This paper presents a simulation comparative study of some recent window-based high-speed TCP protocols (i.e. BIC and CUBIC) in large Bandwidth Delay Product (i.e. BDP) environment. It focuses particularly on long lived TCP transfer. We carry out simulation experiments extending the comparison between BIC and CUBIC [1]. In particular, we highlight further features of BIC and CU-BIC protocols in a lossy network environment. We show also RED AQM incidence on throughput performance. Two sets of simulation studies are conducted. The first one deals with multiplexed high-speed TCP pro-posals of the same kind (BIC or CUBIC) and on the same bottleneck link whereas the second one is concerned with heterogeneous multiplexed high-speed TCP propos-als (BIC and CUBIC). Throughput behaviors of different high-speed TCP’s under different configurations are high-lighted with respect to network loss rate for Drop Tail (i.e. DT) and RED policies under Markovian and non Markovian loss distributions. We evaluate furthermore RED AQM algorithm impact both on link utilization and link bandwidth share between competing high-speed TCP proposals. Although the design and conception of each new proposal is achieved in order to enhance features such as scalability, friendliness, fairness and stability, we show, in this work, that this may not be done without some un-avoidable drawbacks. For further information, please visit this web site.