Abstract: In an encryption communication system, an encrypt key ID of an encrypt apparatus appearing on a communication path between terminals is acquired by using a key seek packet, and an encrypt key ID is automatically learned based upon a key seek response packet for notifying the acquired encrypt key ID. As a result, communication data between the terminals are encrypted/decrypted, transparently relayed, and discarded by the respective encrypt apparatuses. Even when a communication network is made large and complex, the network for the encrypt communication can be readily managed.

Abstract: A VLAN control system is provided, which comprises: a remote access server, connected to a home network in the VLAN having a global network, for controlling communication between any moved terminal and the home network with reference to a management table for indicating a location of each terminal under connection; a remote access client, connected to each remote network, for controlling communication between the remote network and the global network with reference to a management table for indicating a correspondence relationship between each terminal which is connected to the remote network and the home network; and a VLAN management server, connected to the global network, for managing packet transmission and the location of each terminal with reference to a management table for indicating a correspondence relationship between each terminal and the remote access server and for indicating a location of each terminal under connection.