Network relay device, network connection confirmation method, and network

1. A network relay device, comprising:

a device for receiving, from an external network relay device, connection confirmation information indicative of being in communication connection with the external network relay device, when no next connection confirmation information is received within a predetermined period of time, sensing that a communication failure has occurred between the external network relay device and an other external network relay device, and when the received connection confirmation information comprises a particular connection confirmation information comprising connection confirmation information transmitted from a predetermined external network relay device, generating a return confirmation information and forwarding the return confirmation information to the predetermined external network relay device, to return the received connection confirmation information to the network relay device to the predetermined external network relay device.

2. The network relay device according to claim 1 , wherein said device comprises:

a transmit/receive unit for transmitting/receiving the connection confirmation information;

a frame determination unit for determining whether or not the connection confirmation information received in the transmit/receive unit comprises the particular connection confirmation information; and

a forwarding control unit for, when the frame determination unit determines that the connection confirmation information comprises the particular connection confirmation information, providing the return confirmation information to the predetermined external network relay device.

3. The network relay device according to claim 2 , wherein said device further comprises:

a frame conversion unit for, when the frame determination unit determines that the connection confirmation information comprises the particular connection confirmation information, generating the return confirmation information from the particular connection confirmation information; and

the forwarding control unit transmitting the return confirmation information generated by the frame conversion unit, from the transmit/receive unit to the predetermined external network relay device.

4. The network relay device according to claim 3 , wherein the connection confirmation information comprises source identification information for identifying a source having transmitted the connection confirmation information, destination identification information for identifying a destination,

wherein, when the destination identified by the destination identification information comprises the network relay device, and the source identified by the source identification information comprises the predetermined external network relay device, the frame determination unit determines that the connection confirmation information comprises the particular connection confirmation information, and

wherein, when the destination identified by the destination identification information comprises the network relay device, and the source identified by the source identification information is not the predetermined external network relay device, the frame determination unit determines that the connection confirmation information is not the particular connection confirmation information.

5. The network relay device according to claim 4 , wherein the frame determination unit and the frame conversion unit comprise hardware.

6. The network relay device according to claim 1 , wherein said device further comprises:

an administration information storage unit for storing a receiving time of the connection confirmation information.

7. The network relay device according to claim 6 , wherein, when the next connection confirmation information is received within the predetermined period of time, the receiving time stored in the administration information storage unit, which is associated with the connection confirmation information, is renewed.

8. The network relay device according to claim 1 , wherein, when the received connection confirmation information comprises the particular connection confirmation information, the device generates the return confirmation information instead of rewriting contents of the particular connection confirmation information.

9. The network relay device according to claim 1 , wherein the predetermined external network relay device comprises a source that is identified based on a media access control (MAC) address of a port.

10. A network connection confirmation method, comprising:

in a transmit/receive unit for transmitting/receiving connection confirmation information indicative of being in communication connection with an external network relay device, receiving the connection confirmation information;

sensing that a communication failure has occurred between the external network relay device and an other external network relay device, when no next connection confirmation information is received within a redetermined period of time;

determining whether the connection confirmation information received in the transmit/receive unit comprises a particular connection confirmation information comprising connection confirmation information transmitted from a predetermined external network relay device; and

when it is determined that the connection confirmation information comprises the particular connection confirmation information, generating a return confirmation information and forwarding the return confirmation information to the predetermined external network relay device, to return the received connection confirmation information to the predetermined external network relay device.

11. The network connection confirmation method according to claim 10 , further comprising:

wherein, in said generating, the return confirmation information is generated from the particular connection confirmation information, and

wherein the return confirmation information includes transmitting the generated return confirmation information, from the transmit/receive unit to the predetermined external network relay device.

12. The network connection confirmation method according to claim 11 , wherein the connection confirmation information comprises source network relay device identification information for identifying the external network relay device having transmitted the connection confirmation information, and destination network relay device identification information for identifying a destination network relay device,

wherein, when the destination network relay device identified by the destination network relay device identification information comprises the network relay device, and the source network relay device identification information comprises the predetermined external network relay device, it is determined that the connection confirmation information is the particular connection confirmation information, and

wherein, when the destination network relay device identified by the destination network relay device identification information comprises the network relay device, and the source network relay device identification information is not the predetermined external network relay device, it is determined that the connection confirmation information is not the particular connection confirmation information.

13. A network, comprising:

a plurality of connected network relay devices; and

one network relay device receiving connection confirmation information indicative of being in communication connection between the one network relay device and another network relay device, when no next connection confirmation information is received within a predetermined period of time, sensing that a communication failure has occurred between the one network relay device and said another network relay device, and when the received connection confirmation information comprises a particular connection confirmation information comprising connection confirmation information transmitted from a predetermined network relay device, generating a return confirmation information generated from the particular connection confirmation information and forwarding the return confirmation information to the predetermined external network relay device, to return the received connection confirmation information to the one network relay device to the predetermined network relay device.