PROBLEM TO BE SOLVED: To contribute to improvement of fault tolerance and availability of a network using an In-band control system in a control channel.SOLUTION: A switch comprises: a packet processing unit for processing a packet; a control channel management unit for managing a port for communicating with a control device through a control channel; a changeover message generation unit which retrieves control information whose output destination is a port connected to another switch from control information for configuring the control channel stored in the switch when a fault in the port is detected, generates a changeover message for giving instruction so as to change a transfer destination of a packet fitting the control information, and transmits the changeover message to an adjacent switch to a transmission source of the packet designated by the control information; and a changeover message processing unit for changing a port for communicating with the control device managed by the control channel manag
