In the future Internet, hierarchically classified Quality of Service (QOS) controls will be effective because various connections requiring different QOS are mixed. However, even in such an environment, among the same class connections, performance protection to harmful impact from the other connections and quality differentiation between connections will be required furthermore. In this paper, from this point of view, we focus on the active connections succession time (age of active connections) as a new dimensional criterion for buffer controls. To be concrete, the packet discarding control of congested router's buffer based on active connections is proposed. Moreover, its performance is evaluated through TCP/IP level simulation from the viewpoint of file transfer time. Conventional Internet can be regarded as the environment where only one class traffic exists (unit class environment). The proposed control scheme can provide powerful differentiation capability to avoid the performance disruption of total connections even in the conventional Internet.