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Cloud computing is becoming commonly used for enterprise systems. Users utilize WAN, the Internet, or a wireless network to access the cloud service. These networks often have large RTT and packet loss ratios (PLR), so if users communicate via TCP widely used for accessing cloud services, the throughput decreases and the access quality of the cloud service deteriorates. Therefore, much TCP acceleration technology has been developed in conventional research. The technology conventionally proposed as RADIC-TCP [1] controls the retransmission using negative acknowledgement (NACK) returned from the remote receiver. It also uses a congestion algorithm that detects network congestion on the basis of the change rate of PLR calculated by accumulating the lost segment written in NACK coming from the receiver. When the change rate of PLR is small, the sender judges that temporary loss is caused by the congestion with burst traffic or bit error in the wireless environment and continues to increase the throughput, not decrease the throughput. Thus, this technology can improve the utilization ratio of bandwidth without decreasing the throughput excessively. On the other hand, when the change rate of PLR is large, the sender judges that continuous loss is caused by the overuse of bandwidth and decreases the throughput at the gap optimized in accordance with the scale of the network congestion. Therefore, this technology can follow the send bandwidth to the remaining bandwidth exactly while suppressing the excess congestion in the network. In this research, we developed TCP acceleration technology that controls the retransmission using the standard selective acknowledgement (SACK) in order to achieve the communication with normal devices while supporting the congestion control using the same algorithm as conventionally proposed TCP acceleration technology. However, our proposed TCP acceleration technology may not work as intended depending on the occurrence interval of packet losses in real network environments. Therefore, we evaluated this technology's behavior and effect in real network environments. In the evaluation, a smartphone downloaded the data via a wireless network, the Internet, and a Japanese academic backbone network (Science Information Network (SINET)) from a Web server with TCP acceleration technology. In the evaluation using the LTE network with 40ms round trip time, our proposed TCP acceleration technology enhanced the throughput by up to three times. |
