In view of the connection of a home network to an external network via a home router, using a mechanism that access from the same network is provided with a source MAC address whereas a source address field is rewritten to a MAC address of the router in the case of external access via the router, whether or not access is made from the home network is automatically identified by comparing a MAC address of a device on the other side of communication with a MAC address of the home router. It is capable of suitably managing so that a client terminal uses the contents legitimately acquired on a home server within the scope of private use allowed by the copyright law.