NETWORK COMMUNICATION METHOD AMONG TWO OR MORE USER- SIDE CLOSED NETWORKS AND SERVER-SIDE CLOSED NETWORK, AND SERVER DEVICE

PROBLEM TO BE SOLVED: To operate a physical one server device of a server-side closed network as an exclusive server by not sharing the same among user-side closed networks, but independently providing the same to each of user-side closed networks. SOLUTION: Two or more user-side closed networks 31-33 are connected to the server-side closed network 10 by access servers 26, 28-30 by using an IP tunnel. When the connection is required, the access server 26 discriminates the closed network having made the requirement, attaches a specific identification code to the user-side closed network by means of a packet tag, and transfers the same to the server device 11. The server device 11 comprises multiple upper communication flows by protocol stacks 19-21, and lower communication flows from the protocol stacks 19-21 to logical device interfaces 23-25, and these communication flows 12-14 are assigned to the user-side closed networks 31-33. The server device 11 specifies the closed network of a transmitting source host on the basis of the identification tag of the received packet. COPYRIGHT: (C)2003,JPO