Practical analysis of the stability of TCP

This paper discusses the stability of TCP. More precisely, the stationary behavior of the congestion window process is analyzed based on the measured real Internet traffic (bulk data transfer, FTP of large files). Appropriate algorithm approximating the actual congestion window is presented, and statistical methods to analyze the data are discussed in detail: change-point detection, distribution testing and parameter estimation. It has been shown that the distribution of the congestion window process during stable periods has a bell-like shape and can be approximated by a normal distribution. A number of interesting observations during the study are depicted and explained. Finally, possibilities for building reliable and robust models for the TCP protocol in the future, are discussed.