Networks 30, 31, 32, 33 and 34 are internal networks (intranets) consisting of LANs created by connecting computers and network equipment based on standards such as Ethernet???, Token Ring, and FDDI, or WANs consisting of LANs connected with each other by means of dedicated lines, and network 35 represents an external network such as the Internet or public networks consisting of LANs and WANs inte