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2 Network Working Group S. Nandakumar
3 Internet-Draft Cisco
4 Intended status: Standards Track July 03, 2014
5 Expires: January 4, 2015
7 A Framework for SDP Attributes when Multiplexing
8 draft-ietf-mmusic-sdp-mux-attributes-02
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 transport layer flow.
22 The scope of this specification is to provide a framework for
23 analyzing the multiplexing characteristics of SDP attributes. The
24 specification also categorizes existing attributes based on the
25 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 January 4, 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 Table of Contents
61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
63 3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 5
64 4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . 6
65 4.1. Category: NORMAL . . . . . . . . . . . . . . . . . . . . 6
66 4.2. Category: NOT RECOMMENDED . . . . . . . . . . . . . . . . 7
67 4.3. Category: IDENTICAL . . . . . . . . . . . . . . . . . . . 7
68 4.4. Category: SUM . . . . . . . . . . . . . . . . . . . . . . 8
69 4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 8
70 4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 9
71 4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 10
72 4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 10
73 5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 11
74 5.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 11
75 5.2. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 12
76 5.3. RFC5761 - Multiplexing RTP and RTCP . . . . . . . . . . . 13
77 5.4. RFC4574 - SDP Label Attribute . . . . . . . . . . . . . . 13
78 5.5. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 13
79 5.6. RFC4568 - SDP Security Descriptions . . . . . . . . . . . 14
80 5.7. RFC5762 - RTP over DCCP . . . . . . . . . . . . . . . . . 14
81 5.8. RFC6773 - DCCP-UDP Encapsulation . . . . . . . . . . . . 15
82 5.9. RFC5506 - Reduced-Size RTCP in RTP Profile . . . . . . . 16
83 5.10. RFC6787 - Media Resource Control Protocol Version 2 . . . 16
84 5.11. RFC5245 - Interactive Connectivity Establishment (ICE) . 17
85 5.12. RFC5285 - RTP Header Extensions . . . . . . . . . . . . . 18
86 5.13. RFC3605 - RTCP attribute in SDP . . . . . . . . . . . . . 19
87 5.14. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 19
88 5.15. RFC6236 - Image Attributes in SDP . . . . . . . . . . . . 20
89 5.16. RFC6285 - Rapid Acquisition of Multicast RTP Sessions . . 21
90 5.17. RFC6230 - Media Control Channel Framework . . . . . . . . 21
91 5.18. RFC6364 - SDP Elements for FEC Framework . . . . . . . . 22
92 5.19. RFC4796 - Content Attribute . . . . . . . . . . . . . . . 22
93 5.20. RFC3407 - SDP Simple Capability Declaration . . . . . . . 23
94 5.21. RFC6284 - Port Mapping between Unicast and Multicast RTP
95 Sessions . . . . . . . . . . . . . . . . . . . . . . . . 23
96 5.22. RFC6714 - MSRP-CEMA . . . . . . . . . . . . . . . . . . . 24
97 5.23. RFC4583 - SDP Format for BFCP Streams . . . . . . . . . . 24
98 5.24. RFC5547 - SDP Offer/Answer for File Transfer . . . . . . 25
99 5.25. RFC6489 - SDP and RTP Media Loopback Extension . . . . . 25
100 5.26. RFC5760 - RTCP with Unicast Feedback . . . . . . . . . . 26
101 5.27. RFC3611 - RTCP XR . . . . . . . . . . . . . . . . . . . . 26
102 5.28. RFC5939 - SDP Capability Negotiation . . . . . . . . . . 27
103 5.29. RFC6871- SDP Media Capabilities Negotiation . . . . . . . 27
104 5.30. RFC4567 - Key Management Extensions for SDP and RTSP . . 28
105 5.31. RFC4572 - Comedia over TLS in SDP . . . . . . . . . . . . 28
106 5.32. RFC4570 - SDP Source Filters . . . . . . . . . . . . . . 29
107 5.33. RFC6128 - RTCP Port for Multicast Sessions . . . . . . . 29
108 5.34. RFC6189 - ZRTP . . . . . . . . . . . . . . . . . . . . . 30
109 5.35. RFC4145 - Connection-Oriented Media . . . . . . . . . . . 31
110 5.36. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . 31
111 5.37. RFC6193 - Media Description for IKE in SDP . . . . . . . 32
112 5.38. RFC6064 - SDP and RTSP Extensions for 3GPP . . . . . . . 33
113 5.39. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . . 35
114 5.40. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 36
115 5.41. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 37
116 5.42. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 37
117 5.43. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 38
118 5.44. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 39
119 5.45. RFC4975 - The Message Session Relay Protocol . . . . . . 40
120 5.46. Historical . . . . . . . . . . . . . . . . . . . . . . . 41
121 6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 42
122 6.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 42
123 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . 42
124 6.3. RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . 43
125 7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 44
126 7.1. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 44
127 7.2. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 45
128 7.3. RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . 45
129 7.4. RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . . 45
130 7.5. RFC6642 - Third-Party Loss Report . . . . . . . . . . . . 46
131 7.6. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 46
132 8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 47
133 8.1. RFC5888 - SDP Grouping Framework . . . . . . . . . . . . 47
134 8.2. RFC3524 - Mapping Media Streams to Resource Reservation
135 Flows . . . . . . . . . . . . . . . . . . . . . . . . . . 47
136 8.3. RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . 48
137 8.4. RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . . 48
138 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP . . 49
139 9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 49
140 9.1. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 49
141 10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 50
142 10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 50
143 11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 50
144 11.1. RFC4566 SDP: Session Description Protocol . . . . . . . 50
146 12. content Atribute Analysis . . . . . . . . . . . . . . . . . . 50
147 12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 50
148 13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 51
149 13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . 51
150 14. Multiplexing Media Streams and DSCP Markings . . . . . . . . 52
151 14.1. Option A . . . . . . . . . . . . . . . . . . . . . . . . 52
152 14.2. Option B . . . . . . . . . . . . . . . . . . . . . . . . 53
153 15. Multiplexing Considerations for Encapsulating Attributes . . 53
154 15.1. RFC3407 - cpar Attribute Analysis . . . . . . . . . . . 53
155 15.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 54
156 15.2.1. Recommendations . . . . . . . . . . . . . . . . . . 54
157 15.2.1.1. Recommendation-1: Transport Capability Analysis 55
158 15.2.1.2. Recommendation-2: Attribute Capability Analysis 55
159 15.2.1.3. Recommendation-3: Sescap Attribute Analysis . . 56
160 15.2.1.4. Recommendation-4: Capability Extension
161 Attributes . . . . . . . . . . . . . . . . . . . 56
162 15.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 56
163 15.3.1. Recommendation-5: Attribute Capability Under Shared
164 Payload Type . . . . . . . . . . . . . . . . . . . . 56
165 15.4. Recommendation-6: Offer/Answer Negotiation Expectations 57
166 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 59
167 17. Security Considerations . . . . . . . . . . . . . . . . . . . 60
168 18. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 60
169 19. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 61
170 20. References . . . . . . . . . . . . . . . . . . . . . . . . . 62
171 20.1. Normative References . . . . . . . . . . . . . . . . . . 62
172 20.2. Informative References . . . . . . . . . . . . . . . . . 62
173 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 68
175 1. Introduction
177 Real-Time Communication Web (RTCWeb) framework requires Real-time
178 Transport Protocol (RTP) as the media transport protocol and Session
179 Description Protocol (SDP) [RFC4566] for describing and negotiating
180 multi-media communication sessions.
182 SDP defines several attributes for capturing characteristics that
183 apply to the individual media descriptions (described by "m=" lines")
184 and the overall multimedia session. Typically different media types
185 (audio, video etc) described using different media descriptions
186 represent separate RTP Sessions that are carried over individual
187 transport layer flows. However in the IETF RTCWEB WG, a need to use
188 a single 5-tuple for sending and receiving media associated with
189 multiple SDP media descriptions ("m=" lines) has been identified.
190 This would e.g. allow the usage of a single set of Interactive
191 Connectivity Establishment (ICE) [RFC5245] candidates for multiple
192 media descriptions. This in turn has made necessary to understand
193 the interpretation and usage of the SDP attributes defined for the
194 multiplexed media descriptions.
196 Given the number of SDP attributes registered with the IANA [IANA]
197 and possibility of new attributes being defined in the future, there
198 is need for generic future-proof framework to analyze these
199 attributes for their applicability in the transport multiplexing use-
200 cases.
202 The document starts with providing the motivation for requiring such
203 a framework. This is followed by introduction to the SDP attribute
204 analysis framework/procedures, following which several sections
205 applies the framework to the SDP attributes registered with the IANA
206 [IANA]
208 2. Terminology
210 The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
211 "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
212 interpreted as described in [RFC2119].
214 3. Motivation
216 The time and complications of setting up ICE [RFC5245] and DTLS-SRTP
217 [RFC5763] transports for use by RTP, and conservation of ports, forms
218 an requirement to try and reduce the number of transport level flows
219 needed. This has resulted in the definition of ways, such as,
220 [I-D.ietf-mmusic-sdp-bundle-negotiation] and
221 [I-D.ietf-avt-multiplexing-rtp] to multiplex RTP over a single
222 transport flow in order to preserve network resources such as port
223 numbers. This imposes further restrictions on applicability of these
224 SDP attributes as they are defined today.
226 The specific problem is that there are attribute combinations which
227 make sense when specified on independent m-lines -- as with classical
228 SDP -- that do not make sense when those m-lines are then multiplexed
229 over the same transport. To give an obvious example, ICE permits
230 each m=line to have an independently specified ice-ufrag attribute.
231 However, if the media from multiple m-lines is multiplexed over the
232 same ICE component, then the meaning of media-level ice-ufrag
233 attributes becomes muddled.
235 As of today there are close to 250 SDP attributes registered with the
236 IANA [IANA] and more will be added in the future. There is no
237 clearly defined procedure to establish the validity/applicability of
238 these attribute when used with transport multiplexing.
240 4. SDP Attribute Analysis Framework
242 Attributes in an SDP session description can be defined at the
243 session-level and media-level. These attributes could be
244 semantically grouped as noted below.
246 o Attributes related to media content such as media type, encoding
247 schemes, payload types.
249 o Attributes specifying media transport characteristics like RTP/
250 RTCP port numbers, network addresses, QOS.
252 o Metadata description attributes capturing session timing and
253 origin information.
255 o Attributes establishing relationships between media streams such
256 as grouping framework
258 With the above semantic grouping as the reference, the proposed
259 framework classifies each attribute into one of the following
260 categories:
262 4.1. Category: NORMAL
264 Attributes that can be independently specified when multiplexing and
265 retain their original semantics.
267 In the example given below, the direction and label attributes are
268 independently specified for audio and video m=lines. These
269 attributes are not impacted by multiplexing these media streams over
270 a single transport layer flow.
272 v=0
273 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
274 s=
275 c=IN IP4 host.atlanta.example.com
276 t=0 0
277 m=audio 49172 RTP/AVP 99
278 a=sendonly
279 a=label:1
280 a=rtpmap:99 iLBC/8000
281 m=video 49172 RTP/AVP 31
282 a=recvonly
283 a=label:2
284 a=rtpmap:31 H261/90000
286 4.2. Category: NOT RECOMMENDED
288 Attributes that are recommended against multiplexing since their
289 usage under multiplexing might lead to incorrect behavior.
291 Example: Multiplexing media descriptions having attribute zrtp-hash
292 defined with the media descriptions lacking it, would either
293 complicate the handling of multiplexed streams or might fail
294 multiplexing altogether.
296 v=0
297 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
298 s=
299 c=IN IP4 client.biloxi.example.com
300 t=0 0
301 m=audio 3456 RTP/AVP 97 // with zrtp
302 a=rtpmap:97 iLBC/8000
303
304 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
305 df881ae642c371ba46df
306
307 m=video 34567 RTP/AVP 31 //without zrtp
308 a=rtpmap:31 H261/90000
310 4.3. Category: IDENTICAL
312 Attributes that MUST be identical across all the media descriptions
313 being multiplexed.
315 Attributes such as rtcp-mux fall into this category. Since RTCP
316 reporting is done per RTP Session, RTCP Multiplexing MUST to enabled
317 for both the audio and video m=lines in the example below if they are
318 transported over a single 5-tuple.
320 v=0
321 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
322 s=
323 c=IN IP4 client.biloxi.example.com
324 t=0 0
325 m=audio 34567 RTP/AVP 97
326 a=rtcp-mux
327 m=video 34567 RTP/AVP 31
328 a=rtpmap:31 H261/90000
329 a=rtcp-mux
331 4.4. Category: SUM
333 Attributes can be set as they are normally used but software using
334 them in a multiplex case, MUST apply the sum of all the attributes
335 being multiplexed instead of trying to use each one. This is
336 typically used for bandwidth or other rate limiting attributes to the
337 underlining transport.
339 The software parsing the SDP sample below, should use the aggregate
340 Application Specific (AS) bandwidth value from the individual media
341 descriptions to determine the AS value for the multiplexed session.
342 Thus the calculated AS value would be 256+64 bytes for the given
343 example.
345 v=0
346 o=mhandley 2890844526 2890842807 IN IP4 126.16.64.4
347 c=IN IP4 client.biloxi.example.com
348 t=0 0
349 m=audio 49170 RTP/AVP 0
350 b=AS:64
351 m=video 51372 RTP/AVP 31
352 b=AS:256
354 4.5. Category: TRANSPORT
356 Attributes that can be set normally for multiple items in a
357 multiplexed group but the software MUST pick just one of the
358 attribute of the given type for use. The one chosen is the attribute
359 associated with the "m=" line that represents the information being
360 used for the transport of the RTP.
362 In the example below, "a=crypto" attribute is defined for both the
363 audio and the video m=lines. The video media line's a=crypto
364 attribute is chosen since its mid value (bar) appears first in the
365 a=group:BUNDLE line. This is due to BUNDLE grouping semantic
366 [I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values
367 from m=line corresponding to the mid appearing first on the
368 a=group:BUNDLE line to be considered for setting up the RTP
369 Transport.
371 v=0
372 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
373 s=
374 c=IN IP4 host.atlanta.example.com
375 t=0 0
376 a=group:BUNDLE bar foo
377 m=audio 49172 RTP/AVP 99
378 a=mid:foo
379 a=crypto:1 AES_CM_128_HMAC_SHA1_80
380 inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32
381 a=rtpmap:99 iLBC/8000
382 m=video 51374 RTP/AVP 31
383 a=mid:bar
384 a=crypto:1 AES_CM_128_HMAC_SHA1_80
385 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
386 a=rtpmap:96 H261/90000
388 4.6. Category: INHERIT
390 Attributes that encapsulate other SDP attributes and their
391 multiplexing characteristics are inherited from the attributes they
392 encapsulate. Such attributes as of today, are defined in [RFC3407],
393 [RFC5939] and [RFC6871] as part of a generic framework for indicating
394 and negotiating transport, media and media format related
395 capabilities in the SDP.
397 v=0
398 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
399 s=
400 c=IN IP4 host.atlanta.example.com
401 t=0 0
402 m=video 3456 RTP/AVP 100
403 a=rtpmap:100 VP8/90000
404 a=fmtp:100 max-fr=30;max-fs=8040
405 a=sqn: 0
406 a=cdsc: 1 video RTP/AVP 100
407 a=cpar: a=rtcp-mux
408 m=video 3456 RTP/AVP 101
409 a=rtpmap:101 VP8/90000
410 a=fmtp:100 max-fr=15;max-fs=1200
411 a=cdsc: 2 video RTP/AVP 101
412 a=cpar: a=rtcp-mux
414 In the above example , the category IDENTICAL is inherited for the
415 cpar encapsulated rtcp-mux attribute.
417 4.7. Category: IDENTICAL-PER-PT
419 Attributes that define the RTP payload configuration on per Payload
420 Type basis and MUST have identical values across all the media
421 descriptions for a given RTP Payload Type when repeated.
423 In the SDP example below, Payload Types 96 and 97 are repeated across
424 all the video m= lines and all the payload specific parameters (ex:
425 rtpmap, fmtp) are identical.
427 v=0
428 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
429 s=
430 c=IN IP4 host.atlanta.example.com
431 t=0 0
432 a=group:BUNDLE cam1, cam2
433 m = video 96 97
434 a=mid:cam1
435 a=rtpmap:96 H264/90000
436 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
437 max-mbps=108000; max-br=1000
438 a=rtpmap:97 H264/90000
439 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
440 max-mbps=7200; max-br=200
441 m = video 96 97
442 a=mid:cam2
443 a=rtpmap:96 H264/90000
444 a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
445 max-mbps=108000; max-br=1000
446 a=rtpmap:97 H264/90000
447 a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
448 max-mbps=7200; max-br=200
450 4.8. Category: SPECIAL
452 Attributes where the text in the source draft must be consulted for
453 further handling when multiplexed.
455 As an example, for the attribute extmap, the specification defining
456 the extension MUST be referred to understand the multiplexing
457 implications.
459 5. Analysis of Existing Attributes
461 This section analyzes attributes listed in IANA [IANA] grouped under
462 the IETF document that defines them. The "Level" column indicates
463 whether the attribute is currently specified as:
465 o S -- Session level
467 o M -- Media level
469 o B -- Both
471 o SR -- Source-level (for a single SSRC)
473 5.1. RFC4566 - SDP: Session Description Protocol
475 RFC4566 [RFC4566] defines the Session Description Protocol (SDP) that
476 is intended for describing multimedia sessions for the purposes of
477 session announcement, session invitation, and other forms of
478 multimedia session initiation
480 +------------+--------------------------+-------+-------------------+
481 | Attr Name | Notes | Level | Category |
482 +------------+--------------------------+-------+-------------------+
483 | sendrecv | Not impacted | B | NORMAL |
484 | | | | |
485 | sendonly | Not impacted | B | NORMAL |
486 | | | | |
487 | recvonly | Not impacted | B | NORMAL |
488 | | | | |
489 | inactive | Not impacted | B | NORMAL |
490 | | | | |
491 | cat | Not impacted | S | NORMAL |
492 | | | | |
493 | ptime | The attribute value must | M | IDENTICAL-PER-PT |
494 | | be same for a given | | |
495 | | codec configuration | | |
496 | | | | |
497 | maxptime | The attribute value must | M | IDENTICAL-PER-PT |
498 | | be same for a given | | |
499 | | codec configuration | | |
500 | | | | |
501 | orient | Not Impacted | M | NORMAL |
502 | | | | |
503 | framerate | The attribute value must | M | IDENTICAL-PER-PT |
504 | | be same for a given | | |
505 | | codec configuration | | |
506 | | | | |
507 | quality | Not Impacted | M | NORMAL |
508 | | | | |
509 | rtpmap | The attribute value must | M | IDENTICAL-PER-PT |
510 | | be same for a given | | |
511 | | codec configuration | | |
512 | | | | |
513 | fmtp | The attribute value must | M | IDENTICAL-PER-PT |
514 | | be same for a given | | |
515 | | codec configuration | | |
516 | | | | |
517 | keywds | Not impacted | S | NORMAL |
518 | | | | |
519 | type | Not Impacted | S | NORMAL |
520 | | | | |
521 | tool | Not Impacted | S | NORMAL |
522 | | | | |
523 | charset | Not Impacted | S | NORMAL |
524 | | | | |
525 | sdplang | Not Impacted | B | NORMAL |
526 | | | | |
527 | lang | Not Impacted | B | NORMAL |
528 | | | | |
529 +------------+--------------------------+-------+-------------------+
531 RFC4566 Attribute Analysis
533 5.2. RFC4585 - RTP/AVPF
535 RFC4585 [RFC4585] defines an extension to the Audio-visual Profile
536 (AVP) that enables receivers to provide, statistically, more
537 immediate feedback to the senders and thus allows for short-term
538 adaptation and efficient feedback-based repair mechanisms to be
539 implemented.
541 +----------+-------------------------------------+-------+----------+
542 | Attr | Notes | Level | Category |
543 | Name | | | |
544 +----------+-------------------------------------+-------+----------+
545 | rtcp-fb | The combination of a particular | M | NORMAL |
546 | | Payload Type along with the m=line | | |
547 | | identify the scope and | | |
548 | | applicability of a given RTCP | | |
549 | | feedback to a particular RTP | | |
550 | | Stream. | | |
551 | | | | |
552 +----------+-------------------------------------+-------+----------+
554 RFC4585 Attribute Analysis
556 Since RTCP feedback attributes are Payload Type (PT) scoped, the
557 usage of identical Payload Type values across multiplexed m=lines is
558 described in [I-D.ietf-mmusic-sdp-bundle-negotiation].
560 5.3. RFC5761 - Multiplexing RTP and RTCP
562 RFC5761 [RFC5761] discusses issues that arise when multiplexing RTP
563 data packets and RTP Control Protocol (RTCP) packets on a single UDP
564 port. It describes when such multiplexing is and is not appropriate,
565 and it explains how the Session Description Protocol (SDP) can be
566 used to signal multiplexed sessions.
568 +-----------+----------------------------------+-------+------------+
569 | Name | Notes | Level | Category |
570 +-----------+----------------------------------+-------+------------+
571 | rtcp-mux | RTP and RTCP Multiplexing affect | M | IDENTICAL |
572 | | the entire RTP Session | | |
573 | | | | |
574 +-----------+----------------------------------+-------+------------+
576 RFC5761 Attribute Analysis
578 5.4. RFC4574 - SDP Label Attribute
580 RFC4574 [RFC4574] defines a new Session Description Protocol (SDP)
581 media-level attribute: "label". The "label" attribute carries a
582 pointer to a media stream in the context of an arbitrary network
583 application that uses SDP. The sender of the SDP document can attach
584 the "label" attribute to a particular media stream or streams. The
585 application can then use the provided pointer to refer to each
586 particular media stream in its context.
588 +--------+---------------+-------+----------+
589 | Name | Notes | Level | Category |
590 +--------+---------------+-------+----------+
591 | label | Not Impacted | M | NORMAL |
592 | | | | |
593 +--------+---------------+-------+----------+
595 RFC4574 Attribute Analysis
597 5.5. RFC5432 - QoS Mechanism Selection in SDP
599 RFC5432 [RFC5432] defines procedures to negotiate QOS mechanisms
600 using the Session Description Protocol (SDP) offer/answer model.
602 +----------------+-------------------------------+-------+----------+
603 | Name | Notes | Level | Category |
604 +----------------+-------------------------------+-------+----------+
605 | qos-mech-send | A single DSCP code point per | B | NORMAL |
606 | | flow being multiplexed | | |
607 | | doesn't impact multiplexing | | |
608 | | since QOS mechanisms are | | |
609 | | signaled/scoped per flow. | | |
610 | | | | |
611 | qos-mech-recv | A single DSCP code point per | B | NORMAL |
612 | | flow being multiplexed | | |
613 | | doesn't impact multiplexing | | |
614 | | since QOS mechanisms are | | |
615 | | signaled/scoped per flow. | | |
616 | | | | |
617 +----------------+-------------------------------+-------+----------+
619 RFC5432 Attribute Analysis
621 Multiplexing consideration when multiple DSCP code points are defined
622 per flow can be found in Section 14
624 5.6. RFC4568 - SDP Security Descriptions
626 RFC4568 [RFC4568] defines a Session Description Protocol (SDP)
627 cryptographic attribute for unicast media streams. The attribute
628 describes a cryptographic key and other parameters that serve to
629 configure security for a unicast media stream in either a single
630 message or a roundtrip exchange.
632 +--------+---------------------------------------+-------+----------+
633 | Name | Notes | Level | Category |
634 +--------+---------------------------------------+-------+----------+
635 | crypto | Refer to section 6.2.5 of [I-D.ietf-m | M | SPECIAL |
636 | | music-sdp-bundle-negotiation] | | |
637 | | | | |
638 +--------+---------------------------------------+-------+----------+
640 RFC4568 Attribute Analysis
642 If the multiplexing scheme cannot ensure unique SSRCs across all the
643 media lines, multiplexing MUST NOT be performed.
645 5.7. RFC5762 - RTP over DCCP
647 The Real-time Transport Protocol (RTP) is a widely used transport for
648 real-time multimedia on IP networks. The Datagram Congestion Control
649 Protocol (DCCP) is a transport protocol that provides desirable
650 services for real-time applications. RFC5762 [RFC5762] specifies a
651 mapping of RTP onto DCCP, along with associated signaling, such that
652 real-time applications can make use of the services provided by DCCP
654 +--------------------+---------------------+---------+--------------+
655 | Name | Notes | Current | Category |
656 +--------------------+---------------------+---------+--------------+
657 | dccp-service-code | If RFC6773 is not | M | NOT |
658 | | being used in | | RECOMMENDED |
659 | | addition to | | |
660 | | RFC5762, the port | | |
661 | | in the m= line is a | | |
662 | | DCCP port. DCCP | | |
663 | | being a connection | | |
664 | | oriented protocol, | | |
665 | | does not allow | | |
666 | | multiple | | |
667 | | connections on the | | |
668 | | same 5-tuple. | | |
669 | | | | |
670 +--------------------+---------------------+---------+--------------+
672 RFC5762 Attribute Analysis
674 If RFC6773 is being used in addition to RFC5762 and provided that
675 DCCP-in-UDP layer has additional demultiplexing, then it may be
676 possible to use different DCCP service codes for each DCCP flow,
677 given each uses a different DCCP port. Although doing so might
678 conflict with the media type of the m= line. None of this is
679 standardized yet and it wouldn't work as explained. Hence
680 multiplexing MUST NOT be performed even in this alternate scenario.
682 5.8. RFC6773 - DCCP-UDP Encapsulation
684 RFC6773 [RFC6773] document specifies an alternative encapsulation of
685 the Datagram Congestion Control Protocol (DCCP), referred to as DCCP-
686 UDP. This encapsulation allows DCCP to be carried through the
687 current generation of Network Address Translation (NAT) middle boxes
688 without modification of those middle boxes
689 +------------+-------------------------------+-------+--------------+
690 | Name | Notes | Level | Category |
691 +------------+-------------------------------+-------+--------------+
692 | dccp-port | Multiplexing MUST NOT be | M | NOT |
693 | | performed due to potential | | RECOMMENDED |
694 | | conflict between the port | | |
695 | | used for DCCP | | |
696 | | en/decapsulation and the RTP. | | |
697 | | | | |
698 +------------+-------------------------------+-------+--------------+
700 RFC6773 Attribute Analysis
702 Since RFC6773 is about tunnelling DCCP in UDP, with the UDP port
703 being the port of the DCCP en-/de-capsulation service. This
704 encapsulation allows arbitrary DCCP packets to be encapsulated and
705 the DCCP port choosen MAY conflict with the port chosen for the RTP
706 traffic.
708 For multiplexing several DCCP-in-UDP encapsulations on the same UDP
709 port, with no RTP traffic on the same port implies collapsing several
710 DCCP port spaces together. This MAY or MAY NOT work depending on the
711 nature of DCCP encapsulations and ports choses thus rendering it to
712 be very application dependant.
714 5.9. RFC5506 - Reduced-Size RTCP in RTP Profile
716 RFC5506 [RFC5506] discusses benefits and issues that arise when
717 allowing Real-time Transport Protocol (RTCP) packets to be
718 transmitted with reduced size.
720 +-------------+--------------------------------+-------+------------+
721 | Name | Notes | Level | Category |
722 +-------------+--------------------------------+-------+------------+
723 | rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL |
724 | | entire RTP Session | | |
725 | | | | |
726 +-------------+--------------------------------+-------+------------+
728 RFC5506 Attribute Analysis
730 5.10. RFC6787 - Media Resource Control Protocol Version 2
732 The Media Resource Control Protocol Version 2 (MRCPv2) allows client
733 hosts to control media service resources such as speech synthesizers,
734 recognizers, verifiers, and identifiers residing in servers on the
735 network. MRCPv2 is not a "stand-alone" protocol -- it relies on
736 other protocols, such as the Session Initiation Protocol (SIP), to
737 coordinate MRCPv2 clients and servers and manage sessions between
738 them, and the Session Description Protocol (SDP) to describe,
739 discover, and exchange capabilities. It also depends on SIP and SDP
740 to establish the media sessions and associated parameters between the
741 media source or sink and the media server. Once this is done, the
742 MRCPv2 exchange operates over the control session established above,
743 allowing the client to control the media processing resources on the
744 speech resource server. RFC6787 [RFC6787] defines attributes for
745 this purpose.
747 +-----------+---------------+-------+----------+
748 | Name | Notes | Level | Category |
749 +-----------+---------------+-------+----------+
750 | resource | Not Impacted | M | NORMAL |
751 | | | | |
752 | channel | Not Impacted | M | NORMAL |
753 | | | | |
754 +-----------+---------------+-------+----------+
756 RFC6787 Attribute Analysis
758 5.11. RFC5245 - Interactive Connectivity Establishment (ICE)
760 RFC5245 [RFC5245] describes a protocol for Network Address
761 Translator(NAT) traversal for UDP-based multimedia sessions
762 established with the offer/answer model. This protocol is called
763 Interactive Connectivity Establishment (ICE). ICE makes use of the
764 Session Traversal Utilities for NAT (STUN) protocol and its
765 extension,Traversal Using Relay NAT (TURN). ICE can be used by any
766 protocol utilizing the offer/answer model, such as the Session
767 Initiation Protocol (SIP).
769 +--------------------+-------------------------+-------+------------+
770 | Name | Notes | Level | Category |
771 +--------------------+-------------------------+-------+------------+
772 | ice-lite | Not Impacted | S | NORMAL |
773 | | | | |
774 | ice-options | Not Impacted | S | NORMAL |
775 | | | | |
776 | ice-pwd | ice-pwd MUST be the one | B | TRANSPORT |
777 | | that corresponds to the | | |
778 | | m=line chosen for | | |
779 | | setting up the | | |
780 | | underlying transport | | |
781 | | flow | | |
782 | | | | |
783 | ice-ufrag | ice-ufrag MUST be the | B | TRANSPORT |
784 | | one that corresponds to | | |
785 | | the m=line chosen for | | |
786 | | setting up the | | |
787 | | underlying transport | | |
788 | | flow | | |
789 | | | | |
790 | candidate | ice candidate MUST be | M | TRANSPORT |
791 | | the one that | | |
792 | | corresponds to the | | |
793 | | m=line chosen for | | |
794 | | setting up the | | |
795 | | underlying transport | | |
796 | | flow | | |
797 | | | | |
798 | remote-candidates | ice remote candidate | M | TRANSPORT |
799 | | MUST be the one that | | |
800 | | corresponds to the | | |
801 | | m=line chosen for | | |
802 | | setting up the | | |
803 | | underlying transport | | |
804 | | flow | | |
805 | | | | |
806 +--------------------+-------------------------+-------+------------+
808 RFC5245 Attribute Analysis
810 5.12. RFC5285 - RTP Header Extensions
812 RFC5285 [RFC5285] provides a general mechanism to use the header
813 extension feature of RTP (the Real-Time Transport Protocol). It
814 provides the option to use a small number of small extensions in each
815 RTP packet, where the universe of possible extensions is large and
816 registration is de-centralized. The actual extensions in use in a
817 session are signaled in the setup information for that session.
819 +---------+--------------------------------------+-------+----------+
820 | Name | Notes | Level | Category |
821 +---------+--------------------------------------+-------+----------+
822 | extmap | Specific RTP extension document MUST | B | SPECIAL |
823 | | be referred | | |
824 | | | | |
825 +---------+--------------------------------------+-------+----------+
827 RFC5285 Attribute Analysis
829 5.13. RFC3605 - RTCP attribute in SDP
831 Originally, SDP assumed that RTP and RTCP were carried on consecutive
832 ports. However, this is not always true when NATs are involved.
833 [RFC3605] specifies an early mechanism to indicate the RTCP port.
835 +-------+--------------------------------------+-------+------------+
836 | Name | Notes | Level | Category |
837 +-------+--------------------------------------+-------+------------+
838 | rtcp | Identical attribute value MUST be | M | IDENTICAL |
839 | | used since the RTCP port affects the | | |
840 | | entire RTP session. | | |
841 | | | | |
842 +-------+--------------------------------------+-------+------------+
844 RFC3605 Attribute Analysis
846 5.14. RFC5576 - Source-Specific SDP Attributes
848 RFC5576 [RFC5576] defines a mechanism to describe RTP media sources,
849 which are identified by their synchronization source (SSRC)
850 identifiers, in SDP, to associate attributes with these sources, and
851 to express relationships among sources. It also defines several
852 source-level attributes that can be used to describe properties of
853 media sources.
855 +----------------+----------------------+-------+-------------------+
856 | Name | Notes | Level | Category |
857 +----------------+----------------------+-------+-------------------+
858 | ssrc | Refer to Notes below | M | NORMAL |
859 | | | | |
860 | ssrc-group | Refer to section | M | SPECIAL |
861 | | Section 9 for | | |
862 | | specific analysis of | | |
863 | | the grouping | | |
864 | | semantics | | |
865 | | | | |
866 | cname | Not Impacted [Open | SR | NORMAL |
867 | | Issues: what are the | | |
868 | | rules for CNAME | | |
869 | | duplication across | | |
870 | | sessions?] | | |
871 | | | | |
872 | previous-ssrc | Refer to notes below | SR | NORMAL |
873 | | | | |
874 | fmtp | The attribute value | SR | IDENTICAL-PER-PT |
875 | | must be same for a | | |
876 | | given codec | | |
877 | | configuration | | |
878 | | | | |
879 +----------------+----------------------+-------+-------------------+
881 RFC5576 Attribute Analysis
883 If SSRCs are repeated across m=lines being multiplexed, they MUST all
884 represent the same underlying RTP Source. For more details on
885 implications of SSRC values with in the context of multiplexing
886 please refer to [I-D.ietf-mmusic-sdp-bundle-negotiation]
888 5.15. RFC6236 - Image Attributes in SDP
890 RFC6236 [RFC6236] proposes a new generic session setup attribute to
891 make it possible to negotiate different image attributes such as
892 image size. A possible use case is to make it possible for a low-end
893 hand-held terminal to display video without the need to rescale the
894 image,something that may consume large amounts of memory and
895 processing power. The document also helps to maintain an optimal
896 bitrate for video as only the image size that is desired by the
897 receiver is transmitted.
899 +------------+--------------------------+-------+-------------------+
900 | Name | Notes | Level | Category |
901 +------------+--------------------------+-------+-------------------+
902 | imageattr | The attribute value must | M | IDENTICAL-PER-PT |
903 | | be same for a given | | |
904 | | codec configuration | | |
905 | | | | |
906 +------------+--------------------------+-------+-------------------+
908 RFC6236 Attribute Analysis
910 5.16. RFC6285 - Rapid Acquisition of Multicast RTP Sessions
912 RFC6285 [RFC6285] describes a method using the existing RTP and RTP
913 Control Protocol (RTCP) machinery that reduces the acquisition delay.
914 In this method, an auxiliary unicast RTP session carrying the
915 Reference Information to the receiver precedes or accompanies the
916 multicast stream. This unicast RTP flow can be transmitted at a
917 faster than natural bitrate to further accelerate the acquisition.
918 The motivating use case for this capability is multicast applications
919 that carry real-time compressed audio and video.
921 +---------------+-------------------+-------+------------------+
922 | Name | Notes | Level | Category |
923 +---------------+-------------------+-------+------------------+
924 | rams-updates | Not recommended | M | NOT RECOMMENDED |
925 | | | | |
926 +---------------+-------------------+-------+------------------+
928 RFC6285 Attribute Analysis
930 5.17. RFC6230 - Media Control Channel Framework
932 RFC6230 [RFC6230] describes a framework and protocol for application
933 deployment where the application programming logic and media
934 processing are distributed. This implies that application
935 programming logic can seamlessly gain access to appropriate resources
936 that are not co-located on the same physical network entity. The
937 framework uses the Session Initiation Protocol (SIP) to establish an
938 application-level control mechanism between application servers and
939 associated external servers such as media servers.
941 +---------+-----------------+-------+----------+
942 | Name | Notes | Level | Category |
943 +---------+-----------------+-------+----------+
944 | cfw-id | Not Applicable | M | NORMAL |
945 | | | | |
946 +---------+-----------------+-------+----------+
948 RFC6230 Attribute Analysis
950 5.18. RFC6364 - SDP Elements for FEC Framework
952 RFC6364 [RFC6364] specifies the use of the Session Description
953 Protocol (SDP) to describe the parameters required to signal the
954 Forward Error Correction (FEC) Framework Configuration Information
955 between the sender(s) and receiver(s). This document also provides
956 examples that show the semantics for grouping multiple source and
957 repair flows together for the applications that simultaneously use
958 multiple instances of the FEC Framework.
960 +------------------+-------+-------+----------+
961 | Name | Notes | Level | Category |
962 +------------------+-------+-------+----------+
963 | fec-source-flow | | M | SPECIAL |
964 | | | | |
965 | fec-repair-flow | | M | SPECIA: |
966 | | | | |
967 | repair-window | | M | SPECIAL |
968 | | | | |
969 +------------------+-------+-------+----------+
971 RFC6364 Attribute Analysis
973 5.19. RFC4796 - Content Attribute
975 RFC4796 [RFC4796] defines a new Session Description Protocol (SDP)
976 media-level attribute, 'content'. The 'content' attribute defines
977 the content of the media stream to a more detailed level than the
978 media description line. The sender of an SDP session description can
979 attach the 'content' attribute to one or more media streams. The
980 receiving application can then treat each media stream differently
981 (e.g., show it on a big or small screen) based on its content.
983 +----------+---------------+-------+----------+
984 | Name | Notes | Level | Category |
985 +----------+---------------+-------+----------+
986 | content | Not Impacted | M | NORMAL |
987 | | | | |
988 +----------+---------------+-------+----------+
990 RFC4796 Attribute Analysis
992 5.20. RFC3407 - SDP Simple Capability Declaration
994 RFC3407 [RFC3407] defines a set of Session Description Protocol (SDP)
995 attributes that enables SDP to provide a minimal and backwards
996 compatible capability declaration mechanism.
998 +----------+------------------------+-------+----------+
999 | Name | Notes | Level | Category |
1000 +----------+------------------------+-------+----------+
1001 | sqn | Not Impacted | B | NORMAL |
1002 | | | | |
1003 | cdsc | Not Impacted. | B | NORMAL |
1004 | | | | |
1005 | cpar | Refer to Section 15 | B | INHERIT |
1006 | | | | |
1007 | cparmin | Refer to notes below | B | SPECIAL |
1008 | | | | |
1009 | cparmax | Refer to notes below | B | SPECIAL |
1010 | | | | |
1011 +----------+------------------------+-------+----------+
1013 RFC3407 Attribute Analysis
1015 Since the attributes (a=cparmin and a=cparmax) defines minimum and
1016 maximum numerical values associated with the attributed described in
1017 a=cpar, it is recommended to consult the document defining the
1018 attribute for dealing under media stream multiplexing.
1020 5.21. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions
1022 RFC6284 [RFC6284] presents a port mapping solution that allows RTP
1023 receivers to choose their own ports for an auxiliary unicast session
1024 in RTP applications using both unicast and multicast services. The
1025 solution provides protection against denial-of-service or packet
1026 amplification attacks that could be used to cause one or more RTP
1027 packets to be sent to a victim client
1028 +------------------+-------------------------+-------+--------------+
1029 | Name | Notes | Level | Category |
1030 +------------------+-------------------------+-------+--------------+
1031 | portmapping-req | Not recommended, if | M | NOT |
1032 | | port mapping is | | RECOMMENDED |
1033 | | required by the | | |
1034 | | application | | |
1035 | | | | |
1036 +------------------+-------------------------+-------+--------------+
1038 RFC6284 Attribute Analysis
1040 5.22. RFC6714 - MSRP-CEMA
1042 RFC6714 [RFC6714] defines a Message Session Relay Protocol (MSRP)
1043 extension, Connection Establishment for Media Anchoring (CEMA).
1044 Support of this extension is OPTIONAL. The extension allows middle
1045 boxes to anchor the MSRP connection, without the need for middle
1046 boxes to modify the MSRP messages; thus, it also enables secure end-
1047 to-end MSRP communication in networks where such middle boxes are
1048 deployed. This document also defines a Session Description Protocol
1049 (SDP) attribute, 'msrp-cema', that MSRP endpoints use to indicate
1050 support of the CEMA extension.
1052 +------------+---------------+-------+----------+
1053 | Name | Notes | Level | Category |
1054 +------------+---------------+-------+----------+
1055 | msrp-cema | Not Impacted | M | NORMAL |
1056 | | | | |
1057 +------------+---------------+-------+----------+
1059 RFC6714 Attribute Analysis
1061 5.23. RFC4583 - SDP Format for BFCP Streams
1063 RFC4583 [RFC4583] document specifies how to describe Binary Floor
1064 Control Protocol (BFCP) streams in Session Description Protocol (SDP)
1065 descriptions. User agents using the offer/answer model to establish
1066 BFCP streams use this format in their offers and answers
1067 +------------+---------------------------------+-------+------------+
1068 | Name | Notes | Level | Category |
1069 +------------+---------------------------------+-------+------------+
1070 | floorctrl | Must be repeated across all the | M | IDENTICAL |
1071 | | multiplexed m=lines | | |
1072 | | | | |
1073 | confid | Not Impacted | M | NORMAL |
1074 | | | | |
1075 | userid | Not Impacted | M | NORMAL |
1076 | | | | |
1077 | floorid | The floorid MUST be globally | M | NORMAL |
1078 | | unique | | |
1079 | | | | |
1080 +------------+---------------------------------+-------+------------+
1082 RFC4583 Attribute Analysis
1084 5.24. RFC5547 - SDP Offer/Answer for File Transfer
1086 RFC5547 [RFC5547] provides a mechanism to negotiate the transfer of
1087 one or more files between two endpoints by using the Session
1088 Description Protocol (SDP) offer/answer model specified in [RFC3264].
1090 +----------------------+---------------+-------+----------+
1091 | Name | Notes | Level | Category |
1092 +----------------------+---------------+-------+----------+
1093 | file-selector | Not Impacted | M | NORMAL |
1094 | | | | |
1095 | file-transfer-id | Not Impacted | M | NORMAL |
1096 | | | | |
1097 | file-disposition | Not Impacted | M | NORMAL |
1098 | | | | |
1099 | file-date | Not Impacted | M | NORMAL |
1100 | | | | |
1101 | file-iconfile-range | Not Impacted | M | NORMAL |
1102 | | | | |
1103 +----------------------+---------------+-------+----------+
1105 RFC5547 Attribute Analysis
1107 5.25. RFC6489 - SDP and RTP Media Loopback Extension
1109 [MEDIA_LOOPBACK] adds new SDP media types and attributes, which
1110 enable establishment of media sessions where the media is looped back
1111 to the transmitter. Such media sessions will serve as monitoring and
1112 troubleshooting tools by providing the means for measurement of more
1113 advanced VoIP, Real-time Text and Video over IP performance metrics.
1115 +------------------------------+----------------+-------+----------+
1116 | Name | Notes | Level | Category |
1117 +------------------------------+----------------+-------+----------+
1118 | loopback rtp-pkt-loopback | Not Impacted | M | NORMAL |
1119 | | | | |
1120 | loopback rtp-media-loopback | Not Impacted | M | NORMAL |
1121 | | | | |
1122 | loopback-source | Not Impacted | M | NORMAL |
1123 | | | | |
1124 | loopback-mirror | Not Impacted | M | NORMAL |
1125 | | | | |
1126 +------------------------------+----------------+-------+----------+
1128 An Extension to the Session Description Protocol (SDP) and Real-time
1129 Transport Protocol (RTP) for Media Loopback
1131 5.26. RFC5760 - RTCP with Unicast Feedback
1133 RFC5760 [RFC5760] specifies an extension to the Real-time Transport
1134 Control Protocol (RTCP) to use unicast feedback to a multicast
1135 sender. The proposed extension is useful for single-source multicast
1136 sessions such as Source-Specific Multicast (SSM) communication where
1137 the traditional model of many-to-many group communication is either
1138 not available or not desired.
1140 +---------------+------------------------------+-------+------------+
1141 | Name | Notes | Level | Category |
1142 +---------------+------------------------------+-------+------------+
1143 | rtcp-unicast | The attribute MUST be | M | IDENTICAL |
1144 | | reported across all m=lines | | |
1145 | | multiplexed | | |
1146 | | | | |
1147 +---------------+------------------------------+-------+------------+
1149 RFC5760 Attribute Analysis
1151 5.27. RFC3611 - RTCP XR
1153 RFC3611 [RFC3611] defines the Extended Report (XR) packet type for
1154 the RTP Control Protocol (RTCP), and defines how the use of XR
1155 packets can be signaled by an application if it employs the Session
1156 Description Protocol (SDP).
1158 +----------+---------------+-------+----------+
1159 | Name | Notes | Level | Category |
1160 +----------+---------------+-------+----------+
1161 | rtcp-xr | Not Impacted | B | NORMAL |
1162 | | | | |
1163 +----------+---------------+-------+----------+
1165 RFC3611 Attribute Analysis
1167 5.28. RFC5939 - SDP Capability Negotiation
1169 RFC5939 [RFC5939] defines a general SDP Capability Negotiation
1170 framework. It also specifies how to provide attributes and transport
1171 protocols as capabilities and negotiate them using the framework.
1172 Extensions for other types of capabilities (e.g., media types and
1173 media formats) may be provided in other documents.
1175 +-------+-------------------------------+-------+----------+
1176 | Name | Notes | Level | Category |
1177 +-------+-------------------------------+-------+----------+
1178 | pcfg | Refer to section Section 15 | M | INHERIT |
1179 | | | | |
1180 | acfg | Refer to section Section 15 | M | INHERIT |
1181 | | | | |
1182 | csup | Not Impacted | B | NORMAL |
1183 | | | | |
1184 | creq | Not Impacted | B | NORMAL |
1185 | | | | |
1186 | acap | Refer to section Section 15 | B | INHERIT |
1187 | | | | |
1188 | tcap | Refer to section Section 15 | B | INHERIT |
1189 | | | | |
1190 +-------+-------------------------------+-------+----------+
1192 RFC5939 Attribute Analysis
1194 5.29. RFC6871- SDP Media Capabilities Negotiation
1196 Session Description Protocol (SDP) capability negotiation provides a
1197 general framework for indicating and negotiating capabilities in SDP.
1198 The base framework defines only capabilities for negotiating
1199 transport protocols and attributes. [RFC6871] extends the framework
1200 by defining media capabilities that can be used to negotiate media
1201 types and their associated parameters.
1203 +---------+------------------------------+-------+----------+
1204 | Name | Notes | Level | Category |
1205 +---------+------------------------------+-------+----------+
1206 | rmcap | Refer to section Section 15 | B | INHERIT |
1207 | | | | |
1208 | omcap | Refer to section Section 15 | B | INHERIT |
1209 | | | | |
1210 | mfcap | Refer to section Section 15 | B | INHERIT |
1211 | | | | |
1212 | mscap | Refer to section Section 15 | B | INHERIT |
1213 | | | | |
1214 | lcfg | Not Impacted | B | NORMAL |
1215 | | | | |
1216 | sescap | Refer to section Section 15 | S | INHERIT |
1217 | | | | |
1218 +---------+------------------------------+-------+----------+
1220 Session Description Protocol (SDP) Media Capabilities Negotiation
1222 5.30. RFC4567 - Key Management Extensions for SDP and RTSP
1224 RFC4567 [RFC4567] defines general extensions for Session Description
1225 Protocol (SDP) and Real Time Streaming Protocol (RTSP) to carry
1226 messages, as specified by a key management protocol, in order to
1227 secure the media. These extensions are presented as a framework, to
1228 be used by one or more key management protocols. As such, their use
1229 is meaningful only when complemented by an appropriate key management
1230 protocol.
1232 +-----------+----------------------------------+-------+------------+
1233 | Name | Notes | Level | Category |
1234 +-----------+----------------------------------+-------+------------+
1235 | key-mgmt | Key management protocol MUST be | B | IDENTICAL |
1236 | | identical across all the m=lines | | |
1237 | | | | |
1238 +-----------+----------------------------------+-------+------------+
1240 RFC4567 Attribute Analysis
1242 5.31. RFC4572 - Comedia over TLS in SDP
1244 RFC4572 [RFC4572] specifies how to establish secure connection-
1245 oriented media transport sessions over the Transport Layer Security
1246 (TLS) protocol using the Session Description Protocol (SDP). It
1247 defines a new SDP protocol identifier, 'TCP/TLS'. It also defines
1248 the syntax and semantics for an SDP 'fingerprint' attribute that
1249 identifies the certificate that will be presented for the TLS
1250 session. This mechanism allows media transport over TLS connections
1251 to be established securely, so long as the integrity of session
1252 descriptions is assured.
1254 +--------------+-------------------------------+-------+------------+
1255 | Name | Notes | Level | Category |
1256 +--------------+-------------------------------+-------+------------+
1257 | fingerprint | Fingerprint value from the | B | TRANSPORT |
1258 | | m=line defining the | | |
1259 | | underlying transport is | | |
1260 | | chosen | | |
1261 | | | | |
1262 +--------------+-------------------------------+-------+------------+
1264 RFC4572 Attribute Analysis
1266 5.32. RFC4570 - SDP Source Filters
1268 RFC4570 [RFC4570] describes how to adapt the Session Description
1269 Protocol (SDP) to express one or more source addresses as a source
1270 filter for one or more destination "connection" addresses. It
1271 defines the syntax and semantics for an SDP "source-filter" attribute
1272 that may reference either IPv4 or IPv6 address(es) as either an
1273 inclusive or exclusive source list for either multicast or unicast
1274 destinations. In particular, an inclusive source-filter can be used
1275 to specify a Source-Specific Multicast (SSM) session
1277 +----------------+-----------------------------+-------+------------+
1278 | Name | Notes | Level | Category |
1279 +----------------+-----------------------------+-------+------------+
1280 | source-filter | The attribute MUST be | B | IDENTICAL |
1281 | | repeated across all m=lines | | |
1282 | | multiplexed | | |
1283 | | | | |
1284 +----------------+-----------------------------+-------+------------+
1286 RFC4570 Attribute Analysis
1288 5.33. RFC6128 - RTCP Port for Multicast Sessions
1290 The Session Description Protocol (SDP) has an attribute that allows
1291 RTP applications to specify an address and a port associated with the
1292 RTP Control Protocol (RTCP) traffic. In RTP-based source-specific
1293 multicast (SSM) sessions, the same attribute is used to designate the
1294 address and the RTCP port of the Feedback Target in the SDP
1295 description. However, the RTCP port associated with the SSM session
1296 itself cannot be specified by the same attribute to avoid ambiguity,
1297 and thus, is required to be derived from the "m=" line of the media
1298 description. Deriving the RTCP port from the "m=" line imposes an
1299 unnecessary restriction. RFC6128 [RFC6128] removes this restriction
1300 by introducing a new SDP attribute.
1302 +-----------------+----------------------------+-------+------------+
1303 | Name | Notes | Level | Category |
1304 +-----------------+----------------------------+-------+------------+
1305 | multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL |
1306 | | be identical across all | | |
1307 | | the m=lines | | |
1308 | | | | |
1309 +-----------------+----------------------------+-------+------------+
1311 RFC6128 Attribute Analysis
1313 5.34. RFC6189 - ZRTP
1315 RFC6189 [RFC6189] defines ZRTP, a protocol for media path Diffie-
1316 Hellman exchange to agree on a session key and parameters for
1317 establishing unicast Secure Real-time Transport Protocol (SRTP)
1318 sessions for Voice over IP (VoIP) applications.
1320 +------------+-------------------------------+-------+--------------+
1321 | Name | Notes | Level | Category |
1322 +------------+-------------------------------+-------+--------------+
1323 | zrtp-hash | Complicates if all the | M | NOT |
1324 | | m=lines are not authenticated | | RECOMMENDED |
1325 | | as given in the example below | | |
1326 | | | | |
1327 +------------+-------------------------------+-------+--------------+
1329 RFC6189 Attribute Analysis
1331 Example: Multiplexing media descriptions having attribute zrtp-hash
1332 defined with the media descriptions lacking it, would either
1333 complicate the handling of multiplexed stream or fail multiplexing.
1335 v=0
1336 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
1337 s=
1338 c=IN IP4 client.biloxi.example.com
1339 t=0 0
1340 m=audio 3456 RTP/AVP 97
1341 a=rtpmap:97 iLBC/8000
1342
1343 a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
1344 df881ae642c371ba46df
1345
1346 m=video 34567 RTP/AVP 31
1347 a=rtpmap:31 H261/90000
1349 5.35. RFC4145 - Connection-Oriented Media
1351 RFC4145 [RFC4145] describes how to express media transport over TCP
1352 using the Session Description Protocol (SDP). It defines the SDP
1353 'TCP' protocol identifier, the SDP 'setup' attribute, which describes
1354 the connection setup procedure, and the SDP 'connection' attribute,
1355 which handles connection reestablishment.
1357 +-------------+--------------------------------+-------+------------+
1358 | Name | Notes | Level | Category |
1359 +-------------+--------------------------------+-------+------------+
1360 | setup | MUST be identical across all | B | IDENTICAL |
1361 | | m=lines | | |
1362 | | | | |
1363 | connection | MUST be identical across all | B | IDENTICAL |
1364 | | m=lines | | |
1365 | | | | |
1366 +-------------+--------------------------------+-------+------------+
1368 RFC4145 Attribute Analysis
1370 5.36. RFC5159 - OMA BCAST SDP Attributes
1372 RFC5159 [RFC5159] provides descriptions of Session Description
1373 Protocol (SDP) attributes used by the Open Mobile Alliance's
1374 Broadcast Service and Content Protection specification.
1376 +---------------------+---------------+-------+----------+
1377 | Name | Notes | Level | Category |
1378 +---------------------+---------------+-------+----------+
1379 | bcastversion | Not Impacted | S | NORMAL |
1380 | | | | |
1381 | stkmstream | Not Impacted | B | NORMAL |
1382 | | | | |
1383 | SRTPAuthentication | Not Impacted | M | NORMAL |
1384 | | | | |
1385 | SRTPROCTxRate | Not Impacted | M | NORMAL |
1386 | | | | |
1387 +---------------------+---------------+-------+----------+
1389 RFC5159 Attribute Analysis
1391 5.37. RFC6193 - Media Description for IKE in SDP
1393 RFC6193 [RFC6193] specifies how to establish a media session that
1394 represents a virtual private network using the Session Initiation
1395 Protocol for the purpose of on-demand media/application sharing
1396 between peers. It extends the protocol identifier of the Session
1397 Description Protocol (SDP) so that it can negotiate use of the
1398 Internet Key Exchange Protocol (IKE) for media sessions in the SDP
1399 offer/answer model.
1401 +-------------------+--------------------------+-------+------------+
1402 | Name | Notes | Level | Category |
1403 +-------------------+--------------------------+-------+------------+
1404 | ike-setup | Attribute MUST be | B | IDENTICAL |
1405 | | identical across all the | | |
1406 | | m=lines | | |
1407 | | | | |
1408 | psk-fingerprint | Attribute MUST be | B | IDENTICAL |
1409 | | identical across all the | | |
1410 | | m=lines | | |
1411 | | | | |
1412 | ike-esp | Attribute MUST be | B | IDENTICAL |
1413 | | identical across all the | | |
1414 | | m=lines | | |
1415 | | | | |
1416 | ike-esp-udpencap | Attribute MUST be | B | IDENTICAL |
1417 | | identical across all the | | |
1418 | | m=lines | | |
1419 | | | | |
1420 +-------------------+--------------------------+-------+------------+
1422 RFC6193 Attribute Analysis
1424 With the above SDP constraints, a session multiplexed with multiple
1425 m=lines will use only one IPSec association for all of the m= lines.
1427 5.38. RFC6064 - SDP and RTSP Extensions for 3GPP
1429 The Packet-switched Streaming Service (PSS) and the Multimedia
1430 Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session
1431 Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
1432 with some extensions. RFC6064 [RFC6064] provides information about
1433 these extensions and registers the RTSP and SDP extensions with IANA.
1435 +--------------------------+--------------+-------+-----------------+
1436 | Name | Notes | Level | Category |
1437 +--------------------------+--------------+-------+-----------------+
1438 | X-predecbufsize | Refer to | M | NOT RECOMMENDED |
1439 | | notes below | | |
1440 | | | | |
1441 | X-initpredecbufperiod | Refer to | M | NOT RECOMMENDED |
1442 | | notes below | | |
1443 | | | | |
1444 | X-initpostdecbufperiod | Refer to | M | NOT RECOMMENDED |
1445 | | notes below | | |
1446 | | | | |
1447 | X-decbyterate | Refer to | M | NOT RECOMMENDED |
1448 | | notes below | | |
1449 | | | | |
1450 | 3gpp-videopostdecbufsize | Refer to | M | NOT RECOMMENDED |
1451 | | notes below | | |
1452 | | | | |
1453 | framesize | The | M | IDENTICAL-PER- |
1454 | | attribute | | PT |
1455 | | value must | | |
1456 | | be same for | | |
1457 | | a given | | |
1458 | | codec config | | |
1459 | | uration | | |
1460 | | | | |
1461 | 3GPP-Integrity-Key | Refer to | S | NOT RECOMMENDED |
1462 | | notes below | | |
1463 | | | | |
1464 | 3GPP-SRTP-Config | Refer to | M | NOT RECOMMENDED |
1465 | | notes below | | |
1466 | | | | |
1467 | alt,alt-default-id | Refer to | M | NOT RECOMMENDED |
1468 | | notes below | | |
1469 | | | | |
1470 | alt-group | Refer to | M | NOT RECOMMENDED |
1471 | | notes below | | |
1472 | | | | |
1473 | 3GPP-Adaptation-Support | Refer to | M | NOT RECOMMENDED |
1474 | | notes below | | |
1475 | | | | |
1476 | 3GPP-Asset-Informatio | Refer to | B | NOT RECOMMENDED |
1477 | | notes below | | |
1478 | | | | |
1479 | mbms-mode | Refer to | B | NOT RECOMMENDED |
1480 | | notes below | | |
1481 | | | | |
1482 | mbms-flowid | MRefer to | M | NOT RECOMMENDED |
1483 | | notes below | | |
1484 | | | | |
1485 | mbms-repair | Refer to | B | NOT RECOMMENDED |
1486 | | notes below | | |
1487 | | | | |
1488 | 3GPP-QoE- | Refer to | M | NOT RECOMMENDED |
1489 | Metrics:Corruption | notes below | | |
1490 | duration | | | |
1491 | | | | |
1492 | 3GPP-QoE- | Refer to | M | NOT RECOMMENDED |
1493 | Metrics:Rebuffering | notes below | | |
1494 | duration | | | |
1495 | | | | |
1496 | 3GPP-QoE-Metrics:Initial | Refer to | M | NOT RECOMMENDED |
1497 | buffering duration | notes below | | |
1498 | | | | |
1499 | 3GPP-QoE- | Refer to | M | NOT RECOMMENDED |
1500 | Metrics:Successive loss | notes below | | |
1501 | of RTP packets | | | |
1502 | | | | |
1503 | 3GPP-QoE-Metrics:Frame | Refer to | M | NOT RECOMMENDED |
1504 | rate deviation | notes below | | |
1505 | | | | |
1506 | 3GPP-QoE-Metrics:Jitter | Refer to | M | NOT RECOMMENDED |
1507 | duration | notes below | | |
1508 | | | | |
1509 | 3GPP-QoE-Metrics:Content | Refer to | B | NOT RECOMMENDED |
1510 | Switch Time | notes below | | |
1511 | | | | |
1512 | 3GPP-QoE-Metrics:Average | Refer to | M | NOT RECOMMENDED |
1513 | Codec Bitrat | notes below | | |
1514 | | | | |
1515 | 3GPP-QoE-Metrics:Codec | Refer to | M | NOT RECOMMENDED |
1516 | Information | notes below | | |
1517 | | | | |
1518 | 3GPP-QoE-Metrics:Buffer | Refer to | M | NOT RECOMMENDED |
1519 | Status | notes below | | |
1520 | | | | |
1521 +--------------------------+--------------+-------+-----------------+
1523 RFC6064 Attribute Analysis
1525 [RFC6064] defines SDP attributes that are applicable in the
1526 declarative usage of SDP alone. For purposes of this document, only
1527 the Offer/Answer usage of SDP is considered as mandated by
1528 [I-D.ietf-mmusic-sdp-bundle-negotiation].
1530 5.39. RFC3108 - ATM SDP
1532 RFC3108 [RFC3108] describes conventions for using the Session
1533 Description Protocol (SDP) described for controlling ATM Bearer
1534 Connections, and any associated ATM Adaptation Layer (AAL)
1536 +------------------------+--------------+-------+----------+
1537 | Name | Notes | Level | Category |
1538 +------------------------+--------------+-------+----------+
1539 | aalType | Not Impacted | B | NORMAL |
1540 | eecid | Not Impacted | B | NORMAL |
1541 | aalType | Not Impacted | B | NORMAL |
1542 | capability | Not Impacted | B | NORMAL |
1543 | qosClass | Not Impacted | B | NORMAL |
1544 | bcob | Not Impacted | B | NORMAL |
1545 | stc | Not Impacted | B | NORMAL |
1546 | upcc | Not Impacted | B | NORMAL |
1547 | atmQOSparms | Not Impacted | B | NORMAL |
1548 | atmTrfcDesc | Not Impacted | B | NORMAL |
1549 | abrParms | Not Impacted | B | NORMAL |
1550 | abrSetup | Not Impacted | B | NORMAL |
1551 | bearerType | Not Impacted | B | NORMAL |
1552 | lij | Not Impacted | B | NORMAL |
1553 | anycast | Not Impacted | B | NORMAL |
1554 | cache | Not Impacted | B | NORMAL |
1555 | bearerSigIE | Not Impacted | B | NORMAL |
1556 | aalApp | Not Impacted | B | NORMAL |
1557 | cbrRate | Not Impacted | B | NORMAL |
1558 | sbc | Not Impacted | B | NORMAL |
1559 | clkrec | Not Impacted | B | NORMAL |
1560 | fec | Not Impacted | B | NORMAL |
1561 | prtfl | Not Impacted | B | NORMAL |
1562 | structure | Not Impacted | B | NORMAL |
1563 | cpsSDUsize | Not Impacted | B | NORMAL |
1564 | aal2CPS | Not Impacted | B | NORMAL |
1565 | aal2CPSSDUrate | Not Impacted | B | NORMAL |
1566 | aal2sscs3661unassured | Not Impacted | B | NORMAL |
1567 | aal2sscs3661assured | Not Impacted | B | NORMAL |
1568 | aal2sscs3662 | Not Impacted | B | NORMAL |
1569 | aal5sscop | Not Impacted | B | NORMAL |
1570 | atmmap | Not Impacted | B | NORMAL |
1571 | silenceSupp | Not Impacted | B | NORMAL |
1572 | ecan | Not Impacted | B | NORMAL |
1573 | gc | Not Impacted | B | NORMAL |
1574 | profileDesc | Not Impacted | B | NORMAL |
1575 | vsel | Not Impacted | B | NORMAL |
1576 | dsel | Not Impacted | B | NORMAL |
1577 | fsel | Not Impacted | B | NORMAL |
1578 | onewaySel | Not Impacted | B | NORMAL |
1579 | codecconfig | Not Impacted | B | NORMAL |
1580 | isup_usi | Not Impacted | B | NORMAL |
1581 | isup_usi | Not Impacted | B | NORMAL |
1582 | chain | Not Impacted | B | NORMAL |
1583 | | | | |
1584 +------------------------+--------------+-------+----------+
1586 RFC3108 Attribute Analysis
1588 RFC3108 describes conventions for using the Session Description
1589 Protocol (SDP) for characterizing ATM bearer connections using an
1590 AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5,
1591 bearer connections can be used to transport single media streams. In
1592 addition, for AAL1 and AAL2, multiple media streams may be
1593 multiplexed into a bearer connection. For all adaptation types
1594 (AAL1, AAL2 and AAL5), bearer connections may be bundled into a
1595 single media group. In all cases addressed by RFC3108, a real-time
1596 media stream (voice, video, voiceband data, pseudo-wire and others)
1597 or a multiplex of media streams is mapped directly into an ATM
1598 connection. RFC3108 does not address cases where ATM serves as a
1599 low-level transport pipe for IP packets which in turn may carry one
1600 or more real-time (e.g. VoIP) media sessions with a life-cycle
1601 different from that of the underlying ATM transport.
1603 5.40. 3GPP TS 24.182
1605 3GPP TS 24.182 [R3GPPTS24.182] specifies IP multimedia subsystem
1606 Custom Alerting tones
1607 +-------------+----------------------------------+-------+----------+
1608 | Name | Notes | Level | Category |
1609 +-------------+----------------------------------+-------+----------+
1610 | g.3gpp.cat | Usage defined for the IP | M | NORMAL |
1611 | | Multimedia Subsystem | | |
1612 | | | | |
1613 +-------------+----------------------------------+-------+----------+
1615 3GPP TS 24.182 Attribute Analysis
1617 5.41. 3GPP TS 24.183
1619 3GPP TS 24.183 [R3GPPTS24.183]specifies IP multimedia subsystem
1620 Custom Ringing Signal
1622 +-------------+----------------------------------+-------+----------+
1623 | Name | Notes | Level | Category |
1624 +-------------+----------------------------------+-------+----------+
1625 | g.3gpp.crs | Usage defined for the IP | M | NORMAL |
1626 | | Multimedia Subsystem | | |
1627 | | | | |
1628 +-------------+----------------------------------+-------+----------+
1630 3GPP TS 24.183 Attribute Analysis
1632 5.42. 3GPP TS 24.229
1634 3GPP TS 24.229 [R3GPPTS24.229]IP multimedia call control protocol
1635 based on Session Initial protocol and Session Description Protocol.
1637 +------------------+---------------------------+-------+------------+
1638 | Name | Notes | Level | Category |
1639 +------------------+---------------------------+-------+------------+
1640 | secondary-realm | Per media-level attribute | M | TRANSPORT |
1641 | | MUST be used per | | |
1642 | | underlying transport | | |
1643 | | | | |
1644 | visited-realm | Per media-level attribute | M | TRANSPORT |
1645 | | MUST be used per | | |
1646 | | underlying transport | | |
1647 | | | | |
1648 | omr-m-cksum | Not Impacted | M | NORMAL |
1649 | | | | |
1650 | omr-s-cksum | Not Impacted | M | NORMAL |
1651 | | | | |
1652 | omr-m-att | Not Impacted | M | NORMAL |
1653 | | | | |
1654 | omr-s-bw | Not Impacted | M | NORMAL |
1655 | | | | |
1656 | omr-s-bw | Not Impacted | M | NORMAL |
1657 | | | | |
1658 | omr-m-att | Not Impacted | M | NORMAL |
1659 | | | | |
1660 | omr-codecs | Not Impacted | M | NORMAL |
1661 | | | | |
1662 +------------------+---------------------------+-------+------------+
1664 3GPP TS 24.229 Attribute Analysis
1666 5.43. ITU T.38
1668 ITU T.38[T.38] defines procedures for real-time Group 3 facsimile
1669 communications over IP networks.
1671 +------------------------+---------------+-------+----------+
1672 | Name | Notes | Level | Category |
1673 +------------------------+---------------+-------+----------+
1674 | T38FaxVersion | Not Impacted | S | NORMAL |
1675 | | | | |
1676 | T38MaxBitRate | Not Impacted | S | NORMAL |
1677 | | | | |
1678 | T38FaxFillBitRemoval | Not Impacted | S | NORMAL |
1679 | | | | |
1680 | T38FaxTranscodingMMR | Not Impacted | S | NORMAL |
1681 | | | | |
1682 | T38FaxTranscodingJBIG | Not Impacted | S | NORMAL |
1683 | | | | |
1684 | T38FaxRateManagement | Not Impacted | S | NORMAL |
1685 | | | | |
1686 | T38FaxMaxBuffer | Not Impacted | S | NORMAL |
1687 | | | | |
1688 | T38FaxMaxDatagram | Not Impacted | S | NORMAL |
1689 | | | | |
1690 | T38FaxUdpEC | Not Impacted | S | NORMAL |
1691 | | | | |
1692 +------------------------+---------------+-------+----------+
1694 Historic Attribute Analysis
1696 The ITU T.38 attributes are clearly unaffected by multiplexing and
1697 are specific to the working of the fax protocol itself.
1699 5.44. ITU-T H.248.15
1701 ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248
1702 package attribute
1703 +-----------+------------------------------------+-------+----------+
1704 | Name | Notes | Level | Category |
1705 +-----------+------------------------------------+-------+----------+
1706 | h248item | It is also only applicable for | B | SPECIAL |
1707 | | signaling the inclusion of H.248 | | |
1708 | | extension packages to a gateway | | |
1709 | | via the local and remote | | |
1710 | | descriptors. The attribute itself | | |
1711 | | is unaffected by multiplexing, but | | |
1712 | | the packaged referenced in a | | |
1713 | | specific use of the attribute may | | |
1714 | | be impacted. Further analysis of | | |
1715 | | each package is needed to | | |
1716 | | determine if there is an issue. | | |
1717 | | This is only a concern in | | |
1718 | | environments using a decomposed | | |
1719 | | server/gateway with H.248 signaled | | |
1720 | | between them. The ITU-T will need | | |
1721 | | to do further analysis of various | | |
1722 | | packages when they specify how to | | |
1723 | | signal the use of multiplexing to | | |
1724 | | a gateway. | | |
1725 | | | | |
1726 +-----------+------------------------------------+-------+----------+
1728 Historic Attribute Analysis
1730 5.45. RFC4975 - The Message Session Relay Protocol
1732 RFC4975 [RFC4975] the Message Session Relay Protocol, a protocol for
1733 transmitting a series of related instant messages in the context of a
1734 session. Message sessions are treated like any other media stream
1735 when set up via a rendezvous or session creation protocol such as the
1736 Session Initiation Protocol.
1738 +-----------------------+---------------+-------+----------+
1739 | Name | Notes | Level | Category |
1740 +-----------------------+---------------+-------+----------+
1741 | accept-types | Not Impacted | M | NORMAL |
1742 | | | | |
1743 | accept-wrapped-types | Not Impacted | M | NORMAL |
1744 | | | | |
1745 | max-size | Not Impacted | M | NORMAL |
1746 | | | | |
1747 | path | Not Impacted | M | NORMAL |
1748 | | | | |
1749 +-----------------------+---------------+-------+----------+
1751 RFC4975 Attribute Analysis
1753 5.46. Historical
1755 This section specifies analysis for the attributes that are included
1756 for historic usage alone by the [IANA].
1758 +---------------------+--------------+---------------+--------------+
1759 | Name | Notes | Level | Category |
1760 +---------------------+--------------+---------------+--------------+
1761 | rtpred1 | Historic | Not-Applcable | NOT |
1762 | | attributes. | | RECOMMENDED |
1763 | | | | |
1764 | rtpred2 | Historic | Not-Applcable | NOT |
1765 | | attributes. | | RECOMMENDED |
1766 | | | | |
1767 | PSCid | Not | Not-Applcable | TBD |
1768 | | Applicable | | |
1769 | | | | |
1770 | bc_service | Not | Not-Applcable | TBD |
1771 | | Applicable | | |
1772 | | | | |
1773 | bc_program | Not | Not-Applcable | TBD |
1774 | | Applicable | | |
1775 | | | | |
1776 | bc_service_package | Not | Not-Applcable | TBD |
1777 | | Applicable | | |
1778 | | | | |
1779 +---------------------+--------------+---------------+--------------+
1781 Unknowns Attribute Analysis
1783 6. bwtype Attribute Analysis
1785 This section specifies handling of specific bandwidth attributes when
1786 used in multiplexing scenarios.
1788 6.1. RFC4566 - SDP: Session Description Protocol
1790 +------------+-----------------------------------+-------+----------+
1791 | Name | Notes | Level | Category |
1792 +------------+-----------------------------------+-------+----------+
1793 | bwtype:CT | Aggregate bandwidth for the | S | NORMAL |
1794 | | conference | | |
1795 | | | | |
1796 | bwtype:AS | As a session attribute, it | B | NORMAL |
1797 | | specifies the session aggregate | | |
1798 | | unless media-level b=RR and/or | | |
1799 | | b=RS attributes are used. Under | | |
1800 | | this interpretation the | | |
1801 | | multiplexing scheme has no impact | | |
1802 | | and thus NORMAL category applies. | | |
1803 | | | | |
1804 | bwtype:AS | For the media level usage,the | B | SUM |
1805 | | aggregate of individual bandwidth | | |
1806 | | values is considered. | | |
1807 | | | | |
1808 +------------+-----------------------------------+-------+----------+
1810 RFC4566 bwtype Analysis
1812 6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth
1814 RFC3556 [RFC3556] defines an extension to the Session Description
1815 Protocol (SDP) to specify two additional modifiers for the bandwidth
1816 attribute. These modifiers may be used to specify the bandwidth
1817 allowed for RTP Control Protocol (RTCP) packets in a Real-time
1818 Transport Protocol (RTP) session
1819 +------------+--------------------------------+-------+-------------+
1820 | Name | Notes | Level | Category |
1821 +------------+--------------------------------+-------+-------------+
1822 | bwtype:RS | Session level usage represents | B | NORMAL,SUM |
1823 | | session aggregate and media | | |
1824 | | level usage indicates SUM of | | |
1825 | | the individual values while | | |
1826 | | multiplexing | | |
1827 | | | | |
1828 | bwtype:RR | Session level usage represents | B | NORMAL,SUM |
1829 | | session aggregate and media | | |
1830 | | level usage indicates SUM of | | |
1831 | | the individual values while | | |
1832 | | multiplexing | | |
1833 | | | | |
1834 +------------+--------------------------------+-------+-------------+
1836 RFC3556 bwtype Analysis
1838 6.3. RFC3890 - Bandwidth Modifier for SDP
1840 RFC3890 [RFC3890] defines a Session Description Protocol (SDP)
1841 Transport Independent Application Specific Maximum (TIAS) bandwidth
1842 modifier that does not include transport overhead; instead an
1843 additional packet rate attribute is defined. The transport
1844 independent bit-rate value together with the maximum packet rate can
1845 then be used to calculate the real bit-rate over the transport
1846 actually used.
1848 +--------------+---------------------------------+-------+----------+
1849 | Name | Notes | Level | Category |
1850 +--------------+---------------------------------+-------+----------+
1851 | bwtype:TIAS | The usage of TIAS is not | B | SPECIAL |
1852 | | clearly defined Offer/Answer | | |
1853 | | usage. | | |
1854 | | | | |
1855 | maxprate | The usage of TIAS and maxprate | B | SPECIAL |
1856 | | is not well defined under | | |
1857 | | multiplexing | | |
1858 | | | | |
1859 +--------------+---------------------------------+-------+----------+
1861 RFC3890 bwtype Analysis
1863 The intention of TIAS is that the media level bit-rate is multiplied
1864 with the known per-packet overhead for the selected transport and the
1865 maxprate value to determine the worst case bit-rate from the
1866 transport to more accurately capture the required usage. Summing
1867 TIAS values independently across m=lines and multiplying the computed
1868 sum with maxprate and the per-packet overhead would inflate the value
1869 significantly. Instead performing multiplication and adding the
1870 individual values is a more appropriate usage. This still ignores
1871 the fact that this is a send side declaration, and not intended for
1872 receiver negotiation.
1874 7. rtcp-fb Attribute Analysis
1876 This section analyzes rtcp-fb SDP attributes [RTCP-FB].
1878 7.1. RFC4585 - RTP/AVPF
1880 RFC4585 [RFC4585] defines an extension to the Audio-visual Profile
1881 (AVP) that enables receivers to provide, statistically, more
1882 immediate feedback to the senders and thus allows for short-term
1883 adaptation and efficient feedback-based repair mechanisms to be
1884 implemented.
1886 +----------+-----------------------------------+-------+------------+
1887 | Attr | Notes | Level | Category |
1888 | Name | | | |
1889 +----------+-----------------------------------+-------+------------+
1890 | ack rpsi | Not Impacted | M | NORMAL |
1891 | | | | |
1892 | ack app | Feedback parameters MUST be | M | SPECIAL |
1893 | | handled in the app specific way | | |
1894 | | when multiplexed | | |
1895 | | | | |
1896 | nack | Not Impacted | M | NORMAL |
1897 | | | | |
1898 | nack pli | Not Impacted | M | NORMAL |
1899 | | | | |
1900 | nack sli | Not Impacted | M | NORMAL |
1901 | | | | |
1902 | nack | Not Impacted | M | NORMAL |
1903 | rpsi | | | |
1904 | | | | |
1905 | nack app | Feedback parameters MUST be | M | SPECIAL |
1906 | | handled in the app specific way | | |
1907 | | when multiplexed | | |
1908 | | | | |
1909 | trr-int | This attribute applies to RTP | M | IDENTICAL |
1910 | | Session as a whole | | |
1911 | | | | |
1912 +----------+-----------------------------------+-------+------------+
1914 RFC4585 Attribute Analysis
1916 7.2. RFC5104 - Codec Control Messages in AVPF
1918 RFC5104 [RFC5104] specifies a few extensions to the messages defined
1919 in the Audio-Visual Profile with Feedback (AVPF). They are helpful
1920 primarily in conversational multimedia scenarios where centralized
1921 multipoint functionalities are in use. However, some are also usable
1922 in smaller multicast environments and point-to-point calls.
1924 +-----------+--------------+-------+----------+
1925 | Attr Name | Notes | Level | Category |
1926 +-----------+--------------+-------+----------+
1927 | ccm | Not Impacted | M | Normal |
1928 | | | | |
1929 +-----------+--------------+-------+----------+
1931 RFC5104 Attribute Analysis
1933 7.3. RFC6285 - Unicast-Based RAMS
1935 +-----------+---------------+-------+----------+
1936 | Name | Notes | Level | Category |
1937 +-----------+---------------+-------+----------+
1938 | nack rai | Not Impacted | M | NORMAL |
1939 | | | | |
1940 +-----------+---------------+-------+----------+
1942 RFC6285 Attribute Analysis
1944 7.4. RFC6679 - ECN for RTP over UDP/IP
1946 RFC6679 [RFC6679] specifies how Explicit Congestion Notification
1947 (ECN) can be used with the Real-time Transport Protocol (RTP) running
1948 over UDP, using the RTP Control Protocol (RTCP) as a feedback
1949 mechanism. It defines a new RTCP Extended Report (XR) block for
1950 periodic ECN feedback, a new RTCP transport feedback message for
1951 timely reporting of congestion events, and a Session Traversal
1952 Utilities for NAT (STUN) extension used in the optional
1953 initialization method using Interactive Connectivity Establishment
1954 (ICE)
1955 +------------------+---------------------------+-------+------------+
1956 | Name | Notes | Level | Category |
1957 +------------------+---------------------------+-------+------------+
1958 | ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL |
1959 | | the RTP Session level | | |
1960 | | | | |
1961 | nack ecn | This attribute enables | M | IDENTICAL |
1962 | | ECN at the RTP session | | |
1963 | | level | | |
1964 | | | | |
1965 +------------------+---------------------------+-------+------------+
1967 RFC6679 Attribute Analysis
1969 7.5. RFC6642 - Third-Party Loss Report
1971 In a large RTP session using the RTP Control Protocol (RTCP) feedback
1972 mechanism defined in RFC 4585 [RFC4585], a feedback target may
1973 experience transient overload if some event causes a large number of
1974 receivers to send feedback at once. This overload is usually avoided
1975 by ensuring that feedback reports are forwarded to all receivers,
1976 allowing them to avoid sending duplicate feedback reports. However,
1977 there are cases where it is not recommended to forward feedback
1978 reports, and this may allow feedback implosion. RFC6642 [RFC6642]
1979 memo discusses these cases and defines a new RTCP Third-Party Loss
1980 Report that can be used to inform receivers that the feedback target
1981 is aware of some loss event, allowing them to suppress feedback.
1982 Associated Session Description Protocol (SDP) signaling is also
1983 defined.
1985 +-------------+---------------+-------+----------+
1986 | Name | Notes | Level | Category |
1987 +-------------+---------------+-------+----------+
1988 | nack tllei | Not Impacted | M | NORMAL |
1989 | | | | |
1990 | nack pslei | Not Impacted | M | NORMAL |
1991 | | | | |
1992 +-------------+---------------+-------+----------+
1994 RFC6642 Attribute Analysis
1996 7.6. RFC5104 - Codec Control Messages in AVPF
1997 +------------+--------------+-------+----------+
1998 | Attr Name | Notes | Level | Category |
1999 +------------+--------------+-------+----------+
2000 | ccm fir | Not Impacted | M | NORMAL |
2001 | | | | |
2002 | ccm tmmbr | Not Impacted | M | NORMAL |
2003 | | | | |
2004 | ccm tstr | Not Impacted | M | NORMAL |
2005 | | | | |
2006 | ccm vbcm | Not Impacted | M | NORMAL |
2007 | | | | |
2008 +------------+--------------+-------+----------+
2010 RFC5104 Attribute Analysis
2012 8. group Attribute Analysis
2014 This section analyzes SDP "group" semantics [GROUP-SEM].
2016 8.1. RFC5888 - SDP Grouping Framework
2018 RFC5888 [RFC5888] defines a framework to group "m" lines in the
2019 Session Description Protocol (SDP) for different purposes.
2021 +------------+---------------+-------+----------+
2022 | Name | Notes | Level | Category |
2023 +------------+---------------+-------+----------+
2024 | group:LS | Not Impacted | S | NORMAL |
2025 | | | | |
2026 | group:FID | Not Impacted | S | NORMAL |
2027 | | | | |
2028 +------------+---------------+-------+----------+
2030 RFC5888 Attribute Analysis
2032 8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows
2034 RFC3524 [RFC3524] defines an extension to the Session Description
2035 Protocol (SDP) grouping framework. It allows requesting a group of
2036 media streams to be mapped into a single resource reservation flow.
2037 The SDP syntax needed is defined, as well as a new "semantics"
2038 attribute called Single Reservation Flow (SRF).
2040 +------------+---------------+-------+----------+
2041 | Name | Notes | Level | Category |
2042 +------------+---------------+-------+----------+
2043 | group:SRF | Not Impacted | S | NORMAL |
2044 | | | | |
2045 +------------+---------------+-------+----------+
2047 RFC3524 Attribute Analysis
2049 8.3. RFC4091 - ANAT Semantics
2051 RFC4091 [RFC4091] defines the Alternative Network Address Types
2052 (ANAT) semantics for the Session Description Protocol (SDP) grouping
2053 framework. The ANAT semantics allow alternative types of network
2054 addresses to establish a particular media stream.
2056 +-------------+---------------------------+-------+-----------------+
2057 | Name | Notes | Level | Category |
2058 +-------------+---------------------------+-------+-----------------+
2059 | group:ANAT | ANAT semantics is | S | NOT RECOMMENDED |
2060 | | obseleted | | |
2061 | | | | |
2062 +-------------+---------------------------+-------+-----------------+
2064 RFC4091 Attribute Analysis
2066 8.4. RFC5956 - FEC Grouping Semantics in SDP
2068 RFC5956 [RFC5956] defines the semantics for grouping the associated
2069 source and FEC-based (Forward Error Correction) repair flows in the
2070 Session Description Protocol (SDP). The semantics defined in the
2071 document are to be used with the SDP Grouping Framework (RFC 5888).
2072 These semantics allow the description of grouping relationships
2073 between the source and repair flows when one or more source and/or
2074 repair flows are associated in the same group, and they provide
2075 support for additive repair flows. SSRC-level (Synchronization
2076 Source) grouping semantics are also defined in this document for
2077 Real-time Transport Protocol (RTP) streams using SSRC multiplexing.
2079 +---------------+---------------+-------+----------+
2080 | Name | Notes | Level | Category |
2081 +---------------+---------------+-------+----------+
2082 | group:FEC-FR | Not Impacted | S | NORMAL |
2083 | | | | |
2084 +---------------+---------------+-------+----------+
2086 RFC5956 Attribute Analysis
2088 8.5. RFC5583 - Signaling Media Decoding Dependency in SDP
2090 RFC5583 [RFC5583] defines semantics that allow for signaling the
2091 decoding dependency of different media descriptions with the same
2092 media type in the Session Description Protocol (SDP). This is
2093 required, for example, if media data is separated and transported in
2094 different network streams as a result of the use of a layered or
2095 multiple descriptive media coding process.
2097 +--------+------------------------------+-------+-------------------+
2098 | Name | Notes | Level | Category |
2099 +--------+------------------------------+-------+-------------------+
2100 | depend | The attribute value must be | M | IDENTICAL-PER-PT |
2101 | lay | same for a given codec | | |
2102 | | configuration | | |
2103 | | | | |
2104 | depend | The attribute value must be | M | IDENTICAL-PER-PT |
2105 | mdc | same for a given codec | | |
2106 | | configuration | | |
2107 | | | | |
2108 +--------+------------------------------+-------+-------------------+
2110 RFC5583 Attribute Analysis
2112 The usage of identical Payload Type values across multiplexed m=lines
2113 is described in [I-D.ietf-mmusic-sdp-bundle-negotiation].
2115 9. ssrc-group Attribute Analysis
2117 This section analyzes "ssrc-group" semantics [SSRC-GROUP].
2119 9.1. RFC5576 - Source-Specific SDP Attributes
2121 +---------+---------------+-------+----------+
2122 | Name | Notes | Level | Category |
2123 +---------+---------------+-------+----------+
2124 | FID | Not Impacted | M | NORMAL |
2125 | | | | |
2126 | FEC | Not Impacted | M | NORMAL |
2127 | | | | |
2128 | FEC-FR | Not Impacted | M | NORMAL |
2129 | | | | |
2130 +---------+---------------+-------+----------+
2132 RFC5576 Attribute Analysis
2134 10. QoS Mechanism Token Analysis
2136 This section analyzes QoS tokes specified with SDP[QOS].
2138 10.1. RFC5432 - QoS Mechanism Selection in SDP
2140 +-------+----------------------------------------+-------+----------+
2141 | Name | Notes | Level | Category |
2142 +-------+----------------------------------------+-------+----------+
2143 | rsvp | Not Impacted, since QOS mechanisms are | B | NORMAL |
2144 | | applied per flow. | | |
2145 | | | | |
2146 | nsis | Not Impacted, since QOS mechanisms are | B | NORMAL |
2147 | | applied per flow. | | |
2148 | | | | |
2149 +-------+----------------------------------------+-------+----------+
2151 RFC5432 Attribute Analysis
2153 11. k= Attribute Analysis
2155 11.1. RFC4566 SDP: Session Description Protocol
2157 +------+------------------------------------+-------+---------------+
2158 | Name | Notes | Level | Category |
2159 +------+------------------------------------+-------+---------------+
2160 | k= | It is NOT recommended to use this | S | NOT |
2161 | | attribute | | RECOMMENDED |
2162 | | | | |
2163 +------+------------------------------------+-------+---------------+
2165 RFC4566 Attribute Analysis
2167 12. content Atribute Analysis
2169 12.1. RFC4796
2170 +------------------+---------------+-------+----------+
2171 | Name | Notes | Level | Category |
2172 +------------------+---------------+-------+----------+
2173 | content:slides | Not Impacted | M | NORMAL |
2174 | | | | |
2175 | content:speaker | Not Impacted | M | NORMAL |
2176 | | | | |
2177 | content:main | Not Impacted | M | NORMAL |
2178 | | | | |
2179 | content:sl | Not Impacted | M | NORMAL |
2180 | | | | |
2181 | content:alt | Not Impacted | M | NORMAL |
2182 | | | | |
2183 +------------------+---------------+-------+----------+
2185 RFC4796 Attribute Analysis
2187 13. Payload Formats
2189 13.1. RFC5109 - RTP Payload Format for Generic FEC
2191 RFC5109 [RFC5109] describes a payload format for generic Forward
2192 Error Correction (FEC) for media data encapsulated in RTP. It is
2193 based on the exclusive-or (parity) operation. The payload format
2194 allows end systems to apply protection using various protection
2195 lengths and levels, in addition to using various protection group
2196 sizes to adapt to different media and channel characteristics. It
2197 enables complete recovery of the protected packets or partial
2198 recovery of the critical parts of the payload depending on the packet
2199 loss situation.
2201 +---------------------+----------------------+-------+--------------+
2202 | Name | Notes | Level | Category |
2203 +---------------------+----------------------+-------+--------------+
2204 | audio/ulpfec | Not recommended for | M | NOT |
2205 | | multiplexing due to | | RECOMMENDED |
2206 | | reuse of SSRCs | | |
2207 | | | | |
2208 | video/ulpfec | Not recommended for | M | NOT |
2209 | | multiplexing due to | | RECOMMENDED |
2210 | | reuse of SSRCs | | |
2211 | | | | |
2212 | text/ulpfec | Not recommended for | M | NOT |
2213 | | multiplexing due to | | RECOMMENDED |
2214 | | reuse of SSRCs | | |
2215 | | | | |
2216 | application/ulpfec | Not recommended for | M | NOT |
2217 | | multiplexing due to | | RECOMMENDED |
2218 | | reuse of SSRCs | | |
2219 | | | | |
2220 +---------------------+----------------------+-------+--------------+
2222 RFC5109 Payload Format Analysis
2224 Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make
2225 it possible to use ULP with multiplexing and ULP is allowed when used
2226 with that.
2228 14. Multiplexing Media Streams and DSCP Markings
2230 Note: This section does not yet have WG consensus but is included as
2231 a proposal to the WG. There are two options being proposed, A and B.
2232 The authors suggest A.
2234 14.1. Option A
2236 This section provides two rules for multiplexing multiple media
2237 streams with DSCP markings over a single 5-tuple.
2239 Rule 1: Media Streams with markings from different service classes
2240 MUST NOT be multiplexed. For example, a media stream with DSCP
2241 Marking EF MUST NOT be multiplexed with a media stream marked with
2242 AF class. Likewise, a media stream with DSCP marking AF3x MUST
2243 NOT be multiplexed with a media stream marked with AF4x.
2245 Rule 2: Media Streams that belong to the same service class, even
2246 with different drop precedence, MAY be multiplexed. Thus media
2247 streams that all belong to the EF group or all that belong to the
2248 AF4X class can be multiplexed.
2250 For WebRTC applications following the advice in
2251 [I-D.dhesikan-tsvwg-rtcweb-qos], the above rules end up allowing the
2252 audio and video to be multiplexed in many, but not all, cases.
2254 14.2. Option B
2256 Media Streams MAY be multiplexed regardless of what the setting of
2257 the DSCP Per Hop Behavior group (PHB).
2259 15. Multiplexing Considerations for Encapsulating Attributes
2261 This sections deals with recommendations for defining the
2262 multiplexing characteristics of the SDP attributes that encapsulate
2263 other SDP attributes/parameters. Such attributes as of today, for
2264 example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of
2265 a generic framework for indicating and negotiating transport, media
2266 and media format related capabilities in the SDP.
2268 The behavior of such attributes under multiplexing is in turn defined
2269 by the multiplexing behavior of the attributes they encapsulate which
2270 are made known once the Offer/Answer negotiation process is
2271 completed.
2273 15.1. RFC3407 - cpar Attribute Analysis
2275 RFC3407 capability parameter attribute (a=cpar) encapsulates b=
2276 (bandwidth) or an a= attribute. For bandwidth attribute
2277 encapsulation, the category SUM is inherited. For the case of a=
2278 attribute, the category corresponding to the SDP attribute being
2279 referenced is inherited.
2281 v=0
2282 o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
2283 s=
2284 c=IN IP4 host.atlanta.example.com
2285 t=0 0
2286 m=video 3456 RTP/AVP 100
2287 a=rtpmap:100 VP8/90000
2288 a=sqn: 0
2289 a=cdsc: 1 video RTP/AVP 100
2290 a=cpar: a=rtcp-mux
2291 m=video 3456 RTP/AVP 101
2292 a=rtpmap:101 VP8/90000
2293 a=fmtp:100 max-fr=15;max-fs=1200
2294 a=cdsc: 2 video RTP/AVP 101
2295 a=cpar: a=rtcp-mux
2297 In the above example ,the category IDENTICAL is inherited for the
2298 cpar encapsulated rtcp-mux attribute.
2300 15.2. RFC5939 Analysis
2302 [RFC5939] defines a general SDP capability negotiation framework. It
2303 also specifies how to provide transport protocols and SDP attributes
2304 as capabilities and negotiate them using the framework.
2306 For this purpose, [RFC5939] defines the following
2308 o A set of capabilities for the session and its associated media
2309 stream components, supported by each side. The attribute
2310 ("a=acap") defines how to list an attribute name and its
2311 associated value (if any) as a capability. The attribute
2312 ("a=tcap") that defines how to list transport protocols (e.g.,
2313 "RTP/AVP") as capabilities.
2315 o A set of potential configurations indicating which combinations of
2316 those capabilities can be used for the session and its associated
2317 media stream components. Potential configurations are not ready
2318 for use. Instead, they provide an alternative that may be used,
2319 subject to further negotiation.
2321 o An actual configuration for the session and its associated media
2322 stream components, that specifies which combinations of session
2323 parameters and media stream components can be used currently and
2324 with what parameters. Use of an actual configuration does not
2325 require any further negotiation.
2327 o A negotiation process that takes the set of actual and potential
2328 configurations (combinations of capabilities) as input and
2329 provides the negotiated actual configurations as output.
2331 15.2.1. Recommendations
2333 This section provides recommendations for entities generating and
2334 processing SDP under the generic capability negotiation framework as
2335 defined in [RFC5939] under the context of media stream multiplexing.
2337 These recommendations are provided for the purposes of enabling the
2338 Offerer to make sure that the generated potential configurations
2339 between the multiplexed streams can (easily) be negotiated to be
2340 consistent between those streams.
2342 15.2.1.1. Recommendation-1: Transport Capability Analysis
2344 When a transport capability is proposed as a potential configuration
2345 under a given media description, it is recommended that all the media
2346 descriptions under multiplexing have the same potential configuration
2347 number for the given transport capability.
2349 a=tcap:1 RTP/SAVPF
2350 a=tcap:2 RTP/SAVP
2351 a=group:BUNDLE audio video
2352 m= audio
2353 a=mid:audio
2354 a=pcfg:1 t=1
2355 a=pcfg:2
2356 m= video
2357 a=mid:video
2358 a=pcfg:1 t=1
2359 a=pcfg:2 t=2
2361 In the example above, the potential configurations that Offer
2362 transport protocol capability of RTP/SAVPF has the same configuration
2363 number "1" in both the audio and video media descriptions.
2365 15.2.1.2. Recommendation-2: Attribute Capability Analysis
2367 For attribute capabilities which are offered as potential
2368 configurations that encapsulate attributes whose value MUST be
2369 IDENTICAL under multiplexing, it is recommended that all the media
2370 descriptions under multiplexing have the same potential configuration
2371 number for the given attribute capability.
2373 a=acap:1 a=rtcp-mux
2374 a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80
2375 inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
2376 a=group:BUNDLE audio video
2377 m= audio 49172 RTP/AVP 99
2378 a=mid:audio
2379 a=pcfg:1 a=1
2380 a=pcfg:2
2381 m= video 560024 RTP/AVP 100
2382 a=mid:video
2383 a=pcfg:1 a=1
2384 a=pcfg:2 a=2
2386 In the example above, the potential configuration number 1 is
2387 repeated while referring to attribute capability a=rtcp-mux, since
2388 the behavior is IDENTICAL for the attribute a=rtcp-mux under
2389 multiplexing.
2391 15.2.1.3. Recommendation-3: Sescap Attribute Analysis
2393 It is recommended that any bundled media descriptions/configurations
2394 are also acceptable combinations of media streams/configurations as
2395 specified by "sescap" attribute.
2397 15.2.1.4. Recommendation-4: Capability Extension Attributes
2399 Since it is nearly impossible to define a generic mechanism for
2400 various capability extensions , this document does't provide
2401 procedures for dealing with the capability extension attributes.
2402 However, Section Section 15.3 provide analysis of media capability
2403 extension attributes as defined in [RFC6871].
2405 15.3. RFC6871 Analysis
2407 [RFC6871] extends capability negotiation framework described in
2408 [RFC5939] by defining media capabilities that can be used to indicate
2409 and negotiate media types and their associated format parameters.
2411 Building upon the analysis from the previous section, following
2412 recommendation is provided for dealing with the attributes defined in
2413 [RFC6871] under multiplexing
2415 15.3.1. Recommendation-5: Attribute Capability Under Shared Payload
2416 Type
2418 For attribute capabilities which are offered as potential
2419 configurations that encapsulate attributes whose value MUST be
2420 IDENTICAL-PER-PT under multiplexing, it is recommended that all the
2421 media descriptions under multiplexing have the same potential
2422 configuration number for the given attribute capability
2424 The attributes (a=rmcap, a=mfcap) follow the above recommendations
2425 under mutliplexing
2426 v=0
2427 o=- 25678 753849 IN IP4 192.0.2.1
2428 s=
2429 c=IN IP4 192.0.2.1
2430 t=0 0
2431 a=creq:med-v0
2432 m=audio 54322 RTP/AVP 96
2433 a=rtpmap:96 AMR-WB/16000/1
2434 a=fmtp:96 mode-change-capability=1; max-red=220;
2435 mode-set=0,2,4,7
2436 a=rmcap:1,3 audio AMR-WB/16000/1
2437 a=rmcap:2 audio AMR/8000/1
2438 a=mfcap:1,2 mode-change-capability=1
2439 a=mfcap:3 mode-change-capability=2
2440 a=pcfg:1 m=1 pt=1:96
2441 a=pcfg:2 m=2 pt=2:97
2442 a=pcfg:3 m=3 pt=3:98
2444 m=audio 54322 RTP/AVP 96
2445 a=rtpmap:96 AMR-WB/16000/1
2446 a=fmtp:96 mode-change-capability=1; max-red=220;
2447 mode-set=0,2,4,7
2448 a=rmcap:4 audio AMR/8000/1
2449 a=rmcap:5 audio OPUS/48000/2
2450 a=mfcap:5 minptime=40
2451 a=mfcap:4 mode-change-capability=1
2452 a=pcfg:1 m=4 pt=4:97
2453 a=pcfg:4 m=5 pt=5:101
2455 In the example above, the potential configuration number 1 is
2456 repeated when referring to media and media format capability used for
2457 the Payload Type 97. This implies that both the media capability 2
2458 and 4 along with their media format capabilities MUST refer to the
2459 same Codec configuration , as per the definition of IDENTICAL-PER-PT
2461 15.4. Recommendation-6: Offer/Answer Negotiation Expectations
2463 For attributes encapsulated via "a=acap", "a=omcap", "a=mscap"
2464 capability attributes and presented as part of potential/actual
2465 configurations during the Offer/Answer negotiation prodecure, the
2466 negotiation MUST ensure that the multiplexing behavior of these
2467 capabilities inherit from the behavior of the attribute being
2468 encapsulated.
2470 Example 1: Below SDP example captures the following aspects.
2472 o The Offerer offers audio and video streams with several different
2473 RTP profiles (AVP, SAVP, SAVPF) as potential configurations.
2475 o Valid Answer that corresponds to the SDP answer where the Answerer
2476 accepts RTP/SAVPF as the default profile for both the media
2477 streams. In this scenario both the media streams can be
2478 successfully multiplexed.
2480 o Invalid Answer wherein the Answerer accepts the profile RTP/SAVPF
2481 for the audio stream and RTP/AVPF for the video stream. This
2482 scenario results in the failure of the multiplexing as defined in
2483 the section 7.2 of the BUNDLE specification [I-D.ietf-mmusic-sdp-
2484 bundle-negotiation].
2486
2487 v=0
2488 o=- 25678 753849 IN IP4 192.0.2.1
2489 s=
2490 t=0 0
2491 c=IN IP4 192.0.2.1
2492 m=audio 3456 RTP/AVP 98
2493 a=tcap:1 RTP/SAVPF
2494 a=rtpmap:98 OPUS/48000/2
2495 a=pcfg:1 t=1
2496 m=video 51372 RTP/AVP 101
2497 a=rtpmap:101 H264/90000
2498 a=tcap:2 RTP/SAVPF RTP/AVPF
2499 a=pcfg:2 t=2|3
2501
2502 v=0
2503 o=- 24351 621814 IN IP4 192.0.2.2
2504 s=
2505 m=audio 3456 RTP/SAVPF 98
2506 a=rtpmap:98 OPUS/48000/2
2507 a=acfg:1 t=1
2509 m=video 51372 RTP/SAVPF 101
2510 a=rtpmap:101 H264/90000
2511 a=acfg:2 t=2
2513
2514 v=0
2515 o=- 24351 621814 IN IP4 192.0.2.2
2516 s=
2517 m=audio 3456 RTP/SAVPF 98
2518 a=rtpmap:98 OPUS/48000/2
2519 a=acfg:1 t=1
2521 m=video 51372 RTP/AVPF 101
2522 a=rtpmap:101 H264/90000
2523 a=acfg:2 t=3
2525 16. IANA Considerations
2527 IANA shall register categories from this specification by expanding
2528 the Session Description Protocol (SDP) Parameters table with a column
2529 listing categories against each SDP parameter.
2531 +---------------------+
2532 | Category |
2533 +---------------------+
2534 | NORMAL |
2535 +---------------------+
2536 | NOT RECOMMENDED |
2537 +---------------------+
2538 | IDENTICAL |
2539 +---------------------+
2540 | TRANSPORT |
2541 +---------------------+
2542 | INHERIT |
2543 ----------------------+
2544 | IDENTICAL-PER-PT |
2545 +---------------------+
2546 | SPECIAL |
2547 ----------------------
2549 17. Security Considerations
2551 All the attributes which involve security key needs a careful review
2552 to ensure two-time pad vulnerability is not created.
2554 18. Acknowledgments
2556 I would like to thank Cullen Jennings for suggesting the categories,
2557 contributing text and reviewing the draft. I would also link to
2558 thank Magnus, Christer, Jonathan Lennox, Bo Burman, and Dan on
2559 suggesting structural changes helping improve the document
2560 readability.
2562 I would like also to thank following experts on their inputs and
2563 reviews as listed - Flemming Andreasen(5.20,5.28,5.29,15), Rohan
2564 Mahy(5.45), Eric Burger(5.22),Christian Huitema(5.13), Christer
2565 Holmberg(5.17,5.22,5.40,5.41), Richard Ejzak (5.36,5.42,5.43,5.44),
2566 Colin Perkins(5.7,5.8), Magnus westerlund(5.2,5.3,5.9,5.26,
2567 5.27,6.1,6.2,6.3,8.3,7), Roni Evens(5.12,5.27,8.4), Subha
2568 Dhesikan(5.5,12.1,14), Dan Wing(5.6,5.11,5.30,5.34,5.37), Ali C
2569 Begen(5.1,5.16,5.18,5.21,5.33,8.2,8.4,13.1), Bo Burman (7.2,7.6),
2570 Charles Eckel(5.14,5.23,5.24,9.1,8.5), Paul Kyzivat(5.24), Ian
2571 Johansson(5.15), Saravanan Shanmugham(5.10), Paul E Jones(5.25),
2572 Rajesh Kumar(5.39), Jonathan Lennox(5.31,5,14,11.1), Mo
2573 Zanaty(5.4,5.19,8.1,8.3,8.5,12.1), Christian Huitema (5.13), Qin Wu
2574 (5.38 PM-Dir review).
2576 19. Change Log
2578 [RFC EDITOR NOTE: Please remove this section when publishing]
2580 Changes from draft-ietf-mmusic-sdp-mux-attributes-01
2582 o Updated section 15 to provide detailed recommendation on dealing
2583 with encapsulating attributes. Also updated sections 5.20, 5.28,
2584 5.29 to refer to Section 15.
2586 o Added new categories IDENTICAL-PER-PT and INHERIT
2588 o Updated Sections 16 to add the new categories.
2590 o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the
2591 category IDENTICAL-PER-PT.
2593 o Reformatted section 4 to add individual categories to their own
2594 sections.
2596 Changes from draft-ietf-mmusic-sdp-mux-attributes-00
2598 o Added Section 15 to provide recommendations on multiplexing SDP
2599 encapsulating attributes. Also updated sections 5.20, 5.28, 5.29
2600 to refer to Section 15.
2602 o Updated Section 5.38 to incorporate PM-dir review inputs from Qin
2603 Wu
2605 o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more
2606 clarity.
2608 o Fixed few nits regarding sentence clarity and fill-in the NOTES
2609 section where information was lacking.
2611 Changes from draft-nandakumar-mmusic-mux-attributes-05
2613 o Renamed the document to be a WG document.
2615 o Added Section 14.
2617 o Updated Open Issues based on IETF88 discussions.
2619 Changes from draft-nandakumar-mmusic-mux-attributes-04
2621 o Added few OPEN ISSUES that needs to be discussed.
2623 o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4,
2624 5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1
2626 o Updated Table Column name Current to Level and improved TRANSPORT
2627 category explanation on suggestions form Dan Wing.
2629 o Grouped all the rtcp-fb attribute analysis under a single section
2630 as suggested by Magnus/
2632 Changes from draft-nandakumar-mmusic-mux-attributes-03
2634 o Maintenance change to clean up grammatical nits and wordings.
2636 Changes from draft-nandakumar-mmusic-mux-attributes-02
2638 o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34,
2639 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
2640 the inputs from the respective RFC Authors.
2642 Changes from draft-nandakumar-mmusic-mux-attributes-01
2644 o Replaced Category BAD with NOT RECOMMENDED.
2646 o Added Category TBD.
2648 o Updated IANA Consideration Section.
2650 Changes from draft-nandakumar-mmusic-mux-attributes-00
2652 o Added new section for dealing with FEC payload types.
2654 20. References
2656 20.1. Normative References
2658 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
2659 Requirement Levels", BCP 14, RFC 2119, March 1997.
2661 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
2662 Description Protocol", RFC 4566, July 2006.
2664 20.2. Informative References
2666 [ACK-NACK]
2667 "S Description Protocol (SDP) RTCP ACK/NACK Feedback
2668 attributes", .
2671 [CCM] "S Description Protocol (SDP) RTCP-FB Codec Control
2672 Messages", .
2675 [GROUP-SEM]
2676 "S Description Protocol (SDP) "group" semantics",
2677 .
2680 [H.248.15]
2681 "Gateway control protocol: SDP H.248 package attribute",
2682 .
2684 [I-D.dhesikan-tsvwg-rtcweb-qos]
2685 Dhesikan, S., Druta, D., Jones, P., and J. Polk, "DSCP and
2686 other packet markings for RTCWeb QoS", draft-dhesikan-
2687 tsvwg-rtcweb-qos-02 (work in progress), July 2013.
2689 [I-D.ietf-avt-multiplexing-rtp]
2690 El-Khatib, K., Luo, G., Bochmann, G., and Pinjiang. Feng,
2691 "Multiplexing Scheme for RTP Flows between Access
2692 Routers", http://tools.ietf.org/html/
2693 draft-ietf-avt-multiplexing-rtp-01 (work in progress),
2694 October 1999.
2696 [I-D.ietf-mmusic-sdp-bundle-negotiation]
2697 Holmberg, C., Alvestrand, H., and C. Jennings,
2698 "Multiplexing Negotiation Using Session Description
2699 Protocol (SDP) Port Numbers", draft-ietf-mmusic-sdp-
2700 bundle-negotiation-03 (work in progress), February 2013.
2702 [IANA] "S Description Protocol (SDP) Parameters",
2703 .
2706 [MEDIA_LOOPBACK]
2707 Kaplan, H., Hedayat, K., Venna, N., Jones, P., and N.
2708 Stratton, "An Extension to the Session Description
2709 Protocol (SDP) and Real-time Transport Protocol (RTP) for
2710 Media Loopback", 6489 (work in progress), January 2013.
2712 [QOS] "S Description Protocol (SDP) QoS Mechanism Tokens",
2713 .
2716 [R3GPPTS24.182]
2717 "IP Multimedia Subsystem (IMS) Customized Alerting Tones
2718 (CAT); Protocol specification",
2719 .
2721 [R3GPPTS24.183]
2722 "IP Multimedia Subsystem (IMS) Customized Ringing Signal
2723 (CRS); Protocol specification",
2724 .
2726 [R3GPPTS24.229]
2727 "IP multimedia call control protocol based on Session
2728 Initiation Protocol (SIP) and Session Description Protocol
2729 (SDP);",
2730 .
2732 [RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the
2733 Session Description Protocol (SDP) for ATM Bearer
2734 Connections", RFC 3108, May 2001.
2736 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
2737 with Session Description Protocol (SDP)", RFC 3264, June
2738 2002.
2740 [RFC3407] Andreasen, F., "S Description Protocol (SDP) Simple
2741 Capability Declaration", RFC 3407, October 2002.
2743 [RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to
2744 Resource Reservation Flows", RFC 3524, April 2003.
2746 [RFC3556] Casner, S., "S Description Protocol (SDP) Bandwidth
2747 Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC
2748 3556, July 2003.
2750 [RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
2751 in Session Description Protocol (SDP)", RFC 3605, October
2752 2003.
2754 [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
2755 Protocol Extended Reports (RTCP XR)", RFC 3611, November
2756 2003.
2758 [RFC3890] Westerlund, M., "A Transport Independent Bandwidth
2759 Modifier for the Session Description Protocol (SDP)", RFC
2760 3890, September 2004.
2762 [RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network
2763 Address Types (ANAT) Semantics for the Session Description
2764 Protocol (SDP) Grouping Framework", RFC 4091, June 2005.
2766 [RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
2767 the Session Description Protocol (SDP)", RFC 4145,
2768 September 2005.
2770 [RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E.
2771 Carrara, "Key Management Extensions for Session
2772 Description Protocol (SDP) and Real Time Streaming
2773 Protocol (RTSP)", RFC 4567, July 2006.
2775 [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "S Description
2776 Protocol (SDP) Security Descriptions for Media Streams",
2777 RFC 4568, July 2006.
2779 [RFC4570] Quinn, B. and R. Finlayson, "S Description Protocol (SDP)
2780 Source Filters", RFC 4570, July 2006.
2782 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
2783 Transport Layer Security (TLS) Protocol in the Session
2784 Description Protocol (SDP)", RFC 4572, July 2006.
2786 [RFC4574] Levin, O. and G. Camarillo, "The Session Description
2787 Protocol (SDP) Label Attribute", RFC 4574, August 2006.
2789 [RFC4583] Camarillo, G., "S Description Protocol (SDP) Format for
2790 Binary Floor Control Protocol (BFCP) Streams", RFC 4583,
2791 November 2006.
2793 [RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
2794 "Extended RTP Profile for Real-time Transport Control
2795 Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July
2796 2006.
2798 [RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description
2799 Protocol (SDP) Content Attribute", RFC 4796, February
2800 2007.
2802 [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
2803 Session Relay Protocol (MSRP)", RFC 4975, September 2007.
2805 [RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
2806 "Codec Control Messages in the RTP Audio-Visual Profile
2807 with Feedback (AVPF)", RFC 5104, February 2008.
2809 [RFC5109] Li, A., "RTP Payload Format for Generic Forward Error
2810 Correction", RFC 5109, December 2007.
2812 [RFC5159] Dondeti, L. and A. Jerichow, "S Description Protocol (SDP)
2813 Attributes for Open Mobile Alliance (OMA) Broadcast
2814 (BCAST) Service and Content Protection", RFC 5159, March
2815 2008.
2817 [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
2818 (ICE): A Protocol for Network Address Translator (NAT)
2819 Traversal for Offer/Answer Protocols", RFC 5245, July
2820 2006.
2822 [RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP
2823 Header Extensions", RFC 5285, July 2008.
2825 [RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of
2826 Service (QoS) Mechanism Selection in the Session
2827 Description Protocol (SDP)", RFC 5432, March 2009.
2829 [RFC5506] Johansson, I., "Support for Reduced-Size Real-Time
2830 Transport Control Protocol (RTCP): Opportunities and
2831 Consequences", RFC 5506, April 2009.
2833 [RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
2834 and P. Kyzivat, "A Session Description Protocol (SDP)
2835 Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
2836 May 2009.
2838 [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
2839 Media Attributes in the Session Description Protocol
2840 (SDP)", RFC 5576, June 2009.
2842 [RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding
2843 Dependency in the Session Description Protocol (SDP)", RFC
2844 5583, July 2009.
2846 [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
2847 Protocol (RTCP) Extensions for Single-Source Multicast
2848 Sessions with Unicast Feedback", RFC 5760, February 2010.
2850 [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
2851 Control Packets on a Single Port", RFC 5761, April 2010.
2853 [RFC5762] Perkins, C., "RTP and the Datagram Congestion Control
2854 Protocol (DCCP)", RFC 5762, April 2010.
2856 [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
2857 for Establishing a Secure Real-time Transport Protocol
2858 (SRTP) Security Context Using Datagram Transport Layer
2859 Security (DTLS)", RFC 5763, May 2010.
2861 [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
2862 Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
2864 [RFC5939] Andreasen, F., "S Description Protocol (SDP) Capability
2865 Negotiation", RFC 5939, September 2010.
2867 [RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in
2868 the Session Description Protocol", RFC 5956, September
2869 2010.
2871 [RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions
2872 Defined for 3GPP Packet-Switched Streaming Service and
2873 Multimedia Broadcast/Multicast Service", RFC 6064, January
2874 2011.
2876 [RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source-
2877 Specific Multicast (SSM) Sessions", RFC 6128, February
2878 2011.
2880 [RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
2881 Path Key Agreement for Unicast Secure RTP", RFC 6189,
2882 April 2011.
2884 [RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for
2885 the Internet Key Exchange Protocol (IKE) in the Session
2886 Description Protocol (SDP)", RFC 6193, April 2011.
2888 [RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media
2889 Control Channel Framework", RFC 6230, May 2011.
2891 [RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image
2892 Attributes in the Session Description Protocol (SDP)", RFC
2893 6236, May 2011.
2895 [RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping
2896 between Unicast and Multicast RTP Sessions", RFC 6284,
2897 June 2011.
2899 [RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
2900 "Unicast-Based Rapid Acquisition of Multicast RTP
2901 Sessions", RFC 6285, June 2011.
2903 [RFC6364] Begen, A., "S Description Protocol Elements for the
2904 Forward Error Correction (FEC) Framework", RFC 6364,
2905 October 2011.
2907 [RFC6642] Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP)
2908 Extension for a Third-Party Loss Report", RFC 6642, June
2909 2012.
2911 [RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
2912 and K. Carlberg, "Explicit Congestion Notification (ECN)
2913 for RTP over UDP", RFC 6679, August 2012.
2915 [RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
2916 Establishment for Media Anchoring (CEMA) for the Message
2917 Session Relay Protocol (MSRP)", RFC 6714, August 2012.
2919 [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
2920 Datagram Congestion Control Protocol UDP Encapsulation for
2921 NAT Traversal", RFC 6773, November 2012.
2923 [RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control
2924 Protocol Version 2 (MRCPv2)", RFC 6787, November 2012.
2926 [RFC6871] Gimlan, R., Evan, R., and F. Andreasen, "Session
2927 Description Protocol (SDP) Media Capabilities
2928 Negotiation", RFC 6871, Febrauary 2013.
2930 [RTCP-FB] "S Description Protocol (SDP) RTCP Feedback attributes",
2931 .
2934 [SSRC-GROUP]
2935 "S Description Protocol (SDP) "ssrc-group" semantics",
2936 .
2939 [T.38] "Procedures for real-time Group 3 facsimile communication
2940 over IP networks", .
2942 Author's Address
2944 Suhas Nandakumar
2945 Cisco
2946 170 West Tasman Drive
2947 San Jose, CA 95134
2948 USA
2950 Email: snandaku@cisco.com