Recent measurement showed that self-similar nature is found not only in network traffic volume but also round trip packet delay. In this paper, we discuss three issues of the self-similarity of round trip time (RTT), which is one of the most important parameters to determine TCP throughput performance. First, we discuss the origin of the packet delay self-similarity. A recent study anticipated that the queueing delay of self-similar traffic is the reason for packet delay self-similarity. With computer simulation, we evaluate the correlation between traffic and RTT self-similarity. Next, we investigate the impact of RTT self-similarity on TCP throughput performance. Computer simulation results show that RTT self-similarity gives high variability to file transfer time. Finally, we investigate the impact of RTT self-similarity on RTO (Retransmission Time Out). We discover that the bigger the Hurst parameter of RTT is, the more frequent unnecessary timeouts occurs. Furthermore, we propose a new RTO calculation algorithm to improve these unnecessary timeouts.

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