Analysis of TCP Connection Performance Using Emulation of TCP State

Transmission Control Protocol (TCP) is still used by vast majority of Internet applications. However, the huge increase in bandwidth availability during the last decade has stimulated the evolution of TCP and introduction of new versions, better suited for high speed networks. Many factors can influence the performance of TCP protocol, starting from scarcity of network resources, through client or server misconfiguration, to internal limitations of applications. Proper identification of the TCP performance bottlenecks is therefore an important challenge for network operators. In the paper we proposed the methodology for finding root causes of throughput degradation in TCP connections using passive measurements. This methodology was verified by experiments conducted in a live network with 4G wireless Internet access. The paper also presents selected details of its practical implementation.