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2 Network Working Group S. Nandakumar
3 Internet-Draft Cisco
4 Intended status: Standards Track October 24, 2014
5 Expires: April 27, 2015
7 A Framework for SDP Attributes when Multiplexing
8 draft-ietf-mmusic-sdp-mux-attributes-04
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 April 27, 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 . . . . . . . . . . . . . . . 11
87 5.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 12
88 5.2. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 13
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 . . . . . . . . . . . . . 20
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. RFC7226 - 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 . . . . . . . . . . . . . . . . . . . . . . . . . 36
131 5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP) . . 36
132 5.44. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . 37
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 . . . . . . . 39
136 5.48. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . . 42
137 5.49. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 43
138 5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . . 44
139 5.51. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 44
140 5.52. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 44
141 5.53. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 45
142 5.54. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 46
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. RFC4574 - SDP Label Attribute . . . . . . . . . . . . . . 48
147 5.59. Historical Attributes . . . . . . . . . . . . . . . . . . 48
148 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 49
149 6.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 49
150 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . 49
151 6.3. RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . 50
152 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 51
153 7.1. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 51
154 7.2. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 52
155 7.3. RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . 53
156 7.4. RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . . 53
157 7.5. RFC6642 - Third-Party Loss Report . . . . . . . . . . . . 54
158 7.6. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 55
159 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 55
160 8.1. RFC5888 - SDP Grouping Framework . . . . . . . . . . . . 55
161 8.2. RFC3524 - Mapping Media Streams to Resource
162 Reservation Flows . . . . . . . . . . . . . . . . . . . . 56
163 8.3. RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . 56
164 8.4. RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . . 56
165 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP . . 57
166 8.6. RFC7104 - Duplication Grouping Semantics in the SDP . . 57
167 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 58
168 9.1. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 58
169 9.2. RFC7104 - Duplication Grouping Semantics in the SDP . . . 58
170 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 58
171 10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 58
172 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 59
173 11.1. RFC4566 SDP: Session Description Protocol . . . . . . . 59
174 12. content Attribute Analysis . . . . . . . . . . . . . . . . . 59
175 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 59
176 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 60
177 13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . 60
178 14. Multiplexing Considerations for Encapsulating Attributes . . 60
179 14.1. RFC3407 - cpar Attribute Analysis . . . . . . . . . . . 61
180 14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 61
181 14.2.1. Recommendation - Procedures for Potential
182 Configuration Pairing . . . . . . . . . . . . . . . 62
183 14.2.1.1. Example: Transport Capability Multiplexing . . . 63
184 14.2.1.2. Example: Attribute Capability Multiplexing . . . 64
185 14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 65
186 14.3.1. Recommendation: Dealing with Payload Type Numbers . 65
187 14.3.1.1. Example: Attribute Capability Under Shared
188 Payload Type . . . . . . . . . . . . . . . . . . 65
189 14.3.2. Recommendation: Dealing with Latent Configurations . 66
190 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 67
191 15.1. New 'Multiplexing Categories' subregistry . . . . . . . 67
192 15.2. 'Mux Category' column for subregistries . . . . . . . . 68
193 15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 68
194 15.2.2. Table: att-field (session level) . . . . . . . . . . 68
195 15.2.3. Table: att-field (both session and media level) . . 69
196 15.2.4. Table: att-field (media level only) . . . . . . . . 71
197 15.2.5. Table: att-field (source level) . . . . . . . . . . 74
198 15.2.6. Table: content SDP Parameters . . . . . . . . . . . 74
199 15.2.7. Table: Semantics for the 'group' SDP Attribute . . . 75
200 15.2.8. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 75
201 15.2.9. Table: 'ack' and 'nack' Attribute Values . . . . . . 76
202 15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . . 76
203 15.2.11. Table: 'cs-correlation' Attribute Values . . . . . . 76
204 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 77
205 15.2.13. Table: SDP/RTSP key management protocol identifiers 77
206 15.2.14. Table: Codec Control Messages . . . . . . . . . . . 77
207 15.2.15. Table: QoS Mechanism Tokens . . . . . . . . . . . . 78
208 15.2.16. Table: SDP Capability Negotiation Option Tags . . . 78
209 15.2.17. Table: Timestamp Reference Clock Source Parameters . 78
210 15.2.18. Table: Media Clock Source Parameters . . . . . . . . 79
211 16. Security Considerations . . . . . . . . . . . . . . . . . . . 79
212 17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 79
213 18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 80
214 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 82
215 19.1. Normative References . . . . . . . . . . . . . . . . . . 82
216 19.2. Informative References . . . . . . . . . . . . . . . . . 82
217 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 88
219 1. Introduction
221 Real-Time Communication Web (RTCWeb) framework requires Real-time
222 Transport Protocol (RTP) as the media transport protocol and Session
223 Description Protocol (SDP) [RFC4566] for describing and negotiating
224 multi-media communication sessions.
226 SDP defines several attributes for capturing characteristics that
227 apply to the individual media descriptions (described by "m=" lines")
228 and the overall multimedia session. Typically different media types
229 (audio, video etc) described using different media descriptions
230 represent separate RTP Sessions that are carried over individual
231 transport layer flows. However in the IETF RTCWEB WG, a need to use
232 a single 5-tuple for sending and receiving media associated with
233 multiple SDP media descriptions ("m=" lines) has been identified.
234 This would for e.g. allow the usage of a single set of Interactive
235 Connectivity Establishment (ICE) [RFC5245] candidates for multiple
236 media descriptions. This in turn has made necessary to understand
237 the interpretation and usage of the SDP attributes defined for the
238 multiplexed media descriptions.
240 Given the number of SDP attributes registered with the [IANA] and
241 possibility of new attributes being defined in the future, there is
242 need for generic future-proof framework to analyze these attributes
243 for their applicability in the transport multiplexing use-cases.
245 The document starts with providing the motivation for requiring such
246 a framework. This is followed by introduction to the SDP attribute
247 analysis framework/procedures, following which several sections
248 applies the framework to the SDP attributes registered with the
249 [IANA].
251 2. Terminology
253 The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
254 "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
255 interpreted as described in [RFC2119].
257 3. Motivation
259 The time and complications of setting up ICE [RFC5245] and DTLS-SRTP
260 [RFC5763] transports for use by RTP, and conservation of ports, forms
261 an requirement to try and reduce the number of transport level flows
262 needed. This has resulted in the definition of ways, such as,
263 [I-D.ietf-mmusic-sdp-bundle-negotiation] to multiplex RTP over a
264 single transport flow in order to preserve network resources such as
265 port numbers. This imposes further restrictions on applicability of
266 these SDP attributes as they are defined today.
268 The specific problem is that there are attribute combinations which
269 make sense when specified on independent "m= "lines -- as with
270 classical SDP -- that do not make sense when those "m="" lines are
271 then multiplexed over the same transport. To give an obvious
272 example, ICE permits each "m=" line to have an independently
273 specified ice-ufrag attribute. However, if the media from multiple
274 "m=" lines is multiplexed over the same ICE component, then the
275 meaning of media-level ice-ufrag attributes becomes muddled.
277 As of today there are close to 250 SDP attributes registered with the
278 [IANA] and more will be added in the future. There is no clearly
279 defined procedure to establish the validity/applicability of these
280 attribute when used with transport multiplexing.
282 4. SDP Attribute Analysis Framework
284 Attributes in an SDP session description can be defined at the
285 session-level and media-level. These attributes could be
286 semantically grouped as noted below.
288 o Attributes related to media content such as media type, encoding
289 schemes, payload types.
291 o Attributes specifying media transport characteristics like RTP/
292 RTCP port numbers, network addresses, QOS.
294 o Metadata description attributes capturing session timing and
295 origin information.
297 o Attributes establishing relationships between media streams such
298 as grouping framework
300 With the above semantic grouping as a reference, the proposed
301 framework classifies each attribute into one of the following
302 categories:
304 4.1. Category: NORMAL
306 Attributes that can be independently specified when multiplexing and
307 retain their original semantics.
309 In the example given below, the direction and label attributes are
310 independently specified for audio and video m=lines. These
311 attributes are not impacted by multiplexing these media streams over
312 a single transport layer flow.
314 v=0
315 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
316 s=
317 c=IN IP4 host.atlanta.example.com
318 t=0 0
319 m=audio 49172 RTP/AVP 99
320 a=sendonly
321 a=label:1
322 a=rtpmap:99 iLBC/8000
323 m=video 49172 RTP/AVP 31
324 a=recvonly
325 a=label:2
326 a=rtpmap:31 H261/90000
328 4.2. Category: NOT RECOMMENDED
330 Attributes that are recommended against multiplexing since their
331 usage under multiplexing might lead to incorrect behavior.
333 Example: Multiplexing media descriptions having attribute zrtp-hash
334 defined with the media descriptions lacking it, would either
335 complicate the handling of multiplexed streams or might fail
336 multiplexing altogether.
338 v=0
339 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
340 s=
341 c=IN IP4 client.biloxi.example.com
342 t=0 0
343 m=audio 3456 RTP/AVP 97 // with zrtp
344 a=rtpmap:97 iLBC/8000
345
346 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
347 df881ae642c371ba46df
348
349 m=video 34567 RTP/AVP 31 //without zrtp
350 a=rtpmap:31 H261/90000
352 4.3. Category: IDENTICAL
354 Attributes that MUST be identical across all the media descriptions
355 being multiplexed.
357 Attributes such as rtcp-mux fall into this category. Since RTCP
358 reporting is done per RTP Session, RTCP Multiplexing MUST to enabled
359 for both the audio and video m=lines in the example below if they are
360 transported over a single 5-tuple.
362 v=0
363 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
364 s=
365 c=IN IP4 client.biloxi.example.com
366 t=0 0
367 m=audio 34567 RTP/AVP 97
368 a=rtcp-mux
369 m=video 34567 RTP/AVP 31
370 a=rtpmap:31 H261/90000
371 a=rtcp-mux
373 4.4. Category: SUM
375 Attributes can be set as they are normally used but software using
376 them in the multiplexing scenario, MUST apply the sum of all the
377 attributes being multiplexed instead of trying to use them
378 independently. This is typically used for bandwidth or other rate
379 limiting attributes to the underlying transport.
381 The software parsing the SDP sample below, should use the aggregate
382 Application Specific (AS) bandwidth value from the individual media
383 descriptions to determine the AS value for the multiplexed session.
384 Thus the calculated AS value would be 256+64 bytes for the given
385 example.
387 v=0
388 o=test 2890844526 2890842807 IN IP4 126.16.64.4
389 c=IN IP4 client.biloxi.example.com
390 t=0 0
391 m=audio 49170 RTP/AVP 0
392 b=AS:64
393 m=video 51372 RTP/AVP 31
394 b=AS:256
396 4.5. Category: TRANSPORT
398 Attributes that can be set normally for multiple items in a
399 multiplexed group but the software MUST pick just one of the
400 attribute of the given type for use. The one chosen is the attribute
401 associated with the "m=" line that represents the information being
402 used for the transport of the RTP.
404 In the example below, "a=crypto" attribute is defined for both the
405 audio and the video m=lines. The video media line's a=crypto
406 attribute is chosen since its mid value (bar) appears first in the
407 a=group:BUNDLE line. This is due to BUNDLE grouping semantic
408 [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values
409 from m=line corresponding to the mid appearing first on the
410 a=group:BUNDLE line to be considered for setting up the RTP
411 Transport.
413 v=0
414 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
415 s=
416 c=IN IP4 host.atlanta.example.com
417 t=0 0
418 a=group:BUNDLE bar foo
419 m=audio 49172 RTP/AVP 99
420 a=mid:foo
421 a=crypto:1 AES_CM_128_HMAC_SHA1_80
422 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32
423 a=rtpmap:99 iLBC/8000
424 m=video 51374 RTP/AVP 31
425 a=mid:bar
426 a=crypto:1 AES_CM_128_HMAC_SHA1_80
427 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
428 a=rtpmap:96 H261/90000
430 4.6. Category: INHERIT
432 Attributes that encapsulate other SDP attributes or parameters.
433 These attributes inherit their multiplexing characteristics from the
434 attributes or parameters they encapsulate. Such attributes as of
435 today, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of a
436 generic framework for indicating and negotiating transport, media and
437 media format related capabilities in the SDP.
439 The inheritance manifests itself when the encapsulated attribute or
440 parameter is being leveraged. In the case of SDP Capability
441 Negotiation [RFC5939] for example, this occurs when a capability
442 (encapsulating attribute) is used as part of a configuration; the
443 configuration inherits the multiplexing category of each of its
444 constituent (encapsulated) attributes and parameters. This in turn
445 may place constraints on what constitutes a valid configuration from
446 a multiplexing point of view, e.g. because some attributes must be
447 IDENTICAL (see Section 14 for further details).
449 v=0
450 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
451 s=
452 c=IN IP4 host.atlanta.example.com
453 t=0 0
454 m=video 3456 RTP/AVP 100
455 a=rtpmap:100 VP8/90000
456 a=fmtp:100 max-fr=30;max-fs=8040
457 a=sqn: 0
458 a=cdsc: 1 video RTP/AVP 100
459 a=cpar: a=rtcp-mux
460 m=video 3456 RTP/AVP 101
461 a=rtpmap:101 VP8/90000
462 a=fmtp:100 max-fr=15;max-fs=1200
463 a=cdsc: 2 video RTP/AVP 101
464 a=cpar: a=rtcp-mux
466 In the above example , the category IDENTICAL is inherited for the
467 cpar encapsulated rtcp-mux attribute.
469 4.7. Category: IDENTICAL-PER-PT
471 Attributes that define the RTP payload configuration on per Payload
472 Type basis and MUST have identical values across all the media
473 descriptions for a given RTP Payload Type when repeated.
475 In the SDP example below, Payload Types 96 and 97 are repeated across
476 all the video m= lines and all the payload specific parameters (ex:
477 rtpmap, fmtp) are identical.
479 v=0
480 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
481 s=
482 c=IN IP4 host.atlanta.example.com
483 t=0 0
484 a=group:BUNDLE cam1, cam2
485 m = video 96 97
486 a=mid:cam1
487 a=rtpmap:96 H264/90000
488 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
489 max-mbps=108000; max-br=1000
490 a=rtpmap:97 H264/90000
491 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
492 max-mbps=7200; max-br=200
493 m = video 96 97
494 a=mid:cam2
495 a=rtpmap:96 H264/90000
496 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
497 max-mbps=108000; max-br=1000
498 a=rtpmap:97 H264/90000
499 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
500 max-mbps=7200; max-br=200
502 4.8. Category: SPECIAL
504 Attributes where the text in the source draft must be consulted for
505 further handling when multiplexed.
507 As an example, for the attribute extmap, the specification defining
508 the extension MUST be referred to understand the multiplexing
509 implications.
511 4.9. Category: TBD
513 Attributes that have not been analyzed under the proposed
514 multiplexing framework yet. For the purposes of implementations it
515 is advised to consider "NOT RECOMMENDED" as the category when
516 multiplexing these attributes.
518 5. Analysis of Existing Attributes
520 This section analyzes attributes listed in [IANA] grouped under the
521 IETF document that defines them. The "Level" column indicates
522 whether the attribute is currently specified as:
524 o S -- Session level
526 o M -- Media level
527 o B -- Both
529 o SR -- Source-level (for a single SSRC)
531 5.1. RFC4566 - SDP: Session Description Protocol
533 [RFC4566] defines the Session Description Protocol (SDP) that is
534 intended for describing multimedia sessions for the purposes of
535 session announcement, session invitation, and other forms of
536 multimedia session initiation.
538 +-----------------+---------------------+-------+-------------------+
539 | Attr Name | Notes | Level | Category |
540 +-----------------+---------------------+-------+-------------------+
541 | sendrecv | Not impacted | B | NORMAL |
542 | | | | |
543 | sendonly | Not impacted | B | NORMAL |
544 | | | | |
545 | recvonly | Not impacted | B | NORMAL |
546 | | | | |
547 | inactive | Not impacted | B | NORMAL |
548 | | | | |
549 | cat | Not impacted | S | NORMAL |
550 | | | | |
551 | ptime | The attribute value | M | IDENTICAL-PER-PT |
552 | | must be same for a | | |
553 | | given codec | | |
554 | | configuration | | |
555 | | | | |
556 | maxptime | The attribute value | M | IDENTICAL-PER-PT |
557 | | must be same for a | | |
558 | | given codec | | |
559 | | configuration | | |
560 | | | | |
561 | orient | Not Impacted | M | NORMAL |
562 | | | | |
563 | framerate | The attribute value | M | IDENTICAL-PER-PT |
564 | | must be same for a | | |
565 | | given codec | | |
566 | | configuration | | |
567 | | | | |
568 | quality | Not Impacted | M | NORMAL |
569 | | | | |
570 | rtpmap | The attribute value | M | IDENTICAL-PER-PT |
571 | | must be same for a | | |
572 | | given codec | | |
573 | | configuration | | |
574 | | | | |
575 | fmtp | The attribute value | M | IDENTICAL-PER-PT |
576 | | must be same for a | | |
577 | | given codec | | |
578 | | configuration | | |
579 | | | | |
580 | keywds | Not impacted | S | NORMAL |
581 | | | | |
582 | type | Not Impacted | S | NORMAL |
583 | | | | |
584 | type:broadcast | Not Impacted | S | NORMAL |
585 | | | | |
586 | type:H332 | Not Impacted | S | NORMAL |
587 | | | | |
588 | type:meeting | Not Impacted | S | NORMAL |
589 | | | | |
590 | type:moderated | Not Impacted | S | NORMAL |
591 | | | | |
592 | type:test | Not Impacted | S | NORMAL |
593 | | | | |
594 | tool | Not Impacted | S | NORMAL |
595 | | | | |
596 | charset | Not Impacted | S | NORMAL |
597 | | | | |
598 | sdplang | Not Impacted | B | NORMAL |
599 | | | | |
600 | lang | Not Impacted | B | NORMAL |
601 | | | | |
602 +-----------------+---------------------+-------+-------------------+
604 RFC4566 Attribute Analysis
606 5.2. RFC4585 - RTP/AVPF
608 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that
609 enables receivers to provide, statistically, more immediate feedback
610 to the senders and thus allows for short-term adaptation and
611 efficient feedback-based repair mechanisms to be implemented.
613 +----------+----------------------------+-------+-------------------+
614 | Attr | Notes | Level | Category |
615 | Name | | | |
616 +----------+----------------------------+-------+-------------------+
617 | rtcp-fb | Since RTCP feedback | M | IDENTICAL-PER-PT |
618 | | attributes are Payload | | |
619 | | Type (PT) scoped, their | | |
620 | | values MUST be identical | | |
621 | | for a given PT across the | | |
622 | | multiplexed m=lines. | | |
623 | | | | |
624 +----------+----------------------------+-------+-------------------+
626 RFC4585 Attribute Analysis
628 5.3. RFC5761 - Multiplexing RTP and RTCP
630 [RFC5761] discusses issues that arise when multiplexing RTP data
631 packets and RTP Control Protocol (RTCP) packets on a single UDP port.
632 It describes when such multiplexing is and is not appropriate, and it
633 explains how the Session Description Protocol (SDP) can be used to
634 signal multiplexed sessions.
636 +-----------+----------------------------------+-------+------------+
637 | Name | Notes | Level | Category |
638 +-----------+----------------------------------+-------+------------+
639 | rtcp-mux | RTP and RTCP Multiplexing | M | IDENTICAL |
640 | | affects the entire RTP Session | | |
641 | | | | |
642 +-----------+----------------------------------+-------+------------+
644 RFC5761 Attribute Analysis
646 5.4. RFC3312 - Integration of Resource Management and (SIP)
648 [RFC3312] defines a generic framework for preconditions, which are
649 extensible through IANA registration. This document also discusses
650 how network quality of service can be made a precondition for
651 establishment of sessions initiated by the Session Initiation
652 Protocol (SIP). These preconditions require that the participant
653 reserve network resources before continuing with the session.
655 +-------+-----------------------+-------+------------------+
656 | Name | Notes | Level | Category |
657 +-------+-----------------------+-------+------------------+
658 | des | Refer to notes below | M | NOT RECOMMENDED |
659 | | | | |
660 | conf | Refer to notes below | M | NOT RECOMMENDED |
661 | | | | |
662 | curr | Refer to notes below | M | NOT RECOMMENDED |
663 | | | | |
664 +-------+-----------------------+-------+------------------+
666 RFC3312 Attribute Analysis
668 A mismatched set of Preconditions across media descriptions results
669 in Session establishment failures due to inability to meet the right
670 resource reservations requested.
672 5.5. RFC4574 - SDP Label Attribute
674 [RFC4574] defines a new Session Description Protocol (SDP) media-
675 level attribute: "label". The "label" attribute carries a pointer to
676 a media stream in the context of an arbitrary network application
677 that uses SDP. The sender of the SDP document can attach the "label"
678 attribute to a particular media stream or streams. The application
679 can then use the provided pointer to refer to each particular media
680 stream in its context.
682 +--------+---------------+-------+----------+
683 | Name | Notes | Level | Category |
684 +--------+---------------+-------+----------+
685 | label | Not Impacted | M | NORMAL |
686 | | | | |
687 +--------+---------------+-------+----------+
689 RFC4574 Attribute Analysis
691 5.6. RFC5432 - QoS Mechanism Selection in SDP
693 [RFC5432] defines procedures to negotiate QOS mechanisms using the
694 Session Description Protocol (SDP) offer/answer model.
696 +----------------+------------------------+-------+----------+
697 | Name | Notes | Level | Category |
698 +----------------+------------------------+-------+----------+
699 | qos-mech-send | Refer to notes below | B | NORMAL |
700 | | | | |
701 | qos-mech-recv | Refer to notes below. | B | NORMAL |
702 | | | | |
703 +----------------+------------------------+-------+----------+
705 RFC5432 Attribute Analysis
707 A single DSCP code point per flow being multiplexed doesn't impact
708 multiplexing since QOS mechanisms are signaled/scoped per flow.For
709 scenarios that involves having different DSCP for packets being
710 transmitted over the same 5-tuple, has issues as discussed in
711 [I.D-draft-ietf-dart-dscp-rtp]
713 5.7. RFC4568 - SDP Security Descriptions
715 [RFC4568] defines a Session Description Protocol (SDP) cryptographic
716 attribute for unicast media streams. The attribute describes a
717 cryptographic key and other parameters that serve to configure
718 security for a unicast media stream in either a single message or a
719 roundtrip exchange.
721 +---------+------------------------------------+-------+------------+
722 | Name | Notes | Level | Category |
723 +---------+------------------------------------+-------+------------+
724 | crypto | crypto attribute must be the one | M | TRANSPORT |
725 | | that corresponds to the "m=" line | | |
726 | | chosen for setting up the | | |
727 | | underlying transport flow | | |
728 | | | | |
729 +---------+------------------------------------+-------+------------+
731 RFC4568 Attribute Analysis
733 5.8. RFC5762 - RTP over DCCP
735 The Real-time Transport Protocol (RTP) is a widely used transport for
736 real-time multimedia on IP networks. The Datagram Congestion Control
737 Protocol (DCCP) is a transport protocol that provides desirable
738 services for real-time applications. [RFC5762] specifies a mapping
739 of RTP onto DCCP, along with associated signaling, such that real-
740 time applications can make use of the services provided by DCCP.
742 +--------------------+---------------------+---------+--------------+
743 | Name | Notes | Current | Category |
744 +--------------------+---------------------+---------+--------------+
745 | dccp-service-code | If RFC6773 is not | M | NOT |
746 | | being used in | | RECOMMENDED |
747 | | addition to | | |
748 | | RFC5762, the port | | |
749 | | in the "m=" line is | | |
750 | | a DCCP port. DCCP | | |
751 | | being a connection | | |
752 | | oriented protocol, | | |
753 | | does not allow | | |
754 | | multiple | | |
755 | | connections on the | | |
756 | | same 5-tuple. | | |
757 | | | | |
758 +--------------------+---------------------+---------+--------------+
760 RFC5762 Attribute Analysis
762 If RFC6773 is being used in addition to RFC5762 and provided that
763 DCCP-in-UDP layer has additional demultiplexing, then it may be
764 possible to use different DCCP service codes for each DCCP flow,
765 given each uses a different DCCP port. Although doing so might
766 conflict with the media type of the "m=" line. None of this is
767 standardized yet and it wouldn't work as explained. Hence
768 multiplexing MUST NOT be performed even in this alternate scenario.
770 5.9. RFC6773 - DCCP-UDP Encapsulation
772 [RFC6773] document specifies an alternative encapsulation of the
773 Datagram Congestion Control Protocol (DCCP), referred to as DCCP-UDP.
774 This encapsulation allows DCCP to be carried through the current
775 generation of Network Address Translation (NAT) middle boxes without
776 modification of those middle boxes.
778 +------------+-------------------------------+-------+--------------+
779 | Name | Notes | Level | Category |
780 +------------+-------------------------------+-------+--------------+
781 | dccp-port | Multiplexing MUST NOT be | M | NOT |
782 | | performed due to potential | | RECOMMENDED |
783 | | conflict between the port | | |
784 | | used for DCCP | | |
785 | | en/decapsulation and the RTP. | | |
786 | | | | |
787 +------------+-------------------------------+-------+--------------+
789 RFC6773 Attribute Analysis
791 Since RFC6773 is about tunneling DCCP in UDP, with the UDP port being
792 the port of the DCCP en-/de-capsulation service. This encapsulation
793 allows arbitrary DCCP packets to be encapsulated and the DCCP port
794 chosen MAY conflict with the port chosen for the RTP traffic.
796 For multiplexing several DCCP-in-UDP encapsulations on the same UDP
797 port, with no RTP traffic on the same port implies collapsing several
798 DCCP port spaces together. This MAY or MAY NOT work depending on the
799 nature of DCCP encapsulations and ports choses thus rendering it to
800 be very application dependent.
802 5.10. RFC5506 - Reduced-Size RTCP in RTP Profile
804 [RFC5506] discusses benefits and issues that arise when allowing
805 Real-time Transport Protocol (RTCP) packets to be transmitted with
806 reduced size.
808 +-------------+--------------------------------+-------+------------+
809 | Name | Notes | Level | Category |
810 +-------------+--------------------------------+-------+------------+
811 | rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL |
812 | | entire RTP Session | | |
813 | | | | |
814 +-------------+--------------------------------+-------+------------+
816 RFC5506 Attribute Analysis
818 5.11. RFC6787 - Media Resource Control Protocol Version 2
820 The Media Resource Control Protocol Version 2 (MRCPv2) allows client
821 hosts to control media service resources such as speech synthesizers,
822 recognizers, verifiers, and identifiers residing in servers on the
823 network. MRCPv2 is not a "stand-alone" protocol -- it relies on
824 other protocols, such as the Session Initiation Protocol (SIP), to
825 coordinate MRCPv2 clients and servers and manage sessions between
826 them, and the Session Description Protocol (SDP) to describe,
827 discover, and exchange capabilities. It also depends on SIP and SDP
828 to establish the media sessions and associated parameters between the
829 media source or sink and the media server. Once this is done, the
830 MRCPv2 exchange operates over the control session established above,
831 allowing the client to control the media processing resources on the
832 speech resource server. [RFC6787] defines attributes for this
833 purpose.
835 +-----------+---------------+-------+----------+
836 | Name | Notes | Level | Category |
837 +-----------+---------------+-------+----------+
838 | resource | Not Impacted | M | NORMAL |
839 | | | | |
840 | channel | Not Impacted | M | NORMAL |
841 | | | | |
842 | cmid | Not Impacted | M | NORMAL |
843 | | | | |
844 +-----------+---------------+-------+----------+
846 RFC6787 Attribute Analysis
848 5.12. RFC5245 - Interactive Connectivity Establishment (ICE)
850 [RFC5245] describes a protocol for Network Address Translator(NAT)
851 traversal for UDP-based multimedia sessions established with the
852 offer/answer model. This protocol is called Interactive Connectivity
853 Establishment (ICE). ICE makes use of the Session Traversal
854 Utilities for NAT (STUN) protocol and its extension,Traversal Using
855 Relay NAT (TURN). ICE can be used by any protocol utilizing the
856 offer/answer model, such as the Session Initiation Protocol (SIP).
858 +--------------------+-------------------------+-------+------------+
859 | Name | Notes | Level | Category |
860 +--------------------+-------------------------+-------+------------+
861 | ice-lite | Not Impacted | S | NORMAL |
862 | | | | |
863 | ice-options | Not Impacted | S | NORMAL |
864 | | | | |
865 | ice-mismatch | Not Impacted | S | NORMAL |
866 | | | | |
867 | ice-pwd | ice-pwd MUST be the one | B | TRANSPORT |
868 | | that corresponds to the | | |
869 | | m=line chosen for | | |
870 | | setting up the | | |
871 | | underlying transport | | |
872 | | flow | | |
873 | | | | |
874 | ice-ufrag | ice-ufrag MUST be the | B | TRANSPORT |
875 | | one that corresponds to | | |
876 | | the m=line chosen for | | |
877 | | setting up the | | |
878 | | underlying transport | | |
879 | | flow | | |
880 | | | | |
881 | candidate | ice candidate MUST be | M | TRANSPORT |
882 | | the one that | | |
883 | | corresponds to the | | |
884 | | m=line chosen for | | |
885 | | setting up the | | |
886 | | underlying transport | | |
887 | | flow | | |
888 | | | | |
889 | remote-candidates | ice remote candidate | M | TRANSPORT |
890 | | MUST be the one that | | |
891 | | corresponds to the | | |
892 | | m=line chosen for | | |
893 | | setting up the | | |
894 | | underlying transport | | |
895 | | flow | | |
896 | | | | |
897 +--------------------+-------------------------+-------+------------+
899 RFC5245 Attribute Analysis
901 5.13. RFC5285 - RTP Header Extensions
903 [RFC5285] provides a general mechanism to use the header extension
904 feature of RTP (the Real-Time Transport Protocol). It provides the
905 option to use a small number of small extensions in each RTP packet,
906 where the universe of possible extensions is large and registration
907 is de-centralized. The actual extensions in use in a session are
908 signaled in the setup information for that session.
910 +---------+--------------------------------------+-------+----------+
911 | Name | Notes | Level | Category |
912 +---------+--------------------------------------+-------+----------+
913 | extmap | Specific RTP extension document MUST | B | SPECIAL |
914 | | be referred | | |
915 | | | | |
916 +---------+--------------------------------------+-------+----------+
918 RFC5285 Attribute Analysis
920 5.14. RFC3605 - RTCP attribute in SDP
922 Originally, SDP assumed that RTP and RTCP were carried on consecutive
923 ports. However, this is not always true when NATs are involved.
924 [RFC3605] specifies an early mechanism to indicate the RTCP port.
926 +-------+--------------------------------------+-------+------------+
927 | Name | Notes | Level | Category |
928 +-------+--------------------------------------+-------+------------+
929 | rtcp | Identical attribute value MUST be | M | IDENTICAL |
930 | | used since the RTCP port affects the | | |
931 | | entire RTP session. | | |
932 | | | | |
933 +-------+--------------------------------------+-------+------------+
935 RFC3605 Attribute Analysis
937 5.15. RFC5576 - Source-Specific SDP Attributes
939 [RFC5576] defines a mechanism to describe RTP media sources, which
940 are identified by their synchronization source (SSRC) identifiers, in
941 SDP, to associate attributes with these sources, and to express
942 relationships among sources. It also defines several source-level
943 attributes that can be used to describe properties of media sources.
945 +----------------+----------------------+-------+-------------------+
946 | Name | Notes | Level | Category |
947 +----------------+----------------------+-------+-------------------+
948 | ssrc | Refer to Notes below | M | NORMAL |
949 | | | | |
950 | ssrc-group | Refer to section | M | NORMAL |
951 | | Section 9 for | | |
952 | | specific analysis of | | |
953 | | the grouping | | |
954 | | semantics | | |
955 | | | | |
956 | cname | Not Impacted | SR | NORMAL |
957 | | | | |
958 | previous-ssrc | Refer to notes below | SR | NORMAL |
959 | | | | |
960 | fmtp | The attribute value | SR | IDENTICAL-PER-PT |
961 | | must be same for a | | |
962 | | given codec | | |
963 | | configuration | | |
964 | | | | |
965 +----------------+----------------------+-------+-------------------+
967 RFC5576 Attribute Analysis
969 If SSRCs are repeated across m=lines being multiplexed, they MUST all
970 represent the same underlying RTP Source.
972 5.16. RFC7273 - RTP Clock Source Signalling
974 [RFC7273] specifies Session Description Protocol (SDP) signalling
975 that identifies timestamp reference clock sources and SDP signalling
976 that identifies the media clock sources in a multimedia session.
978 +------------+---------------+-------+----------+
979 | Name | Notes | Level | Category |
980 +------------+---------------+-------+----------+
981 | ts-refclk | Not Impacted | B | NORMAL |
982 | | | | |
983 | mediaclk | Not Impacted | B | NORMAL |
984 | | | | |
985 +------------+---------------+-------+----------+
987 RFC7273 Attribute Analysis
989 5.17. RFC6236 - Image Attributes in SDP
991 [RFC6236] proposes a new generic session setup attribute to make it
992 possible to negotiate different image attributes such as image size.
993 A possible use case is to make it possible for a low-end hand-held
994 terminal to display video without the need to rescale the
995 image,something that may consume large amounts of memory and
996 processing power. The document also helps to maintain an optimal
997 bitrate for video as only the image size that is desired by the
998 receiver is transmitted.
1000 +------------+--------------------------+-------+-------------------+
1001 | Name | Notes | Level | Category |
1002 +------------+--------------------------+-------+-------------------+
1003 | imageattr | The attribute value must | M | IDENTICAL-PER-PT |
1004 | | be same for a given | | |
1005 | | codec configuration | | |
1006 | | | | |
1007 +------------+--------------------------+-------+-------------------+
1009 RFC6236 Attribute Analysis
1011 5.18. RFC7197 - Duplication Delay Attribute in SDP
1013 [RFC7197] defines an attribute to indicate the presence of temporally
1014 redundant media streams and the duplication delay in the Session
1015 Description Protocol.
1017 +--------------------+---------------+-------+----------+
1018 | Name | Notes | Level | Category |
1019 +--------------------+---------------+-------+----------+
1020 | duplication-delay | Not Impacted | B | NORMAL |
1021 | | | | |
1022 +--------------------+---------------+-------+----------+
1024 RFC7197 Attribute Analysis
1026 5.19. RFC7226 - RTCP XR Blocks for MOS Metric Reporting
1028 [RFC7226] defines an RTP Control Protocol (RTCP) Extended Report (XR)
1029 Block including two new segment types and associated Session
1030 Description Protocol (SDP) parameters that allow the reporting of
1031 mean opinion score (MOS) Metrics for use in a range of RTP
1032 applications.
1034 +-------------+---------------+-------+----------+
1035 | Name | Notes | Level | Category |
1036 +-------------+---------------+-------+----------+
1037 | calgextmap | Not Impacted | B | NORMAL |
1038 | | | | |
1039 +-------------+---------------+-------+----------+
1041 RFC7226 Attribute Analysis
1043 5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions
1045 [RFC6285] describes a method using the existing RTP and RTP Control
1046 Protocol (RTCP) machinery that reduces the acquisition delay. In
1047 this method, an auxiliary unicast RTP session carrying the Reference
1048 Information to the receiver precedes or accompanies the multicast
1049 stream. This unicast RTP flow can be transmitted at a faster than
1050 natural bitrate to further accelerate the acquisition. The
1051 motivating use case for this capability is multicast applications
1052 that carry real-time compressed audio and video.
1054 +---------------+-------------------+-------+------------------+
1055 | Name | Notes | Level | Category |
1056 +---------------+-------------------+-------+------------------+
1057 | rams-updates | Not recommended | M | NOT RECOMMENDED |
1058 | | | | |
1059 +---------------+-------------------+-------+------------------+
1061 RFC6285 Attribute Analysis
1063 5.21. RFC6230 - Media Control Channel Framework
1065 [RFC6230] describes a framework and protocol for application
1066 deployment where the application programming logic and media
1067 processing are distributed. This implies that application
1068 programming logic can seamlessly gain access to appropriate resources
1069 that are not co-located on the same physical network entity. The
1070 framework uses the Session Initiation Protocol (SIP) to establish an
1071 application-level control mechanism between application servers and
1072 associated external servers such as media servers.
1074 +---------+-----------------+-------+----------+
1075 | Name | Notes | Level | Category |
1076 +---------+-----------------+-------+----------+
1077 | cfw-id | Not Applicable | M | NORMAL |
1078 | | | | |
1079 +---------+-----------------+-------+----------+
1081 RFC6230 Attribute Analysis
1083 5.22. RFC6364 - SDP Elements for FEC Framework
1085 [RFC6364] specifies the use of the Session Description Protocol (SDP)
1086 to describe the parameters required to signal the Forward Error
1087 Correction (FEC) Framework Configuration Information between the
1088 sender(s) and receiver(s). This document also provides examples that
1089 show the semantics for grouping multiple source and repair flows
1090 together for the applications that simultaneously use multiple
1091 instances of the FEC Framework.
1093 +------------------+-----------------------------+-------+----------+
1094 | Name | Notes | Level | Category |
1095 +------------------+-----------------------------+-------+----------+
1096 | fec-source-flow | Specific FEC scheme | M | SPECIAL |
1097 | | document needs to be | | |
1098 | | referred | | |
1099 | | | | |
1100 | fec-repair-flow | Specific FEC scheme | M | SPECIAL |
1101 | | document needs to be | | |
1102 | | referred | | |
1103 | | | | |
1104 | repair-window | Specific FEC scheme | M | SPECIAL |
1105 | | document needs to be | | |
1106 | | referred | | |
1107 | | | | |
1108 +------------------+-----------------------------+-------+----------+
1110 RFC6364 Attribute Analysis
1112 5.23. RFC4796 - Content Attribute
1114 [RFC4796] defines a new Session Description Protocol (SDP) media-
1115 level attribute, 'content'. The 'content' attribute defines the
1116 content of the media stream to a more detailed level than the media
1117 description line. The sender of an SDP session description can
1118 attach the 'content' attribute to one or more media streams. The
1119 receiving application can then treat each media stream differently
1120 (e.g., show it on a big or small screen) based on its content.
1122 +----------+---------------+-------+----------+
1123 | Name | Notes | Level | Category |
1124 +----------+---------------+-------+----------+
1125 | content | Not Impacted | M | NORMAL |
1126 | | | | |
1127 +----------+---------------+-------+----------+
1129 RFC4796 Attribute Analysis
1131 5.24. RFC3407 - SDP Simple Capability Declaration
1133 [RFC3407] defines a set of Session Description Protocol (SDP)
1134 attributes that enables SDP to provide a minimal and backwards
1135 compatible capability declaration mechanism.
1137 +----------+------------------------+-------+----------+
1138 | Name | Notes | Level | Category |
1139 +----------+------------------------+-------+----------+
1140 | sqn | Not Impacted | B | NORMAL |
1141 | | | | |
1142 | cdsc | Not Impacted. | B | NORMAL |
1143 | | | | |
1144 | cpar | Refer to Section 14 | B | INHERIT |
1145 | | | | |
1146 | cparmin | Refer to notes below | B | SPECIAL |
1147 | | | | |
1148 | cparmax | Refer to notes below | B | SPECIAL |
1149 | | | | |
1150 +----------+------------------------+-------+----------+
1152 RFC3407 Attribute Analysis
1154 Since the attributes (a=cparmin and a=cparmax) define minimum and
1155 maximum numerical values associated with the attributes described in
1156 a=cpar, it is recommended to consult the document defining the
1157 attribute.
1159 5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions
1161 [RFC6284] presents a port mapping solution that allows RTP receivers
1162 to choose their own ports for an auxiliary unicast session in RTP
1163 applications using both unicast and multicast services. The solution
1164 provides protection against denial-of-service or packet amplification
1165 attacks that could be used to cause one or more RTP packets to be
1166 sent to a victim client.
1168 +------------------+-------------------------+-------+--------------+
1169 | Name | Notes | Level | Category |
1170 +------------------+-------------------------+-------+--------------+
1171 | portmapping-req | Not recommended, if | M | NOT |
1172 | | port mapping is | | RECOMMENDED |
1173 | | required by the | | |
1174 | | application | | |
1175 | | | | |
1176 +------------------+-------------------------+-------+--------------+
1178 RFC6284 Attribute Analysis
1180 5.26. RFC6714 - MSRP-CEMA
1182 [RFC6714] defines a Message Session Relay Protocol (MSRP) extension,
1183 Connection Establishment for Media Anchoring (CEMA). Support of this
1184 extension is OPTIONAL. The extension allows middle boxes to anchor
1185 the MSRP connection, without the need for middle boxes to modify the
1186 MSRP messages; thus, it also enables secure end-to-end MSRP
1187 communication in networks where such middle boxes are deployed. This
1188 document also defines a Session Description Protocol (SDP) attribute,
1189 'msrp-cema', that MSRP endpoints use to indicate support of the CEMA
1190 extension.
1192 +------------+---------------+-------+----------+
1193 | Name | Notes | Level | Category |
1194 +------------+---------------+-------+----------+
1195 | msrp-cema | Not Impacted | M | NORMAL |
1196 | | | | |
1197 +------------+---------------+-------+----------+
1199 RFC6714 Attribute Analysis
1201 5.27. RFC4583 - SDP Format for BFCP Streams
1203 [RFC4583] document specifies how to describe Binary Floor Control
1204 Protocol (BFCP) streams in Session Description Protocol (SDP)
1205 descriptions. User agents using the offer/answer model to establish
1206 BFCP streams use this format in their offers and answers.
1208 +------------+---------------------------------+-------+------------+
1209 | Name | Notes | Level | Category |
1210 +------------+---------------------------------+-------+------------+
1211 | floorctrl | Must be repeated across all the | M | IDENTICAL |
1212 | | multiplexed m=lines | | |
1213 | | | | |
1214 | confid | Not Impacted | M | NORMAL |
1215 | | | | |
1216 | userid | Not Impacted | M | NORMAL |
1217 | | | | |
1218 | floorid | The floorid MUST be globally | M | NORMAL |
1219 | | unique | | |
1220 | | | | |
1221 +------------+---------------------------------+-------+------------+
1223 RFC4583 Attribute Analysis
1225 5.28. RFC5547 - SDP Offer/Answer for File Transfer
1227 [RFC5547] provides a mechanism to negotiate the transfer of one or
1228 more files between two endpoints by using the Session Description
1229 Protocol (SDP) offer/answer model specified in [RFC3264].
1231 +----------------------+---------------+-------+----------+
1232 | Name | Notes | Level | Category |
1233 +----------------------+---------------+-------+----------+
1234 | file-selector | Not Impacted | M | NORMAL |
1235 | | | | |
1236 | file-transfer-id | Not Impacted | M | NORMAL |
1237 | | | | |
1238 | file-disposition | Not Impacted | M | NORMAL |
1239 | | | | |
1240 | file-date | Not Impacted | M | NORMAL |
1241 | | | | |
1242 | file-iconfile-range | Not Impacted | M | NORMAL |
1243 | | | | |
1244 +----------------------+---------------+-------+----------+
1246 RFC5547 Attribute Analysis
1248 5.29. RFC6849 - SDP and RTP Media Loopback Extension
1250 [RFC6849] adds new SDP media types and attributes, which enable
1251 establishment of media sessions where the media is looped back to the
1252 transmitter. Such media sessions will serve as monitoring and
1253 troubleshooting tools by providing the means for measurement of more
1254 advanced VoIP, Real-time Text and Video over IP performance metrics.
1256 +------------------------------+----------------+-------+----------+
1257 | Name | Notes | Level | Category |
1258 +------------------------------+----------------+-------+----------+
1259 | loopback rtp-pkt-loopback | Not Impacted | M | NORMAL |
1260 | | | | |
1261 | loopback rtp-media-loopback | Not Impacted | M | NORMAL |
1262 | | | | |
1263 | loopback-source | Not Impacted | M | NORMAL |
1264 | | | | |
1265 | loopback-mirror | Not Impacted | M | NORMAL |
1266 | | | | |
1267 +------------------------------+----------------+-------+----------+
1269 RFC6849 Analysis
1271 5.30. RFC5760 - RTCP with Unicast Feedback
1273 [RFC5760] specifies an extension to the Real-time Transport Control
1274 Protocol (RTCP) to use unicast feedback to a multicast sender. The
1275 proposed extension is useful for single-source multicast sessions
1276 such as Source-Specific Multicast (SSM) communication where the
1277 traditional model of many-to-many group communication is either not
1278 available or not desired.
1280 +---------------+------------------------------+-------+------------+
1281 | Name | Notes | Level | Category |
1282 +---------------+------------------------------+-------+------------+
1283 | rtcp-unicast | The attribute MUST be | M | IDENTICAL |
1284 | | reported across all m=lines | | |
1285 | | multiplexed | | |
1286 | | | | |
1287 +---------------+------------------------------+-------+------------+
1289 RFC5760 Attribute Analysis
1291 5.31. RFC3611 - RTCP XR
1293 [RFC3611] defines the Extended Report (XR) packet type for the RTP
1294 Control Protocol (RTCP), and defines how the use of XR packets can be
1295 signaled by an application if it employs the Session Description
1296 Protocol (SDP).
1298 +----------+---------------+-------+----------+
1299 | Name | Notes | Level | Category |
1300 +----------+---------------+-------+----------+
1301 | rtcp-xr | Not Impacted | B | NORMAL |
1302 | | | | |
1303 +----------+---------------+-------+----------+
1305 RFC3611 Attribute Analysis
1307 5.32. RFC5939 - SDP Capability Negotiation
1309 [RFC5939] defines a general SDP Capability Negotiation framework. It
1310 also specifies how to provide attributes and transport protocols as
1311 capabilities and negotiate them using the framework. Extensions for
1312 other types of capabilities (e.g., media types and media formats) may
1313 be provided in other documents.
1315 +---------+-------------------------------+-------+----------+
1316 | Name | Notes | Level | Category |
1317 +---------+-------------------------------+-------+----------+
1318 | pcfg | Refer to Section Section 14 | M | SPECIAL |
1319 | | | | |
1320 | acfg | Refer to Section Section 14 | M | SPECIAL |
1321 | | | | |
1322 | csup | Not Impacted | B | NORMAL |
1323 | | | | |
1324 | creq | Not Impacted | B | NORMAL |
1325 | | | | |
1326 | acap | Refer to section Section 14 | B | INHERIT |
1327 | | | | |
1328 | tcap | Refer to section Section 14 | B | INHERIT |
1329 | | | | |
1330 | cap-v0 | Not Impacted | B | NORMAL |
1331 | | | | |
1332 +---------+-------------------------------+-------+----------+
1334 RFC5939 Attribute Analysis
1336 5.33. RFC6871- SDP Media Capabilities Negotiation
1338 Session Description Protocol (SDP) capability negotiation provides a
1339 general framework for indicating and negotiating capabilities in SDP.
1340 The base framework defines only capabilities for negotiating
1341 transport protocols and attributes. [RFC6871] extends the framework
1342 by defining media capabilities that can be used to negotiate media
1343 types and their associated parameters.
1345 +---------+-----------------------------+-------+-------------------+
1346 | Name | Notes | Level | Category |
1347 +---------+-----------------------------+-------+-------------------+
1348 | rmcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
1349 | | | | |
1350 | omcap | Not Impacted | B | NORMAL |
1351 | | | | |
1352 | mfcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
1353 | | | | |
1354 | mscap | Refer to Section Section 14 | B | INHERIT |
1355 | | | | |
1356 | lcfg | Refer to Section Section 14 | B | SPECIAL |
1357 | | | | |
1358 | sescap | Refer to Section Section 14 | S | NOT RECOMMENDED |
1359 | | | | |
1360 | med-v0 | Not Impacted | S | NORMAL |
1361 | | | | |
1362 +---------+-----------------------------+-------+-------------------+
1364 RFC6871 - Attribute Analysis
1366 The "sescap" attribute is NOT RECOMMENDED for use with multiplexing.
1367 The reason is that it requires the use of unique configuration
1368 numbers across the entire SDP (per [RFC6871] as opposed to within a
1369 media description only (per [RFC5939]). As described in Section 14,
1370 the use of identical configuration numbers between multiplxed
1371 (bundled) media descriptions is the default way of indicating
1372 compatible configurations in a bundle.
1374 5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP
1376 [RFC7006] extends the SDP capability negotiation framework to allow
1377 endpoints to negotiate three additional SDP capabilities. In
1378 particular, this memo provides a mechanism to negotiate bandwidth
1379 ("b=" line), connection data ("c=" line), and session or media titles
1380 ("i=" line for each session or media).
1382 +----------+-----------------------------------+-------+------------+
1383 | Name | Notes | Level | Category |
1384 +----------+-----------------------------------+-------+------------+
1385 | bcap | Inherit the category SUM as | B | INHERIT |
1386 | | applicable to b= attribute | | |
1387 | | | | |
1388 | bcap-v0 | Not Impacted | B | NORMAL |
1389 | | | | |
1390 | ccap | The connection address type MUST | B | IDENTICAL |
1391 | | be identical across all the | | |
1392 | | multiplexed m= lines. | | |
1393 | | | | |
1394 | ccap-v0 | Not Impacted. | B | NORMAL |
1395 | | | | |
1396 | icap | Not Impacted | B | NORMAL |
1397 | | | | |
1398 | icap-v0 | Not Impacted | B | NORMAL |
1399 | | | | |
1400 +----------+-----------------------------------+-------+------------+
1402 RFC7006 - Attribute Analysis
1404 5.35. RFC4567 - Key Management Extensions for SDP and RTSP
1406 [RFC4567] defines general extensions for Session Description Protocol
1407 (SDP) and Real Time Streaming Protocol (RTSP) to carry messages, as
1408 specified by a key management protocol, in order to secure the media.
1409 These extensions are presented as a framework, to be used by one or
1410 more key management protocols. As such, their use is meaningful only
1411 when complemented by an appropriate key management protocol.
1413 +-----------+----------------------------------+-------+------------+
1414 | Name | Notes | Level | Category |
1415 +-----------+----------------------------------+-------+------------+
1416 | key-mgmt | Key management protocol MUST be | B | IDENTICAL |
1417 | | identical across all the m=lines | | |
1418 | | | | |
1419 | mikey | Key management protocol MUST be | B | IDENTICAL |
1420 | | identical across all the m=lines | | |
1421 | | | | |
1422 +-----------+----------------------------------+-------+------------+
1424 RFC4567 Attribute Analysis
1426 5.36. RFC4572 - Comedia over TLS in SDP
1428 [RFC4572] specifies how to establish secure connection-oriented media
1429 transport sessions over the Transport Layer Security (TLS) protocol
1430 using the Session Description Protocol (SDP). It defines a new SDP
1431 protocol identifier, 'TCP/TLS'. It also defines the syntax and
1432 semantics for an SDP 'fingerprint' attribute that identifies the
1433 certificate that will be presented for the TLS session. This
1434 mechanism allows media transport over TLS connections to be
1435 established securely, so long as the integrity of session
1436 descriptions is assured.
1438 +--------------+-------------------------------+-------+------------+
1439 | Name | Notes | Level | Category |
1440 +--------------+-------------------------------+-------+------------+
1441 | fingerprint | Fingerprint value from the | B | TRANSPORT |
1442 | | m=line defining the | | |
1443 | | underlying transport is | | |
1444 | | chosen | | |
1445 | | | | |
1446 +--------------+-------------------------------+-------+------------+
1448 RFC4572 Attribute Analysis
1450 5.37. RFC4570 - SDP Source Filters
1452 [RFC4570] describes how to adapt the Session Description Protocol
1453 (SDP) to express one or more source addresses as a source filter for
1454 one or more destination "connection" addresses. It defines the
1455 syntax and semantics for an SDP "source-filter" attribute that may
1456 reference either IPv4 or IPv6 address(es) as either an inclusive or
1457 exclusive source list for either multicast or unicast destinations.
1458 In particular, an inclusive source-filter can be used to specify a
1459 Source-Specific Multicast (SSM) session.
1461 +----------------+-----------------------------+-------+------------+
1462 | Name | Notes | Level | Category |
1463 +----------------+-----------------------------+-------+------------+
1464 | source-filter | The attribute MUST be | B | IDENTICAL |
1465 | | repeated across all m=lines | | |
1466 | | multiplexed | | |
1467 | | | | |
1468 +----------------+-----------------------------+-------+------------+
1470 RFC4570 Attribute Analysis
1472 5.38. RFC6128 - RTCP Port for Multicast Sessions
1474 The Session Description Protocol (SDP) has an attribute that allows
1475 RTP applications to specify an address and a port associated with the
1476 RTP Control Protocol (RTCP) traffic. In RTP-based source-specific
1477 multicast (SSM) sessions, the same attribute is used to designate the
1478 address and the RTCP port of the Feedback Target in the SDP
1479 description. However, the RTCP port associated with the SSM session
1480 itself cannot be specified by the same attribute to avoid ambiguity,
1481 and thus, is required to be derived from the "m=" line of the media
1482 description. Deriving the RTCP port from the "m=" line imposes an
1483 unnecessary restriction. [RFC6128] removes this restriction by
1484 introducing a new SDP attribute.
1486 +-----------------+----------------------------+-------+------------+
1487 | Name | Notes | Level | Category |
1488 +-----------------+----------------------------+-------+------------+
1489 | multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL |
1490 | | be identical across all | | |
1491 | | the m=lines | | |
1492 | | | | |
1493 +-----------------+----------------------------+-------+------------+
1495 RFC6128 Attribute Analysis
1497 5.39. RFC6189 - ZRTP
1499 [RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman
1500 exchange to agree on a session key and parameters for establishing
1501 unicast Secure Real-time Transport Protocol (SRTP) sessions for Voice
1502 over IP (VoIP) applications.
1504 +------------+-------------------------------+-------+--------------+
1505 | Name | Notes | Level | Category |
1506 +------------+-------------------------------+-------+--------------+
1507 | zrtp-hash | Complicates if all the | M | NOT |
1508 | | m=lines are not authenticated | | RECOMMENDED |
1509 | | as given in the example below | | |
1510 | | | | |
1511 +------------+-------------------------------+-------+--------------+
1513 RFC6189 Attribute Analysis
1515 Example: Multiplexing media descriptions having attribute zrtp-hash
1516 defined with the media descriptions lacking it, would either
1517 complicate the handling of multiplexed stream or fail multiplexing.
1519 v=0
1520 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
1521 s=
1522 c=IN IP4 client.biloxi.example.com
1523 t=0 0
1524 m=audio 3456 RTP/AVP 97
1525 a=rtpmap:97 iLBC/8000
1526
1527 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
1528 df881ae642c371ba46df
1529
1530 m=video 34567 RTP/AVP 31
1531 a=rtpmap:31 H261/90000
1533 5.40. RFC4145 - Connection-Oriented Media
1535 [RFC4145] describes how to express media transport over TCP using the
1536 Session Description Protocol (SDP). It defines the SDP 'TCP'
1537 protocol identifier, the SDP 'setup' attribute, which describes the
1538 connection setup procedure, and the SDP 'connection' attribute, which
1539 handles connection reestablishment.
1541 +-------------+--------------------------------+-------+------------+
1542 | Name | Notes | Level | Category |
1543 +-------------+--------------------------------+-------+------------+
1544 | setup | MUST be identical across all | B | IDENTICAL |
1545 | | m=lines | | |
1546 | | | | |
1547 | connection | MUST be identical across all | B | IDENTICAL |
1548 | | m=lines | | |
1549 | | | | |
1550 +-------------+--------------------------------+-------+------------+
1552 RFC4145 Attribute Analysis
1554 5.41. RFC6947 - The SDP ALTC Attribute
1556 [RFC6947] proposes a mechanism that allows the same SDP offer to
1557 carry multiple IP addresses of different address families (e.g., IPv4
1558 and IPv6). The proposed attribute, the "altc" attribute, solves the
1559 backward-compatibility problem that plagued Alternative Network
1560 Address Types (ANAT) due to their syntax.
1562 +-------+--------------------------------------+-------+------------+
1563 | Name | Notes | Level | Category |
1564 +-------+--------------------------------------+-------+------------+
1565 | altc | The IP Address and port must be the | M | TRANSPORT |
1566 | | one that corresponds to the m=line | | |
1567 | | chosen for setting up the underlying | | |
1568 | | transport flow. | | |
1569 | | | | |
1570 +-------+--------------------------------------+-------+------------+
1572 RFC6947 Attribute Analysis
1574 5.42. RFC7195 - SDP Extension for Circuit Switched Bearers in PSTN
1576 [RFC7195] describes use cases, requirements, and protocol extensions
1577 for using the Session Description Protocol (SDP) offer/answer model
1578 for establishing audio and video media streams over circuit-switched
1579 bearers in the Public Switched Telephone Network (PSTN).
1581 +--------------------------+----------------+-------+----------+
1582 | Name | Notes | Level | Category |
1583 +--------------------------+----------------+-------+----------+
1584 | cs-correlation:callerid | Not Impacted. | M | NORMAL |
1585 | | | | |
1586 | cs-correlation:uuie | Not Impacted. | M | NORMAL |
1587 | | | | |
1588 | cs-correlation:dtmf | Not Impacted. | M | NORMAL |
1589 | | | | |
1590 | cs-correlation:external | Not Impacted. | M | NORMAL |
1591 | | | | |
1592 +--------------------------+----------------+-------+----------+
1594 RFC7195 Attribute Analysis
1596 5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP)
1598 [RFC7272] defines a new RTP Control Protocol (RTCP) Packet Type and
1599 an RTCP Extended Report (XR) Block Type to be used for achieving
1600 Inter-Destination Media Synchronization (IDMS).
1602 +------------+----------------+-------+----------+
1603 | Name | Notes | Level | Category |
1604 +------------+----------------+-------+----------+
1605 | rtcp-idms | Not Impacted. | M | NORMAL |
1606 | | | | |
1607 +------------+----------------+-------+----------+
1609 RFC7272 Attribute Analysis
1611 5.44. RFC5159 - OMA BCAST SDP Attributes
1613 [RFC5159] provides descriptions of Session Description Protocol (SDP)
1614 attributes used by the Open Mobile Alliance's Broadcast Service and
1615 Content Protection specification.
1617 +---------------------+---------------+-------+----------+
1618 | Name | Notes | Level | Category |
1619 +---------------------+---------------+-------+----------+
1620 | bcastversion | Not Impacted | S | NORMAL |
1621 | | | | |
1622 | stkmstream | Not Impacted | B | NORMAL |
1623 | | | | |
1624 | SRTPAuthentication | Not Impacted | M | NORMAL |
1625 | | | | |
1626 | SRTPROCTxRate | Not Impacted | M | NORMAL |
1627 | | | | |
1628 +---------------------+---------------+-------+----------+
1630 RFC5159 Attribute Analysis
1632 5.45. RFC6193 - Media Description for IKE in SDP
1634 [RFC6193] specifies how to establish a media session that represents
1635 a virtual private network using the Session Initiation Protocol for
1636 the purpose of on-demand media/application sharing between peers. It
1637 extends the protocol identifier of the Session Description Protocol
1638 (SDP) so that it can negotiate use of the Internet Key Exchange
1639 Protocol (IKE) for media sessions in the SDP offer/answer model.
1641 +-------------------+--------------------------+-------+------------+
1642 | Name | Notes | Level | Category |
1643 +-------------------+--------------------------+-------+------------+
1644 | ike-setup | Attribute MUST be | B | IDENTICAL |
1645 | | identical across all the | | |
1646 | | m=lines | | |
1647 | | | | |
1648 | psk-fingerprint | Attribute MUST be | B | IDENTICAL |
1649 | | identical across all the | | |
1650 | | m=lines | | |
1651 | | | | |
1652 | ike-esp | Attribute MUST be | B | IDENTICAL |
1653 | | identical across all the | | |
1654 | | m=lines | | |
1655 | | | | |
1656 | ike-esp-udpencap | Attribute MUST be | B | IDENTICAL |
1657 | | identical across all the | | |
1658 | | m=lines | | |
1659 | | | | |
1660 +-------------------+--------------------------+-------+------------+
1662 RFC6193 Attribute Analysis
1664 With the above SDP constraints, a session multiplexed with multiple
1665 m=lines will use only one IPSec association for all of the m= lines.
1667 5.46. RFC2326 - Real Time Streaming Protocol
1669 The Real Time Streaming Protocol, or RTSP, is an application-level
1670 protocol for control over the delivery of data with real-time
1671 properties. RTSP provides an extensible framework to enable
1672 controlled, on-demand delivery of real-time data, such as audio and
1673 video.
1675 +----------+---------------------------------+-------+--------------+
1676 | Name | Notes | Level | Category |
1677 +----------+---------------------------------+-------+--------------+
1678 | etag | RTSP is not supported for RTP | B | NOT |
1679 | | Stream multiplexing | | RECOMMENDED |
1680 | | | | |
1681 | range | RTSP is not supported for RTP | B | NOT |
1682 | | Stream multiplexing | | RECOMMENDED |
1683 | | | | |
1684 | control | RTSP is not supported for RTP | B | NOT |
1685 | | Stream multiplexing | | RECOMMENDED |
1686 | | | | |
1687 | mtag | RTSP is not supported for RTP | B | NOT |
1688 | | Stream multiplexing | | RECOMMENDED |
1689 | | | | |
1690 +----------+---------------------------------+-------+--------------+
1692 RFC2326 Attribute Analysis
1694 5.47. RFC6064 - SDP and RTSP Extensions for 3GPP
1696 The Packet-switched Streaming Service (PSS) and the Multimedia
1697 Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session
1698 Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
1699 with some extensions. [RFC6064] provides information about these
1700 extensions and registers the RTSP and SDP extensions with IANA.
1702 +-------------------------------+------------+-------+--------------+
1703 | Name | Notes | Level | Category |
1704 +-------------------------------+------------+-------+--------------+
1705 | X-predecbufsize | Refer to | M | NOT |
1706 | | notes | | RECOMMENDED |
1707 | | below | | |
1708 | | | | |
1709 | X-initpredecbufperiod | Refer to | M | NOT |
1710 | | notes | | RECOMMENDED |
1711 | | below | | |
1712 | | | | |
1713 | X-initpostdecbufperiod | Refer to | M | NOT |
1714 | | notes | | RECOMMENDED |
1715 | | below | | |
1716 | | | | |
1717 | X-decbyterate | Refer to | M | NOT |
1718 | | notes | | RECOMMENDED |
1719 | | below | | |
1720 | | | | |
1721 | 3gpp-videopostdecbufsize | Refer to | M | NOT |
1722 | | notes | | RECOMMENDED |
1723 | | below | | |
1724 | | | | |
1725 | framesize | Refer to | M | NOT |
1726 | | notes | | RECOMMENDED |
1727 | | below | | |
1728 | | | | |
1729 | 3GPP-Integrity-Key | Refer to | S | NOT |
1730 | | notes | | RECOMMENDED |
1731 | | below | | |
1732 | | | | |
1733 | 3GPP-SDP-Auth | Refer to | S | NOT |
1734 | | notes | | RECOMMENDED |
1735 | | below | | |
1736 | | | | |
1737 | 3GPP-SRTP-Config | Refer to | M | NOT |
1738 | | notes | | RECOMMENDED |
1739 | | below | | |
1740 | | | | |
1741 | alt | Refer to | M | NOT |
1742 | | notes | | RECOMMENDED |
1743 | | below | | |
1744 | | | | |
1745 | alt-default-id | Refer to | M | NOT |
1746 | | notes | | RECOMMENDED |
1747 | | below | | |
1748 | | | | |
1749 | alt-group | Refer to | M | NOT |
1750 | | notes | | RECOMMENDED |
1751 | | below | | |
1752 | | | | |
1753 | 3GPP-Adaptation-Support | Refer to | M | NOT |
1754 | | notes | | RECOMMENDED |
1755 | | below | | |
1756 | | | | |
1757 | 3GPP-Asset-Informatio | Refer to | B | NOT |
1758 | | notes | | RECOMMENDED |
1759 | | below | | |
1760 | | | | |
1761 | mbms-mode | Refer to | B | NOT |
1762 | | notes | | RECOMMENDED |
1763 | | below | | |
1764 | | | | |
1765 | mbms-flowid | Refer to | M | NOT |
1766 | | notes | | RECOMMENDED |
1767 | | below | | |
1768 | | | | |
1769 | mbms-repair | Refer to | B | NOT |
1770 | | notes | | RECOMMENDED |
1771 | | below | | |
1772 | | | | |
1773 | 3GPP-QoE-Metrics:Corruption | Refer to | M | NOT |
1774 | duration | notes | | RECOMMENDED |
1775 | | below | | |
1776 | | | | |
1777 | 3GPP-QoE-Metrics:Rebuffering | Refer to | M | NOT |
1778 | duration | notes | | RECOMMENDED |
1779 | | below | | |
1780 | | | | |
1781 | 3GPP-QoE-Metrics:Initial | Refer to | M | NOT |
1782 | buffering duration | notes | | RECOMMENDED |
1783 | | below | | |
1784 | | | | |
1785 | 3GPP-QoE-Metrics:Successive | Refer to | M | NOT |
1786 | loss of RTP packets | notes | | RECOMMENDED |
1787 | | below | | |
1788 | | | | |
1789 | 3GPP-QoE-Metrics:Frame rate | Refer to | M | NOT |
1790 | deviation | notes | | RECOMMENDED |
1791 | | below | | |
1792 | | | | |
1793 | 3GPP-QoE-Metrics:Jitter | Refer to | M | NOT |
1794 | duration | notes | | RECOMMENDED |
1795 | | below | | |
1796 | | | | |
1797 | 3GPP-QoE-Metrics:Content | Refer to | B | NOT |
1798 | Switch Time | notes | | RECOMMENDED |
1799 | | below | | |
1800 | | | | |
1801 | 3GPP-QoE-Metrics:Average | Refer to | M | NOT |
1802 | Codec Bitrat | notes | | RECOMMENDED |
1803 | | below | | |
1804 | | | | |
1805 | 3GPP-QoE-Metrics:Codec | Refer to | M | NOT |
1806 | Information | notes | | RECOMMENDED |
1807 | | below | | |
1808 | | | | |
1809 | 3GPP-QoE-Metrics:Buffer | Refer to | M | NOT |
1810 | Status | notes | | RECOMMENDED |
1811 | | below | | |
1812 | | | | |
1813 +-------------------------------+------------+-------+--------------+
1815 RFC6064 Attribute Analysis
1817 [RFC6064] defines SDP attributes that are applicable in the
1818 declarative usage of SDP alone. For purposes of this document, only
1819 the Offer/Answer usage of SDP is considered as mandated by
1820 [I-D.ietf-mmusic-sdp-bundle-negotiation].
1822 5.48. RFC3108 - ATM SDP
1824 RFC3108 [RFC3108] describes conventions for using the Session
1825 Description Protocol (SDP) described for controlling ATM Bearer
1826 Connections, and any associated ATM Adaptation Layer (AAL).
1828 +------------------------+--------------+-------+----------+
1829 | Name | Notes | Level | Category |
1830 +------------------------+--------------+-------+----------+
1831 | aalType | Not Impacted | B | NORMAL |
1832 | eecid | Not Impacted | B | NORMAL |
1833 | aalType | Not Impacted | B | NORMAL |
1834 | capability | Not Impacted | B | NORMAL |
1835 | qosClass | Not Impacted | B | NORMAL |
1836 | bcob | Not Impacted | B | NORMAL |
1837 | stc | Not Impacted | B | NORMAL |
1838 | upcc | Not Impacted | B | NORMAL |
1839 | atmQOSparms | Not Impacted | B | NORMAL |
1840 | atmTrfcDesc | Not Impacted | B | NORMAL |
1841 | abrParms | Not Impacted | B | NORMAL |
1842 | abrSetup | Not Impacted | B | NORMAL |
1843 | bearerType | Not Impacted | B | NORMAL |
1844 | lij | Not Impacted | B | NORMAL |
1845 | anycast | Not Impacted | B | NORMAL |
1846 | cache | Not Impacted | B | NORMAL |
1847 | bearerSigIE | Not Impacted | B | NORMAL |
1848 | aalApp | Not Impacted | B | NORMAL |
1849 | cbrRate | Not Impacted | B | NORMAL |
1850 | sbc | Not Impacted | B | NORMAL |
1851 | clkrec | Not Impacted | B | NORMAL |
1852 | fec | Not Impacted | B | NORMAL |
1853 | prtfl | Not Impacted | B | NORMAL |
1854 | structure | Not Impacted | B | NORMAL |
1855 | cpsSDUsize | Not Impacted | B | NORMAL |
1856 | aal2CPS | Not Impacted | B | NORMAL |
1857 | aal2CPSSDUrate | Not Impacted | B | NORMAL |
1858 | aal2sscs3661unassured | Not Impacted | B | NORMAL |
1859 | aal2sscs3661assured | Not Impacted | B | NORMAL |
1860 | aal2sscs3662 | Not Impacted | B | NORMAL |
1861 | aal5sscop | Not Impacted | B | NORMAL |
1862 | atmmap | Not Impacted | B | NORMAL |
1863 | silenceSupp | Not Impacted | B | NORMAL |
1864 | ecan | Not Impacted | B | NORMAL |
1865 | gc | Not Impacted | B | NORMAL |
1866 | profileDesc | Not Impacted | B | NORMAL |
1867 | vsel | Not Impacted | B | NORMAL |
1868 | dsel | Not Impacted | B | NORMAL |
1869 | fsel | Not Impacted | B | NORMAL |
1870 | onewaySel | Not Impacted | B | NORMAL |
1871 | codecconfig | Not Impacted | B | NORMAL |
1872 | isup_usi | Not Impacted | B | NORMAL |
1873 | isup_usi | Not Impacted | B | NORMAL |
1874 | chain | Not Impacted | B | NORMAL |
1875 | | | | |
1876 +------------------------+--------------+-------+----------+
1878 RFC3108 Attribute Analysis
1880 RFC3108 describes conventions for using the Session Description
1881 Protocol (SDP) for characterizing ATM bearer connections using an
1882 AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5,
1883 bearer connections can be used to transport single media streams. In
1884 addition, for AAL1 and AAL2, multiple media streams may be
1885 multiplexed into a bearer connection. For all adaptation types
1886 (AAL1, AAL2 and AAL5), bearer connections may be bundled into a
1887 single media group. In all cases addressed by RFC3108, a real-time
1888 media stream (voice, video, voiceband data, pseudo-wire and others)
1889 or a multiplex of media streams is mapped directly into an ATM
1890 connection. RFC3108 does not address cases where ATM serves as a
1891 low-level transport pipe for IP packets which in turn may carry one
1892 or more real-time (e.g. VoIP) media sessions with a life-cycle
1893 different from that of the underlying ATM transport.
1895 5.49. 3GPP TS 26.114
1897 [R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and
1898 interaction
1900 +----------------------+-------------------------+-------+----------+
1901 | Name | Notes | Level | Category |
1902 +----------------------+-------------------------+-------+----------+
1903 | 3gpp_sync_info | Usage defined for the | M | NORMAL |
1904 | | IP Multimedia Subsystem | | |
1905 | | | | |
1906 | 3gpp_MaxRecvSDUSize | Usage defined for the | M | NORMAL |
1907 | | IP Multimedia Subsystem | | |
1908 | | | | |
1909 +----------------------+-------------------------+-------+----------+
1911 3GPP TS 26.114 Attribute Analysis
1913 5.50. 3GPP TS 183.063
1915 [R3GPPTS183.063] Telecommunications and Internet converged Services
1916 and Protocols for Advanced Networking (TISPAN);
1918 +---------------------+---------------+----------------+----------+
1919 | Name | Notes | Level | Category |
1920 +---------------------+---------------+----------------+----------+
1921 | PSCid | Not Impacted | Not-ApplIcable | NORMAL |
1922 | | | | |
1923 | bc_service | Not Impacted | Not-AppIlcable | NORMAL |
1924 | | | | |
1925 | bc_program | Not Impacted | Not-AppIlcable | NORMAL |
1926 | | | | |
1927 | bc_service_package | Not Impacted | Not-Appilcable | NORMAL |
1928 | | | | |
1929 +---------------------+---------------+----------------+----------+
1931 3GPP TS 183.063 Attribute Analysis
1933 5.51. 3GPP TS 24.182
1935 [R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting
1936 tones
1938 +-------------+----------------------------------+-------+----------+
1939 | Name | Notes | Level | Category |
1940 +-------------+----------------------------------+-------+----------+
1941 | g.3gpp.cat | Usage defined for the IP | M | NORMAL |
1942 | | Multimedia Subsystem | | |
1943 | | | | |
1944 +-------------+----------------------------------+-------+----------+
1946 3GPP TS 24.182 Attribute Analysis
1948 5.52. 3GPP TS 24.183
1950 [R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing
1951 Signal
1952 +-------------+----------------------------------+-------+----------+
1953 | Name | Notes | Level | Category |
1954 +-------------+----------------------------------+-------+----------+
1955 | g.3gpp.crs | Usage defined for the IP | M | NORMAL |
1956 | | Multimedia Subsystem | | |
1957 | | | | |
1958 +-------------+----------------------------------+-------+----------+
1960 3GPP TS 24.183 Attribute Analysis
1962 5.53. 3GPP TS 24.229
1964 [R3GPPTS24.229] specifies IP multimedia call control protocol based
1965 on Session Initial protocol and Session Description Protocol.
1967 +------------------+---------------------------+-------+------------+
1968 | Name | Notes | Level | Category |
1969 +------------------+---------------------------+-------+------------+
1970 | secondary-realm | Per media-level attribute | M | TRANSPORT |
1971 | | MUST be used per | | |
1972 | | underlying transport | | |
1973 | | | | |
1974 | visited-realm | Per media-level attribute | M | TRANSPORT |
1975 | | MUST be used per | | |
1976 | | underlying transport | | |
1977 | | | | |
1978 | omr-m-cksum | Not Impacted | M | NORMAL |
1979 | | | | |
1980 | omr-s-cksum | Not Impacted | M | NORMAL |
1981 | | | | |
1982 | omr-m-att | Not Impacted | M | NORMAL |
1983 | | | | |
1984 | omr-s-bw | Not Impacted | M | NORMAL |
1985 | | | | |
1986 | omr-s-bw | Not Impacted | M | NORMAL |
1987 | | | | |
1988 | omr-m-att | Not Impacted | M | NORMAL |
1989 | | | | |
1990 | omr-codecs | Not Impacted | M | NORMAL |
1991 | | | | |
1992 +------------------+---------------------------+-------+------------+
1994 3GPP TS 24.229 Attribute Analysis
1996 5.54. ITU T.38
1998 [T.38] defines procedures for real-time Group 3 facsimile
1999 communications over IP networks.
2001 +------------------------+---------------+-------+----------+
2002 | Name | Notes | Level | Category |
2003 +------------------------+---------------+-------+----------+
2004 | T38FaxVersion | Not Impacted | S | NORMAL |
2005 | | | | |
2006 | T38MaxBitRate | Not Impacted | S | NORMAL |
2007 | | | | |
2008 | T38FaxFillBitRemoval | Not Impacted | S | NORMAL |
2009 | | | | |
2010 | T38FaxTranscodingMMR | Not Impacted | S | NORMAL |
2011 | | | | |
2012 | T38FaxTranscodingJBIG | Not Impacted | S | NORMAL |
2013 | | | | |
2014 | T38FaxRateManagement | Not Impacted | S | NORMAL |
2015 | | | | |
2016 | T38FaxMaxBuffer | Not Impacted | S | NORMAL |
2017 | | | | |
2018 | T38FaxMaxDatagram | Not Impacted | S | NORMAL |
2019 | | | | |
2020 | T38FaxUdpEC | Not Impacted | S | NORMAL |
2021 | | | | |
2022 | T38FaxMaxIFP | Not Impacted | S | NORMAL |
2023 | | | | |
2024 | T38FaxUdpECDepth | Not Impacted | S | NORMAL |
2025 | | | | |
2026 | T38FaxUdpFECMaxSpan | Not Impacted | S | NORMAL |
2027 | | | | |
2028 | T38ModemType | Not Impacted | S | NORMAL |
2029 | | | | |
2030 +------------------------+---------------+-------+----------+
2032 ITU T.38 Attribute Analysis
2034 The ITU T.38 attributes are clearly unaffected by multiplexing and
2035 are specific to the working of the fax protocol itself.
2037 5.55. ITU-T-REC.Q1970
2039 [ITU-T-REC.Q1970] defines BICC IP bearer control protocol.
2041 +--------+---------------+-------+----------+
2042 | Name | Notes | Level | Category |
2043 +--------+---------------+-------+----------+
2044 | ipbcp | Not Impacted | S | NORMAL |
2045 | | | | |
2046 +--------+---------------+-------+----------+
2048 ITU-T-REC.Q1970 Attribute Analysis
2050 5.56. ITU-T H.248.15
2052 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248
2053 package attribute
2055 +-----------+------------------------------------+-------+----------+
2056 | Name | Notes | Level | Category |
2057 +-----------+------------------------------------+-------+----------+
2058 | h248item | It is also only applicable for | B | SPECIAL |
2059 | | signaling the inclusion of H.248 | | |
2060 | | extension packages to a gateway | | |
2061 | | via the local and remote | | |
2062 | | descriptors. The attribute itself | | |
2063 | | is unaffected by multiplexing, but | | |
2064 | | the packaged referenced in a | | |
2065 | | specific use of the attribute may | | |
2066 | | be impacted. Further analysis of | | |
2067 | | each package is needed to | | |
2068 | | determine if there is an issue. | | |
2069 | | This is only a concern in | | |
2070 | | environments using a decomposed | | |
2071 | | server/gateway with H.248 signaled | | |
2072 | | between them. The ITU-T will need | | |
2073 | | to do further analysis of various | | |
2074 | | packages when they specify how to | | |
2075 | | signal the use of multiplexing to | | |
2076 | | a gateway. | | |
2077 | | | | |
2078 +-----------+------------------------------------+-------+----------+
2080 ITU-T H.248.15 Attribute Analysis
2082 5.57. RFC4975 - The Message Session Relay Protocol
2084 [RFC4975] the Message Session Relay Protocol, a protocol for
2085 transmitting a series of related instant messages in the context of a
2086 session. Message sessions are treated like any other media stream
2087 when set up via a rendezvous or session creation protocol such as the
2088 Session Initiation Protocol.
2090 +-----------------------+---------------+-------+----------+
2091 | Name | Notes | Level | Category |
2092 +-----------------------+---------------+-------+----------+
2093 | accept-types | Not Impacted | M | NORMAL |
2094 | | | | |
2095 | accept-wrapped-types | Not Impacted | M | NORMAL |
2096 | | | | |
2097 | max-size | Not Impacted | M | NORMAL |
2098 | | | | |
2099 | path | Not Impacted | M | NORMAL |
2100 | | | | |
2101 +-----------------------+---------------+-------+----------+
2103 RFC4975 Attribute Analysis
2105 5.58. RFC4574 - SDP Label Attribute
2107 [RFC4574] defines a new Session Description Protocol (SDP) media-
2108 level attribute: "label". The "label" attribute carries a pointer to
2109 a media stream in the context of an arbitrary network application
2110 that uses SDP. The sender of the SDP document can attach the "label"
2111 attribute to a particular media stream or streams. The application
2112 can then use the provided pointer to refer to each particular media
2113 stream in its context.
2115 +--------+---------------+-------+----------+
2116 | Name | Notes | Level | Category |
2117 +--------+---------------+-------+----------+
2118 | label | Not Impacted | M | NORMAL |
2119 | | | | |
2120 +--------+---------------+-------+----------+
2122 RFC4574 Attribute Analysis
2124 5.59. Historical Attributes
2126 This section specifies analysis for the attributes that are included
2127 for historic usage alone by the [IANA].
2129 +----------+---------------------+----------------+-----------------+
2130 | Name | Notes | Level | Category |
2131 +----------+---------------------+----------------+-----------------+
2132 | rtpred1 | Historic | Not-Applicable | NOT RECOMMENDED |
2133 | | attributes. | | |
2134 | | | | |
2135 | rtpred2 | Historic | Not-Applicable | NOT RECOMMENDED |
2136 | | attributes. | | |
2137 | | | | |
2138 +----------+---------------------+----------------+-----------------+
2140 Historical Attribute Analysis
2142 6. bwtype Attribute Analysis
2144 This section specifies handling of specific bandwidth attributes when
2145 used in multiplexing scenarios.
2147 6.1. RFC4566 - SDP: Session Description Protocol
2149 +------------+-----------------------------------+-------+----------+
2150 | Name | Notes | Level | Category |
2151 +------------+-----------------------------------+-------+----------+
2152 | bwtype:CT | Not Impacted | S | NORMAL |
2153 | | | | |
2154 | bwtype:AS | As a session attribute, it | B | NORMAL |
2155 | | specifies the session aggregate | | |
2156 | | unless media-level b=RR and/or | | |
2157 | | b=RS attributes are used. Under | | |
2158 | | this interpretation the | | |
2159 | | multiplexing scheme has no impact | | |
2160 | | and thus NORMAL category applies. | | |
2161 | | | | |
2162 | bwtype:AS | For the media level usage, the | B | SUM |
2163 | | aggregate of individual bandwidth | | |
2164 | | values is considered. | | |
2165 | | | | |
2166 +------------+-----------------------------------+-------+----------+
2168 RFC4566 bwtype Analysis
2170 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth
2172 [RFC3556] defines an extension to the Session Description Protocol
2173 (SDP) to specify two additional modifiers for the bandwidth
2174 attribute. These modifiers may be used to specify the bandwidth
2175 allowed for RTP Control Protocol (RTCP) packets in a Real-time
2176 Transport Protocol (RTP) session.
2178 +------------+-----------------------------------+-------+----------+
2179 | Name | Notes | Level | Category |
2180 +------------+-----------------------------------+-------+----------+
2181 | bwtype:RS | Session level usage represents | B | NORMAL |
2182 | | session aggregate and media level | | |
2183 | | usage indicates SUM of the | | |
2184 | | individual values while | | |
2185 | | multiplexing | | |
2186 | | | | |
2187 | bwtype:RR | Session level usage represents | B | NORMAL |
2188 | | session aggregate and media level | | |
2189 | | usage indicates SUM of the | | |
2190 | | individual values while | | |
2191 | | multiplexing | | |
2192 | | | | |
2193 +------------+-----------------------------------+-------+----------+
2195 RFC3556 bwtype Analysis
2197 6.3. RFC3890 - Bandwidth Modifier for SDP
2199 [RFC3890] defines a Session Description Protocol (SDP) Transport
2200 Independent Application Specific Maximum (TIAS) bandwidth modifier
2201 that does not include transport overhead; instead an additional
2202 packet rate attribute is defined. The transport independent bit-rate
2203 value together with the maximum packet rate can then be used to
2204 calculate the real bit-rate over the transport actually used.
2206 +------------------+-----------------------------+-------+----------+
2207 | Name | Notes | Level | Category |
2208 +------------------+-----------------------------+-------+----------+
2209 | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL |
2210 | | clearly defined | | |
2211 | | Offer/Answer usage. | | |
2212 | | | | |
2213 | bwtype:maxprate | The usage of TIAS and | B | SPECIAL |
2214 | | maxprate is not well | | |
2215 | | defined under multiplexing | | |
2216 | | | | |
2217 +------------------+-----------------------------+-------+----------+
2219 RFC3890 bwtype Analysis
2221 The intention of TIAS is that the media level bit-rate is multiplied
2222 with the known per-packet overhead for the selected transport and the
2223 maxprate value to determine the worst case bit-rate from the
2224 transport to more accurately capture the required usage. Summing
2225 TIAS values independently across m=lines and multiplying the computed
2226 sum with maxprate and the per-packet overhead would inflate the value
2227 significantly. Instead performing multiplication and adding the
2228 individual values is a more appropriate usage. This still ignores
2229 the fact that this is a send side declaration, and not intended for
2230 receiver negotiation.
2232 7. rtcp-fb Attribute Analysis
2234 This section analyzes rtcp-fb SDP attributes.
2236 7.1. RFC4585 - RTP/AVPF
2238 [RFC4585] defines an extension to the Audio-visual Profile (AVP) that
2239 enables receivers to provide, statistically, more immediate feedback
2240 to the senders and thus allows for short-term adaptation and
2241 efficient feedback-based repair mechanisms to be implemented.
2243 +----------+----------------------------+-------+-------------------+
2244 | Attr | Notes | Level | Category |
2245 | Name | | | |
2246 +----------+----------------------------+-------+-------------------+
2247 | ack rpsi | The attribute value must | M | IDENTICAL-PER-PT |
2248 | | be same for a given codec | | |
2249 | | configuration | | |
2250 | | | | |
2251 | ack app | Feedback parameters MUST | M | SPECIAL |
2252 | | be handled in the app | | |
2253 | | specific way when | | |
2254 | | multiplexed | | |
2255 | | | | |
2256 | nack | The attribute value must | M | IDENTICAL-PER-PT |
2257 | | be same for a given codec | | |
2258 | | configuration | | |
2259 | | | | |
2260 | nack pli | The attribute value must | M | IDENTICAL-PER-PT |
2261 | | be same for a given codec | | |
2262 | | configuration | | |
2263 | | | | |
2264 | nack sli | The attribute value must | M | IDENTICAL-PER-PT |
2265 | | be same for a given codec | | |
2266 | | configuration | | |
2267 | | | | |
2268 | nack | The attribute value must | M | IDENTICAL-PER-PT |
2269 | rpsi | be same for a given codec | | |
2270 | | configuration | | |
2271 | | | | |
2272 | nack app | Feedback parameters MUST | M | SPECIAL |
2273 | | be handled in the app | | |
2274 | | specific way when | | |
2275 | | multiplexed | | |
2276 | | | | |
2277 | trr-int | The attribute value must | M | IDENTICAL-PER-PT |
2278 | | be same for a given codec | | |
2279 | | configuration | | |
2280 | | | | |
2281 +----------+----------------------------+-------+-------------------+
2283 RFC4585 Attribute Analysis
2285 7.2. RFC5104 - Codec Control Messages in AVPF
2287 [RFC5104] specifies a few extensions to the messages defined in the
2288 Audio-Visual Profile with Feedback (AVPF). They are helpful
2289 primarily in conversational multimedia scenarios where centralized
2290 multipoint functionalities are in use. However, some are also usable
2291 in smaller multicast environments and point-to-point calls.
2293 +-------+-------------------------------+-------+-------------------+
2294 | Attr | Notes | Level | Category |
2295 | Name | | | |
2296 +-------+-------------------------------+-------+-------------------+
2297 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2298 | | same for a given codec | | |
2299 | | configuration | | |
2300 | | | | |
2301 +-------+-------------------------------+-------+-------------------+
2303 RFC5104 Attribute Analysis
2305 7.3. RFC6285 - Unicast-Based RAMS
2307 +-------+-------------------------------+-------+-------------------+
2308 | Name | Notes | Level | Category |
2309 +-------+-------------------------------+-------+-------------------+
2310 | nack | The attribute value must be | M | IDENTICAL-PER-PT |
2311 | rai | same for a given codec | | |
2312 | | configuration | | |
2313 | | | | |
2314 +-------+-------------------------------+-------+-------------------+
2316 RFC6285 Attribute Analysis
2318 7.4. RFC6679 - ECN for RTP over UDP/IP
2320 [RFC6679] specifies how Explicit Congestion Notification (ECN) can be
2321 used with the Real-time Transport Protocol (RTP) running over UDP,
2322 using the RTP Control Protocol (RTCP) as a feedback mechanism. It
2323 defines a new RTCP Extended Report (XR) block for periodic ECN
2324 feedback, a new RTCP transport feedback message for timely reporting
2325 of congestion events, and a Session Traversal Utilities for NAT
2326 (STUN) extension used in the optional initialization method using
2327 Interactive Connectivity Establishment (ICE).
2329 +------------------+---------------------------+-------+------------+
2330 | Name | Notes | Level | Category |
2331 +------------------+---------------------------+-------+------------+
2332 | ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL |
2333 | | the RTP Session level | | |
2334 | | | | |
2335 | nack ecn | This attribute enables | M | IDENTICAL |
2336 | | ECN at the RTP session | | |
2337 | | level | | |
2338 | | | | |
2339 +------------------+---------------------------+-------+------------+
2341 RFC6679 Attribute Analysis
2343 7.5. RFC6642 - Third-Party Loss Report
2345 In a large RTP session using the RTP Control Protocol (RTCP) feedback
2346 mechanism defined in [RFC4585], a feedback target may experience
2347 transient overload if some event causes a large number of receivers
2348 to send feedback at once. This overload is usually avoided by
2349 ensuring that feedback reports are forwarded to all receivers,
2350 allowing them to avoid sending duplicate feedback reports. However,
2351 there are cases where it is not recommended to forward feedback
2352 reports, and this may allow feedback implosion. [RFC6642] memo
2353 discusses these cases and defines a new RTCP Third-Party Loss Report
2354 that can be used to inform receivers that the feedback target is
2355 aware of some loss event, allowing them to suppress feedback.
2356 Associated Session Description Protocol (SDP) signaling is also
2357 defined.
2359 +--------+------------------------------+-------+-------------------+
2360 | Name | Notes | Level | Category |
2361 +--------+------------------------------+-------+-------------------+
2362 | nack | The attribute value must be | M | IDENTICAL-PER-PT |
2363 | tllei | same for a given codec | | |
2364 | | configuration | | |
2365 | | | | |
2366 | nack | The attribute value must be | M | IDENTICAL-PER-PT |
2367 | pslei | same for a given codec | | |
2368 | | configuration | | |
2369 | | | | |
2370 +--------+------------------------------+-------+-------------------+
2372 RFC6642 Attribute Analysis
2374 7.6. RFC5104 - Codec Control Messages in AVPF
2376 +--------+------------------------------+-------+-------------------+
2377 | Attr | Notes | Level | Category |
2378 | Name | | | |
2379 +--------+------------------------------+-------+-------------------+
2380 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2381 | fir | same for a given codec | | |
2382 | | configuration | | |
2383 | | | | |
2384 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2385 | tmmbr | same for a given codec | | |
2386 | | configuration | | |
2387 | | | | |
2388 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2389 | tstr | same for a given codec | | |
2390 | | configuration | | |
2391 | | | | |
2392 | ccm | The attribute value must be | M | IDENTICAL-PER-PT |
2393 | vbcm | same for a given codec | | |
2394 | | configuration | | |
2395 | | | | |
2396 +--------+------------------------------+-------+-------------------+
2398 RFC5104 Attribute Analysis
2400 8. group Attribute Analysis
2402 This section analyzes SDP "group" semantics.
2404 8.1. RFC5888 - SDP Grouping Framework
2406 [RFC5888] defines a framework to group "m" lines in the Session
2407 Description Protocol (SDP) for different purposes.
2409 +------------+---------------+-------+----------+
2410 | Name | Notes | Level | Category |
2411 +------------+---------------+-------+----------+
2412 | group:LS | Not Impacted | S | NORMAL |
2413 | | | | |
2414 | group:FID | Not Impacted | S | NORMAL |
2415 | | | | |
2416 +------------+---------------+-------+----------+
2418 RFC5888 Attribute Analysis
2420 8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows
2422 [RFC3524] defines an extension to the Session Description Protocol
2423 (SDP) grouping framework. It allows requesting a group of media
2424 streams to be mapped into a single resource reservation flow. The
2425 SDP syntax needed is defined, as well as a new "semantics" attribute
2426 called Single Reservation Flow (SRF).
2428 +------------+---------------+-------+----------+
2429 | Name | Notes | Level | Category |
2430 +------------+---------------+-------+----------+
2431 | group:SRF | Not Impacted | S | NORMAL |
2432 | | | | |
2433 +------------+---------------+-------+----------+
2435 RFC3524 Attribute Analysis
2437 8.3. RFC4091 - ANAT Semantics
2439 [RFC4091] defines the Alternative Network Address Types (ANAT)
2440 semantics for the Session Description Protocol (SDP) grouping
2441 framework. The ANAT semantics allow alternative types of network
2442 addresses to establish a particular media stream.
2444 +-------------+---------------------------+-------+-----------------+
2445 | Name | Notes | Level | Category |
2446 +-------------+---------------------------+-------+-----------------+
2447 | group:ANAT | ANAT semantics is | S | NOT RECOMMENDED |
2448 | | obseleted | | |
2449 | | | | |
2450 +-------------+---------------------------+-------+-----------------+
2452 RFC4091 Attribute Analysis
2454 8.4. RFC5956 - FEC Grouping Semantics in SDP
2456 [RFC5956] defines the semantics for grouping the associated source
2457 and FEC-based (Forward Error Correction) repair flows in the Session
2458 Description Protocol (SDP). The semantics defined in the document
2459 are to be used with the SDP Grouping Framework (RFC 5888). These
2460 semantics allow the description of grouping relationships between the
2461 source and repair flows when one or more source and/or repair flows
2462 are associated in the same group, and they provide support for
2463 additive repair flows. SSRC-level (Synchronization Source) grouping
2464 semantics are also defined in this document for Real-time Transport
2465 Protocol (RTP) streams using SSRC multiplexing.
2467 +---------------+---------------+-------+----------+
2468 | Name | Notes | Level | Category |
2469 +---------------+---------------+-------+----------+
2470 | group:FEC-FR | Not Impacted | S | NORMAL |
2471 | | | | |
2472 +---------------+---------------+-------+----------+
2474 RFC5956 Attribute Analysis
2476 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP
2478 [RFC5583] defines semantics that allow for signaling the decoding
2479 dependency of different media descriptions with the same media type
2480 in the Session Description Protocol (SDP). This is required, for
2481 example, if media data is separated and transported in different
2482 network streams as a result of the use of a layered or multiple
2483 descriptive media coding process.
2485 +--------+------------------------------+-------+-------------------+
2486 | Name | Notes | Level | Category |
2487 +--------+------------------------------+-------+-------------------+
2488 | depend | The attribute value must be | M | IDENTICAL-PER-PT |
2489 | lay | same for a given codec | | |
2490 | | configuration | | |
2491 | | | | |
2492 | depend | The attribute value must be | M | IDENTICAL-PER-PT |
2493 | mdc | same for a given codec | | |
2494 | | configuration | | |
2495 | | | | |
2496 +--------+------------------------------+-------+-------------------+
2498 RFC5583 Attribute Analysis
2500 8.6. RFC7104 - Duplication Grouping Semantics in the SDP
2502 [RFC7104] defines the semantics for grouping redundant streams in the
2503 Session Description Protocol (SDP). The semantics defined in this
2504 document are to be used with the SDP Grouping Framework. Grouping
2505 semantics at the Synchronization Source (SSRC) level are also defined
2506 in this document for RTP streams using SSRC multiplexing.
2508 +------------+---------------+-------+----------+
2509 | Name | Notes | Level | Category |
2510 +------------+---------------+-------+----------+
2511 | group:DUP | Not Impacted | S | NORMAL |
2512 | | | | |
2513 +------------+---------------+-------+----------+
2515 RFC7104 Attribute Analysis
2517 9. ssrc-group Attribute Analysis
2519 This section analyzes "ssrc-group" semantics.
2521 9.1. RFC5576 - Source-Specific SDP Attributes
2523 +-------------------+---------------+-------+----------+
2524 | Name | Notes | Level | Category |
2525 +-------------------+---------------+-------+----------+
2526 | ssrc-group:FID | Not Impacted | SR | NORMAL |
2527 | | | | |
2528 | ssrc-group:FEC | Not Impacted | SR | NORMAL |
2529 | | | | |
2530 | ssrc-groupFEC-FR | Not Impacted | SR | NORMAL |
2531 | | | | |
2532 +-------------------+---------------+-------+----------+
2534 RFC5576 Attribute Analysis
2536 9.2. RFC7104 - Duplication Grouping Semantics in the SDP
2538 +-----------------+---------------+-------+----------+
2539 | Name | Notes | Level | Category |
2540 +-----------------+---------------+-------+----------+
2541 | ssrc-group:DUP | Not Impacted | SR | NORMAL |
2542 | | | | |
2543 +-----------------+---------------+-------+----------+
2545 RFC7104 Attribute Analysis
2547 10. QoS Mechanism Token Analysis
2549 This section analyzes QoS tokes specified with SDP.
2551 10.1. RFC5432 - QoS Mechanism Selection in SDP
2552 +-------+----------------------------------------+-------+----------+
2553 | Name | Notes | Level | Category |
2554 +-------+----------------------------------------+-------+----------+
2555 | rsvp | Not Impacted, since QOS mechanisms are | B | NORMAL |
2556 | | applied per flow. | | |
2557 | | | | |
2558 | nsis | Not Impacted, since QOS mechanisms are | B | NORMAL |
2559 | | applied per flow. | | |
2560 | | | | |
2561 +-------+----------------------------------------+-------+----------+
2563 RFC5432 Attribute Analysis
2565 11. k= Attribute Analysis
2567 11.1. RFC4566 SDP: Session Description Protocol
2569 +------+------------------------------------+-------+---------------+
2570 | Name | Notes | Level | Category |
2571 +------+------------------------------------+-------+---------------+
2572 | k= | It is NOT recommended to use this | S | NOT |
2573 | | attribute | | RECOMMENDED |
2574 | | | | |
2575 +------+------------------------------------+-------+---------------+
2577 RFC4566 Attribute Analysis
2579 12. content Attribute Analysis
2581 12.1. RFC4796
2583 +------------------+---------------+-------+----------+
2584 | Name | Notes | Level | Category |
2585 +------------------+---------------+-------+----------+
2586 | content:slides | Not Impacted | M | NORMAL |
2587 | | | | |
2588 | content:speaker | Not Impacted | M | NORMAL |
2589 | | | | |
2590 | content:main | Not Impacted | M | NORMAL |
2591 | | | | |
2592 | content:sl | Not Impacted | M | NORMAL |
2593 | | | | |
2594 | content:alt | Not Impacted | M | NORMAL |
2595 | | | | |
2596 +------------------+---------------+-------+----------+
2598 RFC4796 Attribute Analysis
2600 13. Payload Formats
2602 13.1. RFC5109 - RTP Payload Format for Generic FEC
2604 [RFC5109] describes a payload format for generic Forward Error
2605 Correction (FEC) for media data encapsulated in RTP. It is based on
2606 the exclusive-or (parity) operation. The payload format allows end
2607 systems to apply protection using various protection lengths and
2608 levels, in addition to using various protection group sizes to adapt
2609 to different media and channel characteristics. It enables complete
2610 recovery of the protected packets or partial recovery of the critical
2611 parts of the payload depending on the packet loss situation.
2613 +---------------------+----------------------+-------+--------------+
2614 | Name | Notes | Level | Category |
2615 +---------------------+----------------------+-------+--------------+
2616 | audio/ulpfec | Not recommended for | M | NOT |
2617 | | multiplexing due to | | RECOMMENDED |
2618 | | reuse of SSRCs | | |
2619 | | | | |
2620 | video/ulpfec | Not recommended for | M | NOT |
2621 | | multiplexing due to | | RECOMMENDED |
2622 | | reuse of SSRCs | | |
2623 | | | | |
2624 | text/ulpfec | Not recommended for | M | NOT |
2625 | | multiplexing due to | | RECOMMENDED |
2626 | | reuse of SSRCs | | |
2627 | | | | |
2628 | application/ulpfec | Not recommended for | M | NOT |
2629 | | multiplexing due to | | RECOMMENDED |
2630 | | reuse of SSRCs | | |
2631 | | | | |
2632 +---------------------+----------------------+-------+--------------+
2634 RFC5109 Payload Format Analysis
2636 Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make
2637 it possible to use ULP with multiplexing and ULP is allowed when used
2638 with that.
2640 14. Multiplexing Considerations for Encapsulating Attributes
2642 This sections deals with recommendations for defining the
2643 multiplexing characteristics of the SDP attributes that encapsulate
2644 other SDP attributes/parameters. Such attributes as of today, for
2645 example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of
2646 a generic framework for indicating and negotiating transport, media
2647 and media format related capabilities in the SDP.
2649 The behavior of such attributes under multiplexing is in turn defined
2650 by the multiplexing behavior of the attributes they encapsulate which
2651 are made known once the Offer/Answer negotiation process is
2652 completed.
2654 14.1. RFC3407 - cpar Attribute Analysis
2656 [RFC3407] capability parameter attribute (a=cpar) encapsulates b=
2657 (bandwidth) or an a= attribute. For bandwidth attribute
2658 encapsulation, the category SUM is inherited. For the case of a=
2659 attribute, the category corresponding to the SDP attribute being
2660 encapsulated is inherited.
2662 v=0
2663 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
2664 s=
2665 c=IN IP4 host.atlanta.example.com
2666 t=0 0
2667 m=video 3456 RTP/AVP 100
2668 a=rtpmap:100 VP8/90000
2669 a=sqn: 0
2670 a=cdsc: 1 video RTP/AVP 100
2671 a=cpar: a=rtcp-mux
2672 m=video 3456 RTP/AVP 101
2673 a=rtpmap:101 VP8/90000
2674 a=fmtp:100 max-fr=15;max-fs=1200
2675 a=cdsc: 2 video RTP/AVP 101
2676 a=cpar: a=rtcp-mux
2678 In the above example ,the category IDENTICAL is inherited for the
2679 cpar encapsulated rtcp-mux attribute.
2681 14.2. RFC5939 Analysis
2683 [RFC5939] defines a general SDP capability negotiation framework. It
2684 also specifies how to provide transport protocols and SDP attributes
2685 as capabilities and negotiate them using the framework.
2687 For this purpose, [RFC5939] defines the following
2689 o A set of capabilities for the session and its associated media
2690 stream components, supported by each side. The attribute
2691 ("a=acap") defines how to list an attribute name and its
2692 associated value (if any) as a capability. The attribute
2693 ("a=tcap") defines how to list transport protocols (e.g., "RTP/
2694 AVP") as capabilities.
2696 o A set of potential configurations ("a=pcfg") provided by the
2697 offerer to indicate whcich combination of those capabilities can
2698 be used for the session and its associated media stream
2699 components. Potential configurations are not ready for use until
2700 fully negotiated. They provide an alternative that may be used,
2701 subject to SDP capability negotiation procedures. In particular
2702 the answerer may choose one of the potential configurations for
2703 use as part of the current Offer/Answer exchange.
2705 o An actual configuration ("a=acfg") for the session and its
2706 associated media stream components. The actual configuration
2707 identifies the potential configuration that was negotiated for
2708 use. Use of an actual configuration does not require any further
2709 negotiation.
2711 o A negotiation process that takes the current actual and the set of
2712 potential configurations (combinations of capabilities) as input
2713 and provides the negotiated actual configurations as output. In
2714 [RFC5939] the negotiation process is done independently for each
2715 media description.
2717 14.2.1. Recommendation - Procedures for Potential Configuration Pairing
2719 This section provides recommendations for entities generating and
2720 processing SDP under the generic capability negotiation framework as
2721 defined in [RFC5939] under the context of media stream multiplexing.
2723 These recommendations are provided for the purposes of enabling the
2724 Offerer to make sure that the generated potential configurations
2725 between the multiplexed streams can (easily) be negotiated to be
2726 consistent between those streams. In particular, the procedures aim
2727 to simplify Answerer's procedure to choose potential configurations
2728 that are consistent across all the bundled media descriptions.
2730 A potential configuration selects a set of attributes and parameters
2731 that become part of the media description when negotiated. When
2732 multiplexing media descriptions with potential configurations
2733 specified, there may be a need for coordinating this selection
2734 between multiplexed media descriptions ensuring right multiplexing
2735 behavior.
2737 Although it is possible to analyze the various potential
2738 configurations in bundled media descriptions to find combinations
2739 that satisfy such constraints, it can quickly become complicated to
2740 do so.
2742 The procedures defined in [RFC5939] state that each potential
2743 configuration in the SDP has a unique configuration number, however
2744 the scope of uniqueness is limited to each media description. To
2745 make it simple for the answerer to chose valid combinations of
2746 potential configurations across media descriptions in a given bundle
2747 group, we provide a simple rule for constructiong potential
2748 configurations:-
2750 o Let m-bundle be the set of media descriptions that form a given
2751 bundle .
2753 o Let m-bundle-pcfg be the set of media descriptions in m-bundle
2754 that include one or more potential configurations.
2756 o Each media description in m-bundle-pcfg MUST have at least one
2757 potential configuration with the same configuration number (e.g.
2758 "1").
2760 o For each potential configuration with configuration number x in m-
2761 bundle-pcfg, the offerer MUST ensure that if the answerer chooses
2762 configuration number x in each of the media descriptions in m-
2763 bundle-pcfg, then the resulting SDP will have all multiplexing
2764 constraints satisfied for those media descriptions.
2766 o Since it is nearly impossible to define a generic mechanism for
2767 various capability extensions , this document does't provide
2768 procedures for dealing with the capability extension attributes.
2769 However, Section 14.3 provide analysis of media capability
2770 extension attributes as defined in [RFC6871].
2772 The above allows the answerer to easily find multiplexing compatible
2773 combinations of potential configurations:- The answerer simply choses
2774 a potential configuration (number) that is present in all of the
2775 media descriptions with potential configurations in the bundle.
2777 Note that it is still possible for the offerer to provide additional
2778 potential configurations with independent configuration numbers. The
2779 answerer will have to perform more complicated analysis to determine
2780 valid multiplexed combinations of those.
2782 14.2.1.1. Example: Transport Capability Multiplexing
2783 v=0
2784 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
2785 s=
2786 c=IN IP4 host.atlanta.example.com
2787 t=0 0
2788 a=tcap:1 RTP/SAVPF
2789 a=tcap:2 RTP/SAVP
2790 a=group:BUNDLE audio video
2791 m= audio
2792 a=mid:audio
2793 a=pcfg:1 t=1
2794 a=pcfg:2
2795 m= video
2796 a=mid:video
2797 a=pcfg:1 t=1
2798 a=pcfg:2 t=2
2800 In the example above, the potential configurations that offer
2801 transport protocol capability of RTP/SAVPF has the same configuration
2802 number "1" in both the audio and video media descriptions.
2804 14.2.1.2. Example: Attribute Capability Multiplexing
2806 v=0
2807 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
2808 s=
2809 c=IN IP4 host.atlanta.example.com
2810 t=0 0
2811 a=acap:1 a=rtcp-mux
2812 a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80
2813 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
2814 a=group:BUNDLE audio video
2815 m= audio 49172 RTP/AVP 99
2816 a=mid:audio
2817 a=pcfg:1 a=1
2818 a=pcfg:2
2819 m= video 560024 RTP/AVP 100
2820 a=mid:video
2821 a=pcfg:1 a=1
2822 a=pcfg:2 a=2
2824 In the example above, the potential configuration number "1" is
2825 repeated while referring to attribute capability a=rtcp-mux, since
2826 the behavior is IDENTICAL for the attribute a=rtcp-mux under
2827 multiplexing.
2829 14.3. RFC6871 Analysis
2831 [RFC6871] extends capability negotiation framework described in
2832 [RFC5939] by defining media capabilities that can be used to indicate
2833 and negotiate media types and their associated format parameters. It
2834 also allows indication of latent configurations and session
2835 capabilities.
2837 14.3.1. Recommendation: Dealing with Payload Type Numbers
2839 [RFC6871] defines a new payload type ("pt") parameter to be used with
2840 the potential, actual and latent configuration parameters. The
2841 parameter associates RTP payload type numbers with the referenced
2842 RTP-based media format capabilities ("a=rmcap") defined in [RFC6871]
2843 and is appropriate only when the transport protocol uses RTP. This
2844 means that the same payload type number can be assigned as part of
2845 potential or actual configurations in different media descriptions in
2846 a bundle. There are rules for the usage of identical Payload Type
2847 values across multiplexed m=lines as described in
2848 [I-D.ietf-mmusic-sdp-bundle-negotiation], which MUST be followed here
2849 as well. As described in Section 14.2.1, the use of identical
2850 configuration numbers for compatible configurations in different
2851 media descriptions that are part of the bundle provides a way to
2852 ensure that the answerer can easily pick compatible configurations
2853 here as well.
2855 14.3.1.1. Example: Attribute Capability Under Shared Payload Type
2857 The attributes (a=rmcap, a=mfcap) follow the above recommendations
2858 under mutliplexing.
2860 v=0
2861 o=- 25678 753849 IN IP4 192.0.2.1
2862 s=
2863 c=IN IP4 192.0.2.1
2864 t=0 0
2865 a=creq:med-v0
2866 m=audio 54322 RTP/AVP 96
2867 a=rtpmap:96 AMR-WB/16000/1
2868 a=fmtp:96 mode-change-capability=1; max-red=220;
2869 mode-set=0,2,4,7
2870 a=rmcap:1,3 audio AMR-WB/16000/1
2871 a=rmcap:2 audio AMR/8000/1
2872 a=mfcap:1,2 mode-change-capability=1
2873 a=mfcap:3 mode-change-capability=2
2874 a=pcfg:1 m=1 pt=1:96
2875 a=pcfg:2 m=2 pt=2:97
2876 a=pcfg:3 m=3 pt=3:98
2877 m=audio 54322 RTP/AVP 96
2878 a=rtpmap:96 AMR-WB/16000/1
2879 a=fmtp:96 mode-change-capability=1; max-red=220;
2880 mode-set=0,2,4,7
2881 a=rmcap:4 audio AMR/8000/1
2882 a=rmcap:5 audio OPUS/48000/2
2883 a=mfcap:5 minptime=40
2884 a=mfcap:4 mode-change-capability=1
2885 a=pcfg:1 m=4 pt=4:97
2886 a=pcfg:4 m=5 pt=5:101
2888 In the example above, the potential configuration number "1" is
2889 repeated when referring to media and media format capability used for
2890 the Payload Type 97. This implies that both the media capability 2
2891 and 4 along with their media format capabilities MUST refer to the
2892 same codec configuration , as per the definition of IDENTICAL-PER-PT.
2894 14.3.2. Recommendation: Dealing with Latent Configurations
2896 [RFC6871] adds the notion of a latent configurations, which provides
2897 configuration information that may be used to guide a subsequent
2898 offer/exchange, e.g. by adding another media stream or use
2899 alternative codec combinations not currently offered. Latent
2900 configurations have configuration numbers which cannot overlap with
2901 the potential configuration numbers [RFC6871]. Supported
2902 combinations of potential and latent configurations are indicated by
2903 use of the "a=sescap" attribute, however use of this attribute is not
2904 recommended with bundled media, since it requires the use of unique
2905 configuration numbers across the SDP. Taken together, this means
2906 there is no well-defined way to indicate supported combinations of
2907 latent configurations, or combinations of latent and potential
2908 configurations with bundled media. It is still allowed to use the
2909 latent configuration attribute, however the limitations above will
2910 apply. To determine valid combinations, actual negotiation will have
2911 to be attempted subsequently instead.
2913 15. IANA Considerations
2915 [RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
2916 document.]
2918 The IANA is requested to add a new column named "Mux Category" to all
2919 several of the subregistries in the "Session Description Protocol
2920 (SDP) Parameters" registry. Section 15.1 defines a new subregistry
2921 for identifying the initial registrations for various multiplexing
2922 categories applicable as proposed in this document.
2924 The tables in Section 15.2 identify name of an entry in the existing
2925 subregistry and specify the value to put in the new "Mux Category"
2926 column of the associated IANA registry. Any entries in the existing
2927 tables that do not have a value for the "Mux Category" specified in
2928 this RFC will get a value of "TBD". Future specifications can change
2929 the "TBD" entries to the correct value.
2931 15.1. New 'Multiplexing Categories' subregistry
2933 A new sub-registry needs to be defined called the "Multiplexing
2934 Categories", with the following registrations created initially:
2935 "NORMAL", "NOT RECOMMENDED", "IDENTICAL", "TRANSPORT", "IDENTICAL-
2936 PER-PT", "SPECIAL" and "TBD" as defined in this document.
2938 Initial value registration for "Mux Category".
2940 +-------------------------+-----------+
2941 | Multiplexing Categories | Reference |
2942 +-------------------------+-----------+
2943 | NORMAL | RFCXXXX |
2944 | NOT RECOMMENDED | RFCXXXX |
2945 | IDENTICAL | RFCXXXX |
2946 | TRANSPORT | RFCXXXX |
2947 | IDENTICAL-PER-PT | RFCXXXX |
2948 | SPECIAL | RFCXXXX |
2949 | TBD | RFCXXXX |
2950 +-------------------------+-----------+
2952 Further entries may be registered on a first-come first-serve basis.
2953 Each registration needs to indicate the multiplexing category value
2954 to be added to the "Multiplexing Categories" subregistry as defined
2955 in this section.
2957 Such a registration must also indicate the applicability of the newly
2958 defined multiplexing category value to various subregistries defined
2959 at "Session Description Protocol (SDP) Parameters".
2961 The general registration procedures of [RFC4566] apply.
2963 15.2. 'Mux Category' column for subregistries
2965 Each sub-section identifies a subregistry in the "Session Description
2966 Protocol (SDP) Parameters" registry. The tables list the column that
2967 identifies the SDP attribute name/Token/Value from the corresponding
2968 subregistries and the values to be used for the new "Mux Category"
2969 column to be added.
2971 15.2.1. Table: SDP bwtype
2973 The following values are to be added to the 'SDP bwtype' subregistry
2974 in the "Session Description Protocol (SDP) Parameters" registry. The
2975 references should be updated to point at this RFC as well as the
2976 previous references.
2978 +----------+--------------+
2979 | SDP Name | Mux Category |
2980 +----------+--------------+
2981 | CT | NORMAL |
2982 | AS | SUM |
2983 | RS | NORMAL |
2984 | RR | NORMAL |
2985 | TIAS | SPECIAL |
2986 +----------+--------------+
2988 15.2.2. Table: att-field (session level)
2990 The following values are to be added to the "att-field (session
2991 level)" subregistry in the "Session Description Protocol (SDP)
2992 Parameters registry. The references should be updated to point at
2993 this RFC as well as the previous references.
2995 +---------------------+------------------+
2996 | SDP Name | Mux Category |
2997 +---------------------+------------------+
2998 | cat | NORMAL |
2999 | keywds | NORMAL |
3000 | type | NORMAL |
3001 | type:broadcast | NORMAL |
3002 | type:H332 | NORMAL |
3003 | type:meeting | NORMAL |
3004 | type:moderated | NORMAL |
3005 | type:test | NORMAL |
3006 | charset | NORMAL |
3007 | charset:iso8895-1 | NORMAL |
3008 | tool | NORMAL |
3009 | ipbcp | NORMAL |
3010 | group | NORMAL |
3011 | ice-lite | NORMAL |
3012 | ice-options | NORMAL |
3013 | bcastversion | NORMAL |
3014 | 3GPP-Integrity-Key | NOT RECOMMENDED |
3015 | 3GPP-SDP-Auth | NOT RECOMMENDED |
3016 | alt-group | NOT RECOMMENDED |
3017 | PSCid | NORMAL |
3018 | bc_service | NORMAL |
3019 | bc_program | NORMAL |
3020 | bc_service_package | NORMAL |
3021 | sescap | NOT RECOMMENDED |
3022 | rtsp-ice-d-m | NOT RECOMMENDED |
3023 +---------------------+------------------+
3025 15.2.3. Table: att-field (both session and media level)
3027 The following values are to be added to the "att-field (both session
3028 and media level)" subregistry in the "Session Description Protocol
3029 (SDP) Parameters registry. The references should be updated to point
3030 at this RFC as well as the previous references.
3032 +-------------------------+-------------------+
3033 | SDP Name | Mux Category |
3034 +-------------------------+-------------------+
3035 | recvonly | NORMAL |
3036 | sendrecv | NORMAL |
3037 | sendonly | NORMAL |
3038 | sdplang | NORMAL |
3039 | lang | NORMAL |
3040 | h248item | SPECIAL |
3041 | sqn | NORMAL |
3042 | cdsc | NORMAL |
3043 | cpar | INHERIT |
3044 | cparmin | SPECIAL |
3045 | cparmax | SPECIAL |
3046 | rtcp-xr | NORMAL |
3047 | maxprate | SPECIAL |
3048 | setup | IDENTICAL |
3049 | connection | IDENTICAL |
3050 | key-mgmt | IDENTICAL |
3051 | source-filter | IDENTICAL |
3052 | inactive | NORMAL |
3053 | fingerprint | TRANSPORT |
3054 | flute-tsi | TBD |
3055 | flute-ch | TBD |
3056 | FEC-declaration | TBD |
3057 | FEC-OTI-extension | TBD |
3058 | content-desc | TBD |
3059 | ice-pwd | TRANSPORT |
3060 | ice-ufrag | TRANSPORT |
3061 | stkmstream | NORMAL |
3062 | qos-mech-send | NORMAL |
3063 | qos-mech-recv | NORMAL |
3064 | csup | NORMAL |
3065 | creq | NORMAL |
3066 | acap | INHERIT |
3067 | tcap | INHERIT |
3068 | 3GPP-QoE-Metrics | NOT RECOMMENDED |
3069 | 3GPP-Asset-Information | NOT RECOMMENDED |
3070 | mbms-mode | NOT RECOMMENDED |
3071 | mbms-repair | NOT RECOMMENDED |
3072 | ike-setup | IDENTICAL |
3073 | psk-fingerprint | IDENTICAL |
3074 | multicast-rtcp | IDENTICAL |
3075 | rmcap | IDENTICAL-PER-PT |
3076 | omcap | NORMAL |
3077 | mfcap | IDENTICAL-PER-PT |
3078 | mscap | INHERIT |
3079 | bcap | INHERIT |
3080 | ccap | IDENTICAL |
3081 | icap | NORMAL |
3082 | 3gpp_sync_info | NORMAL |
3083 | 3gpp_MaxRecvSDUSize | NORMAL |
3084 | etag | NOT RECOMMENDED |
3085 | duplication-delay | NORMAL |
3086 | range | NOT RECOMMENDED |
3087 | control | NOT RECOMMENDED |
3088 | mtag | NOT RECOMMENDED |
3089 | ts-refclk | NORMAL |
3090 | mediaclk | NORMAL |
3091 | calgextmap | NORMAL |
3092 +-------------------------+-------------------+
3094 15.2.4. Table: att-field (media level only)
3096 The following values are to be added to the "att-field (media level
3097 only" registry in the "Session Description Protocol (SDP) Parameters
3098 registry. The references should be updated to point at this RFC as
3099 well as the previous references.
3101 +---------------------------+-------------------+
3102 | SDP Name | Mux Category |
3103 +---------------------------+-------------------+
3104 | ptime | IDENTICAL-PER-PT |
3105 | orient | NORMAL |
3106 | orient:portrait | NORMAL |
3107 | orient:landscape | NORMAL |
3108 | orient:seascape | NORMAL |
3109 | framerate | IDENTICAL-PER-PT |
3110 | quality | NORMAL |
3111 | rtpmap | IDENTICAL-PER-PT |
3112 | fmtp | IDENTICAL-PER-PT |
3113 | rtpred1 | NOT RECOMMENDED |
3114 | rtpred2 | NOT RECOMMENDED |
3115 | T38FaxVersion | NORMAL |
3116 | T38MaxBitRate | NORMAL |
3117 | T38MaxBitRate | NORMAL |
3118 | T38FaxTranscodingMMR | NORMAL |
3119 | T38FaxTranscodingJBIG | NORMAL |
3120 | T38FaxRateManagement | NORMAL |
3121 | T38FaxMaxBuffer | NORMAL |
3122 | T38FaxMaxDatagram | NORMAL |
3123 | T38FaxUdpEC | NORMAL |
3124 | maxptime | IDENTICAL-PER-PT |
3125 | des | NOT RECOMMENDED |
3126 | curr | NOT RECOMMENDED |
3127 | conf | NOT RECOMMENDED |
3128 | mid | NORMAL |
3129 | rtcp | IDENTICAL |
3130 | rtcp-fb | IDENTICAL-PER-PT |
3131 | label | NORMAL |
3132 | T38VendorInfo | NORMAL |
3133 | crypto | TRANSPORT |
3134 | eecid | NORMAL |
3135 | aalType | NORMAL |
3136 | capability | NORMAL |
3137 | qosClass | NORMAL |
3138 | bcob | NORMAL |
3139 | stc | NORMAL |
3140 | upcc | NORMAL |
3141 | atmQOSparms | NORMAL |
3142 | atmQOSparms | NORMAL |
3143 | abrParms | NORMAL |
3144 | abrSetup | NORMAL |
3145 | bearerType | NORMAL |
3146 | lij | NORMAL |
3147 | anycast | NORMAL |
3148 | cache | NORMAL |
3149 | bearerSigIE | NORMAL |
3150 | aalApp | NORMAL |
3151 | cbrRate | NORMAL |
3152 | sbc | NORMAL |
3153 | clkrec | NORMAL |
3154 | fec | NORMAL |
3155 | prtfl | NORMAL |
3156 | structure | NORMAL |
3157 | cpsSDUsize | NORMAL |
3158 | all2CPS | NORMAL |
3159 | all2CPSSDUrate | NORMAL |
3160 | aal2sscs3661unassured | NORMAL |
3161 | aal2sscs3661assured | NORMAL |
3162 | aal2sscs3662 | NORMAL |
3163 | aal5sscop | NORMAL |
3164 | atmmap | NORMAL |
3165 | silenceSupp | NORMAL |
3166 | ecan | NORMAL |
3167 | gc | NORMAL |
3168 | profileDesc | NORMAL |
3169 | vsel | NORMAL |
3170 | dsel | NORMAL |
3171 | fsel | NORMAL |
3172 | onewaySel | NORMAL |
3173 | codecConfig | NORMAL |
3174 | isup_usi | NORMAL |
3175 | uiLayer1_Prot | NORMAL |
3176 | chain | NORMAL |
3177 | floorctrl | IDENTICAL |
3178 | confid | NORMAL |
3179 | userid | NORMAL |
3180 | floorid | NORMAL |
3181 | FEC | NORMAL |
3182 | profileDesc | NORMAL |
3183 | accept-types | NORMAL |
3184 | accept-wrapped-types | NORMAL |
3185 | max-size | NORMAL |
3186 | path | NORMAL |
3187 | dccp-service-code | NOT RECOMMENDED |
3188 | rtcp-mux | IDENTICAL |
3189 | candidate | TRANSPORT |
3190 | ice-mismatch | NORMAL |
3191 | remote-candidates | TRANSPORT |
3192 | SRTPAuthentication | NORMAL |
3193 | SRTPROCTxRate | NORMAL |
3194 | rtcp-rsize | IDENTICAL |
3195 | file-selector | NORMAL |
3196 | file-transfer-id | NORMAL |
3197 | file-disposition | NORMAL |
3198 | file-date | NORMAL |
3199 | file-icon | NORMAL |
3200 | file-range | NORMAL |
3201 | depend | IDENTICAL-PER-PT |
3202 | ssrc | NORMAL |
3203 | ssrc-group | NORMAL |
3204 | rtcp-unicast | IDENTICAL |
3205 | pcfg | SPECIAL |
3206 | acfg | SPECIAL |
3207 | zrtp-hash | NOT RECOMMENDED |
3208 | X-predecbufsize | NOT RECOMMENDED |
3209 | X-initpredecbufperiod | NOT RECOMMENDED |
3210 | X-initpostdecbufperiod | NOT RECOMMENDED |
3211 | X-decbyterate | NOT RECOMMENDED |
3212 | 3gpp-videopostdecbufsize | NOT RECOMMENDED |
3213 | framesize | NOT RECOMMENDED |
3214 | 3GPP-SRTP-Config | NOT RECOMMENDED |
3215 | alt | NOT RECOMMENDED |
3216 | alt-default-id | NOT RECOMMENDED |
3217 | 3GPP-Adaption-Support | NOT RECOMMENDED |
3218 | mbms-flowid | NOT RECOMMENDED |
3219 | fec-source-flow | SPECIAL |
3220 | fec-repair-flow | SPECIAL |
3221 | repair-window | SPECIAL |
3222 | rams-updates | NOT RECOMMENDED |
3223 | imageattr | IDENTICAL-PER-PT |
3224 | cfw-id | NORMAL |
3225 | portmapping-req | NOT RECOMMENDED |
3226 | g.3gpp.cat | NORMAL |
3227 | g.3gpp.crs | NORMAL |
3228 | ecn-capable-rtp | IDENTICAL |
3229 | visited-realm | TRANSPORT |
3230 | secondary-realm | TRANSPORT |
3231 | omr-s-cksum | NORMAL |
3232 | omr-m-cksum | NORMAL |
3233 | omr-codecs | NORMAL |
3234 | omr-codecs | NORMAL |
3235 | omr-m-att | NORMAL |
3236 | omr-m-bw | NORMAL |
3237 | omr-s-bw | NORMAL |
3238 | msrcp-cema | NORMAL |
3239 | dccp-port | NOT RECOMMENDED |
3240 | resource | NORMAL |
3241 | channel | NORMAL |
3242 | cmid | NORMAL |
3243 | content | NORMAL |
3244 | lcfg | SPECIAL |
3245 | loopback | NORMAL |
3246 | loopback-source | NORMAL |
3247 | loopback-mirror | NORMAL |
3248 | chatroom | TBD |
3249 | altc | TRANSPORT |
3250 | T38FaxMaxIFP | NORMAL |
3251 | T38FaxUdpECDepth | NORMAL |
3252 | T38FaxUdpFECMaxSpan | NORMAL |
3253 | T38ModemType | NORMAL |
3254 | cs-correlation | NORMAL |
3255 | rtcpidms | NORMAL |
3256 +---------------------------+-------------------+
3258 15.2.5. Table: att-field (source level)
3260 The following values are to be added to the "att-field (source
3261 level)" registry in the "Session Description Protocol (SDP)
3262 Parameters registry. The references should be updated to point at
3263 this RFC as well as the previous references.
3265 +----------------+-------------------+
3266 | SDP Name | Mux Category |
3267 +----------------+-------------------+
3268 | cname | NORMAL |
3269 | previous-ssrc | NORMAL |
3270 | fmtp | IDENTICAL-PER-PT |
3271 | ts-refclk | NORMAL |
3272 | mediaclk | NORMAL |
3273 +----------------+-------------------+
3275 15.2.6. Table: content SDP Parameters
3277 The following values are to be added to the "content SDP Parameters"
3278 subregistry in the "Session Description Protocol (SDP) Parameters
3279 registry. The references should be updated to point at this RFC as
3280 well as the previous references.
3282 +----------+--------------+
3283 | SDP Name | Mux Category |
3284 +----------+--------------+
3285 | slides | NORMAL |
3286 | speaker | NORMAL |
3287 | sl | NORMAL |
3288 | main | NORMAL |
3289 | alt | NORMAL |
3290 +----------+--------------+
3292 15.2.7. Table: Semantics for the 'group' SDP Attribute
3294 The following values are to be added to the "Semantics for the
3295 "group" SDP Attribute" subregistry in the "Session Description
3296 Protocol (SDP) Parameters registry. The references should be updated
3297 to point at this RFC as well as the previous references.
3299 +---------+------------------+
3300 | Token | Mux Category |
3301 +---------+------------------+
3302 | LS | NORMAL |
3303 | FID | NORMAL |
3304 | SRF | NORMAL |
3305 | ANAT | NOT RECOMMENDED |
3306 | FEC | NORMAL |
3307 | FEC-FR | NORMAL |
3308 | CS | NORMAL |
3309 | DDP | NORMAL |
3310 | DUP | NORMAL |
3311 +---------+------------------+
3313 15.2.8. Table: 'rtcp-fb' Attribute Values
3315 The following values are to be added to the " 'rtcp-fb' Attribute
3316 Values" subregistry in the "Session Description Protocol (SDP)
3317 Parameters registry. The references should be updated to point at
3318 this RFC as well as the previous references.
3320 +------------+-------------------+
3321 | Value Name | Mux Category |
3322 +------------+-------------------+
3323 | ack | IDENTICAL-PER-PT |
3324 | app | SPECIAL |
3325 | ccm | IDENTICAL-PER-PT |
3326 | nack | IDENTICAL-PER-PT |
3327 | trr-int | IDENTICAL-PER-PT |
3328 +------------+-------------------+
3330 15.2.9. Table: 'ack' and 'nack' Attribute Values
3332 The following values are to be added to the " 'ack' and 'nack'
3333 Attribute Values" subregistry in the "Session Description Protocol
3334 (SDP) Parameters" registry. The references should be updated to
3335 point at this RFC as well as the previous references.
3337 +------------+-------------------+
3338 | Value Name | Mux Category |
3339 +------------+-------------------+
3340 | sli | IDENTICAL-PER-PT |
3341 | pli | IDENTICAL-PER-PT |
3342 | rpsi | IDENTICAL-PER-PT |
3343 | app | IDENTICAL-PER-PT |
3344 | rai | IDENTICAL-PER-PT |
3345 | tllei | IDENTICAL-PER-PT |
3346 | pslei | IDENTICAL-PER-PT |
3347 | ecn | IDENTICAL |
3348 +------------+-------------------+
3350 15.2.10. Table: 'depend' SDP Attribute Values
3352 The following values are to be added to the " 'depend' SDP Attribute
3353 Values" subregistry in the "Session Description Protocol (SDP)
3354 Parameters registry. The references should be updated to point at
3355 this RFC as well as the previous references.
3357 +-------+-------------------+
3358 | Token | Mux Category |
3359 +-------+-------------------+
3360 | lay | IDENTICAL-PER-PT |
3361 | mdc | IDENTICAL-PER-PT |
3362 +-------+-------------------+
3364 15.2.11. Table: 'cs-correlation' Attribute Values
3366 The following values are to be added to the " "cs-correlation"
3367 Attribute Values" subregistry in the "Session Description Protocol
3368 (SDP) Parameters registry. The references should be updated to point
3369 at this RFC as well as the previous references.
3371 +-----------+--------------+
3372 | Value | Mux Category |
3373 +-----------+--------------+
3374 | callerid | NORMAL |
3375 | uuie | NORMAL |
3376 | dtmf | NORMAL |
3377 | external | NORMAL |
3378 +-----------+--------------+
3380 15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute
3382 The following values are to be added to the Semantics for the
3383 "Semantics for the "ssrc-group" SDP Attribute" subregistry in the
3384 "Session Description Protocol (SDP) Parameters registry. The
3385 references should be updated to point at this RFC as well as the
3386 previous references.
3388 +---------+--------------+
3389 | Token | Mux Category |
3390 +---------+--------------+
3391 | FID | NORMAL |
3392 | FEC | NORMAL |
3393 | FEC-FR | NORMAL |
3394 | DUP | NORMAL |
3395 +---------+--------------+
3397 15.2.13. Table: SDP/RTSP key management protocol identifiers
3399 The following values are to be added to the "SDP/RTSP key management
3400 protocol identifiers" subregistry in the "Session Description
3401 Protocol (SDP) Parameters registry. The references should be updated
3402 to point at this RFC as well as the previous references.
3404 +------------+--------------+
3405 | Value Name | Mux Category |
3406 +------------+--------------+
3407 | mikey | IDENTICAL |
3408 +------------+--------------+
3410 15.2.14. Table: Codec Control Messages
3412 The following values are to be added to the "Codec Control Messages"
3413 subregistry in the "Session Description Protocol (SDP) Parameters
3414 registry. The references should be updated to point at this RFC as
3415 well as the previous references.
3417 +------------+-------------------+
3418 | Value Name | Mux Category |
3419 +------------+-------------------+
3420 | fir | IDENTICAL-PER-PT |
3421 | tmmbr | IDENTICAL-PER-PT |
3422 | tstr | IDENTICAL-PER-PT |
3423 | vbcm | IDENTICAL-PER-PT |
3424 +------------+-------------------+
3426 15.2.15. Table: QoS Mechanism Tokens
3428 The following values are to be added to the "QoS Mechanism Tokens"
3429 subregistry in the "Session Description Protocol (SDP) Parameters
3430 registry. The references should be updated to point at this RFC as
3431 well as the previous references.
3433 +---------------+--------------+
3434 | QoS Mechanism | Mux Category |
3435 +---------------+--------------+
3436 | rsvp | NORMAL |
3437 | nsis | NORMAL |
3438 +---------------+--------------+
3440 15.2.16. Table: SDP Capability Negotiation Option Tags
3442 The following values are to be added to the "SDP Capability
3443 Negotiation Option Tags" subregistry in the "Session Description
3444 Protocol (SDP) Parameters registry. The references should be updated
3445 to point at this RFC as well as the previous references.
3447 +---------------+--------------+
3448 | QoS Mechanism | Mux Category |
3449 +---------------+--------------+
3450 | cap-v0 | NORMAL |
3451 | med-v0 | NORMAL |
3452 | bcap-v0 | NORMAL |
3453 | ccap-v0 | NORMAL |
3454 | icap-v0 | NORMAL |
3455 +---------------+--------------+
3457 15.2.17. Table: Timestamp Reference Clock Source Parameters
3459 The following values are to be added to the "Timestamp Reference
3460 Clock Source Parameters" subregistry in the "Session Description
3461 Protocol (SDP) Parameters registry. The references should be updated
3462 to point at this RFC as well as the previous references.
3464 +----------+--------------+
3465 | Name | Mux Category |
3466 +----------+--------------+
3467 | ntp | NORMAL |
3468 | ptp | NORMAL |
3469 | gps | NORMAL |
3470 | gal | NORMAL |
3471 | glonass | NORMAL |
3472 | local | NORMAL |
3473 | private | NORMAL |
3474 +----------+--------------+
3476 15.2.18. Table: Media Clock Source Parameters
3478 The following values are to be added to the "Media Clock Source
3479 Parameters" subegistry in the "Session Description Protocol (SDP)
3480 Parameters registry. The references should be updated to point at
3481 this RFC as well as the previous references.
3483 +-----------+--------------+
3484 | Name | Mux Category |
3485 +-----------+--------------+
3486 | sender | NORMAL |
3487 | direct | NORMAL |
3488 | IEEE1722 | NORMAL |
3489 +-----------+--------------+
3491 16. Security Considerations
3493 This document does not add any new security considerations beyond the
3494 existing considerations in the RFC for protocols that are being
3495 multiplexed together.
3497 The ways that SRTP streams are keyed is not believed to create any
3498 two-time pad vulnerability for the currently defined SRTP keying
3499 mechanism.
3501 17. Acknowledgments
3503 I would like to thank Cullen Jennings and Flemming Andreasen for
3504 suggesting the categories, contributing text and reviewing the draft.
3505 I would also link to thank Magnus Westerlund, Christer Holmberg,
3506 Jonathan Lennox, Bo Burman, and Dan on suggesting structural changes
3507 helping improve the document readability.
3509 I would like also to thank following experts on their inputs and
3510 reviews as listed - Flemming Andreasen(5.20,5.28,5.29,14), Rohan
3511 Mahy(5.45), Eric Burger(5.22),Christian Huitema(5.13), Christer
3512 Holmberg(5.17,5.22,5.40,5.41), Richard Ejzak (5.36,5.42,5.43,5.44),
3513 Colin Perkins(5.7,5.8), Magnus westerlund(5.2,5.3,5.9,5.26,
3514 5.27,6.1,6.2,6.3,8.3,7), Roni Evens(5.12,5.27,8.4), Subha
3515 Dhesikan(5.5,12.1,14), Dan Wing(5.6,5.11,5.30,5.34,5.37), Ali C
3516 Begen(5.1,5.16,5.18,5.21,5.33,8.2,8.4,13.1), Bo Burman (7.2,7.6),
3517 Charles Eckel(5.14,5.23,5.24,9.1,8.5), Paul Kyzivat(5.24), Ian
3518 Johansson(5.15), Saravanan Shanmugham(5.10), Paul E Jones(5.25),
3519 Rajesh Kumar(5.39), Jonathan Lennox(5.31,5,14,11.1), Mo
3520 Zanaty(5.4,5.19,8.1,8.3,8.5,12.1), Christian Huitema (5.13), Qin Wu
3521 (5.38 PM-Dir review).
3523 18. Change Log
3525 [RFC EDITOR NOTE: Please remove this section when publishing]
3527 Changes from draft-ietf-mmusic-sdp-mux-attributes-03
3529 o More re-work on the IANA section.
3531 o Clean ups preparing for the last call.
3533 Changes from draft-ietf-mmusic-sdp-mux-attributes-02
3535 o Incorporated suggestions from Flemming on Capability Negotiation.
3537 o Closed open issues from IETF90
3539 o Added IANA section to list the categories for all the SDP
3540 attributes anlayzed
3542 o Lots of cleanup
3544 o Reformatted Refernces section to use short-form notation
3546 Changes from draft-ietf-mmusic-sdp-mux-attributes-01
3548 o Updated section 15 to provide detailed recommendation on dealing
3549 with encapsulating attributes. Also updated sections 5.20, 5.28,
3550 5.29 to refer to Section 15.
3552 o Added new categories IDENTICAL-PER-PT and INHERIT
3554 o Updated Sections 16 to add the new categories.
3556 o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the
3557 category IDENTICAL-PER-PT.
3559 o Reformatted section 4 to add individual categories to their own
3560 sections.
3562 Changes from draft-ietf-mmusic-sdp-mux-attributes-00
3564 o Added Section 15 to provide recommendations on multiplexing SDP
3565 encapsulating attributes. Also updated sections 5.20, 5.28, 5.29
3566 to refer to Section 15.
3568 o Updated Section 5.38 to incorporate PM-dir review inputs from Qin
3569 Wu
3571 o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more
3572 clarity.
3574 o Fixed few nits regarding sentence clarity and fill-in the NOTES
3575 section where information was lacking.
3577 Changes from draft-nandakumar-mmusic-mux-attributes-05
3579 o Renamed the document to be a WG document.
3581 o Added Section 14.
3583 o Updated Open Issues based on IETF88 discussions.
3585 Changes from draft-nandakumar-mmusic-mux-attributes-04
3587 o Added few OPEN ISSUES that needs to be discussed.
3589 o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4,
3590 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1
3592 o Updated Table Column name Current to Level and improved TRANSPORT
3593 category explanation on suggestions form Dan Wing.
3595 o Grouped all the rtcp-fb attribute analysis under a single section
3596 as suggested by Magnus/
3598 Changes from draft-nandakumar-mmusic-mux-attributes-03
3600 o Maintenance change to clean up grammatical nits and wordings.
3602 Changes from draft-nandakumar-mmusic-mux-attributes-02
3604 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34,
3605 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
3606 the inputs from the respective RFC Authors.
3608 Changes from draft-nandakumar-mmusic-mux-attributes-01
3610 o Replaced Category BAD with NOT RECOMMENDED.
3612 o Added Category TBD.
3614 o Updated IANA Consideration Section.
3616 Changes from draft-nandakumar-mmusic-mux-attributes-00
3618 o Added new section for dealing with FEC payload types.
3620 19. References
3622 19.1. Normative References
3624 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
3625 Requirement Levels", BCP 14, RFC 2119, March 1997.
3627 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
3628 Description Protocol", RFC 4566, July 2006.
3630 19.2. Informative References
3632 [H.248.15]
3633 "Gateway control protocol: SDP H.248 package attribute",
3634 .
3636 [I-D.ietf-mmusic-sdp-bundle-negotiation]
3637 Holmberg, C., Alvestrand, H., and C. Jennings,
3638 "Negotiating Media Multiplexing Using the Session
3639 Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
3640 negotiation-12 (work in progress), October 2014.
3642 [I.D-draft-ietf-dart-dscp-rtp]
3643 Black, D. and P. Jones, "The Session Description Protocol
3644 (SDP) Content Attribute", draft-ietf-dart-dscp-rtp-07
3645 (work in progress), September 2014.
3647 [IANA] "Session Description Protocol (SDP) Parameters",
3648 .
3651 [ITU-T-REC.Q1970]
3652 "Q.1970 : BICC IP bearer control protocol",
3653 .
3655 [R3GPPTS183.063]
3656 "TISPAN - IMS based ITPV Stage 3 specification.",
3657 .
3660 [R3GPPTS24.182]
3661 "IP Multimedia Subsystem (IMS) Customized Alerting Tones
3662 (CAT); Protocol specification",
3663 .
3665 [R3GPPTS24.183]
3666 "IP Multimedia Subsystem (IMS) Customized Ringing Signal
3667 (CRS); Protocol specification",
3668 .
3670 [R3GPPTS24.229]
3671 "IP multimedia call control protocol based on Session
3672 Initiation Protocol (SIP) and Session Description Protocol
3673 (SDP);",
3674 .
3676 [R3GPPTS26.114]
3677 "IP multimedia Subsystem : Media Handling and
3678 interaction",
3679 .
3681 [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the
3682 Session Description Protocol (SDP) for ATM Bearer
3683 Connections", RFC 3108, May 2001.
3685 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
3686 with Session Description Protocol (SDP)", RFC 3264, June
3687 2002.
3689 [RFC3312] Camarillo, G., Marshall, W., and J. Rosenberg,
3690 "Integration of Resource Management and Session Initiation
3691 Protocol (SIP)", RFC 3312, October 2002.
3693 [RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple
3694 Capability Declaration", RFC 3407, October 2002.
3696 [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to
3697 Resource Reservation Flows", RFC 3524, April 2003.
3699 [RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth
3700 Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC
3701 3556, July 2003.
3703 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
3704 in Session Description Protocol (SDP)", RFC 3605, October
3705 2003.
3707 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
3708 Protocol Extended Reports (RTCP XR)", RFC 3611, November
3709 2003.
3711 [RFC3890] Westerlund, M., "A Transport Independent Bandwidth
3712 Modifier for the Session Description Protocol (SDP)", RFC
3713 3890, September 2004.
3715 [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network
3716 Address Types (ANAT) Semantics for the Session Description
3717 Protocol (SDP) Grouping Framework", RFC 4091, June 2005.
3719 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
3720 the Session Description Protocol (SDP)", RFC 4145,
3721 September 2005.
3723 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E.
3724 Carrara, "Key Management Extensions for Session
3725 Description Protocol (SDP) and Real Time Streaming
3726 Protocol (RTSP)", RFC 4567, July 2006.
3728 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
3729 Description Protocol (SDP) Security Descriptions for Media
3730 Streams", RFC 4568, July 2006.
3732 [RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol
3733 (SDP) Source Filters", RFC 4570, July 2006.
3735 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
3736 Transport Layer Security (TLS) Protocol in the Session
3737 Description Protocol (SDP)", RFC 4572, July 2006.
3739 [RFC4574] Levin, O. and G. Camarillo, "The Session Description
3740 Protocol (SDP) Label Attribute", RFC 4574, August 2006.
3742 [RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format
3743 for Binary Floor Control Protocol (BFCP) Streams", RFC
3744 4583, November 2006.
3746 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
3747 "Extended RTP Profile for Real-time Transport Control
3748 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July
3749 2006.
3751 [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description
3752 Protocol (SDP) Content Attribute", RFC 4796, February
3753 2007.
3755 [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
3756 Session Relay Protocol (MSRP)", RFC 4975, September 2007.
3758 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
3759 "Codec Control Messages in the RTP Audio-Visual Profile
3760 with Feedback (AVPF)", RFC 5104, February 2008.
3762 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error
3763 Correction", RFC 5109, December 2007.
3765 [RFC5159] Dondeti, L. and A. Jerichow, "Session Description Protocol
3766 (SDP) Attributes for Open Mobile Alliance (OMA) Broadcast
3767 (BCAST) Service and Content Protection", RFC 5159, March
3768 2008.
3770 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
3771 (ICE): A Protocol for Network Address Translator (NAT)
3772 Traversal for Offer/Answer Protocols", RFC 5245, April
3773 2010.
3775 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP
3776 Header Extensions", RFC 5285, July 2008.
3778 [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of
3779 Service (QoS) Mechanism Selection in the Session
3780 Description Protocol (SDP)", RFC 5432, March 2009.
3782 [RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size
3783 Real-Time Transport Control Protocol (RTCP): Opportunities
3784 and Consequences", RFC 5506, April 2009.
3786 [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
3787 and P. Kyzivat, "A Session Description Protocol (SDP)
3788 Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
3789 May 2009.
3791 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
3792 Media Attributes in the Session Description Protocol
3793 (SDP)", RFC 5576, June 2009.
3795 [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding
3796 Dependency in the Session Description Protocol (SDP)", RFC
3797 5583, July 2009.
3799 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
3800 Protocol (RTCP) Extensions for Single-Source Multicast
3801 Sessions with Unicast Feedback", RFC 5760, February 2010.
3803 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
3804 Control Packets on a Single Port", RFC 5761, April 2010.
3806 [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control
3807 Protocol (DCCP)", RFC 5762, April 2010.
3809 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
3810 for Establishing a Secure Real-time Transport Protocol
3811 (SRTP) Security Context Using Datagram Transport Layer
3812 Security (DTLS)", RFC 5763, May 2010.
3814 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
3815 Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
3817 [RFC5939] Andreasen, F., "Session Description Protocol (SDP)
3818 Capability Negotiation", RFC 5939, September 2010.
3820 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in
3821 the Session Description Protocol", RFC 5956, September
3822 2010.
3824 [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions
3825 Defined for 3GPP Packet-Switched Streaming Service and
3826 Multimedia Broadcast/Multicast Service", RFC 6064, January
3827 2011.
3829 [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source-
3830 Specific Multicast (SSM) Sessions", RFC 6128, February
3831 2011.
3833 [RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
3834 Path Key Agreement for Unicast Secure RTP", RFC 6189,
3835 April 2011.
3837 [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for
3838 the Internet Key Exchange Protocol (IKE) in the Session
3839 Description Protocol (SDP)", RFC 6193, April 2011.
3841 [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media
3842 Control Channel Framework", RFC 6230, May 2011.
3844 [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image
3845 Attributes in the Session Description Protocol (SDP)", RFC
3846 6236, May 2011.
3848 [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping
3849 between Unicast and Multicast RTP Sessions", RFC 6284,
3850 June 2011.
3852 [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
3853 "Unicast-Based Rapid Acquisition of Multicast RTP
3854 Sessions", RFC 6285, June 2011.
3856 [RFC6364] Begen, A., "Session Description Protocol Elements for the
3857 Forward Error Correction (FEC) Framework", RFC 6364,
3858 October 2011.
3860 [RFC6642] Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP)
3861 Extension for a Third-Party Loss Report", RFC 6642, June
3862 2012.
3864 [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
3865 and K. Carlberg, "Explicit Congestion Notification (ECN)
3866 for RTP over UDP", RFC 6679, August 2012.
3868 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
3869 Establishment for Media Anchoring (CEMA) for the Message
3870 Session Relay Protocol (MSRP)", RFC 6714, August 2012.
3872 [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
3873 Datagram Congestion Control Protocol UDP Encapsulation for
3874 NAT Traversal", RFC 6773, November 2012.
3876 [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control
3877 Protocol Version 2 (MRCPv2)", RFC 6787, November 2012.
3879 [RFC6849] Kaplan, H., Hedayat, K., Venna, N., Jones, P., and N.
3880 Stratton, "An Extension to the Session Description
3881 Protocol (SDP) and Real-time Transport Protocol (RTP) for
3882 Media Loopback", RFC 6849, February 2013.
3884 [RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session
3885 Description Protocol (SDP) Media Capabilities
3886 Negotiation", RFC 6871, February 2013.
3888 [RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S.
3889 Veikkolainen, "The Session Description Protocol (SDP)
3890 Alternate Connectivity (ALTC) Attribute", RFC 6947, May
3891 2013.
3893 [RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman,
3894 "Miscellaneous Capabilities Negotiation in the Session
3895 Description Protocol (SDP)", RFC 7006, September 2013.
3897 [RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping
3898 Semantics in the Session Description Protocol", RFC 7104,
3899 January 2014.
3901 [RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session
3902 Description Protocol (SDP) Extension for Setting Audio and
3903 Video Media Streams over Circuit-Switched Bearers in the
3904 Public Switched Telephone Network (PSTN)", RFC 7195, May
3905 2014.
3907 [RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay
3908 Attribute in the Session Description Protocol", RFC 7197,
3909 April 2014.
3911 [RFC7226] Villamizar, C., McDysan, D., Ning, S., Malis, A., and L.
3912 Yong, "Requirements for Advanced Multipath in MPLS
3913 Networks", RFC 7226, May 2014.
3915 [RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O.,
3916 Boronat, F., Montagud, M., and K. Gross, "Inter-
3917 Destination Media Synchronization (IDMS) Using the RTP
3918 Control Protocol (RTCP)", RFC 7272, June 2014.
3920 [RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H.
3921 Stokking, "RTP Clock Source Signalling", RFC 7273, June
3922 2014.
3924 [T.38] "Procedures for real-time Group 3 facsimile communication
3925 over IP networks", .
3927 Author's Address
3929 Suhas Nandakumar
3930 Cisco
3931 170 West Tasman Drive
3932 San Jose, CA 95134
3933 USA
3935 Email: snandaku@cisco.com