[libnice] why is TURN prefered before STUN ?

[Philip Withnall]

Hi,

On Mon, 2014-11-10 at 13:47 +0100, Klaus Kranz wrote:

> in the hope not chasing a phantom, I am wondering that even though a
> STUN srflx based connection is possible, libnice uses the TURN relay
> path.
> 
> Is there a way to let the library select relay as the last resort only
> in the case that STUN srflx fails ?

ICE assigns priorities to candidate pairs, and STUN is always
prioritised above TURN — precisely because TURN is so slow and
expensive.

Are you using trickle ICE[1] or normal ICE? How are you checking which
candidate pair libnice chooses to use? Are you waiting for the NiceAgent
to reach NICE_COMPONENT_STATE_CONNECTED or NICE_COMPONENT_STATE_READY?
The candidate pair selection isn’t final until STATE_READY.

This kind of general question can go on the libnice mailing so that
others can respond (and benefit from the answer!). :-)

Philip

[1]: https://tools.ietf.org/html/draft-ietf-mmusic-trickle-ice-01
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