[Users] Understanding the Call Flow

Hi all, I am trying to get a better understanding of the call flow - specifically for distant users. In our current configuration we have all of the UAs registering to our OpenSER box which manages the authentication, and passes the call forward if allowed. Like so: UA -> SER -> PSTN GW -> PSTN I have been experimenting with using a mediaproxy/rtp proxy to improve the quality of service to users beyond the network edge - effectively: UA -> Proxy -> SER -> PSTN GW -> PSTN While this works great, we would like to place some PSTN Gateways closer to the edge of the network (for more than one obvious reason). In this case we would still have a central SER instance for authentication and accounting, but I would like for the edge proxies to be able to send the traffic to the closest applicable PSTN GW. How does one go about deploying something like this? What does the call flow look like? What software components do I need in what places? What is the glue that holds all of this together? Thanks, Max -- Max Clark http://www.clarksys.com