draft-ietf-mmusic-rid-04.txt   draft-ietf-mmusic-rid-05.txt 
Network Working Group P. Thatcher Network Working Group P. Thatcher
Internet-Draft Google Internet-Draft Google
Updates: RFC4855 (if approved) M. Zanaty Updates: 4855 (if approved) M. Zanaty
Intended status: Standards Track S. Nandakumar Intended status: Standards Track S. Nandakumar
Expires: August 11, 2016 Cisco Systems Expires: September 26, 2016 Cisco Systems
B. Burman B. Burman
Ericsson Ericsson
A. Roach A. Roach
B. Campen B. Campen
Mozilla Mozilla
February 08, 2016 March 25, 2016
RTP Payload Format Constraints RTP Payload Format Constraints
draft-ietf-mmusic-rid-04 draft-ietf-mmusic-rid-05
Abstract Abstract
In this specification, we define a framework for identifying RTP In this specification, we define a framework for identifying RTP
Streams with the constraints on its payload format in the Session Streams with the constraints on its payload format in the Session
Description Protocol. This framework defines a new "rid" SDP Description Protocol. This framework defines a new "rid" SDP
attribute to: a) effectively identify the RID RTP Streams within a attribute to: a) effectively identify the RID RTP Streams within a
RTP Session, b) constrain their payload format parameters in a codec- RTP Session, b) constrain their payload format parameters in a codec-
agnostic way beyond what is provided with the regular Payload Types agnostic way beyond what is provided with the regular Payload Types
and c) enable unambiguous mapping between the RID RTP Streams to and c) enable unambiguous mapping between the RID RTP Streams to
skipping to change at page 1, line 48 skipping to change at page 1, line 48
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 11, 2016. This Internet-Draft will expire on September 26, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Key Words for Requirements . . . . . . . . . . . . . . . . . 5 3. Key Words for Requirements . . . . . . . . . . . . . . . . . 4
4. SDP "a=rid" Media Level Attribute . . . . . . . . . . . . . . 5 4. SDP "a=rid" Media Level Attribute . . . . . . . . . . . . . . 5
5. "a=rid" constraints . . . . . . . . . . . . . . . . . . . . . 6 5. "a=rid" constraints . . . . . . . . . . . . . . . . . . . . . 6
6. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 7 6. SDP Offer/Answer Procedures . . . . . . . . . . . . . . . . . 7
6.1. Generating the Initial SDP Offer . . . . . . . . . . . . 7 6.1. Generating the Initial SDP Offer . . . . . . . . . . . . 7
6.2. Answerer processing the SDP Offer . . . . . . . . . . . . 8 6.2. Answerer processing the SDP Offer . . . . . . . . . . . . 8
6.2.1. "a=rid"-unaware Answerer . . . . . . . . . . . . . . 8 6.2.1. "a=rid"-unaware Answerer . . . . . . . . . . . . . . 8
6.2.2. "a=rid"-aware Answerer . . . . . . . . . . . . . . . 9 6.2.2. "a=rid"-aware Answerer . . . . . . . . . . . . . . . 8
6.3. Generating the SDP Answer . . . . . . . . . . . . . . . . 9 6.3. Generating the SDP Answer . . . . . . . . . . . . . . . . 9
6.4. Offerer Processing of the SDP Answer . . . . . . . . . . 10 6.4. Offerer Processing of the SDP Answer . . . . . . . . . . 10
6.5. Modifying the Session . . . . . . . . . . . . . . . . . . 12 6.5. Modifying the Session . . . . . . . . . . . . . . . . . . 11
7. Use with Declarative SDP . . . . . . . . . . . . . . . . . . 12 7. Use with Declarative SDP . . . . . . . . . . . . . . . . . . 12
8. Interaction with Other Techniques . . . . . . . . . . . . . . 12 8. Interaction with Other Techniques . . . . . . . . . . . . . . 12
8.1. Interaction with VP8 Format Parameters . . . . . . . . . 13 8.1. Interaction with VP8 Format Parameters . . . . . . . . . 13
8.1.1. max-fr - Maximum Framerate . . . . . . . . . . . . . 13 8.1.1. max-fr - Maximum Framerate . . . . . . . . . . . . . 13
8.1.2. max-fs - Maximum Framesize, in VP8 Macroblocks . . . 13 8.1.2. max-fs - Maximum Framesize, in VP8 Macroblocks . . . 13
8.2. Interaction with H.264 Format Parameters . . . . . . . . 14 8.2. Interaction with H.264 Format Parameters . . . . . . . . 14
8.2.1. profile-level-id and max-recv-level - Negotiated Sub- 8.2.1. profile-level-id and max-recv-level - Negotiated Sub-
Profile . . . . . . . . . . . . . . . . . . . . . . . 15 Profile . . . . . . . . . . . . . . . . . . . . . . . 15
8.2.2. max-br / MaxBR - Maximum Video Bitrate . . . . . . . 15 8.2.2. max-br / MaxBR - Maximum Video Bitrate . . . . . . . 15
8.2.3. max-fs / MaxFS - Maximum Framesize, in H.264 8.2.3. max-fs / MaxFS - Maximum Framesize, in H.264
Macroblocks . . . . . . . . . . . . . . . . . . . . . 15 Macroblocks . . . . . . . . . . . . . . . . . . . . . 15
8.2.4. max-mbps / MaxMBPS - Maximum Macroblock Processing 8.2.4. max-mbps / MaxMBPS - Maximum Macroblock Processing
Rate . . . . . . . . . . . . . . . . . . . . . . . . 16 Rate . . . . . . . . . . . . . . . . . . . . . . . . 16
8.2.5. max-smbps - Maximum Decoded Picture Buffer . . . . . 16 8.2.5. max-smbps - Maximum Decoded Picture Buffer . . . . . 16
9. Format Parameters for Future Payloads . . . . . . . . . . . . 16 9. Format Parameters for Future Payloads . . . . . . . . . . . . 16
10. Formal Grammar . . . . . . . . . . . . . . . . . . . . . . . 16 10. Formal Grammar . . . . . . . . . . . . . . . . . . . . . . . 16
11. SDP Examples . . . . . . . . . . . . . . . . . . . . . . . . 18 11. SDP Examples . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Many Bundled Streams using Many Codecs . . . . . . . . . 18 11.1. Many Bundled Streams using Many Codecs . . . . . . . . . 18
11.2. Scalable Layers . . . . . . . . . . . . . . . . . . . . 19 11.2. Scalable Layers . . . . . . . . . . . . . . . . . . . . 19
12. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 20 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
12.1. Declarative SDP . . . . . . . . . . . . . . . . . . . . 20 12.1. New SDP Media-Level attribute . . . . . . . . . . . . . 20
12.2. Definition of bitrate . . . . . . . . . . . . . . . . . 20 12.2. Registry for RID-Level Parameters . . . . . . . . . . . 20
12.3. Escaping new constraint values . . . . . . . . . . . . . 21 13. Security Considerations . . . . . . . . . . . . . . . . . . . 21
12.4. Utility of max-width and max height . . . . . . . . . . 21 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
12.5. Definition of max-fps . . . . . . . . . . . . . . . . . 21 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 15.1. Normative References . . . . . . . . . . . . . . . . . . 22
13.1. New SDP Media-Level attribute . . . . . . . . . . . . . 22 15.2. Informative References . . . . . . . . . . . . . . . . . 23
13.2. Registry for RID-Level Parameters . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
14. Security Considerations . . . . . . . . . . . . . . . . . . . 23
15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23
16. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
16.1. Normative References . . . . . . . . . . . . . . . . . . 24
16.2. Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
1. Terminology 1. Terminology
The terms "Source RTP Stream", "Endpoint", "RTP Session", and "RTP The terms "Source RTP Stream", "Endpoint", "RTP Session", and "RTP
Stream" are used as defined in [RFC7656]. Stream" are used as defined in [RFC7656].
The term "RID RTP Stream" is used as defined in The term "RID RTP Stream" is used as defined in
[I-D.roach-avtext-rid]. [I-D.roach-avtext-rid].
[RFC4566] and [RFC3264] terminology is also used where appropriate. [RFC4566] and [RFC3264] terminology is also used where appropriate.
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"rid-identifier" MUST NOT be repeated in a given media description "rid-identifier" MUST NOT be repeated in a given media description
("m=" section). ("m=" section).
The "a=rid" media attribute MAY be used for any RTP-based media The "a=rid" media attribute MAY be used for any RTP-based media
transport. It is not defined for other transports, although other transport. It is not defined for other transports, although other
documents may extend its semantics for such transports. documents may extend its semantics for such transports.
Though the constraints specified by the "rid" constraints follow a Though the constraints specified by the "rid" constraints follow a
syntax similar to session-level and media-level parameters, they are syntax similar to session-level and media-level parameters, they are
defined independently. All "rid" constraints MUST be registered with defined independently. All "rid" constraints MUST be registered with
IANA, using the registry defined in Section 13. IANA, using the registry defined in Section 12.
Section 10 gives a formal Augmented Backus-Naur Form (ABNF) [RFC5234] Section 10 gives a formal Augmented Backus-Naur Form (ABNF) [RFC5234]
grammar for the "rid" attribute. The "a=rid" media attribute is not grammar for the "rid" attribute. The "a=rid" media attribute is not
dependent on charset. dependent on charset.
5. "a=rid" constraints 5. "a=rid" constraints
This section defines the "a=rid" constraints that can be used to This section defines the "a=rid" constraints that can be used to
restrict the RTP payload encoding format in a codec-agnostic way. restrict the RTP payload encoding format in a codec-agnostic way.
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o max-bpp, for maximum number of bits per pixel, calculated as an o max-bpp, for maximum number of bits per pixel, calculated as an
average of all samples of any given coded picture. This is average of all samples of any given coded picture. This is
expressed as a floating point value, with an allowed range of expressed as a floating point value, with an allowed range of
0.0001 to 48.0. 0.0001 to 48.0.
All the constraints are optional and are subject to negotiation based All the constraints are optional and are subject to negotiation based
on the SDP Offer/Answer rules described in Section 6. on the SDP Offer/Answer rules described in Section 6.
This list is intended to be an initial set of constraints. Future This list is intended to be an initial set of constraints. Future
documents may define additional constraints; see Section 13.2. While documents may define additional constraints; see Section 12.2. While
this document does not define constraints for audio codecs, there is this document does not define constraints for audio codecs, there is
no reason such constraints should be precluded from definition and no reason such constraints should be precluded from definition and
registration by other documents. registration by other documents.
Section 10 provides formal Augmented Backus-Naur Form(ABNF) [RFC5234] Section 10 provides formal Augmented Backus-Naur Form(ABNF) [RFC5234]
grammar for each of the "a=rid" constraints defined in this section. grammar for each of the "a=rid" constraints defined in this section.
6. SDP Offer/Answer Procedures 6. SDP Offer/Answer Procedures
This section describes the SDP Offer/Answer [RFC3264] procedures when This section describes the SDP Offer/Answer [RFC3264] procedures when
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constrain the stream beyond what is allowed by other mechanisms, then constrain the stream beyond what is allowed by other mechanisms, then
the offerer will ignore the corresponding "a=rid" line, as described the offerer will ignore the corresponding "a=rid" line, as described
in Section 6.4. in Section 6.4.
The following subsections demonstrate these interactions using The following subsections demonstrate these interactions using
commonly-used video codecs. These descriptions are illustrative of commonly-used video codecs. These descriptions are illustrative of
the interaction principles outlined above, and are not normative. the interaction principles outlined above, and are not normative.
8.1. Interaction with VP8 Format Parameters 8.1. Interaction with VP8 Format Parameters
[I-D.ietf-payload-vp8] defines two format parameters for the VP8 [RFC7741] defines two format parameters for the VP8 codec. Both
codec. Both correspond to constraints on receiver capabilities, and correspond to constraints on receiver capabilities, and never
never indicate sending constraints. indicate sending constraints.
8.1.1. max-fr - Maximum Framerate 8.1.1. max-fr - Maximum Framerate
The VP8 "max-fr" format parameter corresponds to the "max-fps" The VP8 "max-fr" format parameter corresponds to the "max-fps"
constraint defined in this specification. If an RTP sender is constraint defined in this specification. If an RTP sender is
generating a stream using a format defined with this format generating a stream using a format defined with this format
parameter, and the sending constraints defined via "a=rid" include a parameter, and the sending constraints defined via "a=rid" include a
"max-fps" parameter, then the sent stream is will conform to the "max-fps" parameter, then the sent stream is will conform to the
smaller of the two values. smaller of the two values.
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the number of pixels per macroblock (typically 256). If an RTP the number of pixels per macroblock (typically 256). If an RTP
sender is generating a stream using a format defined with this format sender is generating a stream using a format defined with this format
parameter, and the sending constraints defined via "a=rid" include a parameter, and the sending constraints defined via "a=rid" include a
"max-fs" parameter, then the sent stream will conform to the smaller "max-fs" parameter, then the sent stream will conform to the smaller
of the two values; that is, the number of pixels per frame will not of the two values; that is, the number of pixels per frame will not
exceed: exceed:
min(rid_max_fs, fmtp_max_fs * macroblock_size) min(rid_max_fs, fmtp_max_fs * macroblock_size)
This fmtp parameter also has bearing on the max-height and max-width This fmtp parameter also has bearing on the max-height and max-width
parameters. Section 6.1 of [I-D.ietf-payload-vp8] requires that the parameters. Section 6.1 of [RFC7741] requires that the width and
width and height of the frame in macroblocks are also required to be height of the frame in macroblocks are also required to be less than
less than int(sqrt(fmtp_max_fs * 8)). Accordingly, the maximum width int(sqrt(fmtp_max_fs * 8)). Accordingly, the maximum width of a
of a transmitted stream will be limited to: transmitted stream will be limited to:
min(rid_max_width, int(sqrt(fmtp_max_fs * 8)) * macroblock_width) min(rid_max_width, int(sqrt(fmtp_max_fs * 8)) * macroblock_width)
Similarly, the stream's height will be limited to: Similarly, the stream's height will be limited to:
min(rid_max_height, int(sqrt(fmtp_max_fs * 8)) * macroblock_height) min(rid_max_height, int(sqrt(fmtp_max_fs * 8)) * macroblock_height)
8.2. Interaction with H.264 Format Parameters 8.2. Interaction with H.264 Format Parameters
[RFC6184] defines format parameters for the H.264 video codec. The [RFC6184] defines format parameters for the H.264 video codec. The
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This section gives a formal Augmented Backus-Naur Form (ABNF) This section gives a formal Augmented Backus-Naur Form (ABNF)
[RFC5234] grammar for each of the new media and "a=rid" attributes [RFC5234] grammar for each of the new media and "a=rid" attributes
defined in this document. defined in this document.
rid-syntax = "a=rid:" rid-identifier SP rid-dir rid-syntax = "a=rid:" rid-identifier SP rid-dir
[ rid-pt-param-list / rid-param-list ] [ rid-pt-param-list / rid-param-list ]
rid-identifier = 1*(alpha-numeric / "-" / "_") rid-identifier = 1*(alpha-numeric / "-" / "_")
rid-dir = "send" / "recv" rid-dir = "send" / "recv"
rid-pt-param-list = SP rid-fmt-list *(";" rid-param)
rid-pt-param-list = SP rid-fmt-list *(";" rid-param)
rid-param-list = SP rid-param *(";" rid-param) rid-param-list = SP rid-param *(";" rid-param)
rid-fmt-list = "pt=" fmt *( "," fmt ) rid-fmt-list = "pt=" fmt *( "," fmt )
; fmt defined in {{RFC4566}} ; fmt defined in {{RFC4566}}
rid-param = rid-width-param rid-param = rid-width-param
/ rid-height-param / rid-height-param
/ rid-fps-param / rid-fps-param
/ rid-fs-param / rid-fs-param
/ rid-br-param / rid-br-param
skipping to change at page 20, line 27 skipping to change at page 20, line 23
a=rid:0 send max-width=1280;max-height=720;max-fps=15 a=rid:0 send max-width=1280;max-height=720;max-fps=15
a=rid:1 send max-width=1280;max-height=720;max-fps=30;depend=0 a=rid:1 send max-width=1280;max-height=720;max-fps=30;depend=0
a=rid:2 recv max-width=1280;max-height=720;max-fps=30 a=rid:2 recv max-width=1280;max-height=720;max-fps=30
a=rid:5 send max-width=640;max-height=360;max-fps=15 a=rid:5 send max-width=640;max-height=360;max-fps=15
a=rid:6 send max-width=320;max-height=180;max-fps=15 a=rid:6 send max-width=320;max-height=180;max-fps=15
a=simulcast: send rid=0;1;5;6 recv rid=2 a=simulcast: send rid=0;1;5;6 recv rid=2
... ...
...same m=video sections as previous example for mid:v2-v7... ...same m=video sections as previous example for mid:v2-v7...
... ...
12. Open Issues 12. IANA Considerations
12.1. Declarative SDP
Section 7 describes the use of "a=rid" for declarative SDP. This is
a pretty small amount of work, and the use of this mechanism to
describe how a sender is going to constrain a stream does have some
amount of utility. Is the text sufficient? If not, do we want to
invest the work needed to make RID work with declarative use cases?
PROPOSAL: Keep the current text.
12.2. Definition of bitrate
Some questions have been raised as to whether we need a more formal
description of bitrate than we currently use.
If I read correctly, Magnus indicated that the definition in the
document is consistent with TIAS, and believes it is sufficiently
well defined.
PROPOSAL: keep current definition that exists in description of "max-
br".
12.3. Escaping new constraint values
The constraints on an "a=rid:" line are extensible. The syntax for
these is:
rid-param-other = 1*(alpha-numeric / "-") [ "=" param-val ]
param-val = *( %x20-58 / %x60-7E )
; Any printable character except semicolon
If an extension has values that can contain semicolons, they need an
escaping mechanism. Note that this is not an issue for any currently
defined constraints, as they all take numeric values only.
1. Change extension syntax to only allow numeric values
2. Define a universal escaping mechanism for all extensions to use
3. Leave this problem for the first extension constraints - if any -
to define value in a way that might allow a semicolon. Note that
this approach would allow the use of percent-style escaping
(e.g., "%3B") but not backslash-style escaping (e.g., "\;"), as
parsers that do not support the new constraint would interpret
the embedded semicolon as a separator.
PROPOSAL: Option #3
12.4. Utility of max-width and max height
Comment from Stephan Wenger: Are max-width and max-height actually
useful controls? Shouldn't max-fs be sufficient for any plausible
uses?
PROPOSAL: Keep max-height and max-width. Implementation is well-
defined and easily implemented. At least one participant expressed
support for these constraints at IETF 94 face-to-face meeting.
12.5. Definition of max-fps
Comment from Stephan Wenger: Would it be better to define max-fps as
constraining the average over a second rather than the inverse of the
smallest allowed interval between frames?
PROPOSAL: Keep as currently defined. The difference is subtle. The
only kinds of cases allowed by an average that aren't allowed by a
minimum interframe interval are those such as sending no packets for
most of a second, followed by a burst of 30 frames 1 ms apart, as
part of a stream constrained to 30 fps. Such cases seem undesirable.
13. IANA Considerations
This specification updates [RFC4855] to give additional guidance on This specification updates [RFC4855] to give additional guidance on
choice of Format Parameter (fmtp) names, and on their relation to RID choice of Format Parameter (fmtp) names, and on their relation to RID
constraints. constraints.
13.1. New SDP Media-Level attribute 12.1. New SDP Media-Level attribute
This document defines "rid" as SDP media-level attribute. This This document defines "rid" as SDP media-level attribute. This
attribute must be registered by IANA under "Session Description attribute must be registered by IANA under "Session Description
Protocol (SDP) Parameters" under "att-field (media level only)". Protocol (SDP) Parameters" under "att-field (media level only)".
The "rid" attribute is used to identify characteristics of RTP stream The "rid" attribute is used to identify characteristics of RTP stream
with in a RTP Session. Its format is defined in Section 10. with in a RTP Session. Its format is defined in Section 10.
13.2. Registry for RID-Level Parameters 12.2. Registry for RID-Level Parameters
This specification creates a new IANA registry named "att-field (rid This specification creates a new IANA registry named "att-field (rid
level)" within the SDP parameters registry. The "a=rid" constraints level)" within the SDP parameters registry. The "a=rid" constraints
MUST be registered with IANA and documented under the same rules as MUST be registered with IANA and documented under the same rules as
for SDP session-level and media-level attributes as specified in for SDP session-level and media-level attributes as specified in
[RFC4566]. [RFC4566].
Parameters for "a=rid" lines that modify the nature of encoded media Parameters for "a=rid" lines that modify the nature of encoded media
MUST be of the form that the result of applying the modification to MUST be of the form that the result of applying the modification to
the stream results in a stream that still complies with the other the stream results in a stream that still complies with the other
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max-bpp [RFCXXXX] max-bpp [RFCXXXX]
depend [RFCXXXX] depend [RFCXXXX]
It is conceivable that a future document wants to define a RID-level It is conceivable that a future document wants to define a RID-level
constraints that contain string values. These extensions need to constraints that contain string values. These extensions need to
take care to conform to the ABNF defined for rid-param-other. In take care to conform to the ABNF defined for rid-param-other. In
particular, this means that such extensions will need to define particular, this means that such extensions will need to define
escaping mechanisms if they want to allow semicolons, unprintable escaping mechanisms if they want to allow semicolons, unprintable
characters, or byte values greater than 127 in the string. characters, or byte values greater than 127 in the string.
14. Security Considerations 13. Security Considerations
As with most SDP parameters, a failure to provide integrity As with most SDP parameters, a failure to provide integrity
protection over the "a=rid" attributes provides attackers a way to protection over the "a=rid" attributes provides attackers a way to
modify the session in potentially unwanted ways. This could result modify the session in potentially unwanted ways. This could result
in an implementation sending greater amounts of data than a recipient in an implementation sending greater amounts of data than a recipient
wishes to receive. In general, however, since the "a=rid" attribute wishes to receive. In general, however, since the "a=rid" attribute
can only restrict a stream to be a subset of what is otherwise can only restrict a stream to be a subset of what is otherwise
allowable, modification of the value cannot result in a stream that allowable, modification of the value cannot result in a stream that
is of higher bandwidth than would be sent to an implementation that is of higher bandwidth than would be sent to an implementation that
does not support this mechanism. does not support this mechanism.
The actual identifiers used for RIDs are expected to be opaque. As The actual identifiers used for RIDs are expected to be opaque. As
such, they are not expected to contain information that would be such, they are not expected to contain information that would be
sensitive, were it observed by third-parties. sensitive, were it observed by third-parties.
15. Acknowledgements 14. Acknowledgements
Many thanks to review from Cullen Jennings, Magnus Westerlund, and Many thanks to review from Cullen Jennings, Magnus Westerlund, and
Paul Kyzivat. Thanks to Colin Perkins for input on future payload Paul Kyzivat. Thanks to Colin Perkins for input on future payload
type handing.. type handing..
16. References 15. References
16.1. Normative References 15.1. Normative References
[I-D.roach-avtext-rid] [I-D.roach-avtext-rid]
Roach, A., Nandakumar, S., and P. Thatcher, "RTP Stream Roach, A., Nandakumar, S., and P. Thatcher, "RTP Stream
Identifier (RID) Source Description (SDES)", draft-roach- Identifier (RID) Source Description (SDES)", draft-roach-
avtext-rid-02 (work in progress), February 2016. avtext-rid-02 (work in progress), February 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997, RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 24, line 42 skipping to change at page 23, line 10
[RFC4855] Casner, S., "Media Type Registration of RTP Payload [RFC4855] Casner, S., "Media Type Registration of RTP Payload
Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007, Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
<http://www.rfc-editor.org/info/rfc4855>. <http://www.rfc-editor.org/info/rfc4855>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/ Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
RFC5234, January 2008, RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>. <http://www.rfc-editor.org/info/rfc5234>.
16.2. Informative References 15.2. Informative References
[H264] ITU-T Recommendation H.264, "Advanced video coding for [H264] ITU-T Recommendation H.264, "Advanced video coding for
generic audiovisual services (V9)", February 2014, generic audiovisual services (V9)", February 2014,
<http://www.itu.int/rec/T-REC-H.264-201304-I>. <http://www.itu.int/rec/T-REC-H.264-201304-I>.
[I-D.ietf-mmusic-sdp-bundle-negotiation] [I-D.ietf-mmusic-sdp-bundle-negotiation]
Holmberg, C., Alvestrand, H., and C. Jennings, Holmberg, C., Alvestrand, H., and C. Jennings,
"Negotiating Media Multiplexing Using the Session "Negotiating Media Multiplexing Using the Session
Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle-
negotiation-25 (work in progress), January 2016. negotiation-27 (work in progress), February 2016.
[I-D.ietf-mmusic-sdp-simulcast] [I-D.ietf-mmusic-sdp-simulcast]
Burman, B., Westerlund, M., Nandakumar, S., and M. Zanaty, Burman, B., Westerlund, M., Nandakumar, S., and M. Zanaty,
"Using Simulcast in SDP and RTP Sessions", draft-ietf- "Using Simulcast in SDP and RTP Sessions", draft-ietf-
mmusic-sdp-simulcast-04 (work in progress), February 2016. mmusic-sdp-simulcast-04 (work in progress), February 2016.
[I-D.ietf-payload-vp8]
Westin, P., Lundin, H., Glover, M., Uberti, J., and F.
Galligan, "RTP Payload Format for VP8 Video", draft-ietf-
payload-vp8-17 (work in progress), September 2015.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <http://www.rfc-editor.org/info/rfc5226>.
[RFC6184] Wang, Y., Even, R., Kristensen, T., and R. Jesup, "RTP [RFC6184] Wang, Y., Even, R., Kristensen, T., and R. Jesup, "RTP
Payload Format for H.264 Video", RFC 6184, DOI 10.17487/ Payload Format for H.264 Video", RFC 6184, DOI 10.17487/
RFC6184, May 2011, RFC6184, May 2011,
<http://www.rfc-editor.org/info/rfc6184>. <http://www.rfc-editor.org/info/rfc6184>.
skipping to change at page 25, line 36 skipping to change at page 23, line 48
Attributes in the Session Description Protocol (SDP)", RFC Attributes in the Session Description Protocol (SDP)", RFC
6236, DOI 10.17487/RFC6236, May 2011, 6236, DOI 10.17487/RFC6236, May 2011,
<http://www.rfc-editor.org/info/rfc6236>. <http://www.rfc-editor.org/info/rfc6236>.
[RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and [RFC7656] Lennox, J., Gross, K., Nandakumar, S., Salgueiro, G., and
B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms B. Burman, Ed., "A Taxonomy of Semantics and Mechanisms
for Real-Time Transport Protocol (RTP) Sources", RFC 7656, for Real-Time Transport Protocol (RTP) Sources", RFC 7656,
DOI 10.17487/RFC7656, November 2015, DOI 10.17487/RFC7656, November 2015,
<http://www.rfc-editor.org/info/rfc7656>. <http://www.rfc-editor.org/info/rfc7656>.
[RFC7741] Westin, P., Lundin, H., Glover, M., Uberti, J., and F.
Galligan, "RTP Payload Format for VP8 Video", RFC 7741,
DOI 10.17487/RFC7741, March 2016,
<http://www.rfc-editor.org/info/rfc7741>.
Authors' Addresses Authors' Addresses
Peter Thatcher Peter Thatcher
Google Google
Email: pthatcher@google.com Email: pthatcher@google.com
Mo Zanaty Mo Zanaty
Cisco Systems Cisco Systems
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