[OpenSER-Users] stun and symmetric

[Iñaki Baz Castillo]

El Thursday 12 June 2008 08:59:55 Pezhman Lali escribió:
> Dear,
> I find that stun and symmetric nat can not work together ,
> but some big sip providers like sipgate or fwd, added stun settings to
> their ata as default without, any question about customer's nat type.
>
> where is the key ?

AFAIK a device doing STUN test discovers the type of its NAT and returns a 
value to the application invoking it (the ATA).
If the ATA receives "Symmetric NAT" when doing he STUN test it cannot set 
public IP:port in the SIP messages since the ANT type will make them not 
working.

So, it's a device decission wherever to use STUN or not depending on the STUN 
test result. For example Twinkle or Ekiga refuse to set the public IP:port 
discovered via STUN test if the result of the test is "Symmetric NAT".

So if a device (an ATA for example) does STUN test and receives "Symmetric 
NAT" it shouldn't apply STUN to send requests.


-- 
Iñaki Baz Castillo
ibc at in.ilimit.es