A communication system includes a network device to be used for packet handling; and a controller capable of sending, to network device, a packet handling rule according to a first protocol.The network device classifies, based on a condition, indicative of a scope under which the controller is capable of controlling the network device, whether to handle the packet according to the packet handling rule sent from the controller or to handle the packet according to a table entry that the network device autonomously sets based on a second protocol.