When a first transfer-device in a first network receives, from a first communication-device in the first network, a packet addressed to a second communication-device in a second network, the first transfer-device requests a location management server to provide first information identifying a second transfer-device that is included in the second network and operable to transfer the packet to the second communication-device. The location management server notifies at least one of transfer-devices in the first network of the first information. After the transfer-devices in the first network have been notified of second information identifying a third transfer-device that is included in the first network and coupled to the second transfer-device via a route whose state is relatively favorable, the third transfer-device transfers the packet to the second transfer-device via a communication tunnel coupling the third transfer-device with the second transfer-device.