PURPOSE: To select and connect a line provided with appropriate features by selecting a transmission enable line by the transmission destination identification information of a data frame based on the characteristics of the data of a hierarchy higher than a specified hierarchy.

CONSTITUTION: When hit data are present in the data inputted to an address processor 102, a CPU 121 reads a hit segment address, adds '1', writes it in an address register AR, specifies a port address and sets connection to an output port in a switching element unit SEU 111. Then, a port to which loss priority display CLP correspond corresponding to the propriety of the cancellation of the data is selected. Then, the CPU 121 sets data transfer from the AP 102 to the SEU 111 in a DMAC 103 and transfers the data of the AP 102 to the SEU 111. At the time the AP 102 outputs the data of 32 bits of the OR of the value of a compound data register storing the PT and CLP of input data in lower four bits and the VPI and VCI of an output side line stored in a segment by 8 bits.