A control node includes: a monitoring packet transmission section for transmitting a monitoring packet; a monitoring packet reception section for receiving a monitoring packet; an adjustment section for selecting a redundant node from a non-control nodes; a packet generation section for generating a setup packet for specifying the redundant node out of the non-control nodes in accordance with information about the redundant node selected by the adjustment section; and a packet transmission section for transmitting the setup packet to the non-control node. The non-control node includes a control section that acquires information about the traffic upon receiving the monitoring packet, transmits a monitoring packet after acquisition of the traffic, and specifies the non-control node as the redundant node based on information about the redundant node contained in the setup packet upon receiving the setup packet.