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2 Network Working Group S. Nandakumar
3 Internet-Draft Cisco
4 Intended status: Standards Track November 26, 2014
5 Expires: May 30, 2015
7 A Framework for SDP Attributes when Multiplexing
8 draft-ietf-mmusic-sdp-mux-attributes-05
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. In the RTCWEB WG, there is a need to use a
16 single 5-tuple for sending and receiving media associated with
17 multiple media descriptions ("m=" lines). Such a requirement has
18 raised concerns over the semantic implications of the SDP attributes
19 associated with the RTP Media Streams multiplexed over a single
20 underlying transport layer flow.
22 The scope of this specification is to provide a framework for
23 analyzing the multiplexing characteristics of SDP attributes. This
24 specification also categorizes the existing SDP attributes based on
25 the framework described herein.
27 Status of This Memo
29 This Internet-Draft is submitted in full conformance with the
30 provisions of BCP 78 and BCP 79.
32 Internet-Drafts are working documents of the Internet Engineering
33 Task Force (IETF). Note that other groups may also distribute
34 working documents as Internet-Drafts. The list of current Internet-
35 Drafts is at http://datatracker.ietf.org/drafts/current/.
37 Internet-Drafts are draft documents valid for a maximum of six months
38 and may be updated, replaced, or obsoleted by other documents at any
39 time. It is inappropriate to use Internet-Drafts as reference
40 material or to cite them other than as "work in progress."
42 This Internet-Draft will expire on May 30, 2015.
44 Copyright Notice
46 Copyright (c) 2014 IETF Trust and the persons identified as the
47 document authors. All rights reserved.
49 This document is subject to BCP 78 and the IETF Trust's Legal
50 Provisions Relating to IETF Documents
51 (http://trustee.ietf.org/license-info) in effect on the date of
52 publication of this document. Please review these documents
53 carefully, as they describe your rights and restrictions with respect
54 to this document. Code Components extracted from this document must
55 include Simplified BSD License text as described in Section 4.e of
56 the Trust Legal Provisions and are provided without warranty as
57 described in the Simplified BSD License.
59 This document may contain material from IETF Documents or IETF
60 Contributions published or made publicly available before November
61 10, 2008. The person(s) controlling the copyright in some of this
62 material may not have granted the IETF Trust the right to allow
63 modifications of such material outside the IETF Standards Process.
64 Without obtaining an adequate license from the person(s) controlling
65 the copyright in such materials, this document may not be modified
66 outside the IETF Standards Process, and derivative works of it may
67 not be created outside the IETF Standards Process, except to format
68 it for publication as an RFC or to translate it into languages other
69 than English.
71 Table of Contents
73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
74 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
75 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 6
76 4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . 6
77 4.1. Category: NORMAL . . . . . . . . . . . . . . . . . . . . 7
78 4.2. Category: NOT RECOMMENDED . . . . . . . . . . . . . . . . 7
79 4.3. Category: IDENTICAL . . . . . . . . . . . . . . . . . . . 8
80 4.4. Category: SUM . . . . . . . . . . . . . . . . . . . . . . 8
81 4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 9
82 4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 10
83 4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 10
84 4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 11
85 4.9. Category: TBD . . . . . . . . . . . . . . . . . . . . . . 11
86 5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 12
87 5.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 12
88 5.2. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 14
89 5.3. RFC5761 - Multiplexing RTP and RTCP . . . . . . . . . . . 14
90 5.4. RFC3312 - Integration of Resource Management and (SIP) . 14
91 5.5. RFC4574 - SDP Label Attribute . . . . . . . . . . . . . . 15
92 5.6. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 15
93 5.7. RFC4568 - SDP Security Descriptions . . . . . . . . . . . 16
94 5.8. RFC5762 - RTP over DCCP . . . . . . . . . . . . . . . . . 16
95 5.9. RFC6773 - DCCP-UDP Encapsulation . . . . . . . . . . . . 17
96 5.10. RFC5506 - Reduced-Size RTCP in RTP Profile . . . . . . . 18
97 5.11. RFC6787 - Media Resource Control Protocol Version 2 . . . 18
98 5.12. RFC5245 - Interactive Connectivity Establishment (ICE) . 19
99 5.13. RFC5285 - RTP Header Extensions . . . . . . . . . . . . . 21
100 5.14. RFC3605 - RTCP attribute in SDP . . . . . . . . . . . . . 21
101 5.15. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 21
102 5.16. RFC7273 - RTP Clock Source Signalling . . . . . . . . . . 22
103 5.17. RFC6236 - Image Attributes in SDP . . . . . . . . . . . . 23
104 5.18. RFC7197 - Duplication Delay Attribute in SDP . . . . . . 23
105 5.19. RFC7266 - RTCP XR Blocks for MOS Metric Reporting . . . 23
106 5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions . . 24
107 5.21. RFC6230 - Media Control Channel Framework . . . . . . . . 24
108 5.22. RFC6364 - SDP Elements for FEC Framework . . . . . . . . 25
109 5.23. RFC4796 - Content Attribute . . . . . . . . . . . . . . . 25
110 5.24. RFC3407 - SDP Simple Capability Declaration . . . . . . . 26
111 5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP
112 Sessions . . . . . . . . . . . . . . . . . . . . . . . . 26
113 5.26. RFC6714 - MSRP-CEMA . . . . . . . . . . . . . . . . . . . 27
114 5.27. RFC4583 - SDP Format for BFCP Streams . . . . . . . . . . 27
115 5.28. RFC5547 - SDP Offer/Answer for File Transfer . . . . . . 28
116 5.29. RFC6849 - SDP and RTP Media Loopback Extension . . . . . 28
117 5.30. RFC5760 - RTCP with Unicast Feedback . . . . . . . . . . 29
118 5.31. RFC3611 - RTCP XR . . . . . . . . . . . . . . . . . . . . 29
119 5.32. RFC5939 - SDP Capability Negotiation . . . . . . . . . . 29
120 5.33. RFC6871- SDP Media Capabilities Negotiation . . . . . . . 30
121 5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP . . 31
122 5.35. RFC4567 - Key Management Extensions for SDP and RTSP . . 32
123 5.36. RFC4572 - Comedia over TLS in SDP . . . . . . . . . . . . 33
124 5.37. RFC4570 - SDP Source Filters . . . . . . . . . . . . . . 33
125 5.38. RFC6128 - RTCP Port for Multicast Sessions . . . . . . . 34
126 5.39. RFC6189 - ZRTP . . . . . . . . . . . . . . . . . . . . . 34
127 5.40. RFC4145 - Connection-Oriented Media . . . . . . . . . . . 35
128 5.41. RFC6947 - The SDP ALTC Attribute . . . . . . . . . . . . 35
129 5.42. RFC7195 - SDP Extension for Circuit Switched Bearers
130 in PSTN . . . . . . . . . . . . . . . . . . . . . . . . . 35
131 5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP) . . 36
132 5.44. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . 36
133 5.45. RFC6193 - Media Description for IKE in SDP . . . . . . . 37
134 5.46. RFC2326 - Real Time Streaming Protocol . . . . . . . . . 38
135 5.47. RFC6064 - SDP and RTSP Extensions for 3GPP . . . . . . . 38
136 5.48. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . . 41
137 5.49. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 42
138 5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . . 43
139 5.51. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 43
140 5.52. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 44
141 5.53. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 44
142 5.54. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 45
143 5.55. ITU-T-REC.Q1970 . . . . . . . . . . . . . . . . . . . . . 46
144 5.56. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 47
145 5.57. RFC4975 - The Message Session Relay Protocol . . . . . . 47
146 5.58. Historical Attributes . . . . . . . . . . . . . . . . . . 48
147 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 48
148 6.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 48
149 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . 49
150 6.3. RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . 49
151 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 50
152 7.1. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 50
153 7.2. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 51
154 7.3. RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . 52
155 7.4. RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . . 52
156 7.5. RFC6642 - Third-Party Loss Report . . . . . . . . . . . . 53
157 7.6. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 54
158 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 54
159 8.1. RFC5888 - SDP Grouping Framework . . . . . . . . . . . . 54
160 8.2. RFC3524 - Mapping Media Streams to Resource
161 Reservation Flows . . . . . . . . . . . . . . . . . . . . 55
162 8.3. RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . 55
163 8.4. RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . . 55
164 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP . . 56
165 8.6. RFC7104 - Duplication Grouping Semantics in the SDP . . 56
166 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 57
167 9.1. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 57
168 9.2. RFC7104 - Duplication Grouping Semantics in the SDP . . . 57
169 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 57
170 10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 57
171 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 58
172 11.1. RFC4566 SDP: Session Description Protocol . . . . . . . 58
173 12. content Attribute Analysis . . . . . . . . . . . . . . . . . 58
174 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 58
175 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 59
176 13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . 59
177 14. Multiplexing Considerations for Encapsulating Attributes . . 59
178 14.1. RFC3407 - cpar Attribute Analysis . . . . . . . . . . . 60
179 14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 60
180 14.2.1. Recommendation - Procedures for Potential
181 Configuration Pairing . . . . . . . . . . . . . . . 61
182 14.2.1.1. Example: Transport Capability Multiplexing . . . 62
183 14.2.1.2. Example: Attribute Capability Multiplexing . . . 63
184 14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 64
185 14.3.1. Recommendation: Dealing with Payload Type Numbers . 64
186 14.3.1.1. Example: Attribute Capability Under Shared
187 Payload Type . . . . . . . . . . . . . . . . . . 64
188 14.3.2. Recommendation: Dealing with Latent Configurations . 65
189 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66
190 15.1. New 'Multiplexing Categories' subregistry . . . . . . . 66
191 15.2. 'Mux Category' column for subregistries . . . . . . . . 67
192 15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 67
193 15.2.2. Table: att-field (session level) . . . . . . . . . . 67
194 15.2.3. Table: att-field (both session and media level) . . 68
195 15.2.4. Table: att-field (media level only) . . . . . . . . 70
196 15.2.5. Table: att-field (source level) . . . . . . . . . . 73
197 15.2.6. Table: content SDP Parameters . . . . . . . . . . . 73
198 15.2.7. Table: Semantics for the 'group' SDP Attribute . . . 74
199 15.2.8. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 74
200 15.2.9. Table: 'ack' and 'nack' Attribute Values . . . . . . 75
201 15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . . 75
202 15.2.11. Table: 'cs-correlation' Attribute Values . . . . . . 75
203 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 76
204 15.2.13. Table: SDP/RTSP key management protocol identifiers 76
205 15.2.14. Table: Codec Control Messages . . . . . . . . . . . 76
206 15.2.15. Table: QoS Mechanism Tokens . . . . . . . . . . . . 77
207 15.2.16. Table: SDP Capability Negotiation Option Tags . . . 77
208 15.2.17. Table: Timestamp Reference Clock Source Parameters . 77
209 15.2.18. Table: Media Clock Source Parameters . . . . . . . . 78
210 16. Security Considerations . . . . . . . . . . . . . . . . . . . 78
211 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 78
212 18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 79
213 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 81
214 19.1. Normative References . . . . . . . . . . . . . . . . . . 81
215 19.2. Informative References . . . . . . . . . . . . . . . . . 81
216 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 88
218 1. Introduction
220 Real-Time Communication in WEB-browsers (Rtcweb) framework requires
221 Real-time Transport Protocol (RTP) as the media transport protocol
222 and Session Description Protocol (SDP) [RFC4566] for describing and
223 negotiating multi-media communication sessions.
225 SDP defines several attributes for capturing characteristics that
226 apply to the individual media descriptions (described by "m=" lines")
227 and the overall multimedia session. Typically different media types
228 (audio, video etc) described using different media descriptions
229 represent separate RTP Sessions that are carried over individual
230 transport layer flows. However in the IETF RTCWEB WG, a need to use
231 a single 5-tuple for sending and receiving media associated with
232 multiple SDP media descriptions ("m=" lines) has been identified.
233 This would for e.g. allow the usage of a single set of Interactive
234 Connectivity Establishment (ICE) [RFC5245] candidates for multiple
235 media descriptions. This in turn has made necessary to understand
236 the interpretation and usage of the SDP attributes defined for the
237 multiplexed media descriptions.
239 Given the number of SDP attributes registered with the [IANA] and
240 possibility of new attributes being defined in the future, there is
241 need for generic future-proof framework to analyze these attributes
242 for their applicability in the transport multiplexing use-cases.
244 The document starts with providing the motivation for requiring such
245 a framework. This is followed by introduction to the SDP attribute
246 analysis framework/procedures, following which several sections
247 applies the framework to the SDP attributes registered with the
248 [IANA].
250 2. Terminology
252 The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
253 "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
254 interpreted as described in [RFC2119].
256 3. Motivation
258 The time and complications of setting up ICE [RFC5245] and DTLS-SRTP
259 [RFC5763] transports for use by RTP, and conservation of ports, forms
260 an requirement to try and reduce the number of transport level flows
261 needed. This has resulted in the definition of ways, such as,
262 [I-D.ietf-mmusic-sdp-bundle-negotiation] to multiplex RTP over a
263 single transport flow in order to preserve network resources such as
264 port numbers. This imposes further restrictions on applicability of
265 these SDP attributes as they are defined today.
267 The specific problem is that there are attribute combinations which
268 make sense when specified on independent "m= " lines -- as with
269 classical SDP -- that do not make sense when those "m=" lines are
270 then multiplexed over the same transport. To give an obvious
271 example, ICE permits each "m=" line to have an independently
272 specified ice-ufrag attribute. However, if the media from multiple
273 "m=" lines is multiplexed over the same ICE component, then the
274 meaning of media-level ice-ufrag attributes becomes muddled.
276 As of today there are close to 250 SDP attributes registered with the
277 [IANA] and more will be added in the future. There is no clearly
278 defined procedure to establish the validity/applicability of these
279 attribute when used with transport 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. 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/
291 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 streams such
297 as grouping framework
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 recommended against multiplexing since their
330 usage under multiplexing might lead to incorrect behavior.
332 Example: Multiplexing media descriptions having attribute zrtp-hash
333 defined with the media descriptions lacking it, would either
334 complicate the handling of multiplexed streams or might fail
335 multiplexing altogether.
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=audio 3456 RTP/AVP 97 // with zrtp
343 a=rtpmap:97 iLBC/8000
344
345 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
346 df881ae642c371ba46df
347
348 m=video 34567 RTP/AVP 31 //without zrtp
349 a=rtpmap:31 H261/90000
351 4.3. Category: IDENTICAL
353 Attributes that MUST be identical across all the media descriptions
354 being multiplexed.
356 Attributes such as rtcp-mux fall into this category. Since RTCP
357 reporting is done per RTP Session, RTCP Multiplexing MUST be enabled
358 for both the audio and video m=lines if they are transported over a
359 single 5-tuple.
361 v=0
362 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
363 s=
364 c=IN IP4 client.biloxi.example.com
365 t=0 0
366 m=audio 34567 RTP/AVP 97
367 a=rtcp-mux
368 m=video 34567 RTP/AVP 31
369 a=rtpmap:31 H261/90000
370 a=rtcp-mux
372 4.4. Category: SUM
374 Attributes can be set as they are normally used but software using
375 them in the multiplexing scenario, MUST apply the sum of all the
376 attributes being multiplexed instead of trying to use them
377 independently. This is typically used for bandwidth or other rate
378 limiting attributes to the underlying transport.
380 The software parsing the SDP sample below, should use the aggregate
381 Application Specific (AS) bandwidth value from the individual media
382 descriptions to determine the AS value for the multiplexed session.
383 Thus the calculated AS value would be 256+64 bytes for the given
384 example.
386 v=0
387 o=test 2890844526 2890842807 IN IP4 126.16.64.4
388 c=IN IP4 client.biloxi.example.com
389 t=0 0
390 m=audio 49170 RTP/AVP 0
391 b=AS:64
392 m=video 51372 RTP/AVP 31
393 b=AS:256
395 4.5. Category: TRANSPORT
397 Attributes that can be set normally for multiple items in a
398 multiplexed group but the software MUST pick just one of the
399 attribute of the given type for use. The one chosen is the attribute
400 associated with the "m=" line that represents the information being
401 used for the transport of the RTP.
403 In the example below, "a=crypto" attribute is defined for both the
404 audio and the video m=lines. The video media line's a=crypto
405 attribute is chosen since its mid value (bar) appears first in the
406 a=group:BUNDLE line. This is due to BUNDLE grouping semantic
407 [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values
408 from m=line corresponding to the mid appearing first on the
409 a=group:BUNDLE line to be considered for setting up the RTP
410 Transport.
412 v=0
413 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
414 s=
415 c=IN IP4 host.atlanta.example.com
416 t=0 0
417 a=group:BUNDLE bar foo
418 m=audio 49172 RTP/AVP 99
419 a=mid:foo
420 a=crypto:1 AES_CM_128_HMAC_SHA1_80
421 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32
422 a=rtpmap:99 iLBC/8000
423 m=video 51374 RTP/AVP 31
424 a=mid:bar
425 a=crypto:1 AES_CM_128_HMAC_SHA1_80
426 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
427 a=rtpmap:96 H261/90000
429 4.6. Category: INHERIT
431 Attributes that encapsulate other SDP attributes or parameters.
432 These attributes inherit their multiplexing characteristics from the
433 attributes or parameters they encapsulate. Such attributes as of
434 today, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of a
435 generic framework for indicating and negotiating transport, media and
436 media format related capabilities in the SDP.
438 The inheritance manifests itself when the encapsulated attribute or
439 parameter is being leveraged. In the case of SDP Capability
440 Negotiation [RFC5939] for example, this occurs when a capability
441 (encapsulating attribute) is used as part of a configuration; the
442 configuration inherits the multiplexing category of each of its
443 constituent (encapsulated) attributes and parameters. This in turn
444 may place constraints on what constitutes a valid configuration from
445 a multiplexing point of view, e.g. because some attributes must be
446 IDENTICAL (see Section 14 for further details).
448 v=0
449 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
450 s=
451 c=IN IP4 host.atlanta.example.com
452 t=0 0
453 m=video 3456 RTP/AVP 100
454 a=rtpmap:100 VP8/90000
455 a=fmtp:100 max-fr=30;max-fs=8040
456 a=sqn: 0
457 a=cdsc: 1 video RTP/AVP 100
458 a=cpar: a=rtcp-mux
459 m=video 3456 RTP/AVP 101
460 a=rtpmap:101 VP8/90000
461 a=fmtp:100 max-fr=15;max-fs=1200
462 a=cdsc: 2 video RTP/AVP 101
463 a=cpar: a=rtcp-mux
465 In the above example , the category IDENTICAL is inherited for the
466 cpar encapsulated rtcp-mux attribute.
468 4.7. Category: IDENTICAL-PER-PT
470 Attributes that define the RTP payload configuration on per Payload
471 Type basis and MUST have identical values across all the media
472 descriptions for a given RTP Payload Type when repeated. These
473 Payload Types identify the same codec configuration as defined in the
474 Section 10.1.2 of [I-D.ietf-mmusic-sdp-bundle-negotiation] under this
475 context.
477 In the SDP example below, Payload Types 96 and 97 are repeated across
478 all the video m= lines and all the payload specific parameters (ex:
479 rtpmap, fmtp) are identical.
481 v=0
482 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
483 s=
484 c=IN IP4 host.atlanta.example.com
485 t=0 0
486 a=group:BUNDLE cam1, cam2
487 m = video 96 97
488 a=mid:cam1
489 a=rtpmap:96 H264/90000
490 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
491 max-mbps=108000; max-br=1000
492 a=rtpmap:97 H264/90000
493 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
494 max-mbps=7200; max-br=200
495 m = video 96 97
496 a=mid:cam2
497 a=rtpmap:96 H264/90000
498 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
499 max-mbps=108000; max-br=1000
500 a=rtpmap:97 H264/90000
501 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
502 max-mbps=7200; max-br=200
504 4.8. Category: SPECIAL
506 Attributes where the text in the source draft must be consulted for
507 further handling when multiplexed.
509 As an example, for the attribute extmap, the specification defining
510 the extension MUST be referred to understand the multiplexing
511 implications.
513 4.9. Category: TBD
515 Attributes that have not been analyzed under the proposed
516 multiplexing framework yet. For the purposes of implementations it
517 is advised to consider "NOT RECOMMENDED" as the category when
518 multiplexing these attributes.
520 5. Analysis of Existing Attributes
522 This section analyzes attributes listed in [IANA], grouped under the
523 IETF document that defines them.
525 The "Level" column indicates whether the attribute is currently
526 specified as:
528 o S -- Session level
530 o M -- Media level
532 o B -- Both
534 o SR -- Source-level (for a single SSRC)
536 The "Mux Category" column identifies multiplexing category assigned
537 per attribute and the "Notes" column captures additional informative
538 details regarding the assigned category, wherever necessary.
540 5.1. RFC4566 - SDP: Session Description Protocol
542 [RFC4566] defines the Session Description Protocol (SDP) that is
543 intended for describing multimedia sessions for the purposes of
544 session announcement, session invitation, and other forms of
545 multimedia session initiation.
547 +-----------------+---------------------+-------+-------------------+
548 | Attr 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 | Attr | Notes | Level | Mux Category |
624 | Name | | | |
625 +----------+----------------------------+-------+-------------------+
626 | rtcp-fb | Since RTCP feedback | M | IDENTICAL-PER-PT |
627 | | attributes are Payload | | |
628 | | Type (PT) scoped, their | | |
629 | | values MUST be identical | | |
630 | | for a given PT across the | | |
631 | | multiplexed m=lines. | | |
632 | | | | |
633 +----------+----------------------------+-------+-------------------+
635 RFC4585 Attribute Analysis
637 5.3. RFC5761 - Multiplexing RTP and RTCP
639 [RFC5761] discusses issues that arise when multiplexing RTP data
640 packets and RTP Control Protocol (RTCP) packets on a single UDP port.
641 It describes when such multiplexing is and is not appropriate, and it
642 explains how the Session Description Protocol (SDP) can be used to
643 signal multiplexed sessions.
645 +-----------+----------------------------------+-------+------------+
646 | Name | Notes | Level | Mux |
647 | | | | Category |
648 +-----------+----------------------------------+-------+------------+
649 | rtcp-mux | RTP and RTCP Multiplexing | M | IDENTICAL |
650 | | affects the entire RTP Session | | |
651 | | | | |
652 +-----------+----------------------------------+-------+------------+
654 RFC5761 Attribute Analysis
656 5.4. RFC3312 - Integration of Resource Management and (SIP)
658 [RFC3312] defines a generic framework for preconditions, which are
659 extensible through IANA registration. This document also discusses
660 how network quality of service can be made a precondition for
661 establishment of sessions initiated by the Session Initiation
662 Protocol (SIP). These preconditions require that the participant
663 reserve network resources before continuing with the session.
665 +-------+-----------------------+-------+------------------+
666 | Name | Notes | Level | Mux Category |
667 +-------+-----------------------+-------+------------------+
668 | des | Refer to notes below | M | NOT RECOMMENDED |
669 | | | | |
670 | conf | Refer to notes below | M | NOT RECOMMENDED |
671 | | | | |
672 | curr | Refer to notes below | M | NOT RECOMMENDED |
673 | | | | |
674 +-------+-----------------------+-------+------------------+
676 RFC3312 Attribute Analysis
678 A mismatched set of preconditions across media descriptions results
679 in Session establishment failures due to inability in meeting the
680 right resource reservations requested.
682 5.5. RFC4574 - SDP Label Attribute
684 [RFC4574] defines a new Session Description Protocol (SDP) media-
685 level attribute: "label". The "label" attribute carries a pointer to
686 a media stream in the context of an arbitrary network application
687 that uses SDP. The sender of the SDP document can attach the "label"
688 attribute to a particular media stream or streams. The application
689 can then use the provided pointer to refer to each particular media
690 stream in its context.
692 +--------+---------------+-------+--------------+
693 | Name | Notes | Level | Mux Category |
694 +--------+---------------+-------+--------------+
695 | label | Not Impacted | M | NORMAL |
696 | | | | |
697 +--------+---------------+-------+--------------+
699 RFC4574 Attribute Analysis
701 5.6. RFC5432 - QoS Mechanism Selection in SDP
703 [RFC5432] defines procedures to negotiate QOS mechanisms using the
704 Session Description Protocol (SDP) offer/answer model.
706 +----------------+------------------------+-------+--------------+
707 | Name | Notes | Level | Mux Category |
708 +----------------+------------------------+-------+--------------+
709 | qos-mech-send | Refer to notes below | B | NORMAL |
710 | | | | |
711 | qos-mech-recv | Refer to notes below. | B | NORMAL |
712 | | | | |
713 +----------------+------------------------+-------+--------------+
715 RFC5432 Attribute Analysis
717 A single DSCP code point per flow being multiplexed doesn't impact
718 multiplexing since QOS mechanisms are signaled/scoped per flow. For
719 scenarios that involves having different DSCP code points for packets
720 being transmitted over the same 5-tuple, issues as discussed in
721 [I.D-draft-ietf-dart-dscp-rtp] needs to be taken into consideration.
723 5.7. RFC4568 - SDP Security Descriptions
725 [RFC4568] defines a Session Description Protocol (SDP) cryptographic
726 attribute for unicast media streams. The attribute describes a
727 cryptographic key and other parameters that serve to configure
728 security for a unicast media stream in either a single message or a
729 roundtrip exchange.
731 +---------+------------------------------------+-------+------------+
732 | Name | Notes | Level | Mux |
733 | | | | Category |
734 +---------+------------------------------------+-------+------------+
735 | crypto | crypto attribute must be the one | M | TRANSPORT |
736 | | that corresponds to the "m=" line | | |
737 | | chosen for setting up the | | |
738 | | underlying transport flow | | |
739 | | | | |
740 +---------+------------------------------------+-------+------------+
742 RFC4568 Attribute Analysis
744 5.8. RFC5762 - RTP over DCCP
746 The Real-time Transport Protocol (RTP) is a widely used transport for
747 real-time multimedia on IP networks. The Datagram Congestion Control
748 Protocol (DCCP) is a transport protocol that provides desirable
749 services for real-time applications. [RFC5762] specifies a mapping
750 of RTP onto DCCP, along with associated signaling, such that real-
751 time applications can make use of the services provided by DCCP.
753 +--------------------+---------------------+---------+--------------+
754 | Name | Notes | Current | Mux Category |
755 +--------------------+---------------------+---------+--------------+
756 | dccp-service-code | If RFC6773 is not | M | NOT |
757 | | being used in | | RECOMMENDED |
758 | | addition to | | |
759 | | RFC5762, the port | | |
760 | | in the "m=" line is | | |
761 | | a DCCP port. DCCP | | |
762 | | being a connection | | |
763 | | oriented protocol, | | |
764 | | does not allow | | |
765 | | multiple | | |
766 | | connections on the | | |
767 | | same 5-tuple. | | |
768 | | | | |
769 +--------------------+---------------------+---------+--------------+
771 RFC5762 Attribute Analysis
773 If RFC6773 is being used in addition to RFC5762 and provided that
774 DCCP-in-UDP layer has additional demultiplexing, then it may be
775 possible to use different DCCP service codes for each DCCP flow,
776 given each uses a different DCCP port. Although doing so might
777 conflict with the media type of the "m=" line. None of this is
778 standardized yet and it wouldn't work as explained. Hence
779 multiplexing MUST NOT be performed even in this alternate scenario.
781 5.9. RFC6773 - DCCP-UDP Encapsulation
783 [RFC6773] document specifies an alternative encapsulation of the
784 Datagram Congestion Control Protocol (DCCP), referred to as DCCP-UDP.
785 This encapsulation allows DCCP to be carried through the current
786 generation of Network Address Translation (NAT) middle boxes without
787 modification of those middle boxes.
789 +------------+-------------------------------+-------+--------------+
790 | Name | Notes | Level | Mux Category |
791 +------------+-------------------------------+-------+--------------+
792 | dccp-port | Multiplexing MUST NOT be | M | NOT |
793 | | performed due to potential | | RECOMMENDED |
794 | | conflict between the port | | |
795 | | used for DCCP | | |
796 | | en/decapsulation and the RTP. | | |
797 | | | | |
798 +------------+-------------------------------+-------+--------------+
800 RFC6773 Attribute Analysis
802 Since RFC6773 is about tunneling DCCP in UDP, with the UDP port being
803 the port of the DCCP en-/de-capsulation service. This encapsulation
804 allows arbitrary DCCP packets to be encapsulated and the DCCP port
805 chosen MAY conflict with the port chosen for the RTP traffic.
807 For multiplexing several DCCP-in-UDP encapsulations on the same UDP
808 port, with no RTP traffic on the same port implies collapsing several
809 DCCP port spaces together. This MAY or MAY NOT work depending on the
810 nature of DCCP encapsulations and ports choses thus rendering it to
811 be very application dependent.
813 5.10. RFC5506 - Reduced-Size RTCP in RTP Profile
815 [RFC5506] discusses benefits and issues that arise when allowing
816 Real-time Transport Protocol (RTCP) packets to be transmitted with
817 reduced size.
819 +-------------+--------------------------------+-------+------------+
820 | Name | Notes | Level | Mux |
821 | | | | Category |
822 +-------------+--------------------------------+-------+------------+
823 | rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL |
824 | | entire RTP Session | | |
825 | | | | |
826 +-------------+--------------------------------+-------+------------+
828 RFC5506 Attribute Analysis
830 5.11. RFC6787 - Media Resource Control Protocol Version 2
832 The Media Resource Control Protocol Version 2 (MRCPv2) allows client
833 hosts to control media service resources such as speech synthesizers,
834 recognizers, verifiers, and identifiers residing in servers on the
835 network. MRCPv2 is not a "stand-alone" protocol -- it relies on
836 other protocols, such as the Session Initiation Protocol (SIP), to
837 coordinate MRCPv2 clients and servers and manage sessions between
838 them, and the Session Description Protocol (SDP) to describe,
839 discover, and exchange capabilities. It also depends on SIP and SDP
840 to establish the media sessions and associated parameters between the
841 media source or sink and the media server. Once this is done, the
842 MRCPv2 exchange operates over the control session established above,
843 allowing the client to control the media processing resources on the
844 speech resource server. [RFC6787] defines attributes for this
845 purpose.
847 +-----------+---------------+-------+--------------+
848 | Name | Notes | Level | Mux Category |
849 +-----------+---------------+-------+--------------+
850 | resource | Not Impacted | M | NORMAL |
851 | | | | |
852 | channel | Not Impacted | M | NORMAL |
853 | | | | |
854 | cmid | Not Impacted | M | NORMAL |
855 | | | | |
856 +-----------+---------------+-------+--------------+
858 RFC6787 Attribute Analysis
860 5.12. RFC5245 - Interactive Connectivity Establishment (ICE)
862 [RFC5245] describes a protocol for Network Address Translator(NAT)
863 traversal for UDP-based multimedia sessions established with the
864 offer/answer model. This protocol is called Interactive Connectivity
865 Establishment (ICE). ICE makes use of the Session Traversal
866 Utilities for NAT (STUN) protocol and its extension,Traversal Using
867 Relay NAT (TURN). ICE can be used by any protocol utilizing the
868 offer/answer model, such as the Session Initiation Protocol (SIP).
870 +--------------------+-------------------------+-------+------------+
871 | Name | Notes | Level | Mux |
872 | | | | Category |
873 +--------------------+-------------------------+-------+------------+
874 | ice-lite | Not Impacted | S | NORMAL |
875 | | | | |
876 | ice-options | Not Impacted | S | NORMAL |
877 | | | | |
878 | ice-mismatch | Not Impacted | S | NORMAL |
879 | | | | |
880 | ice-pwd | ice-pwd MUST be the one | B | TRANSPORT |
881 | | that corresponds to the | | |
882 | | m=line chosen for | | |
883 | | setting up the | | |
884 | | underlying transport | | |
885 | | flow | | |
886 | | | | |
887 | ice-ufrag | ice-ufrag MUST be the | B | TRANSPORT |
888 | | one that corresponds to | | |
889 | | the m=line chosen for | | |
890 | | setting up the | | |
891 | | underlying transport | | |
892 | | flow | | |
893 | | | | |
894 | candidate | ice candidate MUST be | M | TRANSPORT |
895 | | the one that | | |
896 | | corresponds to the | | |
897 | | m=line chosen for | | |
898 | | setting up the | | |
899 | | underlying transport | | |
900 | | flow | | |
901 | | | | |
902 | remote-candidates | ice remote candidate | M | TRANSPORT |
903 | | MUST be the one that | | |
904 | | corresponds to the | | |
905 | | m=line chosen for | | |
906 | | setting up the | | |
907 | | underlying transport | | |
908 | | flow | | |
909 | | | | |
910 +--------------------+-------------------------+-------+------------+
912 RFC5245 Attribute Analysis
914 5.13. RFC5285 - RTP Header Extensions
916 [RFC5285] provides a general mechanism to use the header extension
917 feature of RTP (the Real-Time Transport Protocol). It provides the
918 option to use a small number of small extensions in each RTP packet,
919 where the universe of possible extensions is large and registration
920 is de-centralized. The actual extensions in use in a session are
921 signaled in the setup information for that session.
923 +---------+-------------------------------------+-------+-----------+
924 | Name | Notes | Level | Mux |
925 | | | | Category |
926 +---------+-------------------------------------+-------+-----------+
927 | extmap | Specific RTP extension document | B | SPECIAL |
928 | | MUST be referred | | |
929 | | | | |
930 +---------+-------------------------------------+-------+-----------+
932 RFC5285 Attribute Analysis
934 5.14. RFC3605 - RTCP attribute in SDP
936 Originally, SDP assumed that RTP and RTCP were carried on consecutive
937 ports. However, this is not always true when NATs are involved.
938 [RFC3605] specifies an early mechanism to indicate the RTCP port.
940 +-------+--------------------------------------+-------+------------+
941 | Name | Notes | Level | Mux |
942 | | | | Category |
943 +-------+--------------------------------------+-------+------------+
944 | rtcp | Identical attribute value MUST be | M | IDENTICAL |
945 | | used since the RTCP port affects the | | |
946 | | entire RTP session. | | |
947 | | | | |
948 +-------+--------------------------------------+-------+------------+
950 RFC3605 Attribute Analysis
952 5.15. RFC5576 - Source-Specific SDP Attributes
954 [RFC5576] defines a mechanism to describe RTP media sources, which
955 are identified by their synchronization source (SSRC) identifiers, in
956 SDP, to associate attributes with these sources, and to express
957 relationships among sources. It also defines several source-level
958 attributes that can be used to describe properties of media sources.
960 +----------------+----------------------+-------+-------------------+
961 | Name | Notes | Level | Mux Category |
962 +----------------+----------------------+-------+-------------------+
963 | ssrc | Refer to Notes below | M | NORMAL |
964 | | | | |
965 | ssrc-group | Refer to section | M | NORMAL |
966 | | Section 9 for | | |
967 | | specific analysis of | | |
968 | | the grouping | | |
969 | | semantics | | |
970 | | | | |
971 | cname | Not Impacted | SR | NORMAL |
972 | | | | |
973 | previous-ssrc | Refer to notes below | SR | NORMAL |
974 | | | | |
975 | fmtp | The attribute value | SR | IDENTICAL-PER-PT |
976 | | must be same for a | | |
977 | | given codec | | |
978 | | configuration | | |
979 | | | | |
980 +----------------+----------------------+-------+-------------------+
982 RFC5576 Attribute Analysis
984 If SSRCs are repeated across m=lines being multiplexed, they MUST all
985 represent the same underlying RTP Source.
987 5.16. RFC7273 - RTP Clock Source Signalling
989 [RFC7273] specifies Session Description Protocol (SDP) signalling
990 that identifies timestamp reference clock sources and SDP signalling
991 that identifies the media clock sources in a multimedia session.
993 +------------+---------------+-------+--------------+
994 | Name | Notes | Level | Mux Category |
995 +------------+---------------+-------+--------------+
996 | ts-refclk | Not Impacted | B | NORMAL |
997 | | | | |
998 | mediaclk | Not Impacted | B | NORMAL |
999 | | | | |
1000 +------------+---------------+-------+--------------+
1002 RFC7273 Attribute Analysis
1004 5.17. RFC6236 - Image Attributes in SDP
1006 [RFC6236] proposes a new generic session setup attribute to make it
1007 possible to negotiate different image attributes such as image size.
1008 A possible use case is to make it possible for a low-end hand-held
1009 terminal to display video without the need to rescale the
1010 image,something that may consume large amounts of memory and
1011 processing power. The document also helps to maintain an optimal
1012 bitrate for video as only the image size that is desired by the
1013 receiver is transmitted.
1015 +------------+--------------------------+-------+-------------------+
1016 | Name | Notes | Level | Mux Category |
1017 +------------+--------------------------+-------+-------------------+
1018 | imageattr | The attribute value must | M | IDENTICAL-PER-PT |
1019 | | be same for a given | | |
1020 | | codec configuration | | |
1021 | | | | |
1022 +------------+--------------------------+-------+-------------------+
1024 RFC6236 Attribute Analysis
1026 5.18. RFC7197 - Duplication Delay Attribute in SDP
1028 [RFC7197] defines an attribute to indicate the presence of temporally
1029 redundant media streams and the duplication delay in the Session
1030 Description Protocol.
1032 +--------------------+---------------+-------+--------------+
1033 | Name | Notes | Level | Mux Category |
1034 +--------------------+---------------+-------+--------------+
1035 | duplication-delay | Not Impacted | B | NORMAL |
1036 | | | | |
1037 +--------------------+---------------+-------+--------------+
1039 RFC7197 Attribute Analysis
1041 5.19. RFC7266 - RTCP XR Blocks for MOS Metric Reporting
1043 [RFC7266] defines an RTP Control Protocol (RTCP) Extended Report (XR)
1044 Block including two new segment types and associated Session
1045 Description Protocol (SDP) parameters that allow the reporting of
1046 mean opinion score (MOS) Metrics for use in a range of RTP
1047 applications.
1049 +-------------+---------------+-------+--------------+
1050 | Name | Notes | Level | Mux Category |
1051 +-------------+---------------+-------+--------------+
1052 | calgextmap | Not Impacted | B | NORMAL |
1053 | | | | |
1054 +-------------+---------------+-------+--------------+
1056 RFC7266 Attribute Analysis
1058 5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions
1060 [RFC6285] describes a method using the existing RTP and RTP Control
1061 Protocol (RTCP) machinery that reduces the acquisition delay. In
1062 this method, an auxiliary unicast RTP session carrying the Reference
1063 Information to the receiver precedes or accompanies the multicast
1064 stream. This unicast RTP flow can be transmitted at a faster than
1065 natural bitrate to further accelerate the acquisition. The
1066 motivating use case for this capability is multicast applications
1067 that carry real-time compressed audio and video.
1069 +---------------+-------------------+-------+------------------+
1070 | Name | Notes | Level | Mux Category |
1071 +---------------+-------------------+-------+------------------+
1072 | rams-updates | Not recommended | M | NOT RECOMMENDED |
1073 | | | | |
1074 +---------------+-------------------+-------+------------------+
1076 RFC6285 Attribute Analysis
1078 5.21. RFC6230 - Media Control Channel Framework
1080 [RFC6230] describes a framework and protocol for application
1081 deployment where the application programming logic and media
1082 processing are distributed. This implies that application
1083 programming logic can seamlessly gain access to appropriate resources
1084 that are not co-located on the same physical network entity. The
1085 framework uses the Session Initiation Protocol (SIP) to establish an
1086 application-level control mechanism between application servers and
1087 associated external servers such as media servers.
1089 +---------+-----------------+-------+--------------+
1090 | Name | Notes | Level | Mux Category |
1091 +---------+-----------------+-------+--------------+
1092 | cfw-id | Not Applicable | M | NORMAL |
1093 | | | | |
1094 +---------+-----------------+-------+--------------+
1096 RFC6230 Attribute Analysis
1098 5.22. RFC6364 - SDP Elements for FEC Framework
1100 [RFC6364] specifies the use of the Session Description Protocol (SDP)
1101 to describe the parameters required to signal the Forward Error
1102 Correction (FEC) Framework Configuration Information between the
1103 sender(s) and receiver(s). This document also provides examples that
1104 show the semantics for grouping multiple source and repair flows
1105 together for the applications that simultaneously use multiple
1106 instances of the FEC Framework.
1108 +------------------+-----------------------------+-------+----------+
1109 | Name | Notes | Level | Mux |
1110 | | | | Category |
1111 +------------------+-----------------------------+-------+----------+
1112 | fec-source-flow | Specific FEC scheme | M | SPECIAL |
1113 | | document needs to be | | |
1114 | | referred | | |
1115 | | | | |
1116 | fec-repair-flow | Specific FEC scheme | M | SPECIAL |
1117 | | document needs to be | | |
1118 | | referred | | |
1119 | | | | |
1120 | repair-window | Specific FEC scheme | M | SPECIAL |
1121 | | document needs to be | | |
1122 | | referred | | |
1123 | | | | |
1124 +------------------+-----------------------------+-------+----------+
1126 RFC6364 Attribute Analysis
1128 5.23. RFC4796 - Content Attribute
1130 [RFC4796] defines a new Session Description Protocol (SDP) media-
1131 level attribute, 'content'. The 'content' attribute defines the
1132 content of the media stream to a more detailed level than the media
1133 description line. The sender of an SDP session description can
1134 attach the 'content' attribute to one or more media streams. The
1135 receiving application can then treat each media stream differently
1136 (e.g., show it on a big or small screen) based on its content.
1138 +----------+---------------+-------+--------------+
1139 | Name | Notes | Level | Mux Category |
1140 +----------+---------------+-------+--------------+
1141 | content | Not Impacted | M | NORMAL |
1142 | | | | |
1143 +----------+---------------+-------+--------------+
1145 RFC4796 Attribute Analysis
1147 5.24. RFC3407 - SDP Simple Capability Declaration
1149 [RFC3407] defines a set of Session Description Protocol (SDP)
1150 attributes that enables SDP to provide a minimal and backwards
1151 compatible capability declaration mechanism.
1153 +----------+------------------------+-------+--------------+
1154 | Name | Notes | Level | Mux Category |
1155 +----------+------------------------+-------+--------------+
1156 | sqn | Not Impacted | B | NORMAL |
1157 | | | | |
1158 | cdsc | Not Impacted. | B | NORMAL |
1159 | | | | |
1160 | cpar | Refer to Section 14 | B | INHERIT |
1161 | | | | |
1162 | cparmin | Refer to notes below | B | SPECIAL |
1163 | | | | |
1164 | cparmax | Refer to notes below | B | SPECIAL |
1165 | | | | |
1166 +----------+------------------------+-------+--------------+
1168 RFC3407 Attribute Analysis
1170 Since the attributes (a=cparmin and a=cparmax) define minimum and
1171 maximum numerical values associated with the attributes described in
1172 a=cpar, it is recommended to consult the document defining the
1173 attribute.
1175 5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions
1177 [RFC6284] presents a port mapping solution that allows RTP receivers
1178 to choose their own ports for an auxiliary unicast session in RTP
1179 applications using both unicast and multicast services. The solution
1180 provides protection against denial-of-service or packet amplification
1181 attacks that could be used to cause one or more RTP packets to be
1182 sent to a victim client.
1184 +------------------+-------------------------+-------+--------------+
1185 | Name | Notes | Level | Mux Category |
1186 +------------------+-------------------------+-------+--------------+
1187 | portmapping-req | Not recommended, if | M | NOT |
1188 | | port mapping is | | RECOMMENDED |
1189 | | required by the | | |
1190 | | application | | |
1191 | | | | |
1192 +------------------+-------------------------+-------+--------------+
1194 RFC6284 Attribute Analysis
1196 5.26. RFC6714 - MSRP-CEMA
1198 [RFC6714] defines a Message Session Relay Protocol (MSRP) extension,
1199 Connection Establishment for Media Anchoring (CEMA). Support of this
1200 extension is OPTIONAL. The extension allows middle boxes to anchor
1201 the MSRP connection, without the need for middle boxes to modify the
1202 MSRP messages; thus, it also enables secure end-to-end MSRP
1203 communication in networks where such middle boxes are deployed. This
1204 document also defines a Session Description Protocol (SDP) attribute,
1205 'msrp-cema', that MSRP endpoints use to indicate support of the CEMA
1206 extension.
1208 +------------+---------------+-------+--------------+
1209 | Name | Notes | Level | Mux Category |
1210 +------------+---------------+-------+--------------+
1211 | msrp-cema | Not Impacted | M | NORMAL |
1212 | | | | |
1213 +------------+---------------+-------+--------------+
1215 RFC6714 Attribute Analysis
1217 5.27. RFC4583 - SDP Format for BFCP Streams
1219 [RFC4583] document specifies how to describe Binary Floor Control
1220 Protocol (BFCP) streams in Session Description Protocol (SDP)
1221 descriptions. User agents using the offer/answer model to establish
1222 BFCP streams use this format in their offers and answers.
1224 +------------+---------------------------------+-------+------------+
1225 | Name | Notes | Level | Mux |
1226 | | | | Category |
1227 +------------+---------------------------------+-------+------------+
1228 | floorctrl | Must be repeated across all the | M | IDENTICAL |
1229 | | multiplexed m=lines | | |
1230 | | | | |
1231 | confid | Not Impacted | M | NORMAL |
1232 | | | | |
1233 | userid | Not Impacted | M | NORMAL |
1234 | | | | |
1235 | floorid | The floorid MUST be globally | M | NORMAL |
1236 | | unique | | |
1237 | | | | |
1238 +------------+---------------------------------+-------+------------+
1240 RFC4583 Attribute Analysis
1242 5.28. RFC5547 - SDP Offer/Answer for File Transfer
1244 [RFC5547] provides a mechanism to negotiate the transfer of one or
1245 more files between two endpoints by using the Session Description
1246 Protocol (SDP) offer/answer model specified in [RFC3264].
1248 +----------------------+---------------+-------+--------------+
1249 | Name | Notes | Level | Mux Category |
1250 +----------------------+---------------+-------+--------------+
1251 | file-selector | Not Impacted | M | NORMAL |
1252 | | | | |
1253 | file-transfer-id | Not Impacted | M | NORMAL |
1254 | | | | |
1255 | file-disposition | Not Impacted | M | NORMAL |
1256 | | | | |
1257 | file-date | Not Impacted | M | NORMAL |
1258 | | | | |
1259 | file-iconfile-range | Not Impacted | M | NORMAL |
1260 | | | | |
1261 +----------------------+---------------+-------+--------------+
1263 RFC5547 Attribute Analysis
1265 5.29. RFC6849 - SDP and RTP Media Loopback Extension
1267 [RFC6849] adds new SDP media types and attributes, which enable
1268 establishment of media sessions where the media is looped back to the
1269 transmitter. Such media sessions will serve as monitoring and
1270 troubleshooting tools by providing the means for measurement of more
1271 advanced VoIP, Real-time Text and Video over IP performance metrics.
1273 +---------------------------+----------------+-------+--------------+
1274 | Name | Notes | Level | Mux Category |
1275 +---------------------------+----------------+-------+--------------+
1276 | loopback rtp-pkt-loopback | Not Impacted | M | NORMAL |
1277 | | | | |
1278 | loopback rtp-media- | Not Impacted | M | NORMAL |
1279 | loopback | | | |
1280 | | | | |
1281 | loopback-source | Not Impacted | M | NORMAL |
1282 | | | | |
1283 | loopback-mirror | Not Impacted | M | NORMAL |
1284 | | | | |
1285 +---------------------------+----------------+-------+--------------+
1287 RFC6849 Analysis
1289 5.30. RFC5760 - RTCP with Unicast Feedback
1291 [RFC5760] specifies an extension to the Real-time Transport Control
1292 Protocol (RTCP) to use unicast feedback to a multicast sender. The
1293 proposed extension is useful for single-source multicast sessions
1294 such as Source-Specific Multicast (SSM) communication where the
1295 traditional model of many-to-many group communication is either not
1296 available or not desired.
1298 +---------------+------------------------------+-------+------------+
1299 | Name | Notes | Level | Mux |
1300 | | | | Category |
1301 +---------------+------------------------------+-------+------------+
1302 | rtcp-unicast | The attribute MUST be | M | IDENTICAL |
1303 | | reported across all m=lines | | |
1304 | | multiplexed | | |
1305 | | | | |
1306 +---------------+------------------------------+-------+------------+
1308 RFC5760 Attribute Analysis
1310 5.31. RFC3611 - RTCP XR
1312 [RFC3611] defines the Extended Report (XR) packet type for the RTP
1313 Control Protocol (RTCP), and defines how the use of XR packets can be
1314 signaled by an application if it employs the Session Description
1315 Protocol (SDP).
1317 +----------+---------------+-------+--------------+
1318 | Name | Notes | Level | Mux Category |
1319 +----------+---------------+-------+--------------+
1320 | rtcp-xr | Not Impacted | B | NORMAL |
1321 | | | | |
1322 +----------+---------------+-------+--------------+
1324 RFC3611 Attribute Analysis
1326 5.32. RFC5939 - SDP Capability Negotiation
1328 [RFC5939] defines a general SDP Capability Negotiation framework. It
1329 also specifies how to provide attributes and transport protocols as
1330 capabilities and negotiate them using the framework. Extensions for
1331 other types of capabilities (e.g., media types and media formats) may
1332 be provided in other documents.
1334 +---------+-------------------------------+-------+--------------+
1335 | Name | Notes | Level | Mux Category |
1336 +---------+-------------------------------+-------+--------------+
1337 | pcfg | Refer to Section Section 14 | M | SPECIAL |
1338 | | | | |
1339 | acfg | Refer to Section Section 14 | M | SPECIAL |
1340 | | | | |
1341 | csup | Not Impacted | B | NORMAL |
1342 | | | | |
1343 | creq | Not Impacted | B | NORMAL |
1344 | | | | |
1345 | acap | Refer to section Section 14 | B | INHERIT |
1346 | | | | |
1347 | tcap | Refer to section Section 14 | B | INHERIT |
1348 | | | | |
1349 | cap-v0 | Not Impacted | B | NORMAL |
1350 | | | | |
1351 +---------+-------------------------------+-------+--------------+
1353 RFC5939 Attribute Analysis
1355 5.33. RFC6871- SDP Media Capabilities Negotiation
1357 Session Description Protocol (SDP) capability negotiation provides a
1358 general framework for indicating and negotiating capabilities in SDP.
1359 The base framework defines only capabilities for negotiating
1360 transport protocols and attributes. [RFC6871] extends the framework
1361 by defining media capabilities that can be used to negotiate media
1362 types and their associated parameters.
1364 +---------+-----------------------------+-------+-------------------+
1365 | Name | Notes | Level | Mux Category |
1366 +---------+-----------------------------+-------+-------------------+
1367 | rmcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
1368 | | | | |
1369 | omcap | Not Impacted | B | NORMAL |
1370 | | | | |
1371 | mfcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
1372 | | | | |
1373 | mscap | Refer to Section Section 14 | B | INHERIT |
1374 | | | | |
1375 | lcfg | Refer to Section Section 14 | B | SPECIAL |
1376 | | | | |
1377 | sescap | Refer to notes below | S | NOT RECOMMENDED |
1378 | | | | |
1379 | med-v0 | Not Impacted | S | NORMAL |
1380 | | | | |
1381 +---------+-----------------------------+-------+-------------------+
1383 RFC6871 - Attribute Analysis
1385 The "sescap" attribute is NOT RECOMMENDED for use with multiplexing.
1386 The reason is that it requires the use of unique configuration
1387 numbers across the entire SDP (per [RFC6871]) as opposed to within a
1388 media description only (per [RFC5939]). As described in Section 14,
1389 the use of identical configuration numbers between multiplexed
1390 (bundled) media descriptions is the default way of indicating
1391 compatible configurations in a bundle.
1393 5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP
1395 [RFC7006] extends the SDP capability negotiation framework to allow
1396 endpoints to negotiate three additional SDP capabilities. In
1397 particular, this memo provides a mechanism to negotiate bandwidth
1398 ("b=" line), connection data ("c=" line), and session or media titles
1399 ("i=" line for each session or media).
1401 +----------+-----------------------------------+-------+------------+
1402 | Name | Notes | Level | Mux |
1403 | | | | Category |
1404 +----------+-----------------------------------+-------+------------+
1405 | bcap | Inherit the category SUM as | B | INHERIT |
1406 | | applicable to b= attribute | | |
1407 | | | | |
1408 | bcap-v0 | Not Impacted | B | NORMAL |
1409 | | | | |
1410 | ccap | The connection address type MUST | B | IDENTICAL |
1411 | | be identical across all the | | |
1412 | | multiplexed m= lines. | | |
1413 | | | | |
1414 | ccap-v0 | Not Impacted. | B | NORMAL |
1415 | | | | |
1416 | icap | Not Impacted | B | NORMAL |
1417 | | | | |
1418 | icap-v0 | Not Impacted | B | NORMAL |
1419 | | | | |
1420 +----------+-----------------------------------+-------+------------+
1422 RFC7006 - Attribute Analysis
1424 5.35. RFC4567 - Key Management Extensions for SDP and RTSP
1426 [RFC4567] defines general extensions for Session Description Protocol
1427 (SDP) and Real Time Streaming Protocol (RTSP) to carry messages, as
1428 specified by a key management protocol, in order to secure the media.
1429 These extensions are presented as a framework, to be used by one or
1430 more key management protocols. As such, their use is meaningful only
1431 when complemented by an appropriate key management protocol.
1433 +-----------+----------------------------------+-------+------------+
1434 | Name | Notes | Level | Mux |
1435 | | | | Category |
1436 +-----------+----------------------------------+-------+------------+
1437 | key-mgmt | Key management protocol MUST be | B | IDENTICAL |
1438 | | identical across all the m=lines | | |
1439 | | | | |
1440 | mikey | Key management protocol MUST be | B | IDENTICAL |
1441 | | identical across all the m=lines | | |
1442 | | | | |
1443 +-----------+----------------------------------+-------+------------+
1445 RFC4567 Attribute Analysis
1447 5.36. RFC4572 - Comedia over TLS in SDP
1449 [RFC4572] specifies how to establish secure connection-oriented media
1450 transport sessions over the Transport Layer Security (TLS) protocol
1451 using the Session Description Protocol (SDP). It defines a new SDP
1452 protocol identifier, 'TCP/TLS'. It also defines the syntax and
1453 semantics for an SDP 'fingerprint' attribute that identifies the
1454 certificate that will be presented for the TLS session. This
1455 mechanism allows media transport over TLS connections to be
1456 established securely, so long as the integrity of session
1457 descriptions is assured.
1459 +--------------+-------------------------------+-------+------------+
1460 | Name | Notes | Level | Mux |
1461 | | | | Category |
1462 +--------------+-------------------------------+-------+------------+
1463 | fingerprint | fingerprint value from the | B | TRANSPORT |
1464 | | m=line defining the | | |
1465 | | underlying transport is | | |
1466 | | chosen | | |
1467 | | | | |
1468 +--------------+-------------------------------+-------+------------+
1470 RFC4572 Attribute Analysis
1472 5.37. RFC4570 - SDP Source Filters
1474 [RFC4570] describes how to adapt the Session Description Protocol
1475 (SDP) to express one or more source addresses as a source filter for
1476 one or more destination "connection" addresses. It defines the
1477 syntax and semantics for an SDP "source-filter" attribute that may
1478 reference either IPv4 or IPv6 address(es) as either an inclusive or
1479 exclusive source list for either multicast or unicast destinations.
1480 In particular, an inclusive source-filter can be used to specify a
1481 Source-Specific Multicast (SSM) session.
1483 +----------------+-----------------------------+-------+------------+
1484 | Name | Notes | Level | Mux |
1485 | | | | Category |
1486 +----------------+-----------------------------+-------+------------+
1487 | source-filter | The attribute MUST be | B | IDENTICAL |
1488 | | repeated across all m=lines | | |
1489 | | multiplexed | | |
1490 | | | | |
1491 +----------------+-----------------------------+-------+------------+
1493 RFC4570 Attribute Analysis
1495 5.38. RFC6128 - RTCP Port for Multicast Sessions
1497 The Session Description Protocol (SDP) has an attribute that allows
1498 RTP applications to specify an address and a port associated with the
1499 RTP Control Protocol (RTCP) traffic. In RTP-based source-specific
1500 multicast (SSM) sessions, the same attribute is used to designate the
1501 address and the RTCP port of the Feedback Target in the SDP
1502 description. However, the RTCP port associated with the SSM session
1503 itself cannot be specified by the same attribute to avoid ambiguity,
1504 and thus, is required to be derived from the "m=" line of the media
1505 description. Deriving the RTCP port from the "m=" line imposes an
1506 unnecessary restriction. [RFC6128] removes this restriction by
1507 introducing a new SDP attribute.
1509 +-----------------+----------------------------+-------+------------+
1510 | Name | Notes | Level | Mux |
1511 | | | | Category |
1512 +-----------------+----------------------------+-------+------------+
1513 | multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL |
1514 | | be identical across all | | |
1515 | | the m=lines | | |
1516 | | | | |
1517 +-----------------+----------------------------+-------+------------+
1519 RFC6128 Attribute Analysis
1521 5.39. RFC6189 - ZRTP
1523 [RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman
1524 exchange to agree on a session key and parameters for establishing
1525 unicast Secure Real-time Transport Protocol (SRTP) sessions for Voice
1526 over IP (VoIP) applications.
1528 +------------+-------------------------------+-------+--------------+
1529 | Name | Notes | Level | Mux Category |
1530 +------------+-------------------------------+-------+--------------+
1531 | zrtp-hash | Complicates if all the | M | NOT |
1532 | | m=lines are not authenticated | | RECOMMENDED |
1533 | | as given in the example below | | |
1534 | | | | |
1535 +------------+-------------------------------+-------+--------------+
1537 RFC6189 Attribute Analysis
1539 5.40. RFC4145 - Connection-Oriented Media
1541 [RFC4145] describes how to express media transport over TCP using the
1542 Session Description Protocol (SDP). It defines the SDP 'TCP'
1543 protocol identifier, the SDP 'setup' attribute, which describes the
1544 connection setup procedure, and the SDP 'connection' attribute, which
1545 handles connection reestablishment.
1547 +-------------+--------------------------------+-------+------------+
1548 | Name | Notes | Level | Mux |
1549 | | | | Category |
1550 +-------------+--------------------------------+-------+------------+
1551 | setup | MUST be identical across all | B | IDENTICAL |
1552 | | m=lines | | |
1553 | | | | |
1554 | connection | MUST be identical across all | B | IDENTICAL |
1555 | | m=lines | | |
1556 | | | | |
1557 +-------------+--------------------------------+-------+------------+
1559 RFC4145 Attribute Analysis
1561 5.41. RFC6947 - The SDP ALTC Attribute
1563 [RFC6947] proposes a mechanism that allows the same SDP offer to
1564 carry multiple IP addresses of different address families (e.g., IPv4
1565 and IPv6). The proposed attribute, the "altc" attribute, solves the
1566 backward-compatibility problem that plagued Alternative Network
1567 Address Types (ANAT) due to their syntax.
1569 +-------+--------------------------------------+-------+------------+
1570 | Name | Notes | Level | Mux |
1571 | | | | Category |
1572 +-------+--------------------------------------+-------+------------+
1573 | altc | The IP Address and port must be the | M | TRANSPORT |
1574 | | one that corresponds to the m=line | | |
1575 | | chosen for setting up the underlying | | |
1576 | | transport flow. | | |
1577 | | | | |
1578 +-------+--------------------------------------+-------+------------+
1580 RFC6947 Attribute Analysis
1582 5.42. RFC7195 - SDP Extension for Circuit Switched Bearers in PSTN
1584 [RFC7195] describes use cases, requirements, and protocol extensions
1585 for using the Session Description Protocol (SDP) offer/answer model
1586 for establishing audio and video media streams over circuit-switched
1587 bearers in the Public Switched Telephone Network (PSTN).
1589 +--------------------------+----------------+-------+--------------+
1590 | Name | Notes | Level | Mux Category |
1591 +--------------------------+----------------+-------+--------------+
1592 | cs-correlation:callerid | Not Impacted. | M | NORMAL |
1593 | | | | |
1594 | cs-correlation:uuie | Not Impacted. | M | NORMAL |
1595 | | | | |
1596 | cs-correlation:dtmf | Not Impacted. | M | NORMAL |
1597 | | | | |
1598 | cs-correlation:external | Not Impacted. | M | NORMAL |
1599 | | | | |
1600 +--------------------------+----------------+-------+--------------+
1602 RFC7195 Attribute Analysis
1604 5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP)
1606 [RFC7272] defines a new RTP Control Protocol (RTCP) Packet Type and
1607 an RTCP Extended Report (XR) Block Type to be used for achieving
1608 Inter-Destination Media Synchronization (IDMS).
1610 +------------+----------------+-------+--------------+
1611 | Name | Notes | Level | Mux Category |
1612 +------------+----------------+-------+--------------+
1613 | rtcp-idms | Not Impacted. | M | NORMAL |
1614 | | | | |
1615 +------------+----------------+-------+--------------+
1617 RFC7272 Attribute Analysis
1619 5.44. RFC5159 - OMA BCAST SDP Attributes
1621 [RFC5159] provides descriptions of Session Description Protocol (SDP)
1622 attributes used by the Open Mobile Alliance's Broadcast Service and
1623 Content Protection specification.
1625 +---------------------+---------------+-------+--------------+
1626 | Name | Notes | Level | Mux Category |
1627 +---------------------+---------------+-------+--------------+
1628 | bcastversion | Not Impacted | S | NORMAL |
1629 | | | | |
1630 | stkmstream | Not Impacted | B | NORMAL |
1631 | | | | |
1632 | SRTPAuthentication | Not Impacted | M | NORMAL |
1633 | | | | |
1634 | SRTPROCTxRate | Not Impacted | M | NORMAL |
1635 | | | | |
1636 +---------------------+---------------+-------+--------------+
1638 RFC5159 Attribute Analysis
1640 5.45. RFC6193 - Media Description for IKE in SDP
1642 [RFC6193] specifies how to establish a media session that represents
1643 a virtual private network using the Session Initiation Protocol for
1644 the purpose of on-demand media/application sharing between peers. It
1645 extends the protocol identifier of the Session Description Protocol
1646 (SDP) so that it can negotiate use of the Internet Key Exchange
1647 Protocol (IKE) for media sessions in the SDP offer/answer model.
1649 +-------------------+--------------------------+-------+------------+
1650 | Name | Notes | Level | Mux |
1651 | | | | Category |
1652 +-------------------+--------------------------+-------+------------+
1653 | ike-setup | Attribute MUST be | B | IDENTICAL |
1654 | | identical across all the | | |
1655 | | m=lines | | |
1656 | | | | |
1657 | psk-fingerprint | Attribute MUST be | B | IDENTICAL |
1658 | | identical across all the | | |
1659 | | m=lines | | |
1660 | | | | |
1661 | ike-esp | Attribute MUST be | B | IDENTICAL |
1662 | | identical across all the | | |
1663 | | m=lines | | |
1664 | | | | |
1665 | ike-esp-udpencap | Attribute MUST be | B | IDENTICAL |
1666 | | identical across all the | | |
1667 | | m=lines | | |
1668 | | | | |
1669 +-------------------+--------------------------+-------+------------+
1671 RFC6193 Attribute Analysis
1673 With the above SDP constraints, a session multiplexed with multiple
1674 m=lines will use only one IPSec association for all of the m= lines.
1676 5.46. RFC2326 - Real Time Streaming Protocol
1678 The Real Time Streaming Protocol, or RTSP, is an application-level
1679 protocol for control over the delivery of data with real-time
1680 properties. RTSP provides an extensible framework to enable
1681 controlled, on-demand delivery of real-time data, such as audio and
1682 video.
1684 +----------+---------------------------------+-------+--------------+
1685 | Name | Notes | Level | Mux Category |
1686 +----------+---------------------------------+-------+--------------+
1687 | etag | RTSP is not supported for RTP | B | NOT |
1688 | | Stream multiplexing | | RECOMMENDED |
1689 | | | | |
1690 | range | RTSP is not supported for RTP | B | NOT |
1691 | | Stream multiplexing | | RECOMMENDED |
1692 | | | | |
1693 | control | RTSP is not supported for RTP | B | NOT |
1694 | | Stream multiplexing | | RECOMMENDED |
1695 | | | | |
1696 | mtag | RTSP is not supported for RTP | B | NOT |
1697 | | Stream multiplexing | | RECOMMENDED |
1698 | | | | |
1699 +----------+---------------------------------+-------+--------------+
1701 RFC2326 Attribute Analysis
1703 5.47. RFC6064 - SDP and RTSP Extensions for 3GPP
1705 The Packet-switched Streaming Service (PSS) and the Multimedia
1706 Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session
1707 Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
1708 with some extensions. [RFC6064] provides information about these
1709 extensions and registers the RTSP and SDP extensions with IANA.
1711 +-------------------------------+------------+-------+--------------+
1712 | Name | Notes | Level | Mux Category |
1713 +-------------------------------+------------+-------+--------------+
1714 | X-predecbufsize | Refer to | M | NOT |
1715 | | notes | | RECOMMENDED |
1716 | | below | | |
1717 | | | | |
1718 | X-initpredecbufperiod | Refer to | M | NOT |
1719 | | notes | | RECOMMENDED |
1720 | | below | | |
1721 | | | | |
1722 | X-initpostdecbufperiod | Refer to | M | NOT |
1723 | | notes | | RECOMMENDED |
1724 | | below | | |
1725 | | | | |
1726 | X-decbyterate | Refer to | M | NOT |
1727 | | notes | | RECOMMENDED |
1728 | | below | | |
1729 | | | | |
1730 | 3gpp-videopostdecbufsize | Refer to | M | NOT |
1731 | | notes | | RECOMMENDED |
1732 | | below | | |
1733 | | | | |
1734 | framesize | Refer to | M | NOT |
1735 | | notes | | RECOMMENDED |
1736 | | below | | |
1737 | | | | |
1738 | 3GPP-Integrity-Key | Refer to | S | NOT |
1739 | | notes | | RECOMMENDED |
1740 | | below | | |
1741 | | | | |
1742 | 3GPP-SDP-Auth | Refer to | S | NOT |
1743 | | notes | | RECOMMENDED |
1744 | | below | | |
1745 | | | | |
1746 | 3GPP-SRTP-Config | Refer to | M | NOT |
1747 | | notes | | RECOMMENDED |
1748 | | below | | |
1749 | | | | |
1750 | alt | Refer to | M | NOT |
1751 | | notes | | RECOMMENDED |
1752 | | below | | |
1753 | | | | |
1754 | alt-default-id | Refer to | M | NOT |
1755 | | notes | | RECOMMENDED |
1756 | | below | | |
1757 | | | | |
1758 | alt-group | Refer to | M | NOT |
1759 | | notes | | RECOMMENDED |
1760 | | below | | |
1761 | | | | |
1762 | 3GPP-Adaptation-Support | Refer to | M | NOT |
1763 | | notes | | RECOMMENDED |
1764 | | below | | |
1765 | | | | |
1766 | 3GPP-Asset-Information | Refer to | B | NOT |
1767 | | notes | | RECOMMENDED |
1768 | | below | | |
1769 | | | | |
1770 | mbms-mode | Refer to | B | NOT |
1771 | | notes | | RECOMMENDED |
1772 | | below | | |
1773 | | | | |
1774 | mbms-flowid | Refer to | M | NOT |
1775 | | notes | | RECOMMENDED |
1776 | | below | | |
1777 | | | | |
1778 | mbms-repair | Refer to | B | NOT |
1779 | | notes | | RECOMMENDED |
1780 | | below | | |
1781 | | | | |
1782 | 3GPP-QoE-Metrics | Refer to | M | NOT |
1783 | | notes | | RECOMMENDED |
1784 | | below | | |
1785 | | | | |
1786 | 3GPP-QoE-Metrics:Corruption | Refer to | M | NOT |
1787 | duration | notes | | RECOMMENDED |
1788 | | below | | |
1789 | | | | |
1790 | 3GPP-QoE-Metrics:Rebuffering | Refer to | M | NOT |
1791 | duration | notes | | RECOMMENDED |
1792 | | below | | |
1793 | | | | |
1794 | 3GPP-QoE-Metrics:Initial | Refer to | M | NOT |
1795 | buffering duration | notes | | RECOMMENDED |
1796 | | below | | |
1797 | | | | |
1798 | 3GPP-QoE-Metrics:Successive | Refer to | M | NOT |
1799 | loss of RTP packets | notes | | RECOMMENDED |
1800 | | below | | |
1801 | | | | |
1802 | 3GPP-QoE-Metrics:Frame rate | Refer to | M | NOT |
1803 | deviation | notes | | RECOMMENDED |
1804 | | below | | |
1805 | | | | |
1806 | 3GPP-QoE-Metrics:Jitter | Refer to | M | NOT |
1807 | duration | notes | | RECOMMENDED |
1808 | | below | | |
1809 | | | | |
1810 | 3GPP-QoE-Metrics:Content | Refer to | B | NOT |
1811 | Switch Time | notes | | RECOMMENDED |
1812 | | below | | |
1813 | | | | |
1814 | 3GPP-QoE-Metrics:Average | Refer to | M | NOT |
1815 | Codec Bitrate | notes | | RECOMMENDED |
1816 | | below | | |
1817 | | | | |
1818 | 3GPP-QoE-Metrics:Codec | Refer to | M | NOT |
1819 | Information | notes | | RECOMMENDED |
1820 | | below | | |
1821 | | | | |
1822 | 3GPP-QoE-Metrics:Buffer | Refer to | M | NOT |
1823 | Status | notes | | RECOMMENDED |
1824 | | below | | |
1825 | | | | |
1826 +-------------------------------+------------+-------+--------------+
1828 RFC6064 Attribute Analysis
1830 [RFC6064] defines SDP attributes that are applicable in the
1831 declarative usage of SDP alone. For purposes of this document, only
1832 the Offer/Answer usage of SDP is considered as mandated by
1833 [I-D.ietf-mmusic-sdp-bundle-negotiation].
1835 5.48. RFC3108 - ATM SDP
1837 RFC3108 [RFC3108] describes conventions for using the Session
1838 Description Protocol (SDP) described for controlling ATM Bearer
1839 Connections, and any associated ATM Adaptation Layer (AAL).
1841 +------------------------+--------------+-------+--------------+
1842 | Name | Notes | Level | Mux Category |
1843 +------------------------+--------------+-------+--------------+
1844 | aalType | Not Impacted | B | NORMAL |
1845 | eecid | Not Impacted | B | NORMAL |
1846 | aalType | Not Impacted | B | NORMAL |
1847 | capability | Not Impacted | B | NORMAL |
1848 | qosClass | Not Impacted | B | NORMAL |
1849 | bcob | Not Impacted | B | NORMAL |
1850 | stc | Not Impacted | B | NORMAL |
1851 | upcc | Not Impacted | B | NORMAL |
1852 | atmQOSparms | Not Impacted | B | NORMAL |
1853 | atmTrfcDesc | Not Impacted | B | NORMAL |
1854 | abrParms | Not Impacted | B | NORMAL |
1855 | abrSetup | Not Impacted | B | NORMAL |
1856 | bearerType | Not Impacted | B | NORMAL |
1857 | lij | Not Impacted | B | NORMAL |
1858 | anycast | Not Impacted | B | NORMAL |
1859 | cache | Not Impacted | B | NORMAL |
1860 | bearerSigIE | Not Impacted | B | NORMAL |
1861 | aalApp | Not Impacted | B | NORMAL |
1862 | cbrRate | Not Impacted | B | NORMAL |
1863 | sbc | Not Impacted | B | NORMAL |
1864 | clkrec | Not Impacted | B | NORMAL |
1865 | fec | Not Impacted | B | NORMAL |
1866 | prtfl | Not Impacted | B | NORMAL |
1867 | structure | Not Impacted | B | NORMAL |
1868 | cpsSDUsize | Not Impacted | B | NORMAL |
1869 | aal2CPS | Not Impacted | B | NORMAL |
1870 | aal2CPSSDUrate | Not Impacted | B | NORMAL |
1871 | aal2sscs3661unassured | Not Impacted | B | NORMAL |
1872 | aal2sscs3661assured | Not Impacted | B | NORMAL |
1873 | aal2sscs3662 | Not Impacted | B | NORMAL |
1874 | aal5sscop | Not Impacted | B | NORMAL |
1875 | atmmap | Not Impacted | B | NORMAL |
1876 | silenceSupp | Not Impacted | B | NORMAL |
1877 | ecan | Not Impacted | B | NORMAL |
1878 | gc | Not Impacted | B | NORMAL |
1879 | profileDesc | Not Impacted | B | NORMAL |
1880 | vsel | Not Impacted | B | NORMAL |
1881 | dsel | Not Impacted | B | NORMAL |
1882 | fsel | Not Impacted | B | NORMAL |
1883 | onewaySel | Not Impacted | B | NORMAL |
1884 | codecconfig | Not Impacted | B | NORMAL |
1885 | isup_usi | Not Impacted | B | NORMAL |
1886 | uiLayer1_Prot | Not Impacted | B | NORMAL |
1887 | chain | Not Impacted | B | NORMAL |
1888 | | | | |
1889 +------------------------+--------------+-------+--------------+
1891 RFC3108 Attribute Analysis
1893 RFC3108 describes conventions for using the Session Description
1894 Protocol (SDP) for characterizing ATM bearer connections using an
1895 AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5,
1896 bearer connections can be used to transport single media streams. In
1897 addition, for AAL1 and AAL2, multiple media streams may be
1898 multiplexed into a bearer connection. For all adaptation types
1899 (AAL1, AAL2 and AAL5), bearer connections may be bundled into a
1900 single media group. In all cases addressed by RFC3108, a real-time
1901 media stream (voice, video, voiceband data, pseudo-wire and others)
1902 or a multiplex of media streams is mapped directly into an ATM
1903 connection. RFC3108 does not address cases where ATM serves as a
1904 low-level transport pipe for IP packets which in turn may carry one
1905 or more real-time (e.g. VoIP) media sessions with a life-cycle
1906 different from that of the underlying ATM transport.
1908 5.49. 3GPP TS 26.114
1910 [R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and
1911 interaction
1912 +----------------------+-------------------------+-------+----------+
1913 | Name | Notes | Level | Mux |
1914 | | | | Category |
1915 +----------------------+-------------------------+-------+----------+
1916 | 3gpp_sync_info | Usage defined for the | M | NORMAL |
1917 | | IP Multimedia Subsystem | | |
1918 | | | | |
1919 | 3gpp_MaxRecvSDUSize | Usage defined for the | M | NORMAL |
1920 | | IP Multimedia Subsystem | | |
1921 | | | | |
1922 +----------------------+-------------------------+-------+----------+
1924 3GPP TS 26.114 Attribute Analysis
1926 5.50. 3GPP TS 183.063
1928 [R3GPPTS183.063] Telecommunications and Internet converged Services
1929 and Protocols for Advanced Networking (TISPAN);
1931 +---------------------+--------------+----------------+-------------+
1932 | Name | Notes | Level | Mux |
1933 | | | | Category |
1934 +---------------------+--------------+----------------+-------------+
1935 | PSCid | Not Impacted | Not-Applicable | NORMAL |
1936 | | | | |
1937 | bc_service | Not Impacted | Not-Applicable | NORMAL |
1938 | | | | |
1939 | bc_program | Not Impacted | Not-Applicable | NORMAL |
1940 | | | | |
1941 | bc_service_package | Not Impacted | Not-Applicable | NORMAL |
1942 | | | | |
1943 +---------------------+--------------+----------------+-------------+
1945 3GPP TS 183.063 Attribute Analysis
1947 5.51. 3GPP TS 24.182
1949 [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting
1950 tones
1951 +-------------+---------------------------------+-------+-----------+
1952 | Name | Notes | Level | Mux |
1953 | | | | Category |
1954 +-------------+---------------------------------+-------+-----------+
1955 | g.3gpp.cat | Usage defined for the IP | M | NORMAL |
1956 | | Multimedia Subsystem | | |
1957 | | | | |
1958 +-------------+---------------------------------+-------+-----------+
1960 3GPP TS 24.182 Attribute Analysis
1962 5.52. 3GPP TS 24.183
1964 [R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing
1965 Signal
1967 +-------------+---------------------------------+-------+-----------+
1968 | Name | Notes | Level | Mux |
1969 | | | | Category |
1970 +-------------+---------------------------------+-------+-----------+
1971 | g.3gpp.crs | Usage defined for the IP | M | NORMAL |
1972 | | Multimedia Subsystem | | |
1973 | | | | |
1974 +-------------+---------------------------------+-------+-----------+
1976 3GPP TS 24.183 Attribute Analysis
1978 5.53. 3GPP TS 24.229
1980 [R3GPPTS24.229] specifies IP multimedia call control protocol based
1981 on Session Initial protocol and Session Description Protocol.
1983 +------------------+---------------------------+-------+------------+
1984 | Name | Notes | Level | Mux |
1985 | | | | Category |
1986 +------------------+---------------------------+-------+------------+
1987 | secondary-realm | secondary-realm must be | M | TRANSPORT |
1988 | | the one that corresponds | | |
1989 | | to the m=line chosen for | | |
1990 | | setting up the underlying | | |
1991 | | transport flow. | | |
1992 | | | | |
1993 | visited-realm | visited-realm must be | M | TRANSPORT |
1994 | | the one that corresponds | | |
1995 | | to the m=line chosen for | | |
1996 | | setting up the underlying | | |
1997 | | transport flow. | | |
1998 | | | | |
1999 | omr-m-cksum | Not Impacted | M | NORMAL |
2000 | | | | |
2001 | omr-s-cksum | Not Impacted | M | NORMAL |
2002 | | | | |
2003 | omr-m-att | Not Impacted | M | NORMAL |
2004 | | | | |
2005 | omr-s-att | Not Impacted | M | NORMAL |
2006 | | | | |
2007 | omr-m-bw | Not Impacted | M | NORMAL |
2008 | | | | |
2009 | omr-s-bw | Not Impacted | M | NORMAL |
2010 | | | | |
2011 | omr-codecs | Not Impacted | M | NORMAL |
2012 | | | | |
2013 +------------------+---------------------------+-------+------------+
2015 3GPP TS 24.229 Attribute Analysis
2017 5.54. ITU T.38
2019 [T.38] defines procedures for real-time Group 3 facsimile
2020 communications over IP networks.
2022 +------------------------+---------------+-------+--------------+
2023 | Name | Notes | Level | Mux Category |
2024 +------------------------+---------------+-------+--------------+
2025 | T38FaxVersion | Not Impacted | S | NORMAL |
2026 | | | | |
2027 | T38MaxBitRate | Not Impacted | S | NORMAL |
2028 | | | | |
2029 | T38FaxFillBitRemoval | Not Impacted | S | NORMAL |
2030 | | | | |
2031 | T38FaxTranscodingMMR | Not Impacted | S | NORMAL |
2032 | | | | |
2033 | T38FaxTranscodingJBIG | Not Impacted | S | NORMAL |
2034 | | | | |
2035 | T38FaxRateManagement | Not Impacted | S | NORMAL |
2036 | | | | |
2037 | T38FaxMaxBuffer | Not Impacted | S | NORMAL |
2038 | | | | |
2039 | T38FaxMaxDatagram | Not Impacted | S | NORMAL |
2040 | | | | |
2041 | T38FaxUdpEC | Not Impacted | S | NORMAL |
2042 | | | | |
2043 | T38FaxMaxIFP | Not Impacted | S | NORMAL |
2044 | | | | |
2045 | T38FaxUdpECDepth | Not Impacted | S | NORMAL |
2046 | | | | |
2047 | T38FaxUdpFECMaxSpan | Not Impacted | S | NORMAL |
2048 | | | | |
2049 | T38ModemType | Not Impacted | S | NORMAL |
2050 | | | | |
2051 | T38VendorInfo | Not Impacted | S | NORMAL |
2052 | | | | |
2053 +------------------------+---------------+-------+--------------+
2055 ITU T.38 Attribute Analysis
2057 The ITU T.38 attributes are clearly unaffected by multiplexing and
2058 are specific to the working of the fax protocol itself.
2060 5.55. ITU-T-REC.Q1970
2062 [ITU-T-REC.Q1970] defines BICC IP bearer control protocol.
2064 +--------+---------------+-------+--------------+
2065 | Name | Notes | Level | Mux Category |
2066 +--------+---------------+-------+--------------+
2067 | ipbcp | Not Impacted | S | NORMAL |
2068 | | | | |
2069 +--------+---------------+-------+--------------+
2071 ITU-T-REC.Q1970 Attribute Analysis
2073 5.56. ITU-T H.248.15
2075 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248
2076 package attribute
2078 +-----------+------------------------------------+-------+----------+
2079 | Name | Notes | Level | Mux |
2080 | | | | Category |
2081 +-----------+------------------------------------+-------+----------+
2082 | h248item | It is only applicable for | B | SPECIAL |
2083 | | signaling the inclusion of H.248 | | |
2084 | | extension packages to a gateway | | |
2085 | | via the local and remote | | |
2086 | | descriptors. The attribute itself | | |
2087 | | is unaffected by multiplexing, but | | |
2088 | | the packaged referenced in a | | |
2089 | | specific use of the attribute may | | |
2090 | | be impacted. Further analysis of | | |
2091 | | each package is needed to | | |
2092 | | determine if there is an issue. | | |
2093 | | This is only a concern in | | |
2094 | | environments using a decomposed | | |
2095 | | server/gateway with H.248 signaled | | |
2096 | | between them. The ITU-T will need | | |
2097 | | to do further analysis of various | | |
2098 | | packages when they specify how to | | |
2099 | | signal the use of multiplexing to | | |
2100 | | a gateway. | | |
2101 | | | | |
2102 +-----------+------------------------------------+-------+----------+
2104 ITU-T H.248.15 Attribute Analysis
2106 5.57. RFC4975 - The Message Session Relay Protocol
2108 [RFC4975] the Message Session Relay Protocol, a protocol for
2109 transmitting a series of related instant messages in the context of a
2110 session. Message sessions are treated like any other media stream
2111 when set up via a rendezvous or session creation protocol such as the
2112 Session Initiation Protocol.
2114 +-----------------------+---------------+-------+--------------+
2115 | Name | Notes | Level | Mux Category |
2116 +-----------------------+---------------+-------+--------------+
2117 | accept-types | Not Impacted | M | NORMAL |
2118 | | | | |
2119 | accept-wrapped-types | Not Impacted | M | NORMAL |
2120 | | | | |
2121 | max-size | Not Impacted | M | NORMAL |
2122 | | | | |
2123 | path | Not Impacted | M | NORMAL |
2124 | | | | |
2125 +-----------------------+---------------+-------+--------------+
2127 RFC4975 Attribute Analysis
2129 5.58. Historical Attributes
2131 This section specifies analysis for the attributes that are included
2132 for historic usage alone by the [IANA].
2134 +----------+---------------------+----------------+-----------------+
2135 | Name | Notes | Level | Mux Category |
2136 +----------+---------------------+----------------+-----------------+
2137 | rtpred1 | Historic | Not-Applicable | NOT RECOMMENDED |
2138 | | attributes. | | |
2139 | | | | |
2140 | rtpred2 | Historic | Not-Applicable | NOT RECOMMENDED |
2141 | | attributes. | | |
2142 | | | | |
2143 +----------+---------------------+----------------+-----------------+
2145 Historical Attribute Analysis
2147 6. bwtype Attribute Analysis
2149 This section specifies handling of specific bandwidth attributes when
2150 used in multiplexing scenarios.
2152 6.1. RFC4566 - SDP: Session Description Protocol
2153 +------------+-----------------------------------+-------+----------+
2154 | Name | Notes | Level | Mux |
2155 | | | | Category |
2156 +------------+-----------------------------------+-------+----------+
2157 | bwtype:CT | Not Impacted | S | NORMAL |
2158 | | | | |
2159 | bwtype:AS | For the media level usage, the | B | SUM |
2160 | | aggregate of individual bandwidth | | |
2161 | | values is considered. | | |
2162 | | | | |
2163 +------------+-----------------------------------+-------+----------+
2165 RFC4566 bwtype Analysis
2167 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth
2169 [RFC3556] defines an extension to the Session Description Protocol
2170 (SDP) to specify two additional modifiers for the bandwidth
2171 attribute. These modifiers may be used to specify the bandwidth
2172 allowed for RTP Control Protocol (RTCP) packets in a Real-time
2173 Transport Protocol (RTP) session.
2175 +------------+-----------------------------------+-------+----------+
2176 | Name | Notes | Level | Mux |
2177 | | | | Category |
2178 +------------+-----------------------------------+-------+----------+
2179 | bwtype:RS | Session level usage represents | B | SUM |
2180 | | session aggregate and media level | | |
2181 | | usage indicates SUM of the | | |
2182 | | individual values while | | |
2183 | | multiplexing | | |
2184 | | | | |
2185 | bwtype:RR | Session level usage represents | B | SUM |
2186 | | session aggregate and media level | | |
2187 | | usage indicates SUM of the | | |
2188 | | individual values while | | |
2189 | | multiplexing | | |
2190 | | | | |
2191 +------------+-----------------------------------+-------+----------+
2193 RFC3556 bwtype Analysis
2195 6.3. RFC3890 - Bandwidth Modifier for SDP
2197 [RFC3890] defines a Session Description Protocol (SDP) Transport
2198 Independent Application Specific Maximum (TIAS) bandwidth modifier
2199 that does not include transport overhead; instead an additional
2200 packet rate attribute is defined. The transport independent bit-rate
2201 value together with the maximum packet rate can then be used to
2202 calculate the real bit-rate over the transport actually used.
2204 +------------------+-----------------------------+-------+----------+
2205 | Name | Notes | Level | Mux |
2206 | | | | Category |
2207 +------------------+-----------------------------+-------+----------+
2208 | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL |
2209 | | clearly defined | | |
2210 | | Offer/Answer usage. | | |
2211 | | | | |
2212 | bwtype:maxprate | The usage of TIAS and | B | SPECIAL |
2213 | | maxprate is not well | | |
2214 | | defined under multiplexing | | |
2215 | | | | |
2216 +------------------+-----------------------------+-------+----------+
2218 RFC3890 bwtype Analysis
2220 The intention of TIAS is that the media level bit-rate is multiplied
2221 with the known per-packet overhead for the selected transport and the
2222 maxprate value to determine the worst case bit-rate from the
2223 transport to more accurately capture the required usage. Summing
2224 TIAS values independently across m=lines and multiplying the computed
2225 sum with maxprate and the per-packet overhead would inflate the value
2226 significantly. Instead performing multiplication and adding the
2227 individual values is a more appropriate usage.
2229 7. rtcp-fb Attribute Analysis
2231 This section analyzes rtcp-fb SDP attributes.
2233 7.1. RFC4585 - RTP/AVPF
2235 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that
2236 enables receivers to provide, statistically, more immediate feedback
2237 to the senders and thus allows for short-term adaptation and
2238 efficient feedback-based repair mechanisms to be implemented.
2240 +----------+----------------------------+-------+-------------------+
2241 | Attr | Notes | Level | Mux Category |
2242 | Name | | | |
2243 +----------+----------------------------+-------+-------------------+
2244 | ack rpsi | The attribute value must | M | IDENTICAL-PER-PT |
2245 | | be same for a given codec | | |
2246 | | configuration | | |
2247 | | | | |
2248 | ack app | Feedback parameters MUST | M | SPECIAL |
2249 | | be handled in the app | | |
2250 | | specific way when | | |
2251 | | multiplexed | | |
2252 | | | | |
2253 | nack | The attribute value must | M | IDENTICAL-PER-PT |
2254 | | be same for a given codec | | |
2255 | | configuration | | |
2256 | | | | |
2257 | nack pli | The attribute value must | M | IDENTICAL-PER-PT |
2258 | | be same for a given codec | | |
2259 | | configuration | | |
2260 | | | | |
2261 | nack sli | The attribute value must | M | IDENTICAL-PER-PT |
2262 | | be same for a given codec | | |
2263 | | configuration | | |
2264 | | | | |
2265 | nack | The attribute value must | M | IDENTICAL-PER-PT |
2266 | rpsi | be same for a given codec | | |
2267 | | configuration | | |
2268 | | | | |
2269 | nack app | Feedback parameters MUST | M | SPECIAL |
2270 | | be handled in the app | | |
2271 | | specific way when | | |
2272 | | multiplexed | | |
2273 | | | | |
2274 | trr-int | The attribute value must | M | IDENTICAL-PER-PT |
2275 | | be same for a given codec | | |
2276 | | configuration | | |
2277 | | | | |
2278 +----------+----------------------------+-------+-------------------+
2280 RFC4585 Attribute Analysis
2282 7.2. RFC5104 - Codec Control Messages in AVPF
2284 [RFC5104] specifies a few extensions to the messages defined in the
2285 Audio-Visual Profile with Feedback (AVPF). They are helpful
2286 primarily in conversational multimedia scenarios where centralized
2287 multipoint functionalities are in use. However, some are also usable
2288 in smaller multicast environments and point-to-point calls.
2290 +-------+-------------------------------+-------+-------------------+
2291 | Attr | Notes | Level | Mux Category |
2292 | Name | | | |
2293 +-------+-------------------------------+-------+-------------------+
2294 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2295 | | same for a given codec | | |
2296 | | configuration | | |
2297 | | | | |
2298 +-------+-------------------------------+-------+-------------------+
2300 RFC5104 Attribute Analysis
2302 7.3. RFC6285 - Unicast-Based RAMS
2304 +-------+-------------------------------+-------+-------------------+
2305 | Name | Notes | Level | Mux Category |
2306 +-------+-------------------------------+-------+-------------------+
2307 | nack | The attribute value must be | M | IDENTICAL-PER-PT |
2308 | rai | same for a given codec | | |
2309 | | configuration | | |
2310 | | | | |
2311 +-------+-------------------------------+-------+-------------------+
2313 RFC6285 Attribute Analysis
2315 7.4. RFC6679 - ECN for RTP over UDP/IP
2317 [RFC6679] specifies how Explicit Congestion Notification (ECN) can be
2318 used with the Real-time Transport Protocol (RTP) running over UDP,
2319 using the RTP Control Protocol (RTCP) as a feedback mechanism. It
2320 defines a new RTCP Extended Report (XR) block for periodic ECN
2321 feedback, a new RTCP transport feedback message for timely reporting
2322 of congestion events, and a Session Traversal Utilities for NAT
2323 (STUN) extension used in the optional initialization method using
2324 Interactive Connectivity Establishment (ICE).
2326 +------------------+---------------------------+-------+------------+
2327 | Name | Notes | Level | Mux |
2328 | | | | Category |
2329 +------------------+---------------------------+-------+------------+
2330 | ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL |
2331 | | the RTP Session level | | |
2332 | | | | |
2333 | nack ecn | This attribute enables | M | IDENTICAL |
2334 | | ECN at the RTP session | | |
2335 | | level | | |
2336 | | | | |
2337 +------------------+---------------------------+-------+------------+
2339 RFC6679 Attribute Analysis
2341 7.5. RFC6642 - Third-Party Loss Report
2343 In a large RTP session using the RTP Control Protocol (RTCP) feedback
2344 mechanism defined in [RFC4585], a feedback target may experience
2345 transient overload if some event causes a large number of receivers
2346 to send feedback at once. This overload is usually avoided by
2347 ensuring that feedback reports are forwarded to all receivers,
2348 allowing them to avoid sending duplicate feedback reports. However,
2349 there are cases where it is not recommended to forward feedback
2350 reports, and this may allow feedback implosion. [RFC6642] memo
2351 discusses these cases and defines a new RTCP Third-Party Loss Report
2352 that can be used to inform receivers that the feedback target is
2353 aware of some loss event, allowing them to suppress feedback.
2354 Associated Session Description Protocol (SDP) signaling is also
2355 defined.
2357 +--------+------------------------------+-------+-------------------+
2358 | Name | Notes | Level | Mux Category |
2359 +--------+------------------------------+-------+-------------------+
2360 | nack | The attribute value must be | M | IDENTICAL-PER-PT |
2361 | tllei | same for a given codec | | |
2362 | | configuration | | |
2363 | | | | |
2364 | nack | The attribute value must be | M | IDENTICAL-PER-PT |
2365 | pslei | same for a given codec | | |
2366 | | configuration | | |
2367 | | | | |
2368 +--------+------------------------------+-------+-------------------+
2370 RFC6642 Attribute Analysis
2372 7.6. RFC5104 - Codec Control Messages in AVPF
2374 +--------+------------------------------+-------+-------------------+
2375 | Attr | Notes | Level | Mux Category |
2376 | Name | | | |
2377 +--------+------------------------------+-------+-------------------+
2378 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2379 | fir | same for a given codec | | |
2380 | | configuration | | |
2381 | | | | |
2382 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2383 | tmmbr | same for a given codec | | |
2384 | | configuration | | |
2385 | | | | |
2386 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2387 | tstr | same for a given codec | | |
2388 | | configuration | | |
2389 | | | | |
2390 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2391 | vbcm | same for a given codec | | |
2392 | | configuration | | |
2393 | | | | |
2394 +--------+------------------------------+-------+-------------------+
2396 RFC5104 Attribute Analysis
2398 8. group Attribute Analysis
2400 This section analyzes SDP "group" semantics.
2402 8.1. RFC5888 - SDP Grouping Framework
2404 [RFC5888] defines a framework to group "m" lines in the Session
2405 Description Protocol (SDP) for different purposes.
2407 +------------+---------------+-------+--------------+
2408 | Name | Notes | Level | Mux Category |
2409 +------------+---------------+-------+--------------+
2410 | group:LS | Not Impacted | S | NORMAL |
2411 | | | | |
2412 | group:FID | Not Impacted | S | NORMAL |
2413 | | | | |
2414 +------------+---------------+-------+--------------+
2416 RFC5888 Attribute Analysis
2418 8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows
2420 [RFC3524] defines an extension to the Session Description Protocol
2421 (SDP) grouping framework. It allows requesting a group of media
2422 streams to be mapped into a single resource reservation flow. The
2423 SDP syntax needed is defined, as well as a new "semantics" attribute
2424 called Single Reservation Flow (SRF).
2426 +------------+---------------+-------+--------------+
2427 | Name | Notes | Level | Mux Category |
2428 +------------+---------------+-------+--------------+
2429 | group:SRF | Not Impacted | S | NORMAL |
2430 | | | | |
2431 +------------+---------------+-------+--------------+
2433 RFC3524 Attribute Analysis
2435 8.3. RFC4091 - ANAT Semantics
2437 [RFC4091] defines the Alternative Network Address Types (ANAT)
2438 semantics for the Session Description Protocol (SDP) grouping
2439 framework. The ANAT semantics allow alternative types of network
2440 addresses to establish a particular media stream.
2442 +-------------+---------------------------+-------+-----------------+
2443 | Name | Notes | Level | Mux Category |
2444 +-------------+---------------------------+-------+-----------------+
2445 | group:ANAT | ANAT semantics is | S | NOT RECOMMENDED |
2446 | | obseleted | | |
2447 | | | | |
2448 +-------------+---------------------------+-------+-----------------+
2450 RFC4091 Attribute Analysis
2452 8.4. RFC5956 - FEC Grouping Semantics in SDP
2454 [RFC5956] defines the semantics for grouping the associated source
2455 and FEC-based (Forward Error Correction) repair flows in the Session
2456 Description Protocol (SDP). The semantics defined in the document
2457 are to be used with the SDP Grouping Framework (RFC 5888). These
2458 semantics allow the description of grouping relationships between the
2459 source and repair flows when one or more source and/or repair flows
2460 are associated in the same group, and they provide support for
2461 additive repair flows. SSRC-level (Synchronization Source) grouping
2462 semantics are also defined in this document for Real-time Transport
2463 Protocol (RTP) streams using SSRC multiplexing.
2465 +---------------+---------------+-------+--------------+
2466 | Name | Notes | Level | Mux Category |
2467 +---------------+---------------+-------+--------------+
2468 | group:FEC-FR | Not Impacted | S | NORMAL |
2469 | | | | |
2470 +---------------+---------------+-------+--------------+
2472 RFC5956 Attribute Analysis
2474 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP
2476 [RFC5583] defines semantics that allow for signaling the decoding
2477 dependency of different media descriptions with the same media type
2478 in the Session Description Protocol (SDP). This is required, for
2479 example, if media data is separated and transported in different
2480 network streams as a result of the use of a layered or multiple
2481 descriptive media coding process.
2483 +--------+------------------------------+-------+-------------------+
2484 | Name | Notes | Level | Mux Category |
2485 +--------+------------------------------+-------+-------------------+
2486 | depend | The attribute value must be | M | IDENTICAL-PER-PT |
2487 | lay | same for a given codec | | |
2488 | | configuration | | |
2489 | | | | |
2490 | depend | The attribute value must be | M | IDENTICAL-PER-PT |
2491 | mdc | same for a given codec | | |
2492 | | configuration | | |
2493 | | | | |
2494 +--------+------------------------------+-------+-------------------+
2496 RFC5583 Attribute Analysis
2498 8.6. RFC7104 - Duplication Grouping Semantics in the SDP
2500 [RFC7104] defines the semantics for grouping redundant streams in the
2501 Session Description Protocol (SDP). The semantics defined in this
2502 document are to be used with the SDP Grouping Framework. Grouping
2503 semantics at the Synchronization Source (SSRC) level are also defined
2504 in this document for RTP streams using SSRC multiplexing.
2506 +------------+---------------+-------+--------------+
2507 | Name | Notes | Level | Mux Category |
2508 +------------+---------------+-------+--------------+
2509 | group:DUP | Not Impacted | S | NORMAL |
2510 | | | | |
2511 +------------+---------------+-------+--------------+
2513 RFC7104 Attribute Analysis
2515 9. ssrc-group Attribute Analysis
2517 This section analyzes "ssrc-group" semantics.
2519 9.1. RFC5576 - Source-Specific SDP Attributes
2521 +-------------------+---------------+-------+--------------+
2522 | Name | Notes | Level | Mux Category |
2523 +-------------------+---------------+-------+--------------+
2524 | ssrc-group:FID | Not Impacted | SR | NORMAL |
2525 | | | | |
2526 | ssrc-group:FEC | Not Impacted | SR | NORMAL |
2527 | | | | |
2528 | ssrc-groupFEC-FR | Not Impacted | SR | NORMAL |
2529 | | | | |
2530 +-------------------+---------------+-------+--------------+
2532 RFC5576 Attribute Analysis
2534 9.2. RFC7104 - Duplication Grouping Semantics in the SDP
2536 +-----------------+---------------+-------+--------------+
2537 | Name | Notes | Level | Mux Category |
2538 +-----------------+---------------+-------+--------------+
2539 | ssrc-group:DUP | Not Impacted | SR | NORMAL |
2540 | | | | |
2541 +-----------------+---------------+-------+--------------+
2543 RFC7104 Attribute Analysis
2545 10. QoS Mechanism Token Analysis
2547 This section analyzes QoS tokes specified with SDP.
2549 10.1. RFC5432 - QoS Mechanism Selection in SDP
2550 +-------+---------------------------------------+-------+-----------+
2551 | Name | Notes | Level | Mux |
2552 | | | | Category |
2553 +-------+---------------------------------------+-------+-----------+
2554 | rsvp | Not Impacted, since QOS mechanisms | B | NORMAL |
2555 | | are applied per flow. | | |
2556 | | | | |
2557 | nsis | Not Impacted, since QOS mechanisms | B | NORMAL |
2558 | | are applied per flow. | | |
2559 | | | | |
2560 +-------+---------------------------------------+-------+-----------+
2562 RFC5432 Attribute Analysis
2564 11. k= Attribute Analysis
2566 11.1. RFC4566 SDP: Session Description Protocol
2568 +------+------------------------------------+-------+---------------+
2569 | Name | Notes | Level | Mux Category |
2570 +------+------------------------------------+-------+---------------+
2571 | k= | It is NOT recommended to use this | S | NOT |
2572 | | attribute | | RECOMMENDED |
2573 | | | | |
2574 +------+------------------------------------+-------+---------------+
2576 RFC4566 Attribute Analysis
2578 12. content Attribute Analysis
2580 12.1. RFC4796
2582 +------------------+---------------+-------+--------------+
2583 | Name | Notes | Level | Mux Category |
2584 +------------------+---------------+-------+--------------+
2585 | content:slides | Not Impacted | M | NORMAL |
2586 | | | | |
2587 | content:speaker | Not Impacted | M | NORMAL |
2588 | | | | |
2589 | content:main | Not Impacted | M | NORMAL |
2590 | | | | |
2591 | content:sl | Not Impacted | M | NORMAL |
2592 | | | | |
2593 | content:alt | Not Impacted | M | NORMAL |
2594 | | | | |
2595 +------------------+---------------+-------+--------------+
2597 RFC4796 Attribute Analysis
2599 13. Payload Formats
2601 13.1. RFC5109 - RTP Payload Format for Generic FEC
2603 [RFC5109] describes a payload format for generic Forward Error
2604 Correction (FEC) for media data encapsulated in RTP. It is based on
2605 the exclusive-or (parity) operation. The payload format allows end
2606 systems to apply protection using various protection lengths and
2607 levels, in addition to using various protection group sizes to adapt
2608 to different media and channel characteristics. It enables complete
2609 recovery of the protected packets or partial recovery of the critical
2610 parts of the payload depending on the packet loss situation.
2612 +---------------------+----------------------+-------+--------------+
2613 | Name | Notes | Level | Mux Category |
2614 +---------------------+----------------------+-------+--------------+
2615 | audio/ulpfec | Not recommended for | M | NOT |
2616 | | multiplexing due to | | RECOMMENDED |
2617 | | reuse of SSRCs | | |
2618 | | | | |
2619 | video/ulpfec | Not recommended for | M | NOT |
2620 | | multiplexing due to | | RECOMMENDED |
2621 | | reuse of SSRCs | | |
2622 | | | | |
2623 | text/ulpfec | Not recommended for | M | NOT |
2624 | | multiplexing due to | | RECOMMENDED |
2625 | | reuse of SSRCs | | |
2626 | | | | |
2627 | application/ulpfec | Not recommended for | M | NOT |
2628 | | multiplexing due to | | RECOMMENDED |
2629 | | reuse of SSRCs | | |
2630 | | | | |
2631 +---------------------+----------------------+-------+--------------+
2633 RFC5109 Payload Format Analysis
2635 Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make
2636 it possible to use ULP with multiplexing and ULP is allowed when used
2637 with that.
2639 14. Multiplexing Considerations for Encapsulating Attributes
2641 This sections deals with recommendations for defining the
2642 multiplexing characteristics of the SDP attributes that encapsulate
2643 other SDP attributes/parameters. Such attributes as of today, for
2644 example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of
2645 a generic framework for indicating and negotiating transport, media
2646 and media format related capabilities in the SDP.
2648 The behavior of such attributes under multiplexing is in turn defined
2649 by the multiplexing behavior of the attributes they encapsulate which
2650 are made known once the Offer/Answer negotiation process is
2651 completed.
2653 14.1. RFC3407 - cpar Attribute Analysis
2655 [RFC3407] capability parameter attribute (a=cpar) encapsulates b=
2656 (bandwidth) or an a= attribute. For bandwidth attribute
2657 encapsulation, the category SUM is inherited. For the case of a=
2658 attribute, the category corresponding to the SDP attribute being
2659 encapsulated is inherited.
2661 v=0
2662 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
2663 s=
2664 c=IN IP4 host.atlanta.example.com
2665 t=0 0
2666 m=video 3456 RTP/AVP 100
2667 a=rtpmap:100 VP8/90000
2668 a=sqn: 0
2669 a=cdsc: 1 video RTP/AVP 100
2670 a=cpar: a=rtcp-mux
2671 m=video 3456 RTP/AVP 101
2672 a=rtpmap:101 VP8/90000
2673 a=fmtp:100 max-fr=15;max-fs=1200
2674 a=cdsc: 2 video RTP/AVP 101
2675 a=cpar: a=rtcp-mux
2677 In the above example ,the category IDENTICAL is inherited for the
2678 cpar encapsulated rtcp-mux attribute.
2680 14.2. RFC5939 Analysis
2682 [RFC5939] defines a general SDP capability negotiation framework. It
2683 also specifies how to provide transport protocols and SDP attributes
2684 as capabilities and negotiate them using the framework.
2686 For this purpose, [RFC5939] defines the following
2688 o A set of capabilities for the session and its associated media
2689 stream components, supported by each side. The attribute
2690 ("a=acap") defines how to list an attribute name and its
2691 associated value (if any) as a capability. The attribute
2692 ("a=tcap") defines how to list transport protocols (e.g., "RTP/
2693 AVP") as capabilities.
2695 o A set of potential configurations ("a=pcfg") provided by the
2696 offerer to indicate whcich combination of those capabilities can
2697 be used for the session and its associated media stream
2698 components. Potential configurations are not ready for use until
2699 fully negotiated. They provide an alternative that may be used,
2700 subject to SDP capability negotiation procedures. In particular
2701 the answerer may choose one of the potential configurations for
2702 use as part of the current Offer/Answer exchange.
2704 o An actual configuration ("a=acfg") for the session and its
2705 associated media stream components. The actual configuration
2706 identifies the potential configuration that was negotiated for
2707 use. Use of an actual configuration does not require any further
2708 negotiation.
2710 o A negotiation process that takes the current actual and the set of
2711 potential configurations (combinations of capabilities) as input
2712 and provides the negotiated actual configurations as output. In
2713 [RFC5939] the negotiation process is done independently for each
2714 media description.
2716 14.2.1. Recommendation - Procedures for Potential Configuration Pairing
2718 This section provides recommendations for entities generating and
2719 processing SDP under the generic capability negotiation framework as
2720 defined in [RFC5939] under the context of media stream multiplexing.
2722 These recommendations are provided for the purposes of enabling the
2723 Offerer to make sure that the generated potential configurations
2724 between the multiplexed streams can (easily) be negotiated to be
2725 consistent between those streams. In particular, the procedures aim
2726 to simplify Answerer's procedure to choose potential configurations
2727 that are consistent across all the bundled media descriptions.
2729 A potential configuration selects a set of attributes and parameters
2730 that become part of the media description when negotiated. When
2731 multiplexing media descriptions with potential configurations
2732 specified, there may be a need for coordinating this selection
2733 between multiplexed media descriptions ensuring right multiplexing
2734 behavior.
2736 Although it is possible to analyze the various potential
2737 configurations in bundled media descriptions to find combinations
2738 that satisfy such constraints, it can quickly become complicated to
2739 do so.
2741 The procedures defined in [RFC5939] state that each potential
2742 configuration in the SDP has a unique configuration number, however
2743 the scope of uniqueness is limited to each media description. To
2744 make it simple for the answerer to chose valid combinations of
2745 potential configurations across media descriptions in a given bundle
2746 group, we provide a simple rule for constructing potential
2747 configurations:-
2749 o Let m-bundle be the set of media descriptions that form a given
2750 bundle .
2752 o Let m-bundle-pcfg be the set of media descriptions in m-bundle
2753 that include one or more potential configurations.
2755 o Each media description in m-bundle-pcfg MUST have at least one
2756 potential configuration with the same configuration number (e.g.
2757 "1").
2759 o For each potential configuration with configuration number x in m-
2760 bundle-pcfg, the offerer MUST ensure that if the answerer chooses
2761 configuration number x in each of the media descriptions in m-
2762 bundle-pcfg, then the resulting SDP will have all multiplexing
2763 constraints satisfied for those media descriptions.
2765 o Since it is nearly impossible to define a generic mechanism for
2766 various capability extensions , this document does't provide
2767 procedures for dealing with the capability extension attributes.
2768 However, Section 14.3 provide analysis of media capability
2769 extension attributes as defined in [RFC6871].
2771 The above allows the answerer to easily find multiplexing compatible
2772 combinations of potential configurations:- The answerer simply choses
2773 a potential configuration (number) that is present in all of the
2774 media descriptions with potential configurations in the bundle.
2776 Note that it is still possible for the offerer to provide additional
2777 potential configurations with independent configuration numbers. The
2778 answerer will have to perform more complicated analysis to determine
2779 valid multiplexed combinations of those.
2781 14.2.1.1. Example: Transport Capability Multiplexing
2782 v=0
2783 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
2784 s=
2785 c=IN IP4 host.atlanta.example.com
2786 t=0 0
2787 a=tcap:1 RTP/SAVPF
2788 a=tcap:2 RTP/SAVP
2789 a=group:BUNDLE audio video
2790 m= audio
2791 a=mid:audio
2792 a=pcfg:1 t=1
2793 a=pcfg:2
2794 m= video
2795 a=mid:video
2796 a=pcfg:1 t=1
2797 a=pcfg:2 t=2
2799 In the example above, the potential configurations that offer
2800 transport protocol capability of RTP/SAVPF has the same configuration
2801 number "1" in both the audio and video media descriptions.
2803 14.2.1.2. Example: Attribute Capability Multiplexing
2805 v=0
2806 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
2807 s=
2808 c=IN IP4 host.atlanta.example.com
2809 t=0 0
2810 a=acap:1 a=rtcp-mux
2811 a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80
2812 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
2813 a=group:BUNDLE audio video
2814 m= audio 49172 RTP/AVP 99
2815 a=mid:audio
2816 a=pcfg:1 a=1
2817 a=pcfg:2
2818 m= video 560024 RTP/AVP 100
2819 a=mid:video
2820 a=pcfg:1 a=1
2821 a=pcfg:2 a=2
2823 In the example above, the potential configuration number "1" is
2824 repeated while referring to attribute capability a=rtcp-mux, since
2825 the behavior is IDENTICAL for the attribute a=rtcp-mux under
2826 multiplexing.
2828 14.3. RFC6871 Analysis
2830 [RFC6871] extends capability negotiation framework described in
2831 [RFC5939] by defining media capabilities that can be used to indicate
2832 and negotiate media types and their associated format parameters. It
2833 also allows indication of latent configurations and session
2834 capabilities.
2836 14.3.1. Recommendation: Dealing with Payload Type Numbers
2838 [RFC6871] defines a new payload type ("pt") parameter to be used with
2839 the potential, actual and latent configuration parameters. The
2840 parameter associates RTP payload type numbers with the referenced
2841 RTP-based media format capabilities ("a=rmcap") defined in [RFC6871]
2842 and is appropriate only when the transport protocol uses RTP. This
2843 means that the same payload type number can be assigned as part of
2844 potential or actual configurations in different media descriptions in
2845 a bundle. There are rules for the usage of identical Payload Type
2846 values across multiplexed m=lines as described in
2847 [I-D.ietf-mmusic-sdp-bundle-negotiation], which MUST be followed here
2848 as well. As described in Section 14.2.1, the use of identical
2849 configuration numbers for compatible configurations in different
2850 media descriptions that are part of the bundle provides a way to
2851 ensure that the answerer can easily pick compatible configurations
2852 here as well.
2854 14.3.1.1. Example: Attribute Capability Under Shared Payload Type
2856 The attributes (a=rmcap, a=mfcap) follow the above recommendations
2857 under mutliplexing.
2859 v=0
2860 o=- 25678 753849 IN IP4 192.0.2.1
2861 s=
2862 c=IN IP4 192.0.2.1
2863 t=0 0
2864 a=creq:med-v0
2865 m=audio 54322 RTP/AVP 96
2866 a=rtpmap:96 AMR-WB/16000/1
2867 a=fmtp:96 mode-change-capability=1; max-red=220;
2868 mode-set=0,2,4,7
2869 a=rmcap:1,3 audio AMR-WB/16000/1
2870 a=rmcap:2 audio AMR/8000/1
2871 a=mfcap:1,2 mode-change-capability=1
2872 a=mfcap:3 mode-change-capability=2
2873 a=pcfg:1 m=1 pt=1:96
2874 a=pcfg:2 m=2 pt=2:97
2875 a=pcfg:3 m=3 pt=3:98
2876 m=audio 54322 RTP/AVP 96
2877 a=rtpmap:96 AMR-WB/16000/1
2878 a=fmtp:96 mode-change-capability=1; max-red=220;
2879 mode-set=0,2,4,7
2880 a=rmcap:4 audio AMR/8000/1
2881 a=rmcap:5 audio OPUS/48000/2
2882 a=mfcap:5 minptime=40
2883 a=mfcap:4 mode-change-capability=1
2884 a=pcfg:1 m=4 pt=4:97
2885 a=pcfg:4 m=5 pt=5:101
2887 In the example above, the potential configuration number "1" is
2888 repeated when referring to media and media format capability used for
2889 the Payload Type 97. This implies that both the media capability 2
2890 and 4 along with their media format capabilities MUST refer to the
2891 same codec configuration , as per the definition of IDENTICAL-PER-PT.
2893 14.3.2. Recommendation: Dealing with Latent Configurations
2895 [RFC6871] adds the notion of a latent configurations, which provides
2896 configuration information that may be used to guide a subsequent
2897 offer/exchange, e.g. by adding another media stream or use
2898 alternative codec combinations not currently offered. Latent
2899 configurations have configuration numbers which cannot overlap with
2900 the potential configuration numbers [RFC6871]. Supported
2901 combinations of potential and latent configurations are indicated by
2902 use of the "a=sescap" attribute, however use of this attribute is not
2903 recommended with bundled media, since it requires the use of unique
2904 configuration numbers across the SDP. Taken together, this means
2905 there is no well-defined way to indicate supported combinations of
2906 latent configurations, or combinations of latent and potential
2907 configurations with bundled media. It is still allowed to use the
2908 latent configuration attribute, however the limitations above will
2909 apply. To determine valid combinations, actual negotiation will have
2910 to be attempted subsequently instead.
2912 15. IANA Considerations
2914 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
2915 document.]
2917 The IANA is requested to add a new column named "Mux Category" to
2918 several of the subregistries in the "Session Description Protocol
2919 (SDP) Parameters" registry. Section 15.1 defines a new subregistry
2920 for identifying the initial registrations for various multiplexing
2921 categories applicable, as proposed in this document.
2923 The tables in Section 15.2 identify name of an entry in the existing
2924 subregistry and specify the value to put in the new "Mux Category"
2925 column of the associated IANA registry. Any entries in the existing
2926 tables that do not have a value for the "Mux Category" specified in
2927 this RFC will get a value of "TBD". Future specifications can change
2928 the "TBD" entries to the correct value.
2930 15.1. New 'Multiplexing Categories' subregistry
2932 A new sub-registry needs to be defined called the "Multiplexing
2933 Categories", with the following registrations created initially:
2934 "NORMAL", "NOT RECOMMENDED", "IDENTICAL", "TRANSPORT", "SUM",
2935 "INHERIT", "IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this
2936 document.
2938 Initial value registration for "Multiplexing Categories".
2940 +-------------------------+-----------+
2941 | Multiplexing Categories | Reference |
2942 +-------------------------+-----------+
2943 | NORMAL | RFCXXXX |
2944 | NOT RECOMMENDED | RFCXXXX |
2945 | IDENTICAL | RFCXXXX |
2946 | TRANSPORT | RFCXXXX |
2947 | SUM | RFCXXXX |
2948 | INHERIT | RFCXXXX |
2949 | IDENTICAL-PER-PT | RFCXXXX |
2950 | SPECIAL | RFCXXXX |
2951 | TBD | RFCXXXX |
2952 +-------------------------+-----------+
2953 Further entries may be registered on a first-come first-serve basis.
2954 Each registration needs to indicate the multiplexing category value
2955 to be added to the "Multiplexing Categories" subregistry as defined
2956 in this section.
2958 Such a registration must also indicate the applicability of the newly
2959 defined multiplexing category value to various subregistries defined
2960 at "Session Description Protocol (SDP) Parameters".
2962 The general registration procedures of [RFC4566] apply.
2964 15.2. 'Mux Category' column for subregistries
2966 Each sub-section identifies a subregistry in the "Session Description
2967 Protocol (SDP) Parameters" registry. The tables list the column that
2968 identifies the SDP attribute name/Token/Value from the corresponding
2969 subregistries and the values to be used for the new "Mux Category"
2970 column to be added.
2972 15.2.1. Table: SDP bwtype
2974 The following values are to be added to the 'SDP bwtype' subregistry
2975 in the "Session Description Protocol (SDP) Parameters" registry. The
2976 references should be updated to point at this RFC as well as the
2977 previous references.
2979 +----------+--------------+
2980 | SDP Name | Mux Category |
2981 +----------+--------------+
2982 | CT | NORMAL |
2983 | AS | SUM |
2984 | RS | SUM |
2985 | RR | SUM |
2986 | TIAS | SPECIAL |
2987 +----------+--------------+
2989 15.2.2. Table: att-field (session level)
2991 The following values are to be added to the "att-field (session
2992 level)" subregistry in the "Session Description Protocol (SDP)
2993 Parameters" registry. The references should be updated to point at
2994 this RFC as well as the previous references.
2996 +---------------------+------------------+
2997 | SDP Name | Mux Category |
2998 +---------------------+------------------+
2999 | cat | NORMAL |
3000 | keywds | NORMAL |
3001 | type | NORMAL |
3002 | type:broadcast | NORMAL |
3003 | type:H332 | NORMAL |
3004 | type:meeting | NORMAL |
3005 | type:moderated | NORMAL |
3006 | type:test | NORMAL |
3007 | charset | NORMAL |
3008 | charset:iso8895-1 | NORMAL |
3009 | tool | NORMAL |
3010 | ipbcp | NORMAL |
3011 | group | NORMAL |
3012 | ice-lite | NORMAL |
3013 | ice-options | NORMAL |
3014 | bcastversion | NORMAL |
3015 | 3GPP-Integrity-Key | NOT RECOMMENDED |
3016 | 3GPP-SDP-Auth | NOT RECOMMENDED |
3017 | alt-group | NOT RECOMMENDED |
3018 | PSCid | NORMAL |
3019 | bc_service | NORMAL |
3020 | bc_program | NORMAL |
3021 | bc_service_package | NORMAL |
3022 | sescap | NOT RECOMMENDED |
3023 | rtsp-ice-d-m | NOT RECOMMENDED |
3024 +---------------------+------------------+
3026 15.2.3. Table: att-field (both session and media level)
3028 The following values are to be added to the "att-field (both session
3029 and media level)" subregistry in the "Session Description Protocol
3030 (SDP) Parameters" registry. The references should be updated to
3031 point at this RFC as well as the previous references.
3033 +-------------------------+-------------------+
3034 | SDP Name | Mux Category |
3035 +-------------------------+-------------------+
3036 | recvonly | NORMAL |
3037 | sendrecv | NORMAL |
3038 | sendonly | NORMAL |
3039 | sdplang | NORMAL |
3040 | lang | NORMAL |
3041 | h248item | SPECIAL |
3042 | sqn | NORMAL |
3043 | cdsc | NORMAL |
3044 | cpar | INHERIT |
3045 | cparmin | SPECIAL |
3046 | cparmax | SPECIAL |
3047 | rtcp-xr | NORMAL |
3048 | maxprate | SPECIAL |
3049 | setup | IDENTICAL |
3050 | connection | IDENTICAL |
3051 | key-mgmt | IDENTICAL |
3052 | source-filter | IDENTICAL |
3053 | inactive | NORMAL |
3054 | fingerprint | TRANSPORT |
3055 | flute-tsi | TBD |
3056 | flute-ch | TBD |
3057 | FEC-declaration | TBD |
3058 | FEC-OTI-extension | TBD |
3059 | content-desc | TBD |
3060 | ice-pwd | TRANSPORT |
3061 | ice-ufrag | TRANSPORT |
3062 | stkmstream | NORMAL |
3063 | extmap | SPECIAL |
3064 | qos-mech-send | NORMAL |
3065 | qos-mech-recv | NORMAL |
3066 | csup | NORMAL |
3067 | creq | NORMAL |
3068 | acap | INHERIT |
3069 | tcap | INHERIT |
3070 | 3GPP-QoE-Metrics | NOT RECOMMENDED |
3071 | 3GPP-Asset-Information | NOT RECOMMENDED |
3072 | mbms-mode | NOT RECOMMENDED |
3073 | mbms-repair | NOT RECOMMENDED |
3074 | ike-setup | IDENTICAL |
3075 | psk-fingerprint | IDENTICAL |
3076 | multicast-rtcp | IDENTICAL |
3077 | rmcap | IDENTICAL-PER-PT |
3078 | omcap | NORMAL |
3079 | mfcap | IDENTICAL-PER-PT |
3080 | mscap | INHERIT |
3081 | 3gpp.iut.replication | TBD |
3082 | bcap | INHERIT |
3083 | ccap | IDENTICAL |
3084 | icap | NORMAL |
3085 | 3gpp_sync_info | NORMAL |
3086 | 3gpp_MaxRecvSDUSize | NORMAL |
3087 | etag | NOT RECOMMENDED |
3088 | duplication-delay | NORMAL |
3089 | range | NOT RECOMMENDED |
3090 | control | NOT RECOMMENDED |
3091 | mtag | NOT RECOMMENDED |
3092 | ts-refclk | NORMAL |
3093 | mediaclk | NORMAL |
3094 | calgextmap | NORMAL |
3095 +-------------------------+-------------------+
3097 15.2.4. Table: att-field (media level only)
3099 The following values are to be added to the "att-field (media level
3100 only)" registry in the "Session Description Protocol (SDP)
3101 Parameters" registry. The references should be updated to point at
3102 this RFC as well as the previous references.
3104 +---------------------------+-------------------+
3105 | SDP Name | Mux Category |
3106 +---------------------------+-------------------+
3107 | ptime | IDENTICAL-PER-PT |
3108 | orient | NORMAL |
3109 | orient:portrait | NORMAL |
3110 | orient:landscape | NORMAL |
3111 | orient:seascape | NORMAL |
3112 | framerate | IDENTICAL-PER-PT |
3113 | quality | NORMAL |
3114 | rtpmap | IDENTICAL-PER-PT |
3115 | fmtp | IDENTICAL-PER-PT |
3116 | rtpred1 | NOT RECOMMENDED |
3117 | rtpred2 | NOT RECOMMENDED |
3118 | T38FaxVersion | NORMAL |
3119 | T38MaxBitRate | NORMAL |
3120 | T38FaxFillBitRemoval | NORMAL |
3121 | T38FaxTranscodingMMR | NORMAL |
3122 | T38FaxTranscodingJBIG | NORMAL |
3123 | T38FaxRateManagement | NORMAL |
3124 | T38FaxMaxBuffer | NORMAL |
3125 | T38FaxMaxDatagram | NORMAL |
3126 | T38FaxUdpEC | NORMAL |
3127 | maxptime | IDENTICAL-PER-PT |
3128 | des | NOT RECOMMENDED |
3129 | curr | NOT RECOMMENDED |
3130 | conf | NOT RECOMMENDED |
3131 | mid | NORMAL |
3132 | rtcp | IDENTICAL |
3133 | rtcp-fb | IDENTICAL-PER-PT |
3134 | label | NORMAL |
3135 | T38VendorInfo | NORMAL |
3136 | crypto | TRANSPORT |
3137 | eecid | NORMAL |
3138 | aalType | NORMAL |
3139 | capability | NORMAL |
3140 | qosClass | NORMAL |
3141 | bcob | NORMAL |
3142 | stc | NORMAL |
3143 | upcc | NORMAL |
3144 | atmQOSparms | NORMAL |
3145 | atmTrfcDesc | NORMAL |
3146 | abrParms | NORMAL |
3147 | abrSetup | NORMAL |
3148 | bearerType | NORMAL |
3149 | lij | NORMAL |
3150 | anycast | NORMAL |
3151 | cache | NORMAL |
3152 | bearerSigIE | NORMAL |
3153 | aalApp | NORMAL |
3154 | cbrRate | NORMAL |
3155 | sbc | NORMAL |
3156 | clkrec | NORMAL |
3157 | fec | NORMAL |
3158 | prtfl | NORMAL |
3159 | structure | NORMAL |
3160 | cpsSDUsize | NORMAL |
3161 | all2CPS | NORMAL |
3162 | all2CPSSDUrate | NORMAL |
3163 | aal2sscs3661unassured | NORMAL |
3164 | aal2sscs3661assured | NORMAL |
3165 | aal2sscs3662 | NORMAL |
3166 | aal5sscop | NORMAL |
3167 | atmmap | NORMAL |
3168 | silenceSupp | NORMAL |
3169 | ecan | NORMAL |
3170 | gc | NORMAL |
3171 | profileDesc | NORMAL |
3172 | vsel | NORMAL |
3173 | dsel | NORMAL |
3174 | fsel | NORMAL |
3175 | onewaySel | NORMAL |
3176 | codecConfig | NORMAL |
3177 | isup_usi | NORMAL |
3178 | uiLayer1_Prot | NORMAL |
3179 | chain | NORMAL |
3180 | floorctrl | IDENTICAL |
3181 | confid | NORMAL |
3182 | userid | NORMAL |
3183 | floorid | NORMAL |
3184 | FEC | NORMAL |
3185 | accept-types | NORMAL |
3186 | accept-wrapped-types | NORMAL |
3187 | max-size | NORMAL |
3188 | path | NORMAL |
3189 | dccp-service-code | NOT RECOMMENDED |
3190 | rtcp-mux | IDENTICAL |
3191 | candidate | TRANSPORT |
3192 | ice-mismatch | NORMAL |
3193 | remote-candidates | TRANSPORT |
3194 | SRTPAuthentication | NORMAL |
3195 | SRTPROCTxRate | NORMAL |
3196 | rtcp-rsize | IDENTICAL |
3197 | file-selector | NORMAL |
3198 | file-transfer-id | NORMAL |
3199 | file-disposition | NORMAL |
3200 | file-date | NORMAL |
3201 | file-icon | NORMAL |
3202 | file-range | NORMAL |
3203 | depend | IDENTICAL-PER-PT |
3204 | ssrc | NORMAL |
3205 | ssrc-group | NORMAL |
3206 | rtcp-unicast | IDENTICAL |
3207 | pcfg | SPECIAL |
3208 | acfg | SPECIAL |
3209 | zrtp-hash | NOT RECOMMENDED |
3210 | X-predecbufsize | NOT RECOMMENDED |
3211 | X-initpredecbufperiod | NOT RECOMMENDED |
3212 | X-initpostdecbufperiod | NOT RECOMMENDED |
3213 | X-decbyterate | NOT RECOMMENDED |
3214 | 3gpp-videopostdecbufsize | NOT RECOMMENDED |
3215 | framesize | NOT RECOMMENDED |
3216 | 3GPP-SRTP-Config | NOT RECOMMENDED |
3217 | alt | NOT RECOMMENDED |
3218 | alt-default-id | NOT RECOMMENDED |
3219 | 3GPP-Adaption-Support | NOT RECOMMENDED |
3220 | mbms-flowid | NOT RECOMMENDED |
3221 | fec-source-flow | SPECIAL |
3222 | fec-repair-flow | SPECIAL |
3223 | repair-window | SPECIAL |
3224 | rams-updates | NOT RECOMMENDED |
3225 | imageattr | IDENTICAL-PER-PT |
3226 | cfw-id | NORMAL |
3227 | portmapping-req | NOT RECOMMENDED |
3228 | g.3gpp.cat | NORMAL |
3229 | g.3gpp.crs | NORMAL |
3230 | ecn-capable-rtp | IDENTICAL |
3231 | visited-realm | TRANSPORT |
3232 | secondary-realm | TRANSPORT |
3233 | omr-s-cksum | NORMAL |
3234 | omr-m-cksum | NORMAL |
3235 | omr-codecs | NORMAL |
3236 | omr-m-att | NORMAL |
3237 | omr-s-att | NORMAL |
3238 | omr-m-bw | NORMAL |
3239 | omr-s-bw | NORMAL |
3240 | msrp-cema | NORMAL |
3241 | dccp-port | NOT RECOMMENDED |
3242 | resource | NORMAL |
3243 | channel | NORMAL |
3244 | cmid | NORMAL |
3245 | content | NORMAL |
3246 | lcfg | SPECIAL |
3247 | loopback | NORMAL |
3248 | loopback-source | NORMAL |
3249 | loopback-mirror | NORMAL |
3250 | chatroom | TBD |
3251 | altc | TRANSPORT |
3252 | T38FaxMaxIFP | NORMAL |
3253 | T38FaxUdpECDepth | NORMAL |
3254 | T38FaxUdpFECMaxSpan | NORMAL |
3255 | T38ModemType | NORMAL |
3256 | cs-correlation | NORMAL |
3257 | rtcp-idms | NORMAL |
3258 +---------------------------+-------------------+
3260 15.2.5. Table: att-field (source level)
3262 The following values are to be added to the "att-field (source
3263 level)" registry in the "Session Description Protocol (SDP)
3264 Parameters" registry. The references should be updated to point at
3265 this RFC as well as the previous references.
3267 +----------------+-------------------+
3268 | SDP Name | Mux Category |
3269 +----------------+-------------------+
3270 | cname | NORMAL |
3271 | previous-ssrc | NORMAL |
3272 | fmtp | IDENTICAL-PER-PT |
3273 | ts-refclk | NORMAL |
3274 | mediaclk | NORMAL |
3275 +----------------+-------------------+
3277 15.2.6. Table: content SDP Parameters
3279 The following values are to be added to the "content SDP Parameters"
3280 subregistry in the "Session Description Protocol (SDP) Parameters"
3281 registry. The references should be updated to point at this RFC as
3282 well as the previous references.
3284 +----------+--------------+
3285 | SDP Name | Mux Category |
3286 +----------+--------------+
3287 | slides | NORMAL |
3288 | speaker | NORMAL |
3289 | sl | NORMAL |
3290 | main | NORMAL |
3291 | alt | NORMAL |
3292 +----------+--------------+
3294 15.2.7. Table: Semantics for the 'group' SDP Attribute
3296 The following values are to be added to the "Semantics for the
3297 "group" SDP Attribute" subregistry in the "Session Description
3298 Protocol (SDP) Parameters" registry. The references should be
3299 updated to point at this RFC as well as the previous references.
3301 +---------+------------------+
3302 | Token | Mux Category |
3303 +---------+------------------+
3304 | LS | NORMAL |
3305 | FID | NORMAL |
3306 | SRF | NORMAL |
3307 | ANAT | NOT RECOMMENDED |
3308 | FEC | NORMAL |
3309 | FEC-FR | NORMAL |
3310 | CS | NORMAL |
3311 | DDP | NORMAL |
3312 | DUP | NORMAL |
3313 +---------+------------------+
3315 15.2.8. Table: 'rtcp-fb' Attribute Values
3317 The following values are to be added to the " 'rtcp-fb' Attribute
3318 Values" subregistry in the "Session Description Protocol (SDP)
3319 Parameters" registry. The references should be updated to point at
3320 this RFC as well as the previous references.
3322 +------------+-------------------+
3323 | Value Name | Mux Category |
3324 +------------+-------------------+
3325 | ack | IDENTICAL-PER-PT |
3326 | app | SPECIAL |
3327 | ccm | IDENTICAL-PER-PT |
3328 | nack | IDENTICAL-PER-PT |
3329 | trr-int | IDENTICAL-PER-PT |
3330 +------------+-------------------+
3332 15.2.9. Table: 'ack' and 'nack' Attribute Values
3334 The following values are to be added to the " 'ack' and 'nack'
3335 Attribute Values" subregistry in the "Session Description Protocol
3336 (SDP) Parameters" registry. The references should be updated to
3337 point at this RFC as well as the previous references.
3339 +------------+-------------------+
3340 | Value Name | Mux Category |
3341 +------------+-------------------+
3342 | sli | IDENTICAL-PER-PT |
3343 | pli | IDENTICAL-PER-PT |
3344 | rpsi | IDENTICAL-PER-PT |
3345 | app | SPECIAL |
3346 | rai | IDENTICAL-PER-PT |
3347 | tllei | IDENTICAL-PER-PT |
3348 | pslei | IDENTICAL-PER-PT |
3349 | ecn | IDENTICAL |
3350 +------------+-------------------+
3352 15.2.10. Table: 'depend' SDP Attribute Values
3354 The following values are to be added to the " 'depend' SDP Attribute
3355 Values" subregistry in the "Session Description Protocol (SDP)
3356 Parameters" registry. The references should be updated to point at
3357 this RFC as well as the previous references.
3359 +-------+-------------------+
3360 | Token | Mux Category |
3361 +-------+-------------------+
3362 | lay | IDENTICAL-PER-PT |
3363 | mdc | IDENTICAL-PER-PT |
3364 +-------+-------------------+
3366 15.2.11. Table: 'cs-correlation' Attribute Values
3368 The following values are to be added to the " "cs-correlation"
3369 Attribute Values" subregistry in the "Session Description Protocol
3370 (SDP) Parameters" registry. The references should be updated to
3371 point at this RFC as well as the previous references.
3373 +-----------+--------------+
3374 | Value | Mux Category |
3375 +-----------+--------------+
3376 | callerid | NORMAL |
3377 | uuie | NORMAL |
3378 | dtmf | NORMAL |
3379 | external | NORMAL |
3380 +-----------+--------------+
3382 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute
3384 The following values are to be added to the Semantics for the
3385 "Semantics for the "ssrc-group" SDP Attribute" subregistry in the
3386 "Session Description Protocol (SDP) Parameters" registry. The
3387 references should be updated to point at this RFC as well as the
3388 previous references.
3390 +---------+--------------+
3391 | Token | Mux Category |
3392 +---------+--------------+
3393 | FID | NORMAL |
3394 | FEC | NORMAL |
3395 | FEC-FR | NORMAL |
3396 | DUP | NORMAL |
3397 +---------+--------------+
3399 15.2.13. Table: SDP/RTSP key management protocol identifiers
3401 The following values are to be added to the "SDP/RTSP key management
3402 protocol identifiers" subregistry in the "Session Description
3403 Protocol (SDP) Parameters" registry. The references should be
3404 updated to point at this RFC as well as the previous references.
3406 +------------+--------------+
3407 | Value Name | Mux Category |
3408 +------------+--------------+
3409 | mikey | IDENTICAL |
3410 +------------+--------------+
3412 15.2.14. Table: Codec Control Messages
3414 The following values are to be added to the "Codec Control Messages"
3415 subregistry in the "Session Description Protocol (SDP) Parameters"
3416 registry. The references should be updated to point at this RFC as
3417 well as the previous references.
3419 +------------+-------------------+
3420 | Value Name | Mux Category |
3421 +------------+-------------------+
3422 | fir | IDENTICAL-PER-PT |
3423 | tmmbr | IDENTICAL-PER-PT |
3424 | tstr | IDENTICAL-PER-PT |
3425 | vbcm | IDENTICAL-PER-PT |
3426 +------------+-------------------+
3428 15.2.15. Table: QoS Mechanism Tokens
3430 The following values are to be added to the "QoS Mechanism Tokens"
3431 subregistry in the "Session Description Protocol (SDP) Parameters"
3432 registry. The references should be updated to point at this RFC as
3433 well as the previous references.
3435 +---------------+--------------+
3436 | QoS Mechanism | Mux Category |
3437 +---------------+--------------+
3438 | rsvp | NORMAL |
3439 | nsis | NORMAL |
3440 +---------------+--------------+
3442 15.2.16. Table: SDP Capability Negotiation Option Tags
3444 The following values are to be added to the "SDP Capability
3445 Negotiation Option Tags" subregistry in the "Session Description
3446 Protocol (SDP) Parameters" registry. The references should be
3447 updated to point at this RFC as well as the previous references.
3449 +---------------+--------------+
3450 | QoS Mechanism | Mux Category |
3451 +---------------+--------------+
3452 | cap-v0 | NORMAL |
3453 | med-v0 | NORMAL |
3454 | bcap-v0 | NORMAL |
3455 | ccap-v0 | NORMAL |
3456 | icap-v0 | NORMAL |
3457 +---------------+--------------+
3459 15.2.17. Table: Timestamp Reference Clock Source Parameters
3461 The following values are to be added to the "Timestamp Reference
3462 Clock Source Parameters" subregistry in the "Session Description
3463 Protocol (SDP) Parameters" registry. The references should be
3464 updated to point at this RFC as well as the previous references.
3466 +----------+--------------+
3467 | Name | Mux Category |
3468 +----------+--------------+
3469 | ntp | NORMAL |
3470 | ptp | NORMAL |
3471 | gps | NORMAL |
3472 | gal | NORMAL |
3473 | glonass | NORMAL |
3474 | local | NORMAL |
3475 | private | NORMAL |
3476 +----------+--------------+
3478 15.2.18. Table: Media Clock Source Parameters
3480 The following values are to be added to the "Media Clock Source
3481 Parameters" subegistry in the "Session Description Protocol (SDP)
3482 Parameters" registry. The references should be updated to point at
3483 this RFC as well as the previous references.
3485 +-----------+--------------+
3486 | Name | Mux Category |
3487 +-----------+--------------+
3488 | sender | NORMAL |
3489 | direct | NORMAL |
3490 | IEEE1722 | NORMAL |
3491 +-----------+--------------+
3493 16. Security Considerations
3495 This document does not add any new security considerations beyond the
3496 existing considerations in the RFC for protocols that are being
3497 multiplexed together.
3499 The ways that SRTP streams are keyed is not believed to create any
3500 two-time pad vulnerability for the currently defined SRTP keying
3501 mechanism.
3503 17. Acknowledgments
3505 I would like to thank Cullen Jennings, Flemming Andreasen for
3506 suggesting the categories, contributing text and reviewing the draft.
3507 I would also link to thank Magnus Westerlund, Christer Holmberg,
3508 Jonathan Lennox, Bo Burman, and Dan Wing on suggesting structural
3509 changes helping improve the document readability.
3511 I would like also to thank following experts on their inputs and
3512 reviews as listed - Flemming Andreasen(5.24,5.32,5.33,14), Rohan
3513 Mahy(5.57), Eric Burger(5.26),Christian Huitema(5.14), Christer
3514 Holmberg(5.21,5.26,5.51,5.52), Richard Ejzak (5.44,5.53,5.54), Colin
3515 Perkins(5.7,5.8,5.9,5.58), Magnus
3516 westerlund(5.2,5.3,5.9,5.27,5.47,6.1,6.2,6.3,8.3,7), Roni
3517 Evens(5.12,5.27,8.4), Subha Dhesikan(5.6,10), Dan
3518 Wing(5.7,5.12,5.35,5.39,5.45), Cullen Jennings (5.40), Ali C
3519 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
3520 (7.2,7.6), Charles Eckel(5.15,5.27,5.28,9.1,8.5), Paul Kyzivat(5.24),
3521 Ian Johansson(5.15), Saravanan Shanmugham(5.11), Paul E Jones(5.30),
3522 Rajesh Kumar(5.48), Jonathan Lennox(5.36,5,15,9.1,11.1), Mo
3523 Zanaty(5.4,5.5,5.23,8.1,8.3,8.5,12.1), Christian Huitema (5.14), Qin
3524 Wu (5.47 PM-Dir review), Hans Stokking(5.43,5.16).
3526 18. Change Log
3528 [RFC EDITOR NOTE: Please remove this section when publishing]
3530 Changes from draft-ietf-mmusic-sdp-mux-attributes-04
3532 o Fixed minor nits overall.
3534 o Updated Acknowledgement Sections
3536 o Last Call Version.
3538 Changes from draft-ietf-mmusic-sdp-mux-attributes-03
3540 o More re-work on the IANA section.
3542 o Clean ups preparing for the last call.
3544 Changes from draft-ietf-mmusic-sdp-mux-attributes-02
3546 o Incorporated suggestions from Flemming on Capability Negotiation.
3548 o Closed open issues from IETF90
3550 o Added IANA section to list the categories for all the SDP
3551 attributes anlayzed
3553 o Lots of cleanup
3555 o Reformatted Refernces section to use short-form notation
3557 Changes from draft-ietf-mmusic-sdp-mux-attributes-01
3559 o Updated section 15 to provide detailed recommendation on dealing
3560 with encapsulating attributes. Also updated sections 5.20, 5.28,
3561 5.29 to refer to Section 15.
3563 o Added new categories IDENTICAL-PER-PT and INHERIT
3565 o Updated Sections 16 to add the new categories.
3567 o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the
3568 category IDENTICAL-PER-PT.
3570 o Reformatted section 4 to add individual categories to their own
3571 sections.
3573 Changes from draft-ietf-mmusic-sdp-mux-attributes-00
3575 o Added Section 15 to provide recommendations on multiplexing SDP
3576 encapsulating attributes. Also updated sections 5.20, 5.28, 5.29
3577 to refer to Section 15.
3579 o Updated Section 5.38 to incorporate PM-dir review inputs from Qin
3580 Wu
3582 o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more
3583 clarity.
3585 o Fixed few nits regarding sentence clarity and fill-in the NOTES
3586 section where information was lacking.
3588 Changes from draft-nandakumar-mmusic-mux-attributes-05
3590 o Renamed the document to be a WG document.
3592 o Added Section 14.
3594 o Updated Open Issues based on IETF88 discussions.
3596 Changes from draft-nandakumar-mmusic-mux-attributes-04
3598 o Added few OPEN ISSUES that needs to be discussed.
3600 o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4,
3601 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1
3603 o Updated Table Column name Current to Level and improved TRANSPORT
3604 category explanation on suggestions form Dan Wing.
3606 o Grouped all the rtcp-fb attribute analysis under a single section
3607 as suggested by Magnus/
3609 Changes from draft-nandakumar-mmusic-mux-attributes-03
3610 o Maintenance change to clean up grammatical nits and wordings.
3612 Changes from draft-nandakumar-mmusic-mux-attributes-02
3614 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34,
3615 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
3616 the inputs from the respective RFC Authors.
3618 Changes from draft-nandakumar-mmusic-mux-attributes-01
3620 o Replaced Category BAD with NOT RECOMMENDED.
3622 o Added Category TBD.
3624 o Updated IANA Consideration Section.
3626 Changes from draft-nandakumar-mmusic-mux-attributes-00
3628 o Added new section for dealing with FEC payload types.
3630 19. References
3632 19.1. Normative References
3634 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
3635 Requirement Levels", BCP 14, RFC 2119, March 1997.
3637 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
3638 Description Protocol", RFC 4566, July 2006.
3640 19.2. Informative References
3642 [H.248.15]
3643 "Gateway control protocol: SDP H.248 package attribute",
3644 .
3646 [I-D.ietf-mmusic-sdp-bundle-negotiation]
3647 Holmberg, C., Alvestrand, H., and C. Jennings,
3648 "Negotiating Media Multiplexing Using the Session
3649 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
3650 negotiation-12 (work in progress), October 2014.
3652 [I.D-draft-ietf-dart-dscp-rtp]
3653 Black, D. and P. Jones, "The Session Description Protocol
3654 (SDP) Content Attribute", draft-ietf-dart-dscp-rtp-07
3655 (work in progress), September 2014.
3657 [IANA] "Session Description Protocol (SDP) Parameters",
3658 .
3661 [ITU-T-REC.Q1970]
3662 "Q.1970 : BICC IP bearer control protocol",
3663 .
3665 [R3GPPTS183.063]
3666 "TISPAN - IMS based ITPV Stage 3 specification.",
3667 .
3670 [R3GPPTS24.182]
3671 "IP Multimedia Subsystem (IMS) Customized Alerting Tones
3672 (CAT); Protocol specification",
3673 .
3675 [R3GPPTS24.183]
3676 "IP Multimedia Subsystem (IMS) Customized Ringing Signal
3677 (CRS); Protocol specification",
3678 .
3680 [R3GPPTS24.229]
3681 "IP multimedia call control protocol based on Session
3682 Initiation Protocol (SIP) and Session Description Protocol
3683 (SDP);",
3684 .
3686 [R3GPPTS26.114]
3687 "IP multimedia Subsystem : Media Handling and
3688 interaction",
3689 .
3691 [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the
3692 Session Description Protocol (SDP) for ATM Bearer
3693 Connections", RFC 3108, May 2001.
3695 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
3696 with Session Description Protocol (SDP)", RFC 3264, June
3697 2002.
3699 [RFC3312] Camarillo, G., Marshall, W., and J. Rosenberg,
3700 "Integration of Resource Management and Session Initiation
3701 Protocol (SIP)", RFC 3312, October 2002.
3703 [RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple
3704 Capability Declaration", RFC 3407, October 2002.
3706 [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to
3707 Resource Reservation Flows", RFC 3524, April 2003.
3709 [RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth
3710 Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC
3711 3556, July 2003.
3713 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
3714 in Session Description Protocol (SDP)", RFC 3605, October
3715 2003.
3717 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
3718 Protocol Extended Reports (RTCP XR)", RFC 3611, November
3719 2003.
3721 [RFC3890] Westerlund, M., "A Transport Independent Bandwidth
3722 Modifier for the Session Description Protocol (SDP)", RFC
3723 3890, September 2004.
3725 [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network
3726 Address Types (ANAT) Semantics for the Session Description
3727 Protocol (SDP) Grouping Framework", RFC 4091, June 2005.
3729 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
3730 the Session Description Protocol (SDP)", RFC 4145,
3731 September 2005.
3733 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E.
3734 Carrara, "Key Management Extensions for Session
3735 Description Protocol (SDP) and Real Time Streaming
3736 Protocol (RTSP)", RFC 4567, July 2006.
3738 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
3739 Description Protocol (SDP) Security Descriptions for Media
3740 Streams", RFC 4568, July 2006.
3742 [RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol
3743 (SDP) Source Filters", RFC 4570, July 2006.
3745 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
3746 Transport Layer Security (TLS) Protocol in the Session
3747 Description Protocol (SDP)", RFC 4572, July 2006.
3749 [RFC4574] Levin, O. and G. Camarillo, "The Session Description
3750 Protocol (SDP) Label Attribute", RFC 4574, August 2006.
3752 [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format
3753 for Binary Floor Control Protocol (BFCP) Streams", RFC
3754 4583, November 2006.
3756 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
3757 "Extended RTP Profile for Real-time Transport Control
3758 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July
3759 2006.
3761 [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description
3762 Protocol (SDP) Content Attribute", RFC 4796, February
3763 2007.
3765 [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
3766 Session Relay Protocol (MSRP)", RFC 4975, September 2007.
3768 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
3769 "Codec Control Messages in the RTP Audio-Visual Profile
3770 with Feedback (AVPF)", RFC 5104, February 2008.
3772 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error
3773 Correction", RFC 5109, December 2007.
3775 [RFC5159] Dondeti, L. and A. Jerichow, "Session Description Protocol
3776 (SDP) Attributes for Open Mobile Alliance (OMA) Broadcast
3777 (BCAST) Service and Content Protection", RFC 5159, March
3778 2008.
3780 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
3781 (ICE): A Protocol for Network Address Translator (NAT)
3782 Traversal for Offer/Answer Protocols", RFC 5245, April
3783 2010.
3785 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP
3786 Header Extensions", RFC 5285, July 2008.
3788 [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of
3789 Service (QoS) Mechanism Selection in the Session
3790 Description Protocol (SDP)", RFC 5432, March 2009.
3792 [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size
3793 Real-Time Transport Control Protocol (RTCP): Opportunities
3794 and Consequences", RFC 5506, April 2009.
3796 [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
3797 and P. Kyzivat, "A Session Description Protocol (SDP)
3798 Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
3799 May 2009.
3801 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
3802 Media Attributes in the Session Description Protocol
3803 (SDP)", RFC 5576, June 2009.
3805 [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding
3806 Dependency in the Session Description Protocol (SDP)", RFC
3807 5583, July 2009.
3809 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
3810 Protocol (RTCP) Extensions for Single-Source Multicast
3811 Sessions with Unicast Feedback", RFC 5760, February 2010.
3813 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
3814 Control Packets on a Single Port", RFC 5761, April 2010.
3816 [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control
3817 Protocol (DCCP)", RFC 5762, April 2010.
3819 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
3820 for Establishing a Secure Real-time Transport Protocol
3821 (SRTP) Security Context Using Datagram Transport Layer
3822 Security (DTLS)", RFC 5763, May 2010.
3824 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
3825 Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
3827 [RFC5939] Andreasen, F., "Session Description Protocol (SDP)
3828 Capability Negotiation", RFC 5939, September 2010.
3830 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in
3831 the Session Description Protocol", RFC 5956, September
3832 2010.
3834 [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions
3835 Defined for 3GPP Packet-Switched Streaming Service and
3836 Multimedia Broadcast/Multicast Service", RFC 6064, January
3837 2011.
3839 [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source-
3840 Specific Multicast (SSM) Sessions", RFC 6128, February
3841 2011.
3843 [RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
3844 Path Key Agreement for Unicast Secure RTP", RFC 6189,
3845 April 2011.
3847 [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for
3848 the Internet Key Exchange Protocol (IKE) in the Session
3849 Description Protocol (SDP)", RFC 6193, April 2011.
3851 [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media
3852 Control Channel Framework", RFC 6230, May 2011.
3854 [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image
3855 Attributes in the Session Description Protocol (SDP)", RFC
3856 6236, May 2011.
3858 [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping
3859 between Unicast and Multicast RTP Sessions", RFC 6284,
3860 June 2011.
3862 [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
3863 "Unicast-Based Rapid Acquisition of Multicast RTP
3864 Sessions", RFC 6285, June 2011.
3866 [RFC6364] Begen, A., "Session Description Protocol Elements for the
3867 Forward Error Correction (FEC) Framework", RFC 6364,
3868 October 2011.
3870 [RFC6642] Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP)
3871 Extension for a Third-Party Loss Report", RFC 6642, June
3872 2012.
3874 [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
3875 and K. Carlberg, "Explicit Congestion Notification (ECN)
3876 for RTP over UDP", RFC 6679, August 2012.
3878 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
3879 Establishment for Media Anchoring (CEMA) for the Message
3880 Session Relay Protocol (MSRP)", RFC 6714, August 2012.
3882 [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
3883 Datagram Congestion Control Protocol UDP Encapsulation for
3884 NAT Traversal", RFC 6773, November 2012.
3886 [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control
3887 Protocol Version 2 (MRCPv2)", RFC 6787, November 2012.
3889 [RFC6849] Kaplan, H., Hedayat, K., Venna, N., Jones, P., and N.
3890 Stratton, "An Extension to the Session Description
3891 Protocol (SDP) and Real-time Transport Protocol (RTP) for
3892 Media Loopback", RFC 6849, February 2013.
3894 [RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session
3895 Description Protocol (SDP) Media Capabilities
3896 Negotiation", RFC 6871, February 2013.
3898 [RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S.
3899 Veikkolainen, "The Session Description Protocol (SDP)
3900 Alternate Connectivity (ALTC) Attribute", RFC 6947, May
3901 2013.
3903 [RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman,
3904 "Miscellaneous Capabilities Negotiation in the Session
3905 Description Protocol (SDP)", RFC 7006, September 2013.
3907 [RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping
3908 Semantics in the Session Description Protocol", RFC 7104,
3909 January 2014.
3911 [RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session
3912 Description Protocol (SDP) Extension for Setting Audio and
3913 Video Media Streams over Circuit-Switched Bearers in the
3914 Public Switched Telephone Network (PSTN)", RFC 7195, May
3915 2014.
3917 [RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay
3918 Attribute in the Session Description Protocol", RFC 7197,
3919 April 2014.
3921 [RFC7266] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control
3922 Protocol (RTCP) Extended Report (XR) Blocks for Mean
3923 Opinion Score (MOS) Metric Reporting", RFC 7266, June
3924 2014.
3926 [RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O.,
3927 Boronat, F., Montagud, M., and K. Gross, "Inter-
3928 Destination Media Synchronization (IDMS) Using the RTP
3929 Control Protocol (RTCP)", RFC 7272, June 2014.
3931 [RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H.
3932 Stokking, "RTP Clock Source Signalling", RFC 7273, June
3933 2014.
3935 [T.38] "Procedures for real-time Group 3 facsimile communication
3936 over IP networks", .
3938 Author's Address
3940 Suhas Nandakumar
3941 Cisco
3942 170 West Tasman Drive
3943 San Jose, CA 95134
3944 USA
3946 Email: snandaku@cisco.com