Network device, controller for controlling network device, and network control system

A controller for controlling at least one network device constituting a software-defined network (SDN), wherein, when a request for a path from a first host to a second host is received, an optimal path is set to give a continuous query language (CQL)-based instruction to respective network devices on the optimal path,

• network devices closest to the respective network devices on the optimal path are identified, and
• an instruction to transmit a packet having the first host as a source address and the second host as a destination address to the identified closest network devices when the packet is received is given to the respective network devices.

A network control system, comprising:

• at least one event processing network connected to a central server,
• wherein each of the event processing network is configured to receive an event condition and an instruction describing an operation according to the event condition from the central server, analyze sensor data of the event processing network itself or a message received from a surrounding event processing network on the basis of the instruction given by the central server, and perform the operation according to the event condition when the event condition is satisfied.