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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 February 28, 2018 5 Expires: September 1, 2018 7 A Framework for SDP Attributes when Multiplexing 8 draft-ietf-mmusic-sdp-mux-attributes-17 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 September 1, 2018. 38 Copyright Notice 40 Copyright (c) 2018 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 . . . . . . . . . . . . . . . . . . . . . . 9 63 4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 9 64 4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 10 65 4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 11 66 4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 12 67 4.9. Category: TBD . . . . . . . . . . . . . . . . . . . . . . 12 68 5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 12 69 5.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 13 70 5.2. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 14 71 5.3. RFC5761: Multiplexing RTP and RTCP . . . . . . . . . . . 15 72 5.4. RFC3312: Integration of Resource Management and SIP . . . 15 73 5.5. RFC4574: SDP Label Attribute . . . . . . . . . . . . . . 16 74 5.6. RFC5432: QOS Mechanism Selection in SDP . . . . . . . . . 16 75 5.7. RFC4568: SDP Security Descriptions . . . . . . . . . . . 17 76 5.8. RFC5762: RTP over DCCP . . . . . . . . . . . . . . . . . 17 77 5.9. RFC6773: DCCP-UDP Encapsulation . . . . . . . . . . . . . 18 78 5.10. RFC5506: Reduced-Size RTCP in RTP Profile . . . . . . . . 19 79 5.11. RFC6787: Media Resource Control Protocol Version 2 . . . 19 80 5.12. RFC5245: ICE . . . . . . . . . . . . . . . . . . . . . . 20 81 5.13. RFC5285: RTP Header Extensions . . . . . . . . . . . . . 21 82 5.14. RFC3605: RTCP attribute in SDP . . . . . . . . . . . . . 22 83 5.15. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 22 84 5.16. RFC7273: RTP Clock Source Signalling . . . . . . . . . . 23 85 5.17. RFC6236: Image Attributes in SDP . . . . . . . . . . . . 24 86 5.18. RFC7197: Duplication Delay Attribute in SDP . . . . . . . 25 87 5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting . . . . 25 88 5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions . . 25 89 5.21. RFC6230: Media Control Channel Framework . . . . . . . . 26 90 5.22. RFC6364: SDP Elements for FEC Framework . . . . . . . . . 26 91 5.23. RFC4796: Content Attribute . . . . . . . . . . . . . . . 27 92 5.24. RFC3407: SDP Simple Capability Declaration . . . . . . . 27 93 5.25. RFC6284: Port Mapping between Unicast and Multicast RTP 94 Sessions . . . . . . . . . . . . . . . . . . . . . . . . 28 95 5.26. RFC6714: MSRP-CEMA . . . . . . . . . . . . . . . . . . . 29 96 5.27. RFC4583: SDP Format for BFCP Streams . . . . . . . . . . 29 97 5.28. RFC5547: SDP Offer/Answer for File Transfer . . . . . . . 30 98 5.29. RFC6849: SDP and RTP Media Loopback Extension . . . . . . 30 99 5.30. RFC5760: RTCP with Unicast Feedback . . . . . . . . . . . 31 100 5.31. RFC3611: RTCP XR . . . . . . . . . . . . . . . . . . . . 31 101 5.32. RFC5939: SDP Capability Negotiation . . . . . . . . . . . 32 102 5.33. RFC6871: SDP Media Capabilities Negotiation . . . . . . . 32 103 5.34. RFC7006: Miscellaneous Capabilities Negotiation SDP . . . 33 104 5.35. RFC4567: Key Management Extensions for SDP and RTSP . . . 34 105 5.36. RFC4572: Comedia over TLS in SDP . . . . . . . . . . . . 35 106 5.37. RFC4570: SDP Source Filters . . . . . . . . . . . . . . . 35 107 5.38. RFC6128: RTCP Port for Multicast Sessions . . . . . . . . 36 108 5.39. RFC6189: ZRTP . . . . . . . . . . . . . . . . . . . . . . 36 109 5.40. RFC4145: Connection-Oriented Media . . . . . . . . . . . 37 110 5.41. RFC6947: The SDP altc Attribute . . . . . . . . . . . . . 37 111 5.42. RFC7195: SDP Extension for Circuit Switched Bearers 112 in PSTN . . . . . . . . . . . . . . . . . . . . . . . . . 38 113 5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP) . . . 38 114 5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP 115 Attributes . . . . . . . . . . . . . . . . . . . . . . . 39 116 5.45. RFC6193: Media Description for IKE in SDP . . . . . . . . 39 117 5.46. RFC2326: Real Time Streaming Protocol . . . . . . . . . . 40 118 5.47. RFC6064: SDP and RTSP Extensions for 3GPP . . . . . . . . 41 119 5.48. RFC3108: ATM SDP . . . . . . . . . . . . . . . . . . . . 43 120 5.49. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 45 121 5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . . 46 122 5.51. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 46 123 5.52. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 47 124 5.53. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 47 125 5.54. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 48 126 5.55. ITU-T Q.1970 . . . . . . . . . . . . . . . . . . . . . . 50 127 5.56. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 50 128 5.57. RFC4975: The Message Session Relay Protocol . . . . . . . 51 129 5.58. Historical Attributes . . . . . . . . . . . . . . . . . . 52 130 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 52 131 6.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 53 132 6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth . . . 53 133 6.3. RFC3890: Bandwidth Modifier for SDP . . . . . . . . . . . 54 134 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 54 135 7.1. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 54 136 7.2. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 55 137 7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP 138 Sessions (RAMS) . . . . . . . . . . . . . . . . . . . . . 56 139 7.4. RFC6679: ECN for RTP over UDP/IP . . . . . . . . . . . . 56 140 7.5. RFC6642: Third-Party Loss Report . . . . . . . . . . . . 57 141 7.6. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 58 142 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 58 143 8.1. RFC5888: SDP Grouping Framework . . . . . . . . . . . . . 58 144 8.2. RFC3524: Mapping Media Streams to Resource 145 Reservation Flows . . . . . . . . . . . . . . . . . . . . 59 146 8.3. RFC4091: ANAT Semantics . . . . . . . . . . . . . . . . . 59 147 8.4. RFC5956: FEC Grouping Semantics in SDP . . . . . . . . . 59 148 8.5. RFC5583: Signaling Media Decoding Dependency in SDP . . . 60 149 8.6. RFC7104: Duplication Grouping Semantics in the SDP . . . 60 150 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 61 151 9.1. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 61 152 9.2. RFC7104: Duplication Grouping Semantics in the SDP . . . 61 153 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 62 154 10.1. RFC5432: QoS Mechanism Selection in SDP . . . . . . . . 62 155 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 62 156 11.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 63 157 12. content Attribute Analysis . . . . . . . . . . . . . . . . . 63 158 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 63 159 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 64 160 13.1. RFC5109: RTP Payload Format for Generic FEC . . . . . . 64 161 14. Multiplexing Considerations for Encapsulating Attributes . . 64 162 14.1. RFC3407: cpar Attribute Analysis . . . . . . . . . . . . 65 163 14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 65 164 14.2.1. Recommendation: Procedures for Potential 165 Configuration Pairing . . . . . . . . . . . . . . . 66 166 14.2.1.1. Example: Transport Capability Multiplexing . . . 67 167 14.2.1.2. Example: Attribute Capability Multiplexing . . . 68 168 14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 69 169 14.3.1. Recommendation: Dealing with Payload Type Numbers . 69 170 14.3.1.1. Example: Attribute Capability Under Shared 171 Payload Type . . . . . . . . . . . . . . . . . . 69 172 14.3.2. Recommendation: Dealing with Latent Configurations . 70 173 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 71 174 15.1. New 'Multiplexing Categories' subregistry . . . . . . . 71 175 15.2. 'Mux Category' column for subregistries . . . . . . . . 72 176 15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 72 177 15.2.2. Table: att-field (session level) . . . . . . . . . . 72 178 15.2.3. Table: att-field (both session and media level) . . 73 179 15.2.4. Table: att-field (media level only) . . . . . . . . 75 180 15.2.5. Table: att-field (source level) . . . . . . . . . . 78 181 15.2.6. Table: content SDP Parameters . . . . . . . . . . . 79 182 15.2.7. Table: Semantics for the 'group' SDP Attribute . . . 79 183 15.2.8. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 80 184 15.2.9. Table: 'ack' and 'nack' Attribute Values . . . . . . 80 185 15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . . 80 186 15.2.11. Table: 'cs-correlation' Attribute Values . . . . . . 81 187 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 81 188 15.2.13. Table: SDP/RTSP key management protocol identifiers 81 189 15.2.14. Table: Codec Control Messages . . . . . . . . . . . 82 190 15.2.15. Table: QoS Mechanism Tokens . . . . . . . . . . . . 82 191 15.2.16. Table: SDP Capability Negotiation Option Tags . . . 82 192 15.2.17. Table: Timestamp Reference Clock Source Parameters . 83 193 15.2.18. Table: Media Clock Source Parameters . . . . . . . . 83 194 16. Security Considerations . . . . . . . . . . . . . . . . . . . 84 195 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 84 196 18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 84 197 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 88 198 19.1. Normative References . . . . . . . . . . . . . . . . . . 88 199 19.2. Informative References . . . . . . . . . . . . . . . . . 88 200 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 97 202 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 Note: Eventhough IDENTICAL attributes must be repeated across all 369 media descriptions under multiplexing, they might not always be 370 explicitly encoded across all media descriptions. 371 [I-D.ietf-mmusic-sdp-bundle-negotiation] defines rules for when 372 attributes and their values are implicitly applied to media 373 description. 375 4.4. Category: SUM 377 The attributes in the SUM category can be set as they are normally 378 used but software using them in the multiplexing scenario MUST apply 379 the sum of all the attributes being multiplexed instead of trying to 380 use them independently. This is typically used for bandwidth or 381 other rate limiting attributes to the underlying transport. 383 The software parsing the SDP sample below, should use the aggregate 384 Application Specific (AS) bandwidth value from the individual media 385 descriptions to determine the AS value for the multiplexed session. 386 Thus the calculated AS value would be 256+64 kilobits per second for 387 the given example. 389 v=0 390 o=test 2890844526 2890842807 IN IP4 client.biloxi.example.com 391 c=IN IP4 client.biloxi.example.com 392 t=0 0 393 m=audio 49170 RTP/AVP 0 394 b=AS:64 395 m=video 51372 RTP/AVP 31 396 b=AS:256 398 4.5. Category: TRANSPORT 400 The attributes in the TRANSPORT category can be set normally for 401 multiple items in a multiplexed group but the software MUST pick the 402 one that's associated with the "m=" line whose information is used 403 for setting up the underlying transport. 405 In the example below, "a=crypto" attribute is defined for both the 406 audio and the video "m=" lines. The video media line's a=crypto 407 attribute is chosen since its mid value (bar) appears first in the 408 a=group:BUNDLE line. This is due to BUNDLE grouping semantic 409 [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values 410 from "m=" line corresponding to the mid appearing first on the 411 a=group:BUNDLE line to be considered for setting up the RTP 412 Transport. 414 v=0 415 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 416 s= 417 c=IN IP4 host.atlanta.example.com 418 t=0 0 419 a=group:BUNDLE bar foo 420 m=audio 49172 RTP/AVP 99 421 a=mid:foo 422 a=crypto:1 AES_CM_128_HMAC_SHA1_80 423 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32 424 a=rtpmap:99 iLBC/8000 425 m=video 51374 RTP/AVP 31 426 a=mid:bar 427 a=crypto:1 AES_CM_128_HMAC_SHA1_80 428 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 429 a=rtpmap:96 H261/90000 431 4.6. Category: INHERIT 433 The attributes in the INHERIT category encapsulate other SDP 434 attributes or parameters. These attributes inherit their 435 multiplexing characteristics from the attributes or parameters they 436 encapsulate. Such attributes are defined in [RFC3407], [RFC5939] and 437 [RFC6871] as part of a generic framework for indicating and 438 negotiating transport, media, and media format related capabilities 439 in the SDP. 441 The inheritance manifests itself when the encapsulated attribute or 442 parameter is being leveraged. In the case of SDP Capability 443 Negotiation [RFC5939] for example, this occurs when a capability 444 (encapsulating attribute) is used as part of a configuration; the 445 configuration inherits the multiplexing category of each of its 446 constituent (encapsulated) attributes and parameters. The inherited 447 attributes MUST be coherent in order to form a valid configuration 448 from a multiplexing point of view (see Section 14 for further 449 details). 451 v=0 452 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 453 s= 454 c=IN IP4 host.atlanta.example.com 455 t=0 0 456 m=video 3456 RTP/AVP 100 457 a=rtpmap:100 VP8/90000 458 a=fmtp:100 max-fr=30;max-fs=8040 459 a=sqn: 0 460 a=cdsc: 1 video RTP/AVP 100 461 a=cpar: a=rtcp-mux 462 m=video 3456 RTP/AVP 101 463 a=rtpmap:101 VP8/90000 464 a=fmtp:100 max-fr=15;max-fs=1200 465 a=cdsc: 2 video RTP/AVP 101 466 a=cpar: a=rtcp-mux 468 In the above example, the category IDENTICAL is inherited by the cpar 469 encapsulated rtcp-mux attribute. 471 4.7. Category: IDENTICAL-PER-PT 473 The attributes in the IDENTICAL-PER-PT category define the RTP 474 payload configuration on per Payload Type basis and MUST have 475 identical values across all the media descriptions for a given RTP 476 Payload Type when repeated. These Payload Types identify the same 477 codec configuration as defined in the Section 10.1.2 of 478 [I-D.ietf-mmusic-sdp-bundle-negotiation] under this context. 480 In the SDP example below, Payload Types 96 and 97 are repeated across 481 all the video "m=" lines and all the payload specific parameters (ex: 482 rtpmap, fmtp) are identical (Note: some line breaks included are due 483 to formatting only). 485 v=0 486 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 487 s= 488 c=IN IP4 host.atlanta.example.com 489 t=0 0 490 a=group:BUNDLE cam1 cam2 491 m=video 96 97 492 a=mid:cam1 493 a=rtpmap:96 H264/90000 494 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 495 max-mbps=108000; max-br=1000 496 a=rtpmap:97 H264/90000 497 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 498 max-mbps=7200; max-br=200 499 m=video 96 97 500 a=mid:cam2 501 a=rtpmap:96 H264/90000 502 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 503 max-mbps=108000; max-br=1000 504 a=rtpmap:97 H264/90000 505 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 506 max-mbps=7200; max-br=200 508 4.8. Category: SPECIAL 510 For the attributes in the SPECIAL category, the text in the 511 specification defining the attribute MUST be consulted for further 512 handling when multiplexed. 514 As an exampe, for the attribute extmap [RFC5285], the specification 515 defining the extension needs to be referred to understand the 516 multiplexing implications. 518 4.9. Category: TBD 520 The attributes in the TBD category have not been analyzed under the 521 proposed multiplexing framework and SHOULD NOT be multiplexed. 523 5. Analysis of Existing Attributes 525 This section analyzes attributes listed in [IANA], grouped under the 526 IETF document that defines them. 528 The "Level" column indicates whether the attribute is currently 529 specified as: 531 o S -- Session level 532 o M -- Media level 534 o B -- Both (Implies either a session level or a media level 535 attribute) 537 o SR -- Source-level (for a single SSRC) [RFC5576] 539 The "Mux Category" column identifies multiplexing category assigned 540 per attribute and the "Notes" column captures additional informative 541 details regarding the assigned category, wherever necessary. 543 5.1. RFC4566: SDP 545 [RFC4566] defines SDP that is intended for describing multimedia 546 sessions for the purposes of session announcement, session 547 invitation, and other forms of multimedia session initiation. 549 +----------------+-----------------------+-------+------------------+ 550 | Name | Notes | Level | Mux Category | 551 +----------------+-----------------------+-------+------------------+ 552 | sendrecv | Not impacted | B | NORMAL | 553 | | | | | 554 | sendonly | Not impacted | B | NORMAL | 555 | | | | | 556 | recvonly | Not impacted | B | NORMAL | 557 | | | | | 558 | inactive | Not impacted | B | NORMAL | 559 | | | | | 560 | cat | Not impacted | S | NORMAL | 561 | | | | | 562 | ptime | The attribute value | M | IDENTICAL-PER-PT | 563 | | MUST be same for a | | | 564 | | given codec | | | 565 | | configuration | | | 566 | | | | | 567 | maxptime | The attribute value | M | IDENTICAL-PER-PT | 568 | | MUST be same for a | | | 569 | | given codec | | | 570 | | configuration | | | 571 | | | | | 572 | orient | Not Impacted | M | NORMAL | 573 | | | | | 574 | framerate | The attribute value | M | IDENTICAL-PER- | 575 | | MUST be same for a | | PT | 576 | | given codec | | | 577 | | configuration | | | 578 | | | | | 579 | quality | Not Impacted | M | NORMAL | 580 | | | | | 581 | rtpmap | The attribute value | M | IDENTICAL-PER-PT | 582 | | MUST be same for a | | | 583 | | given codec | | | 584 | | configuration | | | 585 | | | | | 586 | fmtp | The attribute value | M | IDENTICAL-PER-PT | 587 | | MUST be same for a | | | 588 | | given codec | | | 589 | | configuration | | | 590 | | | | | 591 | keywds | Not impacted | S | NORMAL | 592 | | | | | 593 | type | Not Impacted | S | NORMAL | 594 | | | | | 595 | type:broadcast | Not Impacted | S | NORMAL | 596 | | | | | 597 | type:H332 | Not Impacted | S | NORMAL | 598 | | | | | 599 | type:meeting | Not Impacted | S | NORMAL | 600 | | | | | 601 | type:moderated | Not Impacted | S | NORMAL | 602 | | | | | 603 | type:test | Not Impacted | S | NORMAL | 604 | | | | | 605 | tool | Not Impacted | S | NORMAL | 606 | | | | | 607 | charset | Not Impacted | S | NORMAL | 608 | | | | | 609 | sdplang | Not Impacted | B | NORMAL | 610 | | | | | 611 | lang | Not Impacted | B | NORMAL | 612 | | | | | 613 +----------------+-----------------------+-------+------------------+ 615 5.1 RFC4566 Attribute Analysis 617 5.2. RFC4585: RTP/AVPF 619 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 620 enables receivers to provide, statistically, more immediate feedback 621 to the senders and thus allows for short-term adaptation and 622 efficient feedback-based repair mechanisms to be implemented. 624 +---------+------------------------------+-------+------------------+ 625 | Name | Notes | Level | Mux Category | 626 +---------+------------------------------+-------+------------------+ 627 | rtcp- | Since RTCP feedback | M | IDENTICAL-PER- | 628 | fb | attributes are Payload Type | | PT | 629 | | (PT) scoped, their values | | | 630 | | MUST be identical for a | | | 631 | | given PT across the | | | 632 | | multiplexed "m=" lines. | | | 633 | | | | | 634 +---------+------------------------------+-------+------------------+ 636 5.2 RFC4585 Attribute Analysis 638 5.3. RFC5761: Multiplexing RTP and RTCP 640 [RFC5761] discusses issues that arise when multiplexing RTP data 641 packets and RTP Control Protocol (RTCP) packets on a single UDP port. 642 It describes when such multiplexing is and is not appropriate, and it 643 explains how the SDP can be used to signal multiplexed sessions. 645 +----------+------------------------------------+-------+-----------+ 646 | Name | Notes | Level | Mux | 647 | | | | Category | 648 +----------+------------------------------------+-------+-----------+ 649 | rtcp- | RTP and RTCP Multiplexing affects | M | IDENTICAL | 650 | mux | the entire RTP session | | | 651 | | | | | 652 +----------+------------------------------------+-------+-----------+ 654 5.3 RFC5761 Attribute Analysis 656 5.4. RFC3312: Integration of Resource Management and SIP 658 [RFC3312] defines a generic framework for preconditions, which are 659 extensible through IANA registration. This document also discusses 660 how network quality of service can be made a precondition for 661 establishment of sessions initiated by the Session Initiation 662 Protocol (SIP). These preconditions require that the participant 663 reserve network resources before continuing with the session. 665 +-------+-----------------------+-------+--------------+ 666 | Name | Notes | Level | Mux Category | 667 +-------+-----------------------+-------+--------------+ 668 | des | Refer to notes below | M | CAUTION | 669 | | | | | 670 | conf | Refer to notes below | M | CAUTION | 671 | | | | | 672 | curr | Refer to notes below | M | CAUTION | 673 | | | | | 674 +-------+-----------------------+-------+--------------+ 676 5.4 RFC3312 Attribute Analysis 678 NOTE: A mismatched set of preconditions across media descriptions 679 results in Session establishment failures due to inability to meet 680 right resource reservations requested. 682 5.5. RFC4574: SDP Label Attribute 684 [RFC4574] defines a new SDP media-level attribute: "label". The 685 "label" attribute carries a pointer to a media stream in the context 686 of an arbitrary network application that uses SDP. The sender of the 687 SDP document can attach the "label" attribute to a particular media 688 stream or streams. The application can then use the provided pointer 689 to refer to each particular media stream in its context. 691 +--------+---------------+-------+--------------+ 692 | Name | Notes | Level | Mux Category | 693 +--------+---------------+-------+--------------+ 694 | label | Not Impacted | M | NORMAL | 695 | | | | | 696 +--------+---------------+-------+--------------+ 698 5.5 RFC4574 Attribute Analysis 700 5.6. RFC5432: QOS Mechanism Selection in SDP 702 [RFC5432] defines procedures to negotiate QOS mechanisms using the 703 SDP offer/answer model. 705 +----------------+-----------------------+-------+--------------+ 706 | Name | Notes | Level | Mux Category | 707 +----------------+-----------------------+-------+--------------+ 708 | qos-mech-send | Refer to Section 10 | B | TRANSPORT | 709 | | | | | 710 | qos-mech-recv | Refer to Section 10 | B | TRANSPORT | 711 | | | | | 712 +----------------+-----------------------+-------+--------------+ 714 5.6 RFC5432 Attribute Analysis 716 5.7. RFC4568: SDP Security Descriptions 718 [RFC4568] defines a SDP cryptographic attribute for unicast media 719 streams. The attribute describes a cryptographic key and other 720 parameters that serve to configure security for a unicast media 721 stream in either a single message or a roundtrip exchange. 723 +--------+--------------------------------------+-------+-----------+ 724 | Name | Notes | Level | Mux | 725 | | | | Category | 726 +--------+--------------------------------------+-------+-----------+ 727 | crypto | crypto attribute MUST be the one | M | TRANSPORT | 728 | | that corresponds to the "m=" line | | | 729 | | chosen for setting up the underlying | | | 730 | | transport flow | | | 731 | | | | | 732 +--------+--------------------------------------+-------+-----------+ 734 5.7 RFC4568 Attribute Analysis 736 5.8. RFC5762: RTP over DCCP 738 RTP is a widely used transport for real-time multimedia on IP 739 networks. DCCP is a transport protocol that provides desirable 740 services for real-time applications. [RFC5762] specifies a mapping 741 of RTP onto DCCP, along with associated signaling, such that real- 742 time applications can make use of the services provided by DCCP. 744 +-------------------+--------------------------+---------+----------+ 745 | Name | Notes | Current | Mux | 746 | | | | Category | 747 +-------------------+--------------------------+---------+----------+ 748 | dccp-service- | If RFC6773 is not being | M | CAUTION | 749 | code | used in addition to | | | 750 | | RFC5762, the port in the | | | 751 | | "m=" line is a DCCP | | | 752 | | port. DCCP being a | | | 753 | | connection oriented | | | 754 | | protocol does not allow | | | 755 | | multiple connections on | | | 756 | | the same 5-tuple | | | 757 | | | | | 758 +-------------------+--------------------------+---------+----------+ 760 5.8 RFC5762 Attribute Analysis 762 NOTE: If RFC6773 is being used in addition to RFC5762 and provided 763 that DCCP-in-UDP layer has additional demultiplexing, then it can be 764 possible to use different DCCP service codes for each DCCP flow, 765 given each uses a different DCCP port. Although doing so might 766 conflict with the media type of the "m=" line. None of this is 767 standardized yet and it wouldn't work as explained. Hence performing 768 multiplexing is not recommended even in this alternate scenario. 770 5.9. RFC6773: DCCP-UDP Encapsulation 772 [RFC6773] specifies an alternative encapsulation of DCCP, referred to 773 as DCCP-UDP. This encapsulation allows DCCP to be carried through 774 the current generation of Network Address Translation (NAT) middle 775 boxes without modification of those middle boxes. 777 +-----------+------------------------------------+-------+----------+ 778 | Name | Notes | Level | Mux | 779 | | | | Category | 780 +-----------+------------------------------------+-------+----------+ 781 | dccp- | Multiplexing is not recommended | M | CAUTION | 782 | port | due to potential conflict between | | | 783 | | the port used for DCCP | | | 784 | | en/decapsulation and the RTP | | | 785 | | | | | 786 +-----------+------------------------------------+-------+----------+ 788 5.9 RFC6773 Attribute Analysis 790 NOTE: RFC6773 is about tunneling DCCP in UDP, with the UDP port being 791 the port of the DCCP en-/de-capsulation service. This encapsulation 792 allows arbitrary DCCP packets to be encapsulated and the DCCP port 793 chosen can conflict with the port chosen for the RTP traffic. For 794 multiplexing several DCCP-in-UDP encapsulations on the same UDP port 795 with no RTP traffic on the same port implies collapsing several DCCP 796 port spaces together. This can or cannot work depending on the 797 nature of DCCP encapsulation and ports choices thus rendering it to 798 be very application dependent. 800 5.10. RFC5506: Reduced-Size RTCP in RTP Profile 802 [RFC5506] discusses benefits and issues that arise when allowing RTCP 803 packets to be transmitted with reduced size. 805 +------------+----------------------------------+-------+-----------+ 806 | Name | Notes | Level | Mux | 807 | | | | Category | 808 +------------+----------------------------------+-------+-----------+ 809 | rtcp- | Reduced size RTCP affects the | M | IDENTICAL | 810 | rsize | entire RTP session | | | 811 | | | | | 812 +------------+----------------------------------+-------+-----------+ 814 5.10 RFC5506 Attribute Analysis 816 5.11. RFC6787: Media Resource Control Protocol Version 2 818 The Media Resource Control Protocol Version 2 (MRCPv2) allows client 819 hosts to control media service resources such as speech synthesizers, 820 recognizers, verifiers, and identifiers residing in servers on the 821 network. MRCPv2 is not a "stand-alone" protocol -- it relies on 822 other protocols, such as the SIP, to coordinate MRCPv2 clients and 823 servers, and manage session between them, and SDP to describe, 824 discover, and exchange capabilities. It also depends on SIP and SDP 825 to establish the media sessions and associated parameters between the 826 media source or sink and the media server. Once this is done, the 827 MRCPv2 exchange operates over the control session established above, 828 allowing the client to control the media processing resources on the 829 speech resource server. [RFC6787] defines attributes for this 830 purpose. 832 +-----------+---------------+-------+--------------+ 833 | Name | Notes | Level | Mux Category | 834 +-----------+---------------+-------+--------------+ 835 | resource | Not Impacted | M | NORMAL | 836 | | | | | 837 | channel | Not Impacted | M | NORMAL | 838 | | | | | 839 | cmid | Not Impacted | M | NORMAL | 840 | | | | | 841 +-----------+---------------+-------+--------------+ 843 5.11 RFC6787 Attribute Analysis 845 5.12. RFC5245: ICE 847 [RFC5245] describes a protocol for NAT traversal for UDP-based 848 multimedia sessions established with the offer/answer model. ICE 849 makes use of the Session Traversal Utilities for NAT (STUN) protocol 850 and its extension, Traversal Using Relay NAT (TURN). ICE can be used 851 by any protocol utilizing the offer/answer model, such as the SIP. 853 +-------------------+---------------------------+-------+-----------+ 854 | Name | Notes | Level | Mux | 855 | | | | Category | 856 +-------------------+---------------------------+-------+-----------+ 857 | ice-lite | Not Impacted | S | NORMAL | 858 | | | | | 859 | ice-options | Not Impacted | S | NORMAL | 860 | | | | | 861 | ice-mismatch | Not Impacted | S | NORMAL | 862 | | | | | 863 | ice-pwd | ice-pwd MUST be the one | B | TRANSPORT | 864 | | that corresponds to the | | | 865 | | "m=" line chosen for | | | 866 | | setting up the underlying | | | 867 | | transport flow | | | 868 | | | | | 869 | ice-ufrag | ice-ufrag MUST be the one | B | TRANSPORT | 870 | | that corresponds to the | | | 871 | | "m=" line chosen for | | | 872 | | setting up the underlying | | | 873 | | transport flow | | | 874 | | | | | 875 | candidate | ice candidate MUST be the | M | TRANSPORT | 876 | | one that corresponds to | | | 877 | | the "m=" line chosen for | | | 878 | | setting up the underlying | | | 879 | | transport flow | | | 880 | | | | | 881 | remote- | ice remote candidate MUST | M | TRANSPORT | 882 | candidates | be the one that | | | 883 | | corresponds to the "m=" | | | 884 | | line chosen for setting | | | 885 | | up the underlying | | | 886 | | transport flow | | | 887 | | | | | 888 +-------------------+---------------------------+-------+-----------+ 890 5.12 RFC5245 Attribute Analysis 892 5.13. RFC5285: RTP Header Extensions 894 [RFC5285] provides a general mechanism to use the header extension 895 feature of RTP. It provides the option to use a small number of 896 small extensions in each RTP packet, where the universe of possible 897 extensions is large and registration is de-centralized. The actual 898 extensions in use in a session are signaled in the setup information 899 for that session. 901 +--------+---------------------------------------+-------+----------+ 902 | Name | Notes | Level | Mux | 903 | | | | Category | 904 +--------+---------------------------------------+-------+----------+ 905 | extmap | Refer to the document defining the | B | SPECIAL | 906 | | specific RTP Extension | | | 907 | | | | | 908 +--------+---------------------------------------+-------+----------+ 910 5.13 RFC5285 Attribute Analysis 912 5.14. RFC3605: RTCP attribute in SDP 914 Originally, SDP assumed that RTP and RTCP were carried on consecutive 915 ports. However, this is not always true when NATs are involved. 916 [RFC3605] specifies an early mechanism to indicate the RTCP port. 918 +------+----------------------------------------+-------+-----------+ 919 | Name | Notes | Level | Mux | 920 | | | | Category | 921 +------+----------------------------------------+-------+-----------+ 922 | rtcp | RTCP Port MUST be the one that | M | TRANSPORT | 923 | | corresponds to the "m=" line chosen | | | 924 | | for setting up the underlying | | | 925 | | transport flow. | | | 926 | | | | | 927 +------+----------------------------------------+-------+-----------+ 929 5.14 RFC3605 Attribute Analysis 931 5.15. RFC5576: Source-Specific SDP Attributes 933 [RFC5576] defines a mechanism to describe RTP media sources, which 934 are identified by their synchronization source (SSRC) identifiers, in 935 SDP, to associate attributes with these sources, and to express 936 relationships among sources. It also defines several source-level 937 attributes that can be used to describe properties of media sources. 939 +---------------+------------------------+-------+------------------+ 940 | Name | Notes | Level | Mux Category | 941 +---------------+------------------------+-------+------------------+ 942 | ssrc | Refer to Notes below | M | NORMAL | 943 | | | | | 944 | ssrc-group | Refer to Section 9 for | M | NORMAL | 945 | | specific analysis of | | | 946 | | the grouping | | | 947 | | semantics | | | 948 | | | | | 949 | cname | Not Impacted | SR | NORMAL | 950 | | | | | 951 | previous- | Refer to notes below | SR | NORMAL | 952 | ssrc | | | | 953 | | | | | 954 | fmtp | The attribute value | SR | IDENTICAL-PER- | 955 | | MUST be same for a | | PT | 956 | | given codec | | | 957 | | configuration | | | 958 | | | | | 959 +---------------+------------------------+-------+------------------+ 961 5.15 RFC5576 Attribute Analysis 963 NOTE: If SSRCs are repeated across "m=" lines being multiplexed, they 964 MUST all represent the same underlying RTP Source. 966 5.16. RFC7273: RTP Clock Source Signalling 968 [RFC7273] specifies SDP signalling that identifies timestamp 969 reference clock sources and SDP signalling that identifies the media 970 clock sources in a multimedia session. 972 +--------------------+---------------+-------+--------------+ 973 | Name | Notes | Level | Mux Category | 974 +--------------------+---------------+-------+--------------+ 975 | ts-refclk | Not Impacted | B | NORMAL | 976 | | | | | 977 | mediaclk | Not Impacted | B | NORMAL | 978 | | | | | 979 | ts-refclk:ntp | Not Impacted | B | NORMAL | 980 | | | | | 981 | ts-refclk:ptp | Not Impacted | B | NORMAL | 982 | | | | | 983 | ts-refclk:gps | Not Impacted | B | NORMAL | 984 | | | | | 985 | ts-refclk:gal | Not Impacted | B | NORMAL | 986 | | | | | 987 | ts-refclk:glonass | Not Impacted | B | NORMAL | 988 | | | | | 989 | ts-refclk:local | Not Impacted | B | NORMAL | 990 | | | | | 991 | ts-refclk:private | Not Impacted | B | NORMAL | 992 | | | | | 993 | mediaclk:sender | Not Impacted | B | NORMAL | 994 | | | | | 995 | mediaclk:direct | Not Impacted | B | NORMAL | 996 | | | | | 997 | mediaclk:IEEE1722 | Not Impacted | B | NORMAL | 998 | | | | | 999 +--------------------+---------------+-------+--------------+ 1001 5.16 RFC7273 Attribute Analysis 1003 5.17. RFC6236: Image Attributes in SDP 1005 [RFC6236] proposes a new generic session setup attribute to make it 1006 possible to negotiate different image attributes such as image size. 1007 A possible use case is to make it possible for a low-end hand-held 1008 terminal to display video without the need to rescale the image, 1009 something that may consume large amounts of memory and processing 1010 power. The document also helps to maintain an optimal bitrate for 1011 video as only the image size that is desired by the receiver is 1012 transmitted. 1014 +-----------+----------------------------+-------+------------------+ 1015 | Name | Notes | Level | Mux Category | 1016 +-----------+----------------------------+-------+------------------+ 1017 | imageattr | The attribute value MUST | M | IDENTICAL-PER- | 1018 | | be same for a given codec | | PT | 1019 | | configuration | | | 1020 | | | | | 1021 +-----------+----------------------------+-------+------------------+ 1023 5.17 RFC6236 Attribute Analysis 1025 5.18. RFC7197: Duplication Delay Attribute in SDP 1027 [RFC7197] defines an attribute to indicate the presence of temporally 1028 redundant media streams and the duplication delay in SDP. 1030 +--------------------+---------------+-------+--------------+ 1031 | Name | Notes | Level | Mux Category | 1032 +--------------------+---------------+-------+--------------+ 1033 | duplication-delay | Not Impacted | B | NORMAL | 1034 | | | | | 1035 +--------------------+---------------+-------+--------------+ 1037 5.18 RFC7197 Attribute Analysis 1039 5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting 1041 [RFC7266] defines an RTCP Extended Report (XR) Block including two 1042 new segment types and associated SDP parameters that allow the 1043 reporting of mean opinion score (MOS) Metrics for use in a range of 1044 RTP applications. 1046 +-------------+---------------+-------+--------------+ 1047 | Name | Notes | Level | Mux Category | 1048 +-------------+---------------+-------+--------------+ 1049 | calgextmap | Not Impacted | B | NORMAL | 1050 | | | | | 1051 +-------------+---------------+-------+--------------+ 1053 5.19 RFC7266 Attribute Analysis 1055 5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions 1057 [RFC6285] describes a method using the existing RTP and RTCP 1058 machinery that reduces the acquisition delay. In this method, an 1059 auxiliary unicast RTP session carrying the Reference Information to 1060 the receiver precedes or accompanies the multicast stream. This 1061 unicast RTP flow can be transmitted at a faster than natural bitrate 1062 to further accelerate the acquisition. The motivating use case for 1063 this capability is multicast applications that carry real-time 1064 compressed audio and video. 1066 +---------------+------------------+-------+--------------+ 1067 | Name | Notes | Level | Mux Category | 1068 +---------------+------------------+-------+--------------+ 1069 | rams-updates | Not recommended | M | CAUTION | 1070 | | | | | 1071 +---------------+------------------+-------+--------------+ 1073 5.20 RFC6285 Attribute Analysis 1075 5.21. RFC6230: Media Control Channel Framework 1077 [RFC6230] describes a framework and protocol for application 1078 deployment where the application programming logic and media 1079 processing are distributed. This implies that application 1080 programming logic can seamlessly gain access to appropriate resources 1081 that are not co-located on the same physical network entity. The 1082 framework uses SIP to establish an application-level control 1083 mechanism between application servers and associated external servers 1084 such as media servers. 1086 +---------+---------------+-------+--------------+ 1087 | Name | Notes | Level | Mux Category | 1088 +---------+---------------+-------+--------------+ 1089 | cfw-id | Not Impacted | M | NORMAL | 1090 | | | | | 1091 +---------+---------------+-------+--------------+ 1093 5.21 RFC6230 Attribute Analysis 1095 5.22. RFC6364: SDP Elements for FEC Framework 1097 [RFC6364] specifies the use of SDP to describe the parameters 1098 required to signal the Forward Error Correction (FEC) Framework 1099 Configuration Information between the sender(s) and receiver(s). 1100 This document also provides examples that show the semantics for 1101 grouping multiple source and repair flows together for the 1102 applications that simultaneously use multiple instances of the FEC 1103 Framework. 1105 +-----------------+------------------------------+-------+----------+ 1106 | Name | Notes | Level | Mux | 1107 | | | | Category | 1108 +-----------------+------------------------------+-------+----------+ 1109 | fec-source- | Refer to the document | M | SPECIAL | 1110 | flow | defining specific FEC | | | 1111 | | Scheme | | | 1112 | | | | | 1113 | fec-repair- | Refer to the document | M | SPECIAL | 1114 | flow | defining specific FEC | | | 1115 | | Scheme | | | 1116 | | | | | 1117 | repair-window | Refer to the document | M | SPECIAL | 1118 | | defining specific FEC | | | 1119 | | Scheme | | | 1120 | | | | | 1121 +-----------------+------------------------------+-------+----------+ 1123 5.22 RFC6364 Attribute Analysis 1125 5.23. RFC4796: Content Attribute 1127 [RFC4796] defines a new SDP media-level attribute, 'content'. The 1128 'content' attribute defines the content of the media stream to a more 1129 detailed level than the media description line. The sender of an SDP 1130 session description can attach the 'content' attribute to one or more 1131 media streams. The receiving application can then treat each media 1132 stream differently (e.g., show it on a big or small screen) based on 1133 its content. 1135 +----------+---------------+-------+--------------+ 1136 | Name | Notes | Level | Mux Category | 1137 +----------+---------------+-------+--------------+ 1138 | content | Not Impacted | M | NORMAL | 1139 | | | | | 1140 +----------+---------------+-------+--------------+ 1142 5.23 RFC4796 Attribute Analysis 1144 5.24. RFC3407: SDP Simple Capability Declaration 1146 [RFC3407] defines a set of SDP attributes that enables SDP to provide 1147 a minimal and backwards compatible capability declaration mechanism. 1149 +----------+------------------------+-------+--------------+ 1150 | Name | Notes | Level | Mux Category | 1151 +----------+------------------------+-------+--------------+ 1152 | sqn | Not Impacted | B | NORMAL | 1153 | | | | | 1154 | cdsc | Not Impacted. | B | NORMAL | 1155 | | | | | 1156 | cpar | Refer to Section 14 | B | INHERIT | 1157 | | | | | 1158 | cparmin | Refer to notes below | B | SPECIAL | 1159 | | | | | 1160 | cparmax | Refer to notes below | B | SPECIAL | 1161 | | | | | 1162 +----------+------------------------+-------+--------------+ 1164 5.24 RFC3407 Attribute Analysis 1166 NOTE: The attributes (a=cparmin and a=cparmax) define minimum and 1167 maximum numerical values associated with the attributes described in 1168 a=cpar. 1170 Since the cpar attribute can either define a 'b=' attribute or any 1171 'a=' attribute, the multiplexing category depends on actual attribute 1172 being encapsulated and the implications of the numerical values 1173 assigned. Hence it is recommended to consult the specification 1174 defining attributes (cparmin/cparmax) to further analyze their 1175 behavior under multiplexing. 1177 5.25. RFC6284: Port Mapping between Unicast and Multicast RTP Sessions 1179 [RFC6284] presents a port mapping solution that allows RTP receivers 1180 to choose their own ports for an auxiliary unicast session in RTP 1181 applications using both unicast and multicast services. The solution 1182 provides protection against denial-of-service or packet amplification 1183 attacks that could be used to cause one or more RTP packets to be 1184 sent to a victim client. 1186 +-----------------+------------------------------+-------+----------+ 1187 | Name | Notes | Level | Mux | 1188 | | | | Category | 1189 +-----------------+------------------------------+-------+----------+ 1190 | portmapping- | Not recommended, if port | M | CAUTION | 1191 | req | mapping is required by the | | | 1192 | | application | | | 1193 | | | | | 1194 +-----------------+------------------------------+-------+----------+ 1196 5.25 RFC6284 Attribute Analysis 1198 5.26. RFC6714: MSRP-CEMA 1200 [RFC6714] defines a Message Session Relay Protocol (MSRP) extension, 1201 Connection Establishment for Media Anchoring (CEMA). Support of this 1202 extension is optional. The extension allows middle boxes to anchor 1203 the MSRP connection, without the need for middle boxes to modify the 1204 MSRP messages; thus, it also enables secure end-to-end MSRP 1205 communication in networks where such middle boxes are deployed. This 1206 document also defines a SDP attribute, 'msrp-cema', that MSRP 1207 endpoints use to indicate support of the CEMA extension. 1209 +------------+-----------------------+-------+--------------+ 1210 | Name | Notes | Level | Mux Category | 1211 +------------+-----------------------+-------+--------------+ 1212 | msrp-cema | Refer to notes below | M | TBD | 1213 | | | | | 1214 +------------+-----------------------+-------+--------------+ 1216 5.26 RFC6714 Attribute Analysis 1218 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1219 there exists no publicly available specification that defines 1220 procedures for multiplexing/demultiplexing MRSP flows over a single 1221 5-tuple. Once such a specification is available, the multiplexing 1222 categories assignments for the attributes in this section could be 1223 revisited. 1225 5.27. RFC4583: SDP Format for BFCP Streams 1227 [RFC4583] document specifies how to describe Binary Floor Control 1228 Protocol (BFCP) streams in SDP descriptions. User agents using the 1229 offer/answer model to establish BFCP streams use this format in their 1230 offers and answers. 1232 +------------+-----------------------+-------+--------------+ 1233 | Name | Notes | Level | Mux Category | 1234 +------------+-----------------------+-------+--------------+ 1235 | floorctrl | Refer to notes below | M | TBD | 1236 | | | | | 1237 | confid | Not Impacted | M | NORMAL | 1238 | | | | | 1239 | userid | Not Impacted | M | NORMAL | 1240 | | | | | 1241 | floorid | Not Impacted | M | NORMAL | 1242 | | | | | 1243 +------------+-----------------------+-------+--------------+ 1245 5.27 RFC4583 Attribute Analysis 1247 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1248 there exists no publicly available specification that defines 1249 procedures for multiplexing/demultiplexing BFCP streams over a single 1250 5-tuple. Once such a specification is available, the multiplexing 1251 categories assignments for the attributes in this section could be 1252 revisited. 1254 5.28. RFC5547: SDP Offer/Answer for File Transfer 1256 [RFC5547] provides a mechanism to negotiate the transfer of one or 1257 more files between two endpoints by using the SDP offer/answer model 1258 specified in [RFC3264]. 1260 +-------------------+-----------------------+-------+--------------+ 1261 | Name | Notes | Level | Mux Category | 1262 +-------------------+-----------------------+-------+--------------+ 1263 | file-selector | Refer to notes below | M | TBD | 1264 | | | | | 1265 | file-transfer-id | Refer to notes below | M | TBD | 1266 | | | | | 1267 | file-disposition | Refer to notes below | M | TBD | 1268 | | | | | 1269 | file-date | Refer to notes below | M | TBD | 1270 | | | | | 1271 | file-icon | Refer to notes below | M | TBD | 1272 | | | | | 1273 | file-range | Refer to notes below | M | TBD | 1274 | | | | | 1275 +-------------------+-----------------------+-------+--------------+ 1277 5.28 RFC5547 Attribute Analysis 1279 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1280 there exists no publicly available specification that defines 1281 procedures for multiplexing/demultiplexing MRSP flows over a single 1282 5-tuple. Once such a specification is available, the multiplexing 1283 categories assignments for attributes in this section could be 1284 revisited. 1286 5.29. RFC6849: SDP and RTP Media Loopback Extension 1288 [RFC6849] adds new SDP media types and attributes, which enable 1289 establishment of media sessions where the media is looped back to the 1290 transmitter. Such media sessions will serve as monitoring and 1291 troubleshooting tools by providing the means for measurement of more 1292 advanced Voice over IP (VoIP), Real-time Text, and Video over IP 1293 performance metrics. 1295 +--------------------+-------------------+-------+------------------+ 1296 | Name | Notes | Level | Mux Category | 1297 +--------------------+-------------------+-------+------------------+ 1298 | loopback rtp-pkt- | The attribute | M | IDENTICAL-PER- | 1299 | loopback | value MUST be | | PT | 1300 | | same for a given | | | 1301 | | codec | | | 1302 | | configuration | | | 1303 | | | | | 1304 | loopback rtp- | The attribute | M | IDENTICAL-PER- | 1305 | media-loopback | value MUST be | | PT | 1306 | | same for a given | | | 1307 | | codec | | | 1308 | | configuration | | | 1309 | | | | | 1310 | loopback-source | Not Impacted | M | NORMAL | 1311 | | | | | 1312 | loopback-mirror | Not Impacted | M | NORMAL | 1313 | | | | | 1314 +--------------------+-------------------+-------+------------------+ 1316 5.29 RFC6849 Analysis 1318 5.30. RFC5760: RTCP with Unicast Feedback 1320 [RFC5760] specifies an extension to RTCP to use unicast feedback to a 1321 multicast sender. The proposed extension is useful for single-source 1322 multicast sessions such as Source-Specific Multicast (SSM) 1323 communication where the traditional model of many-to-many group 1324 communication is either not available or not desired. 1326 +--------------+--------------------------------+-------+-----------+ 1327 | Name | Notes | Level | Mux | 1328 | | | | Category | 1329 +--------------+--------------------------------+-------+-----------+ 1330 | rtcp- | The attribute MUST be reported | M | IDENTICAL | 1331 | unicast | across all "m=" lines | | | 1332 | | multiplexed | | | 1333 | | | | | 1334 +--------------+--------------------------------+-------+-----------+ 1336 5.30 RFC5760 Attribute Analysis 1338 5.31. RFC3611: RTCP XR 1340 [RFC3611] defines the Extended Report (XR) packet type for RTCP, and 1341 defines how the use of XR packets can be signaled by an application 1342 if it employs the Session Description Protocol (SDP). 1344 +----------+---------------+-------+--------------+ 1345 | Name | Notes | Level | Mux Category | 1346 +----------+---------------+-------+--------------+ 1347 | rtcp-xr | Not Impacted | B | NORMAL | 1348 | | | | | 1349 +----------+---------------+-------+--------------+ 1351 5.31 RFC3611 Attribute Analysis 1353 5.32. RFC5939: SDP Capability Negotiation 1355 [RFC5939] defines a general SDP Capability Negotiation framework. It 1356 also specifies how to provide attributes and transport protocols as 1357 capabilities and negotiate them using the framework. Extensions for 1358 other types of capabilities (e.g., media types and media formats) may 1359 be provided in other documents. 1361 +---------+-----------------------+-------+--------------+ 1362 | Name | Notes | Level | Mux Category | 1363 +---------+-----------------------+-------+--------------+ 1364 | pcfg | Refer to Section 14 | M | SPECIAL | 1365 | | | | | 1366 | acfg | Refer to Section 14 | M | SPECIAL | 1367 | | | | | 1368 | csup | Not Impacted | B | NORMAL | 1369 | | | | | 1370 | creq | Not Impacted | B | NORMAL | 1371 | | | | | 1372 | acap | Refer to Section 14 | B | INHERIT | 1373 | | | | | 1374 | tcap | Refer to Section 14 | B | INHERIT | 1375 | | | | | 1376 | cap-v0 | Not Impacted | B | NORMAL | 1377 | | | | | 1378 +---------+-----------------------+-------+--------------+ 1380 5.32 RFC5939 Attribute Analysis 1382 5.33. RFC6871: SDP Media Capabilities Negotiation 1384 SDP capability negotiation provides a general framework for 1385 indicating and negotiating capabilities in SDP. The base framework 1386 defines only capabilities for negotiating transport protocols and 1387 attributes. [RFC6871] extends the framework by defining media 1388 capabilities that can be used to negotiate media types and their 1389 associated parameters. 1391 +---------+-----------------------+-------+-------------------+ 1392 | Name | Notes | Level | Mux Category | 1393 +---------+-----------------------+-------+-------------------+ 1394 | rmcap | Refer to Section 14 | B | IDENTICAL-PER-PT | 1395 | | | | | 1396 | omcap | Not Impacted | B | NORMAL | 1397 | | | | | 1398 | mfcap | Refer to Section 14 | B | IDENTICAL-PER-PT | 1399 | | | | | 1400 | mscap | Refer to Section 14 | B | INHERIT | 1401 | | | | | 1402 | lcfg | Refer to Section 14 | B | SPECIAL | 1403 | | | | | 1404 | sescap | Refer to notes below | S | CAUTION | 1405 | | | | | 1406 | med-v0 | Not Impacted | S | NORMAL | 1407 | | | | | 1408 +---------+-----------------------+-------+-------------------+ 1410 5.33 RFC6871 - Attribute Analysis 1412 NOTE: The "sescap" attribute is not recommended for use with 1413 multiplexing. The reason is that it requires the use of unique 1414 configuration numbers across the entire SDP (per [RFC6871]) as 1415 opposed to within a media description only (per [RFC5939]). As 1416 described in Section 14, the use of identical configuration numbers 1417 between multiplexed (bundled) media descriptions is the default way 1418 of indicating compatible configurations in a bundle. 1420 5.34. RFC7006: Miscellaneous Capabilities Negotiation SDP 1422 [RFC7006] extends the SDP capability negotiation framework to allow 1423 endpoints to negotiate three additional SDP capabilities. In 1424 particular, this memo provides a mechanism to negotiate bandwidth 1425 ("b=" line), connection data ("c=" line), and session or media titles 1426 ("i=" line for each session or media). 1428 +---------+-------------------------------------+-------+-----------+ 1429 | Name | Notes | Level | Mux | 1430 | | | | Category | 1431 +---------+-------------------------------------+-------+-----------+ 1432 | bcap | Inherit the category SUM as | B | INHERIT | 1433 | | applicable to b= attribute | | | 1434 | | | | | 1435 | bcap-v0 | Not Impacted | B | NORMAL | 1436 | | | | | 1437 | ccap | The connection address type MUST be | B | IDENTICAL | 1438 | | identical across all the | | | 1439 | | multiplexed "m=" lines | | | 1440 | | | | | 1441 | ccap-v0 | Not Impacted | B | NORMAL | 1442 | | | | | 1443 | icap | Not Impacted | B | NORMAL | 1444 | | | | | 1445 | icap-v0 | Not Impacted | B | NORMAL | 1446 | | | | | 1447 +---------+-------------------------------------+-------+-----------+ 1449 5.34 RFC7006 - Attribute Analysis 1451 5.35. RFC4567: Key Management Extensions for SDP and RTSP 1453 [RFC4567] defines general extensions for SDP and Real Time Streaming 1454 Protocol (RTSP) to carry messages, as specified by a key management 1455 protocol, in order to secure the media. These extensions are 1456 presented as a framework, to be used by one or more key management 1457 protocols. As such, their use is meaningful only when complemented 1458 by an appropriate key management protocol. 1460 +----------+------------------------------------+-------+-----------+ 1461 | Name | Notes | Level | Mux | 1462 | | | | Category | 1463 +----------+------------------------------------+-------+-----------+ 1464 | key- | Key management protocol MUST be | B | IDENTICAL | 1465 | mgmt | identical across all the "m=" | | | 1466 | | lines | | | 1467 | | | | | 1468 | mikey | Key management protocol MUST be | B | IDENTICAL | 1469 | | identical across all the "m=" | | | 1470 | | lines | | | 1471 | | | | | 1472 +----------+------------------------------------+-------+-----------+ 1474 5.35 RFC4567 Attribute Analysis 1476 5.36. RFC4572: Comedia over TLS in SDP 1478 [RFC4572] specifies how to establish secure connection-oriented media 1479 transport sessions over the Transport Layer Security (TLS) protocol 1480 using SDP. It defines a new SDP protocol identifier, 'TCP/TLS'. It 1481 also defines the syntax and semantics for an SDP 'fingerprint' 1482 attribute that identifies the certificate that will be presented for 1483 the TLS session. This mechanism allows media transport over TLS 1484 connections to be established securely, so long as the integrity of 1485 session descriptions is assured. 1487 +-------------+---------------------------------+-------+-----------+ 1488 | Name | Notes | Level | Mux | 1489 | | | | Category | 1490 +-------------+---------------------------------+-------+-----------+ 1491 | fingerprint | fingerprint value MUST be the | B | TRANSPORT | 1492 | | one that corresponds to the | | | 1493 | | "m=" line chosen for setting up | | | 1494 | | the underlying transport flow | | | 1495 | | | | | 1496 +-------------+---------------------------------+-------+-----------+ 1498 5.36 RFC4572 Attribute Analysis 1500 5.37. RFC4570: SDP Source Filters 1502 [RFC4570] describes how to adapt SDP to express one or more source 1503 addresses as a source filter for one or more destination "connection" 1504 addresses. It defines the syntax and semantics for an SDP "source- 1505 filter" attribute that may reference either IPv4 or IPv6 address(es) 1506 as either an inclusive or exclusive source list for either multicast 1507 or unicast destinations. In particular, an inclusive source-filter 1508 can be used to specify a Source-Specific Multicast (SSM) session. 1510 +---------------+-------------------------------+-------+-----------+ 1511 | Name | Notes | Level | Mux | 1512 | | | | Category | 1513 +---------------+-------------------------------+-------+-----------+ 1514 | source- | The attribute MUST be | B | IDENTICAL | 1515 | filter | repeated across all "m=" | | | 1516 | | lines multiplexed | | | 1517 | | | | | 1518 +---------------+-------------------------------+-------+-----------+ 1520 5.37 RFC4570 Attribute Analysis 1522 5.38. RFC6128: RTCP Port for Multicast Sessions 1524 SDP has an attribute that allows RTP applications to specify an 1525 address and a port associated with the RTCP traffic. In RTP-based 1526 source-specific multicast (SSM) sessions, the same attribute is used 1527 to designate the address and the RTCP port of the Feedback Target in 1528 the SDP description. However, the RTCP port associated with the SSM 1529 session itself cannot be specified by the same attribute to avoid 1530 ambiguity, and thus, is required to be derived from the "m=" line of 1531 the media description. Deriving the RTCP port from the "m=" line 1532 imposes an unnecessary restriction. [RFC6128] removes this 1533 restriction by introducing a new SDP attribute. 1535 +----------------+------------------------------+-------+-----------+ 1536 | Name | Notes | Level | Mux | 1537 | | | | Category | 1538 +----------------+------------------------------+-------+-----------+ 1539 | multicast- | Multicast RTCP port MUST be | B | IDENTICAL | 1540 | rtcp | identical across all the | | | 1541 | | "m=" lines | | | 1542 | | | | | 1543 +----------------+------------------------------+-------+-----------+ 1545 5.38 RFC6128 Attribute Analysis 1547 5.39. RFC6189: ZRTP 1549 [RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman 1550 exchange to agree on a session key and parameters for establishing 1551 unicast SRTP sessions for (VoIP applications. 1553 +-----------+-----------------------------------+-------+-----------+ 1554 | Name | Notes | Level | Mux | 1555 | | | | Category | 1556 +-----------+-----------------------------------+-------+-----------+ 1557 | zrtp- | zrtp-hash attribute MUST be the | M | TRANSPORT | 1558 | hash | one that corresponds to the "m=" | | | 1559 | | line chosen for setting up the | | | 1560 | | underlying transport flow | | | 1561 | | | | | 1562 +-----------+-----------------------------------+-------+-----------+ 1564 5.39 RFC6189 Attribute Analysis 1566 5.40. RFC4145: Connection-Oriented Media 1568 [RFC4145] describes how to express media transport over TCP using 1569 SDP. It defines the SDP 'TCP' protocol identifier, the SDP 'setup' 1570 attribute, which describes the connection setup procedure, and the 1571 SDP 'connection' attribute, which handles connection reestablishment. 1573 +------------+----------------------------------+-------+-----------+ 1574 | Name | Notes | Level | Mux | 1575 | | | | Category | 1576 +------------+----------------------------------+-------+-----------+ 1577 | setup | The setup attribute MUST be the | B | TRANSPORT | 1578 | | one that corresponds to the "m=" | | | 1579 | | line chosen for setting up the | | | 1580 | | underlying transport flow. | | | 1581 | | | | | 1582 | connection | The connection attribute MUST be | B | TRANSPORT | 1583 | | the one that corresponds to the | | | 1584 | | "m=" line chosen for setting up | | | 1585 | | the underlying transport flow. | | | 1586 | | | | | 1587 +------------+----------------------------------+-------+-----------+ 1589 5.40 RFC4145 Attribute Analysis 1591 5.41. RFC6947: The SDP altc Attribute 1593 [RFC6947] proposes a mechanism that allows the same SDP offer to 1594 carry multiple IP addresses of different address families (e.g., IPv4 1595 and IPv6). The proposed attribute, the "altc" attribute, solves the 1596 backward-compatibility problem that plagued Alternative Network 1597 Address Types (ANAT) due to their syntax. 1599 +------+----------------------------------------+-------+-----------+ 1600 | Name | Notes | Level | Mux | 1601 | | | | Category | 1602 +------+----------------------------------------+-------+-----------+ 1603 | altc | The IP Address and port MUST be the | M | TRANSPORT | 1604 | | one that corresponds to the "m=" line | | | 1605 | | chosen for setting up the underlying | | | 1606 | | transport flow | | | 1607 | | | | | 1608 +------+----------------------------------------+-------+-----------+ 1610 5.41 RFC6947 Attribute Analysis 1612 5.42. RFC7195: SDP Extension for Circuit Switched Bearers in PSTN 1614 [RFC7195] describes use cases, requirements, and protocol extensions 1615 for using SDP offer/answer model for establishing audio and video 1616 media streams over circuit-switched bearers in the Public Switched 1617 Telephone Network (PSTN). 1619 +-------------------------+-------------------+-------+-------------+ 1620 | Name | Notes | Level | Mux | 1621 | | | | Category | 1622 +-------------------------+-------------------+-------+-------------+ 1623 | cs- | Refer to notes | M | TBD | 1624 | correlation:callerid | below | | | 1625 | | | | | 1626 | cs-correlation:uuie | Refer to notes | M | TBD | 1627 | | below | | | 1628 | | | | | 1629 | cs-correlation:dtmf | Refer to notes | M | TBD | 1630 | | below | | | 1631 | | | | | 1632 | cs- | Refer to notes | M | TBD | 1633 | correlation:external | below | | | 1634 | | | | | 1635 +-------------------------+-------------------+-------+-------------+ 1637 5.42 RFC7195 Attribute Analysis 1639 NOTE: [RFC7195] defines SDP attributes for establishing audio and 1640 video media streams over circuit-switched bearers by defining a new 1641 nettype value "PSTN". However, section 7.2 of 1642 [I-D.ietf-mmusic-sdp-bundle-negotiation] requires the "c=" line 1643 nettype value of "IN". If in future there exists a specification 1644 that defines procedures to multiplex media streams over nettype 1645 "PSTN", the multiplexing categories for attributes in this section 1646 could be revisited. 1648 5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP) 1650 [RFC7272] defines a new RTCP Packet Type and an RTCP Extended Report 1651 (XR) Block Type to be used for achieving Inter-Destination Media 1652 Synchronization (IDMS). 1654 +------------+---------------+-------+--------------+ 1655 | Name | Notes | Level | Mux Category | 1656 +------------+---------------+-------+--------------+ 1657 | rtcp-idms | Not Impacted | M | NORMAL | 1658 | | | | | 1659 +------------+---------------+-------+--------------+ 1661 5.43 RFC7272 Attribute Analysis 1663 5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP 1664 Attributes 1666 [RFC5159] provides descriptions of SDP attributes used by the Open 1667 Mobile Alliance's Broadcast Service and Content Protection 1668 specification. 1670 +--------------------+-----------------------+-------+--------------+ 1671 | Name | Notes | Level | Mux 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- | Unlikely to use IKE in the | B | CAUTION | 1710 | udpencap | 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 | Refer to | M | CAUTION | 1842 | Status | 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 Category | 1861 +-----------------------+--------------------+-------+--------------+ 1862 | aalType | Refer to notes | B | CAUTION | 1863 | | below | | | 1864 | eecid | Refer to notes | B | CAUTION | 1865 | | below | | | 1866 | capability | Refer to notes | B | CAUTION | 1867 | | below | | | 1868 | qosClass | Refer to notes | B | CAUTION | 1869 | | below | | | 1870 | bcob | Refer to notes | B | CAUTION | 1871 | | below | | | 1872 | stc | Refer to notes | B | CAUTION | 1873 | | below | | | 1874 | upcc | Refer to notes | B | CAUTION | 1875 | | below | | | 1876 | atmQOSparms | Refer to notes | B | CAUTION | 1877 | | below | | | 1878 | atmTrfcDesc | Refer to notes | B | CAUTION | 1879 | | below | | | 1880 | abrParms | Refer to notes | B | CAUTION | 1881 | | below | | | 1882 | abrSetup | Refer to notes | B | CAUTION | 1883 | | below | | | 1884 | bearerType | Refer to notes | B | CAUTION | 1885 | | below | | | 1886 | lij | Refer to notes | B | CAUTION | 1887 | | below | | | 1888 | anycast | Refer to notes | B | CAUTION | 1889 | | below | | | 1890 | cache | Refer to notes | B | CAUTION | 1891 | | below | | | 1892 | bearerSigIE | Refer to notes | B | CAUTION | 1893 | | below | | | 1894 | aalApp | Refer to notes | B | CAUTION | 1895 | | below | | | 1896 | cbrRate | Refer to notes | B | CAUTION | 1897 | | below | | | 1898 | sbc | Refer to notes | B | CAUTION | 1899 | | below | | | 1900 | clkrec | Refer to notes | B | CAUTION | 1901 | | below | | | 1902 | fec | Refer to notes | B | CAUTION | 1903 | | below | | | 1904 | prtfl | Refer to notes | B | CAUTION | 1905 | | below | | | 1906 | structure | Refer to notes | B | CAUTION | 1907 | | below | | | 1908 | cpsSDUsize | Refer to notes | B | CAUTION | 1909 | | below | | | 1910 | aal2CPS | Refer to notes | B | CAUTION | 1911 | | below | | | 1912 | aal2CPSSDUrate | Refer to notes | B | CAUTION | 1913 | | below | | | 1914 | aal2sscs3661unassured | Refer to notes | B | CAUTION | 1915 | | below | | | 1916 | aal2sscs3661assured | Refer to notes | B | CAUTION | 1917 | | below | | | 1918 | aal2sscs3662 | Refer to notes | B | CAUTION | 1919 | | below | | | 1920 | aal5sscop | Refer to notes | B | CAUTION | 1921 | | below | | | 1922 | atmmap | Refer to notes | B | CAUTION | 1923 | | below | | | 1924 | silenceSupp | Refer to notes | B | CAUTION | 1925 | | below | | | 1926 | ecan | Refer to notes | B | CAUTION | 1927 | | below | | | 1928 | gc | Refer to notes | B | CAUTION | 1929 | | below | | | 1930 | profileDesc | Refer to notes | B | CAUTION | 1931 | | below | | | 1932 | vsel | Refer to notes | B | CAUTION | 1933 | | below | | | 1934 | dsel | Refer to notes | B | CAUTION | 1935 | | below | | | 1936 | fsel | Refer to notes | B | CAUTION | 1937 | | below | | | 1938 | onewaySel | Refer to notes | B | CAUTION | 1939 | | below | | | 1940 | codecconfig | Refer to notes | B | CAUTION | 1941 | | below | | | 1942 | isup_usi | Refer to notes | B | CAUTION | 1943 | | below | | | 1944 | uiLayer1_Prot | Refer to notes | B | CAUTION | 1945 | | below | | | 1946 | chain | Refer to notes | B | CAUTION | 1947 | | below | | | 1948 | | | | | 1949 +-----------------------+--------------------+-------+--------------+ 1951 5.48 RFC3108 Attribute Analysis 1953 NOTE: RFC3108 describes conventions for using SDP for characterizing 1954 ATM bearer connections using an AAL1, AAL2 or AAL5 adaptation layers. 1955 For AAL1, AAL2 and AAL5, bearer connections can be used to transport 1956 single media streams. In addition, for AAL1 and AAL2, multiple media 1957 streams can be multiplexed into a bearer connection. For all 1958 adaptation types (AAL1, AAL2 and AAL5), bearer connections can be 1959 bundled into a single media group. In all cases addressed by 1960 RFC3108, a real-time media stream (voice, video, voiceband data, 1961 pseudo-wire, and others) or a multiplex of media streams is mapped 1962 directly into an ATM connection. RFC3108 does not address cases 1963 where ATM serves as a low-level transport pipe for IP packets which 1964 in turn can carry one or more real-time (e.g. VoIP) media sessions 1965 with a life-cycle different from that of the underlying ATM 1966 transport. 1968 5.49. 3GPP TS 26.114 1970 [R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and 1971 interaction 1972 +---------------------+--------------------------+-------+----------+ 1973 | Name | Notes | Level | Mux | 1974 | | | | Category | 1975 +---------------------+--------------------------+-------+----------+ 1976 | 3gpp_sync_info | Usage defined for the IP | M | NORMAL | 1977 | | Multimedia Subsystem | | | 1978 | | | | | 1979 | 3gpp_MaxRecvSDUSize | Usage defined for the IP | M | NORMAL | 1980 | | Multimedia Subsystem | | | 1981 | | | | | 1982 +---------------------+--------------------------+-------+----------+ 1984 5.49 3GPP TS 26.114 Attribute Analysis 1986 5.50. 3GPP TS 183.063 1988 [R3GPPTS183.063] Telecommunications and Internet converged Services 1989 and Protocols for Advanced Networking (TISPAN); 1991 +---------------------+---------------+-------+--------------+ 1992 | Name | Notes | Level | Mux Category | 1993 +---------------------+---------------+-------+--------------+ 1994 | PSCid | Not Impacted | S | NORMAL | 1995 | | | | | 1996 | bc_service | Not Impacted | S | NORMAL | 1997 | | | | | 1998 | bc_program | Not Impacted | S | NORMAL | 1999 | | | | | 2000 | bc_service_package | Not Impacted | S | NORMAL | 2001 | | | | | 2002 +---------------------+---------------+-------+--------------+ 2004 5.50 3GPP TS 183.063 Attribute Analysis 2006 5.51. 3GPP TS 24.182 2008 [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting 2009 tones 2010 +------------+----------------------------------+-------+-----------+ 2011 | Name | Notes | Level | Mux | 2012 | | | | Category | 2013 +------------+----------------------------------+-------+-----------+ 2014 | g.3gpp.cat | Usage defined for the IP | M | NORMAL | 2015 | | Multimedia Subsystem | | | 2016 | | | | | 2017 +------------+----------------------------------+-------+-----------+ 2019 5.51 3GPP TS 24.182 Attribute Analysis 2021 5.52. 3GPP TS 24.183 2023 [R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing 2024 Signal 2026 +------------+----------------------------------+-------+-----------+ 2027 | Name | Notes | Level | Mux | 2028 | | | | Category | 2029 +------------+----------------------------------+-------+-----------+ 2030 | g.3gpp.crs | Usage defined for the IP | M | NORMAL | 2031 | | Multimedia Subsystem | | | 2032 | | | | | 2033 +------------+----------------------------------+-------+-----------+ 2035 5.52 3GPP TS 24.183 Attribute Analysis 2037 5.53. 3GPP TS 24.229 2039 [R3GPPTS24.229] specifies IP multimedia call control protocol based 2040 on Session Initial protocol and Session Description Protocol. 2042 +-----------------+-----------------------------+-------+-----------+ 2043 | Name | Notes | Level | Mux | 2044 | | | | Category | 2045 +-----------------+-----------------------------+-------+-----------+ 2046 | secondary- | secondary-realm MUST be | M | TRANSPORT | 2047 | realm | the one that corresponds to | | | 2048 | | the "m=" line chosen for | | | 2049 | | setting up the underlying | | | 2050 | | transport flow | | | 2051 | | | | | 2052 | visited-realm | visited-realm MUST be the | M | TRANSPORT | 2053 | | one that corresponds to the | | | 2054 | | "m=" line chosen for | | | 2055 | | setting up the underlying | | | 2056 | | transport flow | | | 2057 | | | | | 2058 | omr-m-cksum | Not Impacted | M | NORMAL | 2059 | | | | | 2060 | omr-s-cksum | Not Impacted | M | NORMAL | 2061 | | | | | 2062 | omr-m-att | Not Impacted | M | NORMAL | 2063 | | | | | 2064 | omr-s-att | Not Impacted | M | NORMAL | 2065 | | | | | 2066 | omr-m-bw | Not Impacted | M | NORMAL | 2067 | | | | | 2068 | omr-s-bw | Not Impacted | M | NORMAL | 2069 | | | | | 2070 | omr-codecs | Not Impacted | M | NORMAL | 2071 | | | | | 2072 +-----------------+-----------------------------+-------+-----------+ 2074 5.53 3GPP TS 24.229 Attribute Analysis 2076 5.54. ITU T.38 2078 [T.38] defines procedures for real-time Group 3 facsimile 2079 communications over IP networks. 2081 +-----------------------+--------------------+-------+--------------+ 2082 | Name | Notes | Level | Mux Category | 2083 +-----------------------+--------------------+-------+--------------+ 2084 | T38FaxVersion | Refer to notes | M | TBD | 2085 | | below | | | 2086 | | | | | 2087 | T38MaxBitRate | Refer to notes | M | TBD | 2088 | | below | | | 2089 | | | | | 2090 | T38FaxFillBitRemoval | Refer to notes | M | TBD | 2091 | | below | | | 2092 | | | | | 2093 | T38FaxTranscodingMMR | Refer to notes | M | TBD | 2094 | | below | | | 2095 | | | | | 2096 | T38FaxTranscodingJBIG | Refer to notes | M | TBD | 2097 | | below | | | 2098 | | | | | 2099 | T38FaxRateManagement | Refer to notes | M | TBD | 2100 | | below | | | 2101 | | | | | 2102 | T38FaxMaxBuffer | Refer to notes | M | TBD | 2103 | | below | | | 2104 | | | | | 2105 | T38FaxMaxDatagram | Refer to notes | M | TBD | 2106 | | below | | | 2107 | | | | | 2108 | T38FaxUdpEC | Refer to notes | M | TBD | 2109 | | below | | | 2110 | | | | | 2111 | T38FaxMaxIFP | Refer to notes | M | TBD | 2112 | | below | | | 2113 | | | | | 2114 | T38FaxUdpECDepth | Refer to notes | M | TBD | 2115 | | below | | | 2116 | | | | | 2117 | T38FaxUdpFECMaxSpan | Refer to notes | M | TBD | 2118 | | below | | | 2119 | | | | | 2120 | T38ModemType | Refer to notes | M | TBD | 2121 | | below | | | 2122 | | | | | 2123 | T38VendorInfo | Refer to notes | M | TBD | 2124 | | below | | | 2125 | | | | | 2126 +-----------------------+--------------------+-------+--------------+ 2128 5.54 ITU T.38 Attribute Analysis 2130 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 2131 there exists no publicly available specification that defines 2132 procedures for multiplexing/demultiplexing fax protocols flows over a 2133 single 5-tuple. Once such a specification is available, the 2134 multiplexing category assignments for the attributes in this section 2135 could be revisited. 2137 5.55. ITU-T Q.1970 2139 [Q.1970] defines Bearer Independent Call Control (BICC) IP bearer 2140 control protocol. 2142 +-------+----------------------------------------+-------+----------+ 2143 | Name | Notes | Level | Mux | 2144 | | | | Category | 2145 +-------+----------------------------------------+-------+----------+ 2146 | ipbcp | ipbcp version identifies type of IP | S | SPECIAL | 2147 | | bearer control protocol (IPBCP) | | | 2148 | | message used in BICC (ITU-T Q.1901) | | | 2149 | | environment which are limited to | | | 2150 | | single media payload. Refer to the | | | 2151 | | pertinent ITU-T specifications while | | | 2152 | | multiplexing | | | 2153 | | | | | 2154 +-------+----------------------------------------+-------+----------+ 2156 5.55 ITU-T Q.1970 Attribute Analysis 2158 5.56. ITU-T H.248.15 2160 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248 2161 package attribute 2162 +----------+-------------------------------------+-------+----------+ 2163 | Name | Notes | Level | Mux | 2164 | | | | Category | 2165 +----------+-------------------------------------+-------+----------+ 2166 | h248item | It is only applicable for signaling | B | SPECIAL | 2167 | | the inclusion of H.248 extension | | | 2168 | | packages to a gateway via the local | | | 2169 | | and remote descriptors. The | | | 2170 | | attribute itself is unaffected by | | | 2171 | | multiplexing, but the packaged | | | 2172 | | referenced in a specific use of the | | | 2173 | | attribute can be impacted. Further | | | 2174 | | analysis of each package is needed | | | 2175 | | to determine if there is an issue. | | | 2176 | | This is only a concern in | | | 2177 | | environments using a decomposed | | | 2178 | | server/gateway with H.248 signaled | | | 2179 | | between them. The ITU-T will need | | | 2180 | | to do further analysis of various | | | 2181 | | packages when they specify how to | | | 2182 | | signal the use of multiplexing to a | | | 2183 | | gateway | | | 2184 | | | | | 2185 +----------+-------------------------------------+-------+----------+ 2187 5.56 ITU-T H.248.15 Attribute Analysis 2189 5.57. RFC4975: The Message Session Relay Protocol 2191 [RFC4975] the Message Session Relay Protocol, a protocol for 2192 transmitting a series of related instant messages in the context of a 2193 session. Message sessions are treated like any other media stream 2194 when set up via a rendezvous or session creation protocol such as the 2195 Session Initiation Protocol. 2197 +----------------------+---------------------+-------+--------------+ 2198 | Name | Notes | Level | Mux Category | 2199 +----------------------+---------------------+-------+--------------+ 2200 | accept-types | Refer to notes | M | TBD | 2201 | | below | | | 2202 | | | | | 2203 | accept-wrapped- | Refer to notes | M | TBD | 2204 | types | below | | | 2205 | | | | | 2206 | max-size | Refer to notes | M | TBD | 2207 | | below | | | 2208 | | | | | 2209 | path | Refer to notes | M | TBD | 2210 | | below | | | 2211 | | | | | 2212 +----------------------+---------------------+-------+--------------+ 2214 5.57 RFC4975 Attribute Analysis 2216 NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 2217 there exists no publicly available specification that defines 2218 procedures for multiplexing/demultiplexing MRSP flows over a single 2219 5-tuple. Once such a specification is available, the multiplexing 2220 categories assignments for the attributes in this section could be 2221 revisited. 2223 5.58. Historical Attributes 2225 This section specifies analysis for the attributes that are included 2226 for historic usage alone by the [IANA]. 2228 +----------+----------------------+-------+--------------+ 2229 | Name | Notes | Level | Mux Category | 2230 +----------+----------------------+-------+--------------+ 2231 | rtpred1 | Historic attributes | M | CAUTION | 2232 | | | | | 2233 | rtpred2 | Historic attributes | M | CAUTION | 2234 | | | | | 2235 +----------+----------------------+-------+--------------+ 2237 5.58 Historical Attribute Analysis 2239 6. bwtype Attribute Analysis 2241 This section specifies handling of specific bandwidth attributes when 2242 used in multiplexing scenarios. 2244 6.1. RFC4566: SDP 2246 [RFC4566] defines SDP that is intended for describing multimedia 2247 sessions for the purposes of session announcement, session 2248 invitation, and other forms of multimedia session initiation. 2250 +-----------+------------------------------------+-------+----------+ 2251 | Name | Notes | Level | Mux | 2252 | | | | Category | 2253 +-----------+------------------------------------+-------+----------+ 2254 | bwtype:CT | Not Impacted | S | NORMAL | 2255 | | | | | 2256 | bwtype:AS | For the media level usage, the | B | SUM | 2257 | | aggregate of individual bandwidth | | | 2258 | | values is considered | | | 2259 | | | | | 2260 +-----------+------------------------------------+-------+----------+ 2262 6.1 RFC4566 bwtype Analysis 2264 6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth 2266 [RFC3556] defines an extension to SDP to specify two additional 2267 modifiers for the bandwidth attribute. These modifiers may be used 2268 to specify the bandwidth allowed for RTCP packets in a RTP session. 2270 +-----------+------------------------------------+-------+----------+ 2271 | Name | Notes | Level | Mux | 2272 | | | | Category | 2273 +-----------+------------------------------------+-------+----------+ 2274 | bwtype:RS | Session level usage represents | B | SUM | 2275 | | session aggregate and media level | | | 2276 | | usage indicates SUM of the | | | 2277 | | individual values while | | | 2278 | | multiplexing | | | 2279 | | | | | 2280 | bwtype:RR | Session level usage represents | B | SUM | 2281 | | session aggregate and media level | | | 2282 | | usage indicates SUM of the | | | 2283 | | individual values while | | | 2284 | | multiplexing | | | 2285 | | | | | 2286 +-----------+------------------------------------+-------+----------+ 2288 6.2 RFC3556 bwtype Analysis 2290 6.3. RFC3890: Bandwidth Modifier for SDP 2292 [RFC3890] defines SDP Transport Independent Application Specific 2293 Maximum (TIAS) bandwidth modifier that does not include transport 2294 overhead; instead an additional packet rate attribute is defined. 2295 The transport independent bit-rate value together with the maximum 2296 packet rate can then be used to calculate the real bit-rate over the 2297 transport actually used. 2299 +-------------+----------------------------------+-------+----------+ 2300 | Name | Notes | Level | Mux | 2301 | | | | Category | 2302 +-------------+----------------------------------+-------+----------+ 2303 | bwtype:TIAS | The usage of TIAS is not defined | B | SPECIAL | 2304 | | under Offer/Answer usage. | | | 2305 | | | | | 2306 | maxprate | The usage of TIAS and maxprate | B | SPECIAL | 2307 | | is not well defined under | | | 2308 | | multiplexing | | | 2309 | | | | | 2310 +-------------+----------------------------------+-------+----------+ 2312 6.3 RFC3890 bwtype Analysis 2314 NOTE: The intention of TIAS is that the media level bit-rate is 2315 multiplied with the known per-packet overhead for the selected 2316 transport and the maxprate value to determine the worst case bit-rate 2317 from the transport to more accurately capture the required usage. 2318 Summing TIAS values independently across "m=" lines and multiplying 2319 the computed sum with maxprate and the per-packet overhead would 2320 inflate the value significantly. Instead performing multiplication 2321 and adding the individual values is a more appropriate usage. 2323 7. rtcp-fb Attribute Analysis 2325 This section analyzes rtcp-fb SDP attributes. 2327 7.1. RFC4585: RTP/AVPF 2329 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 2330 enables receivers to provide, statistically, more immediate feedback 2331 to the senders and thus allows for short-term adaptation and 2332 efficient feedback-based repair mechanisms to be implemented. 2334 +---------+------------------------------+-------+------------------+ 2335 | Name | Notes | Level | Mux Category | 2336 +---------+------------------------------+-------+------------------+ 2337 | ack | The attribute value MUST be | M | IDENTICAL-PER- | 2338 | rpsi | same for a given codec | | PT | 2339 | | configuration | | | 2340 | | | | | 2341 | ack | Feedback parameters MUST be | M | SPECIAL | 2342 | app | handled in the app specific | | | 2343 | | way when multiplexed | | | 2344 | | | | | 2345 | nack | The attribute value MUST be | M | IDENTICAL-PER- | 2346 | | same for a given codec | | PT | 2347 | | configuration | | | 2348 | | | | | 2349 | nack | The attribute value MUST be | M | IDENTICAL-PER- | 2350 | pli | same for a given codec | | PT | 2351 | | configuration | | | 2352 | | | | | 2353 | nack | The attribute value MUST be | M | IDENTICAL-PER- | 2354 | sli | same for a given codec | | PT | 2355 | | configuration | | | 2356 | | | | | 2357 | nack | The attribute value MUST be | M | IDENTICAL-PER- | 2358 | rpsi | same for a given codec | | PT | 2359 | | configuration | | | 2360 | | | | | 2361 | nack | Feedback parameters MUST be | M | SPECIAL | 2362 | app | handled in the app specific | | | 2363 | | way when multiplexed | | | 2364 | | | | | 2365 | trr- | The attribute value MUST be | M | IDENTICAL-PER- | 2366 | int | same for a given codec | | PT | 2367 | | configuration | | | 2368 | | | | | 2369 +---------+------------------------------+-------+------------------+ 2371 7.1 RFC4585 Attribute Analysis 2373 7.2. RFC5104: Codec Control Messages in AVPF 2375 [RFC5104] specifies a few extensions to the messages defined in the 2376 Audio-Visual Profile with Feedback (AVPF). They are helpful 2377 primarily in conversational multimedia scenarios where centralized 2378 multipoint functionalities are in use. However, some are also usable 2379 in smaller multicast environments and point-to-point calls. 2381 +------+---------------------------------+-------+------------------+ 2382 | Name | Notes | Level | Mux Category | 2383 +------+---------------------------------+-------+------------------+ 2384 | ccm | The attribute value MUST be | M | IDENTICAL-PER- | 2385 | | same for a given codec | | PT | 2386 | | configuration | | | 2387 | | | | | 2388 +------+---------------------------------+-------+------------------+ 2390 7.2 RFC5104 Attribute Analysis 2392 7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP Sessions 2393 (RAMS) 2395 [RFC6285] describes a method using the existing RTP and RTCP 2396 machinery that reduces the acquisition delay. In this method, an 2397 auxiliary unicast RTP session carrying the Reference Information to 2398 the receiver precedes or accompanies the multicast stream. This 2399 unicast RTP flow can be transmitted at a faster than natural bitrate 2400 to further accelerate the acquisition. The motivating use case for 2401 this capability is multicast applications that carry real-time 2402 compressed audio and video. 2404 +--------+-------------------------------+-------+------------------+ 2405 | Name | Notes | Level | Mux Category | 2406 +--------+-------------------------------+-------+------------------+ 2407 | nack | The attribute value MUST be | M | IDENTICAL-PER- | 2408 | rai | same for a given codec | | PT | 2409 | | configuration | | | 2410 | | | | | 2411 +--------+-------------------------------+-------+------------------+ 2413 7.3 RFC6285 Attribute Analysis 2415 7.4. RFC6679: ECN for RTP over UDP/IP 2417 [RFC6679] specifies how Explicit Congestion Notification (ECN) can be 2418 used with the RTP running over UDP, using the RTCP as a feedback 2419 mechanism. It defines a new RTCP Extended Report (XR) block for 2420 periodic ECN feedback, a new RTCP transport feedback message for 2421 timely reporting of congestion events, and a STUN extension used in 2422 the optional initialization method using ICE. 2424 +-----------------+-----------------------------+-------+-----------+ 2425 | Name | Notes | Level | Mux | 2426 | | | | Category | 2427 +-----------------+-----------------------------+-------+-----------+ 2428 | ecn-capable- | ECN markup are enabled at | M | IDENTICAL | 2429 | rtp | the RTP session level | | | 2430 | | | | | 2431 | nack ecn | This attribute enables ECN | M | IDENTICAL | 2432 | | at the RTP session level | | | 2433 | | | | | 2434 +-----------------+-----------------------------+-------+-----------+ 2436 7.4 RFC6679 Attribute Analysis 2438 7.5. RFC6642: Third-Party Loss Report 2440 In a large RTP session using the RTCP feedback mechanism defined in 2441 [RFC4585], a feedback target may experience transient overload if 2442 some event causes a large number of receivers to send feedback at 2443 once. This overload is usually avoided by ensuring that feedback 2444 reports are forwarded to all receivers, allowing them to avoid 2445 sending duplicate feedback reports. However, there are cases where 2446 it is not recommended to forward feedback reports, and this may allow 2447 feedback implosion. [RFC6642] memo discusses these cases and defines 2448 a new RTCP Third-Party Loss Report that can be used to inform 2449 receivers that the feedback target is aware of some loss event, 2450 allowing them to suppress feedback. Associated SDP signaling is also 2451 defined. 2453 +---------+------------------------------+-------+------------------+ 2454 | Name | Notes | Level | Mux Category | 2455 +---------+------------------------------+-------+------------------+ 2456 | nack | The attribute value MUST be | M | IDENTICAL-PER- | 2457 | tllei | same for a given codec | | PT | 2458 | | configuration | | | 2459 | | | | | 2460 | nack | The attribute value MUST be | M | IDENTICAL-PER- | 2461 | pslei | same for a given codec | | PT | 2462 | | configuration | | | 2463 | | | | | 2464 +---------+------------------------------+-------+------------------+ 2466 7.5 RFC6642 Attribute Analysis 2468 7.6. RFC5104: Codec Control Messages in AVPF 2470 [RFC5104] specifies a few extensions to the messages defined in the 2471 Audio-Visual Profile with Feedback (AVPF). They are helpful 2472 primarily in conversational multimedia scenarios where centralized 2473 multipoint functionalities are in use. However, some are also usable 2474 in smaller multicast environments and point-to-point calls. 2476 +--------+-------------------------------+-------+------------------+ 2477 | Name | Notes | Level | Mux Category | 2478 +--------+-------------------------------+-------+------------------+ 2479 | ccm | The attribute value MUST be | M | IDENTICAL-PER- | 2480 | fir | same for a given codec | | PT | 2481 | | configuration | | | 2482 | | | | | 2483 | ccm | The attribute value MUST be | M | IDENTICAL-PER- | 2484 | tmmbr | same for a given codec | | PT | 2485 | | configuration | | | 2486 | | | | | 2487 | ccm | The attribute value MUST be | M | IDENTICAL-PER- | 2488 | tstr | same for a given codec | | PT | 2489 | | configuration | | | 2490 | | | | | 2491 | ccm | The attribute value MUST be | M | IDENTICAL-PER- | 2492 | vbcm | same for a given codec | | PT | 2493 | | configuration | | | 2494 | | | | | 2495 +--------+-------------------------------+-------+------------------+ 2497 7.6 RFC5104 Attribute Analysis 2499 8. group Attribute Analysis 2501 This section analyzes SDP "group" attribute semantics [RFC5888]. 2503 8.1. RFC5888: SDP Grouping Framework 2505 [RFC5888] defines a framework to group "m" lines in SDP for different 2506 purposes. 2508 +------------+---------------+-------+--------------+ 2509 | Name | Notes | Level | Mux Category | 2510 +------------+---------------+-------+--------------+ 2511 | group:LS | Not Impacted | S | NORMAL | 2512 | | | | | 2513 | group:FID | Not Impacted | S | NORMAL | 2514 | | | | | 2515 +------------+---------------+-------+--------------+ 2517 8.1 RFC5888 Attribute Analysis 2519 8.2. RFC3524: Mapping Media Streams to Resource Reservation Flows 2521 [RFC3524] defines an extension to the SDP grouping framework. It 2522 allows requesting a group of media streams to be mapped into a single 2523 resource reservation flow. The SDP syntax needed is defined, as well 2524 as a new "semantics" attribute called Single Reservation Flow (SRF). 2526 +------------+---------------+-------+--------------+ 2527 | Name | Notes | Level | Mux Category | 2528 +------------+---------------+-------+--------------+ 2529 | group:SRF | Not Impacted | S | NORMAL | 2530 | | | | | 2531 +------------+---------------+-------+--------------+ 2533 8.2 RFC3524 Attribute Analysis 2535 8.3. RFC4091: ANAT Semantics 2537 [RFC4091] defines ANAT semantics for the SDP grouping framework. The 2538 ANAT semantics allow alternative types of network addresses to 2539 establish a particular media stream. 2541 +-------------+------------------------------+-------+--------------+ 2542 | Name | Notes | Level | Mux Category | 2543 +-------------+------------------------------+-------+--------------+ 2544 | group:ANAT | ANAT semantics is obsoleted | S | CAUTION | 2545 | | | | | 2546 +-------------+------------------------------+-------+--------------+ 2548 8.3 RFC4091 Attribute Analysis 2550 8.4. RFC5956: FEC Grouping Semantics in SDP 2552 [RFC5956] defines the semantics for grouping the associated source 2553 and FEC-based (Forward Error Correction) repair flows in SDP. The 2554 semantics defined in the document are to be used with the SDP 2555 Grouping Framework [RFC5888]. These semantics allow the description 2556 of grouping relationships between the source and repair flows when 2557 one or more source and/or repair flows are associated in the same 2558 group, and they provide support for additive repair flows. SSRC- 2559 level (Synchronization Source) grouping semantics are also defined in 2560 this document for RTP streams using SSRC multiplexing. 2562 +---------------+---------------+-------+--------------+ 2563 | Name | Notes | Level | Mux Category | 2564 +---------------+---------------+-------+--------------+ 2565 | group:FEC-FR | Not Impacted | S | NORMAL | 2566 | | | | | 2567 +---------------+---------------+-------+--------------+ 2569 8.4 RFC5956 Attribute Analysis 2571 8.5. RFC5583: Signaling Media Decoding Dependency in SDP 2573 [RFC5583] defines semantics that allow for signaling the decoding 2574 dependency of different media descriptions with the same media type 2575 in SDP. This is required, for example, if media data is separated 2576 and transported in different network streams as a result of the use 2577 of a layered or multiple descriptive media coding process. 2579 +-----------+----------------------------+-------+------------------+ 2580 | Name | Notes | Level | Mux Category | 2581 +-----------+----------------------------+-------+------------------+ 2582 | group:DDP | Not Impacted | S | NORMAL | 2583 | | | | | 2584 | depend | The attribute value MUST | M | IDENTICAL-PER- | 2585 | lay | be same for a given codec | | PT | 2586 | | configuration | | | 2587 | | | | | 2588 | depend | The attribute value MUST | M | IDENTICAL-PER- | 2589 | mdc | be same for a given codec | | PT | 2590 | | configuration | | | 2591 | | | | | 2592 +-----------+----------------------------+-------+------------------+ 2594 8.5 RFC5583 Attribute Analysis 2596 8.6. RFC7104: Duplication Grouping Semantics in the SDP 2598 [RFC7104] defines the semantics for grouping redundant streams in 2599 SDP, The semantics defined in this document are to be used with the 2600 SDP Grouping Framework. Grouping semantics at the SSRC)level are 2601 also defined in this document for RTP streams using SSRC 2602 multiplexing. 2604 +------------+---------------+-------+--------------+ 2605 | Name | Notes | Level | Mux Category | 2606 +------------+---------------+-------+--------------+ 2607 | group:DUP | Not Impacted | S | NORMAL | 2608 | | | | | 2609 +------------+---------------+-------+--------------+ 2611 8.6 RFC7104 Attribute Analysis 2613 9. ssrc-group Attribute Analysis 2615 This section analyzes "ssrc-group" semantics. 2617 9.1. RFC5576: Source-Specific SDP Attributes 2619 [RFC5576] defines a mechanism to describe RTP media sources, which 2620 are identified by their synchronization source (SSRC) identifiers, in 2621 SDP, to associate attributes with these sources, and to express 2622 relationships among sources. It also defines several source-level 2623 attributes that can be used to describe properties of media sources. 2625 +--------------------+---------------+-------+--------------+ 2626 | Name | Notes | Level | Mux Category | 2627 +--------------------+---------------+-------+--------------+ 2628 | ssrc-group:FID | Not Impacted | SR | NORMAL | 2629 | | | | | 2630 | ssrc-group:FEC | Not Impacted | SR | NORMAL | 2631 | | | | | 2632 | ssrc-group:FEC-FR | Not Impacted | SR | NORMAL | 2633 | | | | | 2634 +--------------------+---------------+-------+--------------+ 2636 9.1 RFC5576 Attribute Analysis 2638 9.2. RFC7104: Duplication Grouping Semantics in the SDP 2640 [RFC7104] defines the semantics for grouping redundant streams in 2641 SDP. The semantics defined in this document are to be used with the 2642 SDP Grouping Framework. Grouping semantics at the Synchronization 2643 Source (SSRC) level are also defined in this document for RTP streams 2644 using SSRC multiplexing. 2646 +-----------------+---------------+-------+--------------+ 2647 | Name | Notes | Level | Mux Category | 2648 +-----------------+---------------+-------+--------------+ 2649 | ssrc-group:DUP | Not Impacted | SR | NORMAL | 2650 | | | | | 2651 +-----------------+---------------+-------+--------------+ 2653 9.2 RFC7104 Attribute Analysis 2655 10. QoS Mechanism Token Analysis 2657 This section analyzes QoS tokes specified with SDP. 2659 10.1. RFC5432: QoS Mechanism Selection in SDP 2661 [RFC5432] defines procedures to negotiate QOS mechanisms using the 2662 SDP offer/answer model. 2664 +------+----------------------------------------+-------+-----------+ 2665 | Name | Notes | Level | Mux | 2666 | | | | Category | 2667 +------+----------------------------------------+-------+-----------+ 2668 | rsvp | rsvp attribute MUST be the one that | B | TRANSPORT | 2669 | | corresponds to the "m=" line chosen | | | 2670 | | for setting up the underlying | | | 2671 | | transport flow | | | 2672 | | | | | 2673 | nsis | rsvp attribute MUST be the one that | B | TRANSPORT | 2674 | | corresponds to the "m=" line chosen | | | 2675 | | for setting up the underlying | | | 2676 | | transport | | | 2677 | | | | | 2678 +------+----------------------------------------+-------+-----------+ 2680 10.1 RFC5432 Attribute Analysis 2682 NOTE: A single Differentiated Services Code Point (DSCP) code point 2683 per flow being multiplexed doesn't impact multiplexing since QOS 2684 mechanisms are signaled/scoped per flow. For scenarios that involve 2685 having different DSCP code points for packets being transmitted over 2686 the same 5-tuple, issues as discussed in [RFC7657] need to be taken 2687 into consideration. 2689 11. k= Attribute Analysis 2690 11.1. RFC4566: SDP 2692 [RFC4566] defines SDP that is intended for describing multimedia 2693 sessions for the purposes of session announcement, session 2694 invitation, and other forms of multimedia session initiation. 2696 +------+-----------------------------------------+-------+----------+ 2697 | Name | Notes | Level | Mux | 2698 | | | | Category | 2699 +------+-----------------------------------------+-------+----------+ 2700 | k= | It is not recommended to use this | S | CAUTION | 2701 | | attribute under multiplexing | | | 2702 | | | | | 2703 +------+-----------------------------------------+-------+----------+ 2705 11.1 RFC4566 Attribute Analysis 2707 12. content Attribute Analysis 2709 12.1. RFC4796 2711 [RFC4796] defines a new SDP media-level attribute, 'content'. The 2712 'content' attribute defines the content of the media stream to a more 2713 detailed level than the media description line. The sender of an SDP 2714 session description can attach the 'content' attribute to one or more 2715 media streams. The receiving application can then treat each media 2716 stream differently (e.g., show it on a big or small screen) based on 2717 its content. 2719 +------------------+---------------+-------+--------------+ 2720 | Name | Notes | Level | Mux Category | 2721 +------------------+---------------+-------+--------------+ 2722 | content:slides | Not Impacted | M | NORMAL | 2723 | | | | | 2724 | content:speaker | Not Impacted | M | NORMAL | 2725 | | | | | 2726 | content:main | Not Impacted | M | NORMAL | 2727 | | | | | 2728 | content:sl | Not Impacted | M | NORMAL | 2729 | | | | | 2730 | content:alt | Not Impacted | M | NORMAL | 2731 | | | | | 2732 +------------------+---------------+-------+--------------+ 2734 12.1 RFC4796 Attribute Analysis 2736 13. Payload Formats 2738 13.1. RFC5109: RTP Payload Format for Generic FEC 2740 [RFC5109] describes a payload format for generic Forward Error 2741 Correction (FEC) for media data encapsulated in RTP. It is based on 2742 the exclusive-or (parity) operation. The payload format allows end 2743 systems to apply protection using various protection lengths and 2744 levels, in addition to using various protection group sizes to adapt 2745 to different media and channel characteristics. It enables complete 2746 recovery of the protected packets or partial recovery of the critical 2747 parts of the payload depending on the packet loss situation. 2749 +--------------------+---------------------------+-------+----------+ 2750 | Name | Notes | Level | Mux | 2751 | | | | Category | 2752 +--------------------+---------------------------+-------+----------+ 2753 | audio/ulpfec | Not recommended for | M | CAUTION | 2754 | | multiplexing due to reuse | | | 2755 | | of SSRCs | | | 2756 | | | | | 2757 | video/ulpfec | Not recommended for | M | CAUTION | 2758 | | multiplexing due to reuse | | | 2759 | | of SSRCs | | | 2760 | | | | | 2761 | text/ulpfec | Not recommended for | M | CAUTION | 2762 | | multiplexing due to reuse | | | 2763 | | of SSRCs | | | 2764 | | | | | 2765 | application/ulpfec | Not recommended for | M | CAUTION | 2766 | | multiplexing due to reuse | | | 2767 | | of SSRCs | | | 2768 | | | | | 2769 +--------------------+---------------------------+-------+----------+ 2771 13.1 RFC5109 Payload Format Analysis 2773 14. Multiplexing Considerations for Encapsulating Attributes 2775 This sections deals with recommendations for defining the 2776 multiplexing characteristics of the SDP attributes that encapsulate 2777 other SDP attributes/parameters. Such attributes as of today, for 2778 example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of 2779 a generic framework for indicating and negotiating transport, media, 2780 and media format related capabilities in the SDP. 2782 The behavior of such attributes under multiplexing is in turn defined 2783 by the multiplexing behavior of the attributes they encapsulate which 2784 are made known once the Offer/Answer negotiation process is 2785 completed. 2787 14.1. RFC3407: cpar Attribute Analysis 2789 [RFC3407] capability parameter attribute (a=cpar) encapsulates b= 2790 (bandwidth) or an a= attribute. For bandwidth attribute 2791 encapsulation, the category SUM is inherited. For the case of a= 2792 attribute, the category corresponding to the SDP attribute being 2793 encapsulated is inherited. 2795 v=0 2796 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2797 s= 2798 c=IN IP4 host.atlanta.example.com 2799 t=0 0 2800 m=video 3456 RTP/AVP 100 2801 a=rtpmap:100 VP8/90000 2802 a=sqn: 0 2803 a=cdsc: 1 video RTP/AVP 100 2804 a=cpar: a=rtcp-mux 2805 m=video 3456 RTP/AVP 101 2806 a=rtpmap:101 VP8/90000 2807 a=fmtp:100 max-fr=15;max-fs=1200 2808 a=cdsc: 2 video RTP/AVP 101 2809 a=cpar: a=rtcp-mux 2811 In the above example,the category IDENTICAL is inherited for the cpar 2812 encapsulated rtcp-mux attribute. 2814 14.2. RFC5939 Analysis 2816 [RFC5939] defines a general SDP capability negotiation framework. It 2817 also specifies how to provide transport protocols and SDP attributes 2818 as capabilities and negotiate them using the framework. 2820 For this purpose, [RFC5939] defines the following 2822 o A set of capabilities for the session and its associated media 2823 stream components, supported by each side. The attribute 2824 ("a=acap") defines how to list an attribute name and its 2825 associated value (if any) as a capability. The attribute 2826 ("a=tcap") defines how to list transport protocols (e.g., "RTP/ 2827 AVP") as capabilities. 2829 o A set of potential configurations ("a=pcfg") provided by the 2830 offerer to indicate which combinations of those capabilities can 2831 be used for the session and its associated media stream 2832 components. Potential configurations are not ready for use until 2833 fully negotiated. They provide an alternative that MAY be used, 2834 subject to SDP capability negotiation procedures. In particular 2835 the answerer MAY choose one of the potential configurations for 2836 use as part of the current Offer/Answer exchange. 2838 o An actual configuration ("a=acfg") for the session and its 2839 associated media stream components. The actual configuration 2840 identifies the potential configuration that was negotiated for 2841 use. Use of an actual configuration does not require any further 2842 negotiation. 2844 o A negotiation process that takes the current actual and the set of 2845 potential configurations (combinations of capabilities) as input 2846 and provides the negotiated actual configurations as output. In 2847 [RFC5939] the negotiation process is done independently for each 2848 media description. 2850 14.2.1. Recommendation: Procedures for Potential Configuration Pairing 2852 This section provides recommendations for entities generating and 2853 processing SDP under the generic capability negotiation framework as 2854 defined in [RFC5939] under the context of media stream multiplexing. 2856 These recommendations are provided for the purposes of enabling the 2857 Offerer to make sure that the generated potential configurations 2858 between the multiplexed streams can (easily) be negotiated to be 2859 consistent between those streams. In particular, the procedures aim 2860 to simplify Answerer's procedure to choose potential configurations 2861 that are consistent across all the multiplexed media descriptions. 2863 A potential configuration selects a set of attributes and parameters 2864 that become part of the media description when negotiated. When 2865 multiplexing media descriptions with potential configurations 2866 specified, there MAY be a need for coordinating this selection 2867 between multiplexed media descriptions to ensure the right 2868 multiplexing behavior. 2870 Although it is possible to analyze the various potential 2871 configurations in multiplexed media descriptions to find combinations 2872 that satisfy such constraints, it can quickly become complicated to 2873 do so. 2875 The procedures defined in [RFC5939] state that each potential 2876 configuration in the SDP has a unique configuration number, however 2877 the scope of uniqueness is limited to each media description. To 2878 make it simple for the answerer to chose valid combinations of 2879 potential configurations across media descriptions in a given bundle 2880 group, we provide a simple rule for constructing potential 2881 configurations 2883 o Let m-bundle be the set of media descriptions that form a given 2884 bundle . 2886 o Let m-bundle-pcfg be the set of media descriptions in m-bundle 2887 that include one or more potential configurations. 2889 o Each media description in m-bundle-pcfg MUST have at least one 2890 potential configuration with the same configuration number (e.g. 2891 "1"). 2893 o For each potential configuration with configuration number x in m- 2894 bundle-pcfg, the offerer MUST ensure that if the answerer chooses 2895 configuration number x in each of the media descriptions in m- 2896 bundle-pcfg, then the resulting SDP will have all multiplexing 2897 constraints satisfied for those media descriptions. 2899 o Since it is nearly impossible to define a generic mechanism for 2900 various capability extensions, this document does't provide 2901 procedures for dealing with the capability extension attributes. 2902 However, Section 14.3 provide analysis of media capability 2903 extension attributes as defined in [RFC6871]. 2905 The above allows the answerer to easily find multiplexing compatible 2906 combinations of potential configurations: The answerer simply choses 2907 a potential configuration (number) that is present in all of the 2908 media descriptions with potential configurations in the bundle. 2910 Note that it is still possible for the offerer to provide additional 2911 potential configurations with independent configuration numbers. The 2912 answerer will have to perform more complicated analysis to determine 2913 valid multiplexed combinations of those. 2915 14.2.1.1. Example: Transport Capability Multiplexing 2916 v=0 2917 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2918 s= 2919 c=IN IP4 host.atlanta.example.com 2920 t=0 0 2921 a=tcap:1 RTP/SAVPF 2922 a=tcap:2 RTP/SAVP 2923 a=group:BUNDLE audio video 2924 m=audio 2925 a=mid:audio 2926 a=pcfg:1 t=1 2927 a=pcfg:2 2928 m=video 2929 a=mid:video 2930 a=pcfg:1 t=1 2931 a=pcfg:2 t=2 2933 In the example above, the potential configurations that offer 2934 transport protocol capability of RTP/SAVPF has the same configuration 2935 number "1" in both the audio and video media descriptions. 2937 14.2.1.2. Example: Attribute Capability Multiplexing 2939 v=0 2940 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2941 s= 2942 c=IN IP4 host.atlanta.example.com 2943 t=0 0 2944 a=acap:1 a=rtcp-mux 2945 a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80 2946 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 2947 a=group:BUNDLE audio video 2948 m=audio 49172 RTP/AVP 99 2949 a=mid:audio 2950 a=pcfg:1 a=1 2951 a=pcfg:2 2952 m=video 560024 RTP/AVP 100 2953 a=mid:video 2954 a=pcfg:1 a=1 2955 a=pcfg:2 a=2 2957 In the example above, the potential configuration number "1" is 2958 repeated while referring to attribute capability a=rtcp-mux, since 2959 the behavior is IDENTICAL for the attribute a=rtcp-mux under 2960 multiplexing. 2962 14.3. RFC6871 Analysis 2964 [RFC6871] extends the capability negotiation framework described in 2965 [RFC5939] by defining media capabilities that can be used to indicate 2966 and negotiate media types and their associated format parameters. It 2967 also allows indication of latent configurations and session 2968 capabilities. 2970 14.3.1. Recommendation: Dealing with Payload Type Numbers 2972 [RFC6871] defines a new payload type ("pt") parameter to be used with 2973 the potential, actual, and latent configuration parameters. The 2974 parameter associates RTP payload type numbers with the referenced 2975 RTP-based media format capabilities ("a=rmcap") defined in [RFC6871] 2976 and is appropriate only when the transport protocol uses RTP. This 2977 means that the same payload type number can be assigned as part of 2978 potential or actual configurations in different media descriptions in 2979 a bundle. There are rules for the usage of identical Payload Type 2980 values across multiplexed "m=" lines as described in 2981 [I-D.ietf-mmusic-sdp-bundle-negotiation], which must be followed here 2982 as well. As described in Section 14.2.1, the use of identical 2983 configuration numbers for compatible configurations in different 2984 media descriptions that are part of the bundle provides a way to 2985 ensure that the answerer can easily pick compatible configurations 2986 here as well. 2988 14.3.1.1. Example: Attribute Capability Under Shared Payload Type 2990 The attributes (a=rmcap, a=mfcap) follow the above recommendations 2991 under multiplexing. 2993 v=0 2994 o=- 25678 753849 IN IP4 192.0.2.1 2995 s= 2996 c=IN IP4 192.0.2.1 2997 t=0 0 2998 a=creq:med-v0 2999 m=audio 54322 RTP/AVP 96 3000 a=rtpmap:96 AMR-WB/16000/1 3001 a=fmtp:96 mode-change-capability=1; max-red=220; 3002 mode-set=0,2,4,7 3003 a=rmcap:1,3 audio AMR-WB/16000/1 3004 a=rmcap:2 audio AMR/8000/1 3005 a=mfcap:1,2 mode-change-capability=1 3006 a=mfcap:3 mode-change-capability=2 3007 a=pcfg:1 m=1 pt=1:96 3008 a=pcfg:2 m=2 pt=2:97 3009 a=pcfg:3 m=3 pt=3:98 3010 m=audio 54322 RTP/AVP 96 3011 a=rtpmap:96 AMR-WB/16000/1 3012 a=fmtp:96 mode-change-capability=1; max-red=220; 3013 mode-set=0,2,4,7 3014 a=rmcap:4 audio AMR/8000/1 3015 a=rmcap:5 audio OPUS/48000/2 3016 a=mfcap:5 minptime=40 3017 a=mfcap:4 mode-change-capability=1 3018 a=pcfg:1 m=4 pt=4:97 3019 a=pcfg:4 m=5 pt=5:101 3021 In the example above, the potential configuration number "1" is 3022 repeated when referring to media and media format capability used for 3023 the Payload Type 96. This implies that both the media capability 2 3024 and 4 along with their media format capabilities MUST refer to the 3025 same codec configuration, as per the definition of IDENTICAL-PER-PT. 3027 14.3.2. Recommendation: Dealing with Latent Configurations 3029 [RFC6871] adds the notion of a latent configurations, which provides 3030 configuration information that may be used to guide a subsequent 3031 offer/exchange, e.g. by adding another media stream or use 3032 alternative codec combinations not currently offered. Latent 3033 configurations have configuration numbers which cannot overlap with 3034 the potential configuration numbers [RFC6871]. Supported 3035 combinations of potential and latent configurations are indicated by 3036 use of the "a=sescap" attribute, however use of this attribute is not 3037 recommended with multiplexed media, since it requires the use of 3038 unique configuration numbers across the SDP. Taken together, this 3039 means there is no well-defined way to indicate supported combinations 3040 of latent configurations, or combinations of latent and potential 3041 configurations with multiplexed media. It is still allowed to use 3042 the latent configuration attribute, however the limitations above 3043 will apply. To determine valid combinations, actual negotiation will 3044 have to be attempted subsequently instead. 3046 15. IANA Considerations 3048 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 3049 document.] 3051 Section 15.1 defines a new subregistry to be added by the IANA for 3052 identifying the initial registrations for various multiplexing 3053 categories applicable, as proposed in this document. 3055 IANA is also requested to add a new column named "Mux Category" to 3056 several of the subregistries in the "Session Description Protocol 3057 (SDP) Parameters" registry. The tables in Section 15.2 identify name 3058 of an entry in the existing subregistry and specify the value to be 3059 put in the new "Mux Category" column of the associated IANA registry. 3061 15.1. New 'Multiplexing Categories' subregistry 3063 A new sub-registry needs to be defined called the "Multiplexing 3064 Categories", with the following registrations created initially: 3065 "NORMAL", "CAUTION", "IDENTICAL", "TRANSPORT", "SUM", "INHERIT", 3066 "IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this document. 3068 Initial value registration for "Multiplexing Categories". 3070 +-------------------------+-----------+ 3071 | Multiplexing Categories | Reference | 3072 +-------------------------+-----------+ 3073 | NORMAL | RFCXXXX | 3074 | CAUTION | RFCXXXX | 3075 | IDENTICAL | RFCXXXX | 3076 | TRANSPORT | RFCXXXX | 3077 | SUM | RFCXXXX | 3078 | INHERIT | RFCXXXX | 3079 | IDENTICAL-PER-PT | RFCXXXX | 3080 | SPECIAL | RFCXXXX | 3081 | TBD | RFCXXXX | 3082 +-------------------------+-----------+ 3084 Further entries can be registered using Standard Actions policies 3085 outlined in [RFC5226], which requires IESG review and approval and 3086 standards-track IETF RFC publication. 3088 Each registration needs to indicate the multiplexing category value 3089 to be added to the "Multiplexing Categories" subregistry as defined 3090 in this section. 3092 Such a registration MUST also indicate the applicability of the newly 3093 defined multiplexing category value to various subregistries defined 3094 at the "Session Description Protocol (SDP) Parameters" registry. 3096 15.2. 'Mux Category' column for subregistries 3098 Each sub-section identifies a subregistry in the "Session Description 3099 Protocol (SDP) Parameters" registry. The tables list the column that 3100 identifies the SDP attribute name/Token/Value from the corresponding 3101 subregistries and the values to be used for the new "Mux Category" 3102 column to be added. 3104 For the entries in the existing subregistries, under the "Session 3105 Description Protocol (SDP) Parameters" registry, that lack a value 3106 for the "Mux Category" in this specification will get a value of 3107 "TBD". 3109 The registration policy for updates to the 'Mux Category' column 3110 values for existing parameters, or when registering new parameters, 3111 are beyond the scope of this document. The registration policy for 3112 the affected table is defined in [I-D.ietf-mmusic-rfc4566bis]. 3114 15.2.1. Table: SDP bwtype 3116 The following values are to be added to the 'SDP bwtype' subregistry 3117 in the "Session Description Protocol (SDP) Parameters" registry. The 3118 references should be updated to point at this RFC as well as the 3119 previous references. 3121 +----------+--------------+ 3122 | SDP Name | Mux Category | 3123 +----------+--------------+ 3124 | CT | NORMAL | 3125 | AS | SUM | 3126 | RS | SUM | 3127 | RR | SUM | 3128 | TIAS | SPECIAL | 3129 +----------+--------------+ 3131 15.2.2. Table: att-field (session level) 3133 The following values are to be added to the "att-field (session 3134 level)" subregistry in the "Session Description Protocol (SDP) 3135 Parameters" registry. The references should be updated to point at 3136 this RFC as well as the previous references. 3138 +---------------------+--------------+ 3139 | SDP Name | Mux Category | 3140 +---------------------+--------------+ 3141 | cat | NORMAL | 3142 | keywds | NORMAL | 3143 | type | NORMAL | 3144 | type:broadcast | NORMAL | 3145 | type:H332 | NORMAL | 3146 | type:meeting | NORMAL | 3147 | type:moderated | NORMAL | 3148 | type:test | NORMAL | 3149 | charset | NORMAL | 3150 | charset:iso8895-1 | NORMAL | 3151 | tool | NORMAL | 3152 | ipbcp | SPECIAL | 3153 | group | NORMAL | 3154 | ice-lite | NORMAL | 3155 | ice-options | NORMAL | 3156 | bcastversion | NORMAL | 3157 | 3GPP-Integrity-Key | CAUTION | 3158 | 3GPP-SDP-Auth | CAUTION | 3159 | alt-group | CAUTION | 3160 | PSCid | NORMAL | 3161 | bc_service | NORMAL | 3162 | bc_program | NORMAL | 3163 | bc_service_package | NORMAL | 3164 | sescap | CAUTION | 3165 | rtsp-ice-d-m | TBD | 3166 +---------------------+--------------+ 3168 15.2.3. Table: att-field (both session and media level) 3170 The following values are to be added to the "att-field (both session 3171 and media level)" subregistry in the "Session Description Protocol 3172 (SDP) Parameters" registry. The references should be updated to 3173 point at this RFC as well as the previous references. 3175 NOTE: The attributes from draft-ietf-rmt-flute-sdp ('flute-tsi', 3176 'flute-ch', 'FEC-declaration', 'FEC-OTI-extension', 'content-desc') 3177 were not analyzed for their multiplexing behavior due to the expired 3178 status of the draft. For purposes of this specification, the 3179 multiplexing category of 'TBD' is assigned. 3181 +-------------------------+-------------------+ 3182 | SDP Name | Mux Category | 3183 +-------------------------+-------------------+ 3184 | recvonly | NORMAL | 3185 | sendrecv | NORMAL | 3186 | sendonly | NORMAL | 3187 | sdplang | NORMAL | 3188 | lang | NORMAL | 3189 | h248item | SPECIAL | 3190 | sqn | NORMAL | 3191 | cdsc | NORMAL | 3192 | cpar | INHERIT | 3193 | cparmin | SPECIAL | 3194 | cparmax | SPECIAL | 3195 | rtcp-xr | NORMAL | 3196 | maxprate | SPECIAL | 3197 | setup | TRANSPORT | 3198 | connection | TRANSPORT | 3199 | key-mgmt | IDENTICAL | 3200 | source-filter | IDENTICAL | 3201 | inactive | NORMAL | 3202 | fingerprint | TRANSPORT | 3203 | flute-tsi | TBD | 3204 | flute-ch | TBD | 3205 | FEC-declaration | TBD | 3206 | FEC-OTI-extension | TBD | 3207 | content-desc | TBD | 3208 | ice-pwd | TRANSPORT | 3209 | ice-ufrag | TRANSPORT | 3210 | stkmstream | NORMAL | 3211 | extmap | SPECIAL | 3212 | qos-mech-send | TRANSPORT | 3213 | qos-mech-recv | TRANSPORT | 3214 | csup | NORMAL | 3215 | creq | NORMAL | 3216 | acap | INHERIT | 3217 | tcap | INHERIT | 3218 | 3GPP-QoE-Metrics | CAUTION | 3219 | 3GPP-Asset-Information | CAUTION | 3220 | mbms-mode | CAUTION | 3221 | mbms-repair | CAUTION | 3222 | ike-setup | IDENTICAL | 3223 | psk-fingerprint | IDENTICAL | 3224 | multicast-rtcp | IDENTICAL | 3225 | rmcap | IDENTICAL-PER-PT | 3226 | omcap | NORMAL | 3227 | mfcap | IDENTICAL-PER-PT | 3228 | mscap | INHERIT | 3229 | 3gpp.iut.replication | TBD | 3230 | bcap | INHERIT | 3231 | ccap | IDENTICAL | 3232 | icap | NORMAL | 3233 | 3gpp_sync_info | NORMAL | 3234 | 3gpp_MaxRecvSDUSize | NORMAL | 3235 | etag | CAUTION | 3236 | duplication-delay | NORMAL | 3237 | range | CAUTION | 3238 | control | CAUTION | 3239 | mtag | CAUTION | 3240 | ts-refclk | NORMAL | 3241 | mediaclk | NORMAL | 3242 | calgextmap | NORMAL | 3243 +-------------------------+-------------------+ 3245 15.2.4. Table: att-field (media level only) 3247 The following values are to be added to the "att-field (media level 3248 only)" registry in the "Session Description Protocol (SDP) 3249 Parameters" registry. The references should be updated to point at 3250 this RFC as well as the previous references. 3252 +---------------------------+-------------------+ 3253 | SDP Name | Mux Category | 3254 +---------------------------+-------------------+ 3255 | ptime | IDENTICAL-PER-PT | 3256 | orient | NORMAL | 3257 | orient:portrait | NORMAL | 3258 | orient:landscape | NORMAL | 3259 | orient:seascape | NORMAL | 3260 | framerate | IDENTICAL-PER-PT | 3261 | quality | NORMAL | 3262 | rtpmap | IDENTICAL-PER-PT | 3263 | fmtp | IDENTICAL-PER-PT | 3264 | rtpred1 | CAUTION | 3265 | rtpred2 | CAUTION | 3266 | T38FaxVersion | TBD | 3267 | T38MaxBitRate | TBD | 3268 | T38FaxFillBitRemoval | TBD | 3269 | T38FaxTranscodingMMR | TBD | 3270 | T38FaxTranscodingJBIG | TBD | 3271 | T38FaxRateManagement | TBD | 3272 | T38FaxMaxBuffer | TBD | 3273 | T38FaxMaxDatagram | TBD | 3274 | T38FaxUdpEC | TBD | 3275 | maxptime | IDENTICAL-PER-PT | 3276 | des | CAUTION | 3277 | curr | CAUTION | 3278 | conf | CAUTION | 3279 | mid | NORMAL | 3280 | rtcp | TRANSPORT | 3281 | rtcp-fb | IDENTICAL-PER-PT | 3282 | label | NORMAL | 3283 | T38VendorInfo | TBD | 3284 | crypto | TRANSPORT | 3285 | eecid | CAUTION | 3286 | aalType | CAUTION | 3287 | capability | CAUTION | 3288 | qosClass | CAUTION | 3289 | bcob | CAUTION | 3290 | stc | CAUTION | 3291 | upcc | CAUTION | 3292 | atmQOSparms | CAUTION | 3293 | atmTrfcDesc | CAUTION | 3294 | abrParms | CAUTION | 3295 | abrSetup | CAUTION | 3296 | bearerType | CAUTION | 3297 | lij | CAUTION | 3298 | anycast | CAUTION | 3299 | cache | CAUTION | 3300 | bearerSigIE | CAUTION | 3301 | aalApp | CAUTION | 3302 | cbrRate | CAUTION | 3303 | sbc | CAUTION | 3304 | clkrec | CAUTION | 3305 | fec | CAUTION | 3306 | prtfl | CAUTION | 3307 | structure | CAUTION | 3308 | cpsSDUsize | CAUTION | 3309 | all2CPS | CAUTION | 3310 | all2CPSSDUrate | CAUTION | 3311 | aal2sscs3661unassured | CAUTION | 3312 | aal2sscs3661assured | CAUTION | 3313 | aal2sscs3662 | CAUTION | 3314 | aal5sscop | CAUTION | 3315 | atmmap | CAUTION | 3316 | silenceSupp | CAUTION | 3317 | ecan | CAUTION | 3318 | gc | CAUTION | 3319 | profileDesc | CAUTION | 3320 | vsel | CAUTION | 3321 | dsel | CAUTION | 3322 | fsel | CAUTION | 3323 | onewaySel | CAUTION | 3324 | codecconfig | CAUTION | 3325 | isup_usi | CAUTION | 3326 | uiLayer1_Prot | CAUTION | 3327 | chain | CAUTION | 3328 | floorctrl | TBD | 3329 | confid | NORMAL | 3330 | userid | NORMAL | 3331 | floorid | NORMAL | 3332 | FEC | NORMAL | 3333 | accept-types | TBD | 3334 | accept-wrapped-types | TBD | 3335 | max-size | TBD | 3336 | path | TBD | 3337 | dccp-service-code | CAUTION | 3338 | rtcp-mux | IDENTICAL | 3339 | candidate | TRANSPORT | 3340 | ice-mismatch | NORMAL | 3341 | remote-candidates | TRANSPORT | 3342 | SRTPAuthentication | TBD | 3343 | SRTPROCTxRate | TBD | 3344 | rtcp-rsize | IDENTICAL | 3345 | file-selector | TBD | 3346 | file-transfer-id | TBD | 3347 | file-disposition | TBD | 3348 | file-date | TBD | 3349 | file-icon | TBD | 3350 | file-range | TBD | 3351 | depend | IDENTICAL-PER-PT | 3352 | ssrc | NORMAL | 3353 | ssrc-group | NORMAL | 3354 | rtcp-unicast | IDENTICAL | 3355 | pcfg | SPECIAL | 3356 | acfg | SPECIAL | 3357 | zrtp-hash | TRANSPORT | 3358 | X-predecbufsize | CAUTION | 3359 | X-initpredecbufperiod | CAUTION | 3360 | X-initpostdecbufperiod | CAUTION | 3361 | X-decbyterate | CAUTION | 3362 | 3gpp-videopostdecbufsize | CAUTION | 3363 | framesize | CAUTION | 3364 | 3GPP-SRTP-Config | CAUTION | 3365 | alt | CAUTION | 3366 | alt-default-id | CAUTION | 3367 | 3GPP-Adaption-Support | CAUTION | 3368 | mbms-flowid | CAUTION | 3369 | fec-source-flow | SPECIAL | 3370 | fec-repair-flow | SPECIAL | 3371 | repair-window | SPECIAL | 3372 | rams-updates | CAUTION | 3373 | imageattr | IDENTICAL-PER-PT | 3374 | cfw-id | NORMAL | 3375 | portmapping-req | CAUTION | 3376 | g.3gpp.cat | NORMAL | 3377 | g.3gpp.crs | NORMAL | 3378 | ecn-capable-rtp | IDENTICAL | 3379 | visited-realm | TRANSPORT | 3380 | secondary-realm | TRANSPORT | 3381 | omr-s-cksum | NORMAL | 3382 | omr-m-cksum | NORMAL | 3383 | omr-codecs | NORMAL | 3384 | omr-m-att | NORMAL | 3385 | omr-s-att | NORMAL | 3386 | omr-m-bw | NORMAL | 3387 | omr-s-bw | NORMAL | 3388 | msrp-cema | TBD | 3389 | dccp-port | CAUTION | 3390 | resource | NORMAL | 3391 | channel | NORMAL | 3392 | cmid | NORMAL | 3393 | content | NORMAL | 3394 | lcfg | SPECIAL | 3395 | loopback | NORMAL | 3396 | loopback-source | NORMAL | 3397 | loopback-mirror | NORMAL | 3398 | chatroom | TBD | 3399 | altc | TRANSPORT | 3400 | T38FaxMaxIFP | TBD | 3401 | T38FaxUdpECDepth | TBD | 3402 | T38FaxUdpFECMaxSpan | TBD | 3403 | T38ModemType | TBD | 3404 | cs-correlation | TBD | 3405 | rtcp-idms | NORMAL | 3406 +---------------------------+-------------------+ 3408 15.2.5. Table: att-field (source level) 3410 The following values are to be added to the "att-field (source 3411 level)" registry in the "Session Description Protocol (SDP) 3412 Parameters" registry. The references should be updated to point at 3413 this RFC as well as the previous references. 3415 +----------------+-------------------+ 3416 | SDP Name | Mux Category | 3417 +----------------+-------------------+ 3418 | cname | NORMAL | 3419 | previous-ssrc | NORMAL | 3420 | fmtp | IDENTICAL-PER-PT | 3421 | ts-refclk | NORMAL | 3422 | mediaclk | NORMAL | 3423 +----------------+-------------------+ 3425 15.2.6. Table: content SDP Parameters 3427 The following values are to be added to the "content SDP Parameters" 3428 subregistry in the "Session Description Protocol (SDP) Parameters" 3429 registry. The references should be updated to point at this RFC as 3430 well as the previous references. 3432 +----------+--------------+ 3433 | SDP Name | Mux Category | 3434 +----------+--------------+ 3435 | slides | NORMAL | 3436 | speaker | NORMAL | 3437 | sl | NORMAL | 3438 | main | NORMAL | 3439 | alt | NORMAL | 3440 +----------+--------------+ 3442 15.2.7. Table: Semantics for the 'group' SDP Attribute 3444 The following values are to be added to the "Semantics for the 3445 "group" SDP Attribute" subregistry in the "Session Description 3446 Protocol (SDP) Parameters" registry. The references should be 3447 updated to point at this RFC as well as the previous references. 3449 +---------+--------------+ 3450 | Token | Mux Category | 3451 +---------+--------------+ 3452 | LS | NORMAL | 3453 | FID | NORMAL | 3454 | SRF | NORMAL | 3455 | ANAT | CAUTION | 3456 | FEC | NORMAL | 3457 | FEC-FR | NORMAL | 3458 | CS | NORMAL | 3459 | DDP | NORMAL | 3460 | DUP | NORMAL | 3461 +---------+--------------+ 3463 15.2.8. Table: 'rtcp-fb' Attribute Values 3465 The following values are to be added to the " 'rtcp-fb' Attribute 3466 Values" subregistry in the "Session Description Protocol (SDP) 3467 Parameters" registry. The references should be updated to point at 3468 this RFC as well as the previous references. 3470 +------------+-------------------+ 3471 | Value Name | Mux Category | 3472 +------------+-------------------+ 3473 | ack | IDENTICAL-PER-PT | 3474 | app | SPECIAL | 3475 | ccm | IDENTICAL-PER-PT | 3476 | nack | IDENTICAL-PER-PT | 3477 | trr-int | IDENTICAL-PER-PT | 3478 +------------+-------------------+ 3480 15.2.9. Table: 'ack' and 'nack' Attribute Values 3482 The following values are to be added to the " 'ack' and 'nack' 3483 Attribute Values" subregistry in the "Session Description Protocol 3484 (SDP) Parameters" registry. The references should be updated to 3485 point at this RFC as well as the previous references. 3487 +------------+-------------------+ 3488 | Value Name | Mux Category | 3489 +------------+-------------------+ 3490 | sli | IDENTICAL-PER-PT | 3491 | pli | IDENTICAL-PER-PT | 3492 | rpsi | IDENTICAL-PER-PT | 3493 | app | SPECIAL | 3494 | rai | IDENTICAL-PER-PT | 3495 | tllei | IDENTICAL-PER-PT | 3496 | pslei | IDENTICAL-PER-PT | 3497 | ecn | IDENTICAL | 3498 +------------+-------------------+ 3500 15.2.10. Table: 'depend' SDP Attribute Values 3502 The following values are to be added to the " 'depend' SDP Attribute 3503 Values" subregistry in the "Session Description Protocol (SDP) 3504 Parameters" registry. The references should be updated to point at 3505 this RFC as well as the previous references. 3507 +-------+-------------------+ 3508 | Token | Mux Category | 3509 +-------+-------------------+ 3510 | lay | IDENTICAL-PER-PT | 3511 | mdc | IDENTICAL-PER-PT | 3512 +-------+-------------------+ 3514 15.2.11. Table: 'cs-correlation' Attribute Values 3516 The following values are to be added to the " "cs-correlation" 3517 Attribute Values" subregistry in the "Session Description Protocol 3518 (SDP) Parameters" registry. The references should be updated to 3519 point at this RFC as well as the previous references. 3521 +-----------+--------------+ 3522 | Value | Mux Category | 3523 +-----------+--------------+ 3524 | callerid | TBD | 3525 | uuie | TBD | 3526 | dtmf | TBD | 3527 | external | TBD | 3528 +-----------+--------------+ 3530 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 3532 The following values are to be added to the Semantics for the 3533 "Semantics for the "ssrc-group" SDP Attribute" subregistry in the 3534 "Session Description Protocol (SDP) Parameters" registry. The 3535 references should be updated to point at this RFC as well as the 3536 previous references. 3538 +---------+--------------+ 3539 | Token | Mux Category | 3540 +---------+--------------+ 3541 | FID | NORMAL | 3542 | FEC | NORMAL | 3543 | FEC-FR | NORMAL | 3544 | DUP | NORMAL | 3545 +---------+--------------+ 3547 15.2.13. Table: SDP/RTSP key management protocol identifiers 3549 The following values are to be added to the "SDP/RTSP key management 3550 protocol identifiers" subregistry in the "Session Description 3551 Protocol (SDP) Parameters" registry. The references should be 3552 updated to point at this RFC as well as the previous references. 3554 +------------+--------------+ 3555 | Value Name | Mux Category | 3556 +------------+--------------+ 3557 | mikey | IDENTICAL | 3558 +------------+--------------+ 3560 15.2.14. Table: Codec Control Messages 3562 The following values are to be added to the "Codec Control Messages" 3563 subregistry in the "Session Description Protocol (SDP) Parameters" 3564 registry. The references should be updated to point at this RFC as 3565 well as the previous references. 3567 +------------+-------------------+ 3568 | Value Name | Mux Category | 3569 +------------+-------------------+ 3570 | fir | IDENTICAL-PER-PT | 3571 | tmmbr | IDENTICAL-PER-PT | 3572 | tstr | IDENTICAL-PER-PT | 3573 | vbcm | IDENTICAL-PER-PT | 3574 +------------+-------------------+ 3576 15.2.15. Table: QoS Mechanism Tokens 3578 The following values are to be added to the "QoS Mechanism Tokens" 3579 subregistry in the "Session Description Protocol (SDP) Parameters" 3580 registry. The references should be updated to point at this RFC as 3581 well as the previous references. 3583 +---------------+--------------+ 3584 | QoS Mechanism | Mux Category | 3585 +---------------+--------------+ 3586 | rsvp | TRANSPORT | 3587 | nsis | TRANSPORT | 3588 +---------------+--------------+ 3590 15.2.16. Table: SDP Capability Negotiation Option Tags 3592 The following values are to be added to the "SDP Capability 3593 Negotiation Option Tags" subregistry in the "Session Description 3594 Protocol (SDP) Parameters" registry. The references should be 3595 updated to point at this RFC as well as the previous references. 3597 +------------+--------------+ 3598 | Option Tag | Mux Category | 3599 +------------+--------------+ 3600 | cap-v0 | NORMAL | 3601 | med-v0 | NORMAL | 3602 | bcap-v0 | NORMAL | 3603 | ccap-v0 | NORMAL | 3604 | icap-v0 | NORMAL | 3605 +------------+--------------+ 3607 15.2.17. Table: Timestamp Reference Clock Source Parameters 3609 The following values are to be added to the "Timestamp Reference 3610 Clock Source Parameters" subregistry in the "Session Description 3611 Protocol (SDP) Parameters" registry. The references should be 3612 updated to point at this RFC as well as the previous references. 3614 +----------+--------------+ 3615 | Name | Mux Category | 3616 +----------+--------------+ 3617 | ntp | NORMAL | 3618 | ptp | NORMAL | 3619 | gps | NORMAL | 3620 | gal | NORMAL | 3621 | glonass | NORMAL | 3622 | local | NORMAL | 3623 | private | NORMAL | 3624 +----------+--------------+ 3626 15.2.18. Table: Media Clock Source Parameters 3628 The following values are to be added to the "Media Clock Source 3629 Parameters" subegistry in the "Session Description Protocol (SDP) 3630 Parameters" registry. The references should be updated to point at 3631 this RFC as well as the previous references. 3633 +-----------+--------------+ 3634 | Name | Mux Category | 3635 +-----------+--------------+ 3636 | sender | NORMAL | 3637 | direct | NORMAL | 3638 | IEEE1722 | NORMAL | 3639 +-----------+--------------+ 3641 16. Security Considerations 3643 The primary security for RTP including the way it is used here is 3644 described in [RFC3550] and [RFC3711]. 3646 When multiplexing SDP attributes with the category "CAUTION", the 3647 implementations should be aware of possible issues as described in 3648 this specification. 3650 17. Acknowledgments 3652 I would like to thank Cullen Jennings, Flemming Andreasen for 3653 suggesting the categories, contributing text and reviewing the draft. 3654 I would also link to thank Magnus Westerlund, Christer Holmberg, 3655 Jonathan Lennox, Bo Burman, Ari Keranen, and Dan Wing on suggesting 3656 structural changes helping improve the document readability. 3658 I would like also to thank following experts on their inputs and 3659 reviews as listed - Flemming Andreasen(5.24,5.32,5.33,14), Rohan 3660 Mahy(5.57), Eric Burger(5.26),Christian Huitema(5.14), Christer 3661 Holmberg(5.21,5.26,5.51,5.52), Richard Ejzak (5.44,5.53,5.54), Colin 3662 Perkins(5.7,5.8,5.9,5.58), Magnus 3663 Westerlund(5.2,5.3,5.9,5.27,5.47,6.1,6.2,6.3,8.3,7), Roni 3664 Evens(5.12,5.27,8.4), Subha Dhesikan(5.6,10), Dan 3665 Wing(5.7,5.12,5.35,5.39,5.45), Cullen Jennings (5.40), Ali C 3666 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 3667 (7.2,7.6), Charles Eckel(5.15,5.27,5.28,9.1,8.5), Paul Kyzivat(5.24), 3668 Ian Johansson(5.15), Saravanan Shanmugham(5.11), Paul E Jones(5.30), 3669 Rajesh Kumar(5.48), Jonathan Lennox(5.36,5,15,9.1,11.1), Mo 3670 Zanaty(5.4,5.5,5.23,8.1,8.3,8.5,12.1), Christian Huitema (5.14), Qin 3671 Wu (5.47 PM-Dir review), Hans Stokking(5.43,5.16), Christian Groves 3672 (5.48,5.55), Thomas Stach. 3674 I would like to thank Chris Lonvick for the SECDIR review, Dan 3675 Romascanu for th Gen-ART review and Sabrina Tanamal for the IANA 3676 review. 3678 Thanks to Ben Campbell for AD review suggestions. Thanks to Spencer 3679 Dawkins, Stephen Farrel, Alissa Cooper, Mirja Kuehlewind and the 3680 entire IESG experts for their reviews. 3682 18. Change Log 3684 [RFC EDITOR NOTE: Please remove this section when publishing] 3686 Changes draft-ietf-mmusic-sdp-mux-attributes-16 3687 o Added a clarification note on when to encode IDENTICAL attributes 3688 as suggested by Christer. 3690 Changes draft-ietf-mmusic-sdp-mux-attributes-15 3692 o Updated Mux category for floorctrl to TBD 3694 Changes draft-ietf-mmusic-sdp-mux-attributes-14 3696 o Incorporated Comments from IESG review : 3698 * Updated security considerations section to fix the 3699 incositencies (Spencer's review) 3701 * Updated section 5.36 to align the text with 5.39 (Stephen's 3702 review) 3704 * Updated IANA registration section to make RFC4566bis a 3705 informative dependency (IETF 98 followup) 3707 * Updated Section 5 to expand 'B' level SDP attributes (Dan's 3708 review) 3710 Changes from draft-ietf-mmusic-sdp-mux-attributes-10 - draft-ietf- 3711 mmusic-sdp-mux-attributes-13 3713 o Incorporated Comments from WGLC review and AD Evaluation 3715 Changes from draft-ietf-mmusic-sdp-mux-attributes-10 3717 o Incorporated Comments from Bo Burman for publication request 3719 Changes from draft-ietf-mmusic-sdp-mux-attributes-08 to draft-ietf- 3720 mmusic-sdp-mux-attributes-10 3722 o Minor nits and version update to advert expiration 3724 Changes from draft-ietf-mmusic-sdp-mux-attributes-06 to draft-ietf- 3725 mmusic-sdp-mux-attributes-08 3727 o Assigned TBD category to all the attributes for whom there exists 3728 no specification on multiplexing behavior over the underlying 3729 transport protocol today. 3731 o Incorporated comments from Flemming and Ari (post last call) 3733 Changes from draft-ietf-mmusic-sdp-mux-attributes-06 3734 o Incorporated last call review comments from Thomas Stach and Ari 3735 Keranen. 3737 o Fixed more nits to prep for the LastCall. 3739 Changes from draft-ietf-mmusic-sdp-mux-attributes-05 3741 o Incorporated review comments from Christian Grooves and Ari 3742 Keranen. 3744 o Fixed more nits to prep for the LastCall. 3746 Changes from draft-ietf-mmusic-sdp-mux-attributes-04 3748 o Fixed minor nits overall. 3750 o Updated Acknowledgement Sections 3752 o Last Call Version. 3754 Changes from draft-ietf-mmusic-sdp-mux-attributes-03 3756 o More re-work on the IANA section. 3758 o Clean ups preparing for the last call. 3760 Changes from draft-ietf-mmusic-sdp-mux-attributes-02 3762 o Incorporated suggestions from Flemming on Capability Negotiation. 3764 o Closed open issues from IETF90 3766 o Added IANA section to list the categories for all the SDP 3767 attributes anlayzed 3769 o Lots of cleanup 3771 o Reformatted Refernces section to use short-form notation 3773 Changes from draft-ietf-mmusic-sdp-mux-attributes-01 3775 o Updated section 15 to provide detailed recommendation on dealing 3776 with encapsulating attributes. Also updated sections 5.20, 5.28, 3777 5.29 to refer to Section 15. 3779 o Added new categories IDENTICAL-PER-PT and INHERIT 3781 o Updated Sections 16 to add the new categories. 3783 o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the 3784 category IDENTICAL-PER-PT. 3786 o Reformatted section 4 to add individual categories to their own 3787 sections. 3789 Changes from draft-ietf-mmusic-sdp-mux-attributes-00 3791 o Added Section 15 to provide recommendations on multiplexing SDP 3792 encapsulating attributes. Also updated sections 5.20, 5.28, 5.29 3793 to refer to Section 15. 3795 o Updated Section 5.38 to incorporate PM-dir review inputs from Qin 3796 Wu 3798 o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more 3799 clarity. 3801 o Fixed few nits regarding sentence clarity and fill-in the NOTES 3802 section where information was lacking. 3804 Changes from draft-nandakumar-mmusic-mux-attributes-05 3806 o Renamed the document to be a WG document. 3808 o Added Section 14. 3810 o Updated Open Issues based on IETF88 discussions. 3812 Changes from draft-nandakumar-mmusic-mux-attributes-04 3814 o Added few OPEN ISSUES that needs to be discussed. 3816 o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4, 3817 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1 3819 o Updated Table Column name Current to Level and improved TRANSPORT 3820 category explanation on suggestions form Dan Wing. 3822 o Grouped all the rtcp-fb attribute analysis under a single section 3823 as suggested by Magnus/ 3825 Changes from draft-nandakumar-mmusic-mux-attributes-03 3827 o Maintenance change to clean up grammatical nits and wordings. 3829 Changes from draft-nandakumar-mmusic-mux-attributes-02 3830 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34, 3831 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 3832 the inputs from the respective RFC Authors. 3834 Changes from draft-nandakumar-mmusic-mux-attributes-01 3836 o Replaced Category BAD with NOT-RECOMMENDED. 3838 o Added Category TBD. 3840 o Updated IANA Consideration Section. 3842 Changes from draft-nandakumar-mmusic-mux-attributes-00 3844 o Added new section for dealing with FEC payload types. 3846 19. References 3848 19.1. Normative References 3850 [I-D.ietf-mmusic-sdp-bundle-negotiation] 3851 Holmberg, C., Alvestrand, H., and C. Jennings, 3852 "Negotiating Media Multiplexing Using the Session 3853 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- 3854 negotiation-48 (work in progress), January 2018. 3856 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3857 Requirement Levels", BCP 14, RFC 2119, March 1997. 3859 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 3860 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 3861 July 2006, . 3863 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 3864 IANA Considerations Section in RFCs", RFC 5226, 3865 DOI 10.17487/RFC5226, May 2008, . 3868 19.2. Informative References 3870 [H.248.15] 3871 "Gateway control protocol: SDP H.248 package attribute", 3872 . 3874 [I-D.ietf-mmusic-rfc4566bis] 3875 Begen, A., Kyzivat, P., Perkins, C., and M. Handley, "SDP: 3876 Session Description Protocol", draft-ietf-mmusic- 3877 rfc4566bis-25 (work in progress), February 2018. 3879 [IANA] "Session Description Protocol (SDP) Parameters", 3880 . 3883 [Q.1970] "Q.1970 : BICC IP bearer control protocol", 3884 . 3886 [R3GPPTS183.063] 3887 "TISPAN - IMS based ITPV Stage 3 specification.", 3888 . 3892 [R3GPPTS24.182] 3893 "IP Multimedia Subsystem (IMS) Customized Alerting Tones 3894 (CAT); Protocol specification", 3895 . 3897 [R3GPPTS24.183] 3898 "IP Multimedia Subsystem (IMS) Customized Ringing Signal 3899 (CRS); Protocol specification", 3900 . 3902 [R3GPPTS24.229] 3903 "IP multimedia call control protocol based on Session 3904 Initiation Protocol (SIP) and Session Description Protocol 3905 (SDP);", 3906 . 3908 [R3GPPTS26.114] 3909 "IP multimedia Subsystem : Media Handling and 3910 interaction", . 3912 [RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time 3913 Streaming Protocol (RTSP)", RFC 2326, 3914 DOI 10.17487/RFC2326, April 1998, . 3917 [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the 3918 Session Description Protocol (SDP) for ATM Bearer 3919 Connections", RFC 3108, DOI 10.17487/RFC3108, May 2001, 3920 . 3922 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 3923 with Session Description Protocol (SDP)", RFC 3264, 3924 DOI 10.17487/RFC3264, June 2002, . 3927 [RFC3312] Camarillo, G., Ed., Marshall, W., Ed., and J. Rosenberg, 3928 "Integration of Resource Management and Session Initiation 3929 Protocol (SIP)", RFC 3312, DOI 10.17487/RFC3312, October 3930 2002, . 3932 [RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple 3933 Capability Declaration", RFC 3407, DOI 10.17487/RFC3407, 3934 October 2002, . 3936 [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to 3937 Resource Reservation Flows", RFC 3524, 3938 DOI 10.17487/RFC3524, April 2003, . 3941 [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. 3942 Jacobson, "RTP: A Transport Protocol for Real-Time 3943 Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550, 3944 July 2003, . 3946 [RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth 3947 Modifiers for RTP Control Protocol (RTCP) Bandwidth", 3948 RFC 3556, DOI 10.17487/RFC3556, July 2003, 3949 . 3951 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute 3952 in Session Description Protocol (SDP)", RFC 3605, 3953 DOI 10.17487/RFC3605, October 2003, . 3956 [RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., 3957 "RTP Control Protocol Extended Reports (RTCP XR)", 3958 RFC 3611, DOI 10.17487/RFC3611, November 2003, 3959 . 3961 [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. 3962 Norrman, "The Secure Real-time Transport Protocol (SRTP)", 3963 RFC 3711, DOI 10.17487/RFC3711, March 2004, 3964 . 3966 [RFC3890] Westerlund, M., "A Transport Independent Bandwidth 3967 Modifier for the Session Description Protocol (SDP)", 3968 RFC 3890, DOI 10.17487/RFC3890, September 2004, 3969 . 3971 [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network 3972 Address Types (ANAT) Semantics for the Session Description 3973 Protocol (SDP) Grouping Framework", RFC 4091, 3974 DOI 10.17487/RFC4091, June 2005, . 3977 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 3978 the Session Description Protocol (SDP)", RFC 4145, 3979 DOI 10.17487/RFC4145, September 2005, . 3982 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E. 3983 Carrara, "Key Management Extensions for Session 3984 Description Protocol (SDP) and Real Time Streaming 3985 Protocol (RTSP)", RFC 4567, DOI 10.17487/RFC4567, July 3986 2006, . 3988 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session 3989 Description Protocol (SDP) Security Descriptions for Media 3990 Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, 3991 . 3993 [RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol 3994 (SDP) Source Filters", RFC 4570, DOI 10.17487/RFC4570, 3995 July 2006, . 3997 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 3998 Transport Layer Security (TLS) Protocol in the Session 3999 Description Protocol (SDP)", RFC 4572, 4000 DOI 10.17487/RFC4572, July 2006, . 4003 [RFC4574] Levin, O. and G. Camarillo, "The Session Description 4004 Protocol (SDP) Label Attribute", RFC 4574, 4005 DOI 10.17487/RFC4574, August 2006, . 4008 [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format 4009 for Binary Floor Control Protocol (BFCP) Streams", 4010 RFC 4583, DOI 10.17487/RFC4583, November 2006, 4011 . 4013 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 4014 "Extended RTP Profile for Real-time Transport Control 4015 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, 4016 DOI 10.17487/RFC4585, July 2006, . 4019 [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description 4020 Protocol (SDP) Content Attribute", RFC 4796, 4021 DOI 10.17487/RFC4796, February 2007, . 4024 [RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed., 4025 "The Message Session Relay Protocol (MSRP)", RFC 4975, 4026 DOI 10.17487/RFC4975, September 2007, . 4029 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 4030 "Codec Control Messages in the RTP Audio-Visual Profile 4031 with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104, 4032 February 2008, . 4034 [RFC5109] Li, A., Ed., "RTP Payload Format for Generic Forward Error 4035 Correction", RFC 5109, DOI 10.17487/RFC5109, December 4036 2007, . 4038 [RFC5159] Dondeti, L., Ed. and A. Jerichow, "Session Description 4039 Protocol (SDP) Attributes for Open Mobile Alliance (OMA) 4040 Broadcast (BCAST) Service and Content Protection", 4041 RFC 5159, DOI 10.17487/RFC5159, March 2008, 4042 . 4044 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 4045 (ICE): A Protocol for Network Address Translator (NAT) 4046 Traversal for Offer/Answer Protocols", RFC 5245, 4047 DOI 10.17487/RFC5245, April 2010, . 4050 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP 4051 Header Extensions", RFC 5285, DOI 10.17487/RFC5285, July 4052 2008, . 4054 [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of 4055 Service (QoS) Mechanism Selection in the Session 4056 Description Protocol (SDP)", RFC 5432, 4057 DOI 10.17487/RFC5432, March 2009, . 4060 [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size 4061 Real-Time Transport Control Protocol (RTCP): Opportunities 4062 and Consequences", RFC 5506, DOI 10.17487/RFC5506, April 4063 2009, . 4065 [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S., 4066 and P. Kyzivat, "A Session Description Protocol (SDP) 4067 Offer/Answer Mechanism to Enable File Transfer", RFC 5547, 4068 DOI 10.17487/RFC5547, May 2009, . 4071 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific 4072 Media Attributes in the Session Description Protocol 4073 (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009, 4074 . 4076 [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding 4077 Dependency in the Session Description Protocol (SDP)", 4078 RFC 5583, DOI 10.17487/RFC5583, July 2009, 4079 . 4081 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control 4082 Protocol (RTCP) Extensions for Single-Source Multicast 4083 Sessions with Unicast Feedback", RFC 5760, 4084 DOI 10.17487/RFC5760, February 2010, . 4087 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and 4088 Control Packets on a Single Port", RFC 5761, 4089 DOI 10.17487/RFC5761, April 2010, . 4092 [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control 4093 Protocol (DCCP)", RFC 5762, DOI 10.17487/RFC5762, April 4094 2010, . 4096 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework 4097 for Establishing a Secure Real-time Transport Protocol 4098 (SRTP) Security Context Using Datagram Transport Layer 4099 Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May 4100 2010, . 4102 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description 4103 Protocol (SDP) Grouping Framework", RFC 5888, 4104 DOI 10.17487/RFC5888, June 2010, . 4107 [RFC5939] Andreasen, F., "Session Description Protocol (SDP) 4108 Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939, 4109 September 2010, . 4111 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in 4112 the Session Description Protocol", RFC 5956, 4113 DOI 10.17487/RFC5956, September 2010, . 4116 [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions 4117 Defined for 3GPP Packet-Switched Streaming Service and 4118 Multimedia Broadcast/Multicast Service", RFC 6064, 4119 DOI 10.17487/RFC6064, January 2011, . 4122 [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source- 4123 Specific Multicast (SSM) Sessions", RFC 6128, 4124 DOI 10.17487/RFC6128, February 2011, . 4127 [RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP: 4128 Media Path Key Agreement for Unicast Secure RTP", 4129 RFC 6189, DOI 10.17487/RFC6189, April 2011, 4130 . 4132 [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for 4133 the Internet Key Exchange Protocol (IKE) in the Session 4134 Description Protocol (SDP)", RFC 6193, 4135 DOI 10.17487/RFC6193, April 2011, . 4138 [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media 4139 Control Channel Framework", RFC 6230, 4140 DOI 10.17487/RFC6230, May 2011, . 4143 [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image 4144 Attributes in the Session Description Protocol (SDP)", 4145 RFC 6236, DOI 10.17487/RFC6236, May 2011, 4146 . 4148 [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping 4149 between Unicast and Multicast RTP Sessions", RFC 6284, 4150 DOI 10.17487/RFC6284, June 2011, . 4153 [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax, 4154 "Unicast-Based Rapid Acquisition of Multicast RTP 4155 Sessions", RFC 6285, DOI 10.17487/RFC6285, June 2011, 4156 . 4158 [RFC6364] Begen, A., "Session Description Protocol Elements for the 4159 Forward Error Correction (FEC) Framework", RFC 6364, 4160 DOI 10.17487/RFC6364, October 2011, . 4163 [RFC6642] Wu, Q., Ed., Xia, F., and R. Even, "RTP Control Protocol 4164 (RTCP) Extension for a Third-Party Loss Report", RFC 6642, 4165 DOI 10.17487/RFC6642, June 2012, . 4168 [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., 4169 and K. Carlberg, "Explicit Congestion Notification (ECN) 4170 for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August 4171 2012, . 4173 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection 4174 Establishment for Media Anchoring (CEMA) for the Message 4175 Session Relay Protocol (MSRP)", RFC 6714, 4176 DOI 10.17487/RFC6714, August 2012, . 4179 [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A 4180 Datagram Congestion Control Protocol UDP Encapsulation for 4181 NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November 4182 2012, . 4184 [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control 4185 Protocol Version 2 (MRCPv2)", RFC 6787, 4186 DOI 10.17487/RFC6787, November 2012, . 4189 [RFC6849] Kaplan, H., Ed., Hedayat, K., Venna, N., Jones, P., and N. 4190 Stratton, "An Extension to the Session Description 4191 Protocol (SDP) and Real-time Transport Protocol (RTP) for 4192 Media Loopback", RFC 6849, DOI 10.17487/RFC6849, February 4193 2013, . 4195 [RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session 4196 Description Protocol (SDP) Media Capabilities 4197 Negotiation", RFC 6871, DOI 10.17487/RFC6871, February 4198 2013, . 4200 [RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S. 4201 Veikkolainen, "The Session Description Protocol (SDP) 4202 Alternate Connectivity (ALTC) Attribute", RFC 6947, 4203 DOI 10.17487/RFC6947, May 2013, . 4206 [RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman, 4207 "Miscellaneous Capabilities Negotiation in the Session 4208 Description Protocol (SDP)", RFC 7006, 4209 DOI 10.17487/RFC7006, September 2013, . 4212 [RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping 4213 Semantics in the Session Description Protocol", RFC 7104, 4214 DOI 10.17487/RFC7104, January 2014, . 4217 [RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session 4218 Description Protocol (SDP) Extension for Setting Audio and 4219 Video Media Streams over Circuit-Switched Bearers in the 4220 Public Switched Telephone Network (PSTN)", RFC 7195, 4221 DOI 10.17487/RFC7195, May 2014, . 4224 [RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay 4225 Attribute in the Session Description Protocol", RFC 7197, 4226 DOI 10.17487/RFC7197, April 2014, . 4229 [RFC7266] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control 4230 Protocol (RTCP) Extended Report (XR) Blocks for Mean 4231 Opinion Score (MOS) Metric Reporting", RFC 7266, 4232 DOI 10.17487/RFC7266, June 2014, . 4235 [RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O., 4236 Boronat, F., Montagud, M., and K. Gross, "Inter- 4237 Destination Media Synchronization (IDMS) Using the RTP 4238 Control Protocol (RTCP)", RFC 7272, DOI 10.17487/RFC7272, 4239 June 2014, . 4241 [RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H. 4242 Stokking, "RTP Clock Source Signalling", RFC 7273, 4243 DOI 10.17487/RFC7273, June 2014, . 4246 [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services 4247 (Diffserv) and Real-Time Communication", RFC 7657, 4248 DOI 10.17487/RFC7657, November 2015, . 4251 [T.38] "Procedures for real-time Group 3 facsimile communication 4252 over IP networks", . 4254 Author's Address 4256 Suhas Nandakumar 4257 Cisco 4258 170 West Tasman Drive 4259 San Jose, CA 95134 4260 USA 4262 Email: snandaku@cisco.com