[Asterisk-Users] world incoming calls

[Sergey Lapin]

Hi, all!!!

We have one big Asterisk server, supporting LAN calls inside and
gatewaying calls to voipexchange.ru for real phone calls.

Now we need to recieve world calls.

All our users authenticated using SIP. We want to recieve calls from
other SIP clients, that are not on our server without breaking security,
so our users should not be able to make and recieve calls without
authentication. Is it possible at all?
How I could implement it?

Thanks in advance,
S.