Patent ID: 8670451

Claim:
A network system comprising: a gateway arranged on a border between a public network and a private network, and configured to relay data communicated therebetween; a terminal located in the private network, including a virtual interface that corresponds to a physical interface of the gateway on a public network side, and configured to transmit and receive data to and from other terminals located on the public network through the virtual interface; and a transfer path configured to transfer data between the physical interface and the virtual interface, the data being encapsulated with a header that includes information on the gateway or the terminal located in the private network, wherein the header is added by the terminal and deleted by the gateway for a downlink transfer in the private network, and is added by the gateway and deleted by the terminal for an uplink transfer in the private network, wherein the gateway: determines an interface to which the data is to be output at a destination of the data using a determining unit; divides data to be transferred to the terminal in the private network into a plurality of pieces using a dividing unit; adds a header including a transmission/reception confirmation number to the pieces using a transmission/reception control unit; re-transmits, when no reception response to the pieces transmitted to the terminal in the private network is received from the terminal in the private network, transmitted pieces to the terminal using a re-transmission control unit; transmits, when data is received externally, a reception response to a source from which received data is transmitted using the re-transmission control unit; and re-constructs a plurality of pieces of data transferred from the terminal in the private network into original data using a reconstructing unit.