A network session is established by a session establishment procedure in accordance with whether or not a difference in priority of session establishment exists among a plurality of terminals for which the network session is to be established. Based on reserved connection information registered in a database, a network administration device for establishing a network session among a plurality of terminals uses a first session establishment procedure that treats all of the terminals in the same manner when there is no difference in the priority of session establishment among the plurality of terminals, and uses a second session establishment procedure that inquires and performs other operations in advance as to whether or not to establish a session with high-priority terminals and treats with priority the terminals of high-priority users when there is a difference in the priority of session establishment.