In an ANS used for a television conference between calling and destined conference room terminals accommodated in an ATM network, an address of each conference room terminal is stored in an address database as address resolution data which have no hierarchical structure and which therefore uniquely define each conference room terminal. A priority level of each conference room terminal is also stored in the address database and is referenced on occurrence of congestion so as to determine whether or not a connection is released during a conference. Reservation data may be stored in the ANS together with topology data and connection data.