A control condition is automatically generated by using a discovery domain managed by an iSNS server as a network communication quality control unit and set in a network device. Thus, it is possible to realize communication whose quality is effectively controlled in storage data transmission. A network configuration server automatically acquires discovery domain information which groups a host and a storage apparatus managed by a name management server. The network configuration server sets a flow identification condition so as to identify the flow per discovery domain according to the information acquired, assigns a service class performing a control of quality of communication service to the flow, and sets transmission rule for the service class to routers.