MAT 201B / CS 290I--Media Networks and Services
Homework Assignment #2
Due BEFORE CLASS STARTS on Thursday, November 8, 2001

Assignment Overview

The goal of this assignment is to help you understand what is going on in the network by examining exactly what flows across the wire. This is something of a difficult task because network protocol designers have worked so hard to provide so much abstraction to the higher layer applications. Therefore, as a user at the highest layer of the protocol stack, you should be able to see very little of what happens in the network. Never fear though, there are tools that we can use.

Assignment Details

The goal of the assignment is to examine real protocols in use and understand the communication that takes place in a network by examining the bits that flow across a network segment.

For this assignment you will have use your CS UNIX account. (The reason is that Windows does not have snoop capability, but most UNIX operating systems do.) The command is snoop. One problem though: snoop usually requires root privileges to run. Of course, this is a good thing because it should be hard to snoop packets on the network! So, the snooping has been done for you, and a snoop file has been created. Take the hw2.snoop-file.bin.gz file (NOTE: Make sure you download this file, i.e. right click and select ``Save Link As''.) and use it as the source file for snoop (HINT: do a man snoop and look at how to use the -i option... you can do this without having root). You will also want to use some some of the other options that come with snoop to more closely investigate what is happening in this trace. Some of the things going on in the trace will contain protocols we have not gone over in class. You'll have to use one of the class textbooks as a reference to answer them. I will also try to provide some in-class time to answer questions so be prepared to ask questions when the time comes.

This assignment will be graded based on your ability to communicate that you understand everything about the packet trace. This implies, as usual, a clear, concise write-up! To help get you started, I have provided a set of sample questions that you will want to answer about the packet trace. However, these questions only serve as examples of the kinds of things I think are important. They serve as a starting point and are not exhaustive. They are only provided as a guide to help you find the most interesting aspects of the trace. So, how should you proceed? Start by considering the following questions:

Your write-up for this assignment can take any form you like. My suggestion is to be creative (but do not assume that creativity can be used as a substitute for technical thoroughness). First answer the questions and understand what is going on in the trace. Next, create a description of the session filling in the details where appropriate. At a minimum, you should re-order the questions to flow more logically; reduce redundancy (yes, there are some redundant questions); and add questions that you think are important but that I have not included. Try to present the results in a way that provides multiple levels of abstraction. For example, first describe the session, then describe the flows, then describe the packets in the flow. It is also worthwhile to try and draw a network diagram showing the overall relationship of the various hosts.

Assignment Turnin

This assignment is to be done individually, though you may discuss your thoughts and ideas with your classmates.

You only need to turn in a hard copy of your report (due in class), but the assignment must be done entirely in some kind of digital format. Since I will not see the source, you can use anything you want, for example: HTML, Latex, Word, etc.