Re: [rtcweb] Minimal SDP negotiation mechanism

Cullen Jennings <fluffy@cisco.com> Tue, 20 September 2011 19:56 UTC

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From: Cullen Jennings <fluffy@cisco.com>
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Date: Tue, 20 Sep 2011 13:58:28 -0600
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To: Magnus Westerlund <magnus.westerlund@ericsson.com>
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Subject: Re: [rtcweb] Minimal SDP negotiation mechanism
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On Sep 20, 2011, at 7:24 AM, Magnus Westerlund wrote:

> On 2011-09-19 18:59, Harald Alvestrand wrote:
> 
>> 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.
>> 
> 
> I think that is a bad design for glare handling. I agree it needs to be
> handled. I think the ICE version of glare handling could work pretty
> well here. Any offer needs to include a random 32 bit number. If the
> end-point receive an offer in relation to a peer-connection while it has
> an outstanding offer then it compares these codes. Who ever has the
> greatest numerical value wins and that offer is handled the other is
> responded with an error stating GLARE. Thus there is no extra delay and
> more clear resolution of the glare case.
> 
> Cheers
> 
> Magnus Westerlund

I think it has to be possible to gateway what happens here to what happens in SIP with glare - I suspect that more or less puts us on using the SIP glare mechanism.