中文摘要：

针对FASTTCP存在难以选择协议参数的公开问题，根据FASTTCP单边加速应用的特点，提出了一种改进的2层结构的传输层算法。用此算法时，在下层，记录各活跃的FASTTCP连接小时间尺度收集最大排队延时等历史信息，上层算法充分利用历史连接能够提供的最大排队延时等信息，确定目标排队延时的控制范围，大时间尺度周期动态调整协议参数，通知给下层运行的FASTTCP连接，主动控制瓶颈链路的队列长度，避免

英文摘要：

Aiming at the open problem that it is difficult for FAST TCP to choose proper protocol parameters, a novel improved two-layer algorithm for the transport layer is proposed according to the application characteristics of unilateral accelerated FAST TCP systems in the paper. It is described below. In the lower layer, the history information of the active FAST TCP flows, such as the maximum queue delay, is recorded at the small time scale period. By making full use of the history information provided by the lower layer, the range of target queuing delay is obtained and the proper protocol parameters of the FAST TCP flows are dynamically tuned by the upper layer algorithm in the large time scale. So the queuing length of the bottleneck link is actively controlled and the queue overflow problem is solved. It is proved by the NS-2 simulation results that the stability and utilization can be improved while this im- proved two-layer algorithm is used.