The process starts with the Switch receiving incoming call from the originating gateway or any other SIP endpoint. The switch then identifies the caller’s Account (1). This process is called Authentication. If the account cannot be found the call is rejected. Once the Account has been identified the switch enumerates all Customers that need to be charged for the call (2). For Account and each Customer in the list the switch then locates associated Tariff and Rate based on called number and calculates the maximum duration for the call (3). If one or more Rates could not be found or if balance of Account or one of Customers is not sufficient the call is rejected.
The next step is Routing – based on called number and routing configuration assigned to the Account or Customer the switch enumerates one or more Connections for terminating the call to (4). Based on that information it performs actual overflow routing (5) until the call is either connected or there are no more connections to try.
Once the call has been completed, either successfully or unsuccessfully the switch charges Account, Customer(s) and Vendor associated with the call and creates the appropriate CDRs (6).