Re: [MMUSIC] Trickle ICE for SIP Questions

Paul Kyzivat <> Tue, 09 July 2013 22:00 UTC

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Date: Tue, 09 Jul 2013 17:59:04 -0400
From: Paul Kyzivat <>
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Subject: Re: [MMUSIC] Trickle ICE for SIP Questions
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On 7/9/13 5:21 PM, Stach, Thomas wrote:
> Paul,
>> -----Original Message-----
>> From: Paul Kyzivat []
>> Sent: Monday, 08 July, 2013 18:05
>> To: Stach, Thomas
>> Cc:
>> Subject: Re: [MMUSIC] Trickle ICE for SIP Questions
>> Just responding to things that haven't already been covered.
>> On 7/8/13 5:44 AM, Stach, Thomas wrote:
>>>> Yes, why is it such an issue to require PRACK?
>>> [TS] I see potential for easier GW/SBC interworking with vanilla-ICE
>> UAs, that did not implement PRACK
>> I don't get it.
>> If you are talking about SBCs that terminate/relay media, then the leg
>> doing trickle-ICE is separate from the leg doing vanilla-ICE. So what
>> is
>> the issue?
>> And if you have a signaling-only SBC, and one leg supports trickle-ICE
>> while the other side supports only vanilla-ICE, then just use
>> vanilla-ICE e2e. You won't gain anything by an intermediary trying to
>> map trickle-ICE to vanilla-ICE.
> [TS]
> If the trickle-ICE side uses PRACK and the vanilla ICE side does not, the interworking SBC does not only have to collect the trickled candidates and send it on as a bunch once trickling finished. It also has to interwork PRACK.
> As you know the PRACK request can contain a new SDP offer or you could also use UPDATE for another SDP O/A before the 200 OK to the INVITE request. This is rather nasty to interwork if not impossible.

If trickle-ICE worked without PRACK, then the SBC *still* needs to 
collect up all the trickled candidates and send them when it can based 
on the limitations of vanilla-ICE. So the use of trickle-ICE provides no 
speedup compared to using vanilla-ICE e2e.

Also, it sounds like trickle-ICE is requiring changes in the ordering of 
how candidates are tried. If one side uses trickle-ICE and the other 
doesn't, then ISTM that may break.

So I'm still not seeing a case here when it makes sense to gateway 
between trickle-ICE and vanilla-ICE. There may be one, but I'm not 
seeing it.