Abstract: In a network in which all information from terminals having various traffic characteristics is transmitted/switched by a fixed length block including a virtual channel id, a terminal requesting communication declares destination address information and traffic characteristics of the requested communication upon set-up to a network. The exchange in the network expresses traffic characteristics of an individual terminal and an offered load (estimated cell flow) in the network. The traffic characteristics of each terminal are expressed as a maximum cell flow generated from the terminal in time units .DELTA.(i) (i=1, 2, . . . , n) having n predetermined lengths. The predicated offered load of the line supposing that a new request call is accepted is expressed as an estimated cell flow predicted to be transmitted to the line in the time unit .DELTA.t(i) by using traffic characteristic values of the calls currently transmitting on the line and a new request call.