A Closer Look at the Behavior of the Congestion Window in TCP

By: Leslie Raju Cherian
 

Introduction:


We chose the project "ST.IP  Internet Protocol (IP)" wherein we are to ensure that
Linux complies with the IP standards set forth by the Internet Engineering Task
Force (IETF). Our goal in this project is to develop a framework for tracking the
behavior of TCP?s congestion control algorithms in the Linux kernel. We found that
most aspects of TCP behavior are visible in traces of network activity that can be
captured with network protocol analyzers like Ethereal. However, many of the kernel
variables that track congestion control, such as snd_cwnd and rto, are not directly
visible in these traces. We will be modifying the Linux kernel to print out the
values of important congestion control variables along with other information that
will allow us to correlate changes in congestion control with the network activity
seen in Ethereal traces. We will run a set of tests to find out which kind of
algorithm is implemented in the latest versions of Linux to compute the
retransmission timeout value. We also want to find out which congestion window
algorithm is being followed. Moreover, we would like to elucidate how the congestion
window values change in the case of timeouts, packet loss or successful packet
transmission.