TCP performance emulation for lossy communication channels

This thesis examines the performance of TCP on a lossy wireless link. The performance is analyzed for uniformly distributed and correlated packet error processes. The dynamic process of error generation and injection is implemented using exchangeable Linux kernel modules. The TCP kernel variables are accessed using the web100 kernel patch and associated tools. This allows evaluation of TCP dynamics through the inspection of congestion window as it varies with time. The average times taken to detect and to recover from a packet loss is measured. The effect of the time-correlated bit errors on the TCP dynamics is studied using the Gilbert-Elliot model. The use of measured TCP parameters to detect the time instance of the next packet loss and the average packet error rate is presented. The changes in dynamic behavior allow determination of a critical packet error rate. This feature is demonstrated and analyzed with respect to the relative frequency of timeouts and onset of fast-retransmit and fast-recovery mechanisms.