To provide an IP telephone system, its gateway router and a method for allowing the preferential connection of emergency calls even if congestion occurs or the number of sessions reaches the upper limit of a processing capacity.

The gateway router in the IP telephone system has determining means (101 and 102) which determine whether an arrived session control signal is an emergency call or not and control means (107, 108, 111 and 112) which give priority to the connection processing of session control signals of emergency calls by dynamically assigning simultaneously connectable sessions between emergency calls and other ordinary calls.