Re: [rtcweb] Filling in details on "trickle ICE"

Emil Ivov <emcho@jitsi.org> Thu, 18 October 2012 12:31 UTC

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Date: Thu, 18 Oct 2012 14:31:04 +0200
From: Emil Ivov <emcho@jitsi.org>
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To: Christer Holmberg <christer.holmberg@ericsson.com>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] Filling in details on "trickle ICE"
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On 18.10.12, 14:26, Christer Holmberg wrote:
> Hi,
> 
>>>>>> 4) How does trickle ICE work without “relaxing” RFC3264
>>>>>> O/A? It seems like you really want to be able to trickle
>>>>>> via updated offers that may be generated prior to the
>>>>>> corresponding answer or reject?
>>>>> 
>>>>> One of my comments on the trickle draft was about that. The
>>>>> draft says that a new offer can be sent "at any time", but my
>>>>> comment was that it should be according to 3264.
>>>> 
>>>> That's not exactly what the draft says. What it does say is:
>>>> 
>>>> At any point of ICE processing, a trickle ICE agent may receive
>>>> new candidates from the remote agent.
>>> 
>>> Correct.
>>> 
>>> And, it is of course true in one sense, because STUN requests
>>> creating peer reflexive candidates can of course be received at
>>> any time :)
>> 
>> True but in the "Trickle ICE" case it would be more common to learn
>> new candidates through signalling (rather than PR candidates during
>> conn checks). This is what the text refers to. I agree we should
>> make it clearer that we do not really mean PR candidates here.
> 
> Sure.
> 
> (Remember our previous discussion, though, about PR candidates being
> enough if the remote peer is ICE lite ;)

I do :).

>>>>> IF we are going to relax 3264 (I really hope we are NOT), it
>>>>> needs to be clearly described somewhere. We cannot have a
>>>>> number of I-Ds doing it "on the run"...
>>>> 
>>>> I don't see how trickle ICE would require any changes to the
>>>> O/A model. Candidate trickling semantics are completely
>>>> separate from those in 3264.
>>>> 
>>>> Yes, the 3264 offer may, in some cases, contain a first batch
>>>> of candidates and the the 3264 may have to be delayed until ICE
>>>>  processing yields valid pairs for every component but that's
>>>> about it.
>>>> 
>>>> Am I missing something?
>>> 
>>> I guess the question was whether one, after the first batch of 
>>> candidates have been sent in an offer, should be allowed to send
>>> the second batch in a new offer - before an answer to the
>>> previous offer has been received. That would be against 3264.
>> 
>> It would indeed but I am not sure why we would think of additional
>> candidate drops as offers at all. They are just independent
>> signalling and are only loosely related to the 3264 semantics.
>> 
>> Of course with SIP we would have a problem caused by the fact that
>> additional in-dialog signalling is blocked by the 3264 answer.
>> However, that's specific to SIP and will probably be best served
>> with a SIP specific solution (e.g. UPDATEs or forcing early
>> answers, or something else).
> 
> It is sure that SIP may add its own limitations, but the general O/A
> is generic.

Sure, and we agree that the general O/A need not be used for trickle
ICE, right?

Emil

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