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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 January 14, 2016 5 Expires: July 17, 2016 7 A Framework for SDP Attributes when Multiplexing 8 draft-ietf-mmusic-sdp-mux-attributes-12 10 Abstract 12 The Session Description Protocol (SDP) provides mechanisms to 13 describe attributes of multimedia sessions and of individual media 14 streams (e.g., Real-time Transport Protocol (RTP) sessions) within a 15 multimedia session. Typically media associated with individual media 16 descriptions ("m=" lines) represent RTP sessions and are thus carried 17 over individual underlying transport layer flows. For scenarios 18 where SDP is used to negotiate the usage of single 5-tuple for 19 sending and receiving media associated with multiple media 20 descriptions, it is required to understand the semantic implications 21 of the SDP attributes associated with the RTP Media Streams 22 multiplexed over a single underlying transport layer flow. 24 The purpose of this specification is to provide a framework for 25 analyzing the multiplexing characteristics of SDP attributes. This 26 specification also categorizes the existing SDP attributes based on 27 the framework described herein. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on July 17, 2016. 46 Copyright Notice 48 Copyright (c) 2016 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 6 66 4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . 6 67 4.1. Category: NORMAL . . . . . . . . . . . . . . . . . . . . 7 68 4.2. Category: NOT RECOMMENDED . . . . . . . . . . . . . . . . 7 69 4.3. Category: IDENTICAL . . . . . . . . . . . . . . . . . . . 8 70 4.4. Category: SUM . . . . . . . . . . . . . . . . . . . . . . 8 71 4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 9 72 4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 10 73 4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 11 74 4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 12 75 4.9. Category: TBD . . . . . . . . . . . . . . . . . . . . . . 12 76 5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 12 77 5.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 13 78 5.2. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 14 79 5.3. RFC5761: Multiplexing RTP and RTCP . . . . . . . . . . . 15 80 5.4. RFC3312: Integration of Resource Management and SIP . . . 15 81 5.5. RFC4574: SDP Label Attribute . . . . . . . . . . . . . . 16 82 5.6. RFC5432: QOS Mechanism Selection in SDP . . . . . . . . . 16 83 5.7. RFC4568: SDP Security Descriptions . . . . . . . . . . . 17 84 5.8. RFC5762: RTP over DCCP . . . . . . . . . . . . . . . . . 17 85 5.9. RFC6773: DCCP-UDP Encapsulation . . . . . . . . . . . . . 18 86 5.10. RFC5506: Reduced-Size RTCP in RTP Profile . . . . . . . . 19 87 5.11. RFC6787: Media Resource Control Protocol Version 2 . . . 19 88 5.12. RFC5245: ICE . . . . . . . . . . . . . . . . . . . . . . 20 89 5.13. RFC5285: RTP Header Extensions . . . . . . . . . . . . . 21 90 5.14. RFC3605: RTCP attribute in SDP . . . . . . . . . . . . . 22 91 5.15. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 22 92 5.16. RFC7273: RTP Clock Source Signalling . . . . . . . . . . 23 93 5.17. RFC6236: Image Attributes in SDP . . . . . . . . . . . . 24 94 5.18. RFC7197: Duplication Delay Attribute in SDP . . . . . . . 25 95 5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting . . . . 25 96 5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions . . 25 97 5.21. RFC6230: Media Control Channel Framework . . . . . . . . 26 98 5.22. RFC6364: SDP Elements for FEC Framework . . . . . . . . . 26 99 5.23. RFC4796: Content Attribute . . . . . . . . . . . . . . . 27 100 5.24. RFC3407: SDP Simple Capability Declaration . . . . . . . 27 101 5.25. RFC6284: Port Mapping between Unicast and Multicast RTP 102 Sessions . . . . . . . . . . . . . . . . . . . . . . . . 28 103 5.26. RFC6714: MSRP-CEMA . . . . . . . . . . . . . . . . . . . 28 104 5.27. RFC4583: SDP Format for BFCP Streams . . . . . . . . . . 29 105 5.28. RFC5547: SDP Offer/Answer for File Transfer . . . . . . . 30 106 5.29. RFC6849: SDP and RTP Media Loopback Extension . . . . . . 30 107 5.30. RFC5760: RTCP with Unicast Feedback . . . . . . . . . . . 31 108 5.31. RFC3611: RTCP XR . . . . . . . . . . . . . . . . . . . . 31 109 5.32. RFC5939: SDP Capability Negotiation . . . . . . . . . . . 32 110 5.33. RFC6871: SDP Media Capabilities Negotiation . . . . . . . 32 111 5.34. RFC7006: Miscellaneous Capabilities Negotiation SDP . . . 33 112 5.35. RFC4567: Key Management Extensions for SDP and RTSP . . . 34 113 5.36. RFC4572: Comedia over TLS in SDP . . . . . . . . . . . . 35 114 5.37. RFC4570: SDP Source Filters . . . . . . . . . . . . . . . 35 115 5.38. RFC6128: RTCP Port for Multicast Sessions . . . . . . . . 36 116 5.39. RFC6189: ZRTP . . . . . . . . . . . . . . . . . . . . . . 36 117 5.40. RFC4145: Connection-Oriented Media . . . . . . . . . . . 37 118 5.41. RFC6947: The SDP altc Attribute . . . . . . . . . . . . . 37 119 5.42. RFC7195: SDP Extension for Circuit Switched Bearers 120 in PSTN . . . . . . . . . . . . . . . . . . . . . . . . . 38 121 5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP) . . . 38 122 5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP 123 Attributes . . . . . . . . . . . . . . . . . . . . . . . 39 124 5.45. RFC6193: Media Description for IKE in SDP . . . . . . . . 39 125 5.46. RFC2326: Real Time Streaming Protocol . . . . . . . . . . 40 126 5.47. RFC6064: SDP and RTSP Extensions for 3GPP . . . . . . . . 41 127 5.48. RFC3108: ATM SDP . . . . . . . . . . . . . . . . . . . . 44 128 5.49. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 46 129 5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . . 47 130 5.51. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 47 131 5.52. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 47 132 5.53. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 48 133 5.54. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 49 134 5.55. ITU-T Q.1970 . . . . . . . . . . . . . . . . . . . . . . 51 135 5.56. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 51 136 5.57. RFC4975: The Message Session Relay Protocol . . . . . . . 52 137 5.58. Historical Attributes . . . . . . . . . . . . . . . . . . 53 138 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 53 139 6.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 54 140 6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth . . . 54 141 6.3. RFC3890: Bandwidth Modifier for SDP . . . . . . . . . . . 55 143 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 55 144 7.1. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 55 145 7.2. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 56 146 7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP 147 Sessions (RAMS) . . . . . . . . . . . . . . . . . . . . . 57 148 7.4. RFC6679: ECN for RTP over UDP/IP . . . . . . . . . . . . 57 149 7.5. RFC6642: Third-Party Loss Report . . . . . . . . . . . . 58 150 7.6. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 59 151 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 59 152 8.1. RFC5888: SDP Grouping Framework . . . . . . . . . . . . . 59 153 8.2. RFC3524: Mapping Media Streams to Resource 154 Reservation Flows . . . . . . . . . . . . . . . . . . . . 60 155 8.3. RFC4091: ANAT Semantics . . . . . . . . . . . . . . . . . 60 156 8.4. RFC5956: FEC Grouping Semantics in SDP . . . . . . . . . 60 157 8.5. RFC5583: Signaling Media Decoding Dependency in SDP . . . 61 158 8.6. RFC7104: Duplication Grouping Semantics in the SDP . . . 61 159 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 62 160 9.1. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 62 161 9.2. RFC7104: Duplication Grouping Semantics in the SDP . . . 62 162 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 63 163 10.1. RFC5432: QoS Mechanism Selection in SDP . . . . . . . . 63 164 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 63 165 11.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 64 166 12. content Attribute Analysis . . . . . . . . . . . . . . . . . 64 167 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 64 168 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 65 169 13.1. RFC5109: RTP Payload Format for Generic FEC . . . . . . 65 170 14. Multiplexing Considerations for Encapsulating Attributes . . 65 171 14.1. RFC3407: cpar Attribute Analysis . . . . . . . . . . . . 66 172 14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 66 173 14.2.1. Recommendation: Procedures for Potential 174 Configuration Pairing . . . . . . . . . . . . . . . 67 175 14.2.1.1. Example: Transport Capability Multiplexing . . . 68 176 14.2.1.2. Example: Attribute Capability Multiplexing . . . 69 177 14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 70 178 14.3.1. Recommendation: Dealing with Payload Type Numbers . 70 179 14.3.1.1. Example: Attribute Capability Under Shared 180 Payload Type . . . . . . . . . . . . . . . . . . 70 181 14.3.2. Recommendation: Dealing with Latent Configurations . 71 182 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 72 183 15.1. New 'Multiplexing Categories' subregistry . . . . . . . 72 184 15.2. 'Mux Category' column for subregistries . . . . . . . . 73 185 15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 73 186 15.2.2. Table: att-field (session level) . . . . . . . . . . 73 187 15.2.3. Table: att-field (both session and media level) . . 74 188 15.2.4. Table: att-field (media level only) . . . . . . . . 76 189 15.2.5. Table: att-field (source level) . . . . . . . . . . 79 190 15.2.6. Table: content SDP Parameters . . . . . . . . . . . 80 191 15.2.7. Table: Semantics for the 'group' SDP Attribute . . . 80 192 15.2.8. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 80 193 15.2.9. Table: 'ack' and 'nack' Attribute Values . . . . . . 81 194 15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . . 81 195 15.2.11. Table: 'cs-correlation' Attribute Values . . . . . . 82 196 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 82 197 15.2.13. Table: SDP/RTSP key management protocol identifiers 82 198 15.2.14. Table: Codec Control Messages . . . . . . . . . . . 83 199 15.2.15. Table: QoS Mechanism Tokens . . . . . . . . . . . . 83 200 15.2.16. Table: SDP Capability Negotiation Option Tags . . . 83 201 15.2.17. Table: Timestamp Reference Clock Source Parameters . 84 202 15.2.18. Table: Media Clock Source Parameters . . . . . . . . 84 203 16. Security Considerations . . . . . . . . . . . . . . . . . . . 84 204 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 85 205 18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 85 206 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 88 207 19.1. Normative References . . . . . . . . . . . . . . . . . . 88 208 19.2. Informative References . . . . . . . . . . . . . . . . . 88 209 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 96 211 1. Introduction 213 SDP defines several attributes for capturing characteristics that 214 apply to the individual media descriptions (described by "m=" lines") 215 and the overall multimedia session. Typically different media types 216 (audio, video, etc.) described using different media descriptions 217 represent separate RTP sessions that are carried over individual 218 transport layer flows. However 219 [I-D.ietf-mmusic-sdp-bundle-negotiation] defines a way to use a 220 single address:port combination (BUNDLE address) for receiving media 221 associated with multiple SDP media descriptions. This would for e.g. 222 allow the usage of a single set of Interactive Connectivity 223 Establishment (ICE) [RFC5245] candidates for multiple media 224 descriptions. This in turn has made necessary to understand the 225 interpretation and usage of the SDP attributes defined for the 226 multiplexed media descriptions. 228 Given the number of SDP attributes registered with the [IANA] and 229 possibility of new attributes being defined in the future, there is 230 need for generic future-proof framework to analyze these attributes 231 for their applicability in the transport multiplexing use-cases. 233 The document starts with providing the motivation for requiring such 234 a framework. This is followed by introduction to the SDP attribute 235 analysis framework/procedures, following which several sections apply 236 the framework to the SDP attributes registered with the [IANA]. 238 2. Terminology 240 5-tuple: A collection of the following values: source address, source 241 port, destination address, destination port, and transport-layer 242 protocol. 244 3GPP: Third Generation Partnership Project; see http://www.3gpp.org 245 for more information about this organization. 247 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 248 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 249 document are to be interpreted as described in [RFC2119]. 251 3. Motivation 253 The time and complications of setting up ICE [RFC5245] and Datagram 254 Transport Layer Security (DTLS) based Secure Real-time Transport 255 Protocol (SRTP) [RFC5763] transports for use by RTP, and conservation 256 of ports (to avoid maintaining large number of Network Address 257 Translator (NAT) bindings open, reduce time/ports needed for ICE to 258 detect connectivity), forms a requirement to try and reduce the 259 number of transport level flows needed. This has resulted in the 260 definition of ways, such as, [I-D.ietf-mmusic-sdp-bundle-negotiation] 261 to multiplex RTP over a single transport flow in order to preserve 262 network resources such as port numbers. This imposes further 263 restrictions on applicability of the SDP attributes as they are 264 defined today. 266 The specific problem is that there are attribute combinations which 267 make sense when specified on independent "m=" lines -- as with 268 classical SDP -- that do not make sense when those "m=" lines are 269 then multiplexed over the same transport. To give an obvious 270 example, ICE permits each "m=" line to have an independently 271 specified ice-ufrag attribute. However, if the media from multiple 272 "m=" lines is multiplexed over the same ICE component, then the 273 meaning of media-level ice-ufrag attributes becomes muddled. 275 At the time of writing this document there are close to 250 SDP 276 attributes registered with the [IANA] and more will be added in the 277 future. There is no clearly defined procedure to establish the 278 validity/applicability of these attributes when used with transport 279 multiplexing. 281 4. SDP Attribute Analysis Framework 283 Attributes in an SDP session description can be defined at the 284 session-level and media-level. Informally, these attributes could be 285 semantically grouped as noted below. 287 o Attributes related to media content such as media type, encoding 288 schemes, payload types. 290 o Attributes specifying media transport characteristics like RTP/RTP 291 Control Protocol (RTCP) port numbers, network addresses, QOS. 293 o Metadata description attributes capturing session timing and 294 origin information. 296 o Attributes establishing relationships between media descriptions 297 such as grouping framework [RFC5888] 299 With the above semantic grouping as a reference, the proposed 300 framework classifies each attribute into one of the following 301 categories: 303 4.1. Category: NORMAL 305 Attributes that can be independently specified when multiplexing and 306 retain their original semantics. 308 In the example given below, the direction and label attributes are 309 independently specified for audio and video "m=" lines. These 310 attributes are not impacted by multiplexing these media streams over 311 a single transport layer flow. 313 v=0 314 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 315 s= 316 c=IN IP4 host.atlanta.example.com 317 t=0 0 318 m=audio 49172 RTP/AVP 99 319 a=sendonly 320 a=label:1 321 a=rtpmap:99 iLBC/8000 322 m=video 49172 RTP/AVP 31 323 a=recvonly 324 a=label:2 325 a=rtpmap:31 H261/90000 327 4.2. Category: NOT RECOMMENDED 329 Attributes that are not recommended for multiplexing since their 330 usage under multiplexing might lead to incorrect behavior. 332 Example: Multiplexing media descriptions over a single Datagram 333 Congestion Control Protocol (DCCP) transport [RFC5762] is NOT 334 RECOMMENDED since DCCP being a connection oriented protocol doesn't 335 allow multiple connections on the same 5-tuple. 337 v=0 338 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com 339 s= 340 c=IN IP4 client.biloxi.example.com 341 t=0 0 342 m=video 5004 DCCP/RTP/AVP 99 343 a=rtpmap:99 h261/9000 344 a=dccp-service-code:SC=x52545056 345 a=setup:passive 346 a=connection:new 347 m=video 5004 DCCP/RTP/AVP 100 348 a=rtpmap:100 h261/9000 349 a=dccp-service-code:SC=x5254504f 350 a=setup:passive 351 a=connection:new 353 4.3. Category: IDENTICAL 355 Attributes and their associated values (if any) that MUST be 356 identical across all the media descriptions being multiplexed. 358 Attributes such as rtcp-mux fall into this category. Since RTCP 359 reporting is done per RTP session, RTCP Multiplexing MUST be enabled 360 for both the audio and video "m=" lines if they are transported over 361 a single 5-tuple. 363 v=0 364 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com 365 s= 366 c=IN IP4 client.biloxi.example.com 367 t=0 0 368 m=audio 34567 RTP/AVP 97 369 a=rtcp-mux 370 m=video 34567 RTP/AVP 31 371 a=rtpmap:31 H261/90000 372 a=rtcp-mux 374 4.4. Category: SUM 376 Attributes can be set as they are normally used but software using 377 them in the multiplexing scenario, MUST apply the sum of all the 378 attributes being multiplexed instead of trying to use them 379 independently. This is typically used for bandwidth or other rate 380 limiting attributes to the underlying transport. 382 The software parsing the SDP sample below, should use the aggregate 383 Application Specific (AS) bandwidth value from the individual media 384 descriptions to determine the AS value for the multiplexed session. 385 Thus the calculated AS value would be 256+64 kilobits per second for 386 the given example. 388 v=0 389 o=test 2890844526 2890842807 IN IP4 client.biloxi.example.com 390 c=IN IP4 client.biloxi.example.com 391 t=0 0 392 m=audio 49170 RTP/AVP 0 393 b=AS:64 394 m=video 51372 RTP/AVP 31 395 b=AS:256 397 4.5. Category: TRANSPORT 399 Attributes that can be set normally for multiple items in a 400 multiplexed group but the software MUST pick the one that's 401 associated with the "m=" line whose information is used for setting 402 up the underlying transport. 404 In the example below, "a=crypto" attribute is defined for both the 405 audio and the video "m=" lines. The video media line's a=crypto 406 attribute is chosen since its mid value (bar) appears first in the 407 a=group:BUNDLE line. This is due to BUNDLE grouping semantic 408 [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values 409 from "m=" line corresponding to the mid appearing first on the 410 a=group:BUNDLE line to be considered for setting up the RTP 411 Transport. 413 v=0 414 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 415 s= 416 c=IN IP4 host.atlanta.example.com 417 t=0 0 418 a=group:BUNDLE bar foo 419 m=audio 49172 RTP/AVP 99 420 a=mid:foo 421 a=crypto:1 AES_CM_128_HMAC_SHA1_80 422 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32 423 a=rtpmap:99 iLBC/8000 424 m=video 51374 RTP/AVP 31 425 a=mid:bar 426 a=crypto:1 AES_CM_128_HMAC_SHA1_80 427 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 428 a=rtpmap:96 H261/90000 430 4.6. Category: INHERIT 432 Attributes that encapsulate other SDP attributes or parameters. 433 These attributes inherit their multiplexing characteristics from the 434 attributes or parameters they encapsulate. Such attributes are 435 defined in [RFC3407], [RFC5939] and [RFC6871] as part of a generic 436 framework for indicating and negotiating transport, media, and media 437 format related capabilities in the SDP. 439 The inheritance manifests itself when the encapsulated attribute or 440 parameter is being leveraged. In the case of SDP Capability 441 Negotiation [RFC5939] for example, this occurs when a capability 442 (encapsulating attribute) is used as part of a configuration; the 443 configuration inherits the multiplexing category of each of its 444 constituent (encapsulated) attributes and parameters. This in turn 445 MAY place constraints on what constitutes a valid configuration from 446 a multiplexing point of view, e.g. because some attributes MUST be 447 IDENTICAL (see Section 14 for further details). 449 v=0 450 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 451 s= 452 c=IN IP4 host.atlanta.example.com 453 t=0 0 454 m=video 3456 RTP/AVP 100 455 a=rtpmap:100 VP8/90000 456 a=fmtp:100 max-fr=30;max-fs=8040 457 a=sqn: 0 458 a=cdsc: 1 video RTP/AVP 100 459 a=cpar: a=rtcp-mux 460 m=video 3456 RTP/AVP 101 461 a=rtpmap:101 VP8/90000 462 a=fmtp:100 max-fr=15;max-fs=1200 463 a=cdsc: 2 video RTP/AVP 101 464 a=cpar: a=rtcp-mux 466 In the above example, the category IDENTICAL is inherited for the 467 cpar encapsulated rtcp-mux attribute. 469 4.7. Category: IDENTICAL-PER-PT 471 Attributes that define the RTP payload configuration on per Payload 472 Type basis and MUST have identical values across all the media 473 descriptions for a given RTP Payload Type when repeated. These 474 Payload Types identify the same codec configuration as defined in the 475 Section 10.1.2 of [I-D.ietf-mmusic-sdp-bundle-negotiation] under this 476 context. 478 In the SDP example below, Payload Types 96 and 97 are repeated across 479 all the video "m=" lines and all the payload specific parameters (ex: 480 rtpmap, fmtp) are identical (Note: some line breaks included are due 481 to formatting only). 483 v=0 484 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 485 s= 486 c=IN IP4 host.atlanta.example.com 487 t=0 0 488 a=group:BUNDLE cam1 cam2 489 m=video 96 97 490 a=mid:cam1 491 a=rtpmap:96 H264/90000 492 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 493 max-mbps=108000; max-br=1000 494 a=rtpmap:97 H264/90000 495 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 496 max-mbps=7200; max-br=200 497 m=video 96 97 498 a=mid:cam2 499 a=rtpmap:96 H264/90000 500 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000; 501 max-mbps=108000; max-br=1000 502 a=rtpmap:97 H264/90000 503 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000; 504 max-mbps=7200; max-br=200 506 4.8. Category: SPECIAL 508 Attributes where the text in the specification defining the attribute 509 MUST be consulted for further handling when multiplexed. 511 As an example, for the attribute extmap [RFC5285], the specification 512 defining the extension needs to be referred to understand the 513 multiplexing implications. 515 4.9. Category: TBD 517 Attributes that have not been analyzed under the proposed 518 multiplexing framework. For the purposes of implementations it is 519 advised to consider "NOT RECOMMENDED" as the category when 520 multiplexing these attributes. 522 5. Analysis of Existing Attributes 524 This section analyzes attributes listed in [IANA], grouped under the 525 IETF document that defines them. 527 The "Level" column indicates whether the attribute is currently 528 specified as: 530 o S -- Session level 531 o M -- Media level 533 o B -- Both 535 o SR -- Source-level (for a single SSRC) [RFC5576] 537 The "Mux Category" column identifies multiplexing category assigned 538 per attribute and the "Notes" column captures additional informative 539 details regarding the assigned category, wherever necessary. 541 5.1. RFC4566: SDP 543 [RFC4566] defines SDP that is intended for describing multimedia 544 sessions for the purposes of session announcement, session 545 invitation, and other forms of multimedia session initiation. 547 +-----------------+---------------------+-------+-------------------+ 548 | Name | Notes | Level | Mux Category | 549 +-----------------+---------------------+-------+-------------------+ 550 | sendrecv | Not impacted | B | NORMAL | 551 | | | | | 552 | sendonly | Not impacted | B | NORMAL | 553 | | | | | 554 | recvonly | Not impacted | B | NORMAL | 555 | | | | | 556 | inactive | Not impacted | B | NORMAL | 557 | | | | | 558 | cat | Not impacted | S | NORMAL | 559 | | | | | 560 | ptime | The attribute value | M | IDENTICAL-PER-PT | 561 | | MUST be same for a | | | 562 | | given codec | | | 563 | | configuration | | | 564 | | | | | 565 | maxptime | The attribute value | M | IDENTICAL-PER-PT | 566 | | MUST be same for a | | | 567 | | given codec | | | 568 | | configuration | | | 569 | | | | | 570 | orient | Not Impacted | M | NORMAL | 571 | | | | | 572 | framerate | The attribute value | M | IDENTICAL-PER-PT | 573 | | MUST be same for a | | | 574 | | given codec | | | 575 | | configuration | | | 576 | | | | | 577 | quality | Not Impacted | M | NORMAL | 578 | | | | | 579 | rtpmap | The attribute value | M | IDENTICAL-PER-PT | 580 | | MUST be same for a | | | 581 | | given codec | | | 582 | | configuration | | | 583 | | | | | 584 | fmtp | The attribute value | M | IDENTICAL-PER-PT | 585 | | MUST be same for a | | | 586 | | given codec | | | 587 | | configuration | | | 588 | | | | | 589 | keywds | Not impacted | S | NORMAL | 590 | | | | | 591 | type | Not Impacted | S | NORMAL | 592 | | | | | 593 | type:broadcast | Not Impacted | S | NORMAL | 594 | | | | | 595 | type:H332 | Not Impacted | S | NORMAL | 596 | | | | | 597 | type:meeting | Not Impacted | S | NORMAL | 598 | | | | | 599 | type:moderated | Not Impacted | S | NORMAL | 600 | | | | | 601 | type:test | Not Impacted | S | NORMAL | 602 | | | | | 603 | tool | Not Impacted | S | NORMAL | 604 | | | | | 605 | charset | Not Impacted | S | NORMAL | 606 | | | | | 607 | sdplang | Not Impacted | B | NORMAL | 608 | | | | | 609 | lang | Not Impacted | B | NORMAL | 610 | | | | | 611 +-----------------+---------------------+-------+-------------------+ 613 RFC4566 Attribute Analysis 615 5.2. RFC4585: RTP/AVPF 617 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 618 enables receivers to provide, statistically, more immediate feedback 619 to the senders and thus allows for short-term adaptation and 620 efficient feedback-based repair mechanisms to be implemented. 622 +----------+----------------------------+-------+-------------------+ 623 | Name | Notes | Level | Mux Category | 624 +----------+----------------------------+-------+-------------------+ 625 | rtcp-fb | Since RTCP feedback | M | IDENTICAL-PER-PT | 626 | | attributes are Payload | | | 627 | | Type (PT) scoped, their | | | 628 | | values MUST be identical | | | 629 | | for a given PT across the | | | 630 | | multiplexed "m=" lines. | | | 631 | | | | | 632 +----------+----------------------------+-------+-------------------+ 634 RFC4585 Attribute Analysis 636 5.3. RFC5761: Multiplexing RTP and RTCP 638 [RFC5761] discusses issues that arise when multiplexing RTP data 639 packets and RTP Control Protocol (RTCP) packets on a single UDP port. 640 It describes when such multiplexing is and is not appropriate, and it 641 explains how the SDP can be used to signal multiplexed sessions. 643 +-----------+----------------------------------+-------+------------+ 644 | Name | Notes | Level | Mux | 645 | | | | Category | 646 +-----------+----------------------------------+-------+------------+ 647 | rtcp-mux | RTP and RTCP Multiplexing | M | IDENTICAL | 648 | | affects the entire RTP session | | | 649 | | | | | 650 +-----------+----------------------------------+-------+------------+ 652 RFC5761 Attribute Analysis 654 5.4. RFC3312: Integration of Resource Management and SIP 656 [RFC3312] defines a generic framework for preconditions, which are 657 extensible through IANA registration. This document also discusses 658 how network quality of service can be made a precondition for 659 establishment of sessions initiated by the Session Initiation 660 Protocol (SIP). These preconditions require that the participant 661 reserve network resources before continuing with the session. 663 +-------+-----------------------+-------+------------------+ 664 | Name | Notes | Level | Mux Category | 665 +-------+-----------------------+-------+------------------+ 666 | des | Refer to notes below | M | NOT RECOMMENDED | 667 | | | | | 668 | conf | Refer to notes below | M | NOT RECOMMENDED | 669 | | | | | 670 | curr | Refer to notes below | M | NOT RECOMMENDED | 671 | | | | | 672 +-------+-----------------------+-------+------------------+ 674 RFC3312 Attribute Analysis 676 NOTE: A mismatched set of preconditions across media descriptions 677 results in Session establishment failures due to inability in meeting 678 the right resource reservations requested. 680 5.5. RFC4574: SDP Label Attribute 682 [RFC4574] defines a new SDP media-level attribute: "label". The 683 "label" attribute carries a pointer to a media stream in the context 684 of an arbitrary network application that uses SDP. The sender of the 685 SDP document can attach the "label" attribute to a particular media 686 stream or streams. The application can then use the provided pointer 687 to refer to each particular media stream in its context. 689 +--------+---------------+-------+--------------+ 690 | Name | Notes | Level | Mux Category | 691 +--------+---------------+-------+--------------+ 692 | label | Not Impacted | M | NORMAL | 693 | | | | | 694 +--------+---------------+-------+--------------+ 696 RFC4574 Attribute Analysis 698 5.6. RFC5432: QOS Mechanism Selection in SDP 700 [RFC5432] defines procedures to negotiate QOS mechanisms using the 701 SDP offer/answer model. 703 +----------------+----------------------------+-------+-------------+ 704 | Name | Notes | Level | Mux | 705 | | | | Category | 706 +----------------+----------------------------+-------+-------------+ 707 | qos-mech-send | Refer to section Section | B | TRANSPORT | 708 | | 10 | | | 709 | | | | | 710 | qos-mech-recv | Refer to section Section | B | TRANSPORT | 711 | | 10 | | | 712 | | | | | 713 +----------------+----------------------------+-------+-------------+ 715 RFC5432 Attribute Analysis 717 5.7. RFC4568: SDP Security Descriptions 719 [RFC4568] defines a SDP cryptographic attribute for unicast media 720 streams. The attribute describes a cryptographic key and other 721 parameters that serve to configure security for a unicast media 722 stream in either a single message or a roundtrip exchange. 724 +---------+------------------------------------+-------+------------+ 725 | Name | Notes | Level | Mux | 726 | | | | Category | 727 +---------+------------------------------------+-------+------------+ 728 | crypto | crypto attribute MUST be the one | M | TRANSPORT | 729 | | that corresponds to the "m=" line | | | 730 | | chosen for setting up the | | | 731 | | underlying transport flow | | | 732 | | | | | 733 +---------+------------------------------------+-------+------------+ 735 RFC4568 Attribute Analysis 737 5.8. RFC5762: RTP over DCCP 739 RTP is a widely used transport for real-time multimedia on IP 740 networks. DCCP is a transport protocol that provides desirable 741 services for real-time applications. [RFC5762] specifies a mapping 742 of RTP onto DCCP, along with associated signaling, such that real- 743 time applications can make use of the services provided by DCCP. 745 +--------------------+---------------------+---------+--------------+ 746 | Name | Notes | Current | Mux Category | 747 +--------------------+---------------------+---------+--------------+ 748 | dccp-service-code | If RFC6773 is not | M | NOT | 749 | | being used in | | RECOMMENDED | 750 | | addition to | | | 751 | | RFC5762, the port | | | 752 | | in the "m=" line is | | | 753 | | a DCCP port. DCCP | | | 754 | | being a connection | | | 755 | | oriented protocol, | | | 756 | | it does not allow | | | 757 | | multiple | | | 758 | | connections on the | | | 759 | | same 5-tuple | | | 760 | | | | | 761 +--------------------+---------------------+---------+--------------+ 763 RFC5762 Attribute Analysis 765 If RFC6773 is being used in addition to RFC5762 and provided that 766 DCCP-in-UDP layer has additional demultiplexing, then it can be 767 possible to use different DCCP service codes for each DCCP flow, 768 given each uses a different DCCP port. Although doing so might 769 conflict with the media type of the "m=" line. None of this is 770 standardized yet and it wouldn't work as explained. Hence 771 multiplexing MUST NOT be performed even in this alternate scenario. 773 5.9. RFC6773: DCCP-UDP Encapsulation 775 [RFC6773] document specifies an alternative encapsulation of DCCP, 776 referred to as DCCP-UDP. This encapsulation allows DCCP to be 777 carried through the current generation of Network Address Translation 778 (NAT) middle boxes without modification of those middle boxes. 780 +------------+-------------------------------+-------+--------------+ 781 | Name | Notes | Level | Mux Category | 782 +------------+-------------------------------+-------+--------------+ 783 | dccp-port | Multiplexing MUST NOT be | M | NOT | 784 | | performed due to potential | | RECOMMENDED | 785 | | conflict between the port | | | 786 | | used for DCCP | | | 787 | | en/decapsulation and the RTP | | | 788 | | | | | 789 +------------+-------------------------------+-------+--------------+ 791 RFC6773 Attribute Analysis 793 NOTE: RFC6773 is about tunneling DCCP in UDP, with the UDP port being 794 the port of the DCCP en-/de-capsulation service. This encapsulation 795 allows arbitrary DCCP packets to be encapsulated and the DCCP port 796 chosen can conflict with the port chosen for the RTP traffic. For 797 multiplexing several DCCP-in-UDP encapsulations on the same UDP port, 798 with no RTP traffic on the same port implies collapsing several DCCP 799 port spaces together. This can or cannot work depending on the 800 nature of DCCP encapsulation and ports choices thus rendering it to 801 be very application dependent. 803 5.10. RFC5506: Reduced-Size RTCP in RTP Profile 805 [RFC5506] discusses benefits and issues that arise when allowing RTCP 806 packets to be transmitted with reduced size. 808 +-------------+--------------------------------+-------+------------+ 809 | Name | Notes | Level | Mux | 810 | | | | Category | 811 +-------------+--------------------------------+-------+------------+ 812 | rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL | 813 | | entire RTP session | | | 814 | | | | | 815 +-------------+--------------------------------+-------+------------+ 817 RFC5506 Attribute Analysis 819 5.11. RFC6787: Media Resource Control Protocol Version 2 821 The Media Resource Control Protocol Version 2 (MRCPv2) allows client 822 hosts to control media service resources such as speech synthesizers, 823 recognizers, verifiers, and identifiers residing in servers on the 824 network. MRCPv2 is not a "stand-alone" protocol -- it relies on 825 other protocols, such as the SIP, to coordinate MRCPv2 clients and 826 servers, and manage session between them, and SDP to describe, 827 discover, and exchange capabilities. It also depends on SIP and SDP 828 to establish the media sessions and associated parameters between the 829 media source or sink and the media server. Once this is done, the 830 MRCPv2 exchange operates over the control session established above, 831 allowing the client to control the media processing resources on the 832 speech resource server. [RFC6787] defines attributes for this 833 purpose. 835 +-----------+---------------+-------+--------------+ 836 | Name | Notes | Level | Mux Category | 837 +-----------+---------------+-------+--------------+ 838 | resource | Not Impacted | M | NORMAL | 839 | | | | | 840 | channel | Not Impacted | M | NORMAL | 841 | | | | | 842 | cmid | Not Impacted | M | NORMAL | 843 | | | | | 844 +-----------+---------------+-------+--------------+ 846 RFC6787 Attribute Analysis 848 5.12. RFC5245: ICE 850 [RFC5245] describes a protocol for NAT traversal for UDP-based 851 multimedia sessions established with the offer/answer model. ICE 852 makes use of the Session Traversal Utilities for NAT (STUN) protocol 853 and its extension, Traversal Using Relay NAT (TURN). ICE can be used 854 by any protocol utilizing the offer/answer model, such as the SIP. 856 +--------------------+-------------------------+-------+------------+ 857 | Name | Notes | Level | Mux | 858 | | | | Category | 859 +--------------------+-------------------------+-------+------------+ 860 | ice-lite | Not Impacted | S | NORMAL | 861 | | | | | 862 | ice-options | Not Impacted | S | NORMAL | 863 | | | | | 864 | ice-mismatch | Not Impacted | S | NORMAL | 865 | | | | | 866 | ice-pwd | ice-pwd MUST be the one | B | TRANSPORT | 867 | | that corresponds to the | | | 868 | | "m=" line chosen for | | | 869 | | setting up the | | | 870 | | underlying transport | | | 871 | | flow | | | 872 | | | | | 873 | ice-ufrag | ice-ufrag MUST be the | B | TRANSPORT | 874 | | one that corresponds to | | | 875 | | the "m=" line chosen | | | 876 | | for setting up the | | | 877 | | underlying transport | | | 878 | | flow | | | 879 | | | | | 880 | candidate | ice candidate MUST be | M | TRANSPORT | 881 | | the one that | | | 882 | | corresponds to the "m=" | | | 883 | | line chosen for setting | | | 884 | | up the underlying | | | 885 | | transport flow | | | 886 | | | | | 887 | remote-candidates | ice remote candidate | M | TRANSPORT | 888 | | MUST be the one that | | | 889 | | corresponds to the "m=" | | | 890 | | line chosen for setting | | | 891 | | up the underlying | | | 892 | | transport flow | | | 893 | | | | | 894 +--------------------+-------------------------+-------+------------+ 896 RFC5245 Attribute Analysis 898 5.13. RFC5285: RTP Header Extensions 900 [RFC5285] provides a general mechanism to use the header extension 901 feature of RTP. It provides the option to use a small number of 902 small extensions in each RTP packet, where the universe of possible 903 extensions is large and registration is de-centralized. The actual 904 extensions in use in a session are signaled in the setup information 905 for that session. 907 +---------+-------------------------------------+-------+-----------+ 908 | Name | Notes | Level | Mux | 909 | | | | Category | 910 +---------+-------------------------------------+-------+-----------+ 911 | extmap | Specific RTP extension document | B | SPECIAL | 912 | | MUST be referred | | | 913 | | | | | 914 +---------+-------------------------------------+-------+-----------+ 916 RFC5285 Attribute Analysis 918 5.14. RFC3605: RTCP attribute in SDP 920 Originally, SDP assumed that RTP and RTCP were carried on consecutive 921 ports. However, this is not always true when NATs are involved. 922 [RFC3605] specifies an early mechanism to indicate the RTCP port. 924 +-------+--------------------------------------+-------+------------+ 925 | Name | Notes | Level | Mux | 926 | | | | Category | 927 +-------+--------------------------------------+-------+------------+ 928 | rtcp | RTCP Port MUST be the one that | M | TRANSPORT | 929 | | corresponds to the "m=" line chosen | | | 930 | | for setting up the underlying | | | 931 | | transport flow. | | | 932 | | | | | 933 +-------+--------------------------------------+-------+------------+ 935 RFC3605 Attribute Analysis 937 5.15. RFC5576: Source-Specific SDP Attributes 939 [RFC5576] defines a mechanism to describe RTP media sources, which 940 are identified by their synchronization source (SSRC) identifiers, in 941 SDP, to associate attributes with these sources, and to express 942 relationships among sources. It also defines several source-level 943 attributes that can be used to describe properties of media sources. 945 +----------------+----------------------+-------+-------------------+ 946 | Name | Notes | Level | Mux Category | 947 +----------------+----------------------+-------+-------------------+ 948 | ssrc | Refer to Notes below | M | NORMAL | 949 | | | | | 950 | ssrc-group | Refer to Section 9 | M | NORMAL | 951 | | for specific | | | 952 | | analysis of the | | | 953 | | grouping semantics | | | 954 | | | | | 955 | cname | Not Impacted | SR | NORMAL | 956 | | | | | 957 | previous-ssrc | Refer to notes below | SR | NORMAL | 958 | | | | | 959 | fmtp | The attribute value | SR | IDENTICAL-PER-PT | 960 | | MUST be same for a | | | 961 | | given codec | | | 962 | | configuration | | | 963 | | | | | 964 +----------------+----------------------+-------+-------------------+ 966 RFC5576 Attribute Analysis 968 NOTE: If SSRCs are repeated across "m=" lines being multiplexed, they 969 MUST all represent the same underlying RTP Source. 971 5.16. RFC7273: RTP Clock Source Signalling 973 [RFC7273] specifies SDP signalling that identifies timestamp 974 reference clock sources and SDP signalling that identifies the media 975 clock sources in a multimedia session. 977 +--------------------+---------------+-------+--------------+ 978 | Name | Notes | Level | Mux Category | 979 +--------------------+---------------+-------+--------------+ 980 | ts-refclk | Not Impacted | B | NORMAL | 981 | | | | | 982 | mediaclk | Not Impacted | B | NORMAL | 983 | | | | | 984 | ts-refclk:ntp | Not Impacted | B | NORMAL | 985 | | | | | 986 | ts-refclk:ptp | Not Impacted | B | NORMAL | 987 | | | | | 988 | ts-refclk:gps | Not Impacted | B | NORMAL | 989 | | | | | 990 | ts-refclk:gal | Not Impacted | B | NORMAL | 991 | | | | | 992 | ts-refclk:glonass | Not Impacted | B | NORMAL | 993 | | | | | 994 | ts-refclk:local | Not Impacted | B | NORMAL | 995 | | | | | 996 | ts-refclk:private | Not Impacted | B | NORMAL | 997 | | | | | 998 | mediaclk:sender | Not Impacted | B | NORMAL | 999 | | | | | 1000 | mediaclk:direct | Not Impacted | B | NORMAL | 1001 | | | | | 1002 | mediaclk:IEEE1722 | Not Impacted | B | NORMAL | 1003 | | | | | 1004 +--------------------+---------------+-------+--------------+ 1006 RFC7273 Attribute Analysis 1008 5.17. RFC6236: Image Attributes in SDP 1010 [RFC6236] proposes a new generic session setup attribute to make it 1011 possible to negotiate different image attributes such as image size. 1012 A possible use case is to make it possible for a low-end hand-held 1013 terminal to display video without the need to rescale the image, 1014 something that may consume large amounts of memory and processing 1015 power. The document also helps to maintain an optimal bitrate for 1016 video as only the image size that is desired by the receiver is 1017 transmitted. 1019 +------------+--------------------------+-------+-------------------+ 1020 | Name | Notes | Level | Mux Category | 1021 +------------+--------------------------+-------+-------------------+ 1022 | imageattr | The attribute value MUST | M | IDENTICAL-PER-PT | 1023 | | be same for a given | | | 1024 | | codec configuration | | | 1025 | | | | | 1026 +------------+--------------------------+-------+-------------------+ 1028 RFC6236 Attribute Analysis 1030 5.18. RFC7197: Duplication Delay Attribute in SDP 1032 [RFC7197] defines an attribute to indicate the presence of temporally 1033 redundant media streams and the duplication delay in SDP. 1035 +--------------------+---------------+-------+--------------+ 1036 | Name | Notes | Level | Mux Category | 1037 +--------------------+---------------+-------+--------------+ 1038 | duplication-delay | Not Impacted | B | NORMAL | 1039 | | | | | 1040 +--------------------+---------------+-------+--------------+ 1042 RFC7197 Attribute Analysis 1044 5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting 1046 [RFC7266] defines an RTCP Extended Report (XR) Block including two 1047 new segment types and associated SDP parameters that allow the 1048 reporting of mean opinion score (MOS) Metrics for use in a range of 1049 RTP applications. 1051 +-------------+---------------+-------+--------------+ 1052 | Name | Notes | Level | Mux Category | 1053 +-------------+---------------+-------+--------------+ 1054 | calgextmap | Not Impacted | B | NORMAL | 1055 | | | | | 1056 +-------------+---------------+-------+--------------+ 1058 RFC7266 Attribute Analysis 1060 5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions 1062 [RFC6285] describes a method using the existing RTP and RTCP 1063 machinery that reduces the acquisition delay. In this method, an 1064 auxiliary unicast RTP session carrying the Reference Information to 1065 the receiver precedes or accompanies the multicast stream. This 1066 unicast RTP flow can be transmitted at a faster than natural bitrate 1067 to further accelerate the acquisition. The motivating use case for 1068 this capability is multicast applications that carry real-time 1069 compressed audio and video. 1071 +---------------+-------------------+-------+------------------+ 1072 | Name | Notes | Level | Mux Category | 1073 +---------------+-------------------+-------+------------------+ 1074 | rams-updates | Not recommended | M | NOT RECOMMENDED | 1075 | | | | | 1076 +---------------+-------------------+-------+------------------+ 1078 RFC6285 Attribute Analysis 1080 5.21. RFC6230: Media Control Channel Framework 1082 [RFC6230] describes a framework and protocol for application 1083 deployment where the application programming logic and media 1084 processing are distributed. This implies that application 1085 programming logic can seamlessly gain access to appropriate resources 1086 that are not co-located on the same physical network entity. The 1087 framework uses SIP to establish an application-level control 1088 mechanism between application servers and associated external servers 1089 such as media servers. 1091 +---------+---------------+-------+--------------+ 1092 | Name | Notes | Level | Mux Category | 1093 +---------+---------------+-------+--------------+ 1094 | cfw-id | Not Impacted | M | NORMAL | 1095 | | | | | 1096 +---------+---------------+-------+--------------+ 1098 RFC6230 Attribute Analysis 1100 5.22. RFC6364: SDP Elements for FEC Framework 1102 [RFC6364] specifies the use of SDP to describe the parameters 1103 required to signal the Forward Error Correction (FEC) Framework 1104 Configuration Information between the sender(s) and receiver(s). 1105 This document also provides examples that show the semantics for 1106 grouping multiple source and repair flows together for the 1107 applications that simultaneously use multiple instances of the FEC 1108 Framework. 1110 +------------------+-----------------------------+-------+----------+ 1111 | Name | Notes | Level | Mux | 1112 | | | | Category | 1113 +------------------+-----------------------------+-------+----------+ 1114 | fec-source-flow | Specific FEC scheme | M | SPECIAL | 1115 | | document needs to be | | | 1116 | | referred | | | 1117 | | | | | 1118 | fec-repair-flow | Specific FEC scheme | M | SPECIAL | 1119 | | document needs to be | | | 1120 | | referred | | | 1121 | | | | | 1122 | repair-window | Specific FEC scheme | M | SPECIAL | 1123 | | document needs to be | | | 1124 | | referred | | | 1125 | | | | | 1126 +------------------+-----------------------------+-------+----------+ 1128 RFC6364 Attribute Analysis 1130 5.23. RFC4796: Content Attribute 1132 [RFC4796] defines a new SDP media-level attribute, 'content'. The 1133 'content' attribute defines the content of the media stream to a more 1134 detailed level than the media description line. The sender of an SDP 1135 session description can attach the 'content' attribute to one or more 1136 media streams. The receiving application can then treat each media 1137 stream differently (e.g., show it on a big or small screen) based on 1138 its content. 1140 +----------+---------------+-------+--------------+ 1141 | Name | Notes | Level | Mux Category | 1142 +----------+---------------+-------+--------------+ 1143 | content | Not Impacted | M | NORMAL | 1144 | | | | | 1145 +----------+---------------+-------+--------------+ 1147 RFC4796 Attribute Analysis 1149 5.24. RFC3407: SDP Simple Capability Declaration 1151 [RFC3407] defines a set of SDP attributes that enables SDP to provide 1152 a minimal and backwards compatible capability declaration mechanism. 1154 +----------+------------------------+-------+--------------+ 1155 | Name | Notes | Level | Mux Category | 1156 +----------+------------------------+-------+--------------+ 1157 | sqn | Not Impacted | B | NORMAL | 1158 | | | | | 1159 | cdsc | Not Impacted. | B | NORMAL | 1160 | | | | | 1161 | cpar | Refer to Section 14 | B | INHERIT | 1162 | | | | | 1163 | cparmin | Refer to notes below | B | SPECIAL | 1164 | | | | | 1165 | cparmax | Refer to notes below | B | SPECIAL | 1166 | | | | | 1167 +----------+------------------------+-------+--------------+ 1169 RFC3407 Attribute Analysis 1171 NOTE: Since the attributes (a=cparmin and a=cparmax) define minimum 1172 and maximum numerical values associated with the attributes described 1173 in a=cpar, it is recommended to consult the document defining the 1174 attribute. 1176 5.25. RFC6284: Port Mapping between Unicast and Multicast RTP Sessions 1178 [RFC6284] presents a port mapping solution that allows RTP receivers 1179 to choose their own ports for an auxiliary unicast session in RTP 1180 applications using both unicast and multicast services. The solution 1181 provides protection against denial-of-service or packet amplification 1182 attacks that could be used to cause one or more RTP packets to be 1183 sent to a victim client. 1185 +------------------+-------------------------+-------+--------------+ 1186 | Name | Notes | Level | Mux Category | 1187 +------------------+-------------------------+-------+--------------+ 1188 | portmapping-req | Not recommended, if | M | NOT | 1189 | | port mapping is | | RECOMMENDED | 1190 | | required by the | | | 1191 | | application | | | 1192 | | | | | 1193 +------------------+-------------------------+-------+--------------+ 1195 RFC6284 Attribute Analysis 1197 5.26. RFC6714: MSRP-CEMA 1199 [RFC6714] defines a Message Session Relay Protocol (MSRP) extension, 1200 Connection Establishment for Media Anchoring (CEMA). Support of this 1201 extension is OPTIONAL. The extension allows middle boxes to anchor 1202 the MSRP connection, without the need for middle boxes to modify the 1203 MSRP messages; thus, it also enables secure end-to-end MSRP 1204 communication in networks where such middle boxes are deployed. This 1205 document also defines a SDP attribute, 'msrp-cema', that MSRP 1206 endpoints use to indicate support of the CEMA extension. 1208 +------------+-----------------------+-------+--------------+ 1209 | Name | Notes | Level | Mux Category | 1210 +------------+-----------------------+-------+--------------+ 1211 | msrp-cema | Refer to notes below | M | TBD | 1212 | | | | | 1213 +------------+-----------------------+-------+--------------+ 1215 RFC6714 Attribute Analysis 1217 NOTE: As per section 9.1 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1218 there exists no publicly available specification that defines 1219 procedures for multiplexing/demultiplexing MRSP flows over a single 1220 5-tuple. Once such a specification is available, the multiplexing 1221 categories assignments for the attributes in this section MUST be 1222 revisited. 1224 5.27. RFC4583: SDP Format for BFCP Streams 1226 [RFC4583] document specifies how to describe Binary Floor Control 1227 Protocol (BFCP) streams in SDP descriptions. User agents using the 1228 offer/answer model to establish BFCP streams use this format in their 1229 offers and answers. 1231 +------------+---------------------------------+-------+------------+ 1232 | Name | Notes | Level | Mux | 1233 | | | | Category | 1234 +------------+---------------------------------+-------+------------+ 1235 | floorctrl | The attribute MUST be repeated | M | IDENTICAL | 1236 | | across all the multiplexed "m=" | | | 1237 | | lines | | | 1238 | | | | | 1239 | confid | Not Impacted | M | NORMAL | 1240 | | | | | 1241 | userid | Not Impacted | M | NORMAL | 1242 | | | | | 1243 | floorid | The floorid MUST be globally | M | NORMAL | 1244 | | unique | | | 1245 | | | | | 1246 +------------+---------------------------------+-------+------------+ 1248 RFC4583 Attribute Analysis 1250 5.28. RFC5547: SDP Offer/Answer for File Transfer 1252 [RFC5547] provides a mechanism to negotiate the transfer of one or 1253 more files between two endpoints by using the SDP offer/answer model 1254 specified in [RFC3264]. 1256 +-------------------+-----------------------+-------+--------------+ 1257 | Name | Notes | Level | Mux Category | 1258 +-------------------+-----------------------+-------+--------------+ 1259 | file-selector | Refer to notes below | M | TBD | 1260 | | | | | 1261 | file-transfer-id | Refer to notes below | M | TBD | 1262 | | | | | 1263 | file-disposition | Refer to notes below | M | TBD | 1264 | | | | | 1265 | file-date | Refer to notes below | M | TBD | 1266 | | | | | 1267 | file-icon | Refer to notes below | M | TBD | 1268 | | | | | 1269 | file-range | Refer to notes below | M | TBD | 1270 | | | | | 1271 +-------------------+-----------------------+-------+--------------+ 1273 RFC5547 Attribute Analysis 1275 NOTE: As per section 9.1 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 1276 there exists no publicly available specification that defines 1277 procedures for multiplexing/demultiplexing MRSP flows over a single 1278 5-tuple. Once such a specification is available, the multiplexing 1279 categories assignments for attributes in this section MUST be 1280 revisited. 1282 5.29. RFC6849: SDP and RTP Media Loopback Extension 1284 [RFC6849] adds new SDP media types and attributes, which enable 1285 establishment of media sessions where the media is looped back to the 1286 transmitter. Such media sessions will serve as monitoring and 1287 troubleshooting tools by providing the means for measurement of more 1288 advanced Voice over IP (VoIP), Real-time Text, and Video over IP 1289 performance metrics. 1291 +---------------------+-----------------+-------+-------------------+ 1292 | Name | Notes | Level | Mux Category | 1293 +---------------------+-----------------+-------+-------------------+ 1294 | loopback rtp-pkt- | The attribute | M | IDENTICAL-PER-PT | 1295 | loopback | value MUST be | | | 1296 | | same for a | | | 1297 | | given codec | | | 1298 | | configuration | | | 1299 | | | | | 1300 | loopback rtp-media- | The attribute | M | IDENTICAL-PER-PT | 1301 | loopback | value MUST be | | | 1302 | | same for a | | | 1303 | | given codec | | | 1304 | | configuration | | | 1305 | | | | | 1306 | loopback-source | Not Impacted | M | NORMAL | 1307 | | | | | 1308 | loopback-mirror | Not Impacted | M | NORMAL | 1309 | | | | | 1310 +---------------------+-----------------+-------+-------------------+ 1312 RFC6849 Analysis 1314 5.30. RFC5760: RTCP with Unicast Feedback 1316 [RFC5760] specifies an extension to RTCP to use unicast feedback to a 1317 multicast sender. The proposed extension is useful for single-source 1318 multicast sessions such as Source-Specific Multicast (SSM) 1319 communication where the traditional model of many-to-many group 1320 communication is either not available or not desired. 1322 +---------------+------------------------------+-------+------------+ 1323 | Name | Notes | Level | Mux | 1324 | | | | Category | 1325 +---------------+------------------------------+-------+------------+ 1326 | rtcp-unicast | The attribute MUST be | M | IDENTICAL | 1327 | | reported across all "m=" | | | 1328 | | lines multiplexed | | | 1329 | | | | | 1330 +---------------+------------------------------+-------+------------+ 1332 RFC5760 Attribute Analysis 1334 5.31. RFC3611: RTCP XR 1336 [RFC3611] defines the Extended Report (XR) packet type for RTCP, and 1337 defines how the use of XR packets can be signaled by an application 1338 if it employs the Session Description Protocol (SDP). 1340 +----------+---------------+-------+--------------+ 1341 | Name | Notes | Level | Mux Category | 1342 +----------+---------------+-------+--------------+ 1343 | rtcp-xr | Not Impacted | B | NORMAL | 1344 | | | | | 1345 +----------+---------------+-------+--------------+ 1347 RFC3611 Attribute Analysis 1349 5.32. RFC5939: SDP Capability Negotiation 1351 [RFC5939] defines a general SDP Capability Negotiation framework. It 1352 also specifies how to provide attributes and transport protocols as 1353 capabilities and negotiate them using the framework. Extensions for 1354 other types of capabilities (e.g., media types and media formats) may 1355 be provided in other documents. 1357 +---------+-----------------------+-------+--------------+ 1358 | Name | Notes | Level | Mux Category | 1359 +---------+-----------------------+-------+--------------+ 1360 | pcfg | Refer to Section 14 | M | SPECIAL | 1361 | | | | | 1362 | acfg | Refer to Section 14 | M | SPECIAL | 1363 | | | | | 1364 | csup | Not Impacted | B | NORMAL | 1365 | | | | | 1366 | creq | Not Impacted | B | NORMAL | 1367 | | | | | 1368 | acap | Refer to Section 14 | B | INHERIT | 1369 | | | | | 1370 | tcap | Refer to Section 14 | B | INHERIT | 1371 | | | | | 1372 | cap-v0 | Not Impacted | B | NORMAL | 1373 | | | | | 1374 +---------+-----------------------+-------+--------------+ 1376 RFC5939 Attribute Analysis 1378 5.33. RFC6871: SDP Media Capabilities Negotiation 1380 SDP capability negotiation provides a general framework for 1381 indicating and negotiating capabilities in SDP. The base framework 1382 defines only capabilities for negotiating transport protocols and 1383 attributes. [RFC6871] extends the framework by defining media 1384 capabilities that can be used to negotiate media types and their 1385 associated parameters. 1387 +---------+-----------------------+-------+-------------------+ 1388 | Name | Notes | Level | Mux Category | 1389 +---------+-----------------------+-------+-------------------+ 1390 | rmcap | Refer to Section 14 | B | IDENTICAL-PER-PT | 1391 | | | | | 1392 | omcap | Not Impacted | B | NORMAL | 1393 | | | | | 1394 | mfcap | Refer to Section 14 | B | IDENTICAL-PER-PT | 1395 | | | | | 1396 | mscap | Refer to Section 14 | B | INHERIT | 1397 | | | | | 1398 | lcfg | Refer to Section 14 | B | SPECIAL | 1399 | | | | | 1400 | sescap | Refer to notes below | S | NOT RECOMMENDED | 1401 | | | | | 1402 | med-v0 | Not Impacted | S | NORMAL | 1403 | | | | | 1404 +---------+-----------------------+-------+-------------------+ 1406 RFC6871 - Attribute Analysis 1408 NOTE: The "sescap" attribute is NOT RECOMMENDED for use with 1409 multiplexing. The reason is that it requires the use of unique 1410 configuration numbers across the entire SDP (per [RFC6871]) as 1411 opposed to within a media description only (per [RFC5939]). As 1412 described in Section 14, the use of identical configuration numbers 1413 between multiplexed (bundled) media descriptions is the default way 1414 of indicating compatible configurations in a bundle. 1416 5.34. RFC7006: Miscellaneous Capabilities Negotiation SDP 1418 [RFC7006] extends the SDP capability negotiation framework to allow 1419 endpoints to negotiate three additional SDP capabilities. In 1420 particular, this memo provides a mechanism to negotiate bandwidth 1421 ("b=" line), connection data ("c=" line), and session or media titles 1422 ("i=" line for each session or media). 1424 +----------+-----------------------------------+-------+------------+ 1425 | Name | Notes | Level | Mux | 1426 | | | | Category | 1427 +----------+-----------------------------------+-------+------------+ 1428 | bcap | Inherit the category SUM as | B | INHERIT | 1429 | | applicable to b= attribute | | | 1430 | | | | | 1431 | bcap-v0 | Not Impacted | B | NORMAL | 1432 | | | | | 1433 | ccap | The connection address type MUST | B | IDENTICAL | 1434 | | be identical across all the | | | 1435 | | multiplexed "m=" lines | | | 1436 | | | | | 1437 | ccap-v0 | Not Impacted | B | NORMAL | 1438 | | | | | 1439 | icap | Not Impacted | B | NORMAL | 1440 | | | | | 1441 | icap-v0 | Not Impacted | B | NORMAL | 1442 | | | | | 1443 +----------+-----------------------------------+-------+------------+ 1445 RFC7006 - Attribute Analysis 1447 5.35. RFC4567: Key Management Extensions for SDP and RTSP 1449 [RFC4567] defines general extensions for SDP and Real Time Streaming 1450 Protocol (RTSP) to carry messages, as specified by a key management 1451 protocol, in order to secure the media. These extensions are 1452 presented as a framework, to be used by one or more key management 1453 protocols. As such, their use is meaningful only when complemented 1454 by an appropriate key management protocol. 1456 +-----------+----------------------------------+-------+------------+ 1457 | Name | Notes | Level | Mux | 1458 | | | | Category | 1459 +-----------+----------------------------------+-------+------------+ 1460 | key-mgmt | Key management protocol MUST be | B | IDENTICAL | 1461 | | identical across all the "m=" | | | 1462 | | lines | | | 1463 | | | | | 1464 | mikey | Key management protocol MUST be | B | IDENTICAL | 1465 | | identical across all the "m=" | | | 1466 | | lines | | | 1467 | | | | | 1468 +-----------+----------------------------------+-------+------------+ 1470 RFC4567 Attribute Analysis 1472 5.36. RFC4572: Comedia over TLS in SDP 1474 [RFC4572] specifies how to establish secure connection-oriented media 1475 transport sessions over the Transport Layer Security (TLS) protocol 1476 using SDP. It defines a new SDP protocol identifier, 'TCP/TLS'. It 1477 also defines the syntax and semantics for an SDP 'fingerprint' 1478 attribute that identifies the certificate that will be presented for 1479 the TLS session. This mechanism allows media transport over TLS 1480 connections to be established securely, so long as the integrity of 1481 session descriptions is assured. 1483 +--------------+-------------------------------+-------+------------+ 1484 | Name | Notes | Level | Mux | 1485 | | | | Category | 1486 +--------------+-------------------------------+-------+------------+ 1487 | fingerprint | fingerprint value from the | B | TRANSPORT | 1488 | | "m=" line defining the | | | 1489 | | underlying transport is | | | 1490 | | chosen | | | 1491 | | | | | 1492 +--------------+-------------------------------+-------+------------+ 1494 RFC4572 Attribute Analysis 1496 5.37. RFC4570: SDP Source Filters 1498 [RFC4570] describes how to adapt SDP to express one or more source 1499 addresses as a source filter for one or more destination "connection" 1500 addresses. It defines the syntax and semantics for an SDP "source- 1501 filter" attribute that may reference either IPv4 or IPv6 address(es) 1502 as either an inclusive or exclusive source list for either multicast 1503 or unicast destinations. In particular, an inclusive source-filter 1504 can be used to specify a Source-Specific Multicast (SSM) session. 1506 +----------------+-----------------------------+-------+------------+ 1507 | Name | Notes | Level | Mux | 1508 | | | | Category | 1509 +----------------+-----------------------------+-------+------------+ 1510 | source-filter | The attribute MUST be | B | IDENTICAL | 1511 | | repeated across all "m=" | | | 1512 | | lines multiplexed | | | 1513 | | | | | 1514 +----------------+-----------------------------+-------+------------+ 1516 RFC4570 Attribute Analysis 1518 5.38. RFC6128: RTCP Port for Multicast Sessions 1520 SDP has an attribute that allows RTP applications to specify an 1521 address and a port associated with the RTCP traffic. In RTP-based 1522 source-specific multicast (SSM) sessions, the same attribute is used 1523 to designate the address and the RTCP port of the Feedback Target in 1524 the SDP description. However, the RTCP port associated with the SSM 1525 session itself cannot be specified by the same attribute to avoid 1526 ambiguity, and thus, is required to be derived from the "m=" line of 1527 the media description. Deriving the RTCP port from the "m=" line 1528 imposes an unnecessary restriction. [RFC6128] removes this 1529 restriction by introducing a new SDP attribute. 1531 +-----------------+----------------------------+-------+------------+ 1532 | Name | Notes | Level | Mux | 1533 | | | | Category | 1534 +-----------------+----------------------------+-------+------------+ 1535 | multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL | 1536 | | be identical across all | | | 1537 | | the "m=" lines | | | 1538 | | | | | 1539 +-----------------+----------------------------+-------+------------+ 1541 RFC6128 Attribute Analysis 1543 5.39. RFC6189: ZRTP 1545 [RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman 1546 exchange to agree on a session key and parameters for establishing 1547 unicast SRTP sessions for (VoIP applications. 1549 +------------+---------------------------------+-------+------------+ 1550 | Name | Notes | Level | Mux | 1551 | | | | Category | 1552 +------------+---------------------------------+-------+------------+ 1553 | zrtp-hash | zrtp-hash attribute MUST be the | M | TRANSPORT | 1554 | | one that corresponds to the | | | 1555 | | "m=" line chosen for setting up | | | 1556 | | the underlying transport flow | | | 1557 | | | | | 1558 +------------+---------------------------------+-------+------------+ 1560 RFC6189 Attribute Analysis 1562 5.40. RFC4145: Connection-Oriented Media 1564 [RFC4145] describes how to express media transport over TCP using 1565 SDP. It defines the SDP 'TCP' protocol identifier, the SDP 'setup' 1566 attribute, which describes the connection setup procedure, and the 1567 SDP 'connection' attribute, which handles connection reestablishment. 1569 +-------------+--------------------------------+-------+------------+ 1570 | Name | Notes | Level | Mux | 1571 | | | | Category | 1572 +-------------+--------------------------------+-------+------------+ 1573 | setup | The attribute MUST be | B | IDENTICAL | 1574 | | identical across all "m=" | | | 1575 | | lines | | | 1576 | | | | | 1577 | connection | Thee attribute MUST be | B | IDENTICAL | 1578 | | identical across all "m=" | | | 1579 | | lines | | | 1580 | | | | | 1581 +-------------+--------------------------------+-------+------------+ 1583 RFC4145 Attribute Analysis 1585 5.41. RFC6947: The SDP altc Attribute 1587 [RFC6947] proposes a mechanism that allows the same SDP offer to 1588 carry multiple IP addresses of different address families (e.g., IPv4 1589 and IPv6). The proposed attribute, the "altc" attribute, solves the 1590 backward-compatibility problem that plagued Alternative Network 1591 Address Types (ANAT) due to their syntax. 1593 +-------+--------------------------------------+-------+------------+ 1594 | Name | Notes | Level | Mux | 1595 | | | | Category | 1596 +-------+--------------------------------------+-------+------------+ 1597 | altc | The IP Address and port MUST be the | M | TRANSPORT | 1598 | | one that corresponds to the "m=" | | | 1599 | | line chosen for setting up the | | | 1600 | | underlying transport flow | | | 1601 | | | | | 1602 +-------+--------------------------------------+-------+------------+ 1604 RFC6947 Attribute Analysis 1606 5.42. RFC7195: SDP Extension for Circuit Switched Bearers in PSTN 1608 [RFC7195] describes use cases, requirements, and protocol extensions 1609 for using SDP offer/answer model for establishing audio and video 1610 media streams over circuit-switched bearers in the Public Switched 1611 Telephone Network (PSTN). 1613 +--------------------------+-------------------+-------+------------+ 1614 | Name | Notes | Level | Mux | 1615 | | | | Category | 1616 +--------------------------+-------------------+-------+------------+ 1617 | cs-correlation:callerid | Refer to notes | M | TBD | 1618 | | below | | | 1619 | | | | | 1620 | cs-correlation:uuie | Refer to notes | M | TBD | 1621 | | below | | | 1622 | | | | | 1623 | cs-correlation:dtmf | Refer to notes | M | TBD | 1624 | | below | | | 1625 | | | | | 1626 | cs-correlation:external | Refer to notes | M | TBD | 1627 | | below | | | 1628 | | | | | 1629 +--------------------------+-------------------+-------+------------+ 1631 RFC7195 Attribute Analysis 1633 NOTE: [RFC7195] defines SDP attributes for establishing audio and 1634 video media streams over circuit-switched bearers by defining a new 1635 nettype value "PSTN". However, section 7.2 of 1636 [I-D.ietf-mmusic-sdp-bundle-negotiation] requires the "c=" line 1637 nettype value of "IN". If in future there exists a specification 1638 that defines procedures to multiplex media streams over nettype 1639 "PSTN", the multiplexing categories for attributes in this section 1640 MUST be revisited. 1642 5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP) 1644 [RFC7272] defines a new RTCP Packet Type and an RTCP Extended Report 1645 (XR) Block Type to be used for achieving Inter-Destination Media 1646 Synchronization (IDMS). 1648 +------------+---------------+-------+--------------+ 1649 | Name | Notes | Level | Mux Category | 1650 +------------+---------------+-------+--------------+ 1651 | rtcp-idms | Not Impacted | M | NORMAL | 1652 | | | | | 1653 +------------+---------------+-------+--------------+ 1655 RFC7272 Attribute Analysis 1657 5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP 1658 Attributes 1660 [RFC5159] provides descriptions of SDP attributes used by the Open 1661 Mobile Alliance's Broadcast Service and Content Protection 1662 specification. 1664 +---------------------+-----------------------+-------+-------------+ 1665 | Name | Notes | Level | Mux | 1666 | | | | Category | 1667 +---------------------+-----------------------+-------+-------------+ 1668 | bcastversion | Not Impacted | S | NORMAL | 1669 | | | | | 1670 | stkmstream | Not Impacted | B | NORMAL | 1671 | | | | | 1672 | SRTPAuthentication | Needs further | M | TBD | 1673 | | analysis | | | 1674 | | | | | 1675 | SRTPROCTxRate | Needs further | M | TBD | 1676 | | analysis | | | 1677 | | | | | 1678 +---------------------+-----------------------+-------+-------------+ 1680 RFC5159 Attribute Analysis 1682 5.45. RFC6193: Media Description for IKE in SDP 1684 [RFC6193] specifies how to establish a media session that represents 1685 a virtual private network using the Session Initiation Protocol for 1686 the purpose of on-demand media/application sharing between peers. It 1687 extends the protocol identifier of SDP so that it can negotiate use 1688 of the Internet Key Exchange Protocol (IKE) for media sessions in the 1689 SDP offer/answer model. 1691 +-------------------+--------------------------+-------+------------+ 1692 | Name | Notes | Level | Mux | 1693 | | | | Category | 1694 +-------------------+--------------------------+-------+------------+ 1695 | ike-setup | Attribute MUST be | B | IDENTICAL | 1696 | | identical across all the | | | 1697 | | "m=" lines | | | 1698 | | | | | 1699 | psk-fingerprint | Attribute MUST be | B | IDENTICAL | 1700 | | identical across all the | | | 1701 | | "m=" lines | | | 1702 | | | | | 1703 | ike-esp | Attribute MUST be | B | IDENTICAL | 1704 | | identical across all the | | | 1705 | | "m=" lines | | | 1706 | | | | | 1707 | ike-esp-udpencap | Attribute MUST be | B | IDENTICAL | 1708 | | identical across all the | | | 1709 | | "m=" lines | | | 1710 | | | | | 1711 +-------------------+--------------------------+-------+------------+ 1713 RFC6193 Attribute Analysis 1715 NOTE: With the above SDP constraints, a session multiplexed with 1716 multiple "m=" lines will use only one IPSec association for all of 1717 the "m=" lines. 1719 5.46. RFC2326: Real Time Streaming Protocol 1721 The Real Time Streaming Protocol, or RTSP, is an application-level 1722 protocol for control over the delivery of data with real-time 1723 properties. RTSP provides an extensible framework to enable 1724 controlled, on-demand delivery of real-time data, such as audio and 1725 video. 1727 +----------+---------------------------------+-------+--------------+ 1728 | Name | Notes | Level | Mux Category | 1729 +----------+---------------------------------+-------+--------------+ 1730 | etag | RTSP is not supported for RTP | B | NOT | 1731 | | Stream multiplexing | | RECOMMENDED | 1732 | | | | | 1733 | range | RTSP is not supported for RTP | B | NOT | 1734 | | Stream multiplexing | | RECOMMENDED | 1735 | | | | | 1736 | control | RTSP is not supported for RTP | B | NOT | 1737 | | Stream multiplexing | | RECOMMENDED | 1738 | | | | | 1739 | mtag | RTSP is not supported for RTP | B | NOT | 1740 | | Stream multiplexing | | RECOMMENDED | 1741 | | | | | 1742 +----------+---------------------------------+-------+--------------+ 1744 RFC2326 Attribute Analysis 1746 NOTE: [RFC2326] defines SDP attributes that are applicable in the 1747 declarative usage of SDP alone. For purposes of this document, only 1748 the Offer/Answer usage of SDP is considered as mandated by 1749 [I-D.ietf-mmusic-sdp-bundle-negotiation]. 1751 5.47. RFC6064: SDP and RTSP Extensions for 3GPP 1753 The Packet-switched Streaming Service (PSS) and the Multimedia 1754 Broadcast/Multicast Service (MBMS) defined by 3GPP use SDP and RTSP 1755 with some extensions. [RFC6064] provides information about these 1756 extensions and registers the RTSP and SDP extensions with IANA. 1758 +-------------------------------+------------+-------+--------------+ 1759 | Name | Notes | Level | Mux Category | 1760 +-------------------------------+------------+-------+--------------+ 1761 | X-predecbufsize | Refer to | M | NOT | 1762 | | notes | | RECOMMENDED | 1763 | | below | | | 1764 | | | | | 1765 | X-initpredecbufperiod | Refer to | M | NOT | 1766 | | notes | | RECOMMENDED | 1767 | | below | | | 1768 | | | | | 1769 | X-initpostdecbufperiod | Refer to | M | NOT | 1770 | | notes | | RECOMMENDED | 1771 | | below | | | 1772 | | | | | 1773 | X-decbyterate | Refer to | M | NOT | 1774 | | notes | | RECOMMENDED | 1775 | | below | | | 1776 | | | | | 1777 | 3gpp-videopostdecbufsize | Refer to | M | NOT | 1778 | | notes | | RECOMMENDED | 1779 | | below | | | 1780 | | | | | 1781 | framesize | Refer to | M | NOT | 1782 | | notes | | RECOMMENDED | 1783 | | below | | | 1784 | | | | | 1785 | 3GPP-Integrity-Key | Refer to | S | NOT | 1786 | | notes | | RECOMMENDED | 1787 | | below | | | 1788 | | | | | 1789 | 3GPP-SDP-Auth | Refer to | S | NOT | 1790 | | notes | | RECOMMENDED | 1791 | | below | | | 1792 | | | | | 1793 | 3GPP-SRTP-Config | Refer to | M | NOT | 1794 | | notes | | RECOMMENDED | 1795 | | below | | | 1796 | | | | | 1797 | alt | Refer to | M | NOT | 1798 | | notes | | RECOMMENDED | 1799 | | below | | | 1800 | | | | | 1801 | alt-default-id | Refer to | M | NOT | 1802 | | notes | | RECOMMENDED | 1803 | | below | | | 1804 | | | | | 1805 | alt-group | Refer to | S | NOT | 1806 | | notes | | RECOMMENDED | 1807 | | below | | | 1808 | | | | | 1809 | 3GPP-Adaptation-Support | Refer to | M | NOT | 1810 | | notes | | RECOMMENDED | 1811 | | below | | | 1812 | | | | | 1813 | 3GPP-Asset-Information | Refer to | B | NOT | 1814 | | notes | | RECOMMENDED | 1815 | | below | | | 1816 | | | | | 1817 | mbms-mode | Refer to | B | NOT | 1818 | | notes | | RECOMMENDED | 1819 | | below | | | 1820 | | | | | 1821 | mbms-flowid | Refer to | M | NOT | 1822 | | notes | | RECOMMENDED | 1823 | | below | | | 1824 | | | | | 1825 | mbms-repair | Refer to | B | NOT | 1826 | | notes | | RECOMMENDED | 1827 | | below | | | 1828 | | | | | 1829 | 3GPP-QoE-Metrics | Refer to | M | NOT | 1830 | | notes | | RECOMMENDED | 1831 | | below | | | 1832 | | | | | 1833 | 3GPP-QoE-Metrics:Corruption | Refer to | M | NOT | 1834 | duration | notes | | RECOMMENDED | 1835 | | below | | | 1836 | | | | | 1837 | 3GPP-QoE-Metrics:Rebuffering | Refer to | M | NOT | 1838 | duration | notes | | RECOMMENDED | 1839 | | below | | | 1840 | | | | | 1841 | 3GPP-QoE-Metrics:Initial | Refer to | M | NOT | 1842 | buffering duration | notes | | RECOMMENDED | 1843 | | below | | | 1844 | | | | | 1845 | 3GPP-QoE-Metrics:Successive | Refer to | M | NOT | 1846 | loss of RTP packets | notes | | RECOMMENDED | 1847 | | below | | | 1848 | | | | | 1849 | 3GPP-QoE-Metrics:Frame rate | Refer to | M | NOT | 1850 | deviation | notes | | RECOMMENDED | 1851 | | below | | | 1852 | | | | | 1853 | 3GPP-QoE-Metrics:Jitter | Refer to | M | NOT | 1854 | duration | notes | | RECOMMENDED | 1855 | | below | | | 1856 | | | | | 1857 | 3GPP-QoE-Metrics:Content | Refer to | B | NOT | 1858 | Switch Time | notes | | RECOMMENDED | 1859 | | below | | | 1860 | | | | | 1861 | 3GPP-QoE-Metrics:Average | Refer to | M | NOT | 1862 | Codec Bitrate | notes | | RECOMMENDED | 1863 | | below | | | 1864 | | | | | 1865 | 3GPP-QoE-Metrics:Codec | Refer to | M | NOT | 1866 | Information | notes | | RECOMMENDED | 1867 | | below | | | 1868 | | | | | 1869 | 3GPP-QoE-Metrics:Buffer | Refer to | M | NOT | 1870 | Status | notes | | RECOMMENDED | 1871 | | below | | | 1872 | | | | | 1873 +-------------------------------+------------+-------+--------------+ 1875 RFC6064 Attribute Analysis 1877 NOTE: [RFC6064] defines SDP attributes that are applicable in the 1878 declarative usage of SDP alone. For purposes of this document, only 1879 the Offer/Answer usage of SDP is considered as mandated by 1880 [I-D.ietf-mmusic-sdp-bundle-negotiation]. 1882 5.48. RFC3108: ATM SDP 1884 [RFC3108] describes conventions for using SDP described for 1885 controlling ATM Bearer Connections, and any associated ATM Adaptation 1886 Layer (AAL). 1888 +------------------------+------------------+-------+---------------+ 1889 | Name | Notes | Level | Mux Category | 1890 +------------------------+------------------+-------+---------------+ 1891 | aalType | Refer to notes | B | NOT | 1892 | | below | | RECOMMENDED | 1893 | eecid | Refer to notes | B | NOT | 1894 | | below | | RECOMMENDED | 1895 | capability | Refer to notes | B | NOT | 1896 | | below | | RECOMMENDED | 1897 | qosClass | Refer to notes | B | NOT | 1898 | | below | | RECOMMENDED | 1899 | bcob | Refer to notes | B | NOT | 1900 | | below | | RECOMMENDED | 1901 | stc | Refer to notes | B | NOT | 1902 | | below | | RECOMMENDED | 1903 | upcc | Refer to notes | B | NOT | 1904 | | below | | RECOMMENDED | 1905 | atmQOSparms | Refer to notes | B | NOT | 1906 | | below | | RECOMMENDED | 1907 | atmTrfcDesc | Refer to notes | B | NOT | 1908 | | below | | RECOMMENDED | 1909 | abrParms | Refer to notes | B | NOT | 1910 | | below | | RECOMMENDED | 1911 | abrSetup | Refer to notes | B | NOT | 1912 | | below | | RECOMMENDED | 1913 | bearerType | Refer to notes | B | NOT | 1914 | | below | | RECOMMENDED | 1915 | lij | Refer to notes | B | NOT | 1916 | | below | | RECOMMENDED | 1917 | anycast | Refer to notes | B | NOT | 1918 | | below | | RECOMMENDED | 1919 | cache | Refer to notes | B | NOT | 1920 | | below | | RECOMMENDED | 1921 | bearerSigIE | Refer to notes | B | NOT | 1922 | | below | | RECOMMENDED | 1923 | aalApp | Refer to notes | B | NOT | 1924 | | below | | RECOMMENDED | 1925 | cbrRate | Refer to notes | B | NOT | 1926 | | below | | RECOMMENDED | 1927 | sbc | Refer to notes | B | NOT | 1928 | | below | | RECOMMENDED | 1929 | clkrec | Refer to notes | B | NOT | 1930 | | below | | RECOMMENDED | 1931 | fec | Refer to notes | B | NOT | 1932 | | below | | RECOMMENDED | 1933 | prtfl | Refer to notes | B | NOT | 1934 | | below | | RECOMMENDED | 1935 | structure | Refer to notes | B | NOT | 1936 | | below | | RECOMMENDED | 1937 | cpsSDUsize | Refer to notes | B | NOT | 1938 | | below | | RECOMMENDED | 1939 | aal2CPS | Refer to notes | B | NOT | 1940 | | below | | RECOMMENDED | 1941 | aal2CPSSDUrate | Refer to notes | B | NOT | 1942 | | below | | RECOMMENDED | 1943 | aal2sscs3661unassured | Refer to notes | B | NOT | 1944 | | below | | RECOMMENDED | 1945 | aal2sscs3661assured | Refer to notes | B | NOT | 1946 | | below | | RECOMMENDED | 1947 | aal2sscs3662 | Refer to notes | B | NOT | 1948 | | below | | RECOMMENDED | 1949 | aal5sscop | Refer to notes | B | NOT | 1950 | | below | | RECOMMENDED | 1951 | atmmap | Refer to notes | B | NOT | 1952 | | below | | RECOMMENDED | 1953 | silenceSupp | Refer to notes | B | NOT | 1954 | | below | | RECOMMENDED | 1955 | ecan | Refer to notes | B | NOT | 1956 | | below | | RECOMMENDED | 1957 | gc | Refer to notes | B | NOT | 1958 | | below | | RECOMMENDED | 1959 | profileDesc | Refer to notes | B | NOT | 1960 | | below | | RECOMMENDED | 1961 | vsel | Refer to notes | B | NOT | 1962 | | below | | RECOMMENDED | 1963 | dsel | Refer to notes | B | NOT | 1964 | | below | | RECOMMENDED | 1965 | fsel | Refer to notes | B | NOT | 1966 | | below | | RECOMMENDED | 1967 | onewaySel | Refer to notes | B | NOT | 1968 | | below | | RECOMMENDED | 1969 | codecconfig | Refer to notes | B | NOT | 1970 | | below | | RECOMMENDED | 1971 | isup_usi | Refer to notes | B | NOT | 1972 | | below | | RECOMMENDED | 1973 | uiLayer1_Prot | Refer to notes | B | NOT | 1974 | | below | | RECOMMENDED | 1975 | chain | Refer to notes | B | NOT | 1976 | | below | | RECOMMENDED | 1977 | | | | | 1978 +------------------------+------------------+-------+---------------+ 1980 RFC3108 Attribute Analysis 1982 NOTE: RFC3108 describes conventions for using SDP for characterizing 1983 ATM bearer connections using an AAL1, AAL2 or AAL5 adaptation layers. 1984 For AAL1, AAL2 and AAL5, bearer connections can be used to transport 1985 single media streams. In addition, for AAL1 and AAL2, multiple media 1986 streams can be multiplexed into a bearer connection. For all 1987 adaptation types (AAL1, AAL2 and AAL5), bearer connections can be 1988 bundled into a single media group. In all cases addressed by 1989 RFC3108, a real-time media stream (voice, video, voiceband data, 1990 pseudo-wire, and others) or a multiplex of media streams is mapped 1991 directly into an ATM connection. RFC3108 does not address cases 1992 where ATM serves as a low-level transport pipe for IP packets which 1993 in turn can carry one or more real-time (e.g. VoIP) media sessions 1994 with a life-cycle different from that of the underlying ATM 1995 transport. 1997 5.49. 3GPP TS 26.114 1999 [R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and 2000 interaction 2002 +----------------------+-------------------------+-------+----------+ 2003 | Name | Notes | Level | Mux | 2004 | | | | Category | 2005 +----------------------+-------------------------+-------+----------+ 2006 | 3gpp_sync_info | Usage defined for the | M | NORMAL | 2007 | | IP Multimedia Subsystem | | | 2008 | | | | | 2009 | 3gpp_MaxRecvSDUSize | Usage defined for the | M | NORMAL | 2010 | | IP Multimedia Subsystem | | | 2011 | | | | | 2012 +----------------------+-------------------------+-------+----------+ 2014 3GPP TS 26.114 Attribute Analysis 2016 5.50. 3GPP TS 183.063 2018 [R3GPPTS183.063] Telecommunications and Internet converged Services 2019 and Protocols for Advanced Networking (TISPAN); 2021 +---------------------+---------------+-------+--------------+ 2022 | Name | Notes | Level | Mux Category | 2023 +---------------------+---------------+-------+--------------+ 2024 | PSCid | Not Impacted | S | NORMAL | 2025 | | | | | 2026 | bc_service | Not Impacted | S | NORMAL | 2027 | | | | | 2028 | bc_program | Not Impacted | S | NORMAL | 2029 | | | | | 2030 | bc_service_package | Not Impacted | S | NORMAL | 2031 | | | | | 2032 +---------------------+---------------+-------+--------------+ 2034 3GPP TS 183.063 Attribute Analysis 2036 5.51. 3GPP TS 24.182 2038 [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting 2039 tones 2041 +-------------+---------------------------------+-------+-----------+ 2042 | Name | Notes | Level | Mux | 2043 | | | | Category | 2044 +-------------+---------------------------------+-------+-----------+ 2045 | g.3gpp.cat | Usage defined for the IP | M | NORMAL | 2046 | | Multimedia Subsystem | | | 2047 | | | | | 2048 +-------------+---------------------------------+-------+-----------+ 2050 3GPP TS 24.182 Attribute Analysis 2052 5.52. 3GPP TS 24.183 2054 [R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing 2055 Signal 2056 +-------------+---------------------------------+-------+-----------+ 2057 | Name | Notes | Level | Mux | 2058 | | | | Category | 2059 +-------------+---------------------------------+-------+-----------+ 2060 | g.3gpp.crs | Usage defined for the IP | M | NORMAL | 2061 | | Multimedia Subsystem | | | 2062 | | | | | 2063 +-------------+---------------------------------+-------+-----------+ 2065 3GPP TS 24.183 Attribute Analysis 2067 5.53. 3GPP TS 24.229 2069 [R3GPPTS24.229] specifies IP multimedia call control protocol based 2070 on Session Initial protocol and Session Description Protocol. 2072 +------------------+---------------------------+-------+------------+ 2073 | Name | Notes | Level | Mux | 2074 | | | | Category | 2075 +------------------+---------------------------+-------+------------+ 2076 | secondary-realm | secondary-realm MUST be | M | TRANSPORT | 2077 | | the one that corresponds | | | 2078 | | to the "m=" line chosen | | | 2079 | | for setting up the | | | 2080 | | underlying transport flow | | | 2081 | | | | | 2082 | visited-realm | visited-realm MUST be the | M | TRANSPORT | 2083 | | one that corresponds to | | | 2084 | | the "m=" line chosen for | | | 2085 | | setting up the underlying | | | 2086 | | transport flow | | | 2087 | | | | | 2088 | omr-m-cksum | Not Impacted | M | NORMAL | 2089 | | | | | 2090 | omr-s-cksum | Not Impacted | M | NORMAL | 2091 | | | | | 2092 | omr-m-att | Not Impacted | M | NORMAL | 2093 | | | | | 2094 | omr-s-att | Not Impacted | M | NORMAL | 2095 | | | | | 2096 | omr-m-bw | Not Impacted | M | NORMAL | 2097 | | | | | 2098 | omr-s-bw | Not Impacted | M | NORMAL | 2099 | | | | | 2100 | omr-codecs | Not Impacted | M | NORMAL | 2101 | | | | | 2102 +------------------+---------------------------+-------+------------+ 2104 3GPP TS 24.229 Attribute Analysis 2106 5.54. ITU T.38 2108 [T.38] defines procedures for real-time Group 3 facsimile 2109 communications over IP networks. 2111 +------------------------+--------------------+-------+-------------+ 2112 | Name | Notes | Level | Mux | 2113 | | | | Category | 2114 +------------------------+--------------------+-------+-------------+ 2115 | T38FaxVersion | Refer to notes | M | TBD | 2116 | | below | | | 2117 | | | | | 2118 | T38MaxBitRate | Refer to notes | M | TBD | 2119 | | below | | | 2120 | | | | | 2121 | T38FaxFillBitRemoval | Refer to notes | M | TBD | 2122 | | below | | | 2123 | | | | | 2124 | T38FaxTranscodingMMR | Refer to notes | M | TBD | 2125 | | below | | | 2126 | | | | | 2127 | T38FaxTranscodingJBIG | Refer to notes | M | TBD | 2128 | | below | | | 2129 | | | | | 2130 | T38FaxRateManagement | Refer to notes | M | TBD | 2131 | | below | | | 2132 | | | | | 2133 | T38FaxMaxBuffer | Refer to notes | M | TBD | 2134 | | below | | | 2135 | | | | | 2136 | T38FaxMaxDatagram | Refer to notes | M | TBD | 2137 | | below | | | 2138 | | | | | 2139 | T38FaxUdpEC | Refer to notes | M | TBD | 2140 | | below | | | 2141 | | | | | 2142 | T38FaxMaxIFP | Refer to notes | M | TBD | 2143 | | below | | | 2144 | | | | | 2145 | T38FaxUdpECDepth | Refer to notes | M | TBD | 2146 | | below | | | 2147 | | | | | 2148 | T38FaxUdpFECMaxSpan | Refer to notes | M | TBD | 2149 | | below | | | 2150 | | | | | 2151 | T38ModemType | Refer to notes | M | TBD | 2152 | | below | | | 2153 | | | | | 2154 | T38VendorInfo | Refer to notes | M | TBD | 2155 | | below | | | 2156 | | | | | 2157 +------------------------+--------------------+-------+-------------+ 2159 ITU T.38 Attribute Analysis 2161 NOTE: As per section 9.1 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 2162 there exists no publicly available specification that defines 2163 procedures for multiplexing/demultiplexing fax protocols flows over a 2164 single 5-tuple. Once such a specification is available, the 2165 multiplexing category assignments for the attributes in this section 2166 MUST be revisited. 2168 5.55. ITU-T Q.1970 2170 [Q.1970] defines Bearer Independent Call Control (BICC) IP bearer 2171 control protocol. 2173 +--------+---------------------------------------+-------+----------+ 2174 | Name | Notes | Level | Mux | 2175 | | | | Category | 2176 +--------+---------------------------------------+-------+----------+ 2177 | ipbcp | ipbcp version identifies type of IP | S | SPECIAL | 2178 | | bearer control protocol (IPBCP) | | | 2179 | | message used in BICC (ITU-T Q.1901) | | | 2180 | | environment which are limited to | | | 2181 | | single media payload. Pertinent ITU-T | | | 2182 | | specifications needs to be referred | | | 2183 | | while multiplexing | | | 2184 | | | | | 2185 +--------+---------------------------------------+-------+----------+ 2187 ITU-T Q.1970 Attribute Analysis 2189 5.56. ITU-T H.248.15 2191 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248 2192 package attribute 2193 +-----------+------------------------------------+-------+----------+ 2194 | Name | Notes | Level | Mux | 2195 | | | | Category | 2196 +-----------+------------------------------------+-------+----------+ 2197 | h248item | It is only applicable for | B | SPECIAL | 2198 | | signaling the inclusion of H.248 | | | 2199 | | extension packages to a gateway | | | 2200 | | via the local and remote | | | 2201 | | descriptors. The attribute itself | | | 2202 | | is unaffected by multiplexing, but | | | 2203 | | the packaged referenced in a | | | 2204 | | specific use of the attribute can | | | 2205 | | be impacted. Further analysis of | | | 2206 | | each package is needed to | | | 2207 | | determine if there is an issue. | | | 2208 | | This is only a concern in | | | 2209 | | environments using a decomposed | | | 2210 | | server/gateway with H.248 signaled | | | 2211 | | between them. The ITU-T will need | | | 2212 | | to do further analysis of various | | | 2213 | | packages when they specify how to | | | 2214 | | signal the use of multiplexing to | | | 2215 | | a gateway | | | 2216 | | | | | 2217 +-----------+------------------------------------+-------+----------+ 2219 ITU-T H.248.15 Attribute Analysis 2221 5.57. RFC4975: The Message Session Relay Protocol 2223 [RFC4975] the Message Session Relay Protocol, a protocol for 2224 transmitting a series of related instant messages in the context of a 2225 session. Message sessions are treated like any other media stream 2226 when set up via a rendezvous or session creation protocol such as the 2227 Session Initiation Protocol. 2229 +-----------------------+---------------------+-------+-------------+ 2230 | Name | Notes | Level | Mux | 2231 | | | | Category | 2232 +-----------------------+---------------------+-------+-------------+ 2233 | accept-types | Refer to notes | M | TBD | 2234 | | below | | | 2235 | | | | | 2236 | accept-wrapped-types | Refer to notes | M | TBD | 2237 | | below | | | 2238 | | | | | 2239 | max-size | Refer to notes | M | TBD | 2240 | | below | | | 2241 | | | | | 2242 | path | Refer to notes | M | TBD | 2243 | | below | | | 2244 | | | | | 2245 +-----------------------+---------------------+-------+-------------+ 2247 RFC4975 Attribute Analysis 2249 NOTE: As per section 9.1 of [I-D.ietf-mmusic-sdp-bundle-negotiation], 2250 there exists no publicly available specification that defines 2251 procedures for multiplexing/demultiplexing MRSP flows over a single 2252 5-tuple. Once such a specification is available, the multiplexing 2253 categories assignments for the attributes in this section MUST be 2254 revisited. 2256 5.58. Historical Attributes 2258 This section specifies analysis for the attributes that are included 2259 for historic usage alone by the [IANA]. 2261 +----------+----------------------+-------+------------------+ 2262 | Name | Notes | Level | Mux Category | 2263 +----------+----------------------+-------+------------------+ 2264 | rtpred1 | Historic attributes | M | NOT RECOMMENDED | 2265 | | | | | 2266 | rtpred2 | Historic attributes | M | NOT RECOMMENDED | 2267 | | | | | 2268 +----------+----------------------+-------+------------------+ 2270 Historical Attribute Analysis 2272 6. bwtype Attribute Analysis 2274 This section specifies handling of specific bandwidth attributes when 2275 used in multiplexing scenarios. 2277 6.1. RFC4566: SDP 2279 [RFC4566] defines SDP that is intended for describing multimedia 2280 sessions for the purposes of session announcement, session 2281 invitation, and other forms of multimedia session initiation. 2283 +------------+-----------------------------------+-------+----------+ 2284 | Name | Notes | Level | Mux | 2285 | | | | Category | 2286 +------------+-----------------------------------+-------+----------+ 2287 | bwtype:CT | Not Impacted | S | NORMAL | 2288 | | | | | 2289 | bwtype:AS | For the media level usage, the | B | SUM | 2290 | | aggregate of individual bandwidth | | | 2291 | | values is considered | | | 2292 | | | | | 2293 +------------+-----------------------------------+-------+----------+ 2295 RFC4566 bwtype Analysis 2297 6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth 2299 [RFC3556] defines an extension to SDP to specify two additional 2300 modifiers for the bandwidth attribute. These modifiers may be used 2301 to specify the bandwidth allowed for RTCP packets in a RTP session. 2303 +------------+-----------------------------------+-------+----------+ 2304 | Name | Notes | Level | Mux | 2305 | | | | Category | 2306 +------------+-----------------------------------+-------+----------+ 2307 | bwtype:RS | Session level usage represents | B | SUM | 2308 | | session aggregate and media level | | | 2309 | | usage indicates SUM of the | | | 2310 | | individual values while | | | 2311 | | multiplexing | | | 2312 | | | | | 2313 | bwtype:RR | Session level usage represents | B | SUM | 2314 | | session aggregate and media level | | | 2315 | | usage indicates SUM of the | | | 2316 | | individual values while | | | 2317 | | multiplexing | | | 2318 | | | | | 2319 +------------+-----------------------------------+-------+----------+ 2321 RFC3556 bwtype Analysis 2323 6.3. RFC3890: Bandwidth Modifier for SDP 2325 [RFC3890] defines SDP Transport Independent Application Specific 2326 Maximum (TIAS) bandwidth modifier that does not include transport 2327 overhead; instead an additional packet rate attribute is defined. 2328 The transport independent bit-rate value together with the maximum 2329 packet rate can then be used to calculate the real bit-rate over the 2330 transport actually used. 2332 +--------------+---------------------------------+-------+----------+ 2333 | Name | Notes | Level | Mux | 2334 | | | | Category | 2335 +--------------+---------------------------------+-------+----------+ 2336 | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL | 2337 | | clearly defined Offer/Answer | | | 2338 | | usage. | | | 2339 | | | | | 2340 | maxprate | The usage of TIAS and maxprate | B | SPECIAL | 2341 | | is not well defined under | | | 2342 | | multiplexing | | | 2343 | | | | | 2344 +--------------+---------------------------------+-------+----------+ 2346 RFC3890 bwtype Analysis 2348 NOTE: The intention of TIAS is that the media level bit-rate is 2349 multiplied with the known per-packet overhead for the selected 2350 transport and the maxprate value to determine the worst case bit-rate 2351 from the transport to more accurately capture the required usage. 2352 Summing TIAS values independently across "m=" lines and multiplying 2353 the computed sum with maxprate and the per-packet overhead would 2354 inflate the value significantly. Instead performing multiplication 2355 and adding the individual values is a more appropriate usage. 2357 7. rtcp-fb Attribute Analysis 2359 This section analyzes rtcp-fb SDP attributes. 2361 7.1. RFC4585: RTP/AVPF 2363 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that 2364 enables receivers to provide, statistically, more immediate feedback 2365 to the senders and thus allows for short-term adaptation and 2366 efficient feedback-based repair mechanisms to be implemented. 2368 +----------+----------------------------+-------+-------------------+ 2369 | Name | Notes | Level | Mux Category | 2370 +----------+----------------------------+-------+-------------------+ 2371 | ack rpsi | The attribute value MUST | M | IDENTICAL-PER-PT | 2372 | | be same for a given codec | | | 2373 | | configuration | | | 2374 | | | | | 2375 | ack app | Feedback parameters MUST | M | SPECIAL | 2376 | | be handled in the app | | | 2377 | | specific way when | | | 2378 | | multiplexed | | | 2379 | | | | | 2380 | nack | The attribute value MUST | M | IDENTICAL-PER-PT | 2381 | | be same for a given codec | | | 2382 | | configuration | | | 2383 | | | | | 2384 | nack pli | The attribute value MUST | M | IDENTICAL-PER-PT | 2385 | | be same for a given codec | | | 2386 | | configuration | | | 2387 | | | | | 2388 | nack sli | The attribute value MUST | M | IDENTICAL-PER-PT | 2389 | | be same for a given codec | | | 2390 | | configuration | | | 2391 | | | | | 2392 | nack | The attribute value MUST | M | IDENTICAL-PER-PT | 2393 | rpsi | be same for a given codec | | | 2394 | | configuration | | | 2395 | | | | | 2396 | nack app | Feedback parameters MUST | M | SPECIAL | 2397 | | be handled in the app | | | 2398 | | specific way when | | | 2399 | | multiplexed | | | 2400 | | | | | 2401 | trr-int | The attribute value MUST | M | IDENTICAL-PER-PT | 2402 | | be same for a given codec | | | 2403 | | configuration | | | 2404 | | | | | 2405 +----------+----------------------------+-------+-------------------+ 2407 RFC4585 Attribute Analysis 2409 7.2. RFC5104: Codec Control Messages in AVPF 2411 [RFC5104] specifies a few extensions to the messages defined in the 2412 Audio-Visual Profile with Feedback (AVPF). They are helpful 2413 primarily in conversational multimedia scenarios where centralized 2414 multipoint functionalities are in use. However, some are also usable 2415 in smaller multicast environments and point-to-point calls. 2417 +------+--------------------------------+-------+-------------------+ 2418 | Name | Notes | Level | Mux Category | 2419 +------+--------------------------------+-------+-------------------+ 2420 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2421 | | same for a given codec | | | 2422 | | configuration | | | 2423 | | | | | 2424 +------+--------------------------------+-------+-------------------+ 2426 RFC5104 Attribute Analysis 2428 7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP Sessions 2429 (RAMS) 2431 [RFC6285] describes a method using the existing RTP and RTCP 2432 machinery that reduces the acquisition delay. In this method, an 2433 auxiliary unicast RTP session carrying the Reference Information to 2434 the receiver precedes or accompanies the multicast stream. This 2435 unicast RTP flow can be transmitted at a faster than natural bitrate 2436 to further accelerate the acquisition. The motivating use case for 2437 this capability is multicast applications that carry real-time 2438 compressed audio and video. 2440 +-------+-------------------------------+-------+-------------------+ 2441 | Name | Notes | Level | Mux Category | 2442 +-------+-------------------------------+-------+-------------------+ 2443 | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | 2444 | rai | same for a given codec | | | 2445 | | configuration | | | 2446 | | | | | 2447 +-------+-------------------------------+-------+-------------------+ 2449 RFC6285 Attribute Analysis 2451 7.4. RFC6679: ECN for RTP over UDP/IP 2453 [RFC6679] specifies how Explicit Congestion Notification (ECN) can be 2454 used with the RTP running over UDP, using the RTCP as a feedback 2455 mechanism. It defines a new RTCP Extended Report (XR) block for 2456 periodic ECN feedback, a new RTCP transport feedback message for 2457 timely reporting of congestion events, and a STUN extension used in 2458 the optional initialization method using ICE. 2460 +------------------+---------------------------+-------+------------+ 2461 | Name | Notes | Level | Mux | 2462 | | | | Category | 2463 +------------------+---------------------------+-------+------------+ 2464 | ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL | 2465 | | the RTP session level | | | 2466 | | | | | 2467 | nack ecn | This attribute enables | M | IDENTICAL | 2468 | | ECN at the RTP session | | | 2469 | | level | | | 2470 | | | | | 2471 +------------------+---------------------------+-------+------------+ 2473 RFC6679 Attribute Analysis 2475 7.5. RFC6642: Third-Party Loss Report 2477 In a large RTP session using the RTCP feedback mechanism defined in 2478 [RFC4585], a feedback target may experience transient overload if 2479 some event causes a large number of receivers to send feedback at 2480 once. This overload is usually avoided by ensuring that feedback 2481 reports are forwarded to all receivers, allowing them to avoid 2482 sending duplicate feedback reports. However, there are cases where 2483 it is not recommended to forward feedback reports, and this may allow 2484 feedback implosion. [RFC6642] memo discusses these cases and defines 2485 a new RTCP Third-Party Loss Report that can be used to inform 2486 receivers that the feedback target is aware of some loss event, 2487 allowing them to suppress feedback. Associated SDP signaling is also 2488 defined. 2490 +--------+------------------------------+-------+-------------------+ 2491 | Name | Notes | Level | Mux Category | 2492 +--------+------------------------------+-------+-------------------+ 2493 | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | 2494 | tllei | same for a given codec | | | 2495 | | configuration | | | 2496 | | | | | 2497 | nack | The attribute value MUST be | M | IDENTICAL-PER-PT | 2498 | pslei | same for a given codec | | | 2499 | | configuration | | | 2500 | | | | | 2501 +--------+------------------------------+-------+-------------------+ 2503 RFC6642 Attribute Analysis 2505 7.6. RFC5104: Codec Control Messages in AVPF 2507 [RFC5104] specifies a few extensions to the messages defined in the 2508 Audio-Visual Profile with Feedback (AVPF). They are helpful 2509 primarily in conversational multimedia scenarios where centralized 2510 multipoint functionalities are in use. However, some are also usable 2511 in smaller multicast environments and point-to-point calls. 2513 +--------+------------------------------+-------+-------------------+ 2514 | Name | Notes | Level | Mux Category | 2515 +--------+------------------------------+-------+-------------------+ 2516 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2517 | fir | same for a given codec | | | 2518 | | configuration | | | 2519 | | | | | 2520 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2521 | tmmbr | same for a given codec | | | 2522 | | configuration | | | 2523 | | | | | 2524 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2525 | tstr | same for a given codec | | | 2526 | | configuration | | | 2527 | | | | | 2528 | ccm | The attribute value MUST be | M | IDENTICAL-PER-PT | 2529 | vbcm | same for a given codec | | | 2530 | | configuration | | | 2531 | | | | | 2532 +--------+------------------------------+-------+-------------------+ 2534 RFC5104 Attribute Analysis 2536 8. group Attribute Analysis 2538 This section analyzes SDP "group" attribute semantics [RFC5888]. 2540 8.1. RFC5888: SDP Grouping Framework 2542 [RFC5888] defines a framework to group "m" lines in SDP for different 2543 purposes. 2545 +------------+---------------+-------+--------------+ 2546 | Name | Notes | Level | Mux Category | 2547 +------------+---------------+-------+--------------+ 2548 | group:LS | Not Impacted | S | NORMAL | 2549 | | | | | 2550 | group:FID | Not Impacted | S | NORMAL | 2551 | | | | | 2552 +------------+---------------+-------+--------------+ 2554 RFC5888 Attribute Analysis 2556 8.2. RFC3524: Mapping Media Streams to Resource Reservation Flows 2558 [RFC3524] defines an extension to the SDP grouping framework. It 2559 allows requesting a group of media streams to be mapped into a single 2560 resource reservation flow. The SDP syntax needed is defined, as well 2561 as a new "semantics" attribute called Single Reservation Flow (SRF). 2563 +------------+---------------+-------+--------------+ 2564 | Name | Notes | Level | Mux Category | 2565 +------------+---------------+-------+--------------+ 2566 | group:SRF | Not Impacted | S | NORMAL | 2567 | | | | | 2568 +------------+---------------+-------+--------------+ 2570 RFC3524 Attribute Analysis 2572 8.3. RFC4091: ANAT Semantics 2574 [RFC4091] defines ANAT semantics for the SDP grouping framework. The 2575 ANAT semantics allow alternative types of network addresses to 2576 establish a particular media stream. 2578 +-------------+---------------------------+-------+-----------------+ 2579 | Name | Notes | Level | Mux Category | 2580 +-------------+---------------------------+-------+-----------------+ 2581 | group:ANAT | ANAT semantics is | S | NOT RECOMMENDED | 2582 | | obseleted | | | 2583 | | | | | 2584 +-------------+---------------------------+-------+-----------------+ 2586 RFC4091 Attribute Analysis 2588 8.4. RFC5956: FEC Grouping Semantics in SDP 2590 [RFC5956] defines the semantics for grouping the associated source 2591 and FEC-based (Forward Error Correction) repair flows in SDP. The 2592 semantics defined in the document are to be used with the SDP 2593 Grouping Framework [RFC5888]. These semantics allow the description 2594 of grouping relationships between the source and repair flows when 2595 one or more source and/or repair flows are associated in the same 2596 group, and they provide support for additive repair flows. SSRC- 2597 level (Synchronization Source) grouping semantics are also defined in 2598 this document for RTP streams using SSRC multiplexing. 2600 +---------------+---------------+-------+--------------+ 2601 | Name | Notes | Level | Mux Category | 2602 +---------------+---------------+-------+--------------+ 2603 | group:FEC-FR | Not Impacted | S | NORMAL | 2604 | | | | | 2605 +---------------+---------------+-------+--------------+ 2607 RFC5956 Attribute Analysis 2609 8.5. RFC5583: Signaling Media Decoding Dependency in SDP 2611 [RFC5583] defines semantics that allow for signaling the decoding 2612 dependency of different media descriptions with the same media type 2613 in SDP. This is required, for example, if media data is separated 2614 and transported in different network streams as a result of the use 2615 of a layered or multiple descriptive media coding process. 2617 +------------+--------------------------+-------+-------------------+ 2618 | Name | Notes | Level | Mux Category | 2619 +------------+--------------------------+-------+-------------------+ 2620 | group:DDP | Not Impacted | S | NORMAL | 2621 | | | | | 2622 | depend lay | The attribute value MUST | M | IDENTICAL-PER-PT | 2623 | | be same for a given | | | 2624 | | codec configuration | | | 2625 | | | | | 2626 | depend mdc | The attribute value MUST | M | IDENTICAL-PER-PT | 2627 | | be same for a given | | | 2628 | | codec configuration | | | 2629 | | | | | 2630 +------------+--------------------------+-------+-------------------+ 2632 RFC5583 Attribute Analysis 2634 8.6. RFC7104: Duplication Grouping Semantics in the SDP 2636 [RFC7104] defines the semantics for grouping redundant streams in 2637 SDP, The semantics defined in this document are to be used with the 2638 SDP Grouping Framework. Grouping semantics at the SSRC)level are 2639 also defined in this document for RTP streams using SSRC 2640 multiplexing. 2642 +------------+---------------+-------+--------------+ 2643 | Name | Notes | Level | Mux Category | 2644 +------------+---------------+-------+--------------+ 2645 | group:DUP | Not Impacted | S | NORMAL | 2646 | | | | | 2647 +------------+---------------+-------+--------------+ 2649 RFC7104 Attribute Analysis 2651 9. ssrc-group Attribute Analysis 2653 This section analyzes "ssrc-group" semantics. 2655 9.1. RFC5576: Source-Specific SDP Attributes 2657 [RFC5576] defines a mechanism to describe RTP media sources, which 2658 are identified by their synchronization source (SSRC) identifiers, in 2659 SDP, to associate attributes with these sources, and to express 2660 relationships among sources. It also defines several source-level 2661 attributes that can be used to describe properties of media sources. 2663 +--------------------+---------------+-------+--------------+ 2664 | Name | Notes | Level | Mux Category | 2665 +--------------------+---------------+-------+--------------+ 2666 | ssrc-group:FID | Not Impacted | SR | NORMAL | 2667 | | | | | 2668 | ssrc-group:FEC | Not Impacted | SR | NORMAL | 2669 | | | | | 2670 | ssrc-group:FEC-FR | Not Impacted | SR | NORMAL | 2671 | | | | | 2672 +--------------------+---------------+-------+--------------+ 2674 RFC5576 Attribute Analysis 2676 9.2. RFC7104: Duplication Grouping Semantics in the SDP 2678 [RFC7104] defines the semantics for grouping redundant streams in 2679 SDP. The semantics defined in this document are to be used with the 2680 SDP Grouping Framework. Grouping semantics at the Synchronization 2681 Source (SSRC) level are also defined in this document for RTP streams 2682 using SSRC multiplexing. 2684 +-----------------+---------------+-------+--------------+ 2685 | Name | Notes | Level | Mux Category | 2686 +-----------------+---------------+-------+--------------+ 2687 | ssrc-group:DUP | Not Impacted | SR | NORMAL | 2688 | | | | | 2689 +-----------------+---------------+-------+--------------+ 2691 RFC7104 Attribute Analysis 2693 10. QoS Mechanism Token Analysis 2695 This section analyzes QoS tokes specified with SDP. 2697 10.1. RFC5432: QoS Mechanism Selection in SDP 2699 [RFC5432] defines procedures to negotiate QOS mechanisms using the 2700 SDP offer/answer model. 2702 +-------+--------------------------------------+-------+------------+ 2703 | Name | Notes | Level | Mux | 2704 | | | | Category | 2705 +-------+--------------------------------------+-------+------------+ 2706 | rsvp | rsvp attribute MUST be the one that | B | TRANSPORT | 2707 | | corresponds to the "m=" line chosen | | | 2708 | | for setting up the underlying | | | 2709 | | transport flow | | | 2710 | | | | | 2711 | nsis | rsvp attribute MUST be the one that | B | TRANSPORT | 2712 | | corresponds to the "m=" line chosen | | | 2713 | | for setting up the underlying | | | 2714 | | transport | | | 2715 | | | | | 2716 +-------+--------------------------------------+-------+------------+ 2718 RFC5432 Attribute Analysis 2720 NOTE: A single Differentiated Services Code Point (DSCP) code point 2721 per flow being multiplexed doesn't impact multiplexing since QOS 2722 mechanisms are signaled/scoped per flow. For scenarios that involve 2723 having different DSCP code points for packets being transmitted over 2724 the same 5-tuple, issues as discussed in [RFC7657] need to be taken 2725 into consideration. 2727 11. k= Attribute Analysis 2728 11.1. RFC4566: SDP 2730 [RFC4566] defines SDP that is intended for describing multimedia 2731 sessions for the purposes of session announcement, session 2732 invitation, and other forms of multimedia session initiation. 2734 +------+------------------------------------+-------+---------------+ 2735 | Name | Notes | Level | Mux Category | 2736 +------+------------------------------------+-------+---------------+ 2737 | k= | It is NOT recommended to use this | S | NOT | 2738 | | attribute | | RECOMMENDED | 2739 | | | | | 2740 +------+------------------------------------+-------+---------------+ 2742 RFC4566 Attribute Analysis 2744 12. content Attribute Analysis 2746 12.1. RFC4796 2748 [RFC4796] defines a new SDP media-level attribute, 'content'. The 2749 'content' attribute defines the content of the media stream to a more 2750 detailed level than the media description line. The sender of an SDP 2751 session description can attach the 'content' attribute to one or more 2752 media streams. The receiving application can then treat each media 2753 stream differently (e.g., show it on a big or small screen) based on 2754 its content. 2756 +------------------+---------------+-------+--------------+ 2757 | Name | Notes | Level | Mux Category | 2758 +------------------+---------------+-------+--------------+ 2759 | content:slides | Not Impacted | M | NORMAL | 2760 | | | | | 2761 | content:speaker | Not Impacted | M | NORMAL | 2762 | | | | | 2763 | content:main | Not Impacted | M | NORMAL | 2764 | | | | | 2765 | content:sl | Not Impacted | M | NORMAL | 2766 | | | | | 2767 | content:alt | Not Impacted | M | NORMAL | 2768 | | | | | 2769 +------------------+---------------+-------+--------------+ 2771 RFC4796 Attribute Analysis 2773 13. Payload Formats 2775 13.1. RFC5109: RTP Payload Format for Generic FEC 2777 [RFC5109] describes a payload format for generic Forward Error 2778 Correction (FEC) for media data encapsulated in RTP. It is based on 2779 the exclusive-or (parity) operation. The payload format allows end 2780 systems to apply protection using various protection lengths and 2781 levels, in addition to using various protection group sizes to adapt 2782 to different media and channel characteristics. It enables complete 2783 recovery of the protected packets or partial recovery of the critical 2784 parts of the payload depending on the packet loss situation. 2786 +---------------------+----------------------+-------+--------------+ 2787 | Name | Notes | Level | Mux Category | 2788 +---------------------+----------------------+-------+--------------+ 2789 | audio/ulpfec | Not recommended for | M | NOT | 2790 | | multiplexing due to | | RECOMMENDED | 2791 | | reuse of SSRCs | | | 2792 | | | | | 2793 | video/ulpfec | Not recommended for | M | NOT | 2794 | | multiplexing due to | | RECOMMENDED | 2795 | | reuse of SSRCs | | | 2796 | | | | | 2797 | text/ulpfec | Not recommended for | M | NOT | 2798 | | multiplexing due to | | RECOMMENDED | 2799 | | reuse of SSRCs | | | 2800 | | | | | 2801 | application/ulpfec | Not recommended for | M | NOT | 2802 | | multiplexing due to | | RECOMMENDED | 2803 | | reuse of SSRCs | | | 2804 | | | | | 2805 +---------------------+----------------------+-------+--------------+ 2807 RFC5109 Payload Format Analysis 2809 14. Multiplexing Considerations for Encapsulating Attributes 2811 This sections deals with recommendations for defining the 2812 multiplexing characteristics of the SDP attributes that encapsulate 2813 other SDP attributes/parameters. Such attributes as of today, for 2814 example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of 2815 a generic framework for indicating and negotiating transport, media, 2816 and media format related capabilities in the SDP. 2818 The behavior of such attributes under multiplexing is in turn defined 2819 by the multiplexing behavior of the attributes they encapsulate which 2820 are made known once the Offer/Answer negotiation process is 2821 completed. 2823 14.1. RFC3407: cpar Attribute Analysis 2825 [RFC3407] capability parameter attribute (a=cpar) encapsulates b= 2826 (bandwidth) or an a= attribute. For bandwidth attribute 2827 encapsulation, the category SUM is inherited. For the case of a= 2828 attribute, the category corresponding to the SDP attribute being 2829 encapsulated is inherited. 2831 v=0 2832 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2833 s= 2834 c=IN IP4 host.atlanta.example.com 2835 t=0 0 2836 m=video 3456 RTP/AVP 100 2837 a=rtpmap:100 VP8/90000 2838 a=sqn: 0 2839 a=cdsc: 1 video RTP/AVP 100 2840 a=cpar: a=rtcp-mux 2841 m=video 3456 RTP/AVP 101 2842 a=rtpmap:101 VP8/90000 2843 a=fmtp:100 max-fr=15;max-fs=1200 2844 a=cdsc: 2 video RTP/AVP 101 2845 a=cpar: a=rtcp-mux 2847 In the above example,the category IDENTICAL is inherited for the cpar 2848 encapsulated rtcp-mux attribute. 2850 14.2. RFC5939 Analysis 2852 [RFC5939] defines a general SDP capability negotiation framework. It 2853 also specifies how to provide transport protocols and SDP attributes 2854 as capabilities and negotiate them using the framework. 2856 For this purpose, [RFC5939] defines the following 2858 o A set of capabilities for the session and its associated media 2859 stream components, supported by each side. The attribute 2860 ("a=acap") defines how to list an attribute name and its 2861 associated value (if any) as a capability. The attribute 2862 ("a=tcap") defines how to list transport protocols (e.g., "RTP/ 2863 AVP") as capabilities. 2865 o A set of potential configurations ("a=pcfg") provided by the 2866 offerer to indicate which combinations of those capabilities can 2867 be used for the session and its associated media stream 2868 components. Potential configurations are not ready for use until 2869 fully negotiated. They provide an alternative that MAY be used, 2870 subject to SDP capability negotiation procedures. In particular 2871 the answerer MAY choose one of the potential configurations for 2872 use as part of the current Offer/Answer exchange. 2874 o An actual configuration ("a=acfg") for the session and its 2875 associated media stream components. The actual configuration 2876 identifies the potential configuration that was negotiated for 2877 use. Use of an actual configuration does not require any further 2878 negotiation. 2880 o A negotiation process that takes the current actual and the set of 2881 potential configurations (combinations of capabilities) as input 2882 and provides the negotiated actual configurations as output. In 2883 [RFC5939] the negotiation process is done independently for each 2884 media description. 2886 14.2.1. Recommendation: Procedures for Potential Configuration Pairing 2888 This section provides recommendations for entities generating and 2889 processing SDP under the generic capability negotiation framework as 2890 defined in [RFC5939] under the context of media stream multiplexing. 2892 These recommendations are provided for the purposes of enabling the 2893 Offerer to make sure that the generated potential configurations 2894 between the multiplexed streams can (easily) be negotiated to be 2895 consistent between those streams. In particular, the procedures aim 2896 to simplify Answerer's procedure to choose potential configurations 2897 that are consistent across all the multiplexed media descriptions. 2899 A potential configuration selects a set of attributes and parameters 2900 that become part of the media description when negotiated. When 2901 multiplexing media descriptions with potential configurations 2902 specified, there MAY be a need for coordinating this selection 2903 between multiplexed media descriptions to ensure the right 2904 multiplexing behavior. 2906 Although it is possible to analyze the various potential 2907 configurations in multiplexed media descriptions to find combinations 2908 that satisfy such constraints, it can quickly become complicated to 2909 do so. 2911 The procedures defined in [RFC5939] state that each potential 2912 configuration in the SDP has a unique configuration number, however 2913 the scope of uniqueness is limited to each media description. To 2914 make it simple for the answerer to chose valid combinations of 2915 potential configurations across media descriptions in a given bundle 2916 group, we provide a simple rule for constructing potential 2917 configurations 2919 o Let m-bundle be the set of media descriptions that form a given 2920 bundle . 2922 o Let m-bundle-pcfg be the set of media descriptions in m-bundle 2923 that include one or more potential configurations. 2925 o Each media description in m-bundle-pcfg MUST have at least one 2926 potential configuration with the same configuration number (e.g. 2927 "1"). 2929 o For each potential configuration with configuration number x in m- 2930 bundle-pcfg, the offerer MUST ensure that if the answerer chooses 2931 configuration number x in each of the media descriptions in m- 2932 bundle-pcfg, then the resulting SDP will have all multiplexing 2933 constraints satisfied for those media descriptions. 2935 o Since it is nearly impossible to define a generic mechanism for 2936 various capability extensions, this document does't provide 2937 procedures for dealing with the capability extension attributes. 2938 However, Section 14.3 provide analysis of media capability 2939 extension attributes as defined in [RFC6871]. 2941 The above allows the answerer to easily find multiplexing compatible 2942 combinations of potential configurations: The answerer simply choses 2943 a potential configuration (number) that is present in all of the 2944 media descriptions with potential configurations in the bundle. 2946 Note that it is still possible for the offerer to provide additional 2947 potential configurations with independent configuration numbers. The 2948 answerer will have to perform more complicated analysis to determine 2949 valid multiplexed combinations of those. 2951 14.2.1.1. Example: Transport Capability Multiplexing 2952 v=0 2953 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2954 s= 2955 c=IN IP4 host.atlanta.example.com 2956 t=0 0 2957 a=tcap:1 RTP/SAVPF 2958 a=tcap:2 RTP/SAVP 2959 a=group:BUNDLE audio video 2960 m=audio 2961 a=mid:audio 2962 a=pcfg:1 t=1 2963 a=pcfg:2 2964 m=video 2965 a=mid:video 2966 a=pcfg:1 t=1 2967 a=pcfg:2 t=2 2969 In the example above, the potential configurations that offer 2970 transport protocol capability of RTP/SAVPF has the same configuration 2971 number "1" in both the audio and video media descriptions. 2973 14.2.1.2. Example: Attribute Capability Multiplexing 2975 v=0 2976 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com 2977 s= 2978 c=IN IP4 host.atlanta.example.com 2979 t=0 0 2980 a=acap:1 a=rtcp-mux 2981 a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80 2982 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32 2983 a=group:BUNDLE audio video 2984 m=audio 49172 RTP/AVP 99 2985 a=mid:audio 2986 a=pcfg:1 a=1 2987 a=pcfg:2 2988 m=video 560024 RTP/AVP 100 2989 a=mid:video 2990 a=pcfg:1 a=1 2991 a=pcfg:2 a=2 2993 In the example above, the potential configuration number "1" is 2994 repeated while referring to attribute capability a=rtcp-mux, since 2995 the behavior is IDENTICAL for the attribute a=rtcp-mux under 2996 multiplexing. 2998 14.3. RFC6871 Analysis 3000 [RFC6871] extends capability negotiation framework described in 3001 [RFC5939] by defining media capabilities that can be used to indicate 3002 and negotiate media types and their associated format parameters. It 3003 also allows indication of latent configurations and session 3004 capabilities. 3006 14.3.1. Recommendation: Dealing with Payload Type Numbers 3008 [RFC6871] defines a new payload type ("pt") parameter to be used with 3009 the potential, actual, and latent configuration parameters. The 3010 parameter associates RTP payload type numbers with the referenced 3011 RTP-based media format capabilities ("a=rmcap") defined in [RFC6871] 3012 and is appropriate only when the transport protocol uses RTP. This 3013 means that the same payload type number can be assigned as part of 3014 potential or actual configurations in different media descriptions in 3015 a bundle. There are rules for the usage of identical Payload Type 3016 values across multiplexed "m=" lines as described in 3017 [I-D.ietf-mmusic-sdp-bundle-negotiation], which MUST be followed here 3018 as well. As described in Section 14.2.1, the use of identical 3019 configuration numbers for compatible configurations in different 3020 media descriptions that are part of the bundle provides a way to 3021 ensure that the answerer can easily pick compatible configurations 3022 here as well. 3024 14.3.1.1. Example: Attribute Capability Under Shared Payload Type 3026 The attributes (a=rmcap, a=mfcap) follow the above recommendations 3027 under multiplexing. 3029 v=0 3030 o=- 25678 753849 IN IP4 192.0.2.1 3031 s= 3032 c=IN IP4 192.0.2.1 3033 t=0 0 3034 a=creq:med-v0 3035 m=audio 54322 RTP/AVP 96 3036 a=rtpmap:96 AMR-WB/16000/1 3037 a=fmtp:96 mode-change-capability=1; max-red=220; 3038 mode-set=0,2,4,7 3039 a=rmcap:1,3 audio AMR-WB/16000/1 3040 a=rmcap:2 audio AMR/8000/1 3041 a=mfcap:1,2 mode-change-capability=1 3042 a=mfcap:3 mode-change-capability=2 3043 a=pcfg:1 m=1 pt=1:96 3044 a=pcfg:2 m=2 pt=2:97 3045 a=pcfg:3 m=3 pt=3:98 3046 m=audio 54322 RTP/AVP 96 3047 a=rtpmap:96 AMR-WB/16000/1 3048 a=fmtp:96 mode-change-capability=1; max-red=220; 3049 mode-set=0,2,4,7 3050 a=rmcap:4 audio AMR/8000/1 3051 a=rmcap:5 audio OPUS/48000/2 3052 a=mfcap:5 minptime=40 3053 a=mfcap:4 mode-change-capability=1 3054 a=pcfg:1 m=4 pt=4:97 3055 a=pcfg:4 m=5 pt=5:101 3057 In the example above, the potential configuration number "1" is 3058 repeated when referring to media and media format capability used for 3059 the Payload Type 96. This implies that both the media capability 2 3060 and 4 along with their media format capabilities MUST refer to the 3061 same codec configuration, as per the definition of IDENTICAL-PER-PT. 3063 14.3.2. Recommendation: Dealing with Latent Configurations 3065 [RFC6871] adds the notion of a latent configurations, which provides 3066 configuration information that MAY be used to guide a subsequent 3067 offer/exchange, e.g. by adding another media stream or use 3068 alternative codec combinations not currently offered. Latent 3069 configurations have configuration numbers which cannot overlap with 3070 the potential configuration numbers [RFC6871]. Supported 3071 combinations of potential and latent configurations are indicated by 3072 use of the "a=sescap" attribute, however use of this attribute is NOT 3073 RECOMMENDED with multiplexed media, since it requires the use of 3074 unique configuration numbers across the SDP. Taken together, this 3075 means there is no well-defined way to indicate supported combinations 3076 of latent configurations, or combinations of latent and potential 3077 configurations with multiplexed media. It is still allowed to use 3078 the latent configuration attribute, however the limitations above 3079 will apply. To determine valid combinations, actual negotiation will 3080 have to be attempted subsequently instead. 3082 15. IANA Considerations 3084 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this 3085 document.] 3087 The IANA is requested to add a new column named "Mux Category" to 3088 several of the subregistries in the "Session Description Protocol 3089 (SDP) Parameters" registry. Section 15.1 defines a new subregistry 3090 for identifying the initial registrations for various multiplexing 3091 categories applicable, as proposed in this document. 3093 The tables in Section 15.2 identify name of an entry in the existing 3094 subregistry and specify the value to put in the new "Mux Category" 3095 column of the associated IANA registry. Any entries in the existing 3096 tables that do not have a value for the "Mux Category" specified in 3097 this RFC will get a value of "TBD". Future specifications can change 3098 the "TBD" entries to the correct value. 3100 15.1. New 'Multiplexing Categories' subregistry 3102 A new sub-registry needs to be defined called the "Multiplexing 3103 Categories", with the following registrations created initially: 3104 "NORMAL", "NOT RECOMMENDED", "IDENTICAL", "TRANSPORT", "SUM", 3105 "INHERIT", "IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this 3106 document. 3108 Initial value registration for "Multiplexing Categories". 3110 +-------------------------+-----------+ 3111 | Multiplexing Categories | Reference | 3112 +-------------------------+-----------+ 3113 | NORMAL | RFCXXXX | 3114 | NOT RECOMMENDED | RFCXXXX | 3115 | IDENTICAL | RFCXXXX | 3116 | TRANSPORT | RFCXXXX | 3117 | SUM | RFCXXXX | 3118 | INHERIT | RFCXXXX | 3119 | IDENTICAL-PER-PT | RFCXXXX | 3120 | SPECIAL | RFCXXXX | 3121 | TBD | RFCXXXX | 3122 +-------------------------+-----------+ 3123 Further entries can be registered on a first-come first-serve basis. 3124 Each registration needs to indicate the multiplexing category value 3125 to be added to the "Multiplexing Categories" subregistry as defined 3126 in this section. 3128 Such a registration MUST also indicate the applicability of the newly 3129 defined multiplexing category value to various subregistries defined 3130 at "Session Description Protocol (SDP) Parameters". 3132 The general registration procedures of [RFC4566] apply. 3134 15.2. 'Mux Category' column for subregistries 3136 Each sub-section identifies a subregistry in the "Session Description 3137 Protocol (SDP) Parameters" registry. The tables list the column that 3138 identifies the SDP attribute name/Token/Value from the corresponding 3139 subregistries and the values to be used for the new "Mux Category" 3140 column to be added. 3142 15.2.1. Table: SDP bwtype 3144 The following values are to be added to the 'SDP bwtype' subregistry 3145 in the "Session Description Protocol (SDP) Parameters" registry. The 3146 references should be updated to point at this RFC as well as the 3147 previous references. 3149 +----------+--------------+ 3150 | SDP Name | Mux Category | 3151 +----------+--------------+ 3152 | CT | NORMAL | 3153 | AS | SUM | 3154 | RS | SUM | 3155 | RR | SUM | 3156 | TIAS | SPECIAL | 3157 +----------+--------------+ 3159 15.2.2. Table: att-field (session level) 3161 The following values are to be added to the "att-field (session 3162 level)" subregistry in the "Session Description Protocol (SDP) 3163 Parameters" registry. The references should be updated to point at 3164 this RFC as well as the previous references. 3166 +---------------------+------------------+ 3167 | SDP Name | Mux Category | 3168 +---------------------+------------------+ 3169 | cat | NORMAL | 3170 | keywds | NORMAL | 3171 | type | NORMAL | 3172 | type:broadcast | NORMAL | 3173 | type:H332 | NORMAL | 3174 | type:meeting | NORMAL | 3175 | type:moderated | NORMAL | 3176 | type:test | NORMAL | 3177 | charset | NORMAL | 3178 | charset:iso8895-1 | NORMAL | 3179 | tool | NORMAL | 3180 | ipbcp | SPECIAL | 3181 | group | NORMAL | 3182 | ice-lite | NORMAL | 3183 | ice-options | NORMAL | 3184 | bcastversion | NORMAL | 3185 | 3GPP-Integrity-Key | NOT RECOMMENDED | 3186 | 3GPP-SDP-Auth | NOT RECOMMENDED | 3187 | alt-group | NOT RECOMMENDED | 3188 | PSCid | NORMAL | 3189 | bc_service | NORMAL | 3190 | bc_program | NORMAL | 3191 | bc_service_package | NORMAL | 3192 | sescap | NOT RECOMMENDED | 3193 | rtsp-ice-d-m | TBD | 3194 +---------------------+------------------+ 3196 15.2.3. Table: att-field (both session and media level) 3198 The following values are to be added to the "att-field (both session 3199 and media level)" subregistry in the "Session Description Protocol 3200 (SDP) Parameters" registry. The references should be updated to 3201 point at this RFC as well as the previous references. 3203 NOTE: The attributes from draft-ietf-rmt-flute-sdp ('flute-tsi', 3204 'flute-ch', 'FEC-declaration', 'FEC-OTI-extension', 'content-desc') 3205 were not analyzed for their multiplexing behavior due to the expired 3206 status of the draft. For purposes of this specification, the 3207 multiplexing category of 'TBD' is assigned. 3209 +-------------------------+-------------------+ 3210 | SDP Name | Mux Category | 3211 +-------------------------+-------------------+ 3212 | recvonly | NORMAL | 3213 | sendrecv | NORMAL | 3214 | sendonly | NORMAL | 3215 | sdplang | NORMAL | 3216 | lang | NORMAL | 3217 | h248item | SPECIAL | 3218 | sqn | NORMAL | 3219 | cdsc | NORMAL | 3220 | cpar | INHERIT | 3221 | cparmin | SPECIAL | 3222 | cparmax | SPECIAL | 3223 | rtcp-xr | NORMAL | 3224 | maxprate | SPECIAL | 3225 | setup | IDENTICAL | 3226 | connection | IDENTICAL | 3227 | key-mgmt | IDENTICAL | 3228 | source-filter | IDENTICAL | 3229 | inactive | NORMAL | 3230 | fingerprint | TRANSPORT | 3231 | flute-tsi | TBD | 3232 | flute-ch | TBD | 3233 | FEC-declaration | TBD | 3234 | FEC-OTI-extension | TBD | 3235 | content-desc | TBD | 3236 | ice-pwd | TRANSPORT | 3237 | ice-ufrag | TRANSPORT | 3238 | stkmstream | NORMAL | 3239 | extmap | SPECIAL | 3240 | qos-mech-send | TRANSOPORT | 3241 | qos-mech-recv | TRANSPORT | 3242 | csup | NORMAL | 3243 | creq | NORMAL | 3244 | acap | INHERIT | 3245 | tcap | INHERIT | 3246 | 3GPP-QoE-Metrics | NOT RECOMMENDED | 3247 | 3GPP-Asset-Information | NOT RECOMMENDED | 3248 | mbms-mode | NOT RECOMMENDED | 3249 | mbms-repair | NOT RECOMMENDED | 3250 | ike-setup | IDENTICAL | 3251 | psk-fingerprint | IDENTICAL | 3252 | multicast-rtcp | IDENTICAL | 3253 | rmcap | IDENTICAL-PER-PT | 3254 | omcap | NORMAL | 3255 | mfcap | IDENTICAL-PER-PT | 3256 | mscap | INHERIT | 3257 | 3gpp.iut.replication | TBD | 3258 | bcap | INHERIT | 3259 | ccap | IDENTICAL | 3260 | icap | NORMAL | 3261 | 3gpp_sync_info | NORMAL | 3262 | 3gpp_MaxRecvSDUSize | NORMAL | 3263 | etag | NOT RECOMMENDED | 3264 | duplication-delay | NORMAL | 3265 | range | NOT RECOMMENDED | 3266 | control | NOT RECOMMENDED | 3267 | mtag | NOT RECOMMENDED | 3268 | ts-refclk | NORMAL | 3269 | mediaclk | NORMAL | 3270 | calgextmap | NORMAL | 3271 +-------------------------+-------------------+ 3273 15.2.4. Table: att-field (media level only) 3275 The following values are to be added to the "att-field (media level 3276 only)" registry in the "Session Description Protocol (SDP) 3277 Parameters" registry. The references should be updated to point at 3278 this RFC as well as the previous references. 3280 +---------------------------+-------------------+ 3281 | SDP Name | Mux Category | 3282 +---------------------------+-------------------+ 3283 | ptime | IDENTICAL-PER-PT | 3284 | orient | NORMAL | 3285 | orient:portrait | NORMAL | 3286 | orient:landscape | NORMAL | 3287 | orient:seascape | NORMAL | 3288 | framerate | IDENTICAL-PER-PT | 3289 | quality | NORMAL | 3290 | rtpmap | IDENTICAL-PER-PT | 3291 | fmtp | IDENTICAL-PER-PT | 3292 | rtpred1 | NOT RECOMMENDED | 3293 | rtpred2 | NOT RECOMMENDED | 3294 | T38FaxVersion | TBD | 3295 | T38MaxBitRate | TBD | 3296 | T38FaxFillBitRemoval | TBD | 3297 | T38FaxTranscodingMMR | TBD | 3298 | T38FaxTranscodingJBIG | TBD | 3299 | T38FaxRateManagement | TBD | 3300 | T38FaxMaxBuffer | TBD | 3301 | T38FaxMaxDatagram | TBD | 3302 | T38FaxUdpEC | TBD | 3303 | maxptime | IDENTICAL-PER-PT | 3304 | des | NOT RECOMMENDED | 3305 | curr | NOT RECOMMENDED | 3306 | conf | NOT RECOMMENDED | 3307 | mid | NORMAL | 3308 | rtcp | TRANSPORT | 3309 | rtcp-fb | IDENTICAL-PER-PT | 3310 | label | NORMAL | 3311 | T38VendorInfo | TBD | 3312 | crypto | TRANSPORT | 3313 | eecid | NOT RECOMMENDED | 3314 | aalType | NOT RECOMMENDED | 3315 | capability | NOT RECOMMENDED | 3316 | qosClass | NOT RECOMMENDED | 3317 | bcob | NOT RECOMMENDED | 3318 | stc | NOT RECOMMENDED | 3319 | upcc | NOT RECOMMENDED | 3320 | atmQOSparms | NOT RECOMMENDED | 3321 | atmTrfcDesc | NOT RECOMMENDED | 3322 | abrParms | NOT RECOMMENDED | 3323 | abrSetup | NOT RECOMMENDED | 3324 | bearerType | NOT RECOMMENDED | 3325 | lij | NOT RECOMMENDED | 3326 | anycast | NOT RECOMMENDED | 3327 | cache | NOT RECOMMENDED | 3328 | bearerSigIE | NOT RECOMMENDED | 3329 | aalApp | NOT RECOMMENDED | 3330 | cbrRate | NOT RECOMMENDED | 3331 | sbc | NOT RECOMMENDED | 3332 | clkrec | NOT RECOMMENDED | 3333 | fec | NOT RECOMMENDED | 3334 | prtfl | NOT RECOMMENDED | 3335 | structure | NOT RECOMMENDED | 3336 | cpsSDUsize | NOT RECOMMENDED | 3337 | all2CPS | NOT RECOMMENDED | 3338 | all2CPSSDUrate | NOT RECOMMENDED | 3339 | aal2sscs3661unassured | NOT RECOMMENDED | 3340 | aal2sscs3661assured | NOT RECOMMENDED | 3341 | aal2sscs3662 | NOT RECOMMENDED | 3342 | aal5sscop | NOT RECOMMENDED | 3343 | atmmap | NOT RECOMMENDED | 3344 | silenceSupp | NOT RECOMMENDED | 3345 | ecan | NOT RECOMMENDED | 3346 | gc | NOT RECOMMENDED | 3347 | profileDesc | NOT RECOMMENDED | 3348 | vsel | NOT RECOMMENDED | 3349 | dsel | NOT RECOMMENDED | 3350 | fsel | NOT RECOMMENDED | 3351 | onewaySel | NOT RECOMMENDED | 3352 | codecconfig | NOT RECOMMENDED | 3353 | isup_usi | NOT RECOMMENDED | 3354 | uiLayer1_Prot | NOT RECOMMENDED | 3355 | chain | NOT RECOMMENDED | 3356 | floorctrl | IDENTICAL | 3357 | confid | NORMAL | 3358 | userid | NORMAL | 3359 | floorid | NORMAL | 3360 | FEC | NORMAL | 3361 | accept-types | TBD | 3362 | accept-wrapped-types | TBD | 3363 | max-size | TBD | 3364 | path | TBD | 3365 | dccp-service-code | NOT RECOMMENDED | 3366 | rtcp-mux | IDENTICAL | 3367 | candidate | TRANSPORT | 3368 | ice-mismatch | NORMAL | 3369 | remote-candidates | TRANSPORT | 3370 | SRTPAuthentication | TBD | 3371 | SRTPROCTxRate | TBD | 3372 | rtcp-rsize | IDENTICAL | 3373 | file-selector | TBD | 3374 | file-transfer-id | TBD | 3375 | file-disposition | TBD | 3376 | file-date | TBD | 3377 | file-icon | TBD | 3378 | file-range | TBD | 3379 | depend | IDENTICAL-PER-PT | 3380 | ssrc | NORMAL | 3381 | ssrc-group | NORMAL | 3382 | rtcp-unicast | IDENTICAL | 3383 | pcfg | SPECIAL | 3384 | acfg | SPECIAL | 3385 | zrtp-hash | TRANSPORT | 3386 | X-predecbufsize | NOT RECOMMENDED | 3387 | X-initpredecbufperiod | NOT RECOMMENDED | 3388 | X-initpostdecbufperiod | NOT RECOMMENDED | 3389 | X-decbyterate | NOT RECOMMENDED | 3390 | 3gpp-videopostdecbufsize | NOT RECOMMENDED | 3391 | framesize | NOT RECOMMENDED | 3392 | 3GPP-SRTP-Config | NOT RECOMMENDED | 3393 | alt | NOT RECOMMENDED | 3394 | alt-default-id | NOT RECOMMENDED | 3395 | 3GPP-Adaption-Support | NOT RECOMMENDED | 3396 | mbms-flowid | NOT RECOMMENDED | 3397 | fec-source-flow | SPECIAL | 3398 | fec-repair-flow | SPECIAL | 3399 | repair-window | SPECIAL | 3400 | rams-updates | NOT RECOMMENDED | 3401 | imageattr | IDENTICAL-PER-PT | 3402 | cfw-id | NORMAL | 3403 | portmapping-req | NOT RECOMMENDED | 3404 | g.3gpp.cat | NORMAL | 3405 | g.3gpp.crs | NORMAL | 3406 | ecn-capable-rtp | IDENTICAL | 3407 | visited-realm | TRANSPORT | 3408 | secondary-realm | TRANSPORT | 3409 | omr-s-cksum | NORMAL | 3410 | omr-m-cksum | NORMAL | 3411 | omr-codecs | NORMAL | 3412 | omr-m-att | NORMAL | 3413 | omr-s-att | NORMAL | 3414 | omr-m-bw | NORMAL | 3415 | omr-s-bw | NORMAL | 3416 | msrp-cema | TBD | 3417 | dccp-port | NOT RECOMMENDED | 3418 | resource | NORMAL | 3419 | channel | NORMAL | 3420 | cmid | NORMAL | 3421 | content | NORMAL | 3422 | lcfg | SPECIAL | 3423 | loopback | NORMAL | 3424 | loopback-source | NORMAL | 3425 | loopback-mirror | NORMAL | 3426 | chatroom | TBD | 3427 | altc | TRANSPORT | 3428 | T38FaxMaxIFP | TBD | 3429 | T38FaxUdpECDepth | TBD | 3430 | T38FaxUdpFECMaxSpan | TBD | 3431 | T38ModemType | TBD | 3432 | cs-correlation | TBD | 3433 | rtcp-idms | NORMAL | 3434 +---------------------------+-------------------+ 3436 15.2.5. Table: att-field (source level) 3438 The following values are to be added to the "att-field (source 3439 level)" registry in the "Session Description Protocol (SDP) 3440 Parameters" registry. The references should be updated to point at 3441 this RFC as well as the previous references. 3443 +----------------+-------------------+ 3444 | SDP Name | Mux Category | 3445 +----------------+-------------------+ 3446 | cname | NORMAL | 3447 | previous-ssrc | NORMAL | 3448 | fmtp | IDENTICAL-PER-PT | 3449 | ts-refclk | NORMAL | 3450 | mediaclk | NORMAL | 3451 +----------------+-------------------+ 3453 15.2.6. Table: content SDP Parameters 3455 The following values are to be added to the "content SDP Parameters" 3456 subregistry in the "Session Description Protocol (SDP) Parameters" 3457 registry. The references should be updated to point at this RFC as 3458 well as the previous references. 3460 +----------+--------------+ 3461 | SDP Name | Mux Category | 3462 +----------+--------------+ 3463 | slides | NORMAL | 3464 | speaker | NORMAL | 3465 | sl | NORMAL | 3466 | main | NORMAL | 3467 | alt | NORMAL | 3468 +----------+--------------+ 3470 15.2.7. Table: Semantics for the 'group' SDP Attribute 3472 The following values are to be added to the "Semantics for the 3473 "group" SDP Attribute" subregistry in the "Session Description 3474 Protocol (SDP) Parameters" registry. The references should be 3475 updated to point at this RFC as well as the previous references. 3477 +---------+------------------+ 3478 | Token | Mux Category | 3479 +---------+------------------+ 3480 | LS | NORMAL | 3481 | FID | NORMAL | 3482 | SRF | NORMAL | 3483 | ANAT | NOT RECOMMENDED | 3484 | FEC | NORMAL | 3485 | FEC-FR | NORMAL | 3486 | CS | NORMAL | 3487 | DDP | NORMAL | 3488 | DUP | NORMAL | 3489 +---------+------------------+ 3491 15.2.8. Table: 'rtcp-fb' Attribute Values 3493 The following values are to be added to the " 'rtcp-fb' Attribute 3494 Values" subregistry in the "Session Description Protocol (SDP) 3495 Parameters" registry. The references should be updated to point at 3496 this RFC as well as the previous references. 3498 +------------+-------------------+ 3499 | Value Name | Mux Category | 3500 +------------+-------------------+ 3501 | ack | IDENTICAL-PER-PT | 3502 | app | SPECIAL | 3503 | ccm | IDENTICAL-PER-PT | 3504 | nack | IDENTICAL-PER-PT | 3505 | trr-int | IDENTICAL-PER-PT | 3506 +------------+-------------------+ 3508 15.2.9. Table: 'ack' and 'nack' Attribute Values 3510 The following values are to be added to the " 'ack' and 'nack' 3511 Attribute Values" subregistry in the "Session Description Protocol 3512 (SDP) Parameters" registry. The references should be updated to 3513 point at this RFC as well as the previous references. 3515 +------------+-------------------+ 3516 | Value Name | Mux Category | 3517 +------------+-------------------+ 3518 | sli | IDENTICAL-PER-PT | 3519 | pli | IDENTICAL-PER-PT | 3520 | rpsi | IDENTICAL-PER-PT | 3521 | app | SPECIAL | 3522 | rai | IDENTICAL-PER-PT | 3523 | tllei | IDENTICAL-PER-PT | 3524 | pslei | IDENTICAL-PER-PT | 3525 | ecn | IDENTICAL | 3526 +------------+-------------------+ 3528 15.2.10. Table: 'depend' SDP Attribute Values 3530 The following values are to be added to the " 'depend' SDP Attribute 3531 Values" subregistry in the "Session Description Protocol (SDP) 3532 Parameters" registry. The references should be updated to point at 3533 this RFC as well as the previous references. 3535 +-------+-------------------+ 3536 | Token | Mux Category | 3537 +-------+-------------------+ 3538 | lay | IDENTICAL-PER-PT | 3539 | mdc | IDENTICAL-PER-PT | 3540 +-------+-------------------+ 3542 15.2.11. Table: 'cs-correlation' Attribute Values 3544 The following values are to be added to the " "cs-correlation" 3545 Attribute Values" subregistry in the "Session Description Protocol 3546 (SDP) Parameters" registry. The references should be updated to 3547 point at this RFC as well as the previous references. 3549 +-----------+--------------+ 3550 | Value | Mux Category | 3551 +-----------+--------------+ 3552 | callerid | TBD | 3553 | uuie | TBD | 3554 | dtmf | TBD | 3555 | external | TBD | 3556 +-----------+--------------+ 3558 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 3560 The following values are to be added to the Semantics for the 3561 "Semantics for the "ssrc-group" SDP Attribute" subregistry in the 3562 "Session Description Protocol (SDP) Parameters" registry. The 3563 references should be updated to point at this RFC as well as the 3564 previous references. 3566 +---------+--------------+ 3567 | Token | Mux Category | 3568 +---------+--------------+ 3569 | FID | NORMAL | 3570 | FEC | NORMAL | 3571 | FEC-FR | NORMAL | 3572 | DUP | NORMAL | 3573 +---------+--------------+ 3575 15.2.13. Table: SDP/RTSP key management protocol identifiers 3577 The following values are to be added to the "SDP/RTSP key management 3578 protocol identifiers" subregistry in the "Session Description 3579 Protocol (SDP) Parameters" registry. The references should be 3580 updated to point at this RFC as well as the previous references. 3582 +------------+--------------+ 3583 | Value Name | Mux Category | 3584 +------------+--------------+ 3585 | mikey | IDENTICAL | 3586 +------------+--------------+ 3588 15.2.14. Table: Codec Control Messages 3590 The following values are to be added to the "Codec Control Messages" 3591 subregistry in the "Session Description Protocol (SDP) Parameters" 3592 registry. The references should be updated to point at this RFC as 3593 well as the previous references. 3595 +------------+-------------------+ 3596 | Value Name | Mux Category | 3597 +------------+-------------------+ 3598 | fir | IDENTICAL-PER-PT | 3599 | tmmbr | IDENTICAL-PER-PT | 3600 | tstr | IDENTICAL-PER-PT | 3601 | vbcm | IDENTICAL-PER-PT | 3602 +------------+-------------------+ 3604 15.2.15. Table: QoS Mechanism Tokens 3606 The following values are to be added to the "QoS Mechanism Tokens" 3607 subregistry in the "Session Description Protocol (SDP) Parameters" 3608 registry. The references should be updated to point at this RFC as 3609 well as the previous references. 3611 +---------------+--------------+ 3612 | QoS Mechanism | Mux Category | 3613 +---------------+--------------+ 3614 | rsvp | TRANSPORT | 3615 | nsis | TRANSPORT | 3616 +---------------+--------------+ 3618 15.2.16. Table: SDP Capability Negotiation Option Tags 3620 The following values are to be added to the "SDP Capability 3621 Negotiation Option Tags" subregistry in the "Session Description 3622 Protocol (SDP) Parameters" registry. The references should be 3623 updated to point at this RFC as well as the previous references. 3625 +------------+--------------+ 3626 | Option Tag | Mux Category | 3627 +------------+--------------+ 3628 | cap-v0 | NORMAL | 3629 | med-v0 | NORMAL | 3630 | bcap-v0 | NORMAL | 3631 | ccap-v0 | NORMAL | 3632 | icap-v0 | NORMAL | 3633 +------------+--------------+ 3635 15.2.17. Table: Timestamp Reference Clock Source Parameters 3637 The following values are to be added to the "Timestamp Reference 3638 Clock Source Parameters" subregistry in the "Session Description 3639 Protocol (SDP) Parameters" registry. The references should be 3640 updated to point at this RFC as well as the previous references. 3642 +----------+--------------+ 3643 | Name | Mux Category | 3644 +----------+--------------+ 3645 | ntp | NORMAL | 3646 | ptp | NORMAL | 3647 | gps | NORMAL | 3648 | gal | NORMAL | 3649 | glonass | NORMAL | 3650 | local | NORMAL | 3651 | private | NORMAL | 3652 +----------+--------------+ 3654 15.2.18. Table: Media Clock Source Parameters 3656 The following values are to be added to the "Media Clock Source 3657 Parameters" subegistry in the "Session Description Protocol (SDP) 3658 Parameters" registry. The references should be updated to point at 3659 this RFC as well as the previous references. 3661 +-----------+--------------+ 3662 | Name | Mux Category | 3663 +-----------+--------------+ 3664 | sender | NORMAL | 3665 | direct | NORMAL | 3666 | IEEE1722 | NORMAL | 3667 +-----------+--------------+ 3669 16. Security Considerations 3671 This document does not add any new security considerations beyond the 3672 existing considerations in the RFCs for protocols that are being 3673 multiplexed together. 3675 The ways that SRTP streams are keyed is not believed to create any 3676 two-time pad vulnerability for the currently defined SRTP keying 3677 mechanism. 3679 17. Acknowledgments 3681 I would like to thank Cullen Jennings, Flemming Andreasen for 3682 suggesting the categories, contributing text and reviewing the draft. 3683 I would also link to thank Magnus Westerlund, Christer Holmberg, 3684 Jonathan Lennox, Bo Burman, Ari Keranen, and Dan Wing on suggesting 3685 structural changes helping improve the document readability. 3687 I would like also to thank following experts on their inputs and 3688 reviews as listed - Flemming Andreasen(5.24,5.32,5.33,14), Rohan 3689 Mahy(5.57), Eric Burger(5.26),Christian Huitema(5.14), Christer 3690 Holmberg(5.21,5.26,5.51,5.52), Richard Ejzak (5.44,5.53,5.54), Colin 3691 Perkins(5.7,5.8,5.9,5.58), Magnus 3692 Westerlund(5.2,5.3,5.9,5.27,5.47,6.1,6.2,6.3,8.3,7), Roni 3693 Evens(5.12,5.27,8.4), Subha Dhesikan(5.6,10), Dan 3694 Wing(5.7,5.12,5.35,5.39,5.45), Cullen Jennings (5.40), Ali C 3695 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 3696 (7.2,7.6), Charles Eckel(5.15,5.27,5.28,9.1,8.5), Paul Kyzivat(5.24), 3697 Ian Johansson(5.15), Saravanan Shanmugham(5.11), Paul E Jones(5.30), 3698 Rajesh Kumar(5.48), Jonathan Lennox(5.36,5,15,9.1,11.1), Mo 3699 Zanaty(5.4,5.5,5.23,8.1,8.3,8.5,12.1), Christian Huitema (5.14), Qin 3700 Wu (5.47 PM-Dir review), Hans Stokking(5.43,5.16), Christian Groves 3701 (5.48,5.55), Thomas Stach. 3703 18. Change Log 3705 [RFC EDITOR NOTE: Please remove this section when publishing] 3707 Changes from draft-ietf-mmusic-sdp-mux-attributes-10 3709 o Incorporated Comments from Bo Burman for publication request 3711 Changes from draft-ietf-mmusic-sdp-mux-attributes-08 to draft-ietf- 3712 mmusic-sdp-mux-attributes-10 3714 o Minor nits and version update to advert expiration 3716 Changes from draft-ietf-mmusic-sdp-mux-attributes-06 to draft-ietf- 3717 mmusic-sdp-mux-attributes-08 3719 o Assigned TBD category to all the attributes for whom there exists 3720 no specification on multiplexing behavior over the underlying 3721 transport protocol today. 3723 o Incorporated comments from Flemming and Ari (post last call) 3725 Changes from draft-ietf-mmusic-sdp-mux-attributes-06 3726 o Incorporated last call review comments from Thomas Stach and Ari 3727 Keranen. 3729 o Fixed more nits to prep for the LastCall. 3731 Changes from draft-ietf-mmusic-sdp-mux-attributes-05 3733 o Incorporated review comments from Christian Grooves and Ari 3734 Keranen. 3736 o Fixed more nits to prep for the LastCall. 3738 Changes from draft-ietf-mmusic-sdp-mux-attributes-04 3740 o Fixed minor nits overall. 3742 o Updated Acknowledgement Sections 3744 o Last Call Version. 3746 Changes from draft-ietf-mmusic-sdp-mux-attributes-03 3748 o More re-work on the IANA section. 3750 o Clean ups preparing for the last call. 3752 Changes from draft-ietf-mmusic-sdp-mux-attributes-02 3754 o Incorporated suggestions from Flemming on Capability Negotiation. 3756 o Closed open issues from IETF90 3758 o Added IANA section to list the categories for all the SDP 3759 attributes anlayzed 3761 o Lots of cleanup 3763 o Reformatted Refernces section to use short-form notation 3765 Changes from draft-ietf-mmusic-sdp-mux-attributes-01 3767 o Updated section 15 to provide detailed recommendation on dealing 3768 with encapsulating attributes. Also updated sections 5.20, 5.28, 3769 5.29 to refer to Section 15. 3771 o Added new categories IDENTICAL-PER-PT and INHERIT 3773 o Updated Sections 16 to add the new categories. 3775 o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the 3776 category IDENTICAL-PER-PT. 3778 o Reformatted section 4 to add individual categories to their own 3779 sections. 3781 Changes from draft-ietf-mmusic-sdp-mux-attributes-00 3783 o Added Section 15 to provide recommendations on multiplexing SDP 3784 encapsulating attributes. Also updated sections 5.20, 5.28, 5.29 3785 to refer to Section 15. 3787 o Updated Section 5.38 to incorporate PM-dir review inputs from Qin 3788 Wu 3790 o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more 3791 clarity. 3793 o Fixed few nits regarding sentence clarity and fill-in the NOTES 3794 section where information was lacking. 3796 Changes from draft-nandakumar-mmusic-mux-attributes-05 3798 o Renamed the document to be a WG document. 3800 o Added Section 14. 3802 o Updated Open Issues based on IETF88 discussions. 3804 Changes from draft-nandakumar-mmusic-mux-attributes-04 3806 o Added few OPEN ISSUES that needs to be discussed. 3808 o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4, 3809 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1 3811 o Updated Table Column name Current to Level and improved TRANSPORT 3812 category explanation on suggestions form Dan Wing. 3814 o Grouped all the rtcp-fb attribute analysis under a single section 3815 as suggested by Magnus/ 3817 Changes from draft-nandakumar-mmusic-mux-attributes-03 3819 o Maintenance change to clean up grammatical nits and wordings. 3821 Changes from draft-nandakumar-mmusic-mux-attributes-02 3822 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34, 3823 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 3824 the inputs from the respective RFC Authors. 3826 Changes from draft-nandakumar-mmusic-mux-attributes-01 3828 o Replaced Category BAD with NOT RECOMMENDED. 3830 o Added Category TBD. 3832 o Updated IANA Consideration Section. 3834 Changes from draft-nandakumar-mmusic-mux-attributes-00 3836 o Added new section for dealing with FEC payload types. 3838 19. References 3840 19.1. Normative References 3842 [I-D.ietf-mmusic-sdp-bundle-negotiation] 3843 Holmberg, C., Alvestrand, H., and C. Jennings, 3844 "Negotiating Media Multiplexing Using the Session 3845 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- 3846 negotiation-24 (work in progress), January 2016. 3848 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3849 Requirement Levels", BCP 14, RFC 2119, March 1997. 3851 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 3852 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 3853 July 2006, . 3855 19.2. Informative References 3857 [H.248.15] 3858 "Gateway control protocol: SDP H.248 package attribute", 3859 . 3861 [IANA] "Session Description Protocol (SDP) Parameters", 3862 . 3865 [Q.1970] "Q.1970 : BICC IP bearer control protocol", 3866 . 3868 [R3GPPTS183.063] 3869 "TISPAN - IMS based ITPV Stage 3 specification.", 3870 . 3874 [R3GPPTS24.182] 3875 "IP Multimedia Subsystem (IMS) Customized Alerting Tones 3876 (CAT); Protocol specification", 3877 . 3879 [R3GPPTS24.183] 3880 "IP Multimedia Subsystem (IMS) Customized Ringing Signal 3881 (CRS); Protocol specification", 3882 . 3884 [R3GPPTS24.229] 3885 "IP multimedia call control protocol based on Session 3886 Initiation Protocol (SIP) and Session Description Protocol 3887 (SDP);", 3888 . 3890 [R3GPPTS26.114] 3891 "IP multimedia Subsystem : Media Handling and 3892 interaction", . 3894 [RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time 3895 Streaming Protocol (RTSP)", RFC 2326, DOI 10.17487/ 3896 RFC2326, April 1998, 3897 . 3899 [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the 3900 Session Description Protocol (SDP) for ATM Bearer 3901 Connections", RFC 3108, DOI 10.17487/RFC3108, May 2001, 3902 . 3904 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 3905 with Session Description Protocol (SDP)", RFC 3264, DOI 3906 10.17487/RFC3264, June 2002, 3907 . 3909 [RFC3312] Camarillo, G., Ed., Marshall, W., Ed., and J. Rosenberg, 3910 "Integration of Resource Management and Session Initiation 3911 Protocol (SIP)", RFC 3312, DOI 10.17487/RFC3312, October 3912 2002, . 3914 [RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple 3915 Capability Declaration", RFC 3407, DOI 10.17487/RFC3407, 3916 October 2002, . 3918 [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to 3919 Resource Reservation Flows", RFC 3524, DOI 10.17487/ 3920 RFC3524, April 2003, 3921 . 3923 [RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth 3924 Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC 3925 3556, DOI 10.17487/RFC3556, July 2003, 3926 . 3928 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute 3929 in Session Description Protocol (SDP)", RFC 3605, DOI 3930 10.17487/RFC3605, October 2003, 3931 . 3933 [RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed., 3934 "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3935 3611, DOI 10.17487/RFC3611, November 2003, 3936 . 3938 [RFC3890] Westerlund, M., "A Transport Independent Bandwidth 3939 Modifier for the Session Description Protocol (SDP)", RFC 3940 3890, DOI 10.17487/RFC3890, September 2004, 3941 . 3943 [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network 3944 Address Types (ANAT) Semantics for the Session Description 3945 Protocol (SDP) Grouping Framework", RFC 4091, DOI 3946 10.17487/RFC4091, June 2005, 3947 . 3949 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in 3950 the Session Description Protocol (SDP)", RFC 4145, DOI 3951 10.17487/RFC4145, September 2005, 3952 . 3954 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E. 3955 Carrara, "Key Management Extensions for Session 3956 Description Protocol (SDP) and Real Time Streaming 3957 Protocol (RTSP)", RFC 4567, DOI 10.17487/RFC4567, July 3958 2006, . 3960 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session 3961 Description Protocol (SDP) Security Descriptions for Media 3962 Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, 3963 . 3965 [RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol 3966 (SDP) Source Filters", RFC 4570, DOI 10.17487/RFC4570, 3967 July 2006, . 3969 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 3970 Transport Layer Security (TLS) Protocol in the Session 3971 Description Protocol (SDP)", RFC 4572, DOI 10.17487/ 3972 RFC4572, July 2006, 3973 . 3975 [RFC4574] Levin, O. and G. Camarillo, "The Session Description 3976 Protocol (SDP) Label Attribute", RFC 4574, DOI 10.17487/ 3977 RFC4574, August 2006, 3978 . 3980 [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format 3981 for Binary Floor Control Protocol (BFCP) Streams", RFC 3982 4583, DOI 10.17487/RFC4583, November 2006, 3983 . 3985 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, 3986 "Extended RTP Profile for Real-time Transport Control 3987 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, DOI 3988 10.17487/RFC4585, July 2006, 3989 . 3991 [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description 3992 Protocol (SDP) Content Attribute", RFC 4796, DOI 10.17487/ 3993 RFC4796, February 2007, 3994 . 3996 [RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed., 3997 "The Message Session Relay Protocol (MSRP)", RFC 4975, DOI 3998 10.17487/RFC4975, September 2007, 3999 . 4001 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman, 4002 "Codec Control Messages in the RTP Audio-Visual Profile 4003 with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104, 4004 February 2008, . 4006 [RFC5109] Li, A., Ed., "RTP Payload Format for Generic Forward Error 4007 Correction", RFC 5109, DOI 10.17487/RFC5109, December 4008 2007, . 4010 [RFC5159] Dondeti, L., Ed. and A. Jerichow, "Session Description 4011 Protocol (SDP) Attributes for Open Mobile Alliance (OMA) 4012 Broadcast (BCAST) Service and Content Protection", RFC 4013 5159, DOI 10.17487/RFC5159, March 2008, 4014 . 4016 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment 4017 (ICE): A Protocol for Network Address Translator (NAT) 4018 Traversal for Offer/Answer Protocols", RFC 5245, DOI 4019 10.17487/RFC5245, April 2010, 4020 . 4022 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP 4023 Header Extensions", RFC 5285, DOI 10.17487/RFC5285, July 4024 2008, . 4026 [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of 4027 Service (QoS) Mechanism Selection in the Session 4028 Description Protocol (SDP)", RFC 5432, DOI 10.17487/ 4029 RFC5432, March 2009, 4030 . 4032 [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size 4033 Real-Time Transport Control Protocol (RTCP): Opportunities 4034 and Consequences", RFC 5506, DOI 10.17487/RFC5506, April 4035 2009, . 4037 [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S., 4038 and P. Kyzivat, "A Session Description Protocol (SDP) 4039 Offer/Answer Mechanism to Enable File Transfer", RFC 5547, 4040 DOI 10.17487/RFC5547, May 2009, 4041 . 4043 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific 4044 Media Attributes in the Session Description Protocol 4045 (SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009, 4046 . 4048 [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding 4049 Dependency in the Session Description Protocol (SDP)", RFC 4050 5583, DOI 10.17487/RFC5583, July 2009, 4051 . 4053 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control 4054 Protocol (RTCP) Extensions for Single-Source Multicast 4055 Sessions with Unicast Feedback", RFC 5760, DOI 10.17487/ 4056 RFC5760, February 2010, 4057 . 4059 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and 4060 Control Packets on a Single Port", RFC 5761, DOI 10.17487/ 4061 RFC5761, April 2010, 4062 . 4064 [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control 4065 Protocol (DCCP)", RFC 5762, DOI 10.17487/RFC5762, April 4066 2010, . 4068 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework 4069 for Establishing a Secure Real-time Transport Protocol 4070 (SRTP) Security Context Using Datagram Transport Layer 4071 Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May 4072 2010, . 4074 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description 4075 Protocol (SDP) Grouping Framework", RFC 5888, DOI 4076 10.17487/RFC5888, June 2010, 4077 . 4079 [RFC5939] Andreasen, F., "Session Description Protocol (SDP) 4080 Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939, 4081 September 2010, . 4083 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in 4084 the Session Description Protocol", RFC 5956, DOI 10.17487/ 4085 RFC5956, September 2010, 4086 . 4088 [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions 4089 Defined for 3GPP Packet-Switched Streaming Service and 4090 Multimedia Broadcast/Multicast Service", RFC 6064, DOI 4091 10.17487/RFC6064, January 2011, 4092 . 4094 [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source- 4095 Specific Multicast (SSM) Sessions", RFC 6128, DOI 4096 10.17487/RFC6128, February 2011, 4097 . 4099 [RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP: 4100 Media Path Key Agreement for Unicast Secure RTP", RFC 4101 6189, DOI 10.17487/RFC6189, April 2011, 4102 . 4104 [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for 4105 the Internet Key Exchange Protocol (IKE) in the Session 4106 Description Protocol (SDP)", RFC 6193, DOI 10.17487/ 4107 RFC6193, April 2011, 4108 . 4110 [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media 4111 Control Channel Framework", RFC 6230, DOI 10.17487/ 4112 RFC6230, May 2011, 4113 . 4115 [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image 4116 Attributes in the Session Description Protocol (SDP)", RFC 4117 6236, DOI 10.17487/RFC6236, May 2011, 4118 . 4120 [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping 4121 between Unicast and Multicast RTP Sessions", RFC 6284, DOI 4122 10.17487/RFC6284, June 2011, 4123 . 4125 [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax, 4126 "Unicast-Based Rapid Acquisition of Multicast RTP 4127 Sessions", RFC 6285, DOI 10.17487/RFC6285, June 2011, 4128 . 4130 [RFC6364] Begen, A., "Session Description Protocol Elements for the 4131 Forward Error Correction (FEC) Framework", RFC 6364, DOI 4132 10.17487/RFC6364, October 2011, 4133 . 4135 [RFC6642] Wu, Q., Ed., Xia, F., and R. Even, "RTP Control Protocol 4136 (RTCP) Extension for a Third-Party Loss Report", RFC 6642, 4137 DOI 10.17487/RFC6642, June 2012, 4138 . 4140 [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., 4141 and K. Carlberg, "Explicit Congestion Notification (ECN) 4142 for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August 4143 2012, . 4145 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection 4146 Establishment for Media Anchoring (CEMA) for the Message 4147 Session Relay Protocol (MSRP)", RFC 6714, DOI 10.17487/ 4148 RFC6714, August 2012, 4149 . 4151 [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A 4152 Datagram Congestion Control Protocol UDP Encapsulation for 4153 NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November 4154 2012, . 4156 [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control 4157 Protocol Version 2 (MRCPv2)", RFC 6787, DOI 10.17487/ 4158 RFC6787, November 2012, 4159 . 4161 [RFC6849] Kaplan, H., Ed., Hedayat, K., Venna, N., Jones, P., and N. 4162 Stratton, "An Extension to the Session Description 4163 Protocol (SDP) and Real-time Transport Protocol (RTP) for 4164 Media Loopback", RFC 6849, DOI 10.17487/RFC6849, February 4165 2013, . 4167 [RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session 4168 Description Protocol (SDP) Media Capabilities 4169 Negotiation", RFC 6871, DOI 10.17487/RFC6871, February 4170 2013, . 4172 [RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S. 4173 Veikkolainen, "The Session Description Protocol (SDP) 4174 Alternate Connectivity (ALTC) Attribute", RFC 6947, DOI 4175 10.17487/RFC6947, May 2013, 4176 . 4178 [RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman, 4179 "Miscellaneous Capabilities Negotiation in the Session 4180 Description Protocol (SDP)", RFC 7006, DOI 10.17487/ 4181 RFC7006, September 2013, 4182 . 4184 [RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping 4185 Semantics in the Session Description Protocol", RFC 7104, 4186 DOI 10.17487/RFC7104, January 2014, 4187 . 4189 [RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session 4190 Description Protocol (SDP) Extension for Setting Audio and 4191 Video Media Streams over Circuit-Switched Bearers in the 4192 Public Switched Telephone Network (PSTN)", RFC 7195, DOI 4193 10.17487/RFC7195, May 2014, 4194 . 4196 [RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay 4197 Attribute in the Session Description Protocol", RFC 7197, 4198 DOI 10.17487/RFC7197, April 2014, 4199 . 4201 [RFC7266] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control 4202 Protocol (RTCP) Extended Report (XR) Blocks for Mean 4203 Opinion Score (MOS) Metric Reporting", RFC 7266, DOI 4204 10.17487/RFC7266, June 2014, 4205 . 4207 [RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O., 4208 Boronat, F., Montagud, M., and K. Gross, "Inter- 4209 Destination Media Synchronization (IDMS) Using the RTP 4210 Control Protocol (RTCP)", RFC 7272, DOI 10.17487/RFC7272, 4211 June 2014, . 4213 [RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H. 4214 Stokking, "RTP Clock Source Signalling", RFC 7273, DOI 4215 10.17487/RFC7273, June 2014, 4216 . 4218 [RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services 4219 (Diffserv) and Real-Time Communication", RFC 7657, DOI 4220 10.17487/RFC7657, November 2015, 4221 . 4223 [T.38] "Procedures for real-time Group 3 facsimile communication 4224 over IP networks", . 4226 Author's Address 4228 Suhas Nandakumar 4229 Cisco 4230 170 West Tasman Drive 4231 San Jose, CA 95134 4232 USA 4234 Email: snandaku@cisco.com