Design and Performance Evaluation of Distributed Active Queue Management Mechanism Cooperating among Multiple Routers

In recent years, AQM (Active Queue Management) mechanisms, which control the number of packets in the router’s buffer by discarding an arriving packet, have been actively studied. In past studies, most of AQM mechanisms have been designed by taking account of a single router; i.e., few AQM mechanisms have been designed by taking account of multiple routers in the network. In a general network with multiple routers and heterogeneous TCP connections, it is known that the bandwidth allocation to TCP (Transmission Control Protocol) connections satisfies F A fairness criterion. This means that the throughput of TCP connection tends to be high when its propagation delay and/or the number of its traversing links is small. In this paper, we focus on such a general network, and design an AQM mechanism that cooperates with other routers for improving the fairness among heterogeneous TCP connections. In our AQM mechanism, ECN (Explicit Congestion Notification) mechanism is used for differentiating the packet marking probability of RED according to CE (Congestion Experienced) bit of an arriving packet. We analyze the steady state behavior of our proposed AQM mechanism, and show that the fairness among TCP connections is improved compared with the RED router.