TCP Testsuite performs in-depth analysis of your path of connectivity to the Internet, focusing on the interference of middleboxes (NATs, proxies, firewalls) with TCP traffic.It is part of a research project to find ways of extending the TCP protocol in a way that works on today's complex network infrastructure that does not always behave in standard or expected ways. TCP Testsuite forms part of a survey of the diversity of the widely used networks to inform further development of the TCP protocol and extensions.The tool is developed at the University of Cambridge.