Transmission Control Protocol (TCP) is a widely used end-to-end transport protocol in the Internet. However, the congestion control of standard TCP (Reno) functions poorly in high speed networks because of its slow response with large congestion windows. Therefore, standard TCP may become the performance bottleneck as the bandwidth of Internet continues to grow. In this paper, we propose a new variant of hybrid TCP, Concave Convex TCP (CCTCP), to overcome this issue. CCTCP revises Reno's congestion avoidance phase by appending delay-based features. Through ns-2 based simulations we find that, as compared to other hybrid TCPs, CCTCP can achieve a high performance with minor dependence on bottleneck buffer sizes under a variety of network bandwidths, especially in high speed networks.