parameter to be used with 2981 the potential, actual, and latent configuration parameters. The 2982 parameter associates RTP payload type numbers with the referenced 2983 RTP-based media format capabilities ("a=rmcap") defined in [RFC6871] 2984 and is appropriate only when the transport protocol uses RTP. This 2985 means that the same payload type number can be assigned as part of 2986 potential or actual configurations in different media descriptions in 2987 a bundle. There are rules for the usage of identical Payload Type 2988 values across multiplexed "m=" lines as described in 2989 [I-D.ietf-mmusic-sdp-bundle-negotiation], which must be followed here 2990 as well. As described in Section 14.2.1, the use of identical 2991 configuration numbers for compatible configurations in different 2992 media descriptions that are part of the bundle provides a way to 2993 ensure that the answerer can easily pick compatible configurations 2994 here as well. 2996 14.3.1.1. Example: Attribute Capability Under Shared Payload Type 2998 The attributes (a=rmcap, a=mfcap) follow the above recommendations 2999 under multiplexing. 3001 v=0 3002 o=- 25678 753849 IN IP4 192.0.2.1 3003 s= 3004 c=IN IP4 192.0.2.1 3005 t=0 0 3006 a=creq:med-v0 3007 m=audio 54322 RTP/AVP 96 3008 a=rtpmap:96 AMR-WB/16000/1 3009 a=fmtp:96 mode-change-capability=1; max-red=220; 3010 mode-set=0,2,4,7 3011 a=rmcap:1,3 audio AMR-WB/16000/1 3012 a=rmcap:2 audio AMR/8000/1 3013 a=mfcap:1,2 mode-change-capability=1 3014 a=mfcap:3 mode-change-capability=2 3015 a=pcfg:1 m=1 pt=1:96 3016 a=pcfg:2 m=2 pt=2:97 3017 a=pcfg:3 m=3 pt=3:98 3018 m=audio 54322 RTP/AVP 96 3019 a=rtpmap:96 AMR-WB/16000/1 3020 a=fmtp:96 mode-change-capability=1; max-red=220; 3021 mode-set=0,2,4,7 3022 a=rmcap:4 audio AMR/8000/1 3023 a=rmcap:5 audio OPUS/48000/2 3024 a=mfcap:5 minptime=40 3025 a=mfcap:4 mode-change-capability=1 3026 a=pcfg:1 m=4 pt=4:97 3027 a=pcfg:4 m=5 pt=5:101 3029 In the example above, the potential configuration number "1" is 3030 repeated when referring to media and media format capability used for 3031 the Payload Type 96. This implies that both the media capability 2 3032 and 4 along with their media format capabilities MUST refer to the 3033 same codec configuration, as per the definition of IDENTICAL-PER-PT. 3035 14.3.2. Recommendation: Dealing with Latent Configurations 3037 [RFC6871] adds the notion of a latent configurations, which provides 3038 configuration information that may be used to guide a subsequent 3039 offer/exchange, e.g. by adding another media stream or use 3040 alternative codec combinations not currently offered. Latent 3041 configurations have configuration numbers which cannot overlap with 3042 the potential configuration numbers [RFC6871]. Supported 3043 combinations of potential and latent configurations are indicated by 3044 use of the "a=sescap" attribute, however use of this attribute is not 3045 recommended with multiplexed media, since it requires the use of 3046 unique configuration numbers across the SDP. Taken together, this 3047 means there is no well-defined way to indicate supported combinations 3048 of latent configurations, or combinations of latent and potential 3049 configurations with multiplexed media. It is still allowed to use 3050 the latent configuration attribute, however the limitations above 3051 will apply. To determine valid combinations, actual negotiation will 3052 have to be attempted subsequently instead. 3054 15. IANA Considerations 3056 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 3057 document.] 3059 Section 15.1 defines a new subregistry to be added by the IANA for 3060 identifying the initial registrations for various multiplexing 3061 categories applicable, as proposed in this document. 3063 IANA is also requested to add a new column named "Mux Category" to 3064 several of the subregistries in the "Session Description Protocol 3065 (SDP) Parameters" registry. The tables in Section 15.2 identify name 3066 of an entry in the existing subregistry and specify the value to be 3067 put in the new "Mux Category" column of the associated IANA registry. 3069 15.1. New 'Multiplexing Categories' subregistry 3071 A new sub-registry needs to be defined called the "Multiplexing 3072 Categories", with the following registrations created initially: 3073 "NORMAL", "CAUTION", "IDENTICAL", "TRANSPORT", "SUM", "INHERIT", 3074 "IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this document. 3076 Initial value registration for "Multiplexing Categories". 3078 +-------------------------+-----------+ 3079 | Multiplexing Categories | Reference | 3080 +-------------------------+-----------+ 3081 | NORMAL | RFCXXXX | 3082 | CAUTION | RFCXXXX | 3083 | IDENTICAL | RFCXXXX | 3084 | TRANSPORT | RFCXXXX | 3085 | SUM | RFCXXXX | 3086 | INHERIT | RFCXXXX | 3087 | IDENTICAL-PER-PT | RFCXXXX | 3088 | SPECIAL | RFCXXXX | 3089 | TBD | RFCXXXX | 3090 +-------------------------+-----------+ 3092 Further entries can be registered using Standard Actions policies 3093 outlined in [RFC5226], which requires IESG review and approval and 3094 standards-track IETF RFC publication. 3096 Each registration needs to indicate the multiplexing category value 3097 to be added to the "Multiplexing Categories" subregistry as defined 3098 in this section. 3100 Such a registration MUST also indicate the applicability of the newly 3101 defined multiplexing category value to various subregistries defined 3102 at the "Session Description Protocol (SDP) Parameters" registry. 3104 15.2. 'Mux Category' column for subregistries 3106 Each sub-section identifies a subregistry in the "Session Description 3107 Protocol (SDP) Parameters" registry. The tables list the column that 3108 identifies the SDP attribute name/Token/Value from the corresponding 3109 subregistries and the values to be used for the new "Mux Category" 3110 column to be added. 3112 For the entries in the existing subregistries, under the "Session 3113 Description Protocol (SDP) Parameters" registry, that lack a value 3114 for the "Mux Category" in this specification will get a value of 3115 "TBD". 3117 The registration policy for updates to the 'Mux Category' column 3118 values for existing parameters, or when registering new parameters, 3119 are beyond the scope of this document. The registration policy for 3120 the affected table is defined in [I-D.ietf-mmusic-rfc4566bis]. 3122 15.2.1. Table: SDP bwtype 3124 The following values are to be added to the 'SDP bwtype' subregistry 3125 in the "Session Description Protocol (SDP) Parameters" registry. The 3126 references should be updated to point at this RFC as well as the 3127 previous references. 3129 +----------+--------------+ 3130 | SDP Name | Mux Category | 3131 +----------+--------------+ 3132 | CT | NORMAL | 3133 | AS | SUM | 3134 | RS | SUM | 3135 | RR | SUM | 3136 | TIAS | SPECIAL | 3137 +----------+--------------+ 3139 15.2.2. Table: att-field (session level) 3141 The following values are to be added to the "att-field (session 3142 level)" subregistry in the "Session Description Protocol (SDP) 3143 Parameters" registry. The references should be updated to point at 3144 this RFC as well as the previous references. 3146 +---------------------+--------------+ 3147 | SDP Name | Mux Category | 3148 +---------------------+--------------+ 3149 | cat | NORMAL | 3150 | keywds | NORMAL | 3151 | type | NORMAL | 3152 | type:broadcast | NORMAL | 3153 | type:H332 | NORMAL | 3154 | type:meeting | NORMAL | 3155 | type:moderated | NORMAL | 3156 | type:test | NORMAL | 3157 | charset | NORMAL | 3158 | charset:iso8895-1 | NORMAL | 3159 | tool | NORMAL | 3160 | ipbcp | SPECIAL | 3161 | group | NORMAL | 3162 | ice-lite | NORMAL | 3163 | ice-options | NORMAL | 3164 | bcastversion | NORMAL | 3165 | 3GPP-Integrity-Key | CAUTION | 3166 | 3GPP-SDP-Auth | CAUTION | 3167 | alt-group | CAUTION | 3168 | PSCid | NORMAL | 3169 | bc_service | NORMAL | 3170 | bc_program | NORMAL | 3171 | bc_service_package | NORMAL | 3172 | sescap | CAUTION | 3173 | rtsp-ice-d-m | TBD | 3174 +---------------------+--------------+ 3176 15.2.3. Table: att-field (both session and media level) 3178 The following values are to be added to the "att-field (both session 3179 and media level)" subregistry in the "Session Description Protocol 3180 (SDP) Parameters" registry. The references should be updated to 3181 point at this RFC as well as the previous references. 3183 NOTE: The attributes from draft-ietf-rmt-flute-sdp ('flute-tsi', 3184 'flute-ch', 'FEC-declaration', 'FEC-OTI-extension', 'content-desc') 3185 were not analyzed for their multiplexing behavior due to the expired 3186 status of the draft. For purposes of this specification, the 3187 multiplexing category of 'TBD' is assigned. 3189 +-------------------------+-------------------+ 3190 | SDP Name | Mux Category | 3191 +-------------------------+-------------------+ 3192 | recvonly | NORMAL | 3193 | sendrecv | NORMAL | 3194 | sendonly | NORMAL | 3195 | sdplang | NORMAL | 3196 | lang | NORMAL | 3197 | h248item | SPECIAL | 3198 | sqn | NORMAL | 3199 | cdsc | NORMAL | 3200 | cpar | INHERIT | 3201 | cparmin | SPECIAL | 3202 | cparmax | SPECIAL | 3203 | rtcp-xr | NORMAL | 3204 | maxprate | SPECIAL | 3205 | setup | TRANSPORT | 3206 | connection | TRANSPORT | 3207 | key-mgmt | IDENTICAL | 3208 | source-filter | IDENTICAL | 3209 | inactive | NORMAL | 3210 | fingerprint | TRANSPORT | 3211 | flute-tsi | TBD | 3212 | flute-ch | TBD | 3213 | FEC-declaration | TBD | 3214 | FEC-OTI-extension | TBD | 3215 | content-desc | TBD | 3216 | ice-pwd | TRANSPORT | 3217 | ice-ufrag | TRANSPORT | 3218 | stkmstream | NORMAL | 3219 | extmap | SPECIAL | 3220 | qos-mech-send | TRANSPORT | 3221 | qos-mech-recv | TRANSPORT | 3222 | csup | NORMAL | 3223 | creq | NORMAL | 3224 | acap | INHERIT | 3225 | tcap | INHERIT | 3226 | 3GPP-QoE-Metrics | CAUTION | 3227 | 3GPP-Asset-Information | CAUTION | 3228 | mbms-mode | CAUTION | 3229 | mbms-repair | CAUTION | 3230 | ike-setup | IDENTICAL | 3231 | psk-fingerprint | IDENTICAL | 3232 | multicast-rtcp | IDENTICAL | 3233 | rmcap | IDENTICAL-PER-PT | 3234 | omcap | NORMAL | 3235 | mfcap | IDENTICAL-PER-PT | 3236 | mscap | INHERIT | 3237 | 3gpp.iut.replication | TBD | 3238 | bcap | INHERIT | 3239 | ccap | IDENTICAL | 3240 | icap | NORMAL | 3241 | 3gpp_sync_info | NORMAL | 3242 | 3gpp_MaxRecvSDUSize | NORMAL | 3243 | etag | CAUTION | 3244 | duplication-delay | NORMAL | 3245 | range | CAUTION | 3246 | control | CAUTION | 3247 | mtag | CAUTION | 3248 | ts-refclk | NORMAL | 3249 | mediaclk | NORMAL | 3250 | calgextmap | NORMAL | 3251 +-------------------------+-------------------+ 3253 15.2.4. Table: att-field (media level only) 3255 The following values are to be added to the "att-field (media level 3256 only)" registry in the "Session Description Protocol (SDP) 3257 Parameters" registry. The references should be updated to point at 3258 this RFC as well as the previous references. 3260 +---------------------------+-------------------+ 3261 | SDP Name | Mux Category | 3262 +---------------------------+-------------------+ 3263 | ptime | IDENTICAL-PER-PT | 3264 | orient | NORMAL | 3265 | orient:portrait | NORMAL | 3266 | orient:landscape | NORMAL | 3267 | orient:seascape | NORMAL | 3268 | framerate | IDENTICAL-PER-PT | 3269 | quality | NORMAL | 3270 | rtpmap | IDENTICAL-PER-PT | 3271 | fmtp | IDENTICAL-PER-PT | 3272 | rtpred1 | CAUTION | 3273 | rtpred2 | CAUTION | 3274 | T38FaxVersion | TBD | 3275 | T38MaxBitRate | TBD | 3276 | T38FaxFillBitRemoval | TBD | 3277 | T38FaxTranscodingMMR | TBD | 3278 | T38FaxTranscodingJBIG | TBD | 3279 | T38FaxRateManagement | TBD | 3280 | T38FaxMaxBuffer | TBD | 3281 | T38FaxMaxDatagram | TBD | 3282 | T38FaxUdpEC | TBD | 3283 | maxptime | IDENTICAL-PER-PT | 3284 | des | CAUTION | 3285 | curr | CAUTION | 3286 | conf | CAUTION | 3287 | mid | NORMAL | 3288 | rtcp | TRANSPORT | 3289 | rtcp-fb | IDENTICAL-PER-PT | 3290 | label | NORMAL | 3291 | T38VendorInfo | TBD | 3292 | crypto | TRANSPORT | 3293 | eecid | CAUTION | 3294 | aalType | CAUTION | 3295 | capability | CAUTION | 3296 | qosClass | CAUTION | 3297 | bcob | CAUTION | 3298 | stc | CAUTION | 3299 | upcc | CAUTION | 3300 | atmQOSparms | CAUTION | 3301 | atmTrfcDesc | CAUTION | 3302 | abrParms | CAUTION | 3303 | abrSetup | CAUTION | 3304 | bearerType | CAUTION | 3305 | lij | CAUTION | 3306 | anycast | CAUTION | 3307 | cache | CAUTION | 3308 | bearerSigIE | CAUTION | 3309 | aalApp | CAUTION | 3310 | cbrRate | CAUTION | 3311 | sbc | CAUTION | 3312 | clkrec | CAUTION | 3313 | fec | CAUTION | 3314 | prtfl | CAUTION | 3315 | structure | CAUTION | 3316 | cpsSDUsize | CAUTION | 3317 | all2CPS | CAUTION | 3318 | all2CPSSDUrate | CAUTION | 3319 | aal2sscs3661unassured | CAUTION | 3320 | aal2sscs3661assured | CAUTION | 3321 | aal2sscs3662 | CAUTION | 3322 | aal5sscop | CAUTION | 3323 | atmmap | CAUTION | 3324 | silenceSupp | CAUTION | 3325 | ecan | CAUTION | 3326 | gc | CAUTION | 3327 | profileDesc | CAUTION | 3328 | vsel | CAUTION | 3329 | dsel | CAUTION | 3330 | fsel | CAUTION | 3331 | onewaySel | CAUTION | 3332 | codecconfig | CAUTION | 3333 | isup_usi | CAUTION | 3334 | uiLayer1_Prot | CAUTION | 3335 | chain | CAUTION | 3336 | floorctrl | TBD | 3337 | confid | NORMAL | 3338 | userid | NORMAL | 3339 | floorid | NORMAL | 3340 | FEC | NORMAL | 3341 | accept-types | TBD | 3342 | accept-wrapped-types | TBD | 3343 | max-size | TBD | 3344 | path | TBD | 3345 | dccp-service-code | CAUTION | 3346 | rtcp-mux | IDENTICAL | 3347 | candidate | TRANSPORT | 3348 | ice-mismatch | NORMAL | 3349 | remote-candidates | TRANSPORT | 3350 | SRTPAuthentication | TBD | 3351 | SRTPROCTxRate | TBD | 3352 | rtcp-rsize | IDENTICAL | 3353 | file-selector | TBD | 3354 | file-transfer-id | TBD | 3355 | file-disposition | TBD | 3356 | file-date | TBD | 3357 | file-icon | TBD | 3358 | file-range | TBD | 3359 | depend | IDENTICAL-PER-PT | 3360 | ssrc | NORMAL | 3361 | ssrc-group | NORMAL | 3362 | rtcp-unicast | IDENTICAL | 3363 | pcfg | SPECIAL | 3364 | acfg | SPECIAL | 3365 | zrtp-hash | TRANSPORT | 3366 | X-predecbufsize | CAUTION | 3367 | X-initpredecbufperiod | CAUTION | 3368 | X-initpostdecbufperiod | CAUTION | 3369 | X-decbyterate | CAUTION | 3370 | 3gpp-videopostdecbufsize | CAUTION | 3371 | framesize | CAUTION | 3372 | 3GPP-SRTP-Config | CAUTION | 3373 | alt | CAUTION | 3374 | alt-default-id | CAUTION | 3375 | 3GPP-Adaption-Support | CAUTION | 3376 | mbms-flowid | CAUTION | 3377 | fec-source-flow | SPECIAL | 3378 | fec-repair-flow | SPECIAL | 3379 | repair-window | SPECIAL | 3380 | rams-updates | CAUTION | 3381 | imageattr | IDENTICAL-PER-PT | 3382 | cfw-id | NORMAL | 3383 | portmapping-req | CAUTION | 3384 | g.3gpp.cat | NORMAL | 3385 | g.3gpp.crs | NORMAL | 3386 | ecn-capable-rtp | IDENTICAL | 3387 | visited-realm | TRANSPORT | 3388 | secondary-realm | TRANSPORT | 3389 | omr-s-cksum | NORMAL | 3390 | omr-m-cksum | NORMAL | 3391 | omr-codecs | NORMAL | 3392 | omr-m-att | NORMAL | 3393 | omr-s-att | NORMAL | 3394 | omr-m-bw | NORMAL | 3395 | omr-s-bw | NORMAL | 3396 | msrp-cema | TBD | 3397 | dccp-port | CAUTION | 3398 | resource | NORMAL | 3399 | channel | NORMAL | 3400 | cmid | NORMAL | 3401 | content | NORMAL | 3402 | lcfg | SPECIAL | 3403 | loopback | NORMAL | 3404 | loopback-source | NORMAL | 3405 | loopback-mirror | NORMAL | 3406 | chatroom | TBD | 3407 | altc | TRANSPORT | 3408 | T38FaxMaxIFP | TBD | 3409 | T38FaxUdpECDepth | TBD | 3410 | T38FaxUdpFECMaxSpan | TBD | 3411 | T38ModemType | TBD | 3412 | cs-correlation | TBD | 3413 | rtcp-idms | NORMAL | 3414 +---------------------------+-------------------+ 3416 15.2.5. Table: att-field (source level) 3418 The following values are to be added to the "att-field (source 3419 level)" registry in the "Session Description Protocol (SDP) 3420 Parameters" registry. The references should be updated to point at 3421 this RFC as well as the previous references. 3423 +----------------+-------------------+ 3424 | SDP Name | Mux Category | 3425 +----------------+-------------------+ 3426 | cname | NORMAL | 3427 | previous-ssrc | NORMAL | 3428 | fmtp | IDENTICAL-PER-PT | 3429 | ts-refclk | NORMAL | 3430 | mediaclk | NORMAL | 3431 +----------------+-------------------+ 3433 15.2.6. Table: content SDP Parameters 3435 The following values are to be added to the "content SDP Parameters" 3436 subregistry in the "Session Description Protocol (SDP) Parameters" 3437 registry. The references should be updated to point at this RFC as 3438 well as the previous references. 3440 +----------+--------------+ 3441 | SDP Name | Mux Category | 3442 +----------+--------------+ 3443 | slides | NORMAL | 3444 | speaker | NORMAL | 3445 | sl | NORMAL | 3446 | main | NORMAL | 3447 | alt | NORMAL | 3448 +----------+--------------+ 3450 15.2.7. Table: Semantics for the 'group' SDP Attribute 3452 The following values are to be added to the "Semantics for the 3453 "group" SDP Attribute" subregistry in the "Session Description 3454 Protocol (SDP) Parameters" registry. The references should be 3455 updated to point at this RFC as well as the previous references. 3457 +---------+--------------+ 3458 | Token | Mux Category | 3459 +---------+--------------+ 3460 | LS | NORMAL | 3461 | FID | NORMAL | 3462 | SRF | NORMAL | 3463 | ANAT | CAUTION | 3464 | FEC | NORMAL | 3465 | FEC-FR | NORMAL | 3466 | CS | NORMAL | 3467 | DDP | NORMAL | 3468 | DUP | NORMAL | 3469 +---------+--------------+ 3471 15.2.8. Table: 'rtcp-fb' Attribute Values 3473 The following values are to be added to the " 'rtcp-fb' Attribute 3474 Values" subregistry in the "Session Description Protocol (SDP) 3475 Parameters" registry. The references should be updated to point at 3476 this RFC as well as the previous references. 3478 +------------+-------------------+ 3479 | Value Name | Mux Category | 3480 +------------+-------------------+ 3481 | ack | IDENTICAL-PER-PT | 3482 | app | SPECIAL | 3483 | ccm | IDENTICAL-PER-PT | 3484 | nack | IDENTICAL-PER-PT | 3485 | trr-int | IDENTICAL-PER-PT | 3486 +------------+-------------------+ 3488 15.2.9. Table: 'ack' and 'nack' Attribute Values 3490 The following values are to be added to the " 'ack' and 'nack' 3491 Attribute Values" subregistry in the "Session Description Protocol 3492 (SDP) Parameters" registry. The references should be updated to 3493 point at this RFC as well as the previous references. 3495 +------------+-------------------+ 3496 | Value Name | Mux Category | 3497 +------------+-------------------+ 3498 | sli | IDENTICAL-PER-PT | 3499 | pli | IDENTICAL-PER-PT | 3500 | rpsi | IDENTICAL-PER-PT | 3501 | app | SPECIAL | 3502 | rai | IDENTICAL-PER-PT | 3503 | tllei | IDENTICAL-PER-PT | 3504 | pslei | IDENTICAL-PER-PT | 3505 | ecn | IDENTICAL | 3506 +------------+-------------------+ 3508 15.2.10. Table: 'depend' SDP Attribute Values 3510 The following values are to be added to the " 'depend' SDP Attribute 3511 Values" subregistry in the "Session Description Protocol (SDP) 3512 Parameters" registry. The references should be updated to point at 3513 this RFC as well as the previous references. 3515 +-------+-------------------+ 3516 | Token | Mux Category | 3517 +-------+-------------------+ 3518 | lay | IDENTICAL-PER-PT | 3519 | mdc | IDENTICAL-PER-PT | 3520 +-------+-------------------+ 3522 15.2.11. Table: 'cs-correlation' Attribute Values 3524 The following values are to be added to the " "cs-correlation" 3525 Attribute Values" subregistry in the "Session Description Protocol 3526 (SDP) Parameters" registry. The references should be updated to 3527 point at this RFC as well as the previous references. 3529 +-----------+--------------+ 3530 | Value | Mux Category | 3531 +-----------+--------------+ 3532 | callerid | TBD | 3533 | uuie | TBD | 3534 | dtmf | TBD | 3535 | external | TBD | 3536 +-----------+--------------+ 3538 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 3540 The following values are to be added to the Semantics for the 3541 "Semantics for the "ssrc-group" SDP Attribute" subregistry in the 3542 "Session Description Protocol (SDP) Parameters" registry. The 3543 references should be updated to point at this RFC as well as the 3544 previous references. 3546 +---------+--------------+ 3547 | Token | Mux Category | 3548 +---------+--------------+ 3549 | FID | NORMAL | 3550 | FEC | NORMAL | 3551 | FEC-FR | NORMAL | 3552 | DUP | NORMAL | 3553 +---------+--------------+ 3555 15.2.13. Table: SDP/RTSP key management protocol identifiers 3557 The following values are to be added to the "SDP/RTSP key management 3558 protocol identifiers" subregistry in the "Session Description 3559 Protocol (SDP) Parameters" registry. The references should be 3560 updated to point at this RFC as well as the previous references. 3562 +------------+--------------+ 3563 | Value Name | Mux Category | 3564 +------------+--------------+ 3565 | mikey | IDENTICAL | 3566 +------------+--------------+ 3568 15.2.14. Table: Codec Control Messages 3570 The following values are to be added to the "Codec Control Messages" 3571 subregistry in the "Session Description Protocol (SDP) Parameters" 3572 registry. The references should be updated to point at this RFC as 3573 well as the previous references. 3575 +------------+-------------------+ 3576 | Value Name | Mux Category | 3577 +------------+-------------------+ 3578 | fir | IDENTICAL-PER-PT | 3579 | tmmbr | IDENTICAL-PER-PT | 3580 | tstr | IDENTICAL-PER-PT | 3581 | vbcm | IDENTICAL-PER-PT | 3582 +------------+-------------------+ 3584 15.2.15. Table: QoS Mechanism Tokens 3586 The following values are to be added to the "QoS Mechanism Tokens" 3587 subregistry in the "Session Description Protocol (SDP) Parameters" 3588 registry. The references should be updated to point at this RFC as 3589 well as the previous references. 3591 +---------------+--------------+ 3592 | QoS Mechanism | Mux Category | 3593 +---------------+--------------+ 3594 | rsvp | TRANSPORT | 3595 | nsis | TRANSPORT | 3596 +---------------+--------------+ 3598 15.2.16. Table: SDP Capability Negotiation Option Tags 3600 The following values are to be added to the "SDP Capability 3601 Negotiation Option Tags" subregistry in the "Session Description 3602 Protocol (SDP) Parameters" registry. The references should be 3603 updated to point at this RFC as well as the previous references. 3605 +------------+--------------+ 3606 | Option Tag | Mux Category | 3607 +------------+--------------+ 3608 | cap-v0 | NORMAL | 3609 | med-v0 | NORMAL | 3610 | bcap-v0 | NORMAL | 3611 | ccap-v0 | NORMAL | 3612 | icap-v0 | NORMAL | 3613 +------------+--------------+ 3615 15.2.17. Table: Timestamp Reference Clock Source Parameters 3617 The following values are to be added to the "Timestamp Reference 3618 Clock Source Parameters" subregistry in the "Session Description 3619 Protocol (SDP) Parameters" registry. The references should be 3620 updated to point at this RFC as well as the previous references. 3622 +----------+--------------+ 3623 | Name | Mux Category | 3624 +----------+--------------+ 3625 | ntp | NORMAL | 3626 | ptp | NORMAL | 3627 | gps | NORMAL | 3628 | gal | NORMAL | 3629 | glonass | NORMAL | 3630 | local | NORMAL | 3631 | private | NORMAL | 3632 +----------+--------------+ 3634 15.2.18. Table: Media Clock Source Parameters 3636 The following values are to be added to the "Media Clock Source 3637 Parameters" subegistry in the "Session Description Protocol (SDP) 3638 Parameters" registry. The references should be updated to point at 3639 this RFC as well as the previous references. 3641 +-----------+--------------+ 3642 | Name | Mux Category | 3643 +-----------+--------------+ 3644 | sender | NORMAL | 3645 | direct | NORMAL | 3646 | IEEE1722 | NORMAL | 3647 +-----------+--------------+ 3649 16. Security Considerations 3651 The primary security for RTP including the way it is used here is 3652 described in [RFC3550] and [RFC3711]. 3654 When multiplexing SDP attributes with the category "CAUTION", the 3655 implementations should be aware of possible issues as described in 3656 this specification. 3658 17. Acknowledgments 3660 I would like to thank Cullen Jennings, Flemming Andreasen for 3661 suggesting the categories, contributing text and reviewing the draft. 3662 I would also link to thank Magnus Westerlund, Christer Holmberg, 3663 Jonathan Lennox, Bo Burman, Ari Keranen, and Dan Wing on suggesting 3664 structural changes helping improve the document readability. 3666 I would like also to thank following experts on their inputs and 3667 reviews as listed - Flemming Andreasen(5.24,5.32,5.33,14), Rohan 3668 Mahy(5.57), Eric Burger(5.26),Christian Huitema(5.14), Christer 3669 Holmberg(5.21,5.26,5.51,5.52), Richard Ejzak (5.44,5.53,5.54), Colin 3670 Perkins(5.7,5.8,5.9,5.58), Magnus 3671 Westerlund(5.2,5.3,5.9,5.27,5.47,6.1,6.2,6.3,8.3,7), Roni 3672 Evens(5.12,5.27,8.4), Subha Dhesikan(5.6,10), Dan 3673 Wing(5.7,5.12,5.35,5.39,5.45), Cullen Jennings (5.40), Ali C 3674 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 3675 (7.2,7.6), Charles Eckel(5.15,5.27,5.28,9.1,8.5), Paul Kyzivat(5.24), 3676 Ian Johansson(5.15), Saravanan Shanmugham(5.11), Paul E Jones(5.30), 3677 Rajesh Kumar(5.48), Jonathan Lennox(5.36,5,15,9.1,11.1), Mo 3678 Zanaty(5.4,5.5,5.23,8.1,8.3,8.5,12.1), Christian Huitema (5.14), Qin 3679 Wu (5.47 PM-Dir review), Hans Stokking(5.43,5.16), Christian Groves 3680 (5.48,5.55), Thomas Stach. 3682 I would like to thank Chris Lonvick for the SECDIR review, Dan 3683 Romascanu for th Gen-ART review and Sabrina Tanamal for the IANA 3684 review. 3686 Thanks to Ben Campbell for AD review suggestions. Thanks to Spencer 3687 Dawkins, Stephen Farrel, Alissa Cooper, Mirja Kuehlewind and the 3688 entire IESG experts for their reviews. 3690 18. Change Log 3692 [RFC EDITOR NOTE: Please remove this section when publishing] 3694 Changes draft-ietf-mmusic-sdp-mux-attributes-15 3696 o Updated Mux category for floorctrl to TBD 3697 Changes draft-ietf-mmusic-sdp-mux-attributes-14 3699 o Incorporated Comments from IESG review : 3701 * Updated security considerations section to fix the 3702 incositencies (Spencer's review) 3704 * Updated section 5.36 to align the text with 5.39 (Stephen's 3705 review) 3707 * Updated IANA registration section to make RFC4566bis a 3708 informative dependency (IETF 98 followup) 3710 * Updated Section 5 to expand 'B' level SDP attributes (Dan's 3711 review) 3713 Changes from draft-ietf-mmusic-sdp-mux-attributes-10 - draft-ietf- 3714 mmusic-sdp-mux-attributes-13 3716 o Incorporated Comments from WGLC review and AD Evaluation 3718 Changes from draft-ietf-mmusic-sdp-mux-attributes-10 3720 o Incorporated Comments from Bo Burman for publication request 3722 Changes from draft-ietf-mmusic-sdp-mux-attributes-08 to draft-ietf- 3723 mmusic-sdp-mux-attributes-10 3725 o Minor nits and version update to advert expiration 3727 Changes from draft-ietf-mmusic-sdp-mux-attributes-06 to draft-ietf- 3728 mmusic-sdp-mux-attributes-08 3730 o Assigned TBD category to all the attributes for whom there exists 3731 no specification on multiplexing behavior over the underlying 3732 transport protocol today. 3734 o Incorporated comments from Flemming and Ari (post last call) 3736 Changes from draft-ietf-mmusic-sdp-mux-attributes-06 3738 o Incorporated last call review comments from Thomas Stach and Ari 3739 Keranen. 3741 o Fixed more nits to prep for the LastCall. 3743 Changes from draft-ietf-mmusic-sdp-mux-attributes-05 3744 o Incorporated review comments from Christian Grooves and Ari 3745 Keranen. 3747 o Fixed more nits to prep for the LastCall. 3749 Changes from draft-ietf-mmusic-sdp-mux-attributes-04 3751 o Fixed minor nits overall. 3753 o Updated Acknowledgement Sections 3755 o Last Call Version. 3757 Changes from draft-ietf-mmusic-sdp-mux-attributes-03 3759 o More re-work on the IANA section. 3761 o Clean ups preparing for the last call. 3763 Changes from draft-ietf-mmusic-sdp-mux-attributes-02 3765 o Incorporated suggestions from Flemming on Capability Negotiation. 3767 o Closed open issues from IETF90 3769 o Added IANA section to list the categories for all the SDP 3770 attributes anlayzed 3772 o Lots of cleanup 3774 o Reformatted Refernces section to use short-form notation 3776 Changes from draft-ietf-mmusic-sdp-mux-attributes-01 3778 o Updated section 15 to provide detailed recommendation on dealing 3779 with encapsulating attributes. Also updated sections 5.20, 5.28, 3780 5.29 to refer to Section 15. 3782 o Added new categories IDENTICAL-PER-PT and INHERIT 3784 o Updated Sections 16 to add the new categories. 3786 o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the 3787 category IDENTICAL-PER-PT. 3789 o Reformatted section 4 to add individual categories to their own 3790 sections. 3792 Changes from draft-ietf-mmusic-sdp-mux-attributes-00 3794 o Added Section 15 to provide recommendations on multiplexing SDP 3795 encapsulating attributes. Also updated sections 5.20, 5.28, 5.29 3796 to refer to Section 15. 3798 o Updated Section 5.38 to incorporate PM-dir review inputs from Qin 3799 Wu 3801 o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more 3802 clarity. 3804 o Fixed few nits regarding sentence clarity and fill-in the NOTES 3805 section where information was lacking. 3807 Changes from draft-nandakumar-mmusic-mux-attributes-05 3809 o Renamed the document to be a WG document. 3811 o Added Section 14. 3813 o Updated Open Issues based on IETF88 discussions. 3815 Changes from draft-nandakumar-mmusic-mux-attributes-04 3817 o Added few OPEN ISSUES that needs to be discussed. 3819 o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4, 3820 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1 3822 o Updated Table Column name Current to Level and improved TRANSPORT 3823 category explanation on suggestions form Dan Wing. 3825 o Grouped all the rtcp-fb attribute analysis under a single section 3826 as suggested by Magnus/ 3828 Changes from draft-nandakumar-mmusic-mux-attributes-03 3830 o Maintenance change to clean up grammatical nits and wordings. 3832 Changes from draft-nandakumar-mmusic-mux-attributes-02 3834 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34, 3835 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 3836 the inputs from the respective RFC Authors. 3838 Changes from draft-nandakumar-mmusic-mux-attributes-01 3839 o Replaced Category BAD with NOT-RECOMMENDED. 3841 o Added Category TBD. 3843 o Updated IANA Consideration Section. 3845 Changes from draft-nandakumar-mmusic-mux-attributes-00 3847 o Added new section for dealing with FEC payload types. 3849 19. References 3851 19.1. Normative References 3853 [I-D.ietf-mmusic-sdp-bundle-negotiation] 3854 Holmberg, C., Alvestrand, H., and C. Jennings, 3855 "Negotiating Media Multiplexing Using the Session 3856 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- 3857 negotiation-24 (work in progress), January 2016. 3859 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3860 Requirement Levels", BCP 14, RFC 2119, March 1997. 3862 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 3863 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 3864 July 2006, . 3866 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3867 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 3868 DOI 10.17487/RFC5226, May 2008, 3869 . 3871 19.2. Informative References 3873 [H.248.15] 3874 "Gateway control protocol: SDP H.248 package attribute", 3875 . 3877 [I-D.ietf-mmusic-rfc4566bis] 3878 Handley, M., Jacobson, V., Perkins, C., and A. Begen, 3879 "SDP: Session Description Protocol", draft-ietf-mmusic- 3880 rfc4566bis-17 (work in progress), June 2016. 3882 [IANA] "Session Description Protocol (SDP) Parameters", 3883 . 3886 [Q.1970] "Q.1970 : BICC IP bearer control protocol", 3887 . 3889 [R3GPPTS183.063] 3890 "TISPAN - IMS based ITPV Stage 3 specification.", 3891 . 3895 [R3GPPTS24.182] 3896 "IP Multimedia Subsystem (IMS) Customized Alerting Tones 3897 (CAT); Protocol specification", 3898 . 3900 [R3GPPTS24.183] 3901 "IP Multimedia Subsystem (IMS) Customized Ringing Signal 3902 (CRS); Protocol specification", 3903 . 3905 [R3GPPTS24.229] 3906 "IP multimedia call control protocol based on Session 3907 Initiation Protocol (SIP) and Session Description Protocol 3908 (SDP);", 3909 . 3911 [R3GPPTS26.114] 3912 "IP multimedia Subsystem : Media Handling and 3913 interaction", . 3915 [RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time 3916 Streaming Protocol (RTSP)", RFC 2326, DOI 10.17487/ 3917 RFC2326, April 1998, 3918 . 3920 [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the 3921 Session Description Protocol (SDP) for ATM Bearer 3922 Connections", RFC 3108, DOI 10.17487/RFC3108, May 2001, 3923 . 3925 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 3926 with Session Description Protocol (SDP)", RFC 3264, DOI 3927 10.17487/RFC3264, June 2002, 3928 . 3930 [RFC3312] Camarillo, G., Ed., Marshall, W., Ed., and J. Rosenberg, 3931 "Integration of Resource Management and Session Initiation 3932 Protocol (SIP)", RFC 3312, DOI 10.17487/RFC3312, October 3933 2002, . 3935 [RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple 3936 Capability Declaration", RFC 3407, DOI 10.17487/RFC3407, 3937 October 2002, . 3939 [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to 3940 Resource Reservation Flows", RFC 3524, DOI 10.17487/ 3941 RFC3524, April 2003, 3942 . 3944 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 3945 Jacobson, "RTP: A Transport Protocol for Real-Time 3946 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 3947 July 2003, . 3949 [RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth 3950 Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC 3951 3556, DOI 10.17487/RFC3556, July 2003, 3952 . 3954 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute 3955 in Session Description Protocol (SDP)", RFC 3605, DOI 3956 10.17487/RFC3605, October 2003, 3957 . 3959 [RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., 3960 "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3961 3611, DOI 10.17487/RFC3611, November 2003, 3962 . 3964 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 3965 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 3966 RFC 3711, DOI 10.17487/RFC3711, March 2004, 3967 . 3969 [RFC3890] Westerlund, M., "A Transport Independent Bandwidth 3970 Modifier for the Session Description Protocol (SDP)", RFC 3971 3890, DOI 10.17487/RFC3890, September 2004, 3972 . 3974 [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network 3975 Address Types (ANAT) Semantics for the Session Description 3976 Protocol (SDP) Grouping Framework", RFC 4091, DOI 3977 10.17487/RFC4091, June 2005, 3978 . 3980 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 3981 the Session Description Protocol (SDP)", RFC 4145, DOI 3982 10.17487/RFC4145, September 2005, 3983 . 3985 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E. 3986 Carrara, "Key Management Extensions for Session 3987 Description Protocol (SDP) and Real Time Streaming 3988 Protocol (RTSP)", RFC 4567, DOI 10.17487/RFC4567, July 3989 2006, . 3991 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session 3992 Description Protocol (SDP) Security Descriptions for Media 3993 Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, 3994 . 3996 [RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol 3997 (SDP) Source Filters", RFC 4570, DOI 10.17487/RFC4570, 3998 July 2006, . 4000 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 4001 Transport Layer Security (TLS) Protocol in the Session 4002 Description Protocol (SDP)", RFC 4572, DOI 10.17487/ 4003 RFC4572, July 2006, 4004 . 4006 [RFC4574] Levin, O. and G. Camarillo, "The Session Description 4007 Protocol (SDP) Label Attribute", RFC 4574, DOI 10.17487/ 4008 RFC4574, August 2006, 4009 . 4011 [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format 4012 for Binary Floor Control Protocol (BFCP) Streams", RFC 4013 4583, DOI 10.17487/RFC4583, November 2006, 4014 . 4016 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 4017 "Extended RTP Profile for Real-time Transport Control 4018 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI 4019 10.17487/RFC4585, July 2006, 4020 . 4022 [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description 4023 Protocol (SDP) Content Attribute", RFC 4796, DOI 10.17487/ 4024 RFC4796, February 2007, 4025 . 4027 [RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed., 4028 "The Message Session Relay Protocol (MSRP)", RFC 4975, DOI 4029 10.17487/RFC4975, September 2007, 4030 . 4032 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 4033 "Codec Control Messages in the RTP Audio-Visual Profile 4034 with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104, 4035 February 2008, . 4037 [RFC5109] Li, A., Ed., "RTP Payload Format for Generic Forward Error 4038 Correction", RFC 5109, DOI 10.17487/RFC5109, December 4039 2007, . 4041 [RFC5159] Dondeti, L., Ed. and A. Jerichow, "Session Description 4042 Protocol (SDP) Attributes for Open Mobile Alliance (OMA) 4043 Broadcast (BCAST) Service and Content Protection", RFC 4044 5159, DOI 10.17487/RFC5159, March 2008, 4045 . 4047 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 4048 (ICE): A Protocol for Network Address Translator (NAT) 4049 Traversal for Offer/Answer Protocols", RFC 5245, DOI 4050 10.17487/RFC5245, April 2010, 4051 . 4053 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP 4054 Header Extensions", RFC 5285, DOI 10.17487/RFC5285, July 4055 2008, . 4057 [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of 4058 Service (QoS) Mechanism Selection in the Session 4059 Description Protocol (SDP)", RFC 5432, DOI 10.17487/ 4060 RFC5432, March 2009, 4061 . 4063 [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size 4064 Real-Time Transport Control Protocol (RTCP): Opportunities 4065 and Consequences", RFC 5506, DOI 10.17487/RFC5506, April 4066 2009, . 4068 [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S., 4069 and P. Kyzivat, "A Session Description Protocol (SDP) 4070 Offer/Answer Mechanism to Enable File Transfer", RFC 5547, 4071 DOI 10.17487/RFC5547, May 2009, 4072 . 4074 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific 4075 Media Attributes in the Session Description Protocol 4076 (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009, 4077 . 4079 [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding 4080 Dependency in the Session Description Protocol (SDP)", RFC 4081 5583, DOI 10.17487/RFC5583, July 2009, 4082 . 4084 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control 4085 Protocol (RTCP) Extensions for Single-Source Multicast 4086 Sessions with Unicast Feedback", RFC 5760, DOI 10.17487/ 4087 RFC5760, February 2010, 4088 . 4090 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and 4091 Control Packets on a Single Port", RFC 5761, DOI 10.17487/ 4092 RFC5761, April 2010, 4093 . 4095 [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control 4096 Protocol (DCCP)", RFC 5762, DOI 10.17487/RFC5762, April 4097 2010, . 4099 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework 4100 for Establishing a Secure Real-time Transport Protocol 4101 (SRTP) Security Context Using Datagram Transport Layer 4102 Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May 4103 2010, . 4105 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description 4106 Protocol (SDP) Grouping Framework", RFC 5888, DOI 4107 10.17487/RFC5888, June 2010, 4108 . 4110 [RFC5939] Andreasen, F., "Session Description Protocol (SDP) 4111 Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939, 4112 September 2010, . 4114 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in 4115 the Session Description Protocol", RFC 5956, DOI 10.17487/ 4116 RFC5956, September 2010, 4117 . 4119 [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions 4120 Defined for 3GPP Packet-Switched Streaming Service and 4121 Multimedia Broadcast/Multicast Service", RFC 6064, DOI 4122 10.17487/RFC6064, January 2011, 4123 . 4125 [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source- 4126 Specific Multicast (SSM) Sessions", RFC 6128, DOI 4127 10.17487/RFC6128, February 2011, 4128 . 4130 [RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP: 4131 Media Path Key Agreement for Unicast Secure RTP", RFC 4132 6189, DOI 10.17487/RFC6189, April 2011, 4133 . 4135 [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for 4136 the Internet Key Exchange Protocol (IKE) in the Session 4137 Description Protocol (SDP)", RFC 6193, DOI 10.17487/ 4138 RFC6193, April 2011, 4139 . 4141 [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media 4142 Control Channel Framework", RFC 6230, DOI 10.17487/ 4143 RFC6230, May 2011, 4144 . 4146 [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image 4147 Attributes in the Session Description Protocol (SDP)", RFC 4148 6236, DOI 10.17487/RFC6236, May 2011, 4149 . 4151 [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping 4152 between Unicast and Multicast RTP Sessions", RFC 6284, DOI 4153 10.17487/RFC6284, June 2011, 4154 . 4156 [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax, 4157 "Unicast-Based Rapid Acquisition of Multicast RTP 4158 Sessions", RFC 6285, DOI 10.17487/RFC6285, June 2011, 4159 . 4161 [RFC6364] Begen, A., "Session Description Protocol Elements for the 4162 Forward Error Correction (FEC) Framework", RFC 6364, DOI 4163 10.17487/RFC6364, October 2011, 4164 . 4166 [RFC6642] Wu, Q., Ed., Xia, F., and R. Even, "RTP Control Protocol 4167 (RTCP) Extension for a Third-Party Loss Report", RFC 6642, 4168 DOI 10.17487/RFC6642, June 2012, 4169 . 4171 [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., 4172 and K. Carlberg, "Explicit Congestion Notification (ECN) 4173 for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August 4174 2012, . 4176 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection 4177 Establishment for Media Anchoring (CEMA) for the Message 4178 Session Relay Protocol (MSRP)", RFC 6714, DOI 10.17487/ 4179 RFC6714, August 2012, 4180 . 4182 [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A 4183 Datagram Congestion Control Protocol UDP Encapsulation for 4184 NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November 4185 2012, . 4187 [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control 4188 Protocol Version 2 (MRCPv2)", RFC 6787, DOI 10.17487/ 4189 RFC6787, November 2012, 4190 . 4192 [RFC6849] Kaplan, H., Ed., Hedayat, K., Venna, N., Jones, P., and N. 4193 Stratton, "An Extension to the Session Description 4194 Protocol (SDP) and Real-time Transport Protocol (RTP) for 4195 Media Loopback", RFC 6849, DOI 10.17487/RFC6849, February 4196 2013, . 4198 [RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session 4199 Description Protocol (SDP) Media Capabilities 4200 Negotiation", RFC 6871, DOI 10.17487/RFC6871, February 4201 2013, . 4203 [RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S. 4204 Veikkolainen, "The Session Description Protocol (SDP) 4205 Alternate Connectivity (ALTC) Attribute", RFC 6947, DOI 4206 10.17487/RFC6947, May 2013, 4207 . 4209 [RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman, 4210 "Miscellaneous Capabilities Negotiation in the Session 4211 Description Protocol (SDP)", RFC 7006, DOI 10.17487/ 4212 RFC7006, September 2013, 4213 . 4215 [RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping 4216 Semantics in the Session Description Protocol", RFC 7104, 4217 DOI 10.17487/RFC7104, January 2014, 4218 . 4220 [RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session 4221 Description Protocol (SDP) Extension for Setting Audio and 4222 Video Media Streams over Circuit-Switched Bearers in the 4223 Public Switched Telephone Network (PSTN)", RFC 7195, DOI 4224 10.17487/RFC7195, May 2014, 4225 . 4227 [RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay 4228 Attribute in the Session Description Protocol", RFC 7197, 4229 DOI 10.17487/RFC7197, April 2014, 4230 . 4232 [RFC7266] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control 4233 Protocol (RTCP) Extended Report (XR) Blocks for Mean 4234 Opinion Score (MOS) Metric Reporting", RFC 7266, DOI 4235 10.17487/RFC7266, June 2014, 4236 . 4238 [RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O., 4239 Boronat, F., Montagud, M., and K. Gross, "Inter- 4240 Destination Media Synchronization (IDMS) Using the RTP 4241 Control Protocol (RTCP)", RFC 7272, DOI 10.17487/RFC7272, 4242 June 2014, . 4244 [RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H. 4245 Stokking, "RTP Clock Source Signalling", RFC 7273, DOI 4246 10.17487/RFC7273, June 2014, 4247 . 4249 [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services 4250 (Diffserv) and Real-Time Communication", RFC 7657, DOI 4251 10.17487/RFC7657, November 2015, 4252 . 4254 [T.38] "Procedures for real-time Group 3 facsimile communication 4255 over IP networks", . 4257 Author's Address 4258 Suhas Nandakumar 4259 Cisco 4260 170 West Tasman Drive 4261 San Jose, CA 95134 4262 USA 4264 Email: snandaku@cisco.com