Re: [rtcweb] Minimal SDP negotiation mechanism
Harald Alvestrand <harald@alvestrand.no> Wed, 21 September 2011 06:59 UTC
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Date: Wed, 21 Sep 2011 09:02:08 +0200
From: Harald Alvestrand <harald@alvestrand.no>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Minimal SDP negotiation mechanism
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On 09/20/2011 10:08 PM, Cullen Jennings wrote: > I think this sounds about right to me - I have been thinking about a draft along the lines of this and showing how it maps to SIP. Keep in mind there are also cases where one sides sends an OFFER, gets an ANSWER, but that ANSWER has an error. Yes, I discussed this at our team yesterday - it seems to me that the offer/answer model only gives you 2 options here: - Send another OFFER and hope for a more appropriate ANSWER - Give up and signal that the connection is closed We don't have a message that fits in the SDP offer/answer model that allows you to inform the correspondent that the ANSWER was erroneous; this may argue that the PeerConnection needs to inform the Javascript layer and let that layer decide what to do. > I think another key component is that a signaling GW needs to pass along an opaque blob that gets passed back to it so you can signaling GW that are only transaction state full and don't have to retain state for the duration of the communications. Certainly desirable (for gateways that don't want to mess with blob internals). So far, it has seemed to us that the operation line + the SDP blob forms exactly that type of blob. > You also need some identifier information so that a JS application participating in multiple sessions can know what session a given piece of SDP goes with. When the message goes between JS and PeerConnection, there is such an identifier: The PeerConnection object itself. Do we need more? If the ID needs to be passed outside of the JS execution context, we need a globally unique identifier. But I'm not sure we need one all the time, and if a specific application needs it, it can generate one. > > On Sep 19, 2011, at 10:59 AM, Harald Alvestrand wrote: > >> I am looking at the WEBRTC API spec, which specifies a rudimentary negotiation framework: SDP objects prefixed by the string "SDP". >> >> It seems clear to me that this needs at least information about whether something is an offer or an answer, and some way to complete the transaction when an offer is sent and something prevents it from completing. >> Until we know we need more, what about the following, to be specified in the WEBRTC API? >> >> SDP objects are sent through the API, prefixed with either of >> >> SDP OFFER >> SDP ANSWER >> >> Alternatively, one can pass >> >> SDP ERROR >> >> to reply to an SDP OFFER when something goes wrong. >> >> If one gets an OFFER and sends out an ANSWER, state changes. >> If OFFER gets an ANSWER back, state changes. >> In all other cases, state is as before. >> >> We need to handle glare - when one sends an OFFER and gets back an OFFER, reply with SDP ERROR, enter a "glare" state, wait a bit, and send out an offer again. >> >> Do we really have to have anything else? >> >> >> >> >> _______________________________________________ >> rtcweb mailing list >> rtcweb@ietf.org >> https://www.ietf.org/mailman/listinfo/rtcweb >
- Re: [rtcweb] Minimal SDP negotiation mechanism Olle E. Johansson
- [rtcweb] Minimal SDP negotiation mechanism Harald Alvestrand
- Re: [rtcweb] Minimal SDP negotiation mechanism Paul Kyzivat
- Re: [rtcweb] Minimal SDP negotiation mechanism Hadriel Kaplan
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Olle E. Johansson
- Re: [rtcweb] Minimal SDP negotiation mechanism Christer Holmberg
- Re: [rtcweb] Minimal SDP negotiation mechanism Iñaki Baz Castillo
- Re: [rtcweb] Minimal SDP negotiation mechanism Harald Alvestrand
- Re: [rtcweb] Minimal SDP negotiation mechanism Christer Holmberg
- Re: [rtcweb] Minimal SDP negotiation mechanism Christer Holmberg
- Re: [rtcweb] Minimal SDP negotiation mechanism Harald Alvestrand
- Re: [rtcweb] Minimal SDP negotiation mechanism Olle E. Johansson
- Re: [rtcweb] Minimal SDP negotiation mechanism Christer Holmberg
- Re: [rtcweb] Minimal SDP negotiation mechanism Iñaki Baz Castillo
- Re: [rtcweb] Minimal SDP negotiation mechanism Magnus Westerlund
- Re: [rtcweb] Minimal SDP negotiation mechanism Roman Shpount
- Re: [rtcweb] Minimal SDP negotiation mechanism Olle E. Johansson
- Re: [rtcweb] Minimal SDP negotiation mechanism Cullen Jennings
- [rtcweb] Forking & Early Media - Was Re: Minimal … Cullen Jennings
- Re: [rtcweb] Minimal SDP negotiation mechanism Cullen Jennings
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Cullen Jennings
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Olle E. Johansson
- Re: [rtcweb] Minimal SDP negotiation mechanism Hadriel Kaplan
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Dzonatas Sol
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Hadriel Kaplan
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Hadriel Kaplan
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Ravindran Parthasarathi
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Roman Shpount
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Olle E. Johansson
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Ravindran Parthasarathi
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Saúl Ibarra Corretgé
- Re: [rtcweb] Minimal SDP negotiation mechanism Harald Alvestrand
- Re: [rtcweb] Forking & Early Media - Proposal Randell Jesup
- Re: [rtcweb] Forking & Early Media - Proposal Olle E. Johansson
- Re: [rtcweb] Minimal SDP negotiation mechanism Magnus Westerlund
- Re: [rtcweb] Minimal SDP negotiation mechanism Harald Alvestrand
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Muthu Arul Mozhi Perumal (mperumal)
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Roman Shpount
- Re: [rtcweb] Forking & Early Media - Proposal Roman Shpount
- Re: [rtcweb] Forking & Early Media - Proposal Randell Jesup
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Hadriel Kaplan
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Cullen Jennings
- [rtcweb] SIP Glare - Re: Minimal SDP negotiation … Cullen Jennings
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Tim Panton
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Hadriel Kaplan
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Roman Shpount
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Roman Shpount
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Magnus Westerlund
- Re: [rtcweb] Forking & Early Media - Proposal Elwell, John
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Harald Alvestrand
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Iñaki Baz Castillo
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Cullen Jennings
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Dzonatas Sol
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Matthew Kaufman
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Christer Holmberg
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Iñaki Baz Castillo
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Christer Holmberg
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Cullen Jennings
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Iñaki Baz Castillo
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Cullen Jennings
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Matthew Kaufman
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Christer Holmberg
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Cullen Jennings
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Hadriel Kaplan
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Roman Shpount
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Randell Jesup
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Christer Holmberg
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Christer Holmberg
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Hadriel Kaplan
- Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiat… Magnus Westerlund
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Harald Alvestrand
- Re: [rtcweb] Forking & Early Media - Was Re: Mini… Christer Holmberg