WebRTC MediaStream Identification in the Session Description Protocol
draft-ietf-mmusic-msid-12
The information below is for an old version of the document.
Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8830.
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Author | Harald T. Alvestrand | ||
Last updated | 2016-03-18 | ||
Replaces | draft-alvestrand-mmusic-msid | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
Formats | |||
Reviews |
GENART Last Call review
(of
-13)
by Matthew Miller
Ready w/nits
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Additional resources | Mailing list discussion | ||
Stream | WG state | WG Consensus: Waiting for Write-Up | |
Document shepherd | Flemming Andreasen | ||
IESG | IESG state | Became RFC 8830 (Proposed Standard) | |
Consensus boilerplate | Unknown | ||
Telechat date | (None) | ||
Responsible AD | (None) | ||
Send notices to | (None) |
draft-ietf-mmusic-msid-12
", draft-ietf-rtcweb-jsep-08 (work in progress), October 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. [W3C.WD-webrtc-20150210] Bergkvist, A., Burnett, D., Jennings, C., and A. Narayanan, "WebRTC 1.0: Real-time Communication Between Browsers", World Wide Web Consortium WD WD- webrtc-20150210, February 2015, <http://www.w3.org/TR/2015/WD-webrtc-20150210>. Alvestrand Expires September 19, 2016 [Page 11] Internet-Draft MSID in SDP March 2016 7.2. Informative References [I-D.ietf-mmusic-sdp-bundle-negotiation] Holmberg, C., Alvestrand, H., and C. Jennings, "Negotiating Media Multiplexing Using the Session Description Protocol (SDP)", draft-ietf-mmusic-sdp-bundle- negotiation-07 (work in progress), April 2014. [I-D.ietf-rtcweb-overview] Alvestrand, H., "Overview: Real Time Protocols for Browser-based Applications", draft-ietf-rtcweb-overview-13 (work in progress), November 2014. [RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and Control Packets on a Single Port", RFC 5761, April 2010. [RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description Protocol (SDP) Grouping Framework", RFC 5888, June 2010. Appendix A. Design considerations, rejected alternatives One suggested mechanism has been to use CNAME instead of a new attribute. This was abandoned because CNAME identifies a synchronization context; one can imagine both wanting to have tracks from the same synchronization context in multiple MediaStreams and wanting to have tracks from multiple synchronization contexts within one MediaStream (but the latter is impossible, since a MediaStream is defined to impose synchronization on its members). Another suggestion has been to put the msid value within an attribute of RTCP SR (sender report) packets. This doesn't offer the ability to know that you have seen all the tracks currently configured for a media stream. A suggestion that survived for a number of drafts was to define "msid" as a generic mechanism, where the particular semantics of this usage of the mechanism would be defined by an "a=wms-semantic" attribute. This was removed in April 2015. Appendix B. Change log This appendix should be deleted before publication as an RFC. B.1. Changes from alvestrand-rtcweb-msid-00 to -01 Added track identifier. Alvestrand Expires September 19, 2016 [Page 12] Internet-Draft MSID in SDP March 2016 Added inclusion-by-reference of draft-lennox-mmusic-source-selection for track muting. Some rewording. B.2. Changes from alvestrand-rtcweb-msid-01 to -02 Split document into sections describing a generic grouping mechanism and sections describing the application of this grouping mechanism to the WebRTC MediaStream concept. Removed the mechanism for muting tracks, since this is not central to the MSID mechanism. B.3. Changes from alvestrand-rtcweb-msid-02 to mmusic-msid-00 Changed the draft name according to the wishes of the MMUSIC group chairs. Added text indicting cases where it's appropriate to have the same appdata for multiple SSRCs. Minor textual updates. B.4. Changes from alvestrand-mmusic-msid-00 to -01 Increased the amount of explanatory text, much based on a review by Miguel Garcia. Removed references to BUNDLE, since that spec is under active discussion. Removed distinguished values of the MSID identifier. B.5. Changes from alvestrand-mmusic-msid-01 to -02 Changed the order of the "msid-semantic: " attribute's value fields and allowed multiple identifiers. This makes the attribute useful as a marker for "I understand this semantic". Changed the syntax for "identifier" and "appdata" to be "token". Changed the registry for the "msid-semantic" attribute values to be a new registry, based on advice given in Atlanta. Alvestrand Expires September 19, 2016 [Page 13] Internet-Draft MSID in SDP March 2016 B.6. Changes from alvestrand-mmusic-msid-02 to ietf-mmusic-00 Updated terminology to refer to m-lines rather than RTP sessions when discussing SDP formats and the ability of other linking mechanisms to refer to SSRCs. Changed the "default" mechanism to return independent streams after considering the synchronization problem. Removed the space from between "msid-semantic" and its value, to be consistent with RFC 5576. B.7. Changes from mmusic-msid-00 to -01 Reworked msid mechanism to be a per-m-line attribute, to align with draft-roach-mmusic-unified-plan. B.8. Changes from mmusic-msid-01 to -02 Corrected several missed cases where the word "ssrc" was not changed to "M-line". Added pointer to unified-plan (which should be moved to point to -jsep) Removed suggestion that ssrc-group attributes can be used with "msid- semantic", it is now only the msid-semantic registry. B.9. Changes from mmusic-msid-02 to -03 Corrected even more cases where the word "ssrc" was not changed to "M-line". Added the functionality of using an asterisk (*) in the msid-semantic line, in order to remove the need for listing all msids in the msid- semantic line whne only one msid-semantic is in use. Removed some now-unnecessary text. B.10. Changes from mmusic-msid-03 to -04 Changed title to reflect focus on WebRTC MediaStreams Added a section on receiver-side media stream control, using the "msid-control" attribute. Alvestrand Expires September 19, 2016 [Page 14] Internet-Draft MSID in SDP March 2016 B.11. Changes from -04 to -05 Removed the msid-control section after WG discussion. Removed some text that seemed only to pertain to resolved issues. B.12. Changes from -05 to -06 Addressed issues found in Fleming Andreassen's review Referenced JSEP rather than unified-plan for the M-line mapping model Relaxed MSID definition to allow "token-char" in values rather than a-z 0-9 hyphen; tightened ABNF by adding length description to it. Deleted discussion of abandoned alternatives, as part of preparing for publication. Added a "detailed procedures" section to the WMS semantics description. Added IANA registration of the "msid-semantic" attribute. B.13. Changes from -06 to -07 Changed terminology from referring to "WebRTC device" to referring to "entities that implement the WMS semantic". Changed names for ABNF constructions based on a proposal by Paul Kyzivat. Included a section on generic offer/answer semantics. B.14. Changes from -07 to -08 Removed Appendix B that described the (now obsolete) ssrc-specific usage of MSID. Adopted a restructuring of the IANA section based on a suggestion from Martin Thomson. A number of text and ABNF clarifications based on suggestions from Ted Hardie, Paul Kyzivat and Adam Roach. Changed the "non-signalled track handling" to create a single stream with multiple tracks again, according to discussions at TPAC in November 2014 Alvestrand Expires September 19, 2016 [Page 15] Internet-Draft MSID in SDP March 2016 B.15. Changes from -08 to -09 Removed "wms-semantic" and all mention of multiple semantics for msid, as agreed at the Dallas IETF, March 2015. Addressed a number of review comments from Fleming Andresen and others. Changed the term "m-line" to "media description", since that is the term used in RFC 4566. Tried to make sure this document does not describe the API to the application. B.16. Changes from -09 to -10 Addressed review comments from Paul Kyzivat. B.17. Changes from -10 to -11 Defined the semantics of multiple MSIDs in a media section to be a MediaStreamTrack present in multiple MediaStreams. Made an explicit note that MediaStreamTracks are unidirectional. Disallowed the option of sending multiple media sections with the same msid (id and appdata identical). B.18. Changes from -11 to -12 Added mux-category to the IANA considerations section. Author's Address Harald Alvestrand Google Kungsbron 2 Stockholm 11122 Sweden Email: harald@alvestrand.no Alvestrand Expires September 19, 2016 [Page 16]