To provide a service through a wide area network to a client who a huge amount of data is to be transmitted among many points.

In the wide area network using the Internet as a backbone, an ISX/ISP provider especially selected, a router of the ISX/ISP provider rotes an Alter WAN packet of the wide area network along a private tunnel through the Internet and the private tunnel consists of data paths with a wide bandwidth and less hope number of times. A firewall is built up at each termination of each private tunnel, the firewall recognizes an IP packet addressed to a device at other termination of the tunnel and encapsulates the packets with other IP packet having a header including a destination address and an IP address of the fire wall at an incredible side at the other termination of the tunnel.