Re: [rtcweb] Multiplexing using the same port number for multiple media descritions
Christer Holmberg <christer.holmberg@ericsson.com> Tue, 30 August 2011 19:26 UTC
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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Justin Uberti <juberti@google.com>
Date: Tue, 30 Aug 2011 21:27:33 +0200
Thread-Topic: [rtcweb] Multiplexing using the same port number for multiple media descritions
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Multiplexing using the same port number for multiple media descritions
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Hi Justin, >I think Harald's approach is cleaner, since the fallback does not require a new offer. > >What do you see as problematic with Harald's suggestion? I have sent comments on Harald's draft, but my main issues are: 1. Unclear how to remove the m- line which is used for the multiplexed stream. (Maybe Harald has indicated somewhere how it would be done, and in that case I appologise for having missed it) 2. Intermediaries that do not understand the extension would still think that there are individual streams, and reserve resources etc accordingly. (Now, maybe there aren't such intermediaries in a web environment. But as CLUE very likely will also need some kind of a multiplex negotiation mechanism I would like to see something more general). Regards, Christer On Tue, Aug 30, 2011 at 7:21 AM, Christer Holmberg <christer.holmberg@ericsson.com<mailto:christer.holmberg@ericsson.com>> wrote: Hi, One possible alternative solution for SDP multiplex negotiation could be based on the assumption of using the same port number in multiple SDP m- lines (yes, I know SDP does not allow it, and I will come back to that). Something like: SDP offer: m=audio 10000 ... a=rtpmap ... a=rtpmap ... m=video 10000 ... a=rtpmap ... a=rtpmap ... SDP answer (multiplex supported/accepted): m=audio 20000 ... a=rtpmap ... a=rtpmap ... m=video 20000 ... a=rtpmap ... a=rtpmap ... SDP answer (multiplex not-supported/rejected): m=audio 20000 ... a=rtpmap ... a=rtpmap ... m=video 30000 ... a=rtpmap ... a=rtpmap ... MAYBE there is also a need to use some kind of grouping, in which case it could look something like (borrowing some terminology from Harald): SDP offer: a=group:TOGETHER foo bar m=audio 10000 ... a=mid:foo a=rtpmap ... a=rtpmap ... m=video 10000 ... a=mid:bar a=rtpmap ... a=rtpmap ... SDP answer (multiplex supported/accepted): m=audio 20000 ... a=rtpmap ... a=rtpmap ... a=mid:foo m=video 20000 ... a=mid:bar a=rtpmap ... a=rtpmap ... SDP answer (multiplex not-supported/rejected): m=audio 20000 ... a=rtpmap ... a=rtpmap ... m=video 30000 ... a=rtpmap ... a=rtpmap ... An ISSUE with this solution is of course that SDP does not allow for it. However, we could always say that browsers must support it, in which case it should work fine in direct browser-to-browser cases. When interworking with legacy, I guess two things can happen: 1. The offer is acctepted, with different port number in the answer, and multiplex won't be used (see example above) 2. The offer is rejected. In this case, the fallback would be that the browser sends a new offer, with different port numbers, and multiplex won't be used. Regards, Christer _______________________________________________ rtcweb mailing list rtcweb@ietf.org<mailto:rtcweb@ietf.org> https://www.ietf.org/mailman/listinfo/rtcweb
- [rtcweb] Multiplexing using the same port number … Christer Holmberg
- Re: [rtcweb] Multiplexing using the same port num… Justin Uberti
- Re: [rtcweb] Multiplexing using the same port num… Harald Alvestrand
- Re: [rtcweb] Multiplexing using the same port num… Christer Holmberg
- Re: [rtcweb] Multiplexing using the same port num… Christer Holmberg
- Re: [rtcweb] Multiplexing using the same port num… Magnus Westerlund
- Re: [rtcweb] Multiplexing using the same port num… Christer Holmberg
- Re: [rtcweb] Multiplexing using the same port num… Harald Alvestrand
- Re: [rtcweb] Multiplexing using the same port num… Christer Holmberg