Conventional TCP is window based, which exploits the sliding window mechanism to conduct the flow control. It increases the sending window additively and decreases the sending window multiplicatively in response to successful transmission and, packet loss/timeout events respectively. While the mechanism works quite well in normal networks, TCP can hardly reach the ideal bandwidth utilization in long fat networks (LFNs) due to long delay and bursts of packet losses. Besides, as wireless and mobile computing has become popular today, packet loss in such networks may occur due to noise, interference and handoff across different domains. TCP could not react to different situations effectively as it sees all packet losses as an indication of network congestion. In this thesis, we proposed a new transmission control mechanism called Active Rate Anchoring TCP (ARCH-TCP). In ARCH-TCP, we explicitly integrate bandwidth measurement into TCP to solve the aforementioned problem. Specifically, we exploit packet-pair measurement to quickly estimate bandwidth share and then RTT variation is observed to compensate measurement error. We built the model in J-Sim network simulator to evaluate the effectiveness of our proposal. We found that ARCH-TCP can react to network conditions quickly and precisely in both wired and wireless networks and both in the normal networks and LFNs.