Hi Brian,
This can easily achieved by using "failure route" mechanism to implement a serial forking. If first destination fails, you end up in failure route, where you set a new destination and resend....and so on - see http://www.opensips.org/Resources/DocsCoreRoutes16#toc3 .
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Well, of course that X did this and Y did that...this is not the point.
The point is why kamailio is importing the core and TM from SER project (the number one "enemy" of OpenSER from the first day to now) if there is so much knowledge in working on those pieces of code? because it is not...Just polishing and shiny improvements that any coder can do.
Hi Oliver - yes you can do this with OpenSER/OpenSIPS. Actually you do not have to set OpenSIPS as a front registrar, but only as an authentication server. OpenSIPS will receive the REGISTER from mobile clients, perform authentication and if OK, relay the REGISTER to Asterisk to be processed. In this way, everybody registers on Asterisk, but you keep OpenSIPS as a front authentication server.