draft-ietf-mmusic-msid-15.txt   draft-ietf-mmusic-msid-16.txt 
Network Working Group H. Alvestrand Network Working Group H. Alvestrand
Internet-Draft Google Internet-Draft Google
Intended status: Standards Track July 7, 2016 Intended status: Standards Track February 7, 2017
Expires: January 8, 2017 Expires: August 11, 2017
WebRTC MediaStream Identification in the Session Description Protocol WebRTC MediaStream Identification in the Session Description Protocol
draft-ietf-mmusic-msid-15 draft-ietf-mmusic-msid-16
Abstract Abstract
This document specifies a Session Description Protocol (SDP) Grouping This document specifies a Session Description Protocol (SDP) Grouping
mechanism for RTP media streams that can be used to specify relations mechanism for RTP media streams that can be used to specify relations
between media streams. between media streams.
This mechanism is used to signal the association between the SDP This mechanism is used to signal the association between the SDP
concept of "media description" and the WebRTC concept of concept of "media description" and the WebRTC concept of
"MediaStream" / "MediaStreamTrack" using SDP signaling. "MediaStream" / "MediaStreamTrack" using SDP signaling.
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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 January 8, 2017. This Internet-Draft will expire on August 11, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Structure Of This Document . . . . . . . . . . . . . . . 3 1.2. Structure Of This Document . . . . . . . . . . . . . . . 3
1.3. Why A New Mechanism Is Needed . . . . . . . . . . . . . . 4 1.3. Why A New Mechanism Is Needed . . . . . . . . . . . . . . 4
1.4. The WEBRTC MediaStream . . . . . . . . . . . . . . . . . 4 1.4. The WEBRTC MediaStream . . . . . . . . . . . . . . . . . 4
2. The Msid Mechanism . . . . . . . . . . . . . . . . . . . . . 5 2. The Msid Mechanism . . . . . . . . . . . . . . . . . . . . . 5
3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Handling of non-signalled tracks . . . . . . . . . . . . 7 3.1. Handling of non-signalled tracks . . . . . . . . . . . . 7
3.2. Detailed Offer/Answer Procedures . . . . . . . . . . . . 8 3.2. Detailed Offer/Answer Procedures . . . . . . . . . . . . 8
3.2.1. Generating the initial offer . . . . . . . . . . . . 8 3.2.1. Generating the initial offer . . . . . . . . . . . . 9
3.2.2. Answerer processing of the Offer . . . . . . . . . . 9 3.2.2. Answerer processing of the Offer . . . . . . . . . . 9
3.2.3. Generating the answer . . . . . . . . . . . . . . . . 9 3.2.3. Generating the answer . . . . . . . . . . . . . . . . 9
3.2.4. Offerer processing of the answer . . . . . . . . . . 9 3.2.4. Offerer processing of the answer . . . . . . . . . . 9
3.2.5. Modifying the session . . . . . . . . . . . . . . . . 9 3.2.5. Modifying the session . . . . . . . . . . . . . . . . 9
3.3. Example SDP description . . . . . . . . . . . . . . . . . 10 3.3. Example SDP description . . . . . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
4.1. Attribute registration in existing registries . . . . . . 10 4.1. Attribute registration in existing registries . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Normative References . . . . . . . . . . . . . . . . . . 11 7.1. Normative References . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Design considerations, rejected alternatives . . . . 13 Appendix A. Design considerations, rejected alternatives . . . . 13
Appendix B. Change log . . . . . . . . . . . . . . . . . . . . . 13 Appendix B. Change log . . . . . . . . . . . . . . . . . . . . . 14
B.1. Changes from alvestrand-rtcweb-msid-00 to -01 . . . . . . 13 B.1. Changes from alvestrand-rtcweb-msid-00 to -01 . . . . . . 14
B.2. Changes from alvestrand-rtcweb-msid-01 to -02 . . . . . . 14 B.2. Changes from alvestrand-rtcweb-msid-01 to -02 . . . . . . 14
B.3. Changes from alvestrand-rtcweb-msid-02 to mmusic-msid-00 14 B.3. Changes from alvestrand-rtcweb-msid-02 to mmusic-msid-00 14
B.4. Changes from alvestrand-mmusic-msid-00 to -01 . . . . . . 14 B.4. Changes from alvestrand-mmusic-msid-00 to -01 . . . . . . 14
B.5. Changes from alvestrand-mmusic-msid-01 to -02 . . . . . . 14 B.5. Changes from alvestrand-mmusic-msid-01 to -02 . . . . . . 14
B.6. Changes from alvestrand-mmusic-msid-02 to ietf-mmusic-00 14 B.6. Changes from alvestrand-mmusic-msid-02 to ietf-mmusic-00 15
B.7. Changes from mmusic-msid-00 to -01 . . . . . . . . . . . 15 B.7. Changes from mmusic-msid-00 to -01 . . . . . . . . . . . 15
B.8. Changes from mmusic-msid-01 to -02 . . . . . . . . . . . 15 B.8. Changes from mmusic-msid-01 to -02 . . . . . . . . . . . 15
B.9. Changes from mmusic-msid-02 to -03 . . . . . . . . . . . 15 B.9. Changes from mmusic-msid-02 to -03 . . . . . . . . . . . 15
B.10. Changes from mmusic-msid-03 to -04 . . . . . . . . . . . 15 B.10. Changes from mmusic-msid-03 to -04 . . . . . . . . . . . 16
B.11. Changes from -04 to -05 . . . . . . . . . . . . . . . . . 15 B.11. Changes from -04 to -05 . . . . . . . . . . . . . . . . . 16
B.12. Changes from -05 to -06 . . . . . . . . . . . . . . . . . 15 B.12. Changes from -05 to -06 . . . . . . . . . . . . . . . . . 16
B.13. Changes from -06 to -07 . . . . . . . . . . . . . . . . . 16 B.13. Changes from -06 to -07 . . . . . . . . . . . . . . . . . 16
B.14. Changes from -07 to -08 . . . . . . . . . . . . . . . . . 16 B.14. Changes from -07 to -08 . . . . . . . . . . . . . . . . . 16
B.15. Changes from -08 to -09 . . . . . . . . . . . . . . . . . 16 B.15. Changes from -08 to -09 . . . . . . . . . . . . . . . . . 17
B.16. Changes from -09 to -10 . . . . . . . . . . . . . . . . . 17 B.16. Changes from -09 to -10 . . . . . . . . . . . . . . . . . 17
B.17. Changes from -10 to -11 . . . . . . . . . . . . . . . . . 17 B.17. Changes from -10 to -11 . . . . . . . . . . . . . . . . . 17
B.18. Changes from -11 to -12 . . . . . . . . . . . . . . . . . 17 B.18. Changes from -11 to -12 . . . . . . . . . . . . . . . . . 17
B.19. Changes from -12 to -13 . . . . . . . . . . . . . . . . . 17 B.19. Changes from -12 to -13 . . . . . . . . . . . . . . . . . 17
B.20. Changes from -13 to -14 . . . . . . . . . . . . . . . . . 17 B.20. Changes from -13 to -14 . . . . . . . . . . . . . . . . . 17
B.21. Changes from -14 to -15 . . . . . . . . . . . . . . . . . 17 B.21. Changes from -14 to -15 . . . . . . . . . . . . . . . . . 18
B.22. Changes from -15 to -16 . . . . . . . . . . . . . . . . . 18
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
1.1. Terminology 1.1. Terminology
This document uses terminology from [I-D.ietf-rtcweb-overview]. In This document uses terminology from [I-D.ietf-rtcweb-overview]. In
addition, the following terms are used as described below: addition, the following terms are used as described below:
RTP stream Defined in [RFC7656] as a stream of RTP packets RTP stream Defined in [RFC7656] as a stream of RTP packets
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This section describes the procedures for associating media This section describes the procedures for associating media
descriptions representing MediaStreamTracks within MediaStreams as descriptions representing MediaStreamTracks within MediaStreams as
defined in [W3C.WD-webrtc-20160531]. defined in [W3C.WD-webrtc-20160531].
In the Javascript API described in that specification, each In the Javascript API described in that specification, each
MediaStream and MediaStreamTrack has an "id" attribute, which is a MediaStream and MediaStreamTrack has an "id" attribute, which is a
DOMString. DOMString.
The value of the "msid-id" field in the msid consists of the "id" The value of the "msid-id" field in the msid consists of the "id"
attribute of a MediaStream, as defined in the MediaStream's WebIDL attribute of a MediaStream, as defined in the MediaStream's WebIDL
specification. specification. The special value "-" indicates "no MediaStream".
The value of the "msid-appdata" field in the msid consists of the The value of the "msid-appdata" field in the msid consists of the
"id" attribute of a MediaStreamTrack, as defined in the "id" attribute of a MediaStreamTrack, as defined in the
MediaStreamTrack's WebIDL specification. MediaStreamTrack's WebIDL specification.
When an SDP session description is updated, a specific "msid-id" When an SDP session description is updated, a specific "msid-id"
value continues to refer to the same MediaStream, and a specific value continues to refer to the same MediaStream, and a specific
"msid-appdata" to the same MediaStreamTrack. There is no memory "msid-appdata" to the same MediaStreamTrack. There is no memory
apart from the currently valid SDP descriptions; if an msid apart from the currently valid SDP descriptions; if an msid
"identifier" value disappears from the SDP and appears in a later "identifier" value disappears from the SDP and appears in a later
negotiation, it will be taken to refer to a new MediaStream. negotiation, it will be taken to refer to a new MediaStream.
If the MSID attribute does not conform to the ABNF given here, it If the MSID attribute does not conform to the ABNF given here, it
SHOULD be ignored. SHOULD be ignored.
The following is a high level description of the rules for handling The following is a high level description of the rules for handling
SDP updates. Detailed procedures are in Section 3.2. SDP updates. Detailed procedures are in Section 3.2.
o When a new msid "identifier" value occurs in a session o When a new msid "identifier" value occurs in a session
description, the recipient can signal to its application that a description, and it is not "-", the recipient can signal to its
new MediaStream has been added. application that a new MediaStream has been added.
o When a session description is updated to have media descriptions o When a session description is updated to have media descriptions
with an msid "identifier" value, with one or more different with an msid "identifier" value, with one or more different
"appdata" values, the recipient can siggnal to its application "appdata" values, the recipient can signal to its application that
that new MediaStreamTracks have been added to the MediaStream. new MediaStreamTracks have been added, and which MediaStream it
This is done for each different msid "identifier" value. has been added to. This is done for each different msid
"identifier" value, including the special value "-", which
indicates that a MediaStreamTrack has been added with no
corresponding MediaStream.
o When a session description is updated to no longer list any msid o When a session description is updated to no longer list any msid
attribute on a specific media description, the recipient can attribute on a specific media description, the recipient can
signal to its application that the corresponding MediaStreamTrack signal to its application that the corresponding MediaStreamTrack
has ended. has ended.
In addition to signaling that the track is closed when its msid In addition to signaling that the track is ended when its msid
attribute disappears from the SDP, the track will also be signaled as attribute disappears from the SDP, the track will also be signaled as
being closed when all associated SSRCs have disappeared by the rules being ended when all associated SSRCs have disappeared by the rules
of [RFC3550] section 6.3.4 (BYE packet received) and 6.3.5 (timeout), of [RFC3550] section 6.3.4 (BYE packet received) and 6.3.5 (timeout),
or when the corresponding media description is disabled by setting or when the corresponding media description is disabled by setting
the port number to zero. Changing the direction of the media the port number to zero. Changing the direction of the media
description (by setting "sendonly", "recvonly" or "inactive" description (by setting "sendonly", "recvonly" or "inactive"
attributes) will not close the MediaStreamTrack. attributes) will not end the MediaStreamTrack.
The association between SSRCs and media descriptions is specified in The association between SSRCs and media descriptions is specified in
[I-D.ietf-rtcweb-jsep]. [I-D.ietf-rtcweb-jsep].
3.1. Handling of non-signalled tracks 3.1. Handling of non-signalled tracks
Entities that do not use msid will not send msid. This means that Entities that do not use msid will not send msid. This means that
there will be some incoming RTP packets that the recipient has no there will be some incoming RTP packets that the recipient has no
predefined MediaStream id value for. predefined MediaStream id value for.
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Martin Thomson, Ted Hardie, Adam Roach, Magnus Westerlund, Alissa Martin Thomson, Ted Hardie, Adam Roach, Magnus Westerlund, Alissa
Cooper, Sue Hares and Paul Kyzivat for their work in reviewing this Cooper, Sue Hares and Paul Kyzivat for their work in reviewing this
draft, with many specific language suggestions. draft, with many specific language suggestions.
7. References 7. References
7.1. Normative References 7.1. Normative References
[I-D.ietf-mmusic-sdp-mux-attributes] [I-D.ietf-mmusic-sdp-mux-attributes]
Nandakumar, S., "A Framework for SDP Attributes when Nandakumar, S., "A Framework for SDP Attributes when
Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-02 Multiplexing", draft-ietf-mmusic-sdp-mux-attributes-12
(work in progress), July 2014. (work in progress), January 2016.
[I-D.ietf-rtcweb-jsep] [I-D.ietf-rtcweb-jsep]
Uberti, J., Jennings, C., and E. Rescorla, "Javascript Uberti, J., Jennings, C., and E. Rescorla, "Javascript
Session Establishment Protocol", draft-ietf-rtcweb-jsep-07 Session Establishment Protocol", draft-ietf-rtcweb-jsep-14
(work in progress), July 2014. (work in progress), March 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, March 1997. Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003. Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <http://www.rfc-editor.org/info/rfc3550>.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
July 2006, <http://www.rfc-editor.org/info/rfc4566>.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/
RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[W3C.CR-mediacapture-streams-20160519] [W3C.CR-mediacapture-streams-20160519]
Burnett, D., Bergkvist, A., Jennings, C., Narayanan, A., Burnett, D., Bergkvist, A., Jennings, C., Narayanan, A.,
and B. Aboba, "Media Capture and Streams", World Wide Web and B. Aboba, "Media Capture and Streams", World Wide Web
Consortium CR CR-mediacapture-streams-20160519, May 2016, Consortium CR CR-mediacapture-streams-20160519, May 2016,
<http://www.w3.org/TR/2016/ <http://www.w3.org/TR/2016/
CR-mediacapture-streams-20160519>. CR-mediacapture-streams-20160519>.
[W3C.WD-webrtc-20160531] [W3C.WD-webrtc-20160531]
Wilson, C. and J. Kalliokoski, "WebRTC 1.0: Real-time Wilson, C. and J. Kalliokoski, "WebRTC 1.0: Real-time
Communication Between Browsers", World Wide Web Consortium Communication Between Browsers", World Wide Web Consortium
WD WD-webrtc-20160531, May 2016, WD WD-webrtc-20160531, May 2016,
<http://www.w3.org/TR/2016/WD-webrtc-20160531>. <http://www.w3.org/TR/2016/WD-webrtc-20160531>.
7.2. Informative References 7.2. Informative References
[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-07 (work in progress), April 2014. negotiation-29 (work in progress), April 2016.
[I-D.ietf-rtcweb-overview] [I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for Alvestrand, H., "Overview: Real Time Protocols for
Browser-based Applications", draft-ietf-rtcweb-overview-10 Browser-based Applications", draft-ietf-rtcweb-overview-15
(work in progress), June 2014. (work in progress), January 2016.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761, April 2010. Control Packets on a Single Port", RFC 5761, DOI 10.17487/
RFC5761, April 2010,
<http://www.rfc-editor.org/info/rfc5761>.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, June 2010. Protocol (SDP) Grouping Framework", RFC 5888, DOI
10.17487/RFC5888, June 2010,
<http://www.rfc-editor.org/info/rfc5888>.
[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>.
Appendix A. Design considerations, rejected alternatives Appendix A. Design considerations, rejected alternatives
One suggested mechanism has been to use CNAME instead of a new One suggested mechanism has been to use CNAME instead of a new
skipping to change at page 18, line 5 skipping to change at page 18, line 21
considerations section. considerations section.
Moved definition pointers for MediaStream and MediaStreamTrack to the Moved definition pointers for MediaStream and MediaStreamTrack to the
"mediacapture-streams" document. "mediacapture-streams" document.
Added note that syntactically invalid MSID fields SHOULD be ignored. Added note that syntactically invalid MSID fields SHOULD be ignored.
Various small changes based on review feedback during IESG Various small changes based on review feedback during IESG
processing. processing.
B.22. Changes from -15 to -16
Added the special "-" value that means "no MediaStream".
Changed instances of a MediaStreamTrack being "closed" to saying it's
"ended", in accordance with WebRTC terminology.
Author's Address Author's Address
Harald Alvestrand Harald Alvestrand
Google Google
Kungsbron 2 Kungsbron 2
Stockholm 11122 Stockholm 11122
Sweden Sweden
Email: harald@alvestrand.no Email: harald@alvestrand.no
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