HTTP performance analysis over multi-hops satellite communication system

In order to provide a long distance communication such as the one between two nodes separated by about halfway around the earth, a multi-hops satellite communication system which goes through multiple satellites is attractive. Furthermore, in case of disasters, the system is useful as the alternative to submarine optical fiber links. HTTP1.1 (HyperText Transfer Protocol version 1.1) is one of the most popular protocols for obtaining files. However, the performance of HTTP1.1 on such multi-hops system has not sufficiently evaluated. Therefore, we evaluate Web data transfer time based on HTTP1.1 over the multi-hops satellite communication system. Firstly, we propose new formulas to evaluate the performance of both HTTP1.1 and pipelined HTTP1.1. Secondly, the calculation results derived from these formulas are compared with the experimental ones based on the SKYCAST system, which is one of the multihops satellite communication systems. As a result, in case of pipelined HTTP1.1, the comparison shows that the values based on the evaluation formula are close to those from the experimental results. However, we observed that the formula for HTTP1.1 with no pipeline underestimates the transfer time. Therefore, we have carefully investigated the data sequence using the output of tcpdump command. Based on the investigation, we have modified the proposed formulas. Consequently, it is clear that the improved formula well predicts the experimental results.