Patent ID: 8495223

Claim:
An access control method for use in an access control system in which a plurality of access control apparatuses are connected bidirectionally by a communication network, each of the access control apparatuses including a session-data storage part in which session information on a user terminal is recorded, the access control method comprising the steps of: causing any one of the plurality of access control apparatuses to receive an update request for session information; causing the access control apparatus having received the update request to update the session-data storage part of the access control apparatus having received the update request in association with an update time; causing the access control apparatus having received the update request to broadcast a synchronous update request that requests update of the session information; causing each of the access control apparatuses having received the synchronous update request to update the session-data storage part of the access control apparatus having received the synchronous update request on the basis of the synchronous update request in association with the update time; causing any one of the plurality of access control apparatuses to receive a reference request for the session information; causing the access control apparatus having received the reference request to acquire reference-target session information and the update time thereof from the session-data storage part of the access control apparatus having received the reference request; causing the access control apparatus having received the reference request to send the other access control apparatuses a synchronous reference request that requests reference to the session information; causing each of the access control apparatuses having received the synchronous reference request to acquire the reference-target session information and the update time thereof from the session-data storage part of the access control apparatus having received the synchronous reference request and to send the session information and the update time to the access control apparatus having received the reference request; and causing the access control apparatus having received the reference request to extract the latest session information by comparing the session information and the update time acquired from the session-data storage part of the access control apparatus having received the reference request and the session information and the update lime received from each of the access control apparatuses having received the synchronous reference request, and to send the latest session information as a reference response in reply to the reference request.