In an OpenFlow network, a “proactive type” is attained and hardware (HW) performance problem is solved. Specifically, in the OpenFlow network, each of a plurality of switches executes, on a reception packet that meets a rule of an entry registered in its own flow table, an operation based on an action defined in the entry. A controller registers an entry, in which an identifier unique to a path calculated based on a physical topology of a network composed of the plurality of switches is set as a rule and an output from a predetermined output port as an action, in each of the plurality of switches before communication is started among the plurality of switches.