The present invention is comprised for pre-setting bandwidth control information of each user for each of the number of normal physical links which are integrated as a Link Aggregation, recognizing the number of currently normal physical links if a failure, or recovery therefrom, of a physical link which is integrated as the aforementioned Link Aggregation, and carrying out a bandwidth control, for each user traffic, corresponding to the number of the recognized normal physical links by referring to bandwidth control information of each user for each of the number of preset normal physical links, in order to prevent an occurrence of unfairness in usable bandwidth among the users even in the case of a failure occurrence in respective physical links which are logically integrated as a Link Aggregation.