Internet DRAFT - draft-ietf-mmusic-sdp-mux-attributes
draft-ietf-mmusic-sdp-mux-attributes
Network Working Group S. Nandakumar
Internet-Draft Cisco
Intended status: Standards Track August 27, 2020
Expires: February 28, 2021
A Framework for SDP Attributes when Multiplexing
draft-ietf-mmusic-sdp-mux-attributes-19
Abstract
The purpose of this specification is to provide a framework for
analyzing the multiplexing characteristics of Session Description
Protocol (SDP) attributes when SDP is used to negotiate the usage of
single 5-tuple for sending and receiving media associated with
multiple media descriptions.
This specification also categorizes the existing SDP 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.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on February 28, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . 6
4.1. Category: NORMAL . . . . . . . . . . . . . . . . . . . . 7
4.2. Category: CAUTION . . . . . . . . . . . . . . . . . . . . 7
4.3. Category: IDENTICAL . . . . . . . . . . . . . . . . . . . 8
4.4. Category: SUM . . . . . . . . . . . . . . . . . . . . . . 9
4.5. Category: TRANSPORT . . . . . . . . . . . . . . . . . . . 9
4.6. Category: INHERIT . . . . . . . . . . . . . . . . . . . . 10
4.7. Category: IDENTICAL-PER-PT . . . . . . . . . . . . . . . 11
4.8. Category: SPECIAL . . . . . . . . . . . . . . . . . . . . 12
4.9. Category: TBD . . . . . . . . . . . . . . . . . . . . . . 12
5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 12
5.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 13
5.2. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 14
5.3. RFC5761: Multiplexing RTP and RTCP . . . . . . . . . . . 15
5.4. RFC3312: Integration of Resource Management and SIP . . . 15
5.5. RFC4574: SDP Label Attribute . . . . . . . . . . . . . . 16
5.6. RFC5432: QOS Mechanism Selection in SDP . . . . . . . . . 16
5.7. RFC4568: SDP Security Descriptions . . . . . . . . . . . 17
5.8. RFC5762: RTP over DCCP . . . . . . . . . . . . . . . . . 17
5.9. RFC6773: DCCP-UDP Encapsulation . . . . . . . . . . . . . 18
5.10. RFC5506: Reduced-Size RTCP in RTP Profile . . . . . . . . 19
5.11. RFC6787: Media Resource Control Protocol Version 2 . . . 19
5.12. RFC5245: ICE . . . . . . . . . . . . . . . . . . . . . . 20
5.13. RFC5285: RTP Header Extensions . . . . . . . . . . . . . 21
5.14. RFC3605: RTCP attribute in SDP . . . . . . . . . . . . . 22
5.15. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 22
5.16. RFC7273: RTP Clock Source Signalling . . . . . . . . . . 23
5.17. RFC6236: Image Attributes in SDP . . . . . . . . . . . . 24
5.18. RFC7197: Duplication Delay Attribute in SDP . . . . . . . 25
5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting . . . . 25
5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions . . 25
5.21. RFC6230: Media Control Channel Framework . . . . . . . . 26
5.22. RFC6364: SDP Elements for FEC Framework . . . . . . . . . 26
5.23. RFC4796: Content Attribute . . . . . . . . . . . . . . . 27
5.24. RFC3407: SDP Simple Capability Declaration . . . . . . . 27
5.25. RFC6284: Port Mapping between Unicast and Multicast RTP
Sessions . . . . . . . . . . . . . . . . . . . . . . . . 28
5.26. RFC6714: MSRP-CEMA . . . . . . . . . . . . . . . . . . . 29
5.27. RFC4583: SDP Format for BFCP Streams . . . . . . . . . . 29
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5.28. RFC5547: SDP Offer/Answer for File Transfer . . . . . . . 30
5.29. RFC6849: SDP and RTP Media Loopback Extension . . . . . . 30
5.30. RFC5760: RTCP with Unicast Feedback . . . . . . . . . . . 31
5.31. RFC3611: RTCP XR . . . . . . . . . . . . . . . . . . . . 31
5.32. RFC5939: SDP Capability Negotiation . . . . . . . . . . . 32
5.33. RFC6871: SDP Media Capabilities Negotiation . . . . . . . 32
5.34. RFC7006: Miscellaneous Capabilities Negotiation SDP . . . 33
5.35. RFC4567: Key Management Extensions for SDP and RTSP . . . 34
5.36. RFC4572: Comedia over TLS in SDP . . . . . . . . . . . . 35
5.37. RFC4570: SDP Source Filters . . . . . . . . . . . . . . . 35
5.38. RFC6128: RTCP Port for Multicast Sessions . . . . . . . . 36
5.39. RFC6189: ZRTP . . . . . . . . . . . . . . . . . . . . . . 36
5.40. RFC4145: Connection-Oriented Media . . . . . . . . . . . 37
5.41. RFC6947: The SDP altc Attribute . . . . . . . . . . . . . 37
5.42. RFC7195: SDP Extension for Circuit Switched Bearers
in PSTN . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP) . . . 38
5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP
Attributes . . . . . . . . . . . . . . . . . . . . . . . 39
5.45. RFC6193: Media Description for IKE in SDP . . . . . . . . 39
5.46. RFC2326: Real Time Streaming Protocol . . . . . . . . . . 40
5.47. RFC6064: SDP and RTSP Extensions for 3GPP . . . . . . . . 41
5.48. RFC3108: ATM SDP . . . . . . . . . . . . . . . . . . . . 43
5.49. 3GPP TS 26.114 . . . . . . . . . . . . . . . . . . . . . 45
5.50. 3GPP TS 183.063 . . . . . . . . . . . . . . . . . . . . . 46
5.51. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . 46
5.52. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . 47
5.53. ITU-T Q.1970 . . . . . . . . . . . . . . . . . . . . . . 49
5.54. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . 49
5.55. RFC4975: The Message Session Relay Protocol . . . . . . . 50
5.56. Historical Attributes . . . . . . . . . . . . . . . . . . 51
6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 51
6.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 52
6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth . . . 52
6.3. RFC3890: Bandwidth Modifier for SDP . . . . . . . . . . . 53
7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . 53
7.1. RFC4585: RTP/AVPF . . . . . . . . . . . . . . . . . . . . 53
7.2. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 54
7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP
Sessions (RAMS) . . . . . . . . . . . . . . . . . . . . . 55
7.4. RFC6679: ECN for RTP over UDP/IP . . . . . . . . . . . . 55
7.5. RFC6642: Third-Party Loss Report . . . . . . . . . . . . 56
7.6. RFC5104: Codec Control Messages in AVPF . . . . . . . . . 57
8. group Attribute Analysis . . . . . . . . . . . . . . . . . . 57
8.1. RFC5888: SDP Grouping Framework . . . . . . . . . . . . . 57
8.2. RFC3524: Mapping Media Streams to Resource
Reservation Flows . . . . . . . . . . . . . . . . . . . . 58
8.3. RFC4091: ANAT Semantics . . . . . . . . . . . . . . . . . 58
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8.4. RFC5956: FEC Grouping Semantics in SDP . . . . . . . . . 58
8.5. RFC5583: Signaling Media Decoding Dependency in SDP . . . 59
8.6. RFC7104: Duplication Grouping Semantics in the SDP . . . 59
9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 60
9.1. RFC5576: Source-Specific SDP Attributes . . . . . . . . . 60
9.2. RFC7104: Duplication Grouping Semantics in the SDP . . . 60
10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . 61
10.1. RFC5432: QoS Mechanism Selection in SDP . . . . . . . . 61
11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 61
11.1. RFC4566: SDP . . . . . . . . . . . . . . . . . . . . . . 62
12. content Attribute Analysis . . . . . . . . . . . . . . . . . 62
12.1. RFC4796 . . . . . . . . . . . . . . . . . . . . . . . . 62
12.2. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . 63
12.3. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . 63
13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 63
13.1. RFC5109: RTP Payload Format for Generic FEC . . . . . . 63
14. Multiplexing Considerations for Encapsulating Attributes . . 64
14.1. RFC3407: cpar Attribute Analysis . . . . . . . . . . . . 64
14.2. RFC5939 Analysis . . . . . . . . . . . . . . . . . . . . 65
14.2.1. Recommendation: Procedures for Potential
Configuration Pairing . . . . . . . . . . . . . . . 66
14.2.1.1. Example: Transport Capability Multiplexing . . . 67
14.2.1.2. Example: Attribute Capability Multiplexing . . . 68
14.3. RFC6871 Analysis . . . . . . . . . . . . . . . . . . . . 68
14.3.1. Recommendation: Dealing with Payload Type Numbers . 68
14.3.1.1. Example: Attribute Capability Under Shared
Payload Type . . . . . . . . . . . . . . . . . . 69
14.3.2. Recommendation: Dealing with Latent Configurations . 70
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 70
15.1. New 'Multiplexing Categories' subregistry . . . . . . . 70
15.2. 'Mux Category' column for subregistries . . . . . . . . 71
15.2.1. Table: SDP bwtype . . . . . . . . . . . . . . . . . 72
15.2.2. Table: att-field (session level) . . . . . . . . . . 72
15.2.3. Table: att-field (both session and media level) . . 73
15.2.4. Table: att-field (media level only) . . . . . . . . 75
15.2.5. Table: att-field (source level) . . . . . . . . . . 78
15.2.6. Table: content SDP Parameters . . . . . . . . . . . 79
15.2.7. Table: Semantics for the 'group' SDP Attribute . . . 79
15.2.8. Table: 'rtcp-fb' Attribute Values . . . . . . . . . 79
15.2.9. Table: 'ack' and 'nack' Attribute Values . . . . . . 80
15.2.10. Table: 'depend' SDP Attribute Values . . . . . . . . 80
15.2.11. Table: 'cs-correlation' Attribute Values . . . . . . 81
15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute 81
15.2.13. Table: SDP/RTSP key management protocol identifiers 81
15.2.14. Table: Codec Control Messages . . . . . . . . . . . 82
15.2.15. Table: QoS Mechanism Tokens . . . . . . . . . . . . 82
15.2.16. Table: SDP Capability Negotiation Option Tags . . . 82
15.2.17. Table: Timestamp Reference Clock Source Parameters . 83
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15.2.18. Table: Media Clock Source Parameters . . . . . . . . 83
16. Security Considerations . . . . . . . . . . . . . . . . . . . 83
17. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 83
18. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 84
19. References . . . . . . . . . . . . . . . . . . . . . . . . . 88
19.1. Normative References . . . . . . . . . . . . . . . . . . 88
19.2. Informative References . . . . . . . . . . . . . . . . . 88
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 96
1. Introduction
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
[I-D.ietf-mmusic-sdp-bundle-negotiation] defines a way to use a
single address:port combination (BUNDLE address) for receiving media
associated with multiple SDP media descriptions. This would, for
example allow the usage of a single set of Interactive Connectivity
Establishment (ICE) [RFC5245] candidates for multiple media
descriptions. This in turn has made it 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] and
possibility of new attributes being defined in the future, there is
need for a framework to analyze these attributes for their
applicability in the transport multiplexing use-cases.
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 apply
the framework to the SDP attributes registered with the [IANA].
2. Terminology
5-tuple: A collection of the following values: source address, source
port, destination address, destination port, and transport-layer
protocol.
3GPP: Third Generation Partnership Project; see http://www.3gpp.org
for more information about this organization.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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3. Motivation
The time and complications of setting up ICE [RFC5245] and Datagram
Transport Layer Security (DTLS) based Secure Real-time Transport
Protocol (SRTP) [RFC5763] transports for use by RTP, reasons to
conserve ports bindings on the Network Address Translators (NAT),
forms a 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
the 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.
At the time of writing this document there are close to 250 SDP
attributes registered with the [IANA] and more will be added in the
future. There is no clearly defined procedure to establish the
validity/applicability of these attributes when used with transport
multiplexing.
4. SDP Attribute Analysis Framework
Attributes in an SDP session description can be defined at the
session-level or media-level or source-level. Informally, there are
various semantic groupings for these attributes. One such grouping
could be notes as below:
o Attributes related to media content such as media type, encoding
schemes and payload types.
o Attributes specifying media transport characteristics like RTP/RTP
Control Protocol (RTCP) port numbers, network addresses and QOS.
o Metadata description attributes capturing session timing and
origin information.
o Attributes establishing relationships between media descriptions
such as grouping framework [RFC5888]
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The proposed framework analyzes the SDP attributes usage under
multiplexing and assigns each SDP attribute to an appropriate
multiplexing category. Since the multiplexing categories defined in
this specification are independent of any informal semantic groupings
of the SDP attributes, the categorizations assigned are normative.
4.1. Category: NORMAL
The attributes in the NORMAL category can be independently specified
when multiplexed and they 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: CAUTION
The attributes in the CAUTION category are advised against
multiplexing since their usage under multiplexing might lead to
incorrect behavior.
Example: Multiplexing media descriptions over a single Datagram
Congestion Control Protocol (DCCP) transport [RFC5762] is not
recommended since DCCP being a connection oriented protocol doesn't
allow multiple connections on the same 5-tuple.
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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=video 5004 DCCP/RTP/AVP 99
a=rtpmap:99 h261/9000
a=dccp-service-code:SC=x52545056
a=setup:passive
a=connection:new
m=video 5004 DCCP/RTP/AVP 100
a=rtpmap:100 h261/9000
a=dccp-service-code:SC=x5254504f
a=setup:passive
a=connection:new
4.3. Category: IDENTICAL
The attributes and their associated values (if any) in the IDENTICAL
category MUST be repeated across all the media descriptions under
multiplexing.
Attributes such as rtcp-mux fall into this category. Since RTCP
reporting is done per RTP session, RTCP Multiplexing MUST be enabled
for both the audio and video "m=" lines 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
Note: Eventhough IDENTICAL attributes must be repeated across all
media descriptions under multiplexing, they might not always be
explicitly encoded across all media descriptions.
[I-D.ietf-mmusic-sdp-bundle-negotiation] defines rules for when
attributes and their values are implicitly applied to media
description.
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4.4. Category: SUM
The attributes in the SUM category can be set as they are normally
used but software using them in the multiplexing scenario MUST apply
the sum of all the attributes being multiplexed instead of trying to
use them independently. This is typically used for bandwidth or
other rate limiting attributes to the underlying 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 kilobits per second for
the given example.
v=0
o=test 2890844526 2890842807 IN IP4 client.biloxi.example.com
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
The attributes in the TRANSPORT category can be set normally for
multiple items in a multiplexed group but the software MUST pick the
one that's associated with the "m=" line whose information is used
for setting up the underlying transport.
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.
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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 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
4.6. Category: INHERIT
The attributes in the INHERIT category encapsulate other SDP
attributes or parameters. These attributes inherit their
multiplexing characteristics from the attributes or parameters they
encapsulate. Such attributes 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. The inherited
attributes MUST be coherent in order to form a valid configuration
from a multiplexing point of view (see Section 14 for further
details).
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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
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 by the cpar
encapsulated rtcp-mux attribute.
4.7. Category: IDENTICAL-PER-PT
The attributes in the IDENTICAL-PER-PT category 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. These Payload Types identify the same
codec configuration as defined in the Section 10.1.2 of
[I-D.ietf-mmusic-sdp-bundle-negotiation] under this context.
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 (Note: some line breaks included are due
to formatting only).
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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
For the attributes in the SPECIAL category, the text in the
specification defining the attribute MUST be consulted for further
handling when multiplexed.
As an exampe, for the attribute extmap [RFC5285], the specification
defining the extension needs to be referred to understand the
multiplexing implications.
4.9. Category: TBD
The attributes in the TBD category have not been analyzed under the
proposed multiplexing framework and SHOULD NOT be multiplexed.
5. Analysis of Existing Attributes
This section analyzes attributes listed in [IANA], grouped under the
IETF document that defines them.
The "Level" column indicates whether the attribute is currently
specified as:
o S -- Session level
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o M -- Media level
o B -- Both (Implies either a session level or a media level
attribute)
o SR -- Source-level (for a single SSRC) [RFC5576]
The "Mux Category" column identifies multiplexing category assigned
per attribute and the "Notes" column captures additional informative
details regarding the assigned category, wherever necessary.
5.1. RFC4566: SDP
[RFC4566] defines SDP that is intended for describing multimedia
sessions for the purposes of session announcement, session
invitation, and other forms of multimedia session initiation.
+----------------+-----------------------+-------+------------------+
| Name | Notes | Level | Mux 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- |
| | MUST be same for a | | PT |
| | given codec | | |
| | configuration | | |
| | | | |
| quality | Not Impacted | M | NORMAL |
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| | | | |
| rtpmap | The attribute value | M | IDENTICAL-PER-PT |
| | MUST be same for a | | |
| | given codec | | |
| | configuration | | |
| | | | |
| 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 |
| | | | |
+----------------+-----------------------+-------+------------------+
5.1 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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+---------+------------------------------+-------+------------------+
| Name | Notes | Level | Mux Category |
+---------+------------------------------+-------+------------------+
| rtcp- | Since RTCP feedback | M | IDENTICAL-PER- |
| fb | attributes are Payload Type | | PT |
| | (PT) scoped, their values | | |
| | MUST be identical for a | | |
| | given PT across the | | |
| | multiplexed "m=" lines. | | |
| | | | |
+---------+------------------------------+-------+------------------+
5.2 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 SDP can be used to signal multiplexed sessions.
+----------+------------------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | Category |
+----------+------------------------------------+-------+-----------+
| rtcp- | RTP and RTCP Multiplexing affects | M | IDENTICAL |
| mux | the entire RTP session | | |
| | | | |
+----------+------------------------------------+-------+-----------+
5.3 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 | Mux Category |
+-------+-----------------------+-------+--------------+
| des | Refer to notes below | M | CAUTION |
| | | | |
| conf | Refer to notes below | M | CAUTION |
| | | | |
| curr | Refer to notes below | M | CAUTION |
| | | | |
+-------+-----------------------+-------+--------------+
5.4 RFC3312 Attribute Analysis
NOTE: A mismatched set of preconditions across media descriptions
results in Session establishment failures due to inability to meet
right resource reservations requested.
5.5. RFC4574: SDP Label Attribute
[RFC4574] defines a new 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 | Mux Category |
+--------+---------------+-------+--------------+
| label | Not Impacted | M | NORMAL |
| | | | |
+--------+---------------+-------+--------------+
5.5 RFC4574 Attribute Analysis
5.6. RFC5432: QOS Mechanism Selection in SDP
[RFC5432] defines procedures to negotiate QOS mechanisms using the
SDP offer/answer model.
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+----------------+-----------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+----------------+-----------------------+-------+--------------+
| qos-mech-send | Refer to Section 10 | B | TRANSPORT |
| | | | |
| qos-mech-recv | Refer to Section 10 | B | TRANSPORT |
| | | | |
+----------------+-----------------------+-------+--------------+
5.6 RFC5432 Attribute Analysis
5.7. RFC4568: SDP Security Descriptions
[RFC4568] defines a 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 | Mux |
| | | | Category |
+--------+--------------------------------------+-------+-----------+
| crypto | crypto attribute MUST be the one | M | TRANSPORT |
| | that corresponds to the "m=" line | | |
| | chosen for setting up the underlying | | |
| | transport flow | | |
| | | | |
+--------+--------------------------------------+-------+-----------+
5.7 RFC4568 Attribute Analysis
5.8. RFC5762: RTP over DCCP
RTP is a widely used transport for real-time multimedia on IP
networks. DCCP is a transport protocol that provides desirable
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.
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+-------------------+--------------------------+---------+----------+
| Name | Notes | Current | Mux |
| | | | Category |
+-------------------+--------------------------+---------+----------+
| dccp-service- | If RFC6773 is not being | M | CAUTION |
| code | used in 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 | | |
| | | | |
+-------------------+--------------------------+---------+----------+
5.8 RFC5762 Attribute Analysis
NOTE: If RFC6773 is being used in addition to RFC5762 and provided
that DCCP-in-UDP layer has additional demultiplexing, then it can 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 performing
multiplexing is not recommended even in this alternate scenario.
5.9. RFC6773: DCCP-UDP Encapsulation
[RFC6773] specifies an alternative encapsulation of 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.
+-----------+------------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+-----------+------------------------------------+-------+----------+
| dccp- | Multiplexing is not recommended | M | CAUTION |
| port | due to potential conflict between | | |
| | the port used for DCCP | | |
| | en/decapsulation and the RTP | | |
| | | | |
+-----------+------------------------------------+-------+----------+
5.9 RFC6773 Attribute Analysis
NOTE: RFC6773 is about tunneling DCCP in UDP, with the UDP port being
the port of the DCCP en-/de-capsulation service. This encapsulation
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allows arbitrary DCCP packets to be encapsulated and the DCCP port
chosen can 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 can or cannot work depending on the
nature of DCCP encapsulation and ports choices thus rendering it to
be very application dependent.
5.10. RFC5506: Reduced-Size RTCP in RTP Profile
[RFC5506] discusses benefits and issues that arise when allowing RTCP
packets to be transmitted with reduced size.
+------------+----------------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | Category |
+------------+----------------------------------+-------+-----------+
| rtcp- | Reduced size RTCP affects the | M | IDENTICAL |
| rsize | entire RTP session | | |
| | | | |
+------------+----------------------------------+-------+-----------+
5.10 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 SIP, to coordinate MRCPv2 clients and
servers, and manage session between them, and 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.
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+-----------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+-----------+---------------+-------+--------------+
| resource | Not Impacted | M | NORMAL |
| | | | |
| channel | Not Impacted | M | NORMAL |
| | | | |
| cmid | Not Impacted | M | NORMAL |
| | | | |
+-----------+---------------+-------+--------------+
5.11 RFC6787 Attribute Analysis
5.12. RFC5245: ICE
[RFC5245] describes a protocol for NAT traversal for UDP-based
multimedia sessions established with the offer/answer model. 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 SIP.
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+-------------------+---------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | 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 one | B | TRANSPORT |
| | that corresponds to the | | |
| | "m=" line chosen for | | |
| | setting up the underlying | | |
| | transport flow | | |
| | | | |
| candidate | ice candidate MUST be the | M | TRANSPORT |
| | one that corresponds to | | |
| | the "m=" line chosen for | | |
| | setting up the underlying | | |
| | transport flow | | |
| | | | |
| remote- | ice remote candidate MUST | M | TRANSPORT |
| candidates | be the one that | | |
| | corresponds to the "m=" | | |
| | line chosen for setting | | |
| | up the underlying | | |
| | transport flow | | |
| | | | |
+-------------------+---------------------------+-------+-----------+
5.12 RFC5245 Attribute Analysis
5.13. RFC5285: RTP Header Extensions
[RFC5285] provides a general mechanism to use the header extension
feature of RTP. It provides the option to use a small number of
small extensions in each RTP packet, 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.
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+--------+---------------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+--------+---------------------------------------+-------+----------+
| extmap | Refer to the document defining the | B | SPECIAL |
| | specific RTP Extension | | |
| | | | |
+--------+---------------------------------------+-------+----------+
5.13 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 | Mux |
| | | | Category |
+------+----------------------------------------+-------+-----------+
| rtcp | RTCP Port MUST be the one that | M | TRANSPORT |
| | corresponds to the "m=" line chosen | | |
| | for setting up the underlying | | |
| | transport flow. | | |
| | | | |
+------+----------------------------------------+-------+-----------+
5.14 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 | Mux Category |
+---------------+------------------------+-------+------------------+
| ssrc | Refer to Notes below | M | NORMAL |
| | | | |
| ssrc-group | Refer to Section 9 for | M | NORMAL |
| | specific analysis of | | |
| | the grouping | | |
| | semantics | | |
| | | | |
| cname | Not Impacted | SR | NORMAL |
| | | | |
| previous- | Refer to notes below | SR | NORMAL |
| ssrc | | | |
| | | | |
| fmtp | The attribute value | SR | IDENTICAL-PER- |
| | MUST be same for a | | PT |
| | given codec | | |
| | configuration | | |
| | | | |
+---------------+------------------------+-------+------------------+
5.15 RFC5576 Attribute Analysis
NOTE: 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 SDP signalling that identifies timestamp
reference clock sources and SDP signalling that identifies the media
clock sources in a multimedia session.
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+--------------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+--------------------+---------------+-------+--------------+
| ts-refclk | Not Impacted | B | NORMAL |
| | | | |
| mediaclk | Not Impacted | B | NORMAL |
| | | | |
| ts-refclk:ntp | Not Impacted | B | NORMAL |
| | | | |
| ts-refclk:ptp | Not Impacted | B | NORMAL |
| | | | |
| ts-refclk:gps | Not Impacted | B | NORMAL |
| | | | |
| ts-refclk:gal | Not Impacted | B | NORMAL |
| | | | |
| ts-refclk:glonass | Not Impacted | B | NORMAL |
| | | | |
| ts-refclk:local | Not Impacted | B | NORMAL |
| | | | |
| ts-refclk:private | Not Impacted | B | NORMAL |
| | | | |
| mediaclk:sender | Not Impacted | B | NORMAL |
| | | | |
| mediaclk:direct | Not Impacted | B | NORMAL |
| | | | |
| mediaclk:IEEE1722 | Not Impacted | B | NORMAL |
| | | | |
+--------------------+---------------+-------+--------------+
5.16 RFC7273 Attribute Analysis
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.
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+-----------+----------------------------+-------+------------------+
| Name | Notes | Level | Mux Category |
+-----------+----------------------------+-------+------------------+
| imageattr | The attribute value MUST | M | IDENTICAL-PER- |
| | be same for a given codec | | PT |
| | configuration | | |
| | | | |
+-----------+----------------------------+-------+------------------+
5.17 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 SDP.
+--------------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+--------------------+---------------+-------+--------------+
| duplication-delay | Not Impacted | B | NORMAL |
| | | | |
+--------------------+---------------+-------+--------------+
5.18 RFC7197 Attribute Analysis
5.19. RFC7266: RTCP XR Blocks for MOS Metric Reporting
[RFC7266] defines an RTCP Extended Report (XR) Block including two
new segment types and associated SDP parameters that allow the
reporting of mean opinion score (MOS) Metrics for use in a range of
RTP applications.
+-------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+-------------+---------------+-------+--------------+
| calgextmap | Not Impacted | B | NORMAL |
| | | | |
+-------------+---------------+-------+--------------+
5.19 RFC7266 Attribute Analysis
5.20. RFC6285: Rapid Acquisition of Multicast RTP Sessions
[RFC6285] describes a method using the existing RTP and 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
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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 | Mux Category |
+---------------+------------------+-------+--------------+
| rams-updates | Not recommended | M | CAUTION |
| | | | |
+---------------+------------------+-------+--------------+
5.20 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 SIP to establish an application-level control
mechanism between application servers and associated external servers
such as media servers.
+---------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+---------+---------------+-------+--------------+
| cfw-id | Not Impacted | M | NORMAL |
| | | | |
+---------+---------------+-------+--------------+
5.21 RFC6230 Attribute Analysis
5.22. RFC6364: SDP Elements for FEC Framework
[RFC6364] specifies the use of 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.
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+-----------------+------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+-----------------+------------------------------+-------+----------+
| fec-source- | Refer to the document | M | SPECIAL |
| flow | defining specific FEC | | |
| | Scheme | | |
| | | | |
| fec-repair- | Refer to the document | M | SPECIAL |
| flow | defining specific FEC | | |
| | Scheme | | |
| | | | |
| repair-window | Refer to the document | M | SPECIAL |
| | defining specific FEC | | |
| | Scheme | | |
| | | | |
+-----------------+------------------------------+-------+----------+
5.22 RFC6364 Attribute Analysis
5.23. RFC4796: Content Attribute
[RFC4796] defines a new 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 | Mux Category |
+----------+---------------+-------+--------------+
| content | Not Impacted | M | NORMAL |
| | | | |
+----------+---------------+-------+--------------+
5.23 RFC4796 Attribute Analysis
5.24. RFC3407: SDP Simple Capability Declaration
[RFC3407] defines a set of SDP attributes that enables SDP to provide
a minimal and backwards compatible capability declaration mechanism.
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+----------+------------------------+-------+--------------+
| Name | Notes | Level | Mux 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 |
| | | | |
+----------+------------------------+-------+--------------+
5.24 RFC3407 Attribute Analysis
NOTE: The attributes (a=cparmin and a=cparmax) define minimum and
maximum numerical values associated with the attributes described in
a=cpar.
Since the cpar attribute can either define a 'b=' attribute or any
'a=' attribute, the multiplexing category depends on actual attribute
being encapsulated and the implications of the numerical values
assigned. Hence it is recommended to consult the specification
defining attributes (cparmin/cparmax) to further analyze their
behavior under 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 | Mux |
| | | | Category |
+-----------------+------------------------------+-------+----------+
| portmapping- | Not recommended, if port | M | CAUTION |
| req | mapping is required by the | | |
| | application | | |
| | | | |
+-----------------+------------------------------+-------+----------+
5.25 RFC6284 Attribute Analysis
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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
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 SDP attribute, 'msrp-cema', that MSRP
endpoints use to indicate support of the CEMA extension.
+------------+-----------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+------------+-----------------------+-------+--------------+
| msrp-cema | Refer to notes below | M | TBD |
| | | | |
+------------+-----------------------+-------+--------------+
5.26 RFC6714 Attribute Analysis
NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation],
there exists no publicly available specification that defines
procedures for multiplexing/demultiplexing MRSP flows over a single
5-tuple. Once such a specification is available, the multiplexing
categories assignments for the attributes in this section could be
revisited.
5.27. RFC4583: SDP Format for BFCP Streams
[RFC4583] document specifies how to describe Binary Floor Control
Protocol (BFCP) streams in SDP descriptions. User agents using the
offer/answer model to establish BFCP streams use this format in their
offers and answers.
+------------+-----------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+------------+-----------------------+-------+--------------+
| floorctrl | Refer to notes below | M | TBD |
| | | | |
| confid | Not Impacted | M | NORMAL |
| | | | |
| userid | Not Impacted | M | NORMAL |
| | | | |
| floorid | Not Impacted | M | NORMAL |
| | | | |
+------------+-----------------------+-------+--------------+
5.27 RFC4583 Attribute Analysis
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NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation],
there exists no publicly available specification that defines
procedures for multiplexing/demultiplexing BFCP streams over a single
5-tuple. Once such a specification is available, the multiplexing
categories assignments for the attributes in this section could be
revisited.
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 SDP offer/answer model
specified in [RFC3264].
+-------------------+-----------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+-------------------+-----------------------+-------+--------------+
| file-selector | Refer to notes below | M | TBD |
| | | | |
| file-transfer-id | Refer to notes below | M | TBD |
| | | | |
| file-disposition | Refer to notes below | M | TBD |
| | | | |
| file-date | Refer to notes below | M | TBD |
| | | | |
| file-icon | Refer to notes below | M | TBD |
| | | | |
| file-range | Refer to notes below | M | TBD |
| | | | |
+-------------------+-----------------------+-------+--------------+
5.28 RFC5547 Attribute Analysis
NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation],
there exists no publicly available specification that defines
procedures for multiplexing/demultiplexing MRSP flows over a single
5-tuple. Once such a specification is available, the multiplexing
categories assignments for attributes in this section could be
revisited.
5.29. RFC6849: SDP and RTP Media Loopback Extension
[RFC6849] 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 Voice over IP (VoIP), Real-time Text, and Video over IP
performance metrics.
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+--------------------+-------------------+-------+------------------+
| Name | Notes | Level | Mux Category |
+--------------------+-------------------+-------+------------------+
| loopback rtp-pkt- | The attribute | M | IDENTICAL-PER- |
| loopback | value MUST be | | PT |
| | same for a given | | |
| | codec | | |
| | configuration | | |
| | | | |
| loopback rtp- | The attribute | M | IDENTICAL-PER- |
| media-loopback | value MUST be | | PT |
| | same for a given | | |
| | codec | | |
| | configuration | | |
| | | | |
| loopback-source | Not Impacted | M | NORMAL |
| | | | |
| loopback-mirror | Not Impacted | M | NORMAL |
| | | | |
+--------------------+-------------------+-------+------------------+
5.29 RFC6849 Analysis
5.30. RFC5760: RTCP with Unicast Feedback
[RFC5760] specifies an extension to 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 traditional model of many-to-many group
communication is either not available or not desired.
+--------------+--------------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | Category |
+--------------+--------------------------------+-------+-----------+
| rtcp- | The attribute MUST be reported | M | IDENTICAL |
| unicast | across all "m=" lines | | |
| | multiplexed | | |
| | | | |
+--------------+--------------------------------+-------+-----------+
5.30 RFC5760 Attribute Analysis
5.31. RFC3611: RTCP XR
[RFC3611] defines the Extended Report (XR) packet type for RTCP, and
defines how the use of XR packets can be signaled by an application
if it employs the Session Description Protocol (SDP).
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+----------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+----------+---------------+-------+--------------+
| rtcp-xr | Not Impacted | B | NORMAL |
| | | | |
+----------+---------------+-------+--------------+
5.31 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.
+---------+-----------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+---------+-----------------------+-------+--------------+
| pcfg | Refer to Section 14 | M | SPECIAL |
| | | | |
| acfg | Refer to Section 14 | M | SPECIAL |
| | | | |
| csup | Not Impacted | B | NORMAL |
| | | | |
| creq | Not Impacted | B | NORMAL |
| | | | |
| acap | Refer to Section 14 | B | INHERIT |
| | | | |
| tcap | Refer to Section 14 | B | INHERIT |
| | | | |
| cap-v0 | Not Impacted | B | NORMAL |
| | | | |
+---------+-----------------------+-------+--------------+
5.32 RFC5939 Attribute Analysis
5.33. RFC6871: SDP Media Capabilities Negotiation
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 | Mux Category |
+---------+-----------------------+-------+-------------------+
| rmcap | Refer to Section 14 | B | IDENTICAL-PER-PT |
| | | | |
| omcap | Not Impacted | B | NORMAL |
| | | | |
| mfcap | Refer to Section 14 | B | IDENTICAL-PER-PT |
| | | | |
| mscap | Refer to Section 14 | B | INHERIT |
| | | | |
| lcfg | Refer to Section 14 | B | SPECIAL |
| | | | |
| sescap | Refer to notes below | S | CAUTION |
| | | | |
| med-v0 | Not Impacted | S | NORMAL |
| | | | |
+---------+-----------------------+-------+-------------------+
5.33 RFC6871 - Attribute Analysis
NOTE: 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 14, the use of identical configuration numbers
between multiplexed (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 | Mux |
| | | | 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 be | B | IDENTICAL |
| | identical across all the | | |
| | multiplexed "m=" lines | | |
| | | | |
| ccap-v0 | Not Impacted | B | NORMAL |
| | | | |
| icap | Not Impacted | B | NORMAL |
| | | | |
| icap-v0 | Not Impacted | B | NORMAL |
| | | | |
+---------+-------------------------------------+-------+-----------+
5.34 RFC7006 - Attribute Analysis
5.35. RFC4567: Key Management Extensions for SDP and RTSP
[RFC4567] defines general extensions for 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 | Mux |
| | | | Category |
+----------+------------------------------------+-------+-----------+
| key- | Key management protocol MUST be | B | IDENTICAL |
| mgmt | identical across all the "m=" | | |
| | lines | | |
| | | | |
| mikey | Key management protocol MUST be | B | IDENTICAL |
| | identical across all the "m=" | | |
| | lines | | |
| | | | |
+----------+------------------------------------+-------+-----------+
5.35 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 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 | Mux |
| | | | Category |
+-------------+---------------------------------+-------+-----------+
| fingerprint | fingerprint value MUST be the | B | TRANSPORT |
| | one that corresponds to the | | |
| | "m=" line chosen for setting up | | |
| | the underlying transport flow | | |
| | | | |
+-------------+---------------------------------+-------+-----------+
5.36 RFC4572 Attribute Analysis
5.37. RFC4570: SDP Source Filters
[RFC4570] describes how to adapt 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 | Mux |
| | | | Category |
+---------------+-------------------------------+-------+-----------+
| source- | The attribute MUST be | B | IDENTICAL |
| filter | repeated across all "m=" | | |
| | lines multiplexed | | |
| | | | |
+---------------+-------------------------------+-------+-----------+
5.37 RFC4570 Attribute Analysis
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5.38. RFC6128: RTCP Port for Multicast Sessions
SDP has an attribute that allows RTP applications to specify an
address and a port associated with the 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 | Mux |
| | | | Category |
+----------------+------------------------------+-------+-----------+
| multicast- | Multicast RTCP port MUST be | B | IDENTICAL |
| rtcp | identical across all the | | |
| | "m=" lines | | |
| | | | |
+----------------+------------------------------+-------+-----------+
5.38 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 SRTP sessions for (VoIP applications.
+-----------+-----------------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | Category |
+-----------+-----------------------------------+-------+-----------+
| zrtp- | zrtp-hash attribute MUST be the | M | TRANSPORT |
| hash | one that corresponds to the "m=" | | |
| | line chosen for setting up the | | |
| | underlying transport flow | | |
| | | | |
+-----------+-----------------------------------+-------+-----------+
5.39 RFC6189 Attribute Analysis
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5.40. RFC4145: Connection-Oriented Media
[RFC4145] describes how to express media transport over TCP using
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 | Mux |
| | | | Category |
+------------+----------------------------------+-------+-----------+
| setup | The setup attribute MUST be the | B | TRANSPORT |
| | one that corresponds to the "m=" | | |
| | line chosen for setting up the | | |
| | underlying transport flow. | | |
| | | | |
| connection | The connection attribute MUST be | B | TRANSPORT |
| | the one that corresponds to the | | |
| | "m=" line chosen for setting up | | |
| | the underlying transport flow. | | |
| | | | |
+------------+----------------------------------+-------+-----------+
5.40 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.
+------+----------------------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | 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 | | |
| | | | |
+------+----------------------------------------+-------+-----------+
5.41 RFC6947 Attribute Analysis
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5.42. RFC7195: SDP Extension for Circuit Switched Bearers in PSTN
[RFC7195] describes use cases, requirements, and protocol extensions
for using 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 | Mux |
| | | | Category |
+-------------------------+-------------------+-------+-------------+
| cs- | Refer to notes | M | TBD |
| correlation:callerid | below | | |
| | | | |
| cs-correlation:uuie | Refer to notes | M | TBD |
| | below | | |
| | | | |
| cs-correlation:dtmf | Refer to notes | M | TBD |
| | below | | |
| | | | |
| cs- | Refer to notes | M | TBD |
| correlation:external | below | | |
| | | | |
+-------------------------+-------------------+-------+-------------+
5.42 RFC7195 Attribute Analysis
NOTE: [RFC7195] defines SDP attributes for establishing audio and
video media streams over circuit-switched bearers by defining a new
nettype value "PSTN". However, section 7.2 of
[I-D.ietf-mmusic-sdp-bundle-negotiation] requires the "c=" line
nettype value of "IN". If in future there exists a specification
that defines procedures to multiplex media streams over nettype
"PSTN", the multiplexing categories for attributes in this section
could be revisited.
5.43. RFC7272: IDMS Using the RTP Control Protocol (RTCP)
[RFC7272] defines a new RTCP Packet Type and an RTCP Extended Report
(XR) Block Type to be used for achieving Inter-Destination Media
Synchronization (IDMS).
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+------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+------------+---------------+-------+--------------+
| rtcp-idms | Not Impacted | M | NORMAL |
| | | | |
+------------+---------------+-------+--------------+
5.43 RFC7272 Attribute Analysis
5.44. RFC5159: Open Mobile Alliance (OMA) Broadcast (BCAST) SDP
Attributes
[RFC5159] provides descriptions of SDP attributes used by the Open
Mobile Alliance's Broadcast Service and Content Protection
specification.
+--------------------+-----------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+--------------------+-----------------------+-------+--------------+
| bcastversion | Not Impacted | S | NORMAL |
| | | | |
| stkmstream | Not Impacted | B | NORMAL |
| | | | |
| SRTPAuthentication | Needs further | M | TBD |
| | analysis | | |
| | | | |
| SRTPROCTxRate | Needs further | M | TBD |
| | analysis | | |
| | | | |
+--------------------+-----------------------+-------+--------------+
5.44 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 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 | Mux |
| | | | Category |
+------------------+-----------------------------+-------+----------+
| ike-setup | Unlikely to use IKE in the | B | CAUTION |
| | context of multiplexing | | |
| | | | |
| psk-fingerprint | Unlikely to use IKE in the | B | CAUTION |
| | context of multiplexing | | |
| | | | |
| ike-esp | Unlikely to use IKE in the | B | CAUTION |
| | context of multiplexing | | |
| | | | |
| ike-esp- | Unlikely to use IKE in the | B | CAUTION |
| udpencap | context of multiplexing | | |
| | | | |
+------------------+-----------------------------+-------+----------+
5.45 RFC6193 Attribute Analysis
5.46. RFC2326: Real Time Streaming Protocol
The Real Time Streaming Protocol, or RTSP, is an application-level
protocol for control over the delivery of data with real-time
properties. RTSP provides an extensible framework to enable
controlled, on-demand delivery of real-time data, such as audio and
video.
+---------+-------------------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | Category |
+---------+-------------------------------------+-------+-----------+
| etag | RTSP is not supported for RTP | B | CAUTION |
| | Stream multiplexing | | |
| | | | |
| range | RTSP is not supported for RTP | B | CAUTION |
| | Stream multiplexing | | |
| | | | |
| control | RTSP is not supported for RTP | B | CAUTION |
| | Stream multiplexing | | |
| | | | |
| mtag | RTSP is not supported for RTP | B | CAUTION |
| | Stream multiplexing | | |
| | | | |
+---------+-------------------------------------+-------+-----------+
5.46 RFC2326 Attribute Analysis
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NOTE: [RFC2326] 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. RFC6064: SDP and RTSP Extensions for 3GPP
The Packet-switched Streaming Service (PSS) and the Multimedia
Broadcast/Multicast Service (MBMS) defined by 3GPP use SDP and RTSP
with some extensions. [RFC6064] provides information about these
extensions and registers the RTSP and SDP extensions with IANA.
+--------------------------------+---------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+--------------------------------+---------------+-------+----------+
| X-predecbufsize | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| X-initpredecbufperiod | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| X-initpostdecbufperiod | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| X-decbyterate | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| 3gpp-videopostdecbufsize | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| framesize | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| 3GPP-Integrity-Key | Refer to | S | CAUTION |
| | notes below | | |
| | | | |
| 3GPP-SDP-Auth | Refer to | S | CAUTION |
| | notes below | | |
| | | | |
| 3GPP-SRTP-Config | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| alt | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| alt-default-id | Refer to | M | CAUTION |
| | notes below | | |
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| | | | |
| alt-group | Refer to | S | CAUTION |
| | notes below | | |
| | | | |
| 3GPP-Adaptation-Support | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| 3GPP-Asset-Information | Refer to | B | CAUTION |
| | notes below | | |
| | | | |
| mbms-mode | Refer to | B | CAUTION |
| | notes below | | |
| | | | |
| mbms-flowid | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| mbms-repair | Refer to | B | CAUTION |
| | notes below | | |
| | | | |
| 3GPP-QoE-Metrics | Refer to | M | CAUTION |
| | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Corruption | Refer to | M | CAUTION |
| duration | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Rebuffering | Refer to | M | CAUTION |
| duration | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Initial | Refer to | M | CAUTION |
| buffering duration | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Successive | Refer to | M | CAUTION |
| loss of RTP packets | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Frame rate | Refer to | M | CAUTION |
| deviation | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Jitter | Refer to | M | CAUTION |
| duration | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Content | Refer to | B | CAUTION |
| Switch Time | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Average Codec | Refer to | M | CAUTION |
| Bitrate | notes below | | |
| | | | |
| 3GPP-QoE-Metrics:Codec | Refer to | M | CAUTION |
| Information | notes below | | |
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| | | | |
| 3GPP-QoE-Metrics:Buffer | Refer to | M | CAUTION |
| Status | notes below | | |
| | | | |
+--------------------------------+---------------+-------+----------+
5.47 RFC6064 Attribute Analysis
NOTE: [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].
5.48. RFC3108: ATM SDP
[RFC3108] describes conventions for using SDP described for
controlling ATM Bearer Connections, and any associated ATM Adaptation
Layer (AAL).
+-----------------------+--------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+-----------------------+--------------------+-------+--------------+
| aalType | Refer to notes | B | CAUTION |
| | below | | |
| eecid | Refer to notes | B | CAUTION |
| | below | | |
| capability | Refer to notes | B | CAUTION |
| | below | | |
| qosClass | Refer to notes | B | CAUTION |
| | below | | |
| bcob | Refer to notes | B | CAUTION |
| | below | | |
| stc | Refer to notes | B | CAUTION |
| | below | | |
| upcc | Refer to notes | B | CAUTION |
| | below | | |
| atmQOSparms | Refer to notes | B | CAUTION |
| | below | | |
| atmTrfcDesc | Refer to notes | B | CAUTION |
| | below | | |
| abrParms | Refer to notes | B | CAUTION |
| | below | | |
| abrSetup | Refer to notes | B | CAUTION |
| | below | | |
| bearerType | Refer to notes | B | CAUTION |
| | below | | |
| lij | Refer to notes | B | CAUTION |
| | below | | |
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| anycast | Refer to notes | B | CAUTION |
| | below | | |
| cache | Refer to notes | B | CAUTION |
| | below | | |
| bearerSigIE | Refer to notes | B | CAUTION |
| | below | | |
| aalApp | Refer to notes | B | CAUTION |
| | below | | |
| cbrRate | Refer to notes | B | CAUTION |
| | below | | |
| sbc | Refer to notes | B | CAUTION |
| | below | | |
| clkrec | Refer to notes | B | CAUTION |
| | below | | |
| fec | Refer to notes | B | CAUTION |
| | below | | |
| prtfl | Refer to notes | B | CAUTION |
| | below | | |
| structure | Refer to notes | B | CAUTION |
| | below | | |
| cpsSDUsize | Refer to notes | B | CAUTION |
| | below | | |
| aal2CPS | Refer to notes | B | CAUTION |
| | below | | |
| aal2CPSSDUrate | Refer to notes | B | CAUTION |
| | below | | |
| aal2sscs3661unassured | Refer to notes | B | CAUTION |
| | below | | |
| aal2sscs3661assured | Refer to notes | B | CAUTION |
| | below | | |
| aal2sscs3662 | Refer to notes | B | CAUTION |
| | below | | |
| aal5sscop | Refer to notes | B | CAUTION |
| | below | | |
| atmmap | Refer to notes | B | CAUTION |
| | below | | |
| silenceSupp | Refer to notes | B | CAUTION |
| | below | | |
| ecan | Refer to notes | B | CAUTION |
| | below | | |
| gc | Refer to notes | B | CAUTION |
| | below | | |
| profileDesc | Refer to notes | B | CAUTION |
| | below | | |
| vsel | Refer to notes | B | CAUTION |
| | below | | |
| dsel | Refer to notes | B | CAUTION |
| | below | | |
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| fsel | Refer to notes | B | CAUTION |
| | below | | |
| onewaySel | Refer to notes | B | CAUTION |
| | below | | |
| codecconfig | Refer to notes | B | CAUTION |
| | below | | |
| isup_usi | Refer to notes | B | CAUTION |
| | below | | |
| uiLayer1_Prot | Refer to notes | B | CAUTION |
| | below | | |
| chain | Refer to notes | B | CAUTION |
| | below | | |
| | | | |
+-----------------------+--------------------+-------+--------------+
5.48 RFC3108 Attribute Analysis
NOTE: RFC3108 describes conventions for using 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 can be multiplexed into a bearer connection. For all
adaptation types (AAL1, AAL2 and AAL5), bearer connections can 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 can carry one or more real-time (e.g. VoIP) media sessions
with a life-cycle different from that of the underlying ATM
transport.
5.49. 3GPP TS 26.114
[R3GPPTS26.114] specifies IP multimedia subsystem: Media handling and
interaction
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+---------------------+--------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+---------------------+--------------------------+-------+----------+
| 3gpp_sync_info | Usage defined for the IP | M | NORMAL |
| | Multimedia Subsystem | | |
| | | | |
| 3gpp_MaxRecvSDUSize | Usage defined for the IP | M | NORMAL |
| | Multimedia Subsystem | | |
| | | | |
+---------------------+--------------------------+-------+----------+
5.49 3GPP TS 26.114 Attribute Analysis
5.50. 3GPP TS 183.063
[R3GPPTS183.063] Telecommunications and Internet converged Services
and Protocols for Advanced Networking (TISPAN);
+---------------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+---------------------+---------------+-------+--------------+
| PSCid | Not Impacted | S | NORMAL |
| | | | |
| bc_service | Not Impacted | S | NORMAL |
| | | | |
| bc_program | Not Impacted | S | NORMAL |
| | | | |
| bc_service_package | Not Impacted | S | NORMAL |
| | | | |
+---------------------+---------------+-------+--------------+
5.50 3GPP TS 183.063 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 | Mux |
| | | | Category |
+-----------------+-----------------------------+-------+-----------+
| secondary- | secondary-realm MUST be | M | TRANSPORT |
| realm | the one that corresponds to | | |
| | the "m=" line chosen for | | |
| | setting up the underlying | | |
| | transport flow | | |
| | | | |
| visited-realm | visited-realm MUST be the | M | TRANSPORT |
| | one that corresponds to the | | |
| | "m=" line chosen for | | |
| | setting up the underlying | | |
| | transport flow | | |
| | | | |
| omr-m-cksum | Not Impacted | M | NORMAL |
| | | | |
| omr-s-cksum | Not Impacted | M | NORMAL |
| | | | |
| omr-m-att | Not Impacted | M | NORMAL |
| | | | |
| omr-s-att | Not Impacted | M | NORMAL |
| | | | |
| omr-m-bw | Not Impacted | M | NORMAL |
| | | | |
| omr-s-bw | Not Impacted | M | NORMAL |
| | | | |
| omr-codecs | Not Impacted | M | NORMAL |
| | | | |
+-----------------+-----------------------------+-------+-----------+
5.53 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 | Mux Category |
+-----------------------+--------------------+-------+--------------+
| T38FaxVersion | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38MaxBitRate | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxFillBitRemoval | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxTranscodingMMR | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxTranscodingJBIG | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxRateManagement | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxMaxBuffer | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxMaxDatagram | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxUdpEC | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxMaxIFP | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxUdpECDepth | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38FaxUdpFECMaxSpan | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38ModemType | Refer to notes | M | TBD |
| | below | | |
| | | | |
| T38VendorInfo | Refer to notes | M | TBD |
| | below | | |
| | | | |
+-----------------------+--------------------+-------+--------------+
5.54 ITU T.38 Attribute Analysis
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NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation],
there exists no publicly available specification that defines
procedures for multiplexing/demultiplexing fax protocols flows over a
single 5-tuple. Once such a specification is available, the
multiplexing category assignments for the attributes in this section
could be revisited.
5.53. ITU-T Q.1970
[Q.1970] defines Bearer Independent Call Control (BICC) IP bearer
control protocol.
+-------+----------------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+-------+----------------------------------------+-------+----------+
| ipbcp | ipbcp version identifies type of IP | S | SPECIAL |
| | bearer control protocol (IPBCP) | | |
| | message used in BICC (ITU-T Q.1901) | | |
| | environment which are limited to | | |
| | single media payload. Refer to the | | |
| | pertinent ITU-T specifications while | | |
| | multiplexing | | |
| | | | |
+-------+----------------------------------------+-------+----------+
5.55 ITU-T Q.1970 Attribute Analysis
5.54. ITU-T H.248.15
ITU-T H.248.15 [H.248.15] defines Gateway Control Protocol SDP H.248
package attribute
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+----------+-------------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+----------+-------------------------------------+-------+----------+
| h248item | It is only applicable for signaling | B | SPECIAL |
| | 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 can 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 | | |
| | | | |
+----------+-------------------------------------+-------+----------+
5.56 ITU-T H.248.15 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 | Mux Category |
+----------------------+---------------------+-------+--------------+
| accept-types | Refer to notes | M | TBD |
| | below | | |
| | | | |
| accept-wrapped- | Refer to notes | M | TBD |
| types | below | | |
| | | | |
| max-size | Refer to notes | M | TBD |
| | below | | |
| | | | |
| path | Refer to notes | M | TBD |
| | below | | |
| | | | |
+----------------------+---------------------+-------+--------------+
5.57 RFC4975 Attribute Analysis
NOTE: As per section 9 of [I-D.ietf-mmusic-sdp-bundle-negotiation],
there exists no publicly available specification that defines
procedures for multiplexing/demultiplexing MRSP flows over a single
5-tuple. Once such a specification is available, the multiplexing
categories assignments for the attributes in this section could be
revisited.
5.56. Historical Attributes
This section specifies analysis for the attributes that are included
for historic usage alone by the [IANA].
+----------+----------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+----------+----------------------+-------+--------------+
| rtpred1 | Historic attributes | M | CAUTION |
| | | | |
| rtpred2 | Historic attributes | M | CAUTION |
| | | | |
+----------+----------------------+-------+--------------+
5.58 Historical Attribute Analysis
6. bwtype Attribute Analysis
This section specifies handling of specific bandwidth attributes when
used in multiplexing scenarios.
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6.1. RFC4566: SDP
[RFC4566] defines SDP that is intended for describing multimedia
sessions for the purposes of session announcement, session
invitation, and other forms of multimedia session initiation.
+-----------+------------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+-----------+------------------------------------+-------+----------+
| bwtype:CT | Not Impacted | S | NORMAL |
| | | | |
| bwtype:AS | For the media level usage, the | B | SUM |
| | aggregate of individual bandwidth | | |
| | values is considered | | |
| | | | |
+-----------+------------------------------------+-------+----------+
6.1 RFC4566 bwtype Analysis
6.2. RFC3556: SDP Bandwidth Modifiers for RTCP Bandwidth
[RFC3556] defines an extension to SDP to specify two additional
modifiers for the bandwidth attribute. These modifiers may be used
to specify the bandwidth allowed for RTCP packets in a RTP session.
+-----------+------------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+-----------+------------------------------------+-------+----------+
| bwtype:RS | Session level usage represents | B | SUM |
| | session aggregate and media level | | |
| | usage indicates SUM of the | | |
| | individual values while | | |
| | multiplexing | | |
| | | | |
| bwtype:RR | Session level usage represents | B | SUM |
| | session aggregate and media level | | |
| | usage indicates SUM of the | | |
| | individual values while | | |
| | multiplexing | | |
| | | | |
+-----------+------------------------------------+-------+----------+
6.2 RFC3556 bwtype Analysis
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6.3. RFC3890: Bandwidth Modifier for SDP
[RFC3890] defines 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 | Mux |
| | | | Category |
+-------------+----------------------------------+-------+----------+
| bwtype:TIAS | The usage of TIAS is not defined | B | SPECIAL |
| | under Offer/Answer usage. | | |
| | | | |
| maxprate | The usage of TIAS and maxprate | B | SPECIAL |
| | is not well defined under | | |
| | multiplexing | | |
| | | | |
+-------------+----------------------------------+-------+----------+
6.3 RFC3890 bwtype Analysis
NOTE: 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 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.
7. rtcp-fb Attribute Analysis
This section analyzes rtcp-fb SDP attributes.
7.1. 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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+---------+------------------------------+-------+------------------+
| Name | Notes | Level | Mux Category |
+---------+------------------------------+-------+------------------+
| ack | The attribute value MUST be | M | IDENTICAL-PER- |
| rpsi | same for a given codec | | PT |
| | configuration | | |
| | | | |
| ack | Feedback parameters MUST be | M | SPECIAL |
| app | handled in the app specific | | |
| | way when multiplexed | | |
| | | | |
| nack | The attribute value MUST be | M | IDENTICAL-PER- |
| | same for a given codec | | PT |
| | configuration | | |
| | | | |
| nack | The attribute value MUST be | M | IDENTICAL-PER- |
| pli | same for a given codec | | PT |
| | configuration | | |
| | | | |
| nack | The attribute value MUST be | M | IDENTICAL-PER- |
| sli | same for a given codec | | PT |
| | configuration | | |
| | | | |
| nack | The attribute value MUST be | M | IDENTICAL-PER- |
| rpsi | same for a given codec | | PT |
| | configuration | | |
| | | | |
| nack | Feedback parameters MUST be | M | SPECIAL |
| app | handled in the app specific | | |
| | way when multiplexed | | |
| | | | |
| trr- | The attribute value MUST be | M | IDENTICAL-PER- |
| int | same for a given codec | | PT |
| | configuration | | |
| | | | |
+---------+------------------------------+-------+------------------+
7.1 RFC4585 Attribute Analysis
7.2. RFC5104: Codec Control Messages in AVPF
[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
multipoint functionalities are in use. However, some are also usable
in smaller multicast environments and point-to-point calls.
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+------+---------------------------------+-------+------------------+
| Name | Notes | Level | Mux Category |
+------+---------------------------------+-------+------------------+
| ccm | The attribute value MUST be | M | IDENTICAL-PER- |
| | same for a given codec | | PT |
| | configuration | | |
| | | | |
+------+---------------------------------+-------+------------------+
7.2 RFC5104 Attribute Analysis
7.3. RFC6285: Unicast-Based Rapid Acquisition of Multicast RTP Sessions
(RAMS)
[RFC6285] describes a method using the existing RTP and 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 | Mux Category |
+--------+-------------------------------+-------+------------------+
| nack | The attribute value MUST be | M | IDENTICAL-PER- |
| rai | same for a given codec | | PT |
| | configuration | | |
| | | | |
+--------+-------------------------------+-------+------------------+
7.3 RFC6285 Attribute Analysis
7.4. RFC6679: ECN for RTP over UDP/IP
[RFC6679] specifies how Explicit Congestion Notification (ECN) can be
used with the RTP running over UDP, using the 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 STUN extension used in
the optional initialization method using ICE.
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+-----------------+-----------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | Category |
+-----------------+-----------------------------+-------+-----------+
| ecn-capable- | ECN markup are enabled at | M | IDENTICAL |
| rtp | the RTP session level | | |
| | | | |
| nack ecn | This attribute enables ECN | M | IDENTICAL |
| | at the RTP session level | | |
| | | | |
+-----------------+-----------------------------+-------+-----------+
7.4 RFC6679 Attribute Analysis
7.5. RFC6642: Third-Party Loss Report
In a large RTP session using the RTCP feedback mechanism defined in
[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] 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 SDP signaling is also
defined.
+---------+------------------------------+-------+------------------+
| Name | Notes | Level | Mux Category |
+---------+------------------------------+-------+------------------+
| nack | The attribute value MUST be | M | IDENTICAL-PER- |
| tllei | same for a given codec | | PT |
| | configuration | | |
| | | | |
| nack | The attribute value MUST be | M | IDENTICAL-PER- |
| pslei | same for a given codec | | PT |
| | configuration | | |
| | | | |
+---------+------------------------------+-------+------------------+
7.5 RFC6642 Attribute Analysis
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7.6. RFC5104: Codec Control Messages in AVPF
[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
multipoint functionalities are in use. However, some are also usable
in smaller multicast environments and point-to-point calls.
+--------+-------------------------------+-------+------------------+
| Name | Notes | Level | Mux Category |
+--------+-------------------------------+-------+------------------+
| ccm | The attribute value MUST be | M | IDENTICAL-PER- |
| fir | same for a given codec | | PT |
| | configuration | | |
| | | | |
| ccm | The attribute value MUST be | M | IDENTICAL-PER- |
| tmmbr | same for a given codec | | PT |
| | configuration | | |
| | | | |
| ccm | The attribute value MUST be | M | IDENTICAL-PER- |
| tstr | same for a given codec | | PT |
| | configuration | | |
| | | | |
| ccm | The attribute value MUST be | M | IDENTICAL-PER- |
| vbcm | same for a given codec | | PT |
| | configuration | | |
| | | | |
+--------+-------------------------------+-------+------------------+
7.6 RFC5104 Attribute Analysis
8. group Attribute Analysis
This section analyzes SDP "group" attribute semantics [RFC5888].
8.1. RFC5888: SDP Grouping Framework
[RFC5888] defines a framework to group "m" lines in SDP for different
purposes.
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+------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+------------+---------------+-------+--------------+
| group:LS | Not Impacted | S | NORMAL |
| | | | |
| group:FID | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+--------------+
8.1 RFC5888 Attribute Analysis
8.2. RFC3524: Mapping Media Streams to Resource Reservation Flows
[RFC3524] defines an extension to the 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 | Mux Category |
+------------+---------------+-------+--------------+
| group:SRF | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+--------------+
8.2 RFC3524 Attribute Analysis
8.3. RFC4091: ANAT Semantics
[RFC4091] defines ANAT semantics for the SDP grouping framework. The
ANAT semantics allow alternative types of network addresses to
establish a particular media stream.
+-------------+------------------------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+-------------+------------------------------+-------+--------------+
| group:ANAT | ANAT semantics is obsoleted | S | CAUTION |
| | | | |
+-------------+------------------------------+-------+--------------+
8.3 RFC4091 Attribute Analysis
8.4. RFC5956: FEC Grouping Semantics in SDP
[RFC5956] defines the semantics for grouping the associated source
and FEC-based (Forward Error Correction) repair flows in SDP. The
semantics defined in the document are to be used with the SDP
Grouping Framework [RFC5888]. These semantics allow the description
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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 RTP streams using SSRC multiplexing.
+---------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+---------------+---------------+-------+--------------+
| group:FEC-FR | Not Impacted | S | NORMAL |
| | | | |
+---------------+---------------+-------+--------------+
8.4 RFC5956 Attribute Analysis
8.5. RFC5583: Signaling Media Decoding Dependency in SDP
[RFC5583] defines semantics that allow for signaling the decoding
dependency of different media descriptions with the same media type
in 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 | Mux Category |
+-----------+----------------------------+-------+------------------+
| group:DDP | Not Impacted | S | NORMAL |
| | | | |
| depend | The attribute value MUST | M | IDENTICAL-PER- |
| lay | be same for a given codec | | PT |
| | configuration | | |
| | | | |
| depend | The attribute value MUST | M | IDENTICAL-PER- |
| mdc | be same for a given codec | | PT |
| | configuration | | |
| | | | |
+-----------+----------------------------+-------+------------------+
8.5 RFC5583 Attribute Analysis
8.6. RFC7104: Duplication Grouping Semantics in the SDP
[RFC7104] defines the semantics for grouping redundant streams in
SDP, The semantics defined in this document are to be used with the
SDP Grouping Framework. Grouping semantics at the SSRC)level are
also defined in this document for RTP streams using SSRC
multiplexing.
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+------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+------------+---------------+-------+--------------+
| group:DUP | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+--------------+
8.6 RFC7104 Attribute Analysis
9. ssrc-group Attribute Analysis
This section analyzes "ssrc-group" semantics.
9.1. 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.
+--------------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+--------------------+---------------+-------+--------------+
| ssrc-group:FID | Not Impacted | SR | NORMAL |
| | | | |
| ssrc-group:FEC | Not Impacted | SR | NORMAL |
| | | | |
| ssrc-group:FEC-FR | Not Impacted | SR | NORMAL |
| | | | |
+--------------------+---------------+-------+--------------+
9.1 RFC5576 Attribute Analysis
9.2. RFC7104: Duplication Grouping Semantics in the SDP
[RFC7104] defines the semantics for grouping redundant streams in
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 | Mux Category |
+-----------------+---------------+-------+--------------+
| ssrc-group:DUP | Not Impacted | SR | NORMAL |
| | | | |
+-----------------+---------------+-------+--------------+
9.2 RFC7104 Attribute Analysis
10. QoS Mechanism Token Analysis
This section analyzes QoS tokes specified with SDP.
10.1. RFC5432: QoS Mechanism Selection in SDP
[RFC5432] defines procedures to negotiate QOS mechanisms using the
SDP offer/answer model.
+------+----------------------------------------+-------+-----------+
| Name | Notes | Level | Mux |
| | | | Category |
+------+----------------------------------------+-------+-----------+
| rsvp | rsvp attribute MUST be the one that | B | TRANSPORT |
| | corresponds to the "m=" line chosen | | |
| | for setting up the underlying | | |
| | transport flow | | |
| | | | |
| nsis | rsvp attribute MUST be the one that | B | TRANSPORT |
| | corresponds to the "m=" line chosen | | |
| | for setting up the underlying | | |
| | transport | | |
| | | | |
+------+----------------------------------------+-------+-----------+
10.1 RFC5432 Attribute Analysis
NOTE: A single Differentiated Services Code Point (DSCP) code point
per flow being multiplexed doesn't impact multiplexing since QOS
mechanisms are signaled/scoped per flow. For scenarios that involve
having different DSCP code points for packets being transmitted over
the same 5-tuple, issues as discussed in [RFC7657] need to be taken
into consideration.
11. k= Attribute Analysis
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11.1. RFC4566: SDP
[RFC4566] defines SDP that is intended for describing multimedia
sessions for the purposes of session announcement, session
invitation, and other forms of multimedia session initiation.
+------+-----------------------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+------+-----------------------------------------+-------+----------+
| k= | It is not recommended to use this | S | CAUTION |
| | attribute under multiplexing | | |
| | | | |
+------+-----------------------------------------+-------+----------+
11.1 RFC4566 Attribute Analysis
12. content Attribute Analysis
12.1. RFC4796
[RFC4796] defines a new 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 | Mux 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 |
| | | | |
+------------------+---------------+-------+--------------+
12.1 RFC4796 Attribute Analysis
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12.2. 3GPP TS 24.182
[R3GPPTS24.182] specifies IP multimedia subsystem Custom Alerting
tones
+-------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+-------------+---------------+-------+--------------+
| g.3gpp.cat | Not Impacted | M | NORMAL |
| | | | |
+-------------+---------------+-------+--------------+
12.2 3GPP TS 24.182 Attribute Analysis
12.3. 3GPP TS 24.183
[R3GPPTS24.183] specifies IP multimedia subsystem Custom Ringing
Signal
+-------------+---------------+-------+--------------+
| Name | Notes | Level | Mux Category |
+-------------+---------------+-------+--------------+
| g.3gpp.crs | Not Impacted | M | NORMAL |
| | | | |
+-------------+---------------+-------+--------------+
12.3 3GPP TS 24.183 Attribute Analysis
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.
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+--------------------+---------------------------+-------+----------+
| Name | Notes | Level | Mux |
| | | | Category |
+--------------------+---------------------------+-------+----------+
| audio/ulpfec | Not recommended for | M | CAUTION |
| | multiplexing due to reuse | | |
| | of SSRCs | | |
| | | | |
| video/ulpfec | Not recommended for | M | CAUTION |
| | multiplexing due to reuse | | |
| | of SSRCs | | |
| | | | |
| text/ulpfec | Not recommended for | M | CAUTION |
| | multiplexing due to reuse | | |
| | of SSRCs | | |
| | | | |
| application/ulpfec | Not recommended for | M | CAUTION |
| | multiplexing due to reuse | | |
| | of SSRCs | | |
| | | | |
+--------------------+---------------------------+-------+----------+
13.1 RFC5109 Payload Format Analysis
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.
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.
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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
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.
o A set of potential configurations ("a=pcfg") provided by the
offerer to indicate which combinations 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.
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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 simplify Answerer's procedure to choose potential configurations
that are consistent across all the multiplexed 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 to ensure the right
multiplexing behavior.
Although it is possible to analyze the various potential
configurations in multiplexed 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
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 constructing 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").
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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 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
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.
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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.
14.3. RFC6871 Analysis
[RFC6871] extends the 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.
14.3.1. Recommendation: Dealing with Payload Type Numbers
[RFC6871] 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 14.2.1, the use of identical
configuration numbers for compatible configurations in different
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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 multiplexing.
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 96. 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.
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14.3.2. Recommendation: Dealing with Latent Configurations
[RFC6871] 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 multiplexed media, since it requires the use of
unique configuration numbers across the SDP. Taken together, this
means there is no well-defined way to indicate supported combinations
of latent configurations, or combinations of latent and potential
configurations with multiplexed 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.]
Section 15.1 defines a new subregistry to be added by the IANA for
identifying the initial registrations for various multiplexing
categories applicable, as proposed in this document.
IANA is also requested to add a new column named "Mux Category" to
several of the subregistries in the "Session Description Protocol
(SDP) Parameters" registry. The tables in Section 15.2 identify name
of an entry in the existing subregistry and specify the value to be
put in the new "Mux Category" column of the associated IANA registry.
15.1. New 'Multiplexing Categories' subregistry
A new sub-registry needs to be defined called the "Multiplexing
Categories", with the following registrations created initially:
"NORMAL", "CAUTION", "IDENTICAL", "TRANSPORT", "SUM", "INHERIT",
"IDENTICAL-PER-PT", "SPECIAL" and "TBD" as defined in this document.
Initial value registration for "Multiplexing Categories".
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+-------------------------+-----------+
| Multiplexing Categories | Reference |
+-------------------------+-----------+
| NORMAL | RFCXXXX |
| CAUTION | RFCXXXX |
| IDENTICAL | RFCXXXX |
| TRANSPORT | RFCXXXX |
| SUM | RFCXXXX |
| INHERIT | RFCXXXX |
| IDENTICAL-PER-PT | RFCXXXX |
| SPECIAL | RFCXXXX |
| TBD | RFCXXXX |
+-------------------------+-----------+
Further entries can be registered using Standard Actions policies
outlined in [RFC5226], which requires IESG review and approval and
standards-track IETF RFC publication.
Each registration needs to indicate the multiplexing category value
to be added to the "Multiplexing Categories" subregistry as defined
in this section.
Such a registration MUST also indicate the applicability of the newly
defined multiplexing category value to various subregistries defined
at the "Session Description Protocol (SDP) Parameters" registry.
15.2. 'Mux Category' column for subregistries
Each sub-section identifies a subregistry in the "Session Description
Protocol (SDP) Parameters" registry. The tables list the column that
identifies the SDP attribute name/Token/Value from the corresponding
subregistries and the values to be used for the new "Mux Category"
column to be added.
For the entries in the existing subregistries, under the "Session
Description Protocol (SDP) Parameters" registry, that lack a value
for the "Mux Category" in this specification will get a value of
"TBD".
The registration policy for updates to the 'Mux Category' column
values for existing parameters, or when registering new parameters,
are beyond the scope of this document. The registration policy for
the affected table is defined in [I-D.ietf-mmusic-rfc4566bis].
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15.2.1. Table: SDP bwtype
The following values are to be added to the 'SDP bwtype' subregistry
in the "Session Description Protocol (SDP) Parameters" registry. The
references should be updated to point at this RFC as well as the
previous references.
+----------+--------------+
| SDP Name | Mux Category |
+----------+--------------+
| CT | NORMAL |
| AS | SUM |
| RS | SUM |
| RR | SUM |
| TIAS | SPECIAL |
+----------+--------------+
15.2.2. Table: att-field (session level)
The following values are to be added to the "att-field (session
level)" subregistry in the "Session Description Protocol (SDP)
Parameters" registry. The references should be updated to point at
this RFC as well as the previous references.
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+---------------------+--------------+
| 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 | SPECIAL |
| group | NORMAL |
| ice-lite | NORMAL |
| ice-options | NORMAL |
| bcastversion | NORMAL |
| 3GPP-Integrity-Key | CAUTION |
| 3GPP-SDP-Auth | CAUTION |
| alt-group | CAUTION |
| PSCid | NORMAL |
| bc_service | NORMAL |
| bc_program | NORMAL |
| bc_service_package | NORMAL |
| sescap | CAUTION |
| rtsp-ice-d-m | TBD |
+---------------------+--------------+
15.2.3. Table: att-field (both session and media level)
The following values are to be added to the "att-field (both session
and media level)" subregistry in the "Session Description Protocol
(SDP) Parameters" registry. The references should be updated to
point at this RFC as well as the previous references.
NOTE: The attributes from draft-ietf-rmt-flute-sdp ('flute-tsi',
'flute-ch', 'FEC-declaration', 'FEC-OTI-extension', 'content-desc')
were not analyzed for their multiplexing behavior due to the expired
status of the draft. For purposes of this specification, the
multiplexing category of 'TBD' is assigned.
+-------------------------+-------------------+
| SDP Name | Mux Category |
+-------------------------+-------------------+
| recvonly | NORMAL |
| sendrecv | NORMAL |
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| sendonly | NORMAL |
| sdplang | NORMAL |
| lang | NORMAL |
| h248item | SPECIAL |
| sqn | NORMAL |
| cdsc | NORMAL |
| cpar | INHERIT |
| cparmin | SPECIAL |
| cparmax | SPECIAL |
| rtcp-xr | NORMAL |
| maxprate | SPECIAL |
| setup | TRANSPORT |
| connection | TRANSPORT |
| 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 |
| extmap | SPECIAL |
| qos-mech-send | TRANSPORT |
| qos-mech-recv | TRANSPORT |
| csup | NORMAL |
| creq | NORMAL |
| acap | INHERIT |
| tcap | INHERIT |
| 3GPP-QoE-Metrics | CAUTION |
| 3GPP-Asset-Information | CAUTION |
| mbms-mode | CAUTION |
| mbms-repair | CAUTION |
| ike-setup | IDENTICAL |
| psk-fingerprint | IDENTICAL |
| multicast-rtcp | IDENTICAL |
| rmcap | IDENTICAL-PER-PT |
| omcap | NORMAL |
| mfcap | IDENTICAL-PER-PT |
| mscap | INHERIT |
| 3gpp.iut.replication | TBD |
| bcap | INHERIT |
| ccap | IDENTICAL |
| icap | NORMAL |
| 3gpp_sync_info | NORMAL |
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| 3gpp_MaxRecvSDUSize | NORMAL |
| etag | CAUTION |
| duplication-delay | NORMAL |
| range | CAUTION |
| control | CAUTION |
| mtag | CAUTION |
| ts-refclk | NORMAL |
| mediaclk | NORMAL |
| calgextmap | NORMAL |
+-------------------------+-------------------+
15.2.4. Table: att-field (media level only)
The following values are to be added to the "att-field (media level
only)" registry in the "Session Description Protocol (SDP)
Parameters" registry. The references should be updated to point at
this RFC as well as the previous references.
+---------------------------+-------------------+
| SDP Name | Mux Category |
+---------------------------+-------------------+
| 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 | CAUTION |
| rtpred2 | CAUTION |
| T38FaxVersion | TBD |
| T38MaxBitRate | TBD |
| T38FaxFillBitRemoval | TBD |
| T38FaxTranscodingMMR | TBD |
| T38FaxTranscodingJBIG | TBD |
| T38FaxRateManagement | TBD |
| T38FaxMaxBuffer | TBD |
| T38FaxMaxDatagram | TBD |
| T38FaxUdpEC | TBD |
| maxptime | IDENTICAL-PER-PT |
| des | CAUTION |
| curr | CAUTION |
| conf | CAUTION |
| mid | NORMAL |
| rtcp | TRANSPORT |
| rtcp-fb | IDENTICAL-PER-PT |
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| label | NORMAL |
| T38VendorInfo | TBD |
| crypto | TRANSPORT |
| eecid | CAUTION |
| aalType | CAUTION |
| capability | CAUTION |
| qosClass | CAUTION |
| bcob | CAUTION |
| stc | CAUTION |
| upcc | CAUTION |
| atmQOSparms | CAUTION |
| atmTrfcDesc | CAUTION |
| abrParms | CAUTION |
| abrSetup | CAUTION |
| bearerType | CAUTION |
| lij | CAUTION |
| anycast | CAUTION |
| cache | CAUTION |
| bearerSigIE | CAUTION |
| aalApp | CAUTION |
| cbrRate | CAUTION |
| sbc | CAUTION |
| clkrec | CAUTION |
| fec | CAUTION |
| prtfl | CAUTION |
| structure | CAUTION |
| cpsSDUsize | CAUTION |
| all2CPS | CAUTION |
| all2CPSSDUrate | CAUTION |
| aal2sscs3661unassured | CAUTION |
| aal2sscs3661assured | CAUTION |
| aal2sscs3662 | CAUTION |
| aal5sscop | CAUTION |
| atmmap | CAUTION |
| silenceSupp | CAUTION |
| ecan | CAUTION |
| gc | CAUTION |
| profileDesc | CAUTION |
| vsel | CAUTION |
| dsel | CAUTION |
| fsel | CAUTION |
| onewaySel | CAUTION |
| codecconfig | CAUTION |
| isup_usi | CAUTION |
| uiLayer1_Prot | CAUTION |
| chain | CAUTION |
| floorctrl | TBD |
| confid | NORMAL |
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| userid | NORMAL |
| floorid | NORMAL |
| FEC | NORMAL |
| accept-types | TBD |
| accept-wrapped-types | TBD |
| max-size | TBD |
| path | TBD |
| dccp-service-code | CAUTION |
| rtcp-mux | IDENTICAL |
| candidate | TRANSPORT |
| ice-mismatch | NORMAL |
| remote-candidates | TRANSPORT |
| SRTPAuthentication | TBD |
| SRTPROCTxRate | TBD |
| rtcp-rsize | IDENTICAL |
| file-selector | TBD |
| file-transfer-id | TBD |
| file-disposition | TBD |
| file-date | TBD |
| file-icon | TBD |
| file-range | TBD |
| depend | IDENTICAL-PER-PT |
| ssrc | NORMAL |
| ssrc-group | NORMAL |
| rtcp-unicast | IDENTICAL |
| pcfg | SPECIAL |
| acfg | SPECIAL |
| zrtp-hash | TRANSPORT |
| X-predecbufsize | CAUTION |
| X-initpredecbufperiod | CAUTION |
| X-initpostdecbufperiod | CAUTION |
| X-decbyterate | CAUTION |
| 3gpp-videopostdecbufsize | CAUTION |
| framesize | CAUTION |
| 3GPP-SRTP-Config | CAUTION |
| alt | CAUTION |
| alt-default-id | CAUTION |
| 3GPP-Adaption-Support | CAUTION |
| mbms-flowid | CAUTION |
| fec-source-flow | SPECIAL |
| fec-repair-flow | SPECIAL |
| repair-window | SPECIAL |
| rams-updates | CAUTION |
| imageattr | IDENTICAL-PER-PT |
| cfw-id | NORMAL |
| portmapping-req | CAUTION |
| ecn-capable-rtp | IDENTICAL |
| visited-realm | TRANSPORT |
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| secondary-realm | TRANSPORT |
| omr-s-cksum | NORMAL |
| omr-m-cksum | NORMAL |
| omr-codecs | NORMAL |
| omr-m-att | NORMAL |
| omr-s-att | NORMAL |
| omr-m-bw | NORMAL |
| omr-s-bw | NORMAL |
| msrp-cema | TBD |
| dccp-port | CAUTION |
| resource | NORMAL |
| channel | NORMAL |
| cmid | NORMAL |
| content | NORMAL |
| lcfg | SPECIAL |
| loopback | NORMAL |
| loopback-source | NORMAL |
| loopback-mirror | NORMAL |
| chatroom | TBD |
| altc | TRANSPORT |
| T38FaxMaxIFP | TBD |
| T38FaxUdpECDepth | TBD |
| T38FaxUdpFECMaxSpan | TBD |
| T38ModemType | TBD |
| cs-correlation | TBD |
| rtcp-idms | NORMAL |
+---------------------------+-------------------+
15.2.5. Table: att-field (source level)
The following values are to be added to the "att-field (source
level)" registry in the "Session Description Protocol (SDP)
Parameters" registry. The references should be updated to point at
this RFC as well as the previous references.
+----------------+-------------------+
| SDP Name | Mux Category |
+----------------+-------------------+
| cname | NORMAL |
| previous-ssrc | NORMAL |
| fmtp | IDENTICAL-PER-PT |
| ts-refclk | NORMAL |
| mediaclk | NORMAL |
+----------------+-------------------+
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15.2.6. Table: content SDP Parameters
The following values are to be added to the "content SDP Parameters"
subregistry in the "Session Description Protocol (SDP) Parameters"
registry. 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 |
| g.3gpp.cat | NORMAL |
| g.3gpp.crs | NORMAL |
+-------------+--------------+
15.2.7. Table: Semantics for the 'group' SDP Attribute
The following values are to be added to the "Semantics for the
"group" SDP Attribute" subregistry in the "Session Description
Protocol (SDP) Parameters" registry. The references should be
updated to point at this RFC as well as the previous references.
+---------+--------------+
| Token | Mux Category |
+---------+--------------+
| LS | NORMAL |
| FID | NORMAL |
| SRF | NORMAL |
| ANAT | CAUTION |
| FEC | NORMAL |
| FEC-FR | NORMAL |
| CS | NORMAL |
| DDP | NORMAL |
| DUP | NORMAL |
+---------+--------------+
15.2.8. Table: 'rtcp-fb' Attribute Values
The following values are to be added to the " 'rtcp-fb' Attribute
Values" subregistry in the "Session Description Protocol (SDP)
Parameters" registry. The references should be updated to point at
this RFC as well as the previous references.
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+------------+-------------------+
| Value Name | Mux Category |
+------------+-------------------+
| ack | IDENTICAL-PER-PT |
| app | SPECIAL |
| ccm | IDENTICAL-PER-PT |
| nack | IDENTICAL-PER-PT |
| trr-int | IDENTICAL-PER-PT |
+------------+-------------------+
15.2.9. Table: 'ack' and 'nack' Attribute Values
The following values are to be added to the " 'ack' and 'nack'
Attribute Values" subregistry in the "Session Description Protocol
(SDP) Parameters" registry. The references should be updated to
point at this RFC as well as the previous references.
+------------+-------------------+
| Value Name | Mux Category |
+------------+-------------------+
| sli | IDENTICAL-PER-PT |
| pli | IDENTICAL-PER-PT |
| rpsi | IDENTICAL-PER-PT |
| app | SPECIAL |
| rai | IDENTICAL-PER-PT |
| tllei | IDENTICAL-PER-PT |
| pslei | IDENTICAL-PER-PT |
| ecn | IDENTICAL |
+------------+-------------------+
15.2.10. Table: 'depend' SDP Attribute Values
The following values are to be added to the " 'depend' SDP Attribute
Values" subregistry in the "Session Description Protocol (SDP)
Parameters" registry. The references should be updated to point at
this RFC as well as the previous references.
+-------+-------------------+
| Token | Mux Category |
+-------+-------------------+
| lay | IDENTICAL-PER-PT |
| mdc | IDENTICAL-PER-PT |
+-------+-------------------+
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15.2.11. Table: 'cs-correlation' Attribute Values
The following values are to be added to the " "cs-correlation"
Attribute Values" subregistry in the "Session Description Protocol
(SDP) Parameters" registry. The references should be updated to
point at this RFC as well as the previous references.
+-----------+--------------+
| Value | Mux Category |
+-----------+--------------+
| callerid | TBD |
| uuie | TBD |
| dtmf | TBD |
| external | TBD |
+-----------+--------------+
15.2.12. Table: Semantics for the 'ssrc-group' SDP Attribute
The following values are to be added to the Semantics for the
"Semantics for the "ssrc-group" SDP Attribute" subregistry in the
"Session Description Protocol (SDP) Parameters" registry. 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 |
+---------+--------------+
15.2.13. Table: SDP/RTSP key management protocol identifiers
The following values are to be added to the "SDP/RTSP key management
protocol identifiers" subregistry in the "Session Description
Protocol (SDP) Parameters" registry. The references should be
updated to point at this RFC as well as the previous references.
+------------+--------------+
| Value Name | Mux Category |
+------------+--------------+
| mikey | IDENTICAL |
+------------+--------------+
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15.2.14. Table: Codec Control Messages
The following values are to be added to the "Codec Control Messages"
subregistry in the "Session Description Protocol (SDP) Parameters"
registry. 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 |
+------------+-------------------+
15.2.15. Table: QoS Mechanism Tokens
The following values are to be added to the "QoS Mechanism Tokens"
subregistry in the "Session Description Protocol (SDP) Parameters"
registry. The references should be updated to point at this RFC as
well as the previous references.
+---------------+--------------+
| QoS Mechanism | Mux Category |
+---------------+--------------+
| rsvp | TRANSPORT |
| nsis | TRANSPORT |
+---------------+--------------+
15.2.16. Table: SDP Capability Negotiation Option Tags
The following values are to be added to the "SDP Capability
Negotiation Option Tags" subregistry in the "Session Description
Protocol (SDP) Parameters" registry. The references should be
updated to point at this RFC as well as the previous references.
+------------+--------------+
| Option Tag | Mux Category |
+------------+--------------+
| cap-v0 | NORMAL |
| med-v0 | NORMAL |
| bcap-v0 | NORMAL |
| ccap-v0 | NORMAL |
| icap-v0 | NORMAL |
+------------+--------------+
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15.2.17. Table: Timestamp Reference Clock Source Parameters
The following values are to be added to the "Timestamp Reference
Clock Source Parameters" subregistry in the "Session Description
Protocol (SDP) Parameters" registry. 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 |
+----------+--------------+
15.2.18. Table: Media Clock Source Parameters
The following values are to be added to the "Media Clock Source
Parameters" subegistry in the "Session Description Protocol (SDP)
Parameters" registry. 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
The primary security for RTP including the way it is used here is
described in [RFC3550] and [RFC3711].
When multiplexing SDP attributes with the category "CAUTION", the
implementations should be aware of possible issues as described in
this specification.
17. Acknowledgments
I would like to thank Cullen Jennings, Flemming Andreasen for
suggesting the categories, contributing text and reviewing the draft.
I would also link to thank Magnus Westerlund, Christer Holmberg,
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Jonathan Lennox, Bo Burman, Ari Keranen, and Dan Wing 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(5.24,5.32,5.33,14), Rohan
Mahy(5.57), Eric Burger(5.26),Christian Huitema(5.14), Christer
Holmberg(5.21,5.26,5.51,5.52), Richard Ejzak (5.44,5.53,5.54), Colin
Perkins(5.7,5.8,5.9,5.58), Magnus
Westerlund(5.2,5.3,5.9,5.27,5.47,6.1,6.2,6.3,8.3,7), Roni
Evens(5.12,5.27,8.4), Subha Dhesikan(5.6,10), Dan
Wing(5.7,5.12,5.35,5.39,5.45), Cullen Jennings (5.40), Ali C
Begen(5.1,5.20,5.22,5.25,5.38,7.3,8.2,8.4,8.6,9.2,13.1), Bo Burman
(7.2,7.6), Charles Eckel(5.15,5.27,5.28,9.1,8.5), Paul Kyzivat(5.24),
Ian Johansson(5.15), Saravanan Shanmugham(5.11), Paul E Jones(5.30),
Rajesh Kumar(5.48), Jonathan Lennox(5.36,5,15,9.1,11.1), Mo
Zanaty(5.4,5.5,5.23,8.1,8.3,8.5,12.1), Christian Huitema (5.14), Qin
Wu (5.47 PM-Dir review), Hans Stokking(5.43,5.16), Christian Groves
(5.48,5.55), Thomas Stach.
I would like to thank Chris Lonvick for the SECDIR review, Dan
Romascanu for th Gen-ART review and Sabrina Tanamal for the IANA
review.
Thanks to Ben Campbell for AD review suggestions. Thanks to Spencer
Dawkins, Stephen Farrel, Alissa Cooper, Mirja Kuehlewind and the
entire IESG experts for their reviews.
18. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes draft-ietf-mmusic-sdp-mux-attributes-16
o Added a clarification note on when to encode IDENTICAL attributes
as suggested by Christer.
Changes draft-ietf-mmusic-sdp-mux-attributes-15
o Updated Mux category for floorctrl to TBD
Changes draft-ietf-mmusic-sdp-mux-attributes-14
o Incorporated Comments from IESG review :
* Updated security considerations section to fix the
incositencies (Spencer's review)
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* Updated section 5.36 to align the text with 5.39 (Stephen's
review)
* Updated IANA registration section to make RFC4566bis a
informative dependency (IETF 98 followup)
* Updated Section 5 to expand 'B' level SDP attributes (Dan's
review)
Changes from draft-ietf-mmusic-sdp-mux-attributes-10 - draft-ietf-
mmusic-sdp-mux-attributes-13
o Incorporated Comments from WGLC review and AD Evaluation
Changes from draft-ietf-mmusic-sdp-mux-attributes-10
o Incorporated Comments from Bo Burman for publication request
Changes from draft-ietf-mmusic-sdp-mux-attributes-08 to draft-ietf-
mmusic-sdp-mux-attributes-10
o Minor nits and version update to advert expiration
Changes from draft-ietf-mmusic-sdp-mux-attributes-06 to draft-ietf-
mmusic-sdp-mux-attributes-08
o Assigned TBD category to all the attributes for whom there exists
no specification on multiplexing behavior over the underlying
transport protocol today.
o Incorporated comments from Flemming and Ari (post last call)
Changes from draft-ietf-mmusic-sdp-mux-attributes-06
o Incorporated last call review comments from Thomas Stach and Ari
Keranen.
o Fixed more nits to prep for the LastCall.
Changes from draft-ietf-mmusic-sdp-mux-attributes-05
o Incorporated review comments from Christian Grooves and Ari
Keranen.
o Fixed more nits to prep for the LastCall.
Changes from draft-ietf-mmusic-sdp-mux-attributes-04
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o Fixed minor nits overall.
o Updated Acknowledgement Sections
o Last Call Version.
Changes from draft-ietf-mmusic-sdp-mux-attributes-03
o More re-work on the IANA section.
o Clean ups preparing for the last call.
Changes from draft-ietf-mmusic-sdp-mux-attributes-02
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.
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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.
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.
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Changes from draft-nandakumar-mmusic-mux-attributes-00
o Added new section for dealing with FEC payload types.
19. References
19.1. Normative References
[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-54 (work in progress), December 2018.
[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, DOI 10.17487/RFC4566,
July 2006, <https://www.rfc-editor.org/info/rfc4566>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
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-rfc4566bis]
Begen, A., Kyzivat, P., Perkins, C., and M. Handley, "SDP:
Session Description Protocol", draft-ietf-mmusic-
rfc4566bis-37 (work in progress), August 2019.
[IANA] "Session Description Protocol (SDP) Parameters",
<http://www.iana.org/assignments/sdp-parameters/sdp-
parameters.xml>.
[Q.1970] "Q.1970 : BICC IP bearer control protocol",
<https://www.itu.int/rec/T-REC-Q.1970-200609-I/en>.
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[R3GPPTS183.063]
"TISPAN - IMS based ITPV Stage 3 specification.",
<http://www.etsi.org/deliver/
etsi_ts/183000_183099/183063/02.01.00_60/
ts_183063v020100p.pdf>.
[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.3gpp.org/DynaReport/26114.htm>.
[RFC2326] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
Streaming Protocol (RTSP)", RFC 2326,
DOI 10.17487/RFC2326, April 1998,
<https://www.rfc-editor.org/info/rfc2326>.
[RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the
Session Description Protocol (SDP) for ATM Bearer
Connections", RFC 3108, DOI 10.17487/RFC3108, May 2001,
<https://www.rfc-editor.org/info/rfc3108>.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<https://www.rfc-editor.org/info/rfc3264>.
[RFC3312] Camarillo, G., Ed., Marshall, W., Ed., and J. Rosenberg,
"Integration of Resource Management and Session Initiation
Protocol (SIP)", RFC 3312, DOI 10.17487/RFC3312, October
2002, <https://www.rfc-editor.org/info/rfc3312>.
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[RFC3407] Andreasen, F., "Session Description Protocol (SDP) Simple
Capability Declaration", RFC 3407, DOI 10.17487/RFC3407,
October 2002, <https://www.rfc-editor.org/info/rfc3407>.
[RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to
Resource Reservation Flows", RFC 3524,
DOI 10.17487/RFC3524, April 2003,
<https://www.rfc-editor.org/info/rfc3524>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <https://www.rfc-editor.org/info/rfc3550>.
[RFC3556] Casner, S., "Session Description Protocol (SDP) Bandwidth
Modifiers for RTP Control Protocol (RTCP) Bandwidth",
RFC 3556, DOI 10.17487/RFC3556, July 2003,
<https://www.rfc-editor.org/info/rfc3556>.
[RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
in Session Description Protocol (SDP)", RFC 3605,
DOI 10.17487/RFC3605, October 2003,
<https://www.rfc-editor.org/info/rfc3605>.
[RFC3611] Friedman, T., Ed., Caceres, R., Ed., and A. Clark, Ed.,
"RTP Control Protocol Extended Reports (RTCP XR)",
RFC 3611, DOI 10.17487/RFC3611, November 2003,
<https://www.rfc-editor.org/info/rfc3611>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004,
<https://www.rfc-editor.org/info/rfc3711>.
[RFC3890] Westerlund, M., "A Transport Independent Bandwidth
Modifier for the Session Description Protocol (SDP)",
RFC 3890, DOI 10.17487/RFC3890, September 2004,
<https://www.rfc-editor.org/info/rfc3890>.
[RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network
Address Types (ANAT) Semantics for the Session Description
Protocol (SDP) Grouping Framework", RFC 4091,
DOI 10.17487/RFC4091, June 2005,
<https://www.rfc-editor.org/info/rfc4091>.
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[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
DOI 10.17487/RFC4145, September 2005,
<https://www.rfc-editor.org/info/rfc4145>.
[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, DOI 10.17487/RFC4567, July
2006, <https://www.rfc-editor.org/info/rfc4567>.
[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
Description Protocol (SDP) Security Descriptions for Media
Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006,
<https://www.rfc-editor.org/info/rfc4568>.
[RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol
(SDP) Source Filters", RFC 4570, DOI 10.17487/RFC4570,
July 2006, <https://www.rfc-editor.org/info/rfc4570>.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572,
DOI 10.17487/RFC4572, July 2006,
<https://www.rfc-editor.org/info/rfc4572>.
[RFC4574] Levin, O. and G. Camarillo, "The Session Description
Protocol (SDP) Label Attribute", RFC 4574,
DOI 10.17487/RFC4574, August 2006,
<https://www.rfc-editor.org/info/rfc4574>.
[RFC4583] Camarillo, G., "Session Description Protocol (SDP) Format
for Binary Floor Control Protocol (BFCP) Streams",
RFC 4583, DOI 10.17487/RFC4583, November 2006,
<https://www.rfc-editor.org/info/rfc4583>.
[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,
DOI 10.17487/RFC4585, July 2006,
<https://www.rfc-editor.org/info/rfc4585>.
[RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description
Protocol (SDP) Content Attribute", RFC 4796,
DOI 10.17487/RFC4796, February 2007,
<https://www.rfc-editor.org/info/rfc4796>.
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[RFC4975] Campbell, B., Ed., Mahy, R., Ed., and C. Jennings, Ed.,
"The Message Session Relay Protocol (MSRP)", RFC 4975,
DOI 10.17487/RFC4975, September 2007,
<https://www.rfc-editor.org/info/rfc4975>.
[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
"Codec Control Messages in the RTP Audio-Visual Profile
with Feedback (AVPF)", RFC 5104, DOI 10.17487/RFC5104,
February 2008, <https://www.rfc-editor.org/info/rfc5104>.
[RFC5109] Li, A., Ed., "RTP Payload Format for Generic Forward Error
Correction", RFC 5109, DOI 10.17487/RFC5109, December
2007, <https://www.rfc-editor.org/info/rfc5109>.
[RFC5159] Dondeti, L., Ed. and A. Jerichow, "Session Description
Protocol (SDP) Attributes for Open Mobile Alliance (OMA)
Broadcast (BCAST) Service and Content Protection",
RFC 5159, DOI 10.17487/RFC5159, March 2008,
<https://www.rfc-editor.org/info/rfc5159>.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
DOI 10.17487/RFC5245, April 2010,
<https://www.rfc-editor.org/info/rfc5245>.
[RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP
Header Extensions", RFC 5285, DOI 10.17487/RFC5285, July
2008, <https://www.rfc-editor.org/info/rfc5285>.
[RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of
Service (QoS) Mechanism Selection in the Session
Description Protocol (SDP)", RFC 5432,
DOI 10.17487/RFC5432, March 2009,
<https://www.rfc-editor.org/info/rfc5432>.
[RFC5506] Johansson, I. and M. Westerlund, "Support for Reduced-Size
Real-Time Transport Control Protocol (RTCP): Opportunities
and Consequences", RFC 5506, DOI 10.17487/RFC5506, April
2009, <https://www.rfc-editor.org/info/rfc5506>.
[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,
DOI 10.17487/RFC5547, May 2009,
<https://www.rfc-editor.org/info/rfc5547>.
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[RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol
(SDP)", RFC 5576, DOI 10.17487/RFC5576, June 2009,
<https://www.rfc-editor.org/info/rfc5576>.
[RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding
Dependency in the Session Description Protocol (SDP)",
RFC 5583, DOI 10.17487/RFC5583, July 2009,
<https://www.rfc-editor.org/info/rfc5583>.
[RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
Protocol (RTCP) Extensions for Single-Source Multicast
Sessions with Unicast Feedback", RFC 5760,
DOI 10.17487/RFC5760, February 2010,
<https://www.rfc-editor.org/info/rfc5760>.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761,
DOI 10.17487/RFC5761, April 2010,
<https://www.rfc-editor.org/info/rfc5761>.
[RFC5762] Perkins, C., "RTP and the Datagram Congestion Control
Protocol (DCCP)", RFC 5762, DOI 10.17487/RFC5762, April
2010, <https://www.rfc-editor.org/info/rfc5762>.
[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, DOI 10.17487/RFC5763, May
2010, <https://www.rfc-editor.org/info/rfc5763>.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888,
DOI 10.17487/RFC5888, June 2010,
<https://www.rfc-editor.org/info/rfc5888>.
[RFC5939] Andreasen, F., "Session Description Protocol (SDP)
Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939,
September 2010, <https://www.rfc-editor.org/info/rfc5939>.
[RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in
the Session Description Protocol", RFC 5956,
DOI 10.17487/RFC5956, September 2010,
<https://www.rfc-editor.org/info/rfc5956>.
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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,
DOI 10.17487/RFC6064, January 2011,
<https://www.rfc-editor.org/info/rfc6064>.
[RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source-
Specific Multicast (SSM) Sessions", RFC 6128,
DOI 10.17487/RFC6128, February 2011,
<https://www.rfc-editor.org/info/rfc6128>.
[RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP:
Media Path Key Agreement for Unicast Secure RTP",
RFC 6189, DOI 10.17487/RFC6189, April 2011,
<https://www.rfc-editor.org/info/rfc6189>.
[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,
DOI 10.17487/RFC6193, April 2011,
<https://www.rfc-editor.org/info/rfc6193>.
[RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media
Control Channel Framework", RFC 6230,
DOI 10.17487/RFC6230, May 2011,
<https://www.rfc-editor.org/info/rfc6230>.
[RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image
Attributes in the Session Description Protocol (SDP)",
RFC 6236, DOI 10.17487/RFC6236, May 2011,
<https://www.rfc-editor.org/info/rfc6236>.
[RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping
between Unicast and Multicast RTP Sessions", RFC 6284,
DOI 10.17487/RFC6284, June 2011,
<https://www.rfc-editor.org/info/rfc6284>.
[RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
"Unicast-Based Rapid Acquisition of Multicast RTP
Sessions", RFC 6285, DOI 10.17487/RFC6285, June 2011,
<https://www.rfc-editor.org/info/rfc6285>.
[RFC6364] Begen, A., "Session Description Protocol Elements for the
Forward Error Correction (FEC) Framework", RFC 6364,
DOI 10.17487/RFC6364, October 2011,
<https://www.rfc-editor.org/info/rfc6364>.
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[RFC6642] Wu, Q., Ed., Xia, F., and R. Even, "RTP Control Protocol
(RTCP) Extension for a Third-Party Loss Report", RFC 6642,
DOI 10.17487/RFC6642, June 2012,
<https://www.rfc-editor.org/info/rfc6642>.
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
and K. Carlberg, "Explicit Congestion Notification (ECN)
for RTP over UDP", RFC 6679, DOI 10.17487/RFC6679, August
2012, <https://www.rfc-editor.org/info/rfc6679>.
[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
Establishment for Media Anchoring (CEMA) for the Message
Session Relay Protocol (MSRP)", RFC 6714,
DOI 10.17487/RFC6714, August 2012,
<https://www.rfc-editor.org/info/rfc6714>.
[RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
Datagram Congestion Control Protocol UDP Encapsulation for
NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November
2012, <https://www.rfc-editor.org/info/rfc6773>.
[RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control
Protocol Version 2 (MRCPv2)", RFC 6787,
DOI 10.17487/RFC6787, November 2012,
<https://www.rfc-editor.org/info/rfc6787>.
[RFC6849] Kaplan, H., Ed., Hedayat, K., Venna, N., Jones, P., and N.
Stratton, "An Extension to the Session Description
Protocol (SDP) and Real-time Transport Protocol (RTP) for
Media Loopback", RFC 6849, DOI 10.17487/RFC6849, February
2013, <https://www.rfc-editor.org/info/rfc6849>.
[RFC6871] Gilman, R., Even, R., and F. Andreasen, "Session
Description Protocol (SDP) Media Capabilities
Negotiation", RFC 6871, DOI 10.17487/RFC6871, February
2013, <https://www.rfc-editor.org/info/rfc6871>.
[RFC6947] Boucadair, M., Kaplan, H., Gilman, R., and S.
Veikkolainen, "The Session Description Protocol (SDP)
Alternate Connectivity (ALTC) Attribute", RFC 6947,
DOI 10.17487/RFC6947, May 2013,
<https://www.rfc-editor.org/info/rfc6947>.
[RFC7006] Garcia-Martin, M., Veikkolainen, S., and R. Gilman,
"Miscellaneous Capabilities Negotiation in the Session
Description Protocol (SDP)", RFC 7006,
DOI 10.17487/RFC7006, September 2013,
<https://www.rfc-editor.org/info/rfc7006>.
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[RFC7104] Begen, A., Cai, Y., and H. Ou, "Duplication Grouping
Semantics in the Session Description Protocol", RFC 7104,
DOI 10.17487/RFC7104, January 2014,
<https://www.rfc-editor.org/info/rfc7104>.
[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,
DOI 10.17487/RFC7195, May 2014,
<https://www.rfc-editor.org/info/rfc7195>.
[RFC7197] Begen, A., Cai, Y., and H. Ou, "Duplication Delay
Attribute in the Session Description Protocol", RFC 7197,
DOI 10.17487/RFC7197, April 2014,
<https://www.rfc-editor.org/info/rfc7197>.
[RFC7266] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control
Protocol (RTCP) Extended Report (XR) Blocks for Mean
Opinion Score (MOS) Metric Reporting", RFC 7266,
DOI 10.17487/RFC7266, June 2014,
<https://www.rfc-editor.org/info/rfc7266>.
[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, DOI 10.17487/RFC7272,
June 2014, <https://www.rfc-editor.org/info/rfc7272>.
[RFC7273] Williams, A., Gross, K., van Brandenburg, R., and H.
Stokking, "RTP Clock Source Signalling", RFC 7273,
DOI 10.17487/RFC7273, June 2014,
<https://www.rfc-editor.org/info/rfc7273>.
[RFC7657] Black, D., Ed. and P. Jones, "Differentiated Services
(Diffserv) and Real-Time Communication", RFC 7657,
DOI 10.17487/RFC7657, November 2015,
<https://www.rfc-editor.org/info/rfc7657>.
[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
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Suhas Nandakumar
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: snandaku@cisco.com
Nandakumar Expires February 28, 2021 [Page 97]
