Abstract: In a storage subsystem which is connected to an IP network, by excluding an improper packet, security is heightened, and a performance of communication to a logical unit of storage subsystem is maintained and secured. In the storage subsystem, a function which carries out filtering of a packet other than an iSCSI packet is provided. With respect to only the packet passed through the function, its accessibility to the logical unit is filtered. Also, traffic of all received packets, and a traffic lob of a packet judged to be discarded by the above filtering is recorded. By using this information, controlling such as a cut-off process of improper communication, QoS securement for normal communication and so on, are carried out.