Re: [rtcweb] No Plan
Jonathan Lennox <jonathan@vidyo.com> Mon, 03 June 2013 22:07 UTC
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From: Jonathan Lennox <jonathan@vidyo.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>
Date: Mon, 03 Jun 2013 18:03:03 -0400
Thread-Topic: [rtcweb] No Plan
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] No Plan
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On Jun 3, 2013, at 4:40 PM, Paul Kyzivat <pkyzivat@alum.mit.edu> wrote: > +1 > > The more we dig into this the more it looks like Plan B. > > Thanks, > Paul I think No Plan and Plan B are largely isomorphic in a WebRTC context. The primary difference is that rather than using a=ssrc and a=receive-ssrc (and whatever other Plan B attributes would be needed) to control sources within an m-line, instead direct Javascript APIs are used for the same semantics. It's up to the application to communicate the relevant information end-to-end, in parallel to however it communicates the SDP blob. As I see it, the primary advantages of No Plan, then, are that: a) It allows "implicit" signaling of sources -- where that's sufficient -- by just sending RTP traffic. This prevents problems related to the timing and synchronization between signaling and media. (Note that Plan B probably actually needs this as well, for legacy interop.) b) It carves a Comment 22 corner out of the SDP-based APIs, thus decoupling source signaling from SDP offer/answer. This is for a scenario where there aren't any issues of legacy compatibility, and there isn't any (or at least much) existing IETF standardization -- as best I can recall, legacy compatibility and existing standardization were the primary motivations for using SDP as the WebRTC API. Other than that, I think the two proposals are pretty similar for WebRTC, and it would probably be a Simple Matter of Programming to translate between the two (though you have to worry about the O/A state on the Plan B side). In particular, if you have disaggregated media, you need multiple m-lines of the same type. The No Plan document's suggestion that you offer only one m-line of a given media type is guidance on how to avoid interop failures on initial offers to legacy devices, I think, not an essential aspect of the proposal. In a SIP context, No Plan requires defining a separate signaling channel for this source information, in scenarios where something beyond implicit signaling is needed. As Emil has stated, I think that something like the SIP/XCon conference package, or something like the CLUE channel, would be the obvious places to start. I think SIP, even more than RTCWeb, is where you'd want something lighter-weight and better-designed than SDP offer/answer to signal source changes. > On 6/1/13 7:05 AM, Christer Holmberg wrote: >> >> Hi, >> >>>> The draft says: >>>> >>>> "For the sake of interoperability this specification strongly advises >>>> against the use of multiple m= lines for a single media type." >>> >>> This should probably be clarified. The above referred mostly to a >>> browser's expectations and default offers. Multiple m= lines can confuse >>> a number of existing legacy endpoints which is why they should be >>> avoided when initiating a session that could reach a similar device (and >>> by default this should be assumed for any session). >>> >>> If applications *know* that they need to have multiple m= lines of a >>> given type they can request this the same way they could do it with Plan B: >>> >>> If the application wishes, it can request that a given >>> media source be placed onto a separate m= line, by setting a new >>> .content property on the desired MediaStreamTrack; the values for the >>> .content property are those defined for the a=content attribute in >>> [RFC4796]. >>> >>> I'll make sure this is part of the next version. >>> >>> Does this make sense? >> >> I have nothing against a general recommendation to, for a given media type, have as few m- lines as possible. >> >> But, I do think the draft need to point out that it is not always possible, e.g. because: >> >> 1) m- lines have different characteristics (normally indicated using SDP attributes) that does not "fit" all content for the given media type; >> 2) different protocols are used for different m- lines, even if the media type is the same; or >> 3) the remote endpoint only supports a single (or, another given number) of sources per m- line. >> >> Etc. >> >> Regards, >> >> Christer >> >> >> >> >> >>> My understanding is that the usage of multiple m= lines for a single media type would not affect the mechanism as such, but I just want to verify that :) >>> >>> Also, there ARE "legacy" implementations that use multiple m= lines for a single media type (e.g. video enabled devices using two video m= lines: one for camera content, and one for slides). >>> >>> So, while I definitely think that legacy interoperability shall be taken into consideration, I would not like to make such strong statements. In my opinion (the draft also talks about it), the usage of multiple simultaneous SSRCs per m- line is a much bigger issue when it comes to legacy interoperability. >>> >>> Also, in CLUE we have been working on signaling scenarios with multiple m= lines per media type. >>> >>> >>> Regards, >>> >>> Christer >>> >>> >>> >>> -----Original Message----- >>> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On Behalf Of Emil Ivov >>> Sent: 29. toukokuuta 2013 22:00 >>> To: rtcweb@ietf.org >>> Subject: [rtcweb] No Plan >>> >>> Hey all, >>> >>> Based on many of the discussions that we've had here, as well as many others that we've had offlist, it seemed like a good idea to investigate a negotiation alternative that relies on SDP and Offer/Answer just a little bit less. >>> >>> The following "no plan" draft attempts to present one such approach: >>> >>> http://tools.ietf.org/html/draft-ivov-rtcweb-noplan >>> >>> The draft relies on conventional use of SDP O/A but leaves the intricacies of multi-source scenarios to application-specific signalling, with potentially a little help from RTP. >>> >>> Hopefully, proponents of Plans A and B would find that the interoperability requirements that concerned them can still be met with "no plan". Of course they would have to be addressed by application-specific signalling and/or signalling gateways. >>> >>> Comments are welcome! >>> >>> Cheers, >>> Emil >>> >>> -- >>> https://jitsi.org >>> _______________________________________________ >>> rtcweb mailing list >>> rtcweb@ietf.org >>> https://www.ietf.org/mailman/listinfo/rtcweb >>> . >>> >> >> -- >> https://jitsi.org >> _______________________________________________ >> rtcweb mailing list >> rtcweb@ietf.org >> https://www.ietf.org/mailman/listinfo/rtcweb >> > > _______________________________________________ > rtcweb mailing list > rtcweb@ietf.org > https://www.ietf.org/mailman/listinfo/rtcweb > -- Jonathan Lennox jonathan@vidyo.com
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Bernard Aboba
- Re: [rtcweb] No Plan Sergio Garcia Murillo
- [rtcweb] No Plan - but what's the proposal Cullen Jennings
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan Richard Barnes
- Re: [rtcweb] No Plan Cullen Jennings
- Re: [rtcweb] No Plan Peter Saint-Andre
- Re: [rtcweb] No Plan Martin Thomson
- [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan Mary Barnes
- Re: [rtcweb] No Plan Peter Saint-Andre
- Re: [rtcweb] No Plan Christer Holmberg
- Re: [rtcweb] No Plan Stefan Håkansson LK
- Re: [rtcweb] No Plan Enrico Marocco
- Re: [rtcweb] No Plan Bernard Aboba
- Re: [rtcweb] No Plan Stefan Håkansson LK
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Enrico Marocco
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan - PT based MUX Cullen Jennings
- Re: [rtcweb] No Plan Gunnar Hellstrom
- Re: [rtcweb] No Plan Iñaki Baz Castillo
- Re: [rtcweb] No Plan Sergio Garcia Murillo
- Re: [rtcweb] No Plan Gunnar Hellstrom
- Re: [rtcweb] No Plan Sergio Garcia Murillo
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan Iñaki Baz Castillo
- Re: [rtcweb] No Plan Cullen Jennings (fluffy)
- Re: [rtcweb] No Plan Mark Rejhon
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan - but what's the proposal Emil Ivov
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Cullen Jennings (fluffy)
- [rtcweb] RTT (was Re: No Plan) Matthew Kaufman
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan Matthew Kaufman
- Re: [rtcweb] RTT (was Re: No Plan) Paul Kyzivat
- Re: [rtcweb] No Plan Stefan Håkansson LK
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] RTT (was Re: No Plan) Gunnar Hellstrom
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan Christer Holmberg
- Re: [rtcweb] No Plan Iñaki Baz Castillo
- Re: [rtcweb] No Plan Iñaki Baz Castillo
- Re: [rtcweb] RTT (was :No Plan ) Gunnar Hellstrom
- Re: [rtcweb] RTT (was :No Plan ) Iñaki Baz Castillo
- Re: [rtcweb] RTT (was :No Plan ) Barry Dingle
- Re: [rtcweb] RTT (was :No Plan ) Gunnar Hellstrom
- Re: [rtcweb] RTT (was :No Plan ) Iñaki Baz Castillo
- Re: [rtcweb] RTT (was :No Plan ) Iñaki Baz Castillo
- Re: [rtcweb] RTT (was :No Plan ) Gunnar Hellstrom
- Re: [rtcweb] RTT (was :No Plan ) Iñaki Baz Castillo
- [rtcweb] Translating Plan A into No Plan (Was: No… Emil Ivov
- Re: [rtcweb] Translating Plan A into No Plan (Was… Iñaki Baz Castillo
- Re: [rtcweb] Translating Plan A into No Plan (Was… Eric Rescorla
- Re: [rtcweb] No Plan - but what's the proposal Cullen Jennings
- Re: [rtcweb] No Plan - but what's the proposal Cullen Jennings
- Re: [rtcweb] No Plan - but what's the proposal Emil Ivov
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] Translating Plan A into No Plan (Was… Martin Thomson
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] RTT (was :No Plan ) Paul Kyzivat
- Re: [rtcweb] No Plan - but what's the proposal Iñaki Baz Castillo
- Re: [rtcweb] Translating Plan A into No Plan (Was… Paul Kyzivat
- Re: [rtcweb] No Plan Iñaki Baz Castillo
- Re: [rtcweb] Translating Plan A into No Plan (Was… Iñaki Baz Castillo
- Re: [rtcweb] Translating Plan A into No Plan (Was… Emil Ivov
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan - but what's the proposal Emil Ivov
- Re: [rtcweb] Translating Plan A into No Plan (Was… Paul Kyzivat
- Re: [rtcweb] No Plan Paul Kyzivat
- Re: [rtcweb] No Plan Jonathan Lennox
- Re: [rtcweb] No Plan Jim Barnett
- Re: [rtcweb] Translating Plan A into No Plan (Was… Roni Even
- Re: [rtcweb] No Plan Bernard Aboba
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] No Plan Christer Holmberg
- [rtcweb] Repair Flows and No Plan (Was: No Plan) Emil Ivov
- Re: [rtcweb] No Plan Emil Ivov
- Re: [rtcweb] RTT (was :No Plan ) BeckW
- Re: [rtcweb] RTT (was :No Plan ) Gunnar Hellstrom
- Re: [rtcweb] Repair Flows and No Plan (Was: No Pl… Sergio Garcia Murillo
- Re: [rtcweb] No Plan - but what's the proposal Cullen Jennings
- Re: [rtcweb] No Plan - but what's the proposal Emil Ivov
- Re: [rtcweb] No Plan - but what's the proposal Cullen Jennings
- Re: [rtcweb] No Plan - but what's the proposal Silvia Pfeiffer
- Re: [rtcweb] No Plan - but what's the proposal Emil Ivov
- [rtcweb] Plan xyz discussions; MMUSIC <> RTCweb R… Flemming Andreasen
- Re: [rtcweb] No Plan - but what's the proposal Cullen Jennings
- Re: [rtcweb] No Plan - but what's the proposal Cullen Jennings
- Re: [rtcweb] No Plan - but what's the proposal Peter Thatcher