Re: [Ice] ICE PAC: When to start the timer waiting for possible peer reflexive candidates?

[Nils Ohlmeier <[e-mail]>]

> On Apr 29, 2019, at 11:07, Justin Uberti <[e-mail]> wrote:
> 
> However, you can have a local candidate long before the remote peer gets it, so starting the timer once you have a candidate sounds strange to me. I think we should at least wait until the agent has sent the agent to the peer. 
> 
> This is an important observation - we don't want to start the timer until we think both us and the peer agent are running ICE processing (e.g., if we just gathered candidates but didn't send an offer, we shouldn't start the timer). I'm not totally sure what you meant above, but one way to ensure we're in the right state would be to start the timer when both of the below are true:
> 1) We have sent or received an answer.
> 2) Local candidate gathering has completed (including the case when zero candidates have been gathered).
> 
> #2 may not be strictly necessary, but gives us more flexibility in trickle cases if gathering takes a very long time (10+ seconds) for some reason.

Just as warning here: the worst case scenario is that a TURN and/or STUN server was provided/configured which is not reachable. In that case local gathering will only end after the STUN transactions to these unreachable servers have timed out, which by default is 32 seconds.

Doesn’t it make more sense to have #2 be something like: have received at least one remote candidate, even it turns out to be in an locally unsupported format, or an end-of-canditates with no candidates provided at all.

This would result though in situations where you never start the timer if you receive an answer SDP, but never any ICE candidate or end-of-candidates. Which to me looks some strange edge case where the remote agent has crashed or otherwise failed to gather anything including end-of-candidates.

Best
  Nils Ohlmeier