COMMUNICATION SYSTEM, NETWORK RELAY DEVICE, NETWORK RELAY METHOD, AND PROGRAM

1 . A communication system comprising:

counter devices forming a pair; and

a plurality of network relay devices connecting the counter devices, wherein each of the network relay devices includes:

a plurality of communication ports provided for each of the counter devices and connecting the network relay device and the counter device;

a bridge port connected to another network relay device;

a processor configured to:

totalize, for each of multi-chassis link-aggregation groups set for the communication ports, a traffic amount received by the communication ports of the network relay device;

detect whether the communication port of the network relay device to be a transmission destination of traffic of the multi-chassis link-aggregation group is effective; and

acquire a traffic amount for each of multi-chassis link-aggregation groups in the other network relay device and information concerning whether the communication port of the other network relay device is effective; and

a transmitter that transmits a part of the traffic of the multi-chassis link-aggregation group to the other network relay device via the bridge port when a traffic amount per effective communication port in the network relay device is larger than the traffic amount per the effective communication port in the other network relay device by a threshold or more in the multi-chassis link-aggregation group.

2 . The communication system according to claim 1 , wherein the processor is configured to control the transmitter to calculate a traffic distribution amount per the effective communication port by dividing a traffic total amount in the same multi-chassis link-aggregation group by a total number of the effective communication ports in the multi-chassis link-aggregation group and determines a traffic amount transmitted to the other network relay device by dividing a difference between a traffic amount obtained by multiplying together the traffic distribution amount and the number of the effective communication ports of the network relay device and an actual traffic amount in the network relay device by the traffic total amount.

3 . The communication system according to claim 1 , wherein

the processor of each of the network relay devices is further configured to:

control the transmitter to transmit, when receiving traffic from the other network relay device via the bridge port, the traffic from the communication port of the network relay device connected to the counter device to be a transmission destination of the traffic,

give, to the traffic to be transmitted, an identifier of a multi-chassis link-aggregation group set for the communication port that receives the traffic, and

control the transmitter to transmit the traffic from a communication port other than the communication port in which the multi-chassis link-aggregation group specified by the identifier is set.

4 . A network relay device that constructs, in conjunction with another network relay device, multi-chassis link-aggregation connecting counter devices forming a pair, the network relay device comprising:

a plurality of communication ports provided for each of the counter devices and connecting the network relay device and the counter device;

a bridge port connected to the other network relay device;

a processor configured to:

totalize, for each of multi-chassis link-aggregation groups set for the communication ports, a traffic amount received by the communication ports of the network relay device;

detect whether the communication port of the network relay device to be a transmission destination of traffic of the multi-chassis link-aggregation group is effective; and

acquire a traffic amount for each of multi-chassis link-aggregation groups in the other network relay device and information concerning whether the communication port of the other network relay device is effective; and

a transmitter that transmits a part of the traffic of the multi-chassis link-aggregation group to the other network relay device via the bridge port when a traffic amount per effective communication port in the network relay device is larger than the traffic amount per the effective communication port in the other network relay device by a threshold or more in the multi-chassis link-aggregation group.

5 . A network relay method for a network relay device that constructs, in conjunction with another network relay device, multi-chassis link-aggregation connecting counter devices forming a pair, the network relay method comprising:

connecting, by a plurality of communication ports provided for each of the counter devices, the network relay device and the counter device;

connecting, by a bridge port, the network relay device to the other network relay device;

totalizing, for each of multi-chassis link-aggregation groups set for the communication ports, a traffic amount received by the communication ports of the network relay device;

detecting whether the communication port of the network relay device to be a transmission destination of traffic of the multi-chassis link-aggregation group is effective;

acquiring a traffic amount for each of multi-chassis link-aggregation groups in the other network relay device and information concerning whether the communication port of the other network relay device is effective; and

transmitting a part of the traffic of the multi-chassis link-aggregation group to the other network relay device via the bridge port when a traffic amount per effective communication port in the network relay device is larger than the traffic amount per the effective communication port in the other network relay device by a threshold or more in the multi-chassis link-aggregation group.

6 . (canceled)