[OpenSER-Users] OpenSER as SIP Proxy for PSTN Gateway

Hi, As you may work out Im not an expert in this, hopefully for those of you that are this is a pretty straight forward question. Im trying to implement something like this: Cisco_as5300 <-----> OpenSER <------> Atersisk PSTN Gateway SIP Proxy PBX ^ Radius I am attempting to setup OpenSER as a SIP proxy for a Cisco PSTN Gateway, on the other side of OpenSER I have an Asterisk system. My confusion centres around the connection between the end users (SNOM or whatever) which hang off Asterisk and the connection between Asterisk and OpenSER. I have configure Asterisk to SIP register to OpenSER, all works ok here and Asterisk sees OpenSER as a SIP peer and channel. The bit Im not getting is that when someone dials a number from a handset connected to Asterisk that needs to route out via OpenSER, Asterisk seems to pass the username and password credentials of the handset to OpenSER. Firstly if its going to do this, then what is the point of SIP registering Asterisk as its authenticating ever session as individual entities anyway, secondly this isnt scaleable :( it seems to mean I have to configure each SNOM user both in Asterisk and in OpenSER. All of which doesnt seem very logical, can anyone tell me if I'm doing something wrong or if Im approaching this in the wrong way or if I need to approach the problem in some other way... The end goal of this is that Id like the ability to bill on a per SIP peer basis customer Asterisk boxes, I dont want to end up in a situation were I have to know about every SNOM a customer has. many many thanks in advance, Im a bit stuck at the mo! thanks Andy.