Network Working Group S. Nandakumar
Internet-Draft Cisco
Intended status: Standards Track October 20, 2014
Expires: April 23, 2015
A Framework for SDP Attributes when Multiplexing
draft-ietf-mmusic-sdp-mux-attributes-03
Abstract
The Session Description Protocol (SDP) provides mechanisms to
describe attributes of multimedia sessions and of individual media
streams (e.g., Real-time Transport Protocol (RTP) sessions) within a
multimedia session. In the RTCWeb WG, there is a need to use a
single 5-tuple for sending and receiving media associated with
multiple media descriptions ("m=" lines). Such a requirement has
raised concerns over the semantic implications of the SDP attributes
associated with the RTP Media Streams multiplexed over a single
transport layer flow.
The scope of this specification is to provide a framework for
analyzing the multiplexing characteristics of SDP attributes. The
specification also categorizes existing attributes based on the
framework described herein.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 23, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . 6
4.1. Category: NORMAL . . . . . . . . . . . . . . . . . . . . 7
4.2. Category: NOT RECOMMENDED . . . . . . . . . . . . . . . . 7
4.3. Category: IDENTICAL . . . . . . . . . . . . . . . . . . . 8
4.4. Category: SUM . . . . . . . . . . . . . . . . . . . . . . 8
4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 9
4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 10
4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 10
4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 11
4.9. Category: TBD . . . . . . . . . . . . . . . . . . . . . . 11
5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 11
5.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 12
5.2. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 13
5.3. RFC5761 - Multiplexing RTP and RTCP . . . . . . . . . . . 14
5.4. RFC3312 - Integration of Resource Management and (SIP) . 14
5.5. RFC4574 - SDP Label Attribute . . . . . . . . . . . . . . 15
5.6. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 15
5.7. RFC4568 - SDP Security Descriptions . . . . . . . . . . . 16
5.8. RFC5762 - RTP over DCCP . . . . . . . . . . . . . . . . . 16
5.9. RFC6773 - DCCP-UDP Encapsulation . . . . . . . . . . . . 17
5.10. RFC5506 - Reduced-Size RTCP in RTP Profile . . . . . . . 18
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5.11. RFC6787 - Media Resource Control Protocol Version 2 . . . 18
5.12. RFC5245 - Interactive Connectivity Establishment (ICE) . 19
5.13. RFC5285 - RTP Header Extensions . . . . . . . . . . . . . 20
5.14. RFC3605 - RTCP attribute in SDP . . . . . . . . . . . . . 21
5.15. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 21
5.16. RFC7273 - RTP Clock Source Signalling . . . . . . . . . . 22
5.17. RFC6236 - Image Attributes in SDP . . . . . . . . . . . . 23
5.18. RFC7197 - Duplication Delay Attribute in SDP . . . . . . 23
5.19. RFC7226 - RTCP XR Blocks for MOS Metric Reporting . . . 23
5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions . . 24
5.21. RFC6230 - Media Control Channel Framework . . . . . . . . 24
5.22. RFC6364 - SDP Elements for FEC Framework . . . . . . . . 25
5.23. RFC4796 - Content Attribute . . . . . . . . . . . . . . . 25
5.24. RFC3407 - SDP Simple Capability Declaration . . . . . . . 25
5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP
Sessions . . . . . . . . . . . . . . . . . . . . . . . . 26
5.26. RFC6714 - MSRP-CEMA . . . . . . . . . . . . . . . . . . . 26
5.27. RFC4583 - SDP Format for BFCP Streams . . . . . . . . . . 27
5.28. RFC5547 - SDP Offer/Answer for File Transfer . . . . . . 27
5.29. RFC6489 - SDP and RTP Media Loopback Extension . . . . . 28
5.30. RFC5760 - RTCP with Unicast Feedback . . . . . . . . . . 28
5.31. RFC3611 - RTCP XR . . . . . . . . . . . . . . . . . . . . 29
5.32. RFC5939 - SDP Capability Negotiation . . . . . . . . . . 29
5.33. RFC6871- SDP Media Capabilities Negotiation . . . . . . . 30
5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP . . 31
5.35. RFC4567 - Key Management Extensions for SDP and RTSP . . 32
5.36. RFC4572 - Comedia over TLS in SDP . . . . . . . . . . . . 33
5.37. RFC4570 - SDP Source Filters . . . . . . . . . . . . . . 33
5.38. RFC6128 - RTCP Port for Multicast Sessions . . . . . . . 34
5.39. RFC6189 - ZRTP . . . . . . . . . . . . . . . . . . . . . 34
5.40. RFC4145 - Connection-Oriented Media . . . . . . . . . . . 35
5.41. RFC6947 - The SDP ALTC Attribute . . . . . . . . . . . . 35
5.42. RFC7195 - SDP Extension for Circuit Switched Bearers
in PSTN . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP) . . 36
5.44. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . 37
5.45. RFC6193 - Media Description for IKE in SDP . . . . . . . 37
5.46. RFC6064 - SDP and RTSP Extensions for 3GPP . . . . . . . 38
5.47. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . . 41
5.48. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 42
5.49. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 43
5.50. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 43
5.51. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 43
5.52. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 44
5.53. ITU-T-REC.Q1970 . . . . . . . . . . . . . . . . . . . . . 45
5.54. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 46
5.55. RFC4975 - The Message Session Relay Protocol . . . . . . 46
5.56. Historical . . . . . . . . . . . . . . . . . . . . . . . 47
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6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 48
6.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 48
6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . 48
6.3. RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . 49
7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 50
7.1. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . 50
7.2. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 51
7.3. RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . 52
7.4. RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . . 52
7.5. RFC6642 - Third-Party Loss Report . . . . . . . . . . . . 53
7.6. RFC5104 - Codec Control Messages in AVPF . . . . . . . . 54
8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 54
8.1. RFC5888 - SDP Grouping Framework . . . . . . . . . . . . 54
8.2. RFC3524 - Mapping Media Streams to Resource
Reservation Flows . . . . . . . . . . . . . . . . . . . . 55
8.3. RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . 55
8.4. RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . . 55
8.5. RFC5583 - Signaling Media Decoding Dependency in SDP . . 56
8.6. RFC7104 - Duplication Grouping Semantics in the SDP . . 56
9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 57
9.1. RFC5576 - Source-Specific SDP Attributes . . . . . . . . 57
9.2. RFC7104 - Duplication Grouping Semantics in the SDP . . . 57
10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 57
10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . 57
11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 58
11.1. RFC4566 SDP: Session Description Protocol . . . . . . . 58
12. content Atribute Analysis . . . . . . . . . . . . . . . . . . 58
12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 58
13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 59
13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . 59
14. Multiplexing Considerations for Encapsulating
Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 59
14.1. RFC3407 - cpar Attribute Analysis . . . . . . . . . . . 60
14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 60
14.2.1. Recommendation - Procedures for Potential
Configuration Pairing . . . . . . . . . . . . . . . 61
14.2.1.1. Example: Transport Capability Multiplexing . . . 62
14.2.1.2. Example: Attribute Capability Multiplexing . . . 63
14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 64
14.3.1. Recommendation: Dealing with Payload Type Numbers . 64
14.3.1.1. Example: Attribute Capability Under Shared
Payload Type . . . . . . . . . . . . . . . . . . 64
14.3.2. Recommendation: Dealing with Latent Configurations . 65
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 66
15.1. New Column 'Mux Category' . . . . . . . . . . . . . . . 66
15.2. 'Mux Category' values for SDP Registries . . . . . . . . 67
15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 67
15.2.2. Table: att-field . . . . . . . . . . . . . . . . . . 68
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15.2.3. Table: content SDP Parameters . . . . . . . . . . . 73
15.2.4. Table: Semantics for the 'group' SDP Attribute . . . 73
15.2.5. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 74
15.2.6. Table: 'ack' and 'nack' Attribute Values . . . . . . 74
15.2.7. Table: 'depend' SDP Attribute Values . . . . . . . . 75
15.2.8. Table: 'cs-correlation' Attribute Values . . . . . . 75
15.2.9. Table: Semantics for the 'ssrc-group' SDP Attribute 75
15.2.10. Table: SDP/RTSP key management protocol identifiers 76
15.2.11. Table: Codec Control Messages . . . . . . . . . . . 76
15.2.12. Table: QoS Mechanism Tokens . . . . . . . . . . . . 76
15.2.13. Table: SDP Capability Negotiation Option Tags . . . 77
15.2.14. Table: Timestamp Reference Clock Source Parameters . 77
15.2.15. Table: Media Clock Source Parameters . . . . . . . . 77
16. Security Considerations . . . . . . . . . . . . . . . . . . . 78
17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 78
18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 78
19. References . . . . . . . . . . . . . . . . . . . . . . . . . 80
19.1. Normative References . . . . . . . . . . . . . . . . . . 80
19.2. Informative References . . . . . . . . . . . . . . . . . 81
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 87
1. Introduction
Real-Time Communication Web (RTCWeb) framework requires Real-time
Transport Protocol (RTP) as the media transport protocol and Session
Description Protocol (SDP) [RFC4566] for describing and negotiating
multi-media communication sessions.
SDP defines several attributes for capturing characteristics that
apply to the individual media descriptions (described by "m=" lines")
and the overall multimedia session. Typically different media types
(audio, video etc) described using different media descriptions
represent separate RTP Sessions that are carried over individual
transport layer flows. However in the IETF RTCWEB WG, a need to use
a single 5-tuple for sending and receiving media associated with
multiple SDP media descriptions ("m=" lines) has been identified.
This would e.g. allow the usage of a single set of Interactive
Connectivity Establishment (ICE) [RFC5245] candidates for multiple
media descriptions. This in turn has made necessary to understand
the interpretation and usage of the SDP attributes defined for the
multiplexed media descriptions.
Given the number of SDP attributes registered with the IANA [IANA]
and possibility of new attributes being defined in the future, there
is need for generic future-proof framework to analyze these
attributes for their applicability in the transport multiplexing use-
cases.
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The document starts with providing the motivation for requiring such
a framework. This is followed by introduction to the SDP attribute
analysis framework/procedures, following which several sections
applies the framework to the SDP attributes registered with the IANA
[IANA]
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in [RFC2119].
3. Motivation
The time and complications of setting up ICE [RFC5245] and DTLS-SRTP
[RFC5763] transports for use by RTP, and conservation of ports, forms
an requirement to try and reduce the number of transport level flows
needed. This has resulted in the definition of ways, such as,
[I-D.ietf-mmusic-sdp-bundle-negotiation] to multiplex RTP over a
single transport flow in order to preserve network resources such as
port numbers. This imposes further restrictions on applicability of
these SDP attributes as they are defined today.
The specific problem is that there are attribute combinations which
make sense when specified on independent m-lines -- as with classical
SDP -- that do not make sense when those m-lines are then multiplexed
over the same transport. To give an obvious example, ICE permits
each m=line to have an independently specified ice-ufrag attribute.
However, if the media from multiple m-lines is multiplexed over the
same ICE component, then the meaning of media-level ice-ufrag
attributes becomes muddled.
As of today there are close to 250 SDP attributes registered with the
IANA [IANA] and more will be added in the future. There is no
clearly defined procedure to establish the validity/applicability of
these attribute when used with transport multiplexing.
4. SDP Attribute Analysis Framework
Attributes in an SDP session description can be defined at the
session-level and media-level. These attributes could be
semantically grouped as noted below.
o Attributes related to media content such as media type, encoding
schemes, payload types.
o Attributes specifying media transport characteristics like RTP/
RTCP port numbers, network addresses, QOS.
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o Metadata description attributes capturing session timing and
origin information.
o Attributes establishing relationships between media streams such
as grouping framework
With the above semantic grouping as the reference, the proposed
framework classifies each attribute into one of the following
categories:
4.1. Category: NORMAL
Attributes that can be independently specified when multiplexing and
retain their original semantics.
In the example given below, the direction and label attributes are
independently specified for audio and video m=lines. These
attributes are not impacted by multiplexing these media streams over
a single transport layer flow.
v=0
o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49172 RTP/AVP 99
a=sendonly
a=label:1
a=rtpmap:99 iLBC/8000
m=video 49172 RTP/AVP 31
a=recvonly
a=label:2
a=rtpmap:31 H261/90000
4.2. Category: NOT RECOMMENDED
Attributes that are recommended against multiplexing since their
usage under multiplexing might lead to incorrect behavior.
Example: Multiplexing media descriptions having attribute zrtp-hash
defined with the media descriptions lacking it, would either
complicate the handling of multiplexed streams or might fail
multiplexing altogether.
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v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 3456 RTP/AVP 97 // with zrtp
a=rtpmap:97 iLBC/8000
<allOneLine>
a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
df881ae642c371ba46df
</allOneLine>
m=video 34567 RTP/AVP 31 //without zrtp
a=rtpmap:31 H261/90000
4.3. Category: IDENTICAL
Attributes that MUST be identical across all the media descriptions
being multiplexed.
Attributes such as rtcp-mux fall into this category. Since RTCP
reporting is done per RTP Session, RTCP Multiplexing MUST to enabled
for both the audio and video m=lines in the example below if they are
transported over a single 5-tuple.
v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 34567 RTP/AVP 97
a=rtcp-mux
m=video 34567 RTP/AVP 31
a=rtpmap:31 H261/90000
a=rtcp-mux
4.4. Category: SUM
Attributes can be set as they are normally used but software using
them in a multiplex case, MUST apply the sum of all the attributes
being multiplexed instead of trying to use each one. This is
typically used for bandwidth or other rate limiting attributes to the
underlining transport.
The software parsing the SDP sample below, should use the aggregate
Application Specific (AS) bandwidth value from the individual media
descriptions to determine the AS value for the multiplexed session.
Thus the calculated AS value would be 256+64 bytes for the given
example.
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v=0
o=test 2890844526 2890842807 IN IP4 126.16.64.4
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 49170 RTP/AVP 0
b=AS:64
m=video 51372 RTP/AVP 31
b=AS:256
4.5. Category: TRANSPORT
Attributes that can be set normally for multiple items in a
multiplexed group but the software MUST pick just one of the
attribute of the given type for use. The one chosen is the attribute
associated with the "m=" line that represents the information being
used for the transport of the RTP.
In the example below, "a=crypto" attribute is defined for both the
audio and the video m=lines. The video media line's a=crypto
attribute is chosen since its mid value (bar) appears first in the
a=group:BUNDLE line. This is due to BUNDLE grouping semantic
[I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values
from m=line corresponding to the mid appearing first on the
a=group:BUNDLE line to be considered for setting up the RTP
Transport.
v=0
o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
a=group:BUNDLE bar foo
m=audio 49172 RTP/AVP 99
a=mid:foo
a=crypto:1 AES_CM_128_HMAC_SHA1_80
inline:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj|2^20|1:32
a=rtpmap:99 iLBC/8000
m=video 51374 RTP/AVP 31
a=mid:bar
a=crypto:1 AES_CM_128_HMAC_SHA1_80
inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
a=rtpmap:96 H261/90000
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4.6. Category: INHERIT
Attributes that encapsulate other SDP attributes or parameters.
These attributes inherit their multiplexing characteristics from the
attributes or parameters they encapsulate. Such attributes as of
today, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of a
generic framework for indicating and negotiating transport, media and
media format related capabilities in the SDP.
The inheritance manifests itself when the encapsulated attribute or
parameter is being leveraged. In the case of SDP Capability
Negotiation [RFC5939] for example, this occurs when a capability
(encapsulating attribute) is used as part of a configuration; the
configuration inherits the multiplexing Category of each of its
constituent (encapsulated) attributes and parameters. This in turn
may place constraints on what constitutes a valid configuartion from
a multiplexing point of view, e.g. because some attributes must be
IDENTICAL (see Section 15 for further details).
v=0
o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=video 3456 RTP/AVP 100
a=rtpmap:100 VP8/90000
a=fmtp:100 max-fr=30;max-fs=8040
a=sqn: 0
a=cdsc: 1 video RTP/AVP 100
a=cpar: a=rtcp-mux
m=video 3456 RTP/AVP 101
a=rtpmap:101 VP8/90000
a=fmtp:100 max-fr=15;max-fs=1200
a=cdsc: 2 video RTP/AVP 101
a=cpar: a=rtcp-mux
In the above example , the category IDENTICAL is inherited for the
cpar encapsulated rtcp-mux attribute.
4.7. Category: IDENTICAL-PER-PT
Attributes that define the RTP payload configuration on per Payload
Type basis and MUST have identical values across all the media
descriptions for a given RTP Payload Type when repeated.
In the SDP example below, Payload Types 96 and 97 are repeated across
all the video m= lines and all the payload specific parameters (ex:
rtpmap, fmtp) are identical.
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v=0
o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
a=group:BUNDLE cam1, cam2
m = video 96 97
a=mid:cam1
a=rtpmap:96 H264/90000
a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
max-mbps=108000; max-br=1000
a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
max-mbps=7200; max-br=200
m = video 96 97
a=mid:cam2
a=rtpmap:96 H264/90000
a=fmtp:96 profile-level-id=42400d; max-fs=3600; max-fps=3000;
max-mbps=108000; max-br=1000
a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=42400a; max-fs=240; max-fps=3000;
max-mbps=7200; max-br=200
4.8. Category: SPECIAL
Attributes where the text in the source draft must be consulted for
further handling when multiplexed.
As an example, for the attribute extmap, the specification defining
the extension MUST be referred to understand the multiplexing
implications.
4.9. Category: TBD
Attributes that have not been analyzed under the proposed
multiplexing framework yet.
5. Analysis of Existing Attributes
This section analyzes attributes listed in IANA [IANA] grouped under
the IETF document that defines them. The "Level" column indicates
whether the attribute is currently specified as:
o S -- Session level
o M -- Media level
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o B -- Both
o SR -- Source-level (for a single SSRC)
5.1. RFC4566 - SDP: Session Description Protocol
[RFC4566] defines the Session Description Protocol (SDP) that is
intended for describing multimedia sessions for the purposes of
session announcement, session invitation, and other forms of
multimedia session initiation
+-----------------+---------------------+-------+-------------------+
| Attr Name | Notes | Level | Category |
+-----------------+---------------------+-------+-------------------+
| sendrecv | Not impacted | B | NORMAL |
| | | | |
| sendonly | Not impacted | B | NORMAL |
| | | | |
| recvonly | Not impacted | B | NORMAL |
| | | | |
| inactive | Not impacted | B | NORMAL |
| | | | |
| cat | Not impacted | S | NORMAL |
| | | | |
| ptime | The attribute value | M | IDENTICAL-PER-PT |
| | must be same for a | | |
| | given codec | | |
| | configuration | | |
| | | | |
| maxptime | The attribute value | M | IDENTICAL-PER-PT |
| | must be same for a | | |
| | given codec | | |
| | configuration | | |
| | | | |
| orient | Not Impacted | M | NORMAL |
| | | | |
| framerate | The attribute value | M | IDENTICAL-PER-PT |
| | must be same for a | | |
| | given codec | | |
| | configuration | | |
| | | | |
| quality | Not Impacted | M | NORMAL |
| | | | |
| rtpmap | The attribute value | M | IDENTICAL-PER-PT |
| | must be same for a | | |
| | given codec | | |
| | configuration | | |
| | | | |
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| fmtp | The attribute value | M | IDENTICAL-PER-PT |
| | must be same for a | | |
| | given codec | | |
| | configuration | | |
| | | | |
| keywds | Not impacted | S | NORMAL |
| | | | |
| type | Not Impacted | S | NORMAL |
| | | | |
| type:broadcast | Not Impacted | S | NORMAL |
| | | | |
| type:H332 | Not Impacted | S | NORMAL |
| | | | |
| type:meeting | Not Impacted | S | NORMAL |
| | | | |
| type:moderated | Not Impacted | S | NORMAL |
| | | | |
| type:test | Not Impacted | S | NORMAL |
| | | | |
| tool | Not Impacted | S | NORMAL |
| | | | |
| charset | Not Impacted | S | NORMAL |
| | | | |
| sdplang | Not Impacted | B | NORMAL |
| | | | |
| lang | Not Impacted | B | NORMAL |
| | | | |
+-----------------+---------------------+-------+-------------------+
RFC4566 Attribute Analysis
5.2. RFC4585 - RTP/AVPF
[RFC4585] defines an extension to the Audio-visual Profile (AVP) that
enables receivers to provide, statistically, more immediate feedback
to the senders and thus allows for short-term adaptation and
efficient feedback-based repair mechanisms to be implemented.
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+----------+----------------------------+-------+-------------------+
| Attr | Notes | Level | Category |
| Name | | | |
+----------+----------------------------+-------+-------------------+
| rtcp-fb | Since RTCP feedback | M | IDENTICAL-PER-PT |
| | attributes are Payload | | |
| | Type (PT) scoped, their | | |
| | values MUST be identical | | |
| | for a given PT across the | | |
| | multiplexed m=lines. | | |
| | | | |
+----------+----------------------------+-------+-------------------+
RFC4585 Attribute Analysis
5.3. RFC5761 - Multiplexing RTP and RTCP
[RFC5761] discusses issues that arise when multiplexing RTP data
packets and RTP Control Protocol (RTCP) packets on a single UDP port.
It describes when such multiplexing is and is not appropriate, and it
explains how the Session Description Protocol (SDP) can be used to
signal multiplexed sessions.
+-----------+----------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-----------+----------------------------------+-------+------------+
| rtcp-mux | RTP and RTCP Multiplexing | M | IDENTICAL |
| | affects the entire RTP Session | | |
| | | | |
+-----------+----------------------------------+-------+------------+
RFC5761 Attribute Analysis
5.4. RFC3312 - Integration of Resource Management and (SIP)
[RFC3312] defines a generic framework for preconditions, which are
extensible through IANA registration. This document also discusses
how network quality of service can be made a precondition for
establishment of sessions initiated by the Session Initiation
Protocol (SIP). These preconditions require that the participant
reserve network resources before continuing with the session.
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+-------+-----------------------+-------+-----------------+
| Name | Notes | Level | Category |
+-------+-----------------------+-------+-----------------+
| des | Refer to notes below | M | NOT RECOMMEDED |
| | | | |
| conf | Refer to notes below | M | NOT RECOMMEDED |
| | | | |
| curr | Refer to notes below | M | NOT RECOMMEDED |
| | | | |
+-------+-----------------------+-------+-----------------+
RFC3312 Attribute Analysis
A mismatched set of Preconditions across media descriptions results
in Session establishment failures due to inability to meet the right
resource reservations requested.
5.5. RFC4574 - SDP Label Attribute
[RFC4574] defines a new Session Description Protocol (SDP) media-
level attribute: "label". The "label" attribute carries a pointer to
a media stream in the context of an arbitrary network application
that uses SDP. The sender of the SDP document can attach the "label"
attribute to a particular media stream or streams. The application
can then use the provided pointer to refer to each particular media
stream in its context.
+--------+---------------+-------+----------+
| Name | Notes | Level | Category |
+--------+---------------+-------+----------+
| label | Not Impacted | M | NORMAL |
| | | | |
+--------+---------------+-------+----------+
RFC4574 Attribute Analysis
5.6. RFC5432 - QoS Mechanism Selection in SDP
[RFC5432] defines procedures to negotiate QOS mechanisms using the
Session Description Protocol (SDP) offer/answer model.
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+----------------+-------------------------------+-------+----------+
| Name | Notes | Level | Category |
+----------------+-------------------------------+-------+----------+
| qos-mech-send | A single DSCP code point per | B | NORMAL |
| | flow being multiplexed | | |
| | doesn't impact multiplexing | | |
| | since QOS mechanisms are | | |
| | signaled/scoped per flow. | | |
| | | | |
| qos-mech-recv | A single DSCP code point per | B | NORMAL |
| | flow being multiplexed | | |
| | doesn't impact multiplexing | | |
| | since QOS mechanisms are | | |
| | signaled/scoped per flow. | | |
| | | | |
+----------------+-------------------------------+-------+----------+
RFC5432 Attribute Analysis
For scenarios that involves having different DSCP for packets being
transmitted over the same 5-tuple, i.e. what is being in the same
bundle, has issues as discussed in [I.D-draft-ietf-dart-dscp-rtp]
5.7. RFC4568 - SDP Security Descriptions
[RFC4568] defines a Session Description Protocol (SDP) cryptographic
attribute for unicast media streams. The attribute describes a
cryptographic key and other parameters that serve to configure
security for a unicast media stream in either a single message or a
roundtrip exchange.
+---------+------------------------------------+-------+------------+
| Name | Notes | Level | Category |
+---------+------------------------------------+-------+------------+
| crypto | crypto attribute must be the one | M | TRANSPORT |
| | that corresponds to the m=line | | |
| | chosen for setting up the | | |
| | underlying transport flow | | |
| | | | |
+---------+------------------------------------+-------+------------+
RFC4568 Attribute Analysis
5.8. RFC5762 - RTP over DCCP
The Real-time Transport Protocol (RTP) is a widely used transport for
real-time multimedia on IP networks. The Datagram Congestion Control
Protocol (DCCP) is a transport protocol that provides desirable
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services for real-time applications. [RFC5762] specifies a mapping
of RTP onto DCCP, along with associated signaling, such that real-
time applications can make use of the services provided by DCCP
+--------------------+---------------------+---------+--------------+
| Name | Notes | Current | Category |
+--------------------+---------------------+---------+--------------+
| dccp-service-code | If RFC6773 is not | M | NOT |
| | being used in | | RECOMMENDED |
| | addition to | | |
| | RFC5762, the port | | |
| | in the m= line is a | | |
| | DCCP port. DCCP | | |
| | being a connection | | |
| | oriented protocol, | | |
| | does not allow | | |
| | multiple | | |
| | connections on the | | |
| | same 5-tuple. | | |
| | | | |
+--------------------+---------------------+---------+--------------+
RFC5762 Attribute Analysis
If RFC6773 is being used in addition to RFC5762 and provided that
DCCP-in-UDP layer has additional demultiplexing, then it may be
possible to use different DCCP service codes for each DCCP flow,
given each uses a different DCCP port. Although doing so might
conflict with the media type of the m= line. None of this is
standardized yet and it wouldn't work as explained. Hence
multiplexing MUST NOT be performed even in this alternate scenario.
5.9. RFC6773 - DCCP-UDP Encapsulation
[RFC6773] document specifies an alternative encapsulation of the
Datagram Congestion Control Protocol (DCCP), referred to as DCCP-UDP.
This encapsulation allows DCCP to be carried through the current
generation of Network Address Translation (NAT) middle boxes without
modification of those middle boxes
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+------------+-------------------------------+-------+--------------+
| Name | Notes | Level | Category |
+------------+-------------------------------+-------+--------------+
| dccp-port | Multiplexing MUST NOT be | M | NOT |
| | performed due to potential | | RECOMMENDED |
| | conflict between the port | | |
| | used for DCCP | | |
| | en/decapsulation and the RTP. | | |
| | | | |
+------------+-------------------------------+-------+--------------+
RFC6773 Attribute Analysis
Since RFC6773 is about tunnelling DCCP in UDP, with the UDP port
being the port of the DCCP en-/de-capsulation service. This
encapsulation allows arbitrary DCCP packets to be encapsulated and
the DCCP port choosen MAY conflict with the port chosen for the RTP
traffic.
For multiplexing several DCCP-in-UDP encapsulations on the same UDP
port, with no RTP traffic on the same port implies collapsing several
DCCP port spaces together. This MAY or MAY NOT work depending on the
nature of DCCP encapsulations and ports choses thus rendering it to
be very application dependant.
5.10. RFC5506 - Reduced-Size RTCP in RTP Profile
[RFC5506] discusses benefits and issues that arise when allowing
Real-time Transport Protocol (RTCP) packets to be transmitted with
reduced size.
+-------------+--------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------------+--------------------------------+-------+------------+
| rtcp-rsize | Reduced size RTCP affects the | M | IDENTICAL |
| | entire RTP Session | | |
| | | | |
+-------------+--------------------------------+-------+------------+
RFC5506 Attribute Analysis
5.11. RFC6787 - Media Resource Control Protocol Version 2
The Media Resource Control Protocol Version 2 (MRCPv2) allows client
hosts to control media service resources such as speech synthesizers,
recognizers, verifiers, and identifiers residing in servers on the
network. MRCPv2 is not a "stand-alone" protocol -- it relies on
other protocols, such as the Session Initiation Protocol (SIP), to
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coordinate MRCPv2 clients and servers and manage sessions between
them, and the Session Description Protocol (SDP) to describe,
discover, and exchange capabilities. It also depends on SIP and SDP
to establish the media sessions and associated parameters between the
media source or sink and the media server. Once this is done, the
MRCPv2 exchange operates over the control session established above,
allowing the client to control the media processing resources on the
speech resource server. [RFC6787] defines attributes for this
purpose.
+-----------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-----------+---------------+-------+----------+
| resource | Not Impacted | M | NORMAL |
| | | | |
| channel | Not Impacted | M | NORMAL |
| | | | |
+-----------+---------------+-------+----------+
RFC6787 Attribute Analysis
5.12. RFC5245 - Interactive Connectivity Establishment (ICE)
[RFC5245] describes a protocol for Network Address Translator(NAT)
traversal for UDP-based multimedia sessions established with the
offer/answer model. This protocol is called Interactive Connectivity
Establishment (ICE). ICE makes use of the Session Traversal
Utilities for NAT (STUN) protocol and its extension,Traversal Using
Relay NAT (TURN). ICE can be used by any protocol utilizing the
offer/answer model, such as the Session Initiation Protocol (SIP).
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+--------------------+-------------------------+-------+------------+
| Name | Notes | Level | Category |
+--------------------+-------------------------+-------+------------+
| ice-lite | Not Impacted | S | NORMAL |
| | | | |
| ice-options | Not Impacted | S | NORMAL |
| | | | |
| ice-mismatch | Not Impacted | S | NORMAL |
| | | | |
| ice-pwd | ice-pwd MUST be the one | B | TRANSPORT |
| | that corresponds to the | | |
| | m=line chosen for | | |
| | setting up the | | |
| | underlying transport | | |
| | flow | | |
| | | | |
| ice-ufrag | ice-ufrag MUST be the | B | TRANSPORT |
| | one that corresponds to | | |
| | the m=line chosen for | | |
| | setting up the | | |
| | underlying transport | | |
| | flow | | |
| | | | |
| candidate | ice candidate MUST be | M | TRANSPORT |
| | the one that | | |
| | corresponds to the | | |
| | m=line chosen for | | |
| | setting up the | | |
| | underlying transport | | |
| | flow | | |
| | | | |
| remote-candidates | ice remote candidate | M | TRANSPORT |
| | MUST be the one that | | |
| | corresponds to the | | |
| | m=line chosen for | | |
| | setting up the | | |
| | underlying transport | | |
| | flow | | |
| | | | |
+--------------------+-------------------------+-------+------------+
RFC5245 Attribute Analysis
5.13. RFC5285 - RTP Header Extensions
[RFC5285] provides a general mechanism to use the header extension
feature of RTP (the Real-Time Transport Protocol). It provides the
option to use a small number of small extensions in each RTP packet,
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where the universe of possible extensions is large and registration
is de-centralized. The actual extensions in use in a session are
signaled in the setup information for that session.
+---------+--------------------------------------+-------+----------+
| Name | Notes | Level | Category |
+---------+--------------------------------------+-------+----------+
| extmap | Specific RTP extension document MUST | B | SPECIAL |
| | be referred | | |
| | | | |
+---------+--------------------------------------+-------+----------+
RFC5285 Attribute Analysis
5.14. RFC3605 - RTCP attribute in SDP
Originally, SDP assumed that RTP and RTCP were carried on consecutive
ports. However, this is not always true when NATs are involved.
[RFC3605] specifies an early mechanism to indicate the RTCP port.
+-------+--------------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------+--------------------------------------+-------+------------+
| rtcp | Identical attribute value MUST be | M | IDENTICAL |
| | used since the RTCP port affects the | | |
| | entire RTP session. | | |
| | | | |
+-------+--------------------------------------+-------+------------+
RFC3605 Attribute Analysis
5.15. RFC5576 - Source-Specific SDP Attributes
[RFC5576] defines a mechanism to describe RTP media sources, which
are identified by their synchronization source (SSRC) identifiers, in
SDP, to associate attributes with these sources, and to express
relationships among sources. It also defines several source-level
attributes that can be used to describe properties of media sources.
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+----------------+----------------------+-------+-------------------+
| Name | Notes | Level | Category |
+----------------+----------------------+-------+-------------------+
| ssrc | Refer to Notes below | M | NORMAL |
| | | | |
| ssrc-group | Refer to section | M | SPECIAL |
| | Section 9 for | | |
| | specific analysis of | | |
| | the grouping | | |
| | semantics | | |
| | | | |
| cname | Not Impacted [Open | SR | NORMAL |
| | Issues: what are the | | |
| | rules for CNAME | | |
| | duplication across | | |
| | sessions?] | | |
| | | | |
| previous-ssrc | Refer to notes below | SR | NORMAL |
| | | | |
| fmtp | The attribute value | SR | IDENTICAL-PER-PT |
| | must be same for a | | |
| | given codec | | |
| | configuration | | |
| | | | |
+----------------+----------------------+-------+-------------------+
RFC5576 Attribute Analysis
If SSRCs are repeated across m=lines being multiplexed, they MUST all
represent the same underlying RTP Source.
5.16. RFC7273 - RTP Clock Source Signalling
[RFC7273] specifies Session Description Protocol (SDP) signalling
that identifies timestamp reference clock sources and SDP signalling
that identifies the media clock sources in a multimedia session.
+------------+---------------+-----------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-----------+----------+
| ts-refclk | Not Impacted | S, M, SR | NORMAL |
| | | | |
| mediaclk | Not Impacted | S,, M, SR | NORMAL |
| | | | |
+------------+---------------+-----------+----------+
RFC7273 Attribute Analysis
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5.17. RFC6236 - Image Attributes in SDP
[RFC6236] proposes a new generic session setup attribute to make it
possible to negotiate different image attributes such as image size.
A possible use case is to make it possible for a low-end hand-held
terminal to display video without the need to rescale the
image,something that may consume large amounts of memory and
processing power. The document also helps to maintain an optimal
bitrate for video as only the image size that is desired by the
receiver is transmitted.
+------------+--------------------------+-------+-------------------+
| Name | Notes | Level | Category |
+------------+--------------------------+-------+-------------------+
| imageattr | The attribute value must | M | IDENTICAL-PER-PT |
| | be same for a given | | |
| | codec configuration | | |
| | | | |
+------------+--------------------------+-------+-------------------+
RFC6236 Attribute Analysis
5.18. RFC7197 - Duplication Delay Attribute in SDP
[RFC7197] defines an attribute to indicate the presence of temporally
redundant media streams and the duplication delay in the Session
Description Protocol
+--------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+--------------------+---------------+-------+----------+
| duplication-delay | Not Impacted | B | NORMAL |
| | | | |
+--------------------+---------------+-------+----------+
RFC7197 Attribute Analysis
5.19. RFC7226 - RTCP XR Blocks for MOS Metric Reporting
[RFC7226] defines an RTP Control Protocol (RTCP) Extended Report (XR)
Block including two new segment types and associated Session
Description Protocol (SDP) parameters that allow the reporting of
mean opinion score (MOS) Metrics for use in a range of RTP
applications.
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+-------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-------------+---------------+-------+----------+
| calgextmap | Not Impacted | B | NORMAL |
| | | | |
+-------------+---------------+-------+----------+
RFC7226 Attribute Analysis
5.20. RFC6285 - Rapid Acquisition of Multicast RTP Sessions
[RFC6285] describes a method using the existing RTP and RTP Control
Protocol (RTCP) machinery that reduces the acquisition delay. In
this method, an auxiliary unicast RTP session carrying the Reference
Information to the receiver precedes or accompanies the multicast
stream. This unicast RTP flow can be transmitted at a faster than
natural bitrate to further accelerate the acquisition. The
motivating use case for this capability is multicast applications
that carry real-time compressed audio and video.
+---------------+-------------------+-------+------------------+
| Name | Notes | Level | Category |
+---------------+-------------------+-------+------------------+
| rams-updates | Not recommended | M | NOT RECOMMENDED |
| | | | |
+---------------+-------------------+-------+------------------+
RFC6285 Attribute Analysis
5.21. RFC6230 - Media Control Channel Framework
[RFC6230] describes a framework and protocol for application
deployment where the application programming logic and media
processing are distributed. This implies that application
programming logic can seamlessly gain access to appropriate resources
that are not co-located on the same physical network entity. The
framework uses the Session Initiation Protocol (SIP) to establish an
application-level control mechanism between application servers and
associated external servers such as media servers.
+---------+-----------------+-------+----------+
| Name | Notes | Level | Category |
+---------+-----------------+-------+----------+
| cfw-id | Not Applicable | M | NORMAL |
| | | | |
+---------+-----------------+-------+----------+
RFC6230 Attribute Analysis
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5.22. RFC6364 - SDP Elements for FEC Framework
[RFC6364] specifies the use of the Session Description Protocol (SDP)
to describe the parameters required to signal the Forward Error
Correction (FEC) Framework Configuration Information between the
sender(s) and receiver(s). This document also provides examples that
show the semantics for grouping multiple source and repair flows
together for the applications that simultaneously use multiple
instances of the FEC Framework.
+------------------+-------+-------+----------+
| Name | Notes | Level | Category |
+------------------+-------+-------+----------+
| fec-source-flow | | M | SPECIAL |
| | | | |
| fec-repair-flow | | M | SPECIAL |
| | | | |
| repair-window | | M | SPECIAL |
| | | | |
+------------------+-------+-------+----------+
RFC6364 Attribute Analysis
5.23. RFC4796 - Content Attribute
[RFC4796] defines a new Session Description Protocol (SDP) media-
level attribute, 'content'. The 'content' attribute defines the
content of the media stream to a more detailed level than the media
description line. The sender of an SDP session description can
attach the 'content' attribute to one or more media streams. The
receiving application can then treat each media stream differently
(e.g., show it on a big or small screen) based on its content.
+----------+---------------+-------+----------+
| Name | Notes | Level | Category |
+----------+---------------+-------+----------+
| content | Not Impacted | M | NORMAL |
| | | | |
+----------+---------------+-------+----------+
RFC4796 Attribute Analysis
5.24. RFC3407 - SDP Simple Capability Declaration
[RFC3407] defines a set of Session Description Protocol (SDP)
attributes that enables SDP to provide a minimal and backwards
compatible capability declaration mechanism.
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+----------+------------------------+-------+----------+
| Name | Notes | Level | Category |
+----------+------------------------+-------+----------+
| sqn | Not Impacted | B | NORMAL |
| | | | |
| cdsc | Not Impacted. | B | NORMAL |
| | | | |
| cpar | Refer to Section 14 | B | INHERIT |
| | | | |
| cparmin | Refer to notes below | B | SPECIAL |
| | | | |
| cparmax | Refer to notes below | B | SPECIAL |
| | | | |
+----------+------------------------+-------+----------+
RFC3407 Attribute Analysis
Since the attributes (a=cparmin and a=cparmax) define minimum and
maximum numerical values associated with the attributes described in
a=cpar, it is recommended to consult the document defining the
attribute for dealing under media stream multiplexing.
5.25. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions
[RFC6284] presents a port mapping solution that allows RTP receivers
to choose their own ports for an auxiliary unicast session in RTP
applications using both unicast and multicast services. The solution
provides protection against denial-of-service or packet amplification
attacks that could be used to cause one or more RTP packets to be
sent to a victim client
+------------------+-------------------------+-------+--------------+
| Name | Notes | Level | Category |
+------------------+-------------------------+-------+--------------+
| portmapping-req | Not recommended, if | M | NOT |
| | port mapping is | | RECOMMENDED |
| | required by the | | |
| | application | | |
| | | | |
+------------------+-------------------------+-------+--------------+
RFC6284 Attribute Analysis
5.26. RFC6714 - MSRP-CEMA
[RFC6714] defines a Message Session Relay Protocol (MSRP) extension,
Connection Establishment for Media Anchoring (CEMA). Support of this
extension is OPTIONAL. The extension allows middle boxes to anchor
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the MSRP connection, without the need for middle boxes to modify the
MSRP messages; thus, it also enables secure end-to-end MSRP
communication in networks where such middle boxes are deployed. This
document also defines a Session Description Protocol (SDP) attribute,
'msrp-cema', that MSRP endpoints use to indicate support of the CEMA
extension.
+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| msrp-cema | Not Impacted | M | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC6714 Attribute Analysis
5.27. RFC4583 - SDP Format for BFCP Streams
[RFC4583] document specifies how to describe Binary Floor Control
Protocol (BFCP) streams in Session Description Protocol (SDP)
descriptions. User agents using the offer/answer model to establish
BFCP streams use this format in their offers and answers
+------------+---------------------------------+-------+------------+
| Name | Notes | Level | Category |
+------------+---------------------------------+-------+------------+
| floorctrl | Must be repeated across all the | M | IDENTICAL |
| | multiplexed m=lines | | |
| | | | |
| confid | Not Impacted | M | NORMAL |
| | | | |
| userid | Not Impacted | M | NORMAL |
| | | | |
| floorid | The floorid MUST be globally | M | NORMAL |
| | unique | | |
| | | | |
+------------+---------------------------------+-------+------------+
RFC4583 Attribute Analysis
5.28. RFC5547 - SDP Offer/Answer for File Transfer
[RFC5547] provides a mechanism to negotiate the transfer of one or
more files between two endpoints by using the Session Description
Protocol (SDP) offer/answer model specified in [RFC3264].
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+----------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+----------------------+---------------+-------+----------+
| file-selector | Not Impacted | M | NORMAL |
| | | | |
| file-transfer-id | Not Impacted | M | NORMAL |
| | | | |
| file-disposition | Not Impacted | M | NORMAL |
| | | | |
| file-date | Not Impacted | M | NORMAL |
| | | | |
| file-iconfile-range | Not Impacted | M | NORMAL |
| | | | |
+----------------------+---------------+-------+----------+
RFC5547 Attribute Analysis
5.29. RFC6489 - SDP and RTP Media Loopback Extension
[RFC6489] adds new SDP media types and attributes, which enable
establishment of media sessions where the media is looped back to the
transmitter. Such media sessions will serve as monitoring and
troubleshooting tools by providing the means for measurement of more
advanced VoIP, Real-time Text and Video over IP performance metrics.
+------------------------------+----------------+-------+----------+
| Name | Notes | Level | Category |
+------------------------------+----------------+-------+----------+
| loopback rtp-pkt-loopback | Not Impacted | M | NORMAL |
| | | | |
| loopback rtp-media-loopback | Not Impacted | M | NORMAL |
| | | | |
| loopback-source | Not Impacted | M | NORMAL |
| | | | |
| loopback-mirror | Not Impacted | M | NORMAL |
| | | | |
+------------------------------+----------------+-------+----------+
An Extension to the Session Description Protocol (SDP) and Real-time
Transport Protocol (RTP) for Media Loopback
5.30. RFC5760 - RTCP with Unicast Feedback
[RFC5760] specifies an extension to the Real-time Transport Control
Protocol (RTCP) to use unicast feedback to a multicast sender. The
proposed extension is useful for single-source multicast sessions
such as Source-Specific Multicast (SSM) communication where the
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traditional model of many-to-many group communication is either not
available or not desired.
+---------------+------------------------------+-------+------------+
| Name | Notes | Level | Category |
+---------------+------------------------------+-------+------------+
| rtcp-unicast | The attribute MUST be | M | IDENTICAL |
| | reported across all m=lines | | |
| | multiplexed | | |
| | | | |
+---------------+------------------------------+-------+------------+
RFC5760 Attribute Analysis
5.31. RFC3611 - RTCP XR
[RFC3611] defines the Extended Report (XR) packet type for the RTP
Control Protocol (RTCP), and defines how the use of XR packets can be
signaled by an application if it employs the Session Description
Protocol (SDP).
+----------+---------------+-------+----------+
| Name | Notes | Level | Category |
+----------+---------------+-------+----------+
| rtcp-xr | Not Impacted | B | NORMAL |
| | | | |
+----------+---------------+-------+----------+
RFC3611 Attribute Analysis
5.32. RFC5939 - SDP Capability Negotiation
[RFC5939] defines a general SDP Capability Negotiation framework. It
also specifies how to provide attributes and transport protocols as
capabilities and negotiate them using the framework. Extensions for
other types of capabilities (e.g., media types and media formats) may
be provided in other documents.
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+---------+-------------------------------+-------+----------+
| Name | Notes | Level | Category |
+---------+-------------------------------+-------+----------+
| pcfg | Refer to Section Section 14 | M | SPECIAL |
| | | | |
| acfg | Refer to Section Section 14 | M | SPECIAL |
| | | | |
| csup | Not Impacted | B | NORMAL |
| | | | |
| creq | Not Impacted | B | NORMAL |
| | | | |
| acap | Refer to section Section 14 | B | INHERIT |
| | | | |
| tcap | Refer to section Section 14 | B | INHERIT |
| | | | |
| cap-v0 | Not Impacted | B | NORMAL |
| | | | |
+---------+-------------------------------+-------+----------+
RFC5939 Attribute Analysis
5.33. RFC6871- SDP Media Capabilities Negotiation
Session Description Protocol (SDP) capability negotiation provides a
general framework for indicating and negotiating capabilities in SDP.
The base framework defines only capabilities for negotiating
transport protocols and attributes. [RFC6871] extends the framework
by defining media capabilities that can be used to negotiate media
types and their associated parameters.
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+---------+-----------------------------+-------+-------------------+
| Name | Notes | Level | Category |
+---------+-----------------------------+-------+-------------------+
| rmcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
| | | | |
| omcap | Not Impacted | B | NORMAL |
| | | | |
| mfcap | Refer to Section Section 14 | B | IDENTICAL-PER-PT |
| | | | |
| mscap | Refer to Section Section 14 | B | INHERIT |
| | | | |
| lcfg | Refer to Section Section 14 | B | SPECIAL |
| | | | |
| sescap | Refer to Section Section 14 | S | NOT RECOMMENDED |
| | | | |
| med-v0 | Not Impacted | S | NORMAL |
| | | | |
+---------+-----------------------------+-------+-------------------+
Session Description Protocol (SDP) Media Capabilities Negotiation
The "sescap" attribute is NOT RECOMMENDED for use with multiplexing.
The reason is that it requires the use of unique configuration
numbers across the entire SDP (per [RFC6871] as opposed to within a
media description only (per [RFC5939]). As described in Section 15,
the use of identical configuration numbers between multiplxed
(bundled) media descriptions is the default way of indicating
compatible configurations in a bundle.
5.34. RFC7006 - Miscellaneous Capabilities Negotiation SDP
[RFC7006] extends the SDP capability negotiation framework to allow
endpoints to negotiate three additional SDP capabilities. In
particular, this memo provides a mechanism to negotiate bandwidth
("b=" line), connection data ("c=" line), and session or media titles
("i=" line for each session or media).
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+----------+-----------------------------------+-------+------------+
| Name | Notes | Level | Category |
+----------+-----------------------------------+-------+------------+
| bcap | Inherit the category SUM as | B | INHERIT |
| | applicable to b= attribute | | |
| | | | |
| bcap-v0 | Not Impacted | B | NORMAL |
| | | | |
| ccap | The connection address type MUST | B | IDENTICAL |
| | be identical across all the | | |
| | multiplexed m= lines. | | |
| | | | |
| ccap-v0 | Not Impacted. | B | NORMAL |
| | | | |
| icap | Not Impacted | B | NORMAL |
| | | | |
| icap-v0 | Not Impacted | B | NORMAL |
| | | | |
+----------+-----------------------------------+-------+------------+
Miscellaneous Capabilities Negotiation in the Session Description
Protocol (SDP)
5.35. RFC4567 - Key Management Extensions for SDP and RTSP
[RFC4567] defines general extensions for Session Description Protocol
(SDP) and Real Time Streaming Protocol (RTSP) to carry messages, as
specified by a key management protocol, in order to secure the media.
These extensions are presented as a framework, to be used by one or
more key management protocols. As such, their use is meaningful only
when complemented by an appropriate key management protocol.
+-----------+----------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-----------+----------------------------------+-------+------------+
| key-mgmt | Key management protocol MUST be | B | IDENTICAL |
| | identical across all the m=lines | | |
| | | | |
| mikey | Key management protocol MUST be | B | IDENTICAL |
| | identical across all the m=lines | | |
| | | | |
+-----------+----------------------------------+-------+------------+
RFC4567 Attribute Analysis
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5.36. RFC4572 - Comedia over TLS in SDP
[RFC4572] specifies how to establish secure connection-oriented media
transport sessions over the Transport Layer Security (TLS) protocol
using the Session Description Protocol (SDP). It defines a new SDP
protocol identifier, 'TCP/TLS'. It also defines the syntax and
semantics for an SDP 'fingerprint' attribute that identifies the
certificate that will be presented for the TLS session. This
mechanism allows media transport over TLS connections to be
established securely, so long as the integrity of session
descriptions is assured.
+--------------+-------------------------------+-------+------------+
| Name | Notes | Level | Category |
+--------------+-------------------------------+-------+------------+
| fingerprint | Fingerprint value from the | B | TRANSPORT |
| | m=line defining the | | |
| | underlying transport is | | |
| | chosen | | |
| | | | |
+--------------+-------------------------------+-------+------------+
RFC4572 Attribute Analysis
5.37. RFC4570 - SDP Source Filters
[RFC4570] describes how to adapt the Session Description Protocol
(SDP) to express one or more source addresses as a source filter for
one or more destination "connection" addresses. It defines the
syntax and semantics for an SDP "source-filter" attribute that may
reference either IPv4 or IPv6 address(es) as either an inclusive or
exclusive source list for either multicast or unicast destinations.
In particular, an inclusive source-filter can be used to specify a
Source-Specific Multicast (SSM) session
+----------------+-----------------------------+-------+------------+
| Name | Notes | Level | Category |
+----------------+-----------------------------+-------+------------+
| source-filter | The attribute MUST be | B | IDENTICAL |
| | repeated across all m=lines | | |
| | multiplexed | | |
| | | | |
+----------------+-----------------------------+-------+------------+
RFC4570 Attribute Analysis
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5.38. RFC6128 - RTCP Port for Multicast Sessions
The Session Description Protocol (SDP) has an attribute that allows
RTP applications to specify an address and a port associated with the
RTP Control Protocol (RTCP) traffic. In RTP-based source-specific
multicast (SSM) sessions, the same attribute is used to designate the
address and the RTCP port of the Feedback Target in the SDP
description. However, the RTCP port associated with the SSM session
itself cannot be specified by the same attribute to avoid ambiguity,
and thus, is required to be derived from the "m=" line of the media
description. Deriving the RTCP port from the "m=" line imposes an
unnecessary restriction. [RFC6128] removes this restriction by
introducing a new SDP attribute.
+-----------------+----------------------------+-------+------------+
| Name | Notes | Level | Category |
+-----------------+----------------------------+-------+------------+
| multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL |
| | be identical across all | | |
| | the m=lines | | |
| | | | |
+-----------------+----------------------------+-------+------------+
RFC6128 Attribute Analysis
5.39. RFC6189 - ZRTP
[RFC6189] defines ZRTP, a protocol for media path Diffie-Hellman
exchange to agree on a session key and parameters for establishing
unicast Secure Real-time Transport Protocol (SRTP) sessions for Voice
over IP (VoIP) applications.
+------------+-------------------------------+-------+--------------+
| Name | Notes | Level | Category |
+------------+-------------------------------+-------+--------------+
| zrtp-hash | Complicates if all the | M | NOT |
| | m=lines are not authenticated | | RECOMMENDED |
| | as given in the example below | | |
| | | | |
+------------+-------------------------------+-------+--------------+
RFC6189 Attribute Analysis
Example: Multiplexing media descriptions having attribute zrtp-hash
defined with the media descriptions lacking it, would either
complicate the handling of multiplexed stream or fail multiplexing.
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v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 3456 RTP/AVP 97
a=rtpmap:97 iLBC/8000
<allOneLine>
a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
df881ae642c371ba46df
</allOneLine>
m=video 34567 RTP/AVP 31
a=rtpmap:31 H261/90000
5.40. RFC4145 - Connection-Oriented Media
[RFC4145] describes how to express media transport over TCP using the
Session Description Protocol (SDP). It defines the SDP 'TCP'
protocol identifier, the SDP 'setup' attribute, which describes the
connection setup procedure, and the SDP 'connection' attribute, which
handles connection reestablishment.
+-------------+--------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------------+--------------------------------+-------+------------+
| setup | MUST be identical across all | B | IDENTICAL |
| | m=lines | | |
| | | | |
| connection | MUST be identical across all | B | IDENTICAL |
| | m=lines | | |
| | | | |
+-------------+--------------------------------+-------+------------+
RFC4145 Attribute Analysis
5.41. RFC6947 - The SDP ALTC Attribute
[RFC6947] proposes a mechanism that allows the same SDP offer to
carry multiple IP addresses of different address families (e.g., IPv4
and IPv6). The proposed attribute, the "altc" attribute, solves the
backward-compatibility problem that plagued Alternative Network
Address Types (ANAT) due to their syntax.
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+-------+--------------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------+--------------------------------------+-------+------------+
| altc | The IP Address and port must be the | M | TRANSPORT |
| | one that corresponds to the m=line | | |
| | chosen for setting up the underlying | | |
| | transport flow. | | |
| | | | |
+-------+--------------------------------------+-------+------------+
RFC6947 Attribute Analysis
5.42. RFC7195 - SDP Extension for Circuit Switched Bearers in PSTN
[RFC7195] describes use cases, requirements, and protocol extensions
for using the Session Description Protocol (SDP) offer/answer model
for establishing audio and video media streams over circuit-switched
bearers in the Public Switched Telephone Network (PSTN).
+--------------------------+----------------+-------+----------+
| Name | Notes | Level | Category |
+--------------------------+----------------+-------+----------+
| cs-correlation:callerid | Not Impacted. | M | NORMAL |
| | | | |
| cs-correlation:uuie | Not Impacted. | M | NORMAL |
| | | | |
| cs-correlation:dtmf | Not Impacted. | M | NORMAL |
| | | | |
| cs-correlation:external | Not Impacted. | M | NORMAL |
| | | | |
+--------------------------+----------------+-------+----------+
RFC7195 Attribute Analysis
5.43. RFC7272 - IDMS Using the RTP Control Protocol (RTCP)
[RFC7272] defines a new RTP Control Protocol (RTCP) Packet Type and
an RTCP Extended Report (XR) Block Type to be used for achieving
Inter-Destination Media Synchronization (IDMS).
+------------+----------------+-------+----------+
| Name | Notes | Level | Category |
+------------+----------------+-------+----------+
| rtcp-idms | Not Impacted. | M | NORMAL |
| | | | |
+------------+----------------+-------+----------+
RFC7272 Attribute Analysis
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5.44. RFC5159 - OMA BCAST SDP Attributes
[RFC5159] provides descriptions of Session Description Protocol (SDP)
attributes used by the Open Mobile Alliance's Broadcast Service and
Content Protection specification.
+---------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+---------------------+---------------+-------+----------+
| bcastversion | Not Impacted | S | NORMAL |
| | | | |
| stkmstream | Not Impacted | B | NORMAL |
| | | | |
| SRTPAuthentication | Not Impacted | M | NORMAL |
| | | | |
| SRTPROCTxRate | Not Impacted | M | NORMAL |
| | | | |
+---------------------+---------------+-------+----------+
RFC5159 Attribute Analysis
5.45. RFC6193 - Media Description for IKE in SDP
[RFC6193] specifies how to establish a media session that represents
a virtual private network using the Session Initiation Protocol for
the purpose of on-demand media/application sharing between peers. It
extends the protocol identifier of the Session Description Protocol
(SDP) so that it can negotiate use of the Internet Key Exchange
Protocol (IKE) for media sessions in the SDP offer/answer model.
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+-------------------+--------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------------------+--------------------------+-------+------------+
| ike-setup | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
| psk-fingerprint | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
| ike-esp | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
| ike-esp-udpencap | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
+-------------------+--------------------------+-------+------------+
RFC6193 Attribute Analysis
With the above SDP constraints, a session multiplexed with multiple
m=lines will use only one IPSec association for all of the m= lines.
5.46. RFC6064 - SDP and RTSP Extensions for 3GPP
The Packet-switched Streaming Service (PSS) and the Multimedia
Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session
Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
with some extensions. [RFC6064] provides information about these
extensions and registers the RTSP and SDP extensions with IANA.
+-------------------------------+------------+-------+--------------+
| Name | Notes | Level | Category |
+-------------------------------+------------+-------+--------------+
| X-predecbufsize | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| X-initpredecbufperiod | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| X-initpostdecbufperiod | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
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| | | | |
| X-decbyterate | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3gpp-videopostdecbufsize | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| framesize | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-Integrity-Key | Refer to | S | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-SDP-Auth | Refer to | S | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-SRTP-Config | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| alt,alt-default-id | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| alt-group | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-Adaptation-Support | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-Asset-Informatio | Refer to | B | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| mbms-mode | Refer to | B | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| mbms-flowid | Refer to | M | NOT |
| | notes | | RECOMMENDED |
| | below | | |
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| | | | |
| mbms-repair | Refer to | B | NOT |
| | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Corruption | Refer to | M | NOT |
| duration | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Rebuffering | Refer to | M | NOT |
| duration | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Initial | Refer to | M | NOT |
| buffering duration | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Successive | Refer to | M | NOT |
| loss of RTP packets | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Frame rate | Refer to | M | NOT |
| deviation | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Jitter | Refer to | M | NOT |
| duration | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Content | Refer to | B | NOT |
| Switch Time | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Average | Refer to | M | NOT |
| Codec Bitrat | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Codec | Refer to | M | NOT |
| Information | notes | | RECOMMENDED |
| | below | | |
| | | | |
| 3GPP-QoE-Metrics:Buffer | Refer to | M | NOT |
| Status | notes | | RECOMMENDED |
| | below | | |
| | | | |
+-------------------------------+------------+-------+--------------+
RFC6064 Attribute Analysis
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[RFC6064] defines SDP attributes that are applicable in the
declarative usage of SDP alone. For purposes of this document, only
the Offer/Answer usage of SDP is considered as mandated by
[I-D.ietf-mmusic-sdp-bundle-negotiation].
5.47. RFC3108 - ATM SDP
RFC3108 [RFC3108] describes conventions for using the Session
Description Protocol (SDP) described for controlling ATM Bearer
Connections, and any associated ATM Adaptation Layer (AAL)
+------------------------+--------------+-------+----------+
| Name | Notes | Level | Category |
+------------------------+--------------+-------+----------+
| aalType | Not Impacted | B | NORMAL |
| eecid | Not Impacted | B | NORMAL |
| aalType | Not Impacted | B | NORMAL |
| capability | Not Impacted | B | NORMAL |
| qosClass | Not Impacted | B | NORMAL |
| bcob | Not Impacted | B | NORMAL |
| stc | Not Impacted | B | NORMAL |
| upcc | Not Impacted | B | NORMAL |
| atmQOSparms | Not Impacted | B | NORMAL |
| atmTrfcDesc | Not Impacted | B | NORMAL |
| abrParms | Not Impacted | B | NORMAL |
| abrSetup | Not Impacted | B | NORMAL |
| bearerType | Not Impacted | B | NORMAL |
| lij | Not Impacted | B | NORMAL |
| anycast | Not Impacted | B | NORMAL |
| cache | Not Impacted | B | NORMAL |
| bearerSigIE | Not Impacted | B | NORMAL |
| aalApp | Not Impacted | B | NORMAL |
| cbrRate | Not Impacted | B | NORMAL |
| sbc | Not Impacted | B | NORMAL |
| clkrec | Not Impacted | B | NORMAL |
| fec | Not Impacted | B | NORMAL |
| prtfl | Not Impacted | B | NORMAL |
| structure | Not Impacted | B | NORMAL |
| cpsSDUsize | Not Impacted | B | NORMAL |
| aal2CPS | Not Impacted | B | NORMAL |
| aal2CPSSDUrate | Not Impacted | B | NORMAL |
| aal2sscs3661unassured | Not Impacted | B | NORMAL |
| aal2sscs3661assured | Not Impacted | B | NORMAL |
| aal2sscs3662 | Not Impacted | B | NORMAL |
| aal5sscop | Not Impacted | B | NORMAL |
| atmmap | Not Impacted | B | NORMAL |
| silenceSupp | Not Impacted | B | NORMAL |
| ecan | Not Impacted | B | NORMAL |
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| gc | Not Impacted | B | NORMAL |
| profileDesc | Not Impacted | B | NORMAL |
| vsel | Not Impacted | B | NORMAL |
| dsel | Not Impacted | B | NORMAL |
| fsel | Not Impacted | B | NORMAL |
| onewaySel | Not Impacted | B | NORMAL |
| codecconfig | Not Impacted | B | NORMAL |
| isup_usi | Not Impacted | B | NORMAL |
| isup_usi | Not Impacted | B | NORMAL |
| chain | Not Impacted | B | NORMAL |
| | | | |
+------------------------+--------------+-------+----------+
RFC3108 Attribute Analysis
RFC3108 describes conventions for using the Session Description
Protocol (SDP) for characterizing ATM bearer connections using an
AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5,
bearer connections can be used to transport single media streams. In
addition, for AAL1 and AAL2, multiple media streams may be
multiplexed into a bearer connection. For all adaptation types
(AAL1, AAL2 and AAL5), bearer connections may be bundled into a
single media group. In all cases addressed by RFC3108, a real-time
media stream (voice, video, voiceband data, pseudo-wire and others)
or a multiplex of media streams is mapped directly into an ATM
connection. RFC3108 does not address cases where ATM serves as a
low-level transport pipe for IP packets which in turn may carry one
or more real-time (e.g. VoIP) media sessions with a life-cycle
different from that of the underlying ATM transport.
5.48. 3GPP TS 26.114
[R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and
interaction
+----------------------+-------------------------+-------+----------+
| Name | Notes | Level | Category |
+----------------------+-------------------------+-------+----------+
| 3gpp_sync_info | Usage defined for the | M | NORMAL |
| | IP Multimedia Subsystem | | |
| | | | |
| 3gpp_MaxRecvSDUSize | Usage defined for the | M | NORMAL |
| | IP Multimedia Subsystem | | |
| | | | |
+----------------------+-------------------------+-------+----------+
3GPP TS 24.182 Attribute Analysis
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5.49. 3GPP TS 24.182
[R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting
tones
+-------------+----------------------------------+-------+----------+
| Name | Notes | Level | Category |
+-------------+----------------------------------+-------+----------+
| g.3gpp.cat | Usage defined for the IP | M | NORMAL |
| | Multimedia Subsystem | | |
| | | | |
+-------------+----------------------------------+-------+----------+
3GPP TS 24.182 Attribute Analysis
5.50. 3GPP TS 24.183
[R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing
Signal
+-------------+----------------------------------+-------+----------+
| Name | Notes | Level | Category |
+-------------+----------------------------------+-------+----------+
| g.3gpp.crs | Usage defined for the IP | M | NORMAL |
| | Multimedia Subsystem | | |
| | | | |
+-------------+----------------------------------+-------+----------+
3GPP TS 24.183 Attribute Analysis
5.51. 3GPP TS 24.229
[R3GPPTS24.229] specifies IP multimedia call control protocol based
on Session Initial protocol and Session Description Protocol.
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+------------------+---------------------------+-------+------------+
| Name | Notes | Level | Category |
+------------------+---------------------------+-------+------------+
| secondary-realm | Per media-level attribute | M | TRANSPORT |
| | MUST be used per | | |
| | underlying transport | | |
| | | | |
| visited-realm | Per media-level attribute | M | TRANSPORT |
| | MUST be used per | | |
| | underlying transport | | |
| | | | |
| omr-m-cksum | Not Impacted | M | NORMAL |
| | | | |
| omr-s-cksum | Not Impacted | M | NORMAL |
| | | | |
| omr-m-att | Not Impacted | M | NORMAL |
| | | | |
| omr-s-bw | Not Impacted | M | NORMAL |
| | | | |
| omr-s-bw | Not Impacted | M | NORMAL |
| | | | |
| omr-m-att | Not Impacted | M | NORMAL |
| | | | |
| omr-codecs | Not Impacted | M | NORMAL |
| | | | |
+------------------+---------------------------+-------+------------+
3GPP TS 24.229 Attribute Analysis
5.52. ITU T.38
[T.38] defines procedures for real-time Group 3 facsimile
communications over IP networks.
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+------------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------------------+---------------+-------+----------+
| T38FaxVersion | Not Impacted | S | NORMAL |
| | | | |
| T38MaxBitRate | Not Impacted | S | NORMAL |
| | | | |
| T38FaxFillBitRemoval | Not Impacted | S | NORMAL |
| | | | |
| T38FaxTranscodingMMR | Not Impacted | S | NORMAL |
| | | | |
| T38FaxTranscodingJBIG | Not Impacted | S | NORMAL |
| | | | |
| T38FaxRateManagement | Not Impacted | S | NORMAL |
| | | | |
| T38FaxMaxBuffer | Not Impacted | S | NORMAL |
| | | | |
| T38FaxMaxDatagram | Not Impacted | S | NORMAL |
| | | | |
| T38FaxUdpEC | Not Impacted | S | NORMAL |
| | | | |
| T38FaxMaxIFP | Not Impacted | S | NORMAL |
| | | | |
| T38FaxUdpECDepth | Not Impacted | S | NORMAL |
| | | | |
| T38FaxUdpFECMaxSpan | Not Impacted | S | NORMAL |
| | | | |
| T38ModemType | Not Impacted | S | NORMAL |
| | | | |
+------------------------+---------------+-------+----------+
Historic Attribute Analysis
The ITU T.38 attributes are clearly unaffected by multiplexing and
are specific to the working of the fax protocol itself.
5.53. ITU-T-REC.Q1970
[ITU-T-REC.Q1970] defines BICC IP bearer control protocol.
+--------+---------------+-------+----------+
| Name | Notes | Level | Category |
+--------+---------------+-------+----------+
| ipbcp | Not Impacted | S | NORMAL |
| | | | |
+--------+---------------+-------+----------+
ITU-T-REC.Q1970 Attribute Analysis
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5.54. ITU-T H.248.15
ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248
package attribute
+-----------+------------------------------------+-------+----------+
| Name | Notes | Level | Category |
+-----------+------------------------------------+-------+----------+
| h248item | It is also only applicable for | B | SPECIAL |
| | signaling the inclusion of H.248 | | |
| | extension packages to a gateway | | |
| | via the local and remote | | |
| | descriptors. The attribute itself | | |
| | is unaffected by multiplexing, but | | |
| | the packaged referenced in a | | |
| | specific use of the attribute may | | |
| | be impacted. Further analysis of | | |
| | each package is needed to | | |
| | determine if there is an issue. | | |
| | This is only a concern in | | |
| | environments using a decomposed | | |
| | server/gateway with H.248 signaled | | |
| | between them. The ITU-T will need | | |
| | to do further analysis of various | | |
| | packages when they specify how to | | |
| | signal the use of multiplexing to | | |
| | a gateway. | | |
| | | | |
+-----------+------------------------------------+-------+----------+
Historic Attribute Analysis
5.55. RFC4975 - The Message Session Relay Protocol
[RFC4975] the Message Session Relay Protocol, a protocol for
transmitting a series of related instant messages in the context of a
session. Message sessions are treated like any other media stream
when set up via a rendezvous or session creation protocol such as the
Session Initiation Protocol.
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+-----------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-----------------------+---------------+-------+----------+
| accept-types | Not Impacted | M | NORMAL |
| | | | |
| accept-wrapped-types | Not Impacted | M | NORMAL |
| | | | |
| max-size | Not Impacted | M | NORMAL |
| | | | |
| path | Not Impacted | M | NORMAL |
| | | | |
+-----------------------+---------------+-------+----------+
RFC4975 Attribute Analysis
5.56. Historical
This section specifies analysis for the attributes that are included
for historic usage alone by the [IANA].
+---------------------+--------------+---------------+--------------+
| Name | Notes | Level | Category |
+---------------------+--------------+---------------+--------------+
| rtpred1 | Historic | Not-Applcable | NOT |
| | attributes. | | RECOMMENDED |
| | | | |
| rtpred2 | Historic | Not-Applcable | NOT |
| | attributes. | | RECOMMENDED |
| | | | |
| PSCid | Not | Not-Applcable | NORMAL |
| | Applicable | | |
| | | | |
| bc_service | Not | Not-Applcable | NORMAL |
| | Applicable | | |
| | | | |
| bc_program | Not | Not-Applcable | NORMAL |
| | Applicable | | |
| | | | |
| bc_service_package | Not | Not-Applcable | NORMAL |
| | Applicable | | |
| | | | |
+---------------------+--------------+---------------+--------------+
Unknowns Attribute Analysis
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6. bwtype Attribute Analysis
This section specifies handling of specific bandwidth attributes when
used in multiplexing scenarios.
6.1. RFC4566 - SDP: Session Description Protocol
+------------+-----------------------------------+-------+----------+
| Name | Notes | Level | Category |
+------------+-----------------------------------+-------+----------+
| bwtype:CT | Not Impacted | S | NORMAL |
| | | | |
| bwtype:AS | As a session attribute, it | B | NORMAL |
| | specifies the session aggregate | | |
| | unless media-level b=RR and/or | | |
| | b=RS attributes are used. Under | | |
| | this interpretation the | | |
| | multiplexing scheme has no impact | | |
| | and thus NORMAL category applies. | | |
| | | | |
| bwtype:AS | For the media level usage, the | B | SUM |
| | aggregate of individual bandwidth | | |
| | values is considered. | | |
| | | | |
+------------+-----------------------------------+-------+----------+
RFC4566 bwtype Analysis
6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth
RFC3556 [RFC3556] defines an extension to the Session Description
Protocol (SDP) to specify two additional modifiers for the bandwidth
attribute. These modifiers may be used to specify the bandwidth
allowed for RTP Control Protocol (RTCP) packets in a Real-time
Transport Protocol (RTP) session
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+------------+-----------------------------------+-------+----------+
| Name | Notes | Level | Category |
+------------+-----------------------------------+-------+----------+
| bwtype:RS | Session level usage represents | B | NORMAL |
| | session aggregate and media level | | |
| | usage indicates SUM of the | | |
| | individual values while | | |
| | multiplexing | | |
| | | | |
| bwtype:RR | Session level usage represents | B | NORMAL |
| | session aggregate and media level | | |
| | usage indicates SUM of the | | |
| | individual values while | | |
| | multiplexing | | |
| | | | |
+------------+-----------------------------------+-------+----------+
RFC3556 bwtype Analysis
6.3. RFC3890 - Bandwidth Modifier for SDP
RFC3890 [RFC3890] defines a Session Description Protocol (SDP)
Transport Independent Application Specific Maximum (TIAS) bandwidth
modifier that does not include transport overhead; instead an
additional packet rate attribute is defined. The transport
independent bit-rate value together with the maximum packet rate can
then be used to calculate the real bit-rate over the transport
actually used.
+--------------+---------------------------------+-------+----------+
| Name | Notes | Level | Category |
+--------------+---------------------------------+-------+----------+
| bwtype:TIAS | The usage of TIAS is not | B | SPECIAL |
| | clearly defined Offer/Answer | | |
| | usage. | | |
| | | | |
| maxprate | The usage of TIAS and maxprate | B | SPECIAL |
| | is not well defined under | | |
| | multiplexing | | |
| | | | |
+--------------+---------------------------------+-------+----------+
RFC3890 bwtype Analysis
The intention of TIAS is that the media level bit-rate is multiplied
with the known per-packet overhead for the selected transport and the
maxprate value to determine the worst case bit-rate from the
transport to more accurately capture the required usage. Summing
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TIAS values independently across m=lines and multiplying the computed
sum with maxprate and the per-packet overhead would inflate the value
significantly. Instead performing multiplication and adding the
individual values is a more appropriate usage. This still ignores
the fact that this is a send side declaration, and not intended for
receiver negotiation.
7. rtcp-fb Attribute Analysis
This section analyzes rtcp-fb SDP attributes.
7.1. RFC4585 - RTP/AVPF
RFC4585 [RFC4585] defines an extension to the Audio-visual Profile
(AVP) that enables receivers to provide, statistically, more
immediate feedback to the senders and thus allows for short-term
adaptation and efficient feedback-based repair mechanisms to be
implemented.
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+----------+----------------------------+-------+-------------------+
| Attr | Notes | Level | Category |
| Name | | | |
+----------+----------------------------+-------+-------------------+
| ack rpsi | The attribute value must | M | IDENTICAL-PER-PT |
| | be same for a given codec | | |
| | configuration | | |
| | | | |
| ack app | Feedback parameters MUST | M | SPECIAL |
| | be handled in the app | | |
| | specific way when | | |
| | multiplexed | | |
| | | | |
| nack | The attribute value must | M | IDENTICAL-PER-PT |
| | be same for a given codec | | |
| | configuration | | |
| | | | |
| nack pli | The attribute value must | M | IDENTICAL-PER-PT |
| | be same for a given codec | | |
| | configuration | | |
| | | | |
| nack sli | The attribute value must | M | IDENTICAL-PER-PT |
| | be same for a given codec | | |
| | configuration | | |
| | | | |
| nack | The attribute value must | M | IDENTICAL-PER-PT |
| rpsi | be same for a given codec | | |
| | configuration | | |
| | | | |
| nack app | Feedback parameters MUST | M | SPECIAL |
| | be handled in the app | | |
| | specific way when | | |
| | multiplexed | | |
| | | | |
| trr-int | The attribute value must | M | IDENTICAL-PER-PT |
| | be same for a given codec | | |
| | configuration | | |
| | | | |
+----------+----------------------------+-------+-------------------+
RFC4585 Attribute Analysis
7.2. RFC5104 - Codec Control Messages in AVPF
RFC5104 [RFC5104] specifies a few extensions to the messages defined
in the Audio-Visual Profile with Feedback (AVPF). They are helpful
primarily in conversational multimedia scenarios where centralized
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multipoint functionalities are in use. However, some are also usable
in smaller multicast environments and point-to-point calls.
+-------+-------------------------------+-------+-------------------+
| Attr | Notes | Level | Category |
| Name | | | |
+-------+-------------------------------+-------+-------------------+
| ccm | The attribute value must be | M | IDENTICAL-PER-PT |
| | same for a given codec | | |
| | configuration | | |
| | | | |
+-------+-------------------------------+-------+-------------------+
RFC5104 Attribute Analysis
7.3. RFC6285 - Unicast-Based RAMS
+-------+-------------------------------+-------+-------------------+
| Name | Notes | Level | Category |
+-------+-------------------------------+-------+-------------------+
| nack | The attribute value must be | M | IDENTICAL-PER-PT |
| rai | same for a given codec | | |
| | configuration | | |
| | | | |
+-------+-------------------------------+-------+-------------------+
RFC6285 Attribute Analysis
7.4. RFC6679 - ECN for RTP over UDP/IP
RFC6679 [RFC6679] specifies how Explicit Congestion Notification
(ECN) can be used with the Real-time Transport Protocol (RTP) running
over UDP, using the RTP Control Protocol (RTCP) as a feedback
mechanism. It defines a new RTCP Extended Report (XR) block for
periodic ECN feedback, a new RTCP transport feedback message for
timely reporting of congestion events, and a Session Traversal
Utilities for NAT (STUN) extension used in the optional
initialization method using Interactive Connectivity Establishment
(ICE)
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+------------------+---------------------------+-------+------------+
| Name | Notes | Level | Category |
+------------------+---------------------------+-------+------------+
| ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL |
| | the RTP Session level | | |
| | | | |
| nack ecn | This attribute enables | M | IDENTICAL |
| | ECN at the RTP session | | |
| | level | | |
| | | | |
+------------------+---------------------------+-------+------------+
RFC6679 Attribute Analysis
7.5. RFC6642 - Third-Party Loss Report
In a large RTP session using the RTP Control Protocol (RTCP) feedback
mechanism defined in RFC 4585 [RFC4585], a feedback target may
experience transient overload if some event causes a large number of
receivers to send feedback at once. This overload is usually avoided
by ensuring that feedback reports are forwarded to all receivers,
allowing them to avoid sending duplicate feedback reports. However,
there are cases where it is not recommended to forward feedback
reports, and this may allow feedback implosion. RFC6642 [RFC6642]
memo discusses these cases and defines a new RTCP Third-Party Loss
Report that can be used to inform receivers that the feedback target
is aware of some loss event, allowing them to suppress feedback.
Associated Session Description Protocol (SDP) signaling is also
defined.
+--------+------------------------------+-------+-------------------+
| Name | Notes | Level | Category |
+--------+------------------------------+-------+-------------------+
| nack | The attribute value must be | M | IDENTICAL-PER-PT |
| tllei | same for a given codec | | |
| | configuration | | |
| | | | |
| nack | The attribute value must be | M | IDENTICAL-PER-PT |
| pslei | same for a given codec | | |
| | configuration | | |
| | | | |
+--------+------------------------------+-------+-------------------+
RFC6642 Attribute Analysis
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7.6. RFC5104 - Codec Control Messages in AVPF
+--------+------------------------------+-------+-------------------+
| Attr | Notes | Level | Category |
| Name | | | |
+--------+------------------------------+-------+-------------------+
| ccm | The attribute value must be | M | IDENTICAL-PER-PT |
| fir | same for a given codec | | |
| | configuration | | |
| | | | |
| ccm | The attribute value must be | M | IDENTICAL-PER-PT |
| tmmbr | same for a given codec | | |
| | configuration | | |
| | | | |
| ccm | The attribute value must be | M | IDENTICAL-PER-PT |
| tstr | same for a given codec | | |
| | configuration | | |
| | | | |
| ccm | The attribute value must be | M | IDENTICAL-PER-PT |
| vbcm | same for a given codec | | |
| | configuration | | |
| | | | |
+--------+------------------------------+-------+-------------------+
RFC5104 Attribute Analysis
8. group Attribute Analysis
This section analyzes SDP "group" semantics.
8.1. RFC5888 - SDP Grouping Framework
RFC5888 [RFC5888] defines a framework to group "m" lines in the
Session Description Protocol (SDP) for different purposes.
+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| group:LS | Not Impacted | S | NORMAL |
| | | | |
| group:FID | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC5888 Attribute Analysis
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8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows
RFC3524 [RFC3524] defines an extension to the Session Description
Protocol (SDP) grouping framework. It allows requesting a group of
media streams to be mapped into a single resource reservation flow.
The SDP syntax needed is defined, as well as a new "semantics"
attribute called Single Reservation Flow (SRF).
+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| group:SRF | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC3524 Attribute Analysis
8.3. RFC4091 - ANAT Semantics
RFC4091 [RFC4091] defines the Alternative Network Address Types
(ANAT) semantics for the Session Description Protocol (SDP) grouping
framework. The ANAT semantics allow alternative types of network
addresses to establish a particular media stream.
+-------------+---------------------------+-------+-----------------+
| Name | Notes | Level | Category |
+-------------+---------------------------+-------+-----------------+
| group:ANAT | ANAT semantics is | S | NOT RECOMMENDED |
| | obseleted | | |
| | | | |
+-------------+---------------------------+-------+-----------------+
RFC4091 Attribute Analysis
8.4. RFC5956 - FEC Grouping Semantics in SDP
RFC5956 [RFC5956] defines the semantics for grouping the associated
source and FEC-based (Forward Error Correction) repair flows in the
Session Description Protocol (SDP). The semantics defined in the
document are to be used with the SDP Grouping Framework (RFC 5888).
These semantics allow the description of grouping relationships
between the source and repair flows when one or more source and/or
repair flows are associated in the same group, and they provide
support for additive repair flows. SSRC-level (Synchronization
Source) grouping semantics are also defined in this document for
Real-time Transport Protocol (RTP) streams using SSRC multiplexing.
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+---------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+---------------+---------------+-------+----------+
| group:FEC-FR | Not Impacted | S | NORMAL |
| | | | |
+---------------+---------------+-------+----------+
RFC5956 Attribute Analysis
8.5. RFC5583 - Signaling Media Decoding Dependency in SDP
RFC5583 [RFC5583] defines semantics that allow for signaling the
decoding dependency of different media descriptions with the same
media type in the Session Description Protocol (SDP). This is
required, for example, if media data is separated and transported in
different network streams as a result of the use of a layered or
multiple descriptive media coding process.
+--------+------------------------------+-------+-------------------+
| Name | Notes | Level | Category |
+--------+------------------------------+-------+-------------------+
| depend | The attribute value must be | M | IDENTICAL-PER-PT |
| lay | same for a given codec | | |
| | configuration | | |
| | | | |
| depend | The attribute value must be | M | IDENTICAL-PER-PT |
| mdc | same for a given codec | | |
| | configuration | | |
| | | | |
+--------+------------------------------+-------+-------------------+
RFC5583 Attribute Analysis
8.6. RFC7104 - Duplication Grouping Semantics in the SDP
[RFC7104] defines the semantics for grouping redundant streams in the
Session Description Protocol (SDP). The semantics defined in this
document are to be used with the SDP Grouping Framework. Grouping
semantics at the Synchronization Source (SSRC) level are also defined
in this document for RTP streams using SSRC multiplexing.
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+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| group:DUP | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC7104 Attribute Analysis
9. ssrc-group Attribute Analysis
This section analyzes "ssrc-group" semantics.
9.1. RFC5576 - Source-Specific SDP Attributes
+-------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-------------------+---------------+-------+----------+
| ssrc-group:FID | Not Impacted | M | NORMAL |
| | | | |
| ssrc-group:FEC | Not Impacted | M | NORMAL |
| | | | |
| ssrc-groupFEC-FR | Not Impacted | M | NORMAL |
| | | | |
+-------------------+---------------+-------+----------+
RFC5576 Attribute Analysis
9.2. RFC7104 - Duplication Grouping Semantics in the SDP
+-----------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-----------------+---------------+-------+----------+
| ssrc-group:DUP | Not Impacted | M | NORMAL |
| | | | |
+-----------------+---------------+-------+----------+
RFC7104 Attribute Analysis
10. QoS Mechanism Token Analysis
This section analyzes QoS tokes specified with SDP.
10.1. RFC5432 - QoS Mechanism Selection in SDP
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+-------+----------------------------------------+-------+----------+
| Name | Notes | Level | Category |
+-------+----------------------------------------+-------+----------+
| rsvp | Not Impacted, since QOS mechanisms are | B | NORMAL |
| | applied per flow. | | |
| | | | |
| nsis | Not Impacted, since QOS mechanisms are | B | NORMAL |
| | applied per flow. | | |
| | | | |
+-------+----------------------------------------+-------+----------+
RFC5432 Attribute Analysis
11. k= Attribute Analysis
11.1. RFC4566 SDP: Session Description Protocol
+------+------------------------------------+-------+---------------+
| Name | Notes | Level | Category |
+------+------------------------------------+-------+---------------+
| k= | It is NOT recommended to use this | S | NOT |
| | attribute | | RECOMMENDED |
| | | | |
+------+------------------------------------+-------+---------------+
RFC4566 Attribute Analysis
12. content Atribute Analysis
12.1. RFC4796
+------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------------+---------------+-------+----------+
| content:slides | Not Impacted | M | NORMAL |
| | | | |
| content:speaker | Not Impacted | M | NORMAL |
| | | | |
| content:main | Not Impacted | M | NORMAL |
| | | | |
| content:sl | Not Impacted | M | NORMAL |
| | | | |
| content:alt | Not Impacted | M | NORMAL |
| | | | |
+------------------+---------------+-------+----------+
RFC4796 Attribute Analysis
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13. Payload Formats
13.1. RFC5109 - RTP Payload Format for Generic FEC
[RFC5109] describes a payload format for generic Forward Error
Correction (FEC) for media data encapsulated in RTP. It is based on
the exclusive-or (parity) operation. The payload format allows end
systems to apply protection using various protection lengths and
levels, in addition to using various protection group sizes to adapt
to different media and channel characteristics. It enables complete
recovery of the protected packets or partial recovery of the critical
parts of the payload depending on the packet loss situation.
+---------------------+----------------------+-------+--------------+
| Name | Notes | Level | Category |
+---------------------+----------------------+-------+--------------+
| audio/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMENDED |
| | reuse of SSRCs | | |
| | | | |
| video/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMENDED |
| | reuse of SSRCs | | |
| | | | |
| text/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMENDED |
| | reuse of SSRCs | | |
| | | | |
| application/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMENDED |
| | reuse of SSRCs | | |
| | | | |
+---------------------+----------------------+-------+--------------+
RFC5109 Payload Format Analysis
Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make
it possible to use ULP with multiplexing and ULP is allowed when used
with that.
14. Multiplexing Considerations for Encapsulating Attributes
This sections deals with recommendations for defining the
multiplexing characteristics of the SDP attributes that encapsulate
other SDP attributes/parameters. Such attributes as of today, for
example, are defined in [RFC3407], [RFC5939] and [RFC6871] as part of
a generic framework for indicating and negotiating transport, media
and media format related capabilities in the SDP.
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The behavior of such attributes under multiplexing is in turn defined
by the multiplexing behavior of the attributes they encapsulate which
are made known once the Offer/Answer negotiation process is
completed.
14.1. RFC3407 - cpar Attribute Analysis
RFC3407 capability parameter attribute (a=cpar) encapsulates b=
(bandwidth) or an a= attribute. For bandwidth attribute
encapsulation, the category SUM is inherited. For the case of a=
attribute, the category corresponding to the SDP attribute being
encapsulated is inherited.
v=0
o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=video 3456 RTP/AVP 100
a=rtpmap:100 VP8/90000
a=sqn: 0
a=cdsc: 1 video RTP/AVP 100
a=cpar: a=rtcp-mux
m=video 3456 RTP/AVP 101
a=rtpmap:101 VP8/90000
a=fmtp:100 max-fr=15;max-fs=1200
a=cdsc: 2 video RTP/AVP 101
a=cpar: a=rtcp-mux
In the above example ,the category IDENTICAL is inherited for the
cpar encapsulated rtcp-mux attribute.
14.2. RFC5939 Analysis
[RFC5939] defines a general SDP capability negotiation framework. It
also specifies how to provide transport protocols and SDP attributes
as capabilities and negotiate them using the framework.
For this purpose, [RFC5939] defines the following
o A set of capabilities for the session and its associated media
stream components, supported by each side. The attribute
("a=acap") defines how to list an attribute name and its
associated value (if any) as a capability. The attribute
("a=tcap") defines how to list transport protocols (e.g., "RTP/
AVP") as capabilities.
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o A set of potential configurations ("a=pcfg") provided by the
offerer to indicate whcich combination of those capabilities can
be used for the session and its associated media stream
components. Potential configurations are not ready for use until
fully negotiated. They provide an alternative that may be used,
subject to SDP capability negotiation procedures. In particular
the answerer may choose one of the potential configurations for
use as part of the current Offer/Answer exchange.
o An actual configuration ("a=acfg") for the session and its
associated media stream components. The actual configuration
identifies the potential configuration that was negotiated for
use. Use of an actual configuration does not require any further
negotiation.
o A negotiation process that takes the current actual and the set of
potential configurations (combinations of capabilities) as input
and provides the negotiated actual configurations as output. In
[RFC5939] the negotiation process is done independently for each
media description.
14.2.1. Recommendation - Procedures for Potential Configuration Pairing
This section provides recommendations for entities generating and
processing SDP under the generic capability negotiation framework as
defined in [RFC5939] under the context of media stream multiplexing.
These recommendations are provided for the purposes of enabling the
Offerer to make sure that the generated potential configurations
between the multiplexed streams can (easily) be negotiated to be
consistent between those streams. In particular, the procedures aim
to simply Answerer's procedure to choose potential configurations
that are consistent across all the bundled media descriptions.
A potential configuration selects a set of attributes and parameters
that become part of the media description when negotiated. When
multiplexing media descriptions with potential configurations
specified, there may be a need for coordinating this selection
between multiplexed media descriptions ensuring right multiplexing
behavior.
Although it is possible to analyze the various potential
configurations in bundled media descriptions to find combinations
that satisfy such constraints, it can quickly become complicated to
do so.
The procedures defined in [RFC5939] state that each potential
configuration in the SDP has a unique configuration number, however
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the scope of uniqueness is limited to each media description. To
make it simple for the answerer to chose valid combinations of
potential configurations across media descriptions in a given bundle
group, we provide a simple rule for constructiong potential
configurations:-
o Let m-bundle be the set of media descriptions that form a given
bundle .
o Let m-bundle-pcfg be the set of media descriptions in m-bundle
that include one or more potential configurations.
o Each media description in m-bundle-pcfg MUST have at least one
potential configuration with the same configuration number (e.g.
"1").
o For each potential configuration with configuration number x in m-
bundle-pcfg, the offerer MUST ensure that if the answerer chooses
configuration number x in each of the media descriptions in m-
bundle-pcfg, then the resulting SDP will have all multiplexing
constraints satisfied for those media descriptions.
o Since it is nearly impossible to define a generic mechanism for
various capability extensions , this document does't provide
procedures for dealing with the capability extension attributes.
However, Section Section 14.3 provide analysis of media capability
extension attributes as defined in [RFC6871].
The above allows the answerer to easily find multiplexing compatible
combinations of potential configurations:- The answerer simply choses
a potential configuration (number) that is present in all of the
media descriptions with potential configurations in the bundle.
Note that it is still possible for the offerer to provide additional
potential configurations with independent configuration numbers. The
answerer will have to perform more complicated analysis to determine
valid multiplexed combinations of those.
14.2.1.1. Example: Transport Capability Multiplexing
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v=0
o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
a=tcap:1 RTP/SAVPF
a=tcap:2 RTP/SAVP
a=group:BUNDLE audio video
m= audio
a=mid:audio
a=pcfg:1 t=1
a=pcfg:2
m= video
a=mid:video
a=pcfg:1 t=1
a=pcfg:2 t=2
In the example above, the potential configurations that offer
transport protocol capability of RTP/SAVPF has the same configuration
number "1" in both the audio and video media descriptions.
14.2.1.2. Example: Attribute Capability Multiplexing
v=0
o=alice 2890844526 2890844527 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
a=acap:1 a=rtcp-mux
a=acap:2 a=crypto:1 AES_CM_128_HMAC_SHA1_80
inline:EcGZiNWpFJhQXdspcl1ekcmVCNWpVLcfHAwJSoj|2^20|1:32
a=group:BUNDLE audio video
m= audio 49172 RTP/AVP 99
a=mid:audio
a=pcfg:1 a=1
a=pcfg:2
m= video 560024 RTP/AVP 100
a=mid:video
a=pcfg:1 a=1
a=pcfg:2 a=2
In the example above, the potential configuration number 1 is
repeated while referring to attribute capability a=rtcp-mux, since
the behavior is IDENTICAL for the attribute a=rtcp-mux under
multiplexing.
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14.3. RFC6871 Analysis
[RFC6871] extends capability negotiation framework described in
[RFC5939] by defining media capabilities that can be used to indicate
and negotiate media types and their associated format parameters. It
also allows indication of latent configurations and session
capabilities (the latter of which is not recommended for use with
bundled media as described in Section 5.29).
14.3.1. Recommendation: Dealing with Payload Type Numbers
RFC 6871 defines a new payload type ("pt") parameter to be used with
the potential, actual and latent configuration parameters. The
parameter associates RTP payload type numbers with the referenced
RTP-based media format capabilities ("a=rmcap") defined in [RFC6871]
and is appropriate only when the transport protocol uses RTP. This
means that the same payload type number can be assigned as part of
potential or actual configurations in different media descriptions in
a bundle. There are rules for the usage of identical Payload Type
values across multiplexed m=lines as described in [I-D.ietf-mmusic-
sdp-bundle-negotiation], which MUST be followed here as well. As
described in Section 15.2, the use of identical configuration numbers
for compatible configurations in different media descriptions that
are part of the bundle provides a way to ensure that the answerer can
easily pick compatible configurations here as well.
14.3.1.1. Example: Attribute Capability Under Shared Payload Type
The attributes (a=rmcap, a=mfcap) follow the above recommendations
under mutliplexing
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v=0
o=- 25678 753849 IN IP4 192.0.2.1
s=
c=IN IP4 192.0.2.1
t=0 0
a=creq:med-v0
m=audio 54322 RTP/AVP 96
a=rtpmap:96 AMR-WB/16000/1
a=fmtp:96 mode-change-capability=1; max-red=220;
mode-set=0,2,4,7
a=rmcap:1,3 audio AMR-WB/16000/1
a=rmcap:2 audio AMR/8000/1
a=mfcap:1,2 mode-change-capability=1
a=mfcap:3 mode-change-capability=2
a=pcfg:1 m=1 pt=1:96
a=pcfg:2 m=2 pt=2:97
a=pcfg:3 m=3 pt=3:98
m=audio 54322 RTP/AVP 96
a=rtpmap:96 AMR-WB/16000/1
a=fmtp:96 mode-change-capability=1; max-red=220;
mode-set=0,2,4,7
a=rmcap:4 audio AMR/8000/1
a=rmcap:5 audio OPUS/48000/2
a=mfcap:5 minptime=40
a=mfcap:4 mode-change-capability=1
a=pcfg:1 m=4 pt=4:97
a=pcfg:4 m=5 pt=5:101
In the example above, the potential configuration number 1 is
repeated when referring to media and media format capability used for
the Payload Type 97. This implies that both the media capability 2
and 4 along with their media format capabilities MUST refer to the
same codec configuration , as per the definition of IDENTICAL-PER-PT
14.3.2. Recommendation: Dealing with Latent Configurations
RFC 6871 adds the notion of a latent configurations, which provides
configuration information that may be used to guide a subsequent
offer/exchange, e.g. by adding another media stream or use
alternative codec combinations not currently offered. Latent
configurations have configuration numbers which cannot overlap with
the potential configuration numbers [RFC6871]. Supported
combinations of potential and latent configurations are indicated by
use of the "a=sescap" attribute, however use of this attribute is not
recommended with bundled media, since it requires the use of unique
configuration numbers across the SDP. Taken together, this means
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there is no well-defined way to indicate supported combinations of
latent configurations, or combinations of latent and potential
configurations with bundled media. It is still allowed to use the
latent configuration attribute, however the limitations above will
apply. To determine valid combinations, actual negotiation will have
to be attempted subsequently instead.
15. IANA Considerations
[RFC EDITOR NOTE: Please replace RFCXXXX with the RFC number of this
document.]
The IANA is requested to add a new column named "Mux Category" to all
several of the registries in the "Session Description Protocol (SDP)
Parameters". Section Section 15.1 defines the new registry for
identifying the initial registrations for "Mux Category" as proposed
in this document. The tables in Section 15.2 identify name of an
entry in the existing registry and specify the value to put in the
new "Mux Category" column of the associated IANA registry. Any
entries in the existing tables that do not have a value for the "Mux
Category" specified in this RFC will get a value of "TBD". Future
specifications can change the "TBD" entries to the correct value.
15.1. New Column 'Mux Category'
A new registry needs to be setup for specifying possible values for
the "Mux Category" column, with the following registrations created
initially: "NORMAL", "NOT RECOMMENDED", "IDENTICAL", "TRANSPORT",
"IDENTICAL-PER-PT", SPECIAL" and "TBD" as defined in this document.
Initial value registration for the column "Mux Category".
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Value name: NORMAL
Reference : RFCXXXX
Value name: NOT RECOMMENDED
Reference : RFCXXXX
Value name: IDENTICAL
Reference : RFCXXXX
Value name: TRANSPORT
Reference : RFCXXXX
Value name: IDENTICAL-PER-PT
Reference : RFCXXXX
Value name: SPECIAL
Reference : RFCXXXX
Value name: TBD
Reference : RFCXXXX
Further entries may be registered on a first-come first-serve basis.
Each registration needs to indicate the "Mux Category" value and
identify the entries in the existing registries defined at "Session
Description Protocol (SDP) Parameters" to which the newly registered
"Mux Category" applies. For each new registration, it is mandatory
that a permanent, stable, and publicly accessible document exists
that specifies the semantics of the registered parameter in the
context of multiplexing and its applicability to existing registered
SDP parameters as stated above. The general registration procedures
of [RFC4566] apply.
15.2. 'Mux Category' values for SDP Registries
The various sub-sections below assigns the values to be used for the
"Mux Category" column for the corresponding registries idenfied.
15.2.1. Table: SDP bwtype
The following values are to be added to the 'SDP bwtype' registry in
the "Session Description Protocol (SDP) Parameters. The references
should be updated to point at this RFC as well as the previous
references.
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+-------+--------------+
| Type | Mux Category |
+-------+--------------+
| CT | NORMAL |
| AS | SUM |
| RS | NORMAL |
| RR | NORMAL |
| TIAS | SPECIAL |
+-------+--------------+
15.2.2. Table: att-field
The following values are to be added to the 'att-field' registry in
the "Session Description Protocol (SDP) Parameters. The references
should be updated to point at this RFC as well as the previous
references.
+---------------------------+-------------------+
| SDP Name | Mux Category |
+---------------------------+-------------------+
| cat | NORMAL |
| keywds | NORMAL |
| type | NORMAL |
| type:broadcast | NORMAL |
| type:H332 | NORMAL |
| type:meeting | NORMAL |
| type:moderated | NORMAL |
| type:test | NORMAL |
| charset | NORMAL |
| charset:iso8895-1 | NORMAL |
| tool | NORMAL |
| ipbcp | NORMAL |
| group | NORMAL |
| ice-lite | NORMAL |
| ice-options | NORMAL |
| bcastversion | NORMAL |
| 3GPP-Integrity-Key | NOT RECOMMENDED |
| 3GPP-SDP-Auth | NOT RECOMMENDED |
| alt-group | NOT RECOMMENDED |
| PSCid | NORMAL |
| bc_service | NORMAL |
| bc_program | NORMAL |
| bc_service_package | NORMAL |
| sescap | NOT RECOMMENDED |
| rtsp-ice-d-m | TBD |
| recvonly | NORMAL |
| sendrecv | NORMAL |
| sendonly | NORMAL |
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| sdplang | NORMAL |
| lang | NORMAL |
| h248item | SPECIAL |
| sqn | NORMAL |
| cdsc | NORMAL |
| cpar | INHERIT |
| cparmin | SPECIAL |
| cparmax | SPECIAL |
| rtcp-xr | NORMAL |
| maxprate | SPECIAL |
| setup | IDENTICAL |
| connection | IDENTICAL |
| key-mgmt | IDENTICAL |
| source-filter | IDENTICAL |
| inactive | NORMAL |
| fingerprint | TRANSPORT |
| flute-tsi | TBD |
| flute-ch | TBD |
| FEC-declaration | TBD |
| FEC-OTI-extension | TBD |
| content-desc | TBD |
| ice-pwd | TRANSPORT |
| ice-ufrag | TRANSPORT |
| stkmstream | NORMAL |
| qos-mech-send | NORMAL |
| qos-mech-recv | NORMAL |
| csup | NORMAL |
| creq | NORMAL |
| acap | INHERIT |
| tcap | INHERIT |
| 3GPP-QoE-Metrics | NOT RECOMMENDED |
| 3GPP-Asset-Information | NOT RECOMMENDED |
| mbms-mode | NORMAL |
| mbms-repair | NORMAL |
| ike-setup | IDENTICAL |
| psk-fingerprint | IDENTICAL |
| multicast-rtcp | IDENTICAL |
| rmcap | IDENTICAL-PER-PT |
| omcap | NORMAL |
| mfcap | IDENTICAL-PER-PT |
| mscap | INHERIT |
| bcap | INHERIT |
| ccap | IDENTICAL |
| icap | NORMAL |
| 3gpp_sync_info | NORMAL |
| 3gpp_MaxRecvSDUSize | NORMAL |
| etag | TBD |
| duplication-delay | NORMAL |
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| range | TBD |
| control | TBD |
| mtag | TBD |
| ts-refclk | NORMAL |
| mediaclk | NORMAL |
| calgextmap | NORMAL |
| ptime | IDENTICAL-PER-PT |
| orient | NORMAL |
| orient:portrait | NORMAL |
| orient:landscape | NORMAL |
| orient:seascape | NORMAL |
| framerate | IDENTICAL-PER-PT |
| quality | NORMAL |
| rtpmap | IDENTICAL-PER-PT |
| fmtp | IDENTICAL-PER-PT |
| rtpred1 | NOT RECOMMENDED |
| rtpred2 | NOT RECOMMENDED |
| T38FaxVersion | NORMAL |
| T38MaxBitRate | NORMAL |
| T38MaxBitRate | NORMAL |
| T38FaxTranscodingMMR | NORMAL |
| T38FaxTranscodingJBIG | NORMAL |
| T38FaxRateManagement | NORMAL |
| T38FaxMaxBuffer | NORMAL |
| T38FaxMaxDatagram | NORMAL |
| T38FaxUdpEC | NORMAL |
| maxptime | IDENTICAL-PER-PT |
| des | NORMAL |
| curr | NORMAL |
| conf | NORMAL |
| mid | NORMAL |
| rtcp | IDENTICAL |
| rtcp-fb | IDENTICAL-PER-PT |
| label | NORMAL |
| T38VendorInfo | NORMAL |
| crypto | TRANSPORT |
| eecid | NORMAL |
| aalType | NORMAL |
| capability | NORMAL |
| qosClass | NORMAL |
| bcob | NORMAL |
| stc | NORMAL |
| upcc | NORMAL |
| atmQOSparms | NORMAL |
| atmQOSparms | NORMAL |
| abrParms | NORMAL |
| abrSetup | NORMAL |
| bearerType | NORMAL |
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| lij | NORMAL |
| anycast | NORMAL |
| cache | NORMAL |
| bearerSigIE | NORMAL |
| aalApp | NORMAL |
| cbrRate | NORMAL |
| sbc | NORMAL |
| clkrec | NORMAL |
| fec | NORMAL |
| prtfl | NORMAL |
| structure | NORMAL |
| cpsSDUsize | NORMAL |
| all2CPS | NORMAL |
| all2CPSSDUrate | NORMAL |
| aal2sscs3661unassured | NORMAL |
| aal2sscs3661assured | NORMAL |
| aal2sscs3662 | NORMAL |
| aal5sscop | NORMAL |
| atmmap | NORMAL |
| silenceSupp | NORMAL |
| ecan | NORMAL |
| gc | NORMAL |
| profileDesc | NORMAL |
| vsel | NORMAL |
| dsel | NORMAL |
| fsel | NORMAL |
| onewaySel | NORMAL |
| codecConfig | NORMAL |
| isup_usi | NORMAL |
| uiLayer1_Prot | NORMAL |
| chain | NORMAL |
| floorctrl | IDENTICAL |
| confid | NORMAL |
| userid | NORMAL |
| floorid | NORMAL |
| FEC | NORMAL |
| profileDesc | NORMAL |
| accept-types | NORMAL |
| accept-wrapped-types | NORMAL |
| max-size | NORMAL |
| path | NORMAL |
| dccp-service-code | NOT RECOMMENDED |
| rtcp-mux | IDENTICAL |
| candidate | TRANSPORT |
| ice-mismatch | NORMAL |
| remote-candidates | TRANSPORT |
| SRTPAuthentication | NORMAL |
| SRTPROCTxRate | NORMAL |
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| rtcp-rsize | IDENTICAL |
| file-selector | NORMAL |
| file-transfer-id | NORMAL |
| file-disposition | NORMAL |
| file-date | NORMAL |
| file-icon | NORMAL |
| file-range | NORMAL |
| depend | IDENTICAL-PER-PT |
| ssrc | NORMAL |
| ssrc-group | NORMAL |
| rtcp-unicast | IDENTICAL |
| pcfg | SPECIAL |
| acfg | SPECIAL |
| zrtp-hash | NOT RECOMMENDED |
| X-predecbufsize | NOT RECOMMENDED |
| X-initpredecbufperiod | NOT RECOMMENDED |
| X-initpostdecbufperiod | NOT RECOMMENDED |
| X-decbyterate | NOT RECOMMENDED |
| 3gpp-videopostdecbufsize | NOT RECOMMENDED |
| framesize | NOT RECOMMENDED |
| 3GPP-SRTP-Config | NOT RECOMMENDED |
| alt | NOT RECOMMENDED |
| alt-default-id | NOT RECOMMENDED |
| 3GPP-Adaption-Support | NOT RECOMMENDED |
| mbms-flowid | NOT RECOMMENDED |
| fec-source-flow | SPECIAL |
| fec-repair-flow | SPECIAL |
| repair-window | SPECIAL |
| rams-updates | NOT RECOMMENDED |
| imageattr | IDENTICAL-PER-PT |
| cfw-id | NORMAL |
| portmapping-req | NOT RECOMMENDED |
| g.3gpp.cat | NORMAL |
| g.3gpp.crs | NORMAL |
| ecm-capable-rtp | IDENTICAL-PER-PT |
| visited-realm | TRANSPORT |
| secondary-realm | TRANSPORT |
| omr-s-cksum | NORMAL |
| omr-m-Cksum | NORMAL |
| omr-codecs | NORMAL |
| omr-codecs | NORMAL |
| omr-m-att | NORMAL |
| omr-m-bw | NORMAL |
| omr-s-bw | NORMAL |
| msrcp-cema | NORMAL |
| dccp-port | NOT RECOMMENDED |
| resource | NORMAL |
| channel | NORMAL |
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| cmid | NORMAL |
| content | NORMAL |
| lcfg | SPECIAL |
| loopback | NORMAL |
| loopback-source | NORMAL |
| loopback-mirror | NORMAL |
| chatroom | TBD |
| altc | TRANSPORT |
| T38FaxMaxIFP | NORMAL |
| T38FaxUdpECDepth | NORMAL |
| T38FaxUdpFECMaxSpan | NORMAL |
| T38ModemType | NORMAL |
| cs-correlation | NORMAL |
| rtcpidms | NORMAL |
| cname | NORMAL |
| previous-ssrc | NORMAL |
| fmtp | IDENTICAL-PER-PT |
+---------------------------+-------------------+
15.2.3. Table: content SDP Parameters
The following values are to be added to the 'content SDP Parameters'
registry in the "Session Description Protocol (SDP) Parameters. The
references should be updated to point at this RFC as well as the
previous references.
+----------+--------------+
| SDP Name | Mux Category |
+----------+--------------+
| slides | NORMAL |
| speaker | NORMAL |
| sl | NORMAL |
| main | NORMAL |
| alt | NORMAL |
+----------+--------------+
15.2.4. Table: Semantics for the 'group' SDP Attribute
The following values are to be added to the Semantics for the "group"
SDP Attribute registry in the "Session Description Protocol (SDP)
Parameters. The references should be updated to point at this RFC as
well as the previous references.
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+---------+------------------+
| Token | Mux Category |
+---------+------------------+
| LS | NORMAL |
| FID | NORMAL |
| SRF | NORMAL |
| ANAT | NOT RECOMMENDED |
| FEC | NORMAL |
| FEC-FR | NORMAL |
| CS | NORMAL |
| DDP | NORMAL |
| DUP | NORMAL |
+---------+------------------+
15.2.5. Table: 'rtcp-fb' Attribute Values
The following values are to be added to the " 'rtcp-fb' Attribute
Values" registry in the "Session Description Protocol (SDP)
Parameters. The references should be updated to point at this RFC as
well as the previous references.
+------------+-------------------+
| Value Name | Mux Category |
+------------+-------------------+
| ack | IDENTICAL-PER-PT |
| app | SPECIAL |
| ccm | IDENTICAL-PER-PT |
| nack | IDENTICAL-PER-PT |
| trr-int | IDENTICAL-PER-PT |
+------------+-------------------+
15.2.6. Table: 'ack' and 'nack' Attribute Values
The following values are to be added to the " 'ack' and 'nack'
Attribute Values" registry in the "Session Description Protocol (SDP)
Parameters. The references should be updated to point at this RFC as
well as the previous references.
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+------------+-------------------+
| Value Name | Mux Category |
+------------+-------------------+
| sli | IDENTICAL-PER-PT |
| pli | IDENTICAL-PER-PT |
| rpsi | IDENTICAL-PER-PT |
| app | IDENTICAL-PER-PT |
| rai | IDENTICAL-PER-PT |
| tllei | IDENTICAL-PER-PT |
| pslei | IDENTICAL-PER-PT |
| ecn | IDENTICAL-PER-PT |
+------------+-------------------+
15.2.7. Table: 'depend' SDP Attribute Values
The following values are to be added to the " 'depend' SDP Attribute
Values" registry in the "Session Description Protocol (SDP)
Parameters. The references should be updated to point at this RFC as
well as the previous references.
+-------+--------------+
| Token | Mux Category |
+-------+--------------+
| lay | NORMAL |
| mdc | NORMAL |
+-------+--------------+
15.2.8. Table: 'cs-correlation' Attribute Values
The following values are to be added to the " 'cs-correlation'
Attribute Values" registry in the "Session Description Protocol (SDP)
Parameters. The references should be updated to point at this RFC as
well as the previous references.
+-----------+--------------+
| Token | Mux Category |
+-----------+--------------+
| callerid | NORMAL |
| uuie | NORMAL |
| dtmf | NORMAL |
| external | NORMAL |
+-----------+--------------+
15.2.9. Table: Semantics for the 'ssrc-group' SDP Attribute
The following values are to be added to the Semantics for the "
'ssrc-group' SDP Attribute" registry in the "Session Description
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Protocol (SDP) Parameters. The references should be updated to point
at this RFC as well as the previous references.
+---------+--------------+
| Token | Mux Category |
+---------+--------------+
| FID | NORMAL |
| FEC | NORMAL |
| FEC-FR | NORMAL |
| DUP | NORMAL |
+---------+--------------+
15.2.10. Table: SDP/RTSP key management protocol identifiers
The following values are to be added to the "SDP/RTSP key management
protocol identifiers" registry in the "Session Description Protocol
(SDP) Parameters. The references should be updated to point at this
RFC as well as the previous references.
+------------+--------------+
| Value Name | Mux Category |
+------------+--------------+
| mikey | IDENTICAL |
+------------+--------------+
15.2.11. Table: Codec Control Messages
The following values are to be added to the "Codec Control Messages"
registry in the "Session Description Protocol (SDP) Parameters. The
references should be updated to point at this RFC as well as the
previous references.
+------------+-------------------+
| Value Name | Mux Category |
+------------+-------------------+
| fir | IDENTICAL-PER-PT |
| tmmbr | IDENTICAL-PER-PT |
| tstr | IDENTICAL-PER-PT |
| vbcm | IDENTICAL-PER-PT |
+------------+-------------------+
15.2.12. Table: QoS Mechanism Tokens
The following values are to be added to the "QoS Mechanism Tokens"
registry in the "Session Description Protocol (SDP) Parameters. The
references should be updated to point at this RFC as well as the
previous references.
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+---------------+--------------+
| QoS Mechanism | Mux Category |
+---------------+--------------+
| rsvp | NORMAL |
| nsis | NORMAL |
+---------------+--------------+
15.2.13. Table: SDP Capability Negotiation Option Tags
The following values are to be added to the "SDP Capability
Negotiation Option Tags" Registry in the "Session Description
Protocol (SDP) Parameters. The references should be updated to point
at this RFC as well as the previous references.
+---------------+--------------+
| QoS Mechanism | Mux Category |
+---------------+--------------+
| cap-v0 | NORMAL |
| med-v0 | NORMAL |
| bcap-v0 | NORMAL |
| ccap-v0 | NORMAL |
| icap-v0 | NORMAL |
+---------------+--------------+
15.2.14. Table: Timestamp Reference Clock Source Parameters
The following values are to be added to the "Timestamp Reference
Clock Source Parameters" Registry in the "Session Description
Protocol (SDP) Parameters. The references should be updated to point
at this RFC as well as the previous references.
+----------+--------------+
| Name | Mux Category |
+----------+--------------+
| ntp | NORMAL |
| ptp | NORMAL |
| gps | NORMAL |
| gal | NORMAL |
| glonass | NORMAL |
| local | NORMAL |
| private | NORMAL |
+----------+--------------+
15.2.15. Table: Media Clock Source Parameters
The following values are to be added to the "Media Clock Source
Parameters" Registry in the "Session Description Protocol (SDP)
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Parameters. The references should be updated to point at this RFC as
well as the previous references.
+-----------+--------------+
| Name | Mux Category |
+-----------+--------------+
| sender | NORMAL |
| direct | NORMAL |
| IEEE1722 | NORMAL |
+-----------+--------------+
16. Security Considerations
This document does not add any new security considerations beyond the
existing considerations in the RFC for protocols that are being
multiplexed together.
The ways that SRTP streams are keyed is not believed to create any
two-time pad vulnerability for the currently defined SRTP keying
mechanism.
17. Acknowledgments
I would like to thank Cullen Jennings for suggesting the categories,
contributing text and reviewing the draft. I would also link to
thank Magnus, Christer, Jonathan Lennox, Bo Burman, and Dan on
suggesting structural changes helping improve the document
readability.
I would like also to thank following experts on their inputs and
reviews as listed - Flemming Andreasen(5.20,5.28,5.29,15), Rohan
Mahy(5.45), Eric Burger(5.22),Christian Huitema(5.13), Christer
Holmberg(5.17,5.22,5.40,5.41), Richard Ejzak (5.36,5.42,5.43,5.44),
Colin Perkins(5.7,5.8), Magnus westerlund(5.2,5.3,5.9,5.26,
5.27,6.1,6.2,6.3,8.3,7), Roni Evens(5.12,5.27,8.4), Subha
Dhesikan(5.5,12.1,14), Dan Wing(5.6,5.11,5.30,5.34,5.37), Ali C
Begen(5.1,5.16,5.18,5.21,5.33,8.2,8.4,13.1), Bo Burman (7.2,7.6),
Charles Eckel(5.14,5.23,5.24,9.1,8.5), Paul Kyzivat(5.24), Ian
Johansson(5.15), Saravanan Shanmugham(5.10), Paul E Jones(5.25),
Rajesh Kumar(5.39), Jonathan Lennox(5.31,5,14,11.1), Mo
Zanaty(5.4,5.19,8.1,8.3,8.5,12.1), Christian Huitema (5.13), Qin Wu
(5.38 PM-Dir review).
18. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-mmusic-sdp-mux-attributes-02
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o Incorporated suggestions from Flemming on Capability Negotiation.
o Closed open issues from IETF90
o Added IANA section to list the categories for all the SDP
attributes anlayzed
o Lots of cleanup
o Reformatted Refernces section to use short-form notation
Changes from draft-ietf-mmusic-sdp-mux-attributes-01
o Updated section 15 to provide detailed recommendation on dealing
with encapsulating attributes. Also updated sections 5.20, 5.28,
5.29 to refer to Section 15.
o Added new categories IDENTICAL-PER-PT and INHERIT
o Updated Sections 16 to add the new categories.
o Updated Sections 5.1, 5.14, 5.15, 5.38, 8.5 to reflect the
category IDENTICAL-PER-PT.
o Reformatted section 4 to add individual categories to their own
sections.
Changes from draft-ietf-mmusic-sdp-mux-attributes-00
o Added Section 15 to provide recommendations on multiplexing SDP
encapsulating attributes. Also updated sections 5.20, 5.28, 5.29
to refer to Section 15.
o Updated Section 5.38 to incorporate PM-dir review inputs from Qin
Wu
o Updated Sections 5.2,5.14,8.5 to refer to BUNDLE draft for more
clarity.
o Fixed few nits regarding sentence clarity and fill-in the NOTES
section where information was lacking.
Changes from draft-nandakumar-mmusic-mux-attributes-05
o Renamed the document to be a WG document.
o Added Section 14.
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o Updated Open Issues based on IETF88 discussions.
Changes from draft-nandakumar-mmusic-mux-attributes-04
o Added few OPEN ISSUES that needs to be discussed.
o Updated sections 5.10,5.23,5,24,5,25,7.2,9.1,5.12,5.27,8.4,
5.44,5.11,5.4,5.19,10.1,10.5,5.21,10.4,15.1
o Updated Table Column name Current to Level and improved TRANSPORT
category explanation on suggestions form Dan Wing.
o Grouped all the rtcp-fb attribute analysis under a single section
as suggested by Magnus/
Changes from draft-nandakumar-mmusic-mux-attributes-03
o Maintenance change to clean up grammatical nits and wordings.
Changes from draft-nandakumar-mmusic-mux-attributes-02
o Updated Sections 5.3,5.5,5.6,5.7,5.9,5.8,5.11,5.13,5.22,5.34,
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
the inputs from the respective RFC Authors.
Changes from draft-nandakumar-mmusic-mux-attributes-01
o Replaced Category BAD with NOT RECOMMENDED.
o Added Category TBD.
o Updated IANA Consideration Section.
Changes from draft-nandakumar-mmusic-mux-attributes-00
o Added new section for dealing with FEC payload types.
19. References
19.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
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19.2. Informative References
[H.248.15]
"Gateway control protocol: SDP H.248 package attribute",
<http://www.itu.int/rec/T-REC-H.248.15>.
[I-D.ietf-mmusic-sdp-bundle-negotiation]
Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
negotiation-12 (work in progress), October 2014.
[I.D-draft-ietf-dart-dscp-rtp]
Black, D. and P. Jones, "The Session Description Protocol
(SDP) Content Attribute", draft-ietf-dart-dscp-rtp-07
(work in progress), September 2014.
[IANA] "S Description Protocol (SDP) Parameters",
<http://www.iana.org/assignments/sdp-parameters/
sdp-parameters.xml>.
[ITU-T-REC.Q1970]
"Q.1970 : BICC IP bearer control protocol",
<https://www.itu.int/rec/T-REC-Q.1970-200609-I/en>.
[R3GPPTS24.182]
"IP Multimedia Subsystem (IMS) Customized Alerting Tones
(CAT); Protocol specification",
<http://www.3gpp.org/ftp/Specs/html-info/24182.htm>.
[R3GPPTS24.183]
"IP Multimedia Subsystem (IMS) Customized Ringing Signal
(CRS); Protocol specification",
<http://www.3gpp.org/ftp/Specs/html-info/24183.htm>.
[R3GPPTS24.229]
"IP multimedia call control protocol based on Session
Initiation Protocol (SIP) and Session Description Protocol
(SDP);",
<http://www.3gpp.org/ftp/Specs/html-info/24229.htm>.
[R3GPPTS26.114]
"IP multimedia Subsystem : Media Handling and
interaction",
<http://www.in2eps.com/3g26/tk-3gpp-26-114.html>.
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[RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the
Session Description Protocol (SDP) for ATM Bearer
Connections", RFC 3108, May 2001.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264, June
2002.
[RFC3312] Camarillo, G., Marshall, W., and J. Rosenberg,
"Integration of Resource Management and Session Initiation
Protocol (SIP)", RFC 3312, October 2002.
[RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple
Capability Declaration", RFC 3407, October 2002.
[RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to
Resource Reservation Flows", RFC 3524, April 2003.
[RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth
Modifiers for RTP Control Protocol (RTCP) Bandwidth", RFC
3556, July 2003.
[RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
in Session Description Protocol (SDP)", RFC 3605, October
2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611, November
2003.
[RFC3890] Westerlund, M., "A Transport Independent Bandwidth
Modifier for the Session Description Protocol (SDP)", RFC
3890, September 2004.
[RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network
Address Types (ANAT) Semantics for the Session Description
Protocol (SDP) Grouping Framework", RFC 4091, June 2005.
[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
September 2005.
[RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E.
Carrara, "Key Management Extensions for Session
Description Protocol (SDP) and Real Time Streaming
Protocol (RTSP)", RFC 4567, July 2006.
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[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
Description Protocol (SDP) Security Descriptions for Media
Streams", RFC 4568, July 2006.
[RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol
(SDP) Source Filters", RFC 4570, July 2006.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, July 2006.
[RFC4574] Levin, O. and G. Camarillo, "The Session Description
Protocol (SDP) Label Attribute", RFC 4574, August 2006.
[RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format
for Binary Floor Control Protocol (BFCP) Streams", RFC
4583, November 2006.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July
2006.
[RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description
Protocol (SDP) Content Attribute", RFC 4796, February
2007.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
Session Relay Protocol (MSRP)", RFC 4975, September 2007.
[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
"Codec Control Messages in the RTP Audio-Visual Profile
with Feedback (AVPF)", RFC 5104, February 2008.
[RFC5109] Li, A., "RTP Payload Format for Generic Forward Error
Correction", RFC 5109, December 2007.
[RFC5159] Dondeti, L. and A. Jerichow, "Session Description Protocol
(SDP) Attributes for Open Mobile Alliance (OMA) Broadcast
(BCAST) Service and Content Protection", RFC 5159, March
2008.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, April
2010.
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[RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP
Header Extensions", RFC 5285, July 2008.
[RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of
Service (QoS) Mechanism Selection in the Session
Description Protocol (SDP)", RFC 5432, March 2009.
[RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size
Real-Time Transport Control Protocol (RTCP): Opportunities
and Consequences", RFC 5506, April 2009.
[RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
and P. Kyzivat, "A Session Description Protocol (SDP)
Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
May 2009.
[RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol
(SDP)", RFC 5576, June 2009.
[RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding
Dependency in the Session Description Protocol (SDP)", RFC
5583, July 2009.
[RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
Protocol (RTCP) Extensions for Single-Source Multicast
Sessions with Unicast Feedback", RFC 5760, February 2010.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761, April 2010.
[RFC5762] Perkins, C., "RTP and the Datagram Congestion Control
Protocol (DCCP)", RFC 5762, April 2010.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, May 2010.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
[RFC5939] Andreasen, F., "Session Description Protocol (SDP)
Capability Negotiation", RFC 5939, September 2010.
[RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in
the Session Description Protocol", RFC 5956, September
2010.
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[RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions
Defined for 3GPP Packet-Switched Streaming Service and
Multimedia Broadcast/Multicast Service", RFC 6064, January
2011.
[RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source-
Specific Multicast (SSM) Sessions", RFC 6128, February
2011.
[RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
Path Key Agreement for Unicast Secure RTP", RFC 6189,
April 2011.
[RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for
the Internet Key Exchange Protocol (IKE) in the Session
Description Protocol (SDP)", RFC 6193, April 2011.
[RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media
Control Channel Framework", RFC 6230, May 2011.
[RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image
Attributes in the Session Description Protocol (SDP)", RFC
6236, May 2011.
[RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping
between Unicast and Multicast RTP Sessions", RFC 6284,
June 2011.
[RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
"Unicast-Based Rapid Acquisition of Multicast RTP
Sessions", RFC 6285, June 2011.
[RFC6364] Begen, A., "Session Description Protocol Elements for the
Forward Error Correction (FEC) Framework", RFC 6364,
October 2011.
[RFC6489] Huston, G., Michaelson, G., and S. Kent, "Certification
Authority (CA) Key Rollover in the Resource Public Key
Infrastructure (RPKI)", BCP 174, RFC 6489, February 2012.
[RFC6642] Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP)
Extension for a Third-Party Loss Report", RFC 6642, June
2012.
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
and K. Carlberg, "Explicit Congestion Notification (ECN)
for RTP over UDP", RFC 6679, August 2012.
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[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
Establishment for Media Anchoring (CEMA) for the Message
Session Relay Protocol (MSRP)", RFC 6714, August 2012.
[RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
Datagram Congestion Control Protocol UDP Encapsulation for
NAT Traversal", RFC 6773, November 2012.
[RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control
Protocol Version 2 (MRCPv2)", RFC 6787, November 2012.
[RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session
Description Protocol (SDP) Media Capabilities
Negotiation", RFC 6871, February 2013.
[RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S.
Veikkolainen, "The Session Description Protocol (SDP)
Alternate Connectivity (ALTC) Attribute", RFC 6947, May
2013.
[RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman,
"Miscellaneous Capabilities Negotiation in the Session
Description Protocol (SDP)", RFC 7006, September 2013.
[RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping
Semantics in the Session Description Protocol", RFC 7104,
January 2014.
[RFC7195] Garcia-Martin, M. and S. Veikkolainen, "Session
Description Protocol (SDP) Extension for Setting Audio and
Video Media Streams over Circuit-Switched Bearers in the
Public Switched Telephone Network (PSTN)", RFC 7195, May
2014.
[RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay
Attribute in the Session Description Protocol", RFC 7197,
April 2014.
[RFC7226] Villamizar, C., McDysan, D., Ning, S., Malis, A., and L.
Yong, "Requirements for Advanced Multipath in MPLS
Networks", RFC 7226, May 2014.
[RFC7272] van Brandenburg, R., Stokking, H., van Deventer, O.,
Boronat, F., Montagud, M., and K. Gross, "Inter-
Destination Media Synchronization (IDMS) Using the RTP
Control Protocol (RTCP)", RFC 7272, June 2014.
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[RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H.
Stokking, "RTP Clock Source Signalling", RFC 7273, June
2014.
[T.38] "Procedures for real-time Group 3 facsimile communication
over IP networks", <http://www.itu.int/rec/T-REC-T.38/e>.
Author's Address
Suhas Nandakumar
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: snandaku@cisco.com
Nandakumar Expires April 23, 2015 [Page 87]
