We are thinking of going through a path of building a redirect registrar server using opensips. In addition we are planning to add an additional SBC layer also using opensips. My question is can we use opensips in such a way that when an authenticated INVITE comes in to the SBC it is sent over to the redirect registrar server which if authorized will respond with a 3xx that will indicate the SBC that it should redirect this INVITE to the user's assigned PBX. I would of course expect the SBC to absorb the 3xx response and have this all seem less for the client. Our objective here to get the authentication server out of the call path so future SIP traffic for a dialog does not go through this server.
Any thoughts/ suggestions/ past experience with this kind of setup would be helpful.