PURPOSE: To save number of stages of switches of a sorting network more than that of a conventional switch by setting a terminal number at a border when output terminal numbers are divided into two to output terminal information in unconnected packet.

CONSTITUTION: Output terminal numbers at the border when output terminal numbers from (000) to (111) are divided into two are (011) and (100). In order to make an intermediate value between both the numbers, 1 bit is added after the LSB of an input header, the additional LSB of a connection packet is set to '0', and an input header of unconnection packet is selected to be (0111). In a sorting network 3 of a pre-stage, two packets inputted to each switch 1 are shared in the direction of the arrow according to the relation of the quantity of the input header. In a routing network 4 of a post-stage, the network is shared to the upper side when the 1st bit of the MSB of the input header is logical 1 and to the lower side when logical 0 by a switch 2 of the 1st stage.