Re: [rtcweb] RE : I-D Action: draft-ietf-rtcweb-data-channel-04.txt
Randell Jesup <randell-ietf@jesup.org> Tue, 12 March 2013 08:00 UTC
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Subject: Re: [rtcweb] RE : I-D Action: draft-ietf-rtcweb-data-channel-04.txt
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On 3/11/2013 5:20 PM, MARCON, JEROME (JEROME) wrote: > > > Assuming that some day a spec defines the transport of T.140 (or > whatever similar protocol) over RTCWeb data channels > > - with a registered subprotocol > > - with multiple reliability options supported > > - requiring some new data channel properties > > - of which some are assymetric between the endpoints (like the > "characters per second" defined in [RFC4103]. > > > > Then (in the current version of your proposal) it seems to me that > > * Because current DATA_CHANNEL_OPEN syntax is not extensible: > > - it is not possible to carry these new properties in DATA_CHANNEL_OPEN > Why is it not extensible? We have a message type and you could simply > define another message... > > [JM1]. Mmh, then the spec defining T.140 (or whatever) over data > channels (and willing to add a new property like "cps") would have to > define a new message type - and more less its own DATA_CHANNEL_OPEN > structure? That's a costly extensibility. It you need to do a more complex negotiation, you have several choices. One would be: Open a reliable data channel for negotiation (0 RTT) (flagged by label & protocol). Over that channel, immediately send a message that sets up an offer for T.140 (take your pick on format. A JS app would likely use JSON), with a channel which was preset with the appropriate options ("I expect to receive data on this channel with these options"). The answerer can send back the response (on the negotiation channel), and also say "I expect data on this channel with these options"). At this point, the T.140 channel is open, and as soon as the response is received by the offerer, both sides know it. If this sounds very much like "fast-path re-negotiation" for JSEP, it is. Once you have DataChannels, you can leverage them to do a lot of things. This sort of sequence is enabled by the ability added to allow external negotiation. This is as fast as any other mechanism (and faster than any that goes via a signaling server) - 3 messages, 1 RTT total. (Open, Offer -> Answer) You can do this in SDP if you wish (and are willing to parse SDP, or whatever limited SDP you need). As mentioned, I normally would suggest JSON or something like that for JS Apps.) You can also do external negotiation over whatever channel and method you like. -- Randell Jesup randell-ietf@jesup.org
- [rtcweb] I-D Action: draft-ietf-rtcweb-data-chann… internet-drafts
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… MARCON, JEROME (JEROME)
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Michael Tuexen
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Randell Jesup
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Peter Thatcher
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Salvatore Loreto
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… MARCON, JEROME (JEROME)
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… MARCON, JEROME (JEROME)
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Salvatore Loreto
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… MARCON, JEROME (JEROME)
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Salvatore Loreto
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Michael Tuexen
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… MARCON, JEROME (JEROME)
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Randell Jesup
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Randell Jesup
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Michael Tuexen
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Michael Tuexen
- [rtcweb] RE : I-D Action: draft-ietf-rtcweb-data-… MARCON, JEROME (JEROME)
- Re: [rtcweb] RE : I-D Action: draft-ietf-rtcweb-d… Harald Alvestrand
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Michael Tuexen
- [rtcweb] RE : I-D Action: draft-ietf-rtcweb-data-… MARCON, JEROME (JEROME)
- [rtcweb] RE : RE : I-D Action: draft-ietf-rtcweb-… MARCON, JEROME (JEROME)
- Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-c… Michael Tuexen
- Re: [rtcweb] RE : I-D Action: draft-ietf-rtcweb-d… Randell Jesup