Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiation mechanism

Roman Shpount <roman@telurix.com> Thu, 22 September 2011 14:53 UTC

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Date: Thu, 22 Sep 2011 10:55:27 -0400
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From: Roman Shpount <roman@telurix.com>
To: Hadriel Kaplan <HKaplan@acmepacket.com>
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Subject: Re: [rtcweb] SIP Glare - Re: Minimal SDP negotiation mechanism
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If we are planning to support SIP, then standard way of dealing with glare
actually works fairly well. We would probably not get as much glare even
with SIP if we would not use re-INVITEs for keep alive messages (SIP session
timers). If we do not plan to support SIP, all we need is an ability in the
API to cancel an offer and leave glare resolution to signaling. In general
glare is unavoidable, for instance in case were both parties in the call
decide for some reason to switch the video on.
_____________
Roman Shpount


On Thu, Sep 22, 2011 at 10:40 AM, Hadriel Kaplan <HKaplan@acmepacket.com>wrote;wrote:

>
> On Sep 22, 2011, at 9:57 AM, Tim Panton wrote:
>
> > At the risk of showing my ignorance - why are we expecting glare to be a
> problem?
> > To my mind glare only happens when you have a locked resource e.g. a busy
> line
> > or number . Rtcweb does not contain either of those concepts, what's the
> resource
> > that is being competed for here ?
>
> The resource being competed for is SDP state/media info of the same
> session.  If both sides send a new SDP offer during the session at the same
> time, one side has to win.
>
> One would think this would be ultra-rare, but in SIP it happens a lot in
> some deployments.
>
> -hadriel
>
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