Improvements on block size control method for adaptive parallel downloading

Although the traditional downloading programs usually select one server and retrieves a file from the server, it is more practical to select more servers (e.g. mirror servers) and to fetch different parts of a file from the servers in parallel from the point of view of downloading time and fault-tolerance of network service. We have already proposed an adaptive parallel downloading method, which enables us to stabilize and accelerate the downloading time even in the network environments with various bandwidths. Since we found a little room for improvement in the method, this paper describes an improved method. The new method has the following features: (1) independence of the number of mirror servers and (2) introduction of request pipelining into parallel downloading. Based on practical experiments from the viewpoint of downloading speed and stability of downloading time, we confirm that the improved method is more effective than the previous methods. There is a possibility that the improved method become one of the most important network control technologies for network assurance.