Protocol architecture of high speed TCP/IP service over international ATM network

TCP/IP based data communication is one of the most promising applications in wide area ATM services. However, it is noticed that TCP becomes the throughput bottleneck over an international ATM network with large propagation delay. The major reason for this problem is that TCP performs window based flow control and the maximum value of the window size is limited by 64 kbytes. Against this problem, we proposed a high speed TCP/IP service using a TCP gateway, where a pair of TCP gateways are introduced in international ATM networks, and each of them works as an intermediate system along a TCP connection. They improve the TCP throughput by introducing a link-by-link flow control and a sufficient window size between the gateways, without any modifications to end terminals. In the design of a TCP gateway, we have also taken account of the mechanisms avoiding the performance degradation due to transmission errors and congestion. In this paper, we describe the protocol architecture of the TCP gateway and its performance by comparing with conventional TCP and TCP with window scale option. The results of performance evaluation show that the TCP gateway can provide more than 20 times higher throughput than conventional TCP, and that it can attain higher performance in the sense of throughput and fairness than the case where TCP with window scale option is used in customer terminals