Internet DRAFT - draft-nandakumar-mmusic-sdp-mux-attributes
draft-nandakumar-mmusic-sdp-mux-attributes
Network Working Group S. Nandakumar
Internet-Draft Cisco
Intended status: Standards Track October 18, 2013
Expires: April 21, 2014
A Framework for SDP Attributes when Multiplexing
draft-nandakumar-mmusic-sdp-mux-attributes-05
Abstract
The Session Description Protocol (SDP) provides mechanisms to
describe attributes of multimedia sessions and of individual media
streams (e.g., Real-time Transport Protocol (RTP) sessions) within a
multimedia session. In the RTCWeb WG, there is a need to use a
single 5-tuple for sending and receiving media associated with
multiple media descriptions ("m=" lines). Such a requirement has
raised concerns over the semantic implications of the SDP attributes
associated with the RTP Sessions multiplexed over a single transport
layer flow.
The scope of this specification is to provide a framework for
analyzing the multiplexing characteristics of SDP attributes. The
specification also categorizes existing attributes based on the
framework described herein.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on April 21, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. SDP Attribute Analysis Framework . . . . . . . . . . . . . . . 6
5. Analysis of Existing Attributes . . . . . . . . . . . . . . . 9
5.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 10
5.2. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . . 11
5.3. RFC5761 - Multiplexing RTP and RTCP . . . . . . . . . . . 12
5.4. RFC4574 - SDP Label Attribute . . . . . . . . . . . . . . 13
5.5. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . . 13
5.6. RFC4568 - SDP Security Descriptions . . . . . . . . . . . 14
5.7. RFC5762 - RTP over DCCP . . . . . . . . . . . . . . . . . 14
5.8. RFC6773 - DCCP-UDP Encapsulation . . . . . . . . . . . . . 15
5.9. RFC5506 - Reduced-Size RTCP in RTP Profile . . . . . . . . 16
5.10. RFC6787 - Media Resource Control Protocol Version 2 . . . 16
5.11. RFC5245 - Interactive Connectivity Establishment (ICE) . . 17
5.12. RFC5285 - RTP Header Extensions . . . . . . . . . . . . . 17
5.13. RFC3605 - RTCP attribute in SDP . . . . . . . . . . . . . 18
5.14. RFC5576 - Source-Specific SDP Attributes . . . . . . . . . 18
5.15. RFC6236 - Image Attributes in SDP . . . . . . . . . . . . 19
5.16. RFC6285 - Rapid Acquisition of Multicast RTP Sessions . . 20
5.17. RFC6230 - Media Control Channel Framework . . . . . . . . 20
5.18. RFC6364 - SDP Elements for FEC Framework . . . . . . . . . 21
5.19. RFC4796 - Content Attribute . . . . . . . . . . . . . . . 21
5.20. RFC3407 - SDP Simple Capability Declaration . . . . . . . 22
5.21. RFC6284 - Port Mapping between Unicast and Multicast
RTP Sessions . . . . . . . . . . . . . . . . . . . . . . . 22
5.22. RFC6714 - MSRP-CEMA . . . . . . . . . . . . . . . . . . . 23
5.23. RFC4583 - SDP Format for BFCP Streams . . . . . . . . . . 23
5.24. RFC5547 - SDP Offer/Answer for File Transfer . . . . . . . 24
5.25. draft-ietf-mmusic-media-loopback . . . . . . . . . . . . . 24
5.26. RFC5760 - RTCP with Unicast Feedback . . . . . . . . . . . 25
5.27. RFC3611 - RTCP XR . . . . . . . . . . . . . . . . . . . . 25
5.28. RFC5939 - SDP Capability Negotiation . . . . . . . . . . . 25
5.29. draft-ietf-mmusic-sdp-media-capabilities . . . . . . . . . 26
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5.30. RFC4567 - Key Management Extensions for SDP and RTSP . . . 27
5.31. RFC4572 - Comedia over TLS in SDP . . . . . . . . . . . . 27
5.32. RFC4570 - SDP Source Filters . . . . . . . . . . . . . . . 28
5.33. RFC6128 - RTCP Port for Multicast Sessions . . . . . . . . 28
5.34. RFC6189 - ZRTP . . . . . . . . . . . . . . . . . . . . . . 29
5.35. RFC4145 - Connection-Oriented Media . . . . . . . . . . . 30
5.36. RFC5159 - OMA BCAST SDP Attributes . . . . . . . . . . . . 30
5.37. RFC6193 - Media Description for IKE in SDP . . . . . . . . 31
5.38. RFC6064 - SDP and RTSP Extensions for 3GPP . . . . . . . . 32
5.39. RFC3108 - ATM SDP . . . . . . . . . . . . . . . . . . . . 34
5.40. 3GPP TS 24.182 . . . . . . . . . . . . . . . . . . . . . . 35
5.41. 3GPP TS 24.183 . . . . . . . . . . . . . . . . . . . . . . 36
5.42. 3GPP TS 24.229 . . . . . . . . . . . . . . . . . . . . . . 36
5.43. ITU T.38 . . . . . . . . . . . . . . . . . . . . . . . . . 37
5.44. ITU-T H.248.15 . . . . . . . . . . . . . . . . . . . . . . 37
5.45. RFC4975 - The Message Session Relay Protocol . . . . . . . 38
5.46. Historical . . . . . . . . . . . . . . . . . . . . . . . . 39
6. bwtype Attribute Analysis . . . . . . . . . . . . . . . . . . 39
6.1. RFC4566 - SDP: Session Description Protocol . . . . . . . 39
6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth . . . 40
6.3. RFC3890 - Bandwidth Modifier for SDP . . . . . . . . . . . 41
7. rtcp-fb Attribute Analysis . . . . . . . . . . . . . . . . . . 41
7.1. RFC4585 - RTP/AVPF . . . . . . . . . . . . . . . . . . . . 41
7.2. RFC5104 - Codec Control Messages in AVPF . . . . . . . . . 42
7.3. RFC6285 - Unicast-Based RAMS . . . . . . . . . . . . . . . 43
7.4. RFC6679 - ECN for RTP over UDP/IP . . . . . . . . . . . . 43
7.5. RFC6642 - Third-Party Loss Report . . . . . . . . . . . . 43
7.6. RFC5104 - Codec Control Messages in AVPF . . . . . . . . . 44
8. group Attribute Analysis . . . . . . . . . . . . . . . . . . . 44
8.1. RFC5888 - SDP Grouping Framework . . . . . . . . . . . . . 44
8.2. RFC3524 - Mapping Media Streams to Resource
Reservation Flows . . . . . . . . . . . . . . . . . . . . 45
8.3. RFC4091 - ANAT Semantics . . . . . . . . . . . . . . . . . 45
8.4. RFC5956 - FEC Grouping Semantics in SDP . . . . . . . . . 46
8.5. RFC5583 - Signaling Media Decoding Dependency in SDP . . . 46
9. ssrc-group Attribute Analysis . . . . . . . . . . . . . . . . 47
9.1. RFC5576 - Source-Specific SDP Attributes . . . . . . . . . 47
10. QoS Mechanism Token Analysis . . . . . . . . . . . . . . . . . 47
10.1. RFC5432 - QoS Mechanism Selection in SDP . . . . . . . . . 47
11. k= Attribute Analysis . . . . . . . . . . . . . . . . . . . . 47
11.1. RFC4566 SDP: Session Description Protocol . . . . . . . . 48
12. content Atribute Analysis . . . . . . . . . . . . . . . . . . 48
12.1. RFC4796 - MSRP Relays . . . . . . . . . . . . . . . . . . 48
13. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 48
13.1. RFC5109 - RTP Payload Format for Generic FEC . . . . . . . 48
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49
15. Security Considerations . . . . . . . . . . . . . . . . . . . 50
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 50
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17. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 50
18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51
18.1. Normative References . . . . . . . . . . . . . . . . . . . 51
18.2. Informative References . . . . . . . . . . . . . . . . . . 51
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 57
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1. Introduction
Real-Time Communication Web (RTCWeb) framework requires Real-time
Transport Protocol as the media transport protocol and Session
Description Protocol (SDP) [RFC4566] for describing and negotiating
multi-media communication sessions.
SDP defines several attributes for capturing characteristics that
apply to the individual media descriptions (described by "m=" lines")
and the overall multimedia session. Typically different media types
(audio, video etc) described using different media descriptions
represent separate RTP Sessions that are carried over individual
transport layer flows. However, in the RTCWeb WG, a requirement has
arisen to multiplex several RTP Sessions over a single transport
layer flow. This in turn has made necessary to understand the
interpretation and usage of the SDP attributes defined for the
multiplexed media descriptions.
Given the number of SDP attributes registered with the IANA [IANA]
and possibility of new attributes being defined in the future, there
is need for generic future-proof framework to analyze these
attributes for their applicability in the transport multiplexing use-
cases.
The document starts with providing the motivation for requiring such
a framework. This is followed by introduction to the SDP attribute
analysis framework/procedures, following which several sections
applies the framework to the SDP attributes registered with the IANA
[IANA]
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",
"RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
interpreted as described in [RFC2119].
3. Motivation
The time and complications of setting up ICE [RFC5245] and DTLS-SRTP
[RFC5763] transports for use by RTP, and conservation of ports, forms
an requirement to try and reduce the number of transport level flows
needed. This has resulted in the definition of ways, such as,
[I-D.ietf-mmusic-sdp-bundle-negotiation] and
[I-D.ietf-avt-multiplexing-rtp] to multiplex RTP over a single
transport flow in order to preserve network resources such as port
numbers. This imposes further restrictions on applicability of these
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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-mline to have an independently specified ice-ufrag attribute.
However, if the media from multiple m-lines is multiplexed over the
same ICE component, then the meaning of media-level ice-ufrag
attributes becomes muddled.
As of today there are close to 250 SDP attributes registered with the
IANA [IANA] and more will be added in the future. There is no
clearly defined procedure to establish the validity/applicability of
these attribute when used with transport multiplexing.
4. SDP Attribute Analysis Framework
Attributes in an SDP session description can be defined at the
session-level and media-level. These attributes could be
semantically grouped as noted below.
o Attributes related to media content such as media type, encoding
schemes, payload types.
o Attributes specifying media transport characteristics like RTP/
RTCP port numbers, network addresses, QOS.
o Metadata description attributes capturing session timing and
origin information.
o Attributes establishing relationships between media streams such
as grouping framework
With the above semantic grouping as the reference, the proposed
framework classifies each attribute into one of the following
categories:
NORMAL Attributes that can be independently specified when
multiplexing and retain their original semantics.
In the example given below, the direction and label attributes are
independently specified for audio and video m=lines. These
attributes are not impacted by multiplexing these media streams
over a single transport layer flow.
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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=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
NOT RECOMMENDED Attributes where multiplexing is not recommended if
these attributes are in use in the SDP since doing so MAY result
in incorrect behaviors
Example: Multiplexing media descriptions having attribute zrtp-
hash defined with the media descriptions lacking it, would either
complicate the handling of multiplexed stream or fail
multiplexing.
v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 3456 RTP/AVP 97 // with zrtp
a=rtpmap:97 iLBC/8000
<allOneLine>
a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
df881ae642c371ba46df
</allOneLine>
m=video 34567 RTP/AVP 31 //without zrtp
a=rtpmap:31 H261/90000
IDENTICAL Attributes that MUST be identical across all the media
descriptions being multiplexed.
Attributes such as rtcp-mux fall into this category. Since RTCP
reporting is done per RTP Session, there is no way to receive RTCP
control data for the video m=line in the example below. Hence
rtcp-mux MUST be repeated for the video m=line as well, when
multiplexed.
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v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 34567 RTP/AVP 97
a=rtcp-mux
m=video 34567 RTP/AVP 31
a=rtpmap:31 H261/90000
a=rtcp-mux
SUM Attributes can be set as they are normally used but software
using them in a multiplex case, MUST apply the sum of all the
attributes being multiplexed instead of trying to use each one.
This is typically used for bandwidth or other rate limiting
attributes to the underlining transport.
The software parsing the SDP sample below, should use the
aggregate Application Specific (AS) bandwidth value from the
individual media descriptions to determine the AS value for the
multiplexed session. Thus the calculated AS value would be 256+64
bytes for the given example.
v=0
o=mhandley 2890844526 2890842807 IN IP4 126.16.64.4
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 49170 RTP/AVP 0
b=AS:64
m=video 51372 RTP/AVP 31
b=AS:256
TRANSPORT Attributes that can be set normally for multiple items in
a multiplexed group but the software MUST pick just one of the
attribute of the given type for use. The one chosen is the
attribute associated with the "m=" line that represents the
information being used for the transport of the RTP.
In the example below, "a=crypto" attribute is defined for both the
audio and the video m=lines. The video media line's a=crypto
attribute is chosen since its mid value (bar) appears first in the
a=group:BUNDLE line. This is due to BUNDLE grouping semantic
[I-D.ietf-mmusic-sdp-bundle-negotiation] which mandates the values
from m=line corresponding to the mid appearing first on the
a=group:BUNDLE line to be considered for setting up the RTP
Transport.
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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
SPECIAL Attributes where the text in the source draft must be
consulted for further handling when multiplexed.
As an example, for the attribute extmap, the specification
defining the extension MUST be referred to understand the
multiplexing implications.
TBD This category defines attributes that need more information to
assign an appropriate category.
The idea behind these categories is to provide recommendations for
using the attributes under RTP session multiplexing scenarios.
Section 5 analyzes attributes listed in IANA [IANA] grouped under the
IETF document that defines them. The "Level" column indicates
whether the attribute is currently specified as:
o S -- Session level
o M -- Media level
o B -- Both
o SR -- Source-level (for a single SSRC)
5. Analysis of Existing Attributes
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5.1. RFC4566 - SDP: Session Description Protocol
RFC4566 [RFC4566] defines the Session Description Protocol (SDP) that
is intended for describing multimedia sessions for the purposes of
session announcement, session invitation, and other forms of
multimedia session initiation
+------------+----------------+-------+----------+
| Attr Name | Notes | Level | Category |
+------------+----------------+-------+----------+
| sendrecv | Not impacted | B | NORMAL |
| | | | |
| sendonly | Not impacted | B | NORMAL |
| | | | |
| recvonly | Not impacted | B | NORMAL |
| | | | |
| inactive | Not impacted | B | NORMAL |
| | | | |
| cat | Not impacted | S | NORMAL |
| | | | |
| ptime | Not Impacted | M | NORMAL |
| | | | |
| maxptime | Not Impacted | M | NORMAL |
| | | | |
| orient | Not Impacted | M | NORMAL |
| | | | |
| framerate | Not Impacted | M | NORMAL |
| | | | |
| quality | Not Impacted | M | NORMAL |
| | | | |
| rtpmap | Not Impacted | M | NORMAL |
| | | | |
| fmtp | Not Impacted | M | NORMAL |
| | | | |
| keywds | Not impacted | S | NORMAL |
| | | | |
| type | Not Impacted | S | NORMAL |
| | | | |
| tool | Not Impacted | S | NORMAL |
| | | | |
| charset | Not Impacted | S | NORMAL |
| | | | |
| sdplang | Not Impacted | B | NORMAL |
| | | | |
| lang | Not Impacted | B | NORMAL |
| | | | |
+------------+----------------+-------+----------+
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RFC4566 Attribute Analysis
5.2. RFC4585 - RTP/AVPF
RFC4585 [RFC4585] defines an extension to the Audio-visual Profile
(AVP) that enables receivers to provide, statistically, more
immediate feedback to the senders and thus allows for short-term
adaptation and efficient feedback-based repair mechanisms to be
implemented.
+----------+-----------------------------------+-------+------------+
| Attr | Notes | Level | Category |
| Name | | | |
+----------+-----------------------------------+-------+------------+
| rtcp-fb | RTCP reporting happens per RTP | M | IDENTICAL |
| | Session. | | |
| | | | |
+----------+-----------------------------------+-------+------------+
RFC4585 Attribute Analysis
OPEN ISSUE:Below SDP examples show 3 scenarios on implications of
allowing Payload Types to be repated or not repeated within the
BUNDLEd m= lines.
Scenario1: Payload Types are not shared and rtcp-fb is mandated for
all the multiplexed m=lines. This scenario leads into assigning
category "NOT IMPACTED" for rtcp-fb and its paramters since RTCP
reporting happens per PayloadType with in a BUNDLED RTP Session, thus
allowing for unique reporting.
a=group:BUNDLE audio video
m=audio 3456 RTP/AVP 97
a=mid:audio
a=rtpmap:97 iLBC/8000
m=video 3456 RTP/AVP 98
a=mid:video
a=rtpmap:98 VP8/90000
a-rtcp-fb:98 nack rpsi
Scenario2: Payload Types are shared and rtcp-fb is repeated across
all the multiplexed m= lines with same feedback type (nack). This
leads to assigning category "IDENTICAL" to rtcp-fb which allows NACK
and NACK RPSI reporting to be done for PT 98 in this example.
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a=group:BUNDLE audio video
m=audio 3456 RTP/AVP 98
a=mid:audio
a=rtpmap:98 iLBC/8000
a=rtcp-fb:98 nack
m=video 3456 RTP/AVP 98
a=mid:video
a=rtpmap:98 VP8/90000
a-rtcp-fb:98 nack rpsi
In the below case, audio media line has rtcp-fb ack and video video
media line has rtcp-fb nack with Payload types shared. With such a
configuration, positive acks are reported for video stream even it
was not intended and negative acks are reported for audio stream
unintended.
// PTs are shared and have different feedback types
a=group:BUNDLE audio video
m=audio 3456 RTP/AVP 98
a=mid:audio
a=rtpmap:98 iLBC/8000
a=rtcp-fb ack // Positive ACK
m=video 3456 RTP/AVP 98
a=mid:video
a=rtpmap:98 VP8/90000
a-rtcp-fb:98 nack rpsi // Nack ACK
OPEN ISSUE: Should BUNDLE disallow PT to be repeated ?? What does
it mean if PTs are shared in the context of rtcp-fb ??. Magnus
pointed out that RTCP FB reporting MUST happen per (PT+Media
Source) when BUNDLED. If this is allowed, the category of
"IDENTICAL" applies with rtcp-fb for all m= lines and update
BUNDLE spec to mandate the behavior. Does this sound fine ?
5.3. RFC5761 - Multiplexing RTP and RTCP
RFC5761 [RFC5761] discusses issues that arise when multiplexing RTP
data packets and RTP Control Protocol (RTCP) packets on a single UDP
port. It describes when such multiplexing is and is not appropriate,
and it explains how the Session Description Protocol (SDP) can be
used to signal multiplexed sessions.
+-----------+----------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-----------+----------------------------------+-------+------------+
| rtcp-mux | RTCP muxing should be repeated | M | IDENTICAL |
| | across all the m=lines | | |
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| | | | |
+-----------+----------------------------------+-------+------------+
RFC5761 Attribute Analysis
5.4. RFC4574 - SDP Label Attribute
RFC4574 [RFC4574] defines a new Session Description Protocol (SDP)
media-level attribute: "label". The "label" attribute carries a
pointer to a media stream in the context of an arbitrary network
application that uses SDP. The sender of the SDP document can attach
the "label" attribute to a particular media stream or streams. The
application can then use the provided pointer to refer to each
particular media stream in its context.
+--------+---------------+-------+----------+
| Name | Notes | Level | Category |
+--------+---------------+-------+----------+
| label | Not Impacted | M | NORMAL |
| | | | |
+--------+---------------+-------+----------+
RFC4574 Attribute Analysis
5.5. RFC5432 - QoS Mechanism Selection in SDP
RFC5432 [RFC5432] defines prordures to negotiate QOS mechanisms using
the Session Description Protocol (SDP) offer/answer model.
+----------------+-------------------------------+-------+----------+
| Name | Notes | Level | Category |
+----------------+-------------------------------+-------+----------+
| qos-mech-send | Since QOS mechanism are | B | NORMAL |
| | signaled per flow, | | |
| | multiplexing multiple m=lines | | |
| | has no impact on per m=line | | |
| | QOS mechanism. | | |
| | | | |
| qos-mech-recv | Since QOS mechanism are | B | NORMAL |
| | signaled per flow, | | |
| | multiplexing multiple m=lines | | |
| | has no impact on per m=line | | |
| | QOS mechanism. | | |
| | | | |
+----------------+-------------------------------+-------+----------+
RFC5432 Attribute Analysis
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5.6. RFC4568 - SDP Security Descriptions
RFC4568 [RFC4568] defines a Session Description Protocol (SDP)
cryptographic attribute for unicast media streams. The attribute
describes a cryptographic key and other parameters that serve to
configure security for a unicast media stream in either a single
message or a roundtrip exchange.
+---------+----------------------------------+-------+--------------+
| Name | Notes | Level | Category |
+---------+----------------------------------+-------+--------------+
| crypto | The multiplexing scheme MUST | M | TRANSPORT |
| | ensure unique SSRCs across all | | |
| | the media lines multiplexed. In | | |
| | that case, cryptographic keys | | |
| | corresponding to the underlying | | |
| | transport is used. | | |
| | | | |
| crypto | If the multiplexing scheme | M | NOT |
| | cannot ensure unique SSRCs | | RECOMMENDED |
| | across all the media lines, | | |
| | multiplexing MUST NOT be | | |
| | performed. | | |
| | | | |
+---------+----------------------------------+-------+--------------+
RFC4568 Attribute Analysis
5.7. RFC5762 - RTP over DCCP
The Real-time Transport Protocol (RTP) is a widely used transport for
real-time multimedia on IP networks. The Datagram Congestion Control
Protocol (DCCP) is a transport protocol that provides desirable
services for real-time applications. RFC5762 [RFC5762] specifies a
mapping of RTP onto DCCP, along with associated signalling, such that
real-time applications can make use of the services provided by DCCP
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+--------------------+---------------------+---------+--------------+
| Name | Notes | Current | Category |
+--------------------+---------------------+---------+--------------+
| dccp-service-code | If RFC 6773 is not | M | NOT |
| | being used in | | RECOMMENDED |
| | addition to RFC | | |
| | 5762, the port in | | |
| | the m= line is a | | |
| | DCCP port. DCCP | | |
| | being a connection | | |
| | oriented protocol, | | |
| | does not allow | | |
| | multiple | | |
| | connections on the | | |
| | same 5-tuple. | | |
| | | | |
+--------------------+---------------------+---------+--------------+
RFC5762 Attribute Analysis
If RFC 6773 is being used in addition to RFC 5762 and provided that
DCCP-in-UDP layer has additional demultiplexing, then it may be
possible to use different DCCP service codes for each DCCP flow,
given each uses a different DCCP port. Although doing so might
conflict with the media type of the m= line. None of this is
standardised yet and it wouldn't work as explained. Hence
multiplexing MUST NOT be performed even in this alternate scenario.
5.8. RFC6773 - DCCP-UDP Encapsulation
RFC6773 [RFC6773] document specifies an alternative encapsulation of
the Datagram Congestion Control Protocol (DCCP), referred to as DCCP-
UDP. This encapsulation allows DCCP to be carried through the
current generation of Network Address Translation (NAT) middleboxes
without modification of those middleboxes
+------------+-------------------------------+-------+--------------+
| Name | Notes | Level | Category |
+------------+-------------------------------+-------+--------------+
| dccp-port | Multiplexing MUST NOT be | M | NOT |
| | performed due to potential | | RECOMMENDED |
| | conflict between the port | | |
| | used for DCCP | | |
| | en/decapsulation and the | | |
| | RTP. | | |
| | | | |
+------------+-------------------------------+-------+--------------+
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RFC6773 Attribute Analysis
5.9. RFC5506 - Reduced-Size RTCP in RTP Profile
RFC5506 [RFC5506] discusses benefits and issues that arise when
allowing Real-time Transport Protocol (RTCP) packets to be
transmitted with reduced size.
+-------------+--------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------------+--------------------------------+-------+------------+
| rtcp-rsize | RTCP reduced size MUST be | M | IDENTICAL |
| | repeated across all the | | |
| | m=lines | | |
| | | | |
+-------------+--------------------------------+-------+------------+
RFC5506 Attribute Analysis
5.10. RFC6787 - Media Resource Control Protocol Version 2
The Media Resource Control Protocol Version 2 (MRCPv2) allows client
hosts to control media service resources such as speech synthesizers,
recognizers, verifiers, and identifiers residing in servers on the
network. MRCPv2 is not a "stand-alone" protocol -- it relies on
other protocols, such as the Session Initiation Protocol (SIP), to
coordinate MRCPv2 clients and servers and manage sessions between
them, and the Session Description Protocol (SDP) to describe,
discover, and exchange capabilities. It also depends on SIP and SDP
to establish the media sessions and associated parameters between the
media source or sink and the media server. Once this is done, the
MRCPv2 exchange operates over the control session established above,
allowing the client to control the media processing resources on the
speech resource server. RFC6787 [RFC6787] defines attributes for
this purpose.
+-----------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-----------+---------------+-------+----------+
| resource | Not Impacted | M | NORMAL |
| | | | |
| channel | Not Impacted | M | NORMAL |
| | | | |
| | Not Impacted | M | NORMAL |
| | | | |
+-----------+---------------+-------+----------+
RFC6787 Attribute Analysis
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5.11. RFC5245 - Interactive Connectivity Establishment (ICE)
RFC5245 [RFC5245] describes a protocol for Network Address
Translator(NAT) traversal for UDP-based multimedia sessions
established with the offer/answer model. This protocol is called
Interactive Connectivity Establishment (ICE). ICE makes use of the
Session Traversal Utilities for NAT (STUN) protocol and its
extension,Traversal Using Relay NAT (TURN). ICE can be used by any
protocol utilizing the offer/answer model, such as the Session
Initiation Protocol (SIP).
+--------------------+-------------------------+-------+------------+
| Name | Notes | Level | Category |
+--------------------+-------------------------+-------+------------+
| ice-lite | Not Impacted | S | NORMAL |
| | | | |
| ice-options | Not Impacted | S | NORMAL |
| | | | |
| ice-pwd | Per media-level | B | TRANSPORT |
| | attribute MUST be used | | |
| | per underlying | | |
| | transport flow | | |
| | | | |
| ice-ufrag | Per media-level | B | TRANSPORT |
| | attribute MUST be used | | |
| | per underlying | | |
| | transport flow | | |
| | | | |
| candidate | Per media-level | M | TRANSPORT |
| | attribute MUST be used | | |
| | per underlying | | |
| | transport flow | | |
| | | | |
| remote-candidates | Per media-level | M | TRANSPORT |
| | attribute MUST be used | | |
| | per underlying | | |
| | transport flow | | |
| | | | |
+--------------------+-------------------------+-------+------------+
RFC5245 Attribute Analysis
5.12. RFC5285 - RTP Header Extensions
RFC5285 [RFC5285] provides a general mechanism to use the header
extension feature of RTP (the Real-Time Transport Protocol). It
provides the option to use a small number of small extensions in each
RTP packet, where the universe of possible extensions is large and
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registration is de-centralized. The actual extensions in use in a
session are signaled in the setup information for that session.
+---------+--------------------------------------+-------+----------+
| Name | Notes | Level | Category |
+---------+--------------------------------------+-------+----------+
| extmap | Specific RTP extension document MUST | B | SPECIAL |
| | be referred | | |
| | | | |
+---------+--------------------------------------+-------+----------+
RFC5285 Attribute Analysis
5.13. RFC3605 - RTCP attribute in SDP
Originally, SDP assumed that RTP and RTCP were carried on consecutive
ports. However, this is not always true when NATs are involved.
[RFC3605] specifies an early mechanism to indicate the RTCP port.
+-------+--------------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------+--------------------------------------+-------+------------+
| rtcp | Case1:Same RTCP port is repeated | M | TRANSPORT |
| | across the m=lines. Case2:Different | | |
| | RTCP ports renders multiplexing | | |
| | impossible | | |
| | | | |
+-------+--------------------------------------+-------+------------+
RFC3605 Attribute Analysis
5.14. RFC5576 - Source-Specific SDP Attributes
RFC5576 [RFC5576] defines a mechanism to describe RTP media sources,
which are identified by their synchronization source (SSRC)
identifiers, in SDP, to associate attributes with these sources, and
to express relationships among sources. It also defines several
source-level attributes that can be used to describe properties of
media sources.
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+----------------+---------------------------+-------+--------------+
| Name | Notes | Level | Category |
+----------------+---------------------------+-------+--------------+
| ssrc | SSRCs repeated over | M | NOT |
| | multiple m=lines is | | RECOMMENDED |
| | forbidden if the m-lines | | |
| | are in the same RTP | | |
| | session. | | |
| | | | |
| ssrc-group | Refer to section | M | SPECIAL |
| | Section 9 for specific | | |
| | analysis of the grouping | | |
| | semantics | | |
| | | | |
| cname | Not Impacted [Open | SR | NORMAL |
| | Issues: what are the | | |
| | rules for CNAME | | |
| | duplication across | | |
| | sessions?] | | |
| | | | |
| previous-ssrc | SSRCs repeated over | SR | NOT |
| | multiple m=lines | | RECOMMENDED |
| | complicates multiplexing | | |
| | | | |
| fmtp | Not Impacted | SR | NORMAL |
| | | | |
+----------------+---------------------------+-------+--------------+
RFC5576 Attribute Analysis
OPEN ISSUE:LNX: There has been concern on how to deal with SSRC
values repeated across the multiplexed m= lines. Lennox suggested
to possible options to deal with it. The simpler is to say that
individual SSRC values in a=ssrc attributes MUST NOT be repeated
across bundled m-lines, but other than that the behavior is
normal. The more complicated is to say that SSRC attributes MAY
be repeated across bundled m-lines, iff the media stream satisfies
more than one m-line. In this case, it's up to the individual
source attributes to define what's allowed.
Should BUNDLE allow SSRCs to be repeated ? If so, should the
category for the source attributes be SPECIAL and update RFC5576
to add text to define multiplexing scenarios.
5.15. RFC6236 - Image Attributes in SDP
RFC6236 [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
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hand-held terminal to display video without the need to rescale the
image,something that may consume large amounts of memory and
processing power. The document also helps to maintain an optimal
bitrate for video as only the image size that is desired by the
receiver is transmitted.
+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| imageattr | Not Impacted | M | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC6236 Attribute Analysis
5.16. RFC6285 - Rapid Acquisition of Multicast RTP Sessions
RFC6285 [RFC6285] describes a method using the existing RTP and RTP
Control Protocol (RTCP) machinery that reduces the acquisition delay.
In this method, an auxiliary unicast RTP session carrying the
Reference Information to the receiver precedes or accompanies the
multicast stream. This unicast RTP flow can be transmitted at a
faster than natural bitrate to further accelerate the acquisition.
The motivating use case for this capability is multicast applications
that carry real-time compressed audio and video.
+---------------+-------------------+-------+------------------+
| Name | Notes | Level | Category |
+---------------+-------------------+-------+------------------+
| rams-updates | Not recommended | M | NOT RECOMMENDED |
| | | | |
+---------------+-------------------+-------+------------------+
RFC6285 Attribute Analysis
5.17. RFC6230 - Media Control Channel Framework
RFC6230 [RFC6230] describes a framework and protocol for application
deployment where the application programming logic and media
processing are distributed. This implies that application
programming logic can seamlessly gain access to appropriate resources
that are not co-located on the same physical network entity. The
framework uses the Session Initiation Protocol (SIP) to establish an
application-level control mechanism between application servers and
associated external servers such as media servers.
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+---------+-----------------+-------+----------+
| Name | Notes | Level | Category |
+---------+-----------------+-------+----------+
| cfw-id | Not Applicable | M | NORMAL |
| | | | |
+---------+-----------------+-------+----------+
RFC6230 Attribute Analysis
5.18. RFC6364 - SDP Elements for FEC Framework
RFC6364 [RFC6364] specifies the use of the Session Description
Protocol (SDP) to describe the parameters required to signal the
Forward Error Correction (FEC) Framework Configuration Information
between the sender(s) and receiver(s). This document also provides
examples that show the semantics for grouping multiple source and
repair flows together for the applications that simultaneously use
multiple instances of the FEC Framework.
+------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------------+---------------+-------+----------+
| fec-source-flow | Not Impacted | M | NORMAL |
| | | | |
| fec-repair-flow | Not Impacted | M | NORMAL |
| | | | |
| repair-window | Not Impacted | M | NORMAL |
| | | | |
+------------------+---------------+-------+----------+
RFC6364 Attribute Analysis
5.19. RFC4796 - Content Attribute
RFC4796 [RFC4796] defines a new Session Description Protocol (SDP)
media-level attribute, 'content'. The 'content' attribute defines
the content of the media stream to a more detailed level than the
media description line. The sender of an SDP session description can
attach the 'content' attribute to one or more media streams. The
receiving application can then treat each media stream differently
(e.g., show it on a big or small screen) based on its content.
+----------+---------------+-------+----------+
| Name | Notes | Level | Category |
+----------+---------------+-------+----------+
| content | Not Impacted | M | NORMAL |
| | | | |
+----------+---------------+-------+----------+
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RFC4796 Attribute Analysis
5.20. RFC3407 - SDP Simple Capability Declaration
RFC3407 [RFC3407] defines a set of Session Description Protocol (SDP)
attributes that enables SDP to provide a minimal and backwards
compatible capability declaration mechanism.
+----------+-------------------------------------+-------+----------+
| Name | Notes | Level | Category |
+----------+-------------------------------------+-------+----------+
| sqn | Not Impacted | B | NORMAL |
| | | | |
| csdc | Mismatch in the offered capability | B | TBD |
| | description MAY fail multiplexing. | | |
| | | | |
| cpar | Mismatch in the offered capability | B | TBD |
| | parameters MAY fail multiplexing. | | |
| | | | |
| cparmin | Mismatch in the offered capability | B | TBD |
| | parameters MAY fail multiplexing. | | |
| | | | |
| cparmax | Mismatch in the offered capability | B | TBD |
| | parameters MAY fail multiplexing. | | |
| | | | |
+----------+-------------------------------------+-------+----------+
RFC3407 Attribute Analysis
5.21. RFC6284 - Port Mapping between Unicast and Multicast RTP Sessions
RFC6284 [RFC6284] presents a port mapping solution that allows RTP
receivers to choose their own ports for an auxiliary unicast session
in RTP applications using both unicast and multicast services. The
solution provides protection against denial-of-service or packet
amplification attacks that could be used to cause one or more RTP
packets to be sent to a victim client
+------------------+-------------------------+-------+--------------+
| Name | Notes | Level | Category |
+------------------+-------------------------+-------+--------------+
| portmapping-req | Not recommended, if | M | NOT |
| | port mapping is | | RECOMMENDED |
| | required by the | | |
| | application | | |
| | | | |
+------------------+-------------------------+-------+--------------+
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RFC6284 Attribute Analysis
5.22. RFC6714 - MSRP-CEMA
RFC6714 [RFC6714] defines a Message Session Relay Protocol (MSRP)
extension, Connection Establishment for Media Anchoring (CEMA).
Support of this extension is OPTIONAL. The extension allows
middleboxes to anchor the MSRP connection, without the need for
middleboxes to modify the MSRP messages; thus, it also enables secure
end-to-end MSRP communication in networks where such middleboxes are
deployed. This document also defines a Session Description Protocol
(SDP) attribute, 'msrp-cema', that MSRP endpoints use to indicate
support of the CEMA extension.
+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| msrp-cema | Not Impacted | M | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC6714 Attribute Analysis
5.23. RFC4583 - SDP Format for BFCP Streams
RFC4583 [RFC4583] document specifies how to describe Binary Floor
Control Protocol (BFCP) streams in Session Description Protocol (SDP)
descriptions. User agents using the offer/answer model to establish
BFCP streams use this format in their offers and answers
+------------+-------------------------------+-------+--------------+
| Name | Notes | Level | Category |
+------------+-------------------------------+-------+--------------+
| floorctrl | Must be repeated across all | M | IDENTICAL |
| | the multiplexed m=lines | | |
| | | | |
| confid | Not Impacted | M | NORMAL |
| | | | |
| userid | Not Impacted | M | NORMAL |
| | | | |
| floorid | The floorid MUST be unique | M | NOT |
| | across the multiplexed | | RECOMMENDED |
| | m=lines | | |
| | | | |
+------------+-------------------------------+-------+--------------+
RFC4583 Attribute Analysis
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5.24. RFC5547 - SDP Offer/Answer for File Transfer
RFC5547 [RFC5547] provides a mechanism to negotiate the transfer of
one or more files between two endpoints by using the Session
Description Protocol (SDP) offer/answer model specified in [RFC3264].
+--------------------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+--------------------------------+---------------+-------+----------+
| file-selector | Not Impacted | M | NORMAL |
| | | | |
| file-transfer-id | Not Impacted | M | NORMAL |
| | | | |
| file-disposition | Not Impacted | M | NORMAL |
| | | | |
| file-date,file-iconfile-range | Not Impacted | M | NORMAL |
| | | | |
| file-iconfile-range | Not Impacted | M | NORMAL |
| | | | |
| file-iconfile-range | Not Impacted | M | NORMAL |
| | | | |
+--------------------------------+---------------+-------+----------+
RFC5547 Attribute Analysis
5.25. draft-ietf-mmusic-media-loopback
[MEDIA_LOOPBACK] adds new SDP media types and attributes, which
enable establishment of media sessions where the media is looped back
to the transmitter. Such media sessions will serve as monitoring and
troubleshooting tools by providing the means for measurement of more
advanced VoIP, Real-time Text and Video over IP performance metrics.
+------------------------------+----------------+-------+----------+
| Name | Notes | Level | Category |
+------------------------------+----------------+-------+----------+
| loopback rtp-pkt-loopback | Not Impacted | M | NORMAL |
| | | | |
| loopback rtp-media-loopback | Not Impacted | M | NORMAL |
| | | | |
| loopback-source | Not Impacted | M | NORMAL |
| | | | |
| loopback-mirror | Not Impacted | M | NORMAL |
| | | | |
+------------------------------+----------------+-------+----------+
draft-ietf-mmusic-media-loopback Attribute Analysis
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5.26. RFC5760 - RTCP with Unicast Feedback
RFC5760 [RFC5760] specifies an extension to the Real-time Transport
Control Protocol (RTCP) to use unicast feedback to a multicast
sender. The proposed extension is useful for single-source multicast
sessions such as Source-Specific Multicast (SSM) communication where
the traditional model of many-to-many group communication is either
not available or not desired.
+---------------+------------------------------+-------+------------+
| Name | Notes | Level | Category |
+---------------+------------------------------+-------+------------+
| rtcp-unicast | The attribute MUST be | M | IDENTICAL |
| | reported across all m=lines | | |
| | multiplexed | | |
| | | | |
+---------------+------------------------------+-------+------------+
RFC5760 Attribute Analysis
5.27. RFC3611 - RTCP XR
RFC3611 [RFC3611] defines the Extended Report (XR) packet type for
the RTP Control Protocol (RTCP), and defines how the use of XR
packets can be signaled by an application if it employs the Session
Description Protocol (SDP).
+----------+-----------------------------------+-------+------------+
| Name | Notes | Level | Category |
+----------+-----------------------------------+-------+------------+
| rtcp-xr | The attribute MUST be reported | B | IDENTICAL |
| | across all m=lines multiplexed | | |
| | | | |
+----------+-----------------------------------+-------+------------+
RFC3611 Attribute Analysis
5.28. RFC5939 - SDP Capability Negotiation
RFC5939 [RFC5939] defines a general SDP Capability Negotiation
framework. It also specifies how to provide attributes and transport
protocols as capabilities and negotiate them using the framework.
Extensions for other types of capabilities (e.g., media types and
media formats) may be provided in other documents.
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+-------+--------------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------+--------------------------------------+-------+------------+
| pcfg | Depends on capability being | M | SPECIAL |
| | negotiated | | |
| | | | |
| acfg | Depends on capability being | M | SPECIAL |
| | negotiated | | |
| | | | |
| csup | Depends on capability being | B | SPECIAL |
| | negotiated | | |
| | | | |
| creq | Depends on capability being | B | SPECIAL |
| | negotiateds | | |
| | | | |
| acap | Depends on capability being | B | SPECIAL |
| | negotiated | | |
| | | | |
| tcap | Repeat transport capability across | B | IDENTICAL |
| | all m= lines | | |
| | | | |
+-------+--------------------------------------+-------+------------+
RFC5939 Attribute Analysis
5.29. draft-ietf-mmusic-sdp-media-capabilities
Session Description Protocol (SDP) capability negotiation provides a
general framework for indicating and negotiating capabilities in SDP.
The base framework defines only capabilities for negotiating
transport protocols and attributes. [MEDIA_CAP] extends the
framework by defining media capabilities that can be used to
negotiate media types and their associated parameters.
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+--------+---------------+-------+----------+
| Name | Notes | Level | Category |
+--------+---------------+-------+----------+
| rmcap | Not Impacted | B | NORMAL |
| | | | |
| omcap | Not Impacted | B | NORMAL |
| | | | |
| mfcap | Not Impacted | B | NORMAL |
| | | | |
| mscap | Not Impacted | B | NORMAL |
| | | | |
| lcfg | Not Impacted | B | NORMAL |
| | | | |
| secap | Not Impacted | S | NORMAL |
| | | | |
+--------+---------------+-------+----------+
draft-ietf-mmusic-sdp-media-capabilities Attribute Analysis
5.30. RFC4567 - Key Management Extensions for SDP and RTSP
RFC4567 [RFC4567] defines general extensions for Session Description
Protocol (SDP) and Real Time Streaming Protocol (RTSP) to carry
messages, as specified by a key management protocol, in order to
secure the media. These extensions are presented as a framework, to
be used by one or more key management protocols. As such, their use
is meaningful only when complemented by an appropriate key management
protocol.
+-----------+----------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-----------+----------------------------------+-------+------------+
| key-mgmt | Key management protocol MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
+-----------+----------------------------------+-------+------------+
RFC4567 Attribute Analysis
5.31. RFC4572 - Comedia over TLS in SDP
RFC4572 [RFC4572] specifies how to establish secure connection-
oriented media transport sessions over the Transport Layer Security
(TLS) protocol using the Session Description Protocol (SDP). It
defines a new SDP protocol identifier, 'TCP/TLS'. It also defines
the syntax and semantics for an SDP 'fingerprint' attribute that
identifies the certificate that will be presented for the TLS
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session. This mechanism allows media transport over TLS connections
to be established securely, so long as the integrity of session
descriptions is assured.
+--------------+-------------------------------+-------+------------+
| Name | Notes | Level | Category |
+--------------+-------------------------------+-------+------------+
| fingerprint | Fingerprint value MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
+--------------+-------------------------------+-------+------------+
RFC4572 Attribute Analysis
5.32. RFC4570 - SDP Source Filters
RFC4570 [RFC4570] describes how to adapt the Session Description
Protocol (SDP) to express one or more source addresses as a source
filter for one or more destination "connection" addresses. It
defines the syntax and semantics for an SDP "source-filter" attribute
that may reference either IPv4 or IPv6 address(es) as either an
inclusive or exclusive source list for either multicast or unicast
destinations. In particular, an inclusive source-filter can be used
to specify a Source-Specific Multicast (SSM) session
+----------------+-----------------------------+-------+------------+
| Name | Notes | Level | Category |
+----------------+-----------------------------+-------+------------+
| source-filter | he attribute MUST be | B | IDENTICAL |
| | repeated across all m=lines | | |
| | multiplexed | | |
| | | | |
+----------------+-----------------------------+-------+------------+
RFC4570 Attribute Analysis
5.33. RFC6128 - RTCP Port for Multicast Sessions
The Session Description Protocol (SDP) has an attribute that allows
RTP applications to specify an address and a port associated with the
RTP Control Protocol (RTCP) traffic. In RTP-based source-specific
multicast (SSM) sessions, the same attribute is used to designate the
address and the RTCP port of the Feedback Target in the SDP
description. However, the RTCP port associated with the SSM session
itself cannot be specified by the same attribute to avoid ambiguity,
and thus, is required to be derived from the "m=" line of the media
description. Deriving the RTCP port from the "m=" line imposes an
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unnecessary restriction. RFC6128 [RFC6128] removes this restriction
by introducing a new SDP attribute.
+-----------------+----------------------------+-------+------------+
| Name | Notes | Level | Category |
+-----------------+----------------------------+-------+------------+
| multicast-rtcp | Multicast RTCP port MUST | B | IDENTICAL |
| | be identical across all | | |
| | the m=lines | | |
| | | | |
+-----------------+----------------------------+-------+------------+
RFC6128 Attribute Analysis
5.34. RFC6189 - ZRTP
RFC6189 [RFC6189] defines ZRTP, a protocol for media path Diffie-
Hellman exchange to agree on a session key and parameters for
establishing unicast Secure Real-time Transport Protocol (SRTP)
sessions for Voice over IP (VoIP) applications.
+------------+-------------------------------+-------+--------------+
| Name | Notes | Level | Category |
+------------+-------------------------------+-------+--------------+
| zrtp-hash | Complicates if all the | M | NOT |
| | m=lines are not authenticated | | RECOMMENDED |
| | as given in the example | | |
| | below | | |
| | | | |
+------------+-------------------------------+-------+--------------+
RFC6189 Attribute Analysis
Example: Multiplexing media descriptions having attribute zrtp-hash
defined with the media descriptions lacking it, would either
complicate the handling of multiplexed stream or fail multiplexing.
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v=0
o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com
s=
c=IN IP4 client.biloxi.example.com
t=0 0
m=audio 3456 RTP/AVP 97
a=rtpmap:97 iLBC/8000
<allOneLine>
a=zrtp-hash:1.10 fe30efd02423cb054e50efd0248742ac7a52c8f91bc2
df881ae642c371ba46df
</allOneLine>
m=video 34567 RTP/AVP 31
a=rtpmap:31 H261/90000
5.35. RFC4145 - Connection-Oriented Media
RFC4145 [RFC4145] describes how to express media transport over TCP
using the Session Description Protocol (SDP). It defines the SDP
'TCP' protocol identifier, the SDP 'setup' attribute, which describes
the connection setup procedure, and the SDP 'connection' attribute,
which handles connection reestablishment.
+-------------+--------------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------------+--------------------------------+-------+------------+
| setup | Should be identical across all | B | IDENTICAL |
| | m=lines | | |
| | | | |
| connection | Should be identical across all | B | IDENTICAL |
| | m=lines | | |
| | | | |
+-------------+--------------------------------+-------+------------+
RFC4145 Attribute Analysis
5.36. RFC5159 - OMA BCAST SDP Attributes
RFC5159 [RFC5159] provides descriptions of Session Description
Protocol (SDP) attributes used by the Open Mobile Alliance's
Broadcast Service and Content Protection specification.
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+---------------------+-------+-------+----------+
| Name | Notes | Level | Category |
+---------------------+-------+-------+----------+
| bcastversion | | S | TBD |
| | | | |
| stkmstream | | B | TBD |
| | | | |
| SRTPAuthentication | | M | TBD |
| | | | |
| SRTPROCTxRate | | M | TBD |
| | | | |
+---------------------+-------+-------+----------+
RFC5159 Attribute Analysis
5.37. RFC6193 - Media Description for IKE in SDP
RFC6193 [RFC6193] specifies how to establish a media session that
represents a virtual private network using the Session Initiation
Protocol for the purpose of on-demand media/application sharing
between peers. It extends the protocol identifier of the Session
Description Protocol (SDP) so that it can negotiate use of the
Internet Key Exchange Protocol (IKE) for media sessions in the SDP
offer/answer model.
+-------------------+--------------------------+-------+------------+
| Name | Notes | Level | Category |
+-------------------+--------------------------+-------+------------+
| ike-setup | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
| psk-fingerprint | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
| ike-esp | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
| ike-esp-udpencap | Attribute MUST be | B | IDENTICAL |
| | identical across all the | | |
| | m=lines | | |
| | | | |
+-------------------+--------------------------+-------+------------+
RFC6193 Attribute Analysis
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With the above SDP constraints, a session multiplexed with multiple
m=lines will use only one IPSec association for all of the m= lines.
5.38. RFC6064 - SDP and RTSP Extensions for 3GPP
The Packet-switched Streaming Service (PSS) and the Multimedia
Broadcast/Multicast Service (MBMS) defined by 3GPP use the Session
Description Protocol (SDP) and Real Time Streaming Protocol (RTSP)
with some extensions. RFC6064 [RFC6064] provides information about
these extensions and registers the RTSP and SDP extensions with IANA.
+-----------------------+----------------------+------+-------------+
| Name | Notes | Leve | Category |
| | | l | |
+-----------------------+----------------------+------+-------------+
| X-predecbufsize | Case1:Aggregate | M | NOT |
| | total when video | | RECOMMENDED |
| | m-lines are | | |
| | muxed Case2:Multiple | | |
| | xing with audio | | |
| | m=lines is invalid | | |
| | | | |
| X-initpredecbufperiod | Case1:Aggregate | M | NOT |
| | total when video | | RECOMMENDED |
| | m-lines are | | |
| | muxed Case2:Multiple | | |
| | xing with audio | | |
| | m=lines is invalid | | |
| | | | |
| X-initpostdecbufperio | Case1:Aggregate | M | NOT |
| d | total when video | | RECOMMENDED |
| | m-lines are | | |
| | muxed Case2:Multiple | | |
| | xing with audio | | |
| | m=lines is invalid | | |
| | | | |
| X-decbyterate | Case1:Aggregate | M | NOT |
| | total when video | | RECOMMENDED |
| | m-lines are | | |
| | muxed Case2:Multiple | | |
| | xing with audio | | |
| | m=lines is invalid | | |
| | | | |
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| 3gpp-videopostdecbufs | Case1:Aggregate | M | NOT |
| ize | total when video | | RECOMMENDED |
| | m-lines are muxed. | | |
| | Case2:Multiplexing | | |
| | with audio m=lines | | |
| | is invalid | | |
| | | | |
| framesize | Not Impacted | M | NORMAL |
| | | | |
| 3GPP-Integrity-Key | Not Impacted | S | NORMAL |
| | | | |
| 3GPP-SRTP-Config | Same config SHALL | M | NORMAL |
| | apply to all the | | |
| | m=lines multiplexed | | |
| | | | |
| alt,alt-default-id | Specifying alternate | M | TBD |
| | m=lines when session | | |
| | with mulitple | | |
| | m=lines of different | | |
| | types cannot be | | |
| | clearly specified | | |
| | | | |
| alt-group | Complicates | M | TBD |
| | selection of | | |
| | alternate m=lines | | |
| | grouped with | | |
| | alt-group on | | |
| | mulitplexing | | |
| | | | |
| 3GPP-Adaptation-Suppo | | M | TBD |
| rt | | | |
| | | | |
| 3GPP-QoE-Metricsn | | B | TBD |
| | | | |
| 3GPP-Asset-Informatio | | B | TBD |
| | | | |
| | | | |
| mbms-mode | | B | TBD |
| | | | |
| mbms-flowid | Multiplexing | M | TBD |
| | multiple m=lines | | |
| | complicates FEC | | |
| | mappings to the | | |
| | transport | | |
| | addresses. | | |
| | | | |
| mbms-repair | | B | TBD |
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| | | | |
+-----------------------+----------------------+------+-------------+
RFC6064 Attribute Analysis
OPEN ISSUE:MW: These paramters are defined for the declarative
usage in RTSP or multicast/broadcast and dont have O/A defintions.
Does BUNDLE apply only to O/A usage ?
5.39. RFC3108 - ATM SDP
RFC3108 [RFC3108] describes conventions for using the Session
Description Protocol (SDP) described for controlling ATM Bearer
Connections, and any associated ATM Adaptation Layer (AAL)
+------------------------+--------------+-------+----------+
| Name | Notes | Level | Category |
+------------------------+--------------+-------+----------+
| aalType | NOT IMPACTED | B | NORMAL |
| eecid | NOT IMPACTED | B | NORMAL |
| aalType | NOT IMPACTED | B | NORMAL |
| capability | NOT IMPACTED | B | NORMAL |
| qosClass | NOT IMPACTED | B | NORMAL |
| bcob | NOT IMPACTED | B | NORMAL |
| stc | NOT IMPACTED | B | NORMAL |
| upcc | NOT IMPACTED | B | NORMAL |
| atmQOSparms | NOT IMPACTED | B | NORMAL |
| atmTrfcDesc | NOT IMPACTED | B | NORMAL |
| abrParms | NOT IMPACTED | B | NORMAL |
| abrSetup | NOT IMPACTED | B | NORMAL |
| bearerType | NOT IMPACTED | B | NORMAL |
| lij | NOT IMPACTED | B | NORMAL |
| anycast | NOT IMPACTED | B | NORMAL |
| cache | NOT IMPACTED | B | NORMAL |
| bearerSigIE | NOT IMPACTED | B | NORMAL |
| aalApp | NOT IMPACTED | B | NORMAL |
| cbrRate | NOT IMPACTED | B | NORMAL |
| sbc | NOT IMPACTED | B | NORMAL |
| clkrec | NOT IMPACTED | B | NORMAL |
| fec | NOT IMPACTED | B | NORMAL |
| prtfl | NOT IMPACTED | B | NORMAL |
| structure | NOT IMPACTED | B | NORMAL |
| cpsSDUsize | NOT IMPACTED | B | NORMAL |
| aal2CPS | NOT IMPACTED | B | NORMAL |
| aal2CPSSDUrate | NOT IMPACTED | B | NORMAL |
| aal2sscs3661unassured | NOT IMPACTED | B | NORMAL |
| aal2sscs3661assured | NOT IMPACTED | B | NORMAL |
| aal2sscs3662 | NOT IMPACTED | B | NORMAL |
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| aal5sscop | NOT IMPACTED | B | NORMAL |
| atmmap | NOT IMPACTED | B | NORMAL |
| silenceSupp | NOT IMPACTED | B | NORMAL |
| ecan | NOT IMPACTED | B | NORMAL |
| gc | NOT IMPACTED | B | NORMAL |
| profileDesc | NOT IMPACTED | B | NORMAL |
| vsel | NOT IMPACTED | B | NORMAL |
| dsel | NOT IMPACTED | B | NORMAL |
| fsel | NOT IMPACTED | B | NORMAL |
| onewaySel | NOT IMPACTED | B | NORMAL |
| codecconfig | NOT IMPACTED | B | NORMAL |
| isup_usi | NOT IMPACTED | B | NORMAL |
| isup_usi | NOT IMPACTED | B | NORMAL |
| chain | NOT IMPACTED | B | NORMAL |
| | | | |
+------------------------+--------------+-------+----------+
RFC3108 Attribute Analysis
RFC3108 describes conventions for using the Session Description
Protocol (SDP) for characterizing ATM bearer connections using an
AAL1, AAL2 or AAL5 adaptation layers. For AAL1, AAL2 and AAL5,
bearer connections can be used to transport single media streams. In
addition, for AAL1 and AAL2, multiple media streams may be
multiplexed into a bearer connection. For all adaptation types
(AAL1, AAL2 and AAL5), bearer connections may be bundled into a
single media group. In all cases addressed by RFC3108, a real-time
media stream (voice, video, voiceband data, pseudo-wire and others)
or a multiplex of media streams is mapped directly into an ATM
connection. RFC3108 does not address cases where ATM serves as a
low-level transport pipe for IP packets which in turn may carry one
or more real-time (e.g. VoIP) media sessions with a life-cycle
different from that of the underlying ATM transport.
5.40. 3GPP TS 24.182
3GPP TS 24.182 [3GPP TS 24.182] specifies IP multimedia subsystem
Custom Alerting tones
+-------------+----------------------------------+-------+----------+
| Name | Notes | Level | Category |
+-------------+----------------------------------+-------+----------+
| g.3gpp.cat | Usage defined for the IP | M | NORMAL |
| | Multimedia Subsystem | | |
| | | | |
+-------------+----------------------------------+-------+----------+
3GPP TS 24.182 Attribute Analysis
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5.41. 3GPP TS 24.183
3GPP TS 24.183 [3GPP TS 24.183]specifies IP multimedia subsystem
Custom Ringing Signal
+-------------+----------------------------------+-------+----------+
| Name | Notes | Level | Category |
+-------------+----------------------------------+-------+----------+
| g.3gpp.crs | Usage defined for the IP | M | NORMAL |
| | Multimedia Subsystem | | |
| | | | |
+-------------+----------------------------------+-------+----------+
3GPP TS 24.183 Attribute Analysis
5.42. 3GPP TS 24.229
3GPP TS 24.229 [3GPP TS 24.229]IP multimedia call control protocol
based on Session Initial protocol and Session Description Protocol.
+------------------+---------------------------+-------+------------+
| Name | Notes | Level | Category |
+------------------+---------------------------+-------+------------+
| secondary-realm | Per media-level attribute | M | TRANSPORT |
| | MUST be used per | | |
| | underlying transport | | |
| | | | |
| visited-realm | Per media-level attribute | M | TRANSPORT |
| | MUST be used per | | |
| | underlying transport | | |
| | | | |
| omr-m-cksum | Not Impacted | M | NORMAL |
| | | | |
| omr-s-cksum | Not Impacted | M | NORMAL |
| | | | |
| omr-m-att | Not Impacted | M | NORMAL |
| | | | |
| omr-s-bw | Not Impacted | M | NORMAL |
| | | | |
| omr-s-bw | Not Impacted | M | NORMAL |
| | | | |
| omr-m-att | Not Impacted | M | NORMAL |
| | | | |
| omr-codecs | Not Impacted | M | NORMAL |
| | | | |
+------------------+---------------------------+-------+------------+
3GPP TS 24.229 Attribute Analysis
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5.43. ITU T.38
ITU T.38[T.38] defines procedures for real-time Group 3 fascimile
communications over IP netowrks.
+------------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------------------+---------------+-------+----------+
| T38FaxVersion | Not Impacted | S | NORMAL |
| | | | |
| T38MaxBitRate | Not Impacted | S | NORMAL |
| | | | |
| T38FaxFillBitRemoval | Not Impacted | S | NORMAL |
| | | | |
| T38FaxTranscodingMMR | Not Impacted | S | NORMAL |
| | | | |
| T38FaxTranscodingJBIG | Not Impacted | S | NORMAL |
| | | | |
| T38FaxRateManagement | Not Impacted | S | NORMAL |
| | | | |
| T38FaxMaxBuffer | Not Impacted | S | NORMAL |
| | | | |
| T38FaxMaxDatagram | Not Impacted | S | NORMAL |
| | | | |
| T38FaxUdpEC | Not Impacted | S | NORMAL |
| | | | |
+------------------------+---------------+-------+----------+
Historic Attribute Analysis
The ITU T.38 attributes are clearly unaffected by multiplexing and
are specific to the working of the fax protocol itself.
5.44. 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 | Category |
+-----------+------------------------------------+-------+----------+
| h248item | It is also only applicable for | B | SPECIAL |
| | signaling the inclusion of H.248 | | |
| | extension packages to a gateway | | |
| | via the local and remote | | |
| | descriptors. The attribute itself | | |
| | is unaffected by multiplexing, but | | |
| | the packaged referenced in a | | |
| | specific use of the attribute may | | |
| | be impacted. Further analysis of | | |
| | each package is needed to | | |
| | determine if there is an issue. | | |
| | This is only a concern in | | |
| | environments using a decomposed | | |
| | server/gateway with H.248 signaled | | |
| | between them. The ITU-T will need | | |
| | to do further analysis of various | | |
| | packages when they specify how to | | |
| | signal the use of multiplexing to | | |
| | a gateway. | | |
| | | | |
+-----------+------------------------------------+-------+----------+
Historic Attribute Analysis
5.45. RFC4975 - The Message Session Relay Protocol
RFC4975 [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.
+-----------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-----------------------+---------------+-------+----------+
| accept-types | Not Impacted | M | NORMAL |
| | | | |
| accept-wrapped-types | Not Impacted | M | NORMAL |
| | | | |
| max-size | Not Impacted | M | NORMAL |
| | | | |
| path | Not Impacted | M | NORMAL |
| | | | |
+-----------------------+---------------+-------+----------+
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RFC4975 Attribute Analysis
5.46. Historical
This section specifies analysis for the attributes that are included
for historic usage alone by the [IANA].
+---------------------+-----------------+---------------+----------+
| Name | Notes | Level | Category |
+---------------------+-----------------+---------------+----------+
| rtpred1 | Not Applicable | Not-Applcable | TBD |
| | | | |
| rtpred2 | Not Applicable | Not-Applcable | TBD |
| | | | |
| PSCid | Not Applicable | Not-Applcable | TBD |
| | | | |
| bc_service | Not Applicable | Not-Applcable | TBD |
| | | | |
| bc_program | Not Applicable | Not-Applcable | TBD |
| | | | |
| bc_service_package | Not Applicable | Not-Applcable | TBD |
| | | | |
+---------------------+-----------------+---------------+----------+
Unknowns Attribute Analysis
6. bwtype Attribute Analysis
This section specifies handling of specific bandwidth attributes when
used in multiplexing scenarios.
6.1. RFC4566 - SDP: Session Description Protocol
+------------+-----------------------------------+-------+----------+
| Name | Notes | Level | Category |
+------------+-----------------------------------+-------+----------+
| bwtype:CT | Aggregate bandwidth for the | S | NORMAL |
| | conference | | |
| | | | |
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| bwtype:AS | There are 2 interpretations for | B | NORMAL, |
| | this attribute As a session | | SUM |
| | attribute, it specifies the | | |
| | session aggregate unless | | |
| | media-level b=RR and/or b=RS | | |
| | attributes are used. Under this | | |
| | interpretation the multiplexing | | |
| | scheme has no impact and belongs | | |
| | to NORMAL category. For the | | |
| | media level usage, the aggregate | | |
| | of individual bandwidth values is | | |
| | considered. | | |
| | | | |
+------------+-----------------------------------+-------+----------+
RFC4566 bwtype Analysis
6.2. RFC3556 - SDP Bandwidth Modifiers for RTCP Bandwidth
RFC3556 [RFC3556] defines an extension to the Session Description
Protocol (SDP) to specify two additional modifiers for the bandwidth
attribute. These modifiers may be used to specify the bandwidth
allowed for RTP Control Protocol (RTCP) packets in a Real-time
Transport Protocol (RTP) session
+------------+--------------------------------+-------+-------------+
| Name | Notes | Level | Category |
+------------+--------------------------------+-------+-------------+
| bwtype:RS | S level usage represents | B | NORMAL,SUM |
| | session aggregate and media | | |
| | level usage indicates SUM of | | |
| | the individual values while | | |
| | multiplexing | | |
| | | | |
| bwtype:RR | S level usage represents | B | NORMAL,SUM |
| | session aggregate and media | | |
| | level usage indicates SUM of | | |
| | the individual values while | | |
| | multiplexing | | |
| | | | |
+------------+--------------------------------+-------+-------------+
RFC3556 bwtype Analysis
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6.3. RFC3890 - Bandwidth Modifier for SDP
RFC3890 [RFC3890] defines a Session Description Protocol (SDP)
Transport Independent Application Specific Maximum (TIAS) bandwidth
modifier that does not include transport overhead; instead an
additional packet rate attribute is defined. The transport
independent bit-rate value together with the maximum packet rate can
then be used to calculate the real bit-rate over the transport
actually used.
+--------------+---------------------------------+-------+----------+
| Name | Notes | Level | Category |
+--------------+---------------------------------+-------+----------+
| bwtype:TIAS | The usage of TIAS is not | B | TBD |
| | clearly defined Offer/Answer | | |
| | usage. | | |
| | | | |
| maxprate | The usage of TIAS and maxprate | B | TBD |
| | is not well defined under | | |
| | multiplexing | | |
| | | | |
+--------------+---------------------------------+-------+----------+
RFC3890 bwtype Analysis
The intention of TIAS is that the media level bit-rate is multiplied
with the known per-packet overhead for the selected transport and the
maxprate value to determine the worst case bit-rate from the
transport to more accurately capture the required usage. Summing
TIAS values independently across m=lines and multiplying the computed
sum with maxprate and the per-packet overhead would inflate the value
significantly. Instead performing multiplication and adding the
individual values is a more appropriate usage. This still ignores
the fact that this is a send side declaration, and not intended for
receiver negotiation.
7. rtcp-fb Attribute Analysis
This section analyzes rtcp-fb SDP attributes [RTCP-FB].
7.1. RFC4585 - RTP/AVPF
RFC4585 [RFC4585] defines an extension to the Audio-visual Profile
(AVP) that enables receivers to provide, statistically, more
immediate feedback to the senders and thus allows for short-term
adaptation and efficient feedback-based repair mechanisms to be
implemented.
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+----------+-----------------------------------+-------+------------+
| Attr | Notes | Level | Category |
| Name | | | |
+----------+-----------------------------------+-------+------------+
| ack | Not Impacted | M | NORMAL |
| rpsi | | | |
| | | | |
| ack app | Feedback parameters MUST be | M | SPECIAL |
| | handled in the app specifc way | | |
| | when multiplexed | | |
| | | | |
| nack | Not Impacted | M | NORMAL |
| | | | |
| nack | Not Impacted | M | NORMAL |
| pli | | | |
| | | | |
| nack | Not Impacted | M | NORMAL |
| sli | | | |
| | | | |
| nack | Not Impacted | M | NORMAL |
| rpsi | | | |
| | | | |
| nack | Feedback parameters MUST be | M | SPECIAL |
| app | handled in the app specifc way | | |
| | when multiplexed | | |
| | | | |
| trr-int | This attribute applies to RTP | M | IDENTICAL |
| | Session as a whole | | |
| | | | |
+----------+-----------------------------------+-------+------------+
RFC4585 Attribute Analysis
7.2. RFC5104 - Codec Control Messages in AVPF
RFC5104 [RFC5104] specifies a few extensions to the messages defined
in the Audio-Visual Profile with Feedback (AVPF). They are helpful
primarily in conversational multimedia scenarios where centralized
multipoint functionalities are in use. However, some are also usable
in smaller multicast environments and point-to-point calls.
+-----------+--------------+-------+----------+
| Attr Name | Notes | Level | Category |
+-----------+--------------+-------+----------+
| ccm | Not Impacted | M | Normal |
| | | | |
+-----------+--------------+-------+----------+
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RFC5104 Attribute Analysis
7.3. RFC6285 - Unicast-Based RAMS
+-----------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-----------+---------------+-------+----------+
| nack rai | Not Impacted | M | NORMAL |
| | | | |
+-----------+---------------+-------+----------+
RFC6285 Attribute Analysis
7.4. RFC6679 - ECN for RTP over UDP/IP
RFC6679 [RFC6679] specifies how Explicit Congestion Notification
(ECN) can be used with the Real-time Transport Protocol (RTP) running
over UDP, using the RTP Control Protocol (RTCP) as a feedback
mechanism. It defines a new RTCP Extended Report (XR) block for
periodic ECN feedback, a new RTCP transport feedback message for
timely reporting of congestion events, and a Session Traversal
Utilities for NAT (STUN) extension used in the optional
initialisation method using Interactive Connectivity Establishment
(ICE)
+------------------+---------------------------+-------+------------+
| Name | Notes | Level | Category |
+------------------+---------------------------+-------+------------+
| ecn-capable-rtp | ECN markup are enabled at | M | IDENTICAL |
| | the RTP Session level | | |
| | | | |
| nack ecn | This attribute enables | M | IDENTICAL |
| | ECN at the RTP session | | |
| | level | | |
| | | | |
+------------------+---------------------------+-------+------------+
RFC6679 Attribute Analysis
7.5. RFC6642 - Third-Party Loss Report
In a large RTP session using the RTP Control Protocol (RTCP) feedback
mechanism defined in RFC 4585 [RFC4585], a feedback target may
experience transient overload if some event causes a large number of
receivers to send feedback at once. This overload is usually avoided
by ensuring that feedback reports are forwarded to all receivers,
allowing them to avoid sending duplicate feedback reports. However,
there are cases where it is not recommended to forward feedback
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reports, and this may allow feedback implosion. RFC6642 [RFC6642]
memo discusses these cases and defines a new RTCP Third-Party Loss
Report that can be used to inform receivers that the feedback target
is aware of some loss event, allowing them to suppress feedback.
Associated Session Description Protocol (SDP) signaling is also
defined.
+-------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-------------+---------------+-------+----------+
| nack tllei | Not Impacted | M | NORMAL |
| | | | |
| nack pslei | Not Impacted | M | NORMAL |
| | | | |
+-------------+---------------+-------+----------+
RFC6642 Attribute Analysis
7.6. RFC5104 - Codec Control Messages in AVPF
+------------+--------------+-------+----------+
| Attr Name | Notes | Level | Category |
+------------+--------------+-------+----------+
| ccm fir | Not Impacted | M | NORMAL |
| | | | |
| ccm tmmbr | Not Impacted | M | NORMAL |
| | | | |
| ccm tstr | Not Impacted | M | NORMAL |
| | | | |
| ccm vbcm | Not Impacted | M | NORMAL |
| | | | |
+------------+--------------+-------+----------+
RFC5104 Attribute Analysis
8. group Attribute Analysis
This section analyzes SDP "group" semantics [GROUP-SEM].
8.1. RFC5888 - SDP Grouping Framework
RFC5888 [RFC5888] defines a framework to group "m" lines in the
Session Description Protocol (SDP) for different purposes.
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+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| group:LS | Not Impacted | S | NORMAL |
| | | | |
| group:FID | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC5888 Attribute Analysis
8.2. RFC3524 - Mapping Media Streams to Resource Reservation Flows
RFC3524 [RFC3524] defines an extension to the Session Description
Protocol (SDP) grouping framework. It allows requesting a group of
media streams to be mapped into a single resource reservation flow.
The SDP syntax needed is defined, as well as a new "semantics"
attribute called Single Reservation Flow (SRF).
+------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------+---------------+-------+----------+
| group:SRF | Not Impacted | S | NORMAL |
| | | | |
+------------+---------------+-------+----------+
RFC3524 Attribute Analysis
8.3. RFC4091 - ANAT Semantics
RFC4091 [RFC4091] defines the Alternative Network Address Types
(ANAT) semantics for the Session Description Protocol (SDP) grouping
framework. The ANAT semantics allow alternative types of network
addresses to establish a particular media stream.
+-------------+----------------+-------+------------------+
| Name | Notes | Level | Category |
+-------------+----------------+-------+------------------+
| group:ANAT | Not Impacted | S | NOT RECOMMENDED |
| | | | |
+-------------+----------------+-------+------------------+
RFC4091 Attribute Analysis
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8.4. RFC5956 - FEC Grouping Semantics in SDP
RFC5956 [RFC5956] defines the semantics for grouping the associated
source and FEC-based (Forward Error Correction) repair flows in the
Session Description Protocol (SDP). The semantics defined in the
document are to be used with the SDP Grouping Framework (RFC 5888).
These semantics allow the description of grouping relationships
between the source and repair flows when one or more source and/or
repair flows are associated in the same group, and they provide
support for additive repair flows. SSRC-level (Synchronization
Source) grouping semantics are also defined in this document for
Real-time Transport Protocol (RTP) streams using SSRC multiplexing.
+---------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+---------------+---------------+-------+----------+
| group:FEC-FR | Not Impacted | S | NORMAL |
| | | | |
+---------------+---------------+-------+----------+
RFC5956 Attribute Analysis
8.5. RFC5583 - Signaling Media Decoding Dependency in SDP
RFC5583 [RFC5583] defines semantics that allow for signaling the
decoding dependency of different media descriptions with the same
media type in the Session Description Protocol (SDP). This is
required, for example, if media data is separated and transported in
different network streams as a result of the use of a layered or
multiple descriptive media coding process.
+-------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+-------------+---------------+-------+----------+
| depend lay | Not Impacted | M | NORMAL |
| | | | |
| depend mdc | Not Impacted | M | NORMAL |
| | | | |
+-------------+---------------+-------+----------+
RFC5583 Attribute Analysis
OPEN ISSUE:Eckel: If PTs are not unique across the m=lines
BUNDLED, how should this be handled ?
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9. ssrc-group Attribute Analysis
This section analyzes "ssrc-group" semantics [SSRC-GROUP].
9.1. RFC5576 - Source-Specific SDP Attributes
+---------+---------------+-------+----------+
| Name | Notes | Level | Category |
+---------+---------------+-------+----------+
| FID | Not Impacted | M | NORMAL |
| | | | |
| FEC | Not Impacted | M | NORMAL |
| | | | |
| FEC-FR | Not Impacted | M | NORMAL |
| | | | |
+---------+---------------+-------+----------+
RFC5576 Attribute Analysis
10. QoS Mechanism Token Analysis
This section analyzes QoS tokes specified with SDP[QOS].
10.1. RFC5432 - QoS Mechanism Selection in SDP
+-------+----------------------------------------+-------+----------+
| Name | Notes | Level | Category |
+-------+----------------------------------------+-------+----------+
| rsvp | Not Impacted, since QOS mechanisms are | B | NORMAL |
| | applied per flow. | | |
| | | | |
| nsis | Not Impacted, since QOS mechanisms are | B | NORMAL |
| | applied per flow. | | |
| | | | |
+-------+----------------------------------------+-------+----------+
RFC5432 Attribute Analysis
11. k= Attribute Analysis
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11.1. RFC4566 SDP: Session Description Protocol
+------+------------------------------------+-------+---------------+
| Name | Notes | Level | Category |
+------+------------------------------------+-------+---------------+
| k= | It is NOT recommended to use this | S | NOT |
| | attribute | | RECOMMENDED |
| | | | |
+------+------------------------------------+-------+---------------+
RFC4566 Attribute Analysis
12. content Atribute Analysis
12.1. RFC4796 - MSRP Relays
+------------------+---------------+-------+----------+
| Name | Notes | Level | Category |
+------------------+---------------+-------+----------+
| content:slides | Not Impacted | M | NORMAL |
| | | | |
| content:speaker | Not Impacted | M | NORMAL |
| | | | |
| content:main | Not Impacted | M | NORMAL |
| | | | |
| content:sl | Not Impacted | M | NORMAL |
| | | | |
| content:alt | Not Impacted | M | NORMAL |
| | | | |
+------------------+---------------+-------+----------+
RFC4796 Attribute Analysis
13. Payload Formats
13.1. RFC5109 - RTP Payload Format for Generic FEC
RFC5109 [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 | Category |
+---------------------+----------------------+-------+--------------+
| audio/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMENDED |
| | reuse of SSRCs | | |
| | | | |
| video/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMENDED |
| | reuse of SSRCs | | |
| | | | |
| text/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMEDED |
| | reuse of SSRCs | | |
| | | | |
| application/ulpfec | Not recommended for | M | NOT |
| | multiplexing due to | | RECOMMENDED |
| | reuse of SSRCs | | |
| | | | |
+---------------------+----------------------+-------+--------------+
RFC5109 Payload Format Analysis
Draft draft-lennox-payload-ulp-ssrc-mux proposes a simple fix to make
it possible to use ULP with multipelxing and ULP is allowed when used
with that.
14. IANA Considerations
IANA shall register categories from this specification by expanding
the Session Description Protocol (SDP) Parameters table with a column
listing categories against each SDP parameter.
+---------------------+
| Category |
+---------------------+
| NORMAL |
+---------------------+
| NOT RECOMMENDED |
+---------------------+
| IDENTICAL |
+---------------------+
| TRANSPORT |
+---------------------+
| SPECIAL |
----------------------
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15. Security Considerations
All the attributes which involve security key needs a careful review
to ensure two-time pad vulnerability is not created
16. Acknowledgments
I would like to thank Cullen Jennings for suggesting the categories,
contributing text and helping review the draft. I would also link to
thank Magnus, Christer and Dan on suggesting stuctural changes
helping improve the document readability.
I would like also to thank following experts on their inputs and
reviews as listed - Rohan Mahy(5.45), Eric Burger(5.22), Christian
Huitema(5.13), Christer Holmberg(5.22,5.40,5.41), Richard Ejzak
(5.36,5.42,5.43,5.44,), Colin Perkins(5.7,5.8), Magnus
westerlund(5.3,5.9,6.1,6.2,6.3,8.3,5.2,7,8,9), Roni
Evens(5.12,5.27,8.4), Subha Dhesikan(5.5,12.1), Dan
Wing(5.6,5.11,5.30,5.34,5.37), Ali C
Begen(5.1,5.16,5.18,5.21,5.33,8.2,13.1,10.4,15.1), Bo Burman
(7.2,7.6), Charles Eckel(5.14,5.23,5.24,10.5), Paul Kyzivat(5.24),
Ian Johansson (5.11), Saravanan Shanmugham(5.10), Paul E Jones(5.25),
Rajesh Kumar (5.39), Jonathan Lennox (5.31,5,14,11.1), Mo
Zanaty(5.4,5.19,10.1,10.5)
17. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
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 explantion 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 Maintainence 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.
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Changes from draft-nandakumar-mmusic-mux-attributes-01
o Replaced Category BAD with NOT RECOMMENDED.
o Added Category TBD.
o Updated IANA Consideration Section.
Changes from draft-nandakumar-mmusic-mux-attributes-00
o Added new section for dealing with FEC payload types.
18. References
18.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
18.2. Informative References
[3GPP TS 24.182]
"IP Multimedia Subsystem (IMS) Customized Alerting Tones
(CAT); Protocol specification",
<http://www.3gpp.org/ftp/Specs/html-info/24182.htm>.
[3GPP TS 24.183]
"IP Multimedia Subsystem (IMS) Customized Ringing Signal
(CRS); Protocol specification",
<http://www.3gpp.org/ftp/Specs/html-info/24183.htm>.
[3GPP TS 24.229]
"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>.
[ACK-NACK]
"S Description Protocol (SDP) RTCP ACK/NACK Feedback
attributes", <http://www.iana.org/assignments/
sdp-parameters/sdp-parameters.xml#sdp-parameters-15>.
[CCM] "S Description Protocol (SDP) RTCP-FB Codec Control
Messages", <http://www.iana.org/assignments/
sdp-parameters/sdp-parameters.xml#sdp-parameters-19>.
[GROUP-SEM]
"S Description Protocol (SDP) "group" semantics", <http://
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www.iana.org/assignments/sdp-parameters/
sdp-parameters.xml#sdp-parameters-13>.
[H.248.15]
"Gateway control protocol: SDP H.248 package attribute",
<http://www.itu.int/rec/T-REC-H.248.15>.
[I-D.ietf-avt-multiplexing-rtp]
El-Khatib, K., Luo, G., Bochmann, G., and Pinjiang. Feng,
"Multiplexing Scheme for RTP Flows between Access
Routers", Internet-Draft http://tools.ietf.org/html/
draft-ietf-avt-multiplexing-rtp-01, October 1999.
[I-D.ietf-mmusic-sdp-bundle-negotiation]
Holmberg, C., Alvestrand, H., and C. Jennings,
"Multiplexing Negotiation Using Session Description
Protocol (SDP) Port Numbers",
draft-ietf-mmusic-sdp-bundle-negotiation-03 (work in
progress), February 2013.
[IANA] "S Description Protocol (SDP) Parameters", <http://
www.iana.org/assignments/sdp-parameters/
sdp-parameters.xml>.
[MEDIA_CAP]
Kaplan, H., Hedayat, K., and N. Venna, "S Description
Protocol (SDP) Media Capabilities Negotiation",
draft-ietf-mmusic-sdp-media-capabilities-17 (work in
progress), January 2013.
[MEDIA_LOOPBACK]
Kaplan, H., 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", draft-ietf-mmusic-media-loopback-27 (work
in progress), January 2013.
[QOS] "S Description Protocol (SDP) QoS Mechanism Tokens", <http
://www.iana.org/assignments/sdp-parameters/
sdp-parameters.xml#sdp-parameters-20>.
[RFC3108] Kumar, R. and M. Mostafa, "Conventions for the use of the
Session Description Protocol (SDP) for ATM Bearer
Connections", RFC 3108, May 2001.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
June 2002.
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[RFC3407] Andreasen, F., "S Description Protocol (SDP) Simple
Capability Declaration", RFC 3407, October 2002.
[RFC3524] Camarillo, G. and A. Monrad, "Mapping of Media Streams to
Resource Reservation Flows", RFC 3524, April 2003.
[RFC3556] Casner, S., "S Description Protocol (SDP) Bandwidth
Modifiers for RTP Control Protocol (RTCP) Bandwidth",
RFC 3556, July 2003.
[RFC3605] Huitema, C., "Real Time Control Protocol (RTCP) attribute
in Session Description Protocol (SDP)", RFC 3605,
October 2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003.
[RFC3890] Westerlund, M., "A Transport Independent Bandwidth
Modifier for the Session Description Protocol (SDP)",
RFC 3890, September 2004.
[RFC4091] Camarillo, G. and J. Rosenberg, "The Alternative Network
Address Types (ANAT) Semantics for the Session Description
Protocol (SDP) Grouping Framework", RFC 4091, June 2005.
[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in
the Session Description Protocol (SDP)", RFC 4145,
September 2005.
[RFC4567] Arkko, J., Lindholm, F., Naslund, M., Norrman, K., and E.
Carrara, "Key Management Extensions for Session
Description Protocol (SDP) and Real Time Streaming
Protocol (RTSP)", RFC 4567, July 2006.
[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "S Description
Protocol (SDP) Security Descriptions for Media Streams",
RFC 4568, July 2006.
[RFC4570] Quinn, B. and R. Finlayson, "S Description Protocol (SDP)
Source Filters", RFC 4570, July 2006.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, July 2006.
[RFC4574] Levin, O. and G. Camarillo, "The Session Description
Protocol (SDP) Label Attribute", RFC 4574, August 2006.
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[RFC4583] Camarillo, G., "S Description Protocol (SDP) Format for
Binary Floor Control Protocol (BFCP) Streams", RFC 4583,
November 2006.
[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
"Extended RTP Profile for Real-time Transport Control
Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
July 2006.
[RFC4796] Hautakorpi, J. and G. Camarillo, "The Session Description
Protocol (SDP) Content Attribute", RFC 4796,
February 2007.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
Session Relay Protocol (MSRP)", RFC 4975, September 2007.
[RFC5104] Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
"Codec Control Messages in the RTP Audio-Visual Profile
with Feedback (AVPF)", RFC 5104, February 2008.
[RFC5109] Li, A., "RTP Payload Format for Generic Forward Error
Correction", RFC 5109, December 2007.
[RFC5159] Dondeti, L. and A. Jerichow, "S Description Protocol (SDP)
Attributes for Open Mobile Alliance (OMA) Broadcast
(BCAST) Service and Content Protection", RFC 5159,
March 2008.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245,
July 2006.
[RFC5285] Singer, D. and H. Desineni, "A General Mechanism for RTP
Header Extensions", RFC 5285, July 2008.
[RFC5432] Polk, J., Dhesikan, S., and G. Camarillo, "Quality of
Service (QoS) Mechanism Selection in the Session
Description Protocol (SDP)", RFC 5432, March 2009.
[RFC5506] Johansson, I., "Support for Reduced-Size Real-Time
Transport Control Protocol (RTCP): Opportunities and
Consequences", RFC 5506, April 2009.
[RFC5547] Garcia-Martin, M., Isomaki, M., Camarillo, G., Loreto, S.,
and P. Kyzivat, "A Session Description Protocol (SDP)
Offer/Answer Mechanism to Enable File Transfer", RFC 5547,
May 2009.
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[RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol
(SDP)", RFC 5576, June 2009.
[RFC5583] Schierl, T. and S. Wenger, "Signaling Media Decoding
Dependency in the Session Description Protocol (SDP)",
RFC 5583, July 2009.
[RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
Protocol (RTCP) Extensions for Single-Source Multicast
Sessions with Unicast Feedback", RFC 5760, February 2010.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761, April 2010.
[RFC5762] Perkins, C., "RTP and the Datagram Congestion Control
Protocol (DCCP)", RFC 5762, April 2010.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, May 2010.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
[RFC5939] Andreasen, F., "S Description Protocol (SDP) Capability
Negotiation", RFC 5939, September 2010.
[RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in
the Session Description Protocol", RFC 5956,
September 2010.
[RFC6064] Westerlund, M. and P. Frojdh, "SDP and RTSP Extensions
Defined for 3GPP Packet-Switched Streaming Service and
Multimedia Broadcast/Multicast Service", RFC 6064,
January 2011.
[RFC6128] Begen, A., "RTP Control Protocol (RTCP) Port for Source-
Specific Multicast (SSM) Sessions", RFC 6128,
February 2011.
[RFC6189] Zimmermann, P., Johnston, A., and J. Callas, "ZRTP: Media
Path Key Agreement for Unicast Secure RTP", RFC 6189,
April 2011.
[RFC6193] Saito, M., Wing, D., and M. Toyama, "Media Description for
the Internet Key Exchange Protocol (IKE) in the Session
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Description Protocol (SDP)", RFC 6193, April 2011.
[RFC6230] Boulton, C., Melanchuk, T., and S. McGlashan, "Media
Control Channel Framework", RFC 6230, May 2011.
[RFC6236] Johansson, I. and K. Jung, "Negotiation of Generic Image
Attributes in the Session Description Protocol (SDP)",
RFC 6236, May 2011.
[RFC6284] Begen, A., Wing, D., and T. Van Caenegem, "Port Mapping
between Unicast and Multicast RTP Sessions", RFC 6284,
June 2011.
[RFC6285] Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
"Unicast-Based Rapid Acquisition of Multicast RTP
Sessions", RFC 6285, June 2011.
[RFC6364] Begen, A., "S Description Protocol Elements for the
Forward Error Correction (FEC) Framework", RFC 6364,
October 2011.
[RFC6642] Wu, Q., Xia, F., and R. Even, "RTP Control Protocol (RTCP)
Extension for a Third-Party Loss Report", RFC 6642,
June 2012.
[RFC6679] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P.,
and K. Carlberg, "Explicit Congestion Notification (ECN)
for RTP over UDP", RFC 6679, August 2012.
[RFC6714] Holmberg, C., Blau, S., and E. Burger, "Connection
Establishment for Media Anchoring (CEMA) for the Message
Session Relay Protocol (MSRP)", RFC 6714, August 2012.
[RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
Datagram Congestion Control Protocol UDP Encapsulation for
NAT Traversal", RFC 6773, November 2012.
[RFC6787] Burnett, D. and S. Shanmugham, "Media Resource Control
Protocol Version 2 (MRCPv2)", RFC 6787, November 2012.
[RTCP-FB] "S Description Protocol (SDP) RTCP Feedback attributes", <
http://www.iana.org/assignments/sdp-parameters/
sdp-parameters.xml#sdp-parameters-14>.
[SSRC-GROUP]
"S Description Protocol (SDP) "ssrc-group" semantics", <ht
tp://www.iana.org/assignments/sdp-parameters/
sdp-parameters.xml#sdp-parameters-17>.
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[T.38] "Procedures for real-time Group 3 facsimile communication
over IP networks", <http://www.itu.int/rec/T-REC-T.38/e>.
Author's Address
Suhas Nandakumar
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: snandaku@cisco.com
Nandakumar Expires April 21, 2014 [Page 57]
