Recently, networks are rapidly speeding up and multimedia traffic is increasing with the growth in demand of the Internet. Under these situations, routers with the flow-based QoS guaranteed mechanism are desired. Therefore, we have proposed the output buffer control mechanism by flow management and implemented it as a basic hardware design with restricted function. In this paper, the expansion of this mechanism is achieved in correspondence to real networks and the advanced QoS guarantee. The effectivness of this control mechanism is shown by experimentally evaluating the trial production switch equipped with this mechanism under the environment which an actual network was presumed.