Evaluation on stability enhancement of parallel downloading

While traditional downloading programs usually select one mirror server for retrieving a file, it is more effective to select several mirror servers and to fetch different parts of the same file from the servers in parallel from the viewpoints of downloading time and fault-tolerance of network service. We have already proposed an adaptive parallel downloading method that enables us to stabilize and accelerate the downloading time even if the network offers a wide variety of bandwidths. This paper describes several improvements on our original method to enhance its stability. We have investigated suitable parameters for the improvements, which can adapt to the network conditions. The parameters are a throughput ratio of the smallest to the total and a performance deterioration ratio of each link. Practical experiments that focus on downloading speed and stability of downloading time confirm that the improved method is more effective than both our original method and the typical existing method.