Re: [rtcweb] Use of offer / answer semantics
Harald Alvestrand <harald@alvestrand.no> Thu, 08 September 2011 10:48 UTC
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Date: Thu, 08 Sep 2011 12:50:35 +0200
From: Harald Alvestrand <harald@alvestrand.no>
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To: Bernard Aboba <bernard_aboba@hotmail.com>
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Cc: rtcweb@ietf.org
Subject: Re: [rtcweb] Use of offer / answer semantics
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On 09/08/11 06:45, Bernard Aboba wrote: > > > > 1) The media negotiations will be done using the same SDP > offer/answer semantics that are used in SIP. > > To be precise - you're suggesting that we use RFC 3264 offer/answer > > semantics. (That RFC is 25 pages long. RFC 3261, the core SIP document, > > is 269 pages, and is NOT a normative reference from 3264. I am anxious > > to avoid having a normative dependency on 3261.) > > > > I agree with this. > > [BA] I do *not* agree that RTCWEB should have to support every aspect > of SDP offer/answer. Basic offer/answer, sure. All potential corner > cases? Not necessarily. If we start off from: - RFC 3264 assuming that we support all of it, and then list the parts we don't want - RFC 3261 assuming we support none of it, and list the parts we do want we might have a better dialogue (or at least a more precise one). > > > > 2) It will be possible to gateway between legacy SIP devices that > support ICE and appropriate RTP / SDP mechanisms and codecs without > using a media gateway. A signaling gateway to convert between the > signaling on the web side to the SIP signaling may be needed. > > > I agree with this - I think the "may be needed" will turn out to be > > "will be needed", but some portion of that gateway can be > implemented by > > Javascript running in the browser, if desirable. > > [BA] This seems like a good principle, but I'm not clear that it will > work with all use cases. For example, what happens in the E911 use > cases when an RTCWEB implementation attempts to make a call to a PSAP > implementing NENA i3 Stage 3? If you don't have a media gateway, then > the browser will need to implement one of the mandated codecs on the > PSAP side. So in those use cases, eliminating the media gateway > implies making G.711 and H.264 mandatory-to-implement. Unless RTCWEB mandtory codecs have some overlap with the NENA i3 Stage 3 codecs, you have given a good argument for why NENA i3 Stage 3 devices should not be in the list of "legacy SIP devices that support ICE and appropriate RTP / SDP mechanisms and codecs". I'm still hoping that some day, someone will show up with a serial number and software version for a device they definitely think should be in the "legacy SIP devices that support ICE and appropriate RTP / SDP mechanisms and codecs" category. > > > > 3) When a new codec is specified, and the SDP for the new codec is > specified in the MMUSIC WG, no other standardization would should be > required for it to be possible to use that in the web browsers. Adding > a new codecs which might have new SDP parameters should not change the > APIs between the browser and javascript application. As soon as the > browsers support the new codec, old applications written before the > codecs was specified should automatically be able to use the new codec > where appropriate with no changes to the JS applications. > > I agree with this (modulo spelling and WG name fixups). > > [BA] Agree with "no new standardization". But that doesn't mean that > applications will automatically "just work", right? That's a much > harder requirement. Nothing ever "just works"..... but simple cases should continue to work. > > > I decided that the fight against SDP was not worth fighting after > > listening to the dozens of WGs doing SDP extensions for various > > purposes, many of which might make sense to incorporate in a browser > > platform, and concluding that SDP wouldn't hold still enough for us to > > specify a gateway from/to it. > > [BA] Agree that it's not worth fighting, but making it clear what we > do and do not support will be a "fight" of sorts. That is, unless > you're willing to require that the browser be able to *everything* > enabled by RFC 3264. Personally, I don't think that is worthwhile. I think we agree. Let's get down to specifics (in another thread).
- [rtcweb] Use of offer / answer semantics Cullen Jennings
- Re: [rtcweb] Use of offer / answer semantics Colin Perkins
- Re: [rtcweb] Use of offer / answer semantics Matthew Kaufman
- Re: [rtcweb] Use of offer / answer semantics Emil Ivov
- Re: [rtcweb] Use of offer / answer semantics Emil Ivov
- Re: [rtcweb] Use of offer / answer semantics Colin Perkins
- Re: [rtcweb] Use of offer / answer semantics Emil Ivov
- Re: [rtcweb] Use of offer / answer semantics Cullen Jennings
- Re: [rtcweb] Use of offer / answer semantics Cullen Jennings
- Re: [rtcweb] Use of offer / answer semantics Cullen Jennings
- Re: [rtcweb] Use of offer / answer semantics Harald Alvestrand
- Re: [rtcweb] Use of offer / answer semantics Henry Sinnreich
- Re: [rtcweb] Use of offer / answer semantics Bernard Aboba
- Re: [rtcweb] Use of offer / answer semantics Tim Panton
- Re: [rtcweb] Use of offer / answer semantics Harald Alvestrand
- Re: [rtcweb] Use of offer / answer semantics Olle E. Johansson
- Re: [rtcweb] Use of offer / answer semantics Roman Shpount
- Re: [rtcweb] Use of offer / answer semantics Paul Kyzivat
- Re: [rtcweb] Use of offer / answer semantics Dzonatas Sol
- Re: [rtcweb] Use of offer / answer semantics Paul Kyzivat
- Re: [rtcweb] Use of offer / answer semantics Hadriel Kaplan
- Re: [rtcweb] Use of offer / answer semantics Olle E. Johansson
- [rtcweb] Supporting legacy PSTN interop (was: Use… Hadriel Kaplan
- Re: [rtcweb] Supporting legacy PSTN interop (was:… Ravindran Parthasarathi
- Re: [rtcweb] Use of offer / answer semantics Randell Jesup
- Re: [rtcweb] Use of offer / answer semantics Hadriel Kaplan