Openflow switch and failure recovery method in openflow network

1. A failure recovery method used in an Open Flow network including a plurality of OpenFlow switches and an OpenFlow controller configured to control the plurality of OpenFlow switches, wherein

the OpenFlow controller has a memory in which a proxy OpenFlow switch for a first OpenFlow switch among the plurality of OpenFlow switches is registered, the proxy OpenFlow switch being one of the plurality of OpenFlow switches other than the first OpenFlow switch and wherein the failure recovery method comprises:

detecting, both in the first OpenFlow switch and the OpenFlow controller, a failure on a link between the first OpenFlow switch and the OpenFlow controller when a failure occurs on the link between the first OpenFlow switch and the OpenFlow controller;

transmitting a first request to establish an OpenFlow channel from the first OpenFlow switch to a second OpenFlow switch among the plurality of OpenFlow switches when the first OpenFlow switch detects the failure on the link between the first OpenFlow switch and the OpenFlow controller;

establishing a first OpenFlow channel between the first OpenFlow switch and the second OpenFlow switch in response to the first request;

transmitting a second request to establish an OpenFlow channel from the second OpenFlow switch to the OpenFlow controller when the second OpenFlow switch receives the first request from the first OpenFlow switch;

allowing the second request when the OpenFlow controller detects the failure on the link between the first OpenFlow switch and the OpenFlow controller and the second OpenFlow switch that has transmitted the second request is registered as the proxy OpenFlow switch for the first OpenFlow switch in the memory; and

establishing a second OpenFlow channel between the second OpenFlow switch and the OpenFlow controller when the second request is allowed.

2. The failure recovery method according to claim 1 , further comprising:

configuring a forwarding circuit in the second OpenFlow switch so as to forward control information transmitted from the first OpenFlow switch through the first OpenFlow channel to the OpenFlow controller through the second OpenFlow channel and forward control information transmitted from the OpenFlow controller through the second OpenFlow channel to the first OpenFlow switch through the first OpenFlow channel.

3. The failure recovery method according to claim 1 , wherein

the second OpenFlow channel is established on a connection established between the second OpenFlow switch and the OpenFlow controller in response to the second request.

4. The failure recovery method according to claim 1 , wherein

the second OpenFlow channel is established on a connection that has been established in advance between the second OpenFlow switch and the OpenFlow controller.

5. The failure recovery method according to claim 1 , wherein

the second OpenFlow switch is designated in advance for the first OpenFlow switch.

6. The failure recovery method according to claim 5 , wherein

a path between the first OpenFlow switch and the second OpenFlow switch is designated in advance for the first OpenFlow switch.

7. The failure recovery method according to claim 1 , wherein

the first OpenFlow switch adds an identifier to identify communication between the first OpenFlow switch and the OpenFlow controller to the control information and transmits the control information through the first OpenFlow channel, and

the OpenFlow controller adds the identifier to the control information and transmits the control information through the second OpenFlow channel.

8. The failure recovery method according to claim 1 , wherein

the OpenFlow controller collects statistical information that represents traffic amount of each OpenFlow switch,

the OpenFlow controller specifies an OpenFlow switch with the least traffic amount based on the statistical information,

the OpenFlow controller transmits an instruction to notifies the first OpenFlow switch of the specified OpenFlow switch, and

the first OpenFlow switch transmits to the OpenFlow switch specified by the OpenFlow controller a request to establish an OpenFlow channel between the first OpenFlow switch and the OpenFlow controller.

9. The failure recovery method according to claim 1 , further comprising:

collecting statistical information that represents a load of each OpenFlow switch, and

determining the second OpenFlow switch in accordance with the statistical information.