Communication system, communication device, controller, and method and program for controlling forwarding path of packet flow

1. A network device to be used for a packet handling, the network device comprising:

a first unit to communicate with a controller according to a first protocol, and to receive a packet handling rule from the controller which is capable of sending the packet handling rule to a plurality of the network devices via a network between the controller and the network device;

a second unit to classify, based on a classification rule for classifying a received packet, 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 set based on a second protocol; and

a third unit to request the packet handling rule to the controller when the packet handling rule for forwarding the received packet is not set in the network device.

2. The network device according to claim 1 , wherein the second unit classifies the packet based on an attribute of the packet.

3. The network device according to claim 1 , wherein the second unit classifies the packet based on whether the packet is to be forwarded within a predetermined network domain.

4. A system, comprising:

a network device to handle a packet; and

a controller to send, via a network between the controller and the network device, a packet handling rule to a plurality of the network devices according to a first protocol,

wherein the network device classifies, based on a classification rule for classifying the packet, whether to handle the packet according to the packet handling rule or to handle the packet according to a table entry that the network device autonomously set based on a second protocol; and

wherein the network device requests the packet handling rule to the controller when the packet handling rule for forwarding the received packet is not set in the network device.

5. The system according to claim 4 , wherein the network device classifies the packet based on an attribute of the packet.

6. The system according to claim 4 , wherein the network device classifies the packet based on whether the packet is to be forwarded within a predetermined network domain.

7. A method to be used for a packet handling, the method comprising:

communicating with a controller according to a first protocol;

receiving a packet handling rule from the controller which is capable of sending the packet handling rule to a plurality of the network devices via network between the controller and the network device;

classifying, based on a classification rule for classifying a received packet, 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 set based on a second protocol; and

requesting the packet handling rule to the controller when the packet handling rule for forwarding the received packet is not set in the network device.

8. The method according to claim 7 , wherein the classifying comprises:

classifying the packet based on an attribute of the packet.

9. The method according to claim 7 , wherein the classifying comprises:

classifying the packet based on whether the packet is to be forwarded within a predetermined network domain.