Estimate round trip time of TCP in a passive way

With the development of Internet, service performance measurement becomes a technical hotspot. In this paper, a passive RTT estimate algorithm (PRE) is proposed to estimate Round Trip Time (RTT) of long-term TCP in the broadband network. Since TCP sender always sends packages belong to the same round together, there is a "gap" between two rounds of sending. PRE can find "gap" between two rounds, and so that call estimate RTT in a passive mode. Base on PRE, passive TCP performance measurement can W deployed in the traffic monitors. Both simulation and practical experiments validate that the algorithm can estimate RTT properly.