Packet communication apparatus and packet communication method

A packet communication apparatus that connects a first network to a second network, the apparatus comprising:

• a network interface unit;
• and
• a processing unit,
• wherein the processing unit
• intercepts a communication from the first network through the network interface unit when the communication uses a handshake communication protocol, and buffers data packets,
• transfers, as a proxy, response packets and the data packets to a terminal device disposed in the first network,
• stops the transmission of the data packets belonging to an arbitrary packet flow to the second network when the reception of the response packets belonging to the packet flow from the second network is ceased for a network outage detection time or more set for each of the arbitrary packet flows, while transmitting the data packets belonging to the arbitrary packet flow to the second network,
• continues to stop the transmission of the data packets belonging to the packet flow until receiving a failure notification packet for notifying the occurrence of a failure in the second network, or recovery from the failure, from the second network, or for a given period after receiving the failure notification packet, and
• thereafter retransmits the data packets whose corresponding response packets are not received, belonging to the packet flow.

A packet communication method in a packet communication apparatus that connects a first network to a second network, the method comprising:

• intercepting a communication between the first networks when the communication uses a handshake communication protocol, buffering data packets, and transferring, as a proxy, response packets and the data packets to a terminal device disposed in the first network;
• stopping the transmission of the data packets belonging to an arbitrary packet flow to the second network when the reception of the response packets belonging to the packet flow from the second network is ceased for a network outage detection time or more set for each of the arbitrary packet flows, while transmitting the data packets belonging to the arbitrary packet flow to the second network;
• retransmitting a the first data packet whose corresponding response packet is not received, belonging to the packet flow to the second network in a retransmission attempt period set for each of the arbitrary packet flows, immediately after the data packet transmission stops;
• and
• retransmitting the remaining data packets whose corresponding response packets are not received, belonging to the packet flow, at the time of receiving the response packets from the second network.