After the presence of high Bandwidth-Delay Product (high-BDP) networks, many researches have been conducted to prove either the existing TCP variants can achieve an excellent performance without wasting the bandwidth of these networks or not. In this paper, a comparative test-bed experiment on a set of high speed TCP variants has been conducted to show their differences in bandwidth utilization, loss ratio and TCP-Fairness. The involved TCP Variants in this experiment are: NewReno, STCP, HS-TCP, H-TCP and CUBIC. These TCP variants have been examined in both cases of single and parallel schemes. The core of this work is how to evaluate these TCP variants over a single bottleneck network using a new parallel scheme to fully utilize the bandwi...