Both a connection server and a relay connection server are installed in an IP transfer network; a function similar to a line connection control of a subscriber exchanger is applied to a connection server; a function similar to a line connection control of a relay exchanger is applied to the relay connection...http://www.google.de/patents/US8121113?utm_source=gb-gplus-sharePatent US8121113 - Terminal-to-terminal communication connection control method using IP transfer network
