Lab Exercises

Lab 1

This lab consists of analyzing several TCP packet traces. These traces were collected using tcpdump and demonstrate various TCP behaviors.

For each trace perform the following analysis:

1. Process the trace with tcptrace. This will produce a set of output files for use with xplot.
2. View the output files with xplot.
3. Find the minimum and typical RTT for each connection. This does not have to be precise.
4. Find the average bandwidth utilization of the connection.
5. Attempt to estimate the bandwidth available to the connection.
6. Identify TCP performance problems with this connection, and think about possible improvements to fix these problems.

In order to do this exercise, you will need to log in to one of the NetBSD lab workstations. Use ssh to connect from your NT workstation to the NetBSD machine. You will have an account on each of the 14 workstations; choose one at random. (Try to spread out). The traces for this exercise are located in /usr/local/traces. The tools are located in /usr/local/bin, which should be in your path.

For help on tcptrace, try tcptrace -h.

tcptrace -G trace_name
will produce a full set of plots for a given trace.

xplot xplot_file
will plot the output. You will need to set your X DISPLAY environment variable to point to your NT workstation in order to view the plots.

You can zoom xplot by using the left mouse button to select a region. Clicking the left button unzooms one level. Middle button drags/scrolls the plot. Right button exits. Shift-Left-button produces a .PS file which you might be able to print.