On inferring TCP behavior

Most of the traffic in today's Internet is controlled by the Transmission C ontrol Protocol (TCP). Hence, the performance of TCP has a significant impa ct on the performance of the overall Internet. TCP is a complex protocol wi th many user-configurable parameters and a range of different implementatio ns. In addition, research continues to produce new developments in congesti on control mechanisms and TCP options, and it is useful to trace the deploy ment of these new mechanisms in the Internet. As a final concern, the stabi lity and fairness of the current Internet relies on the voluntary use of co ngestion control mechanisms by end hosts. Therefore it is important to test TCP implementations for conformant end-to-end congestion control. Since we b traffic forms the majority of the TCP traffic, TCP implementations in tod ay's web servers are of particular interest. We have developed a tool calle d TCP Behavior Inference Tool (TBIT) to characterize the TCP behavior of a remote web server. In this paper, we describe TBIT, and present results abo ut the TCP behaviors of major web servers, obtained using this tool. We als o describe the use of TBIT to detect bugs and non-compliance in TCP impleme ntations deployed in public web servers.