A computer includes a WAN driver that causes data to be transmitted from a guest domain to a computer to use a first protocol, a WANonTCP/IP driver and a TCP/IP driver that add identification information of the guest domain to the data and cause the data to use a second protocol, and a LAN driver that transmits the data to the line accommodation apparatus using the second protocol. The line accommodation apparatus includes a line GW control unit that acquires the identification information of the guest domain from the data, extracts a line card corresponding to the identification information, and causes the received data to use a third protocol; a line card driver that transmits the data to the computer via the extracted line card using the third protocol.