>Register is used JUST to **RECEIVE** calls, not to send calls.
>
>SIP uses http-digest autentication. This means: in **EVERY** INVITE a proxy 
>wnat to authenticate the client (Asterisk) receives a challenge from the 
>proxy and the client must generate a hash (a response) with its credentials 
>and the nonce received.

Ok, thanks for the reply Iñaki. So in the case of a configuration like mine what are other people doing to negate the

need to define all the users in both Asterisk and OpenSER? Are you authenticating the users on OpenSER based

on source IP? Or allowing all connections without authentication? 

And in general any pointers on the best way for me to achieve a simple accountig solution that is easy to maintain 

as more asterisk boxes and users are added?