Re: [Fwd: I-D ACTION:draft-jennings-midcom-stun-results-00.txt]

At 07:46 PM 2/13/2004, Jonathan Rosenberg wrote:
>I disgaree.
>
>Cullen's results show that we are seeing hybrid NATs whose type depends on whether the random port selected by the client is allocated already or not. In such a case, if the client picks an already-allocated port during the detection phase, it may detect the nat as symmetric, when it fact it might be port restricted in other cases.
>
>With ICE, if you happen to be unlucky during a stun allocation, turn would get used. If you're lucky, and you get a port-restricted port, then the relay would not be used.

So here is a case which makes me puzzled and possibly needs some
extra work: SIP client behind a restrictive NAT. With STUN assumptions
it will work (as long as they hold, of course),the client will send 
a "primer" packet to UAS and UAS media will come in.

With ICE, a UAS will first check connectivity to UAC's STUN address.
The ICE draft suggests doing so on the initial application request
(SIP INVITE e.g.) to keep call set up time low. At this moment however, 
UAC's NAT is not primed yet and the STUN check reports no connectivity.

-jiri

--
Jiri Kuthan            http://iptel.org/~jiri/