PURPOSE: To provide required communication quality to each throughput attribute by varying the selection range of a path corresponding to a traffic of a packet call whose throughput attribute differs.

CONSTITUTION: Switches SW 10-SW 37 have an input terminal and an output terminal respectively and a function applying exchange connection of a packet call coming from an optional input terminal to an optional designated output terminal. Moreover, a switch network control processor in a packet exchange decides the designation of the output terminal according to a prescribed protocol and it is added to a label part of all packets belonging to one and same packet call as path information. Then the calculation is applied according to a predetermined order to select an optimum path and the path is decided when the result is within a permissible value. Thus, the communication quality to a packet call having a different throughput attribute and priority from each call is satisfied.