[Serusers] Proxy to Proxy between different realm/domain

[Chahn John Kim]

Hi all,
Need you experts' help on SIP design.

I've setup a testbed composed of two SER Registrar/Proxies in two
different realm/domain(s) as below;

<--Internal Private(192.168.x.0----><----External Public(x.x.x.0)--------->
UA1<-----------------> SER1 <---------------------> SER2 <------------> UA2
         Mydomain.org Registrar/Proxy    Theirdomain.org Registrar/Proxy


What is the right way to pass the user credential of UA1 to SER2 so that
"INVITE" to UA2 will be accepted at SER2, knowing that UA1 user has its
login ID/password to SER2 but it is locally "REGISTER"ed at SER1 in
private domain?

I guess I am having trouble understanding working mechanism of "inter" SIP
realm or domain.

Any comments will be appreciated.

John Kim
email: johnk at koreanet.us
       johnk at netcomusa.us