[Asterisk-Users] IP to IP call without server?

[nkb]

Hi.
I'm really new.
I was just wondering if it is possible at all to do a IP to IP call 
without a * server (or as a matter of fact, any other kind of server)? 
say I'm at mydomain.com's 10.0.0.1 and I want to call my buddy at 
hisdomain.com's 192.168.0.3. Is this sort of things possible? Or must we 
all both be registered with the same server to do that? Can this not be 
done without passing thru server (*)?
Thanks.