Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiation mechanism
Matthew Kaufman <matthew.kaufman@skype.net> Thu, 22 September 2011 19:31 UTC
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Date: Thu, 22 Sep 2011 12:33:49 -0700
From: Matthew Kaufman <matthew.kaufman@skype.net>
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To: Cullen Jennings <fluffy@cisco.com>
References: <4E777500.5030201@alvestrand.no> <4E78940C.4040405@ericsson.com> <ED2DB00E-A64B-405F-96AC-2269258F6FFC@cisco.com> <4E799ECC.8030306@ericsson.com> <DB6B2796-9762-47CA-9A45-62476146DF04@cisco.com> <57CCCB06-F4C3-4E23-AF09-B7B5285C5FAE@phonefromhere.com> <F7758EE8-9D36-4999-86E4-21DB1E6F217D@cisco.com>
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Cc: rtcweb@ietf.org
Subject: Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiation mechanism
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On 9/22/11 11:56 AM, Cullen Jennings wrote: > Tim, it happens a fair amount in our playing around with browser > deployments. You make my own arguments for me. > Imagine you and I both using browsers and have an audio call set up. Sounds great. And the web server has sent down some javascript that was able to query the capabilities and so it knows which audio and video codecs are supported at each end, even before the audio call started. > We are talking an I say "hey, lets, add video", then we both go and > push our "enable video" buttons at roughly the same time. Also good. > In this case we often get glare. You shouldn't. Each side is asking the server to tell the other end to start sending video, and the server knows what codecs and parameters will work, so there's no overlap at all. > Part of the reasons is that the signaling path is not really fast as > it involves waiting for web servers to deal with sending notifications > down to other side. It's hard to guess what the signaling delay will > be but it easy to imagine that it will be over 200 ms in many cases > and pretty easy to imagine that both of use would would click the add > video button within 1/4 of second of each other. The glare we are > talking about here is any time browser A has sent an SDP offer to the > other side, but before A has received an SDP answer, the other side > sends A and SDP offer. See, that's the problem. IF there are SDP offers and answers, they shouldn't be tied to the peer connection object, they should be tied to the objects that represent the devices... that way you would have two separate offer/answer happening, one for each direction. And if you *weren't* using offer/answer, but had instead collected the capabilities ahead of time, then the server could just immediately tell each end to start sending. So instead of a 200 msec delay *and* the risk of glare, you'd have zero delay *and* zero chance of glare. Matthew Kaufman
- 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