Is tampered-TCP really effective for getting higher throughput in the Internet?

This paper examines the effectiveness of tampered-TCP whose congestion control mechanism has been modified by malicious users for higher than the normal TCP throughput. In this paper, We focus on a tampered-TCP in which the increase and decrease ratio of the congestion window size were changed during the congestion avoidance phase. The performance of the tampered-TCP was examined based on a mathematical analysis and simulation given the coexisting of tampered-TCP and TCP Reno connections in the network. The following characteristics of the tamperedTCP were found: (1) when the increase ratio is larger than 2 packets per RTT, the throughput is significantly degraded due to many timeouts; (2) lowering the decrease ratio is effective for the throughput improvement; and (3) the effectiveness of lowering the decrease ratio is less than the illeffects encountered when the increase ratio is augmented. We conclude that the tampered-TCP would self-destruct in many parameter regions, and there is few situation where the tampered-TCP obtains much higher throughput.