A system for routing voice telephone calls over IP networks as opposed to traditional switched circuit networks. The voice communications during the telephone call are packaged as digital data and access the Internet through gateways. The system supports the linking of a source gateway in a first clearinghouse to a destination gateway in a second clearinghouse. The system further supports the selection of a destination gateway based on factors such as cost, speed of routing, and transmission quality of the voice data. The components of the system are arranged so as to minimize the number of signals sent between clearinghouses in identifying the optimal destination gateway.