Implementation and Performance Evaluation of TCP Extensions in FreeBSD

TCP is the most widely used transport layer protocol and is used in a big range of ap-plications. Understanding its behavior, is critical in order to properly engineer, operate, and evaluate the performance of the Internet, as well as to properly design and implement future networks. It aims into providing fast and reliable communication over an unreli-able network such as the modern Internet. In order to achieve that, it is equipped with a number of mechanisms that allow it to recover from losses etc. How fast a transmission is done, meaning how fast all bytes available for transmission from a sender to a receiver are sent is very important. This thesis explores two extensions of standard TCP that aim into decreasing the time needed for data transmission. The first one is the Proportional Rate Reduction (PRR) [DMCG11], an algorithm proposed as an alternative to the standard Fast Recovery algorithm of TCP, used for loss recovery. PRR addresses all the weaknesses that the standard algorithm has. The second extension that is explored is New Congestion Window Validation [FSS13], a method that improves TCP performance for rate-limited traffic. This traffic is produced by applications, which do not use the entire bandwidth available to them by TCP. An implementation for each extension was done in the TCP/IP stack of the FreeBSD kernel. Their performance was evaluated. The results show that the transmission time is lowered for all the scenarios that have been evaluated. The results for each extension are presented at the respective section of each chapter.