In the case of incoming calls from a vendor via IP, there is one further issue: since the call reaches your network via the Internet, potentially anyone could be attempting to send you a call in such a fashion. PortaSwitch must be able to correctly authorize calls coming from your vendors (otherwise these calls will be dropped); yet only calls from a “real” vendor should go through.
- Someone dials a phone number assigned to your customer (1).
- The vendor receives this call from the PSTN network and sends the call to PortaSIP (2).
- PortaSIP sends an authorization request to the billing engine (3), using either a remote IP address or a SIP username as the verification parameter (for more details about these two methods of authentication, see the Call authorization rules chapter).
- PortaBilling will check whether this authorization request is related to a “Calls from Vendor via SIP” connection (4). If there is no match, it assumed to be a normal call from one of your customers, and the call will then proceed according to the standard algorithm. Otherwise (e.g., if this call is indeed coming via a “Calls from Vendor via SIP” connection), PortaBilling will compare the username and password supplied in the authorization request with those defined in the vendor account associated with this connection.
- If authentication succeeds (5) (e.g., the call is indeed being sent by your vendor), PortaBilling will apply the connection’s translation rules and check whether the dialed number belongs to one of your accounts (1234). If it does not, the call will be refused (since there has probably been a configuration error so that the vendor is routing international traffic to your network).
- PortaSIP receives the routing information for the call (6), and so now recognizes that the call should be sent to one of your SIP phones (7). Follow-me, UM parameters, and other related information are provided as well. One very important point is that this call will be charged to the account which receives the call.
- After the call is disconnected, the called account is charged for the call (8), and the costs of the call are calculated for the vendor.