A Brief Introduction to Network Utilities and Internet Topology

Due February 06, 2005 23:59 (by CMS if you are listed, by email to Peter, , othewise). 
(Note, please check immediately to see if you are in CMS, and if not please send an email to Peter.)
Also, please subscribe to the course mail-list, which you can do at the following site: cs419 list.
Late answers will be accepted, but with the standard penalty.
You may discuss the websites you discover among yourselves (I can't stop you), but please do the measurements and answer the questions yourselves!

This assignment will use the network utilities ping and tracert. ping requests an echo from a host, and if that host deigns to do so, it will send a reply. ping measures the time it takes to receive the reply. tracert (short for "trace route") uses some trickery to determine the routers a packet is likely to pass through on its way to its destination. Detailed descriptions of these two commands can be found at the following web sites (among many others).

http://www.computerhope.com/tracert.htm
http://www.computerhope.com/pinghlp.htm

These utilities are available on the Windows machines in CSUG lab, via the command line. (Start > Run, type in "cmd").  You may do this assignment from any computer you wish (doesn't have to be CSUG lab).

In answering the following questions, provide the output of the tracert commands (cut-and-paste themf rom the cmd window).

1. The time it takes a packet sent from one host to reach its destination can vary greatly depending on the two communicating hosts. Use the ping utility to find a host (e.g. website) for each of the following round-trip time categories (with respect to your computer, or one in CSUG, etc): 0-10ms, 10-25ms, 25-50ms, 50-100ms, >100ms.  

Based on your observations from question (1), answer questions 2 - 4.

2.  Is there a correlation between geographic location and latency? How strong is this correlation? Give an intuitive reason for this correlation.

3.  Is there much variation in delay from packet to packet?  Is there a correlation between the ratio of fastest to slowest packet for any given ping and the average round trip time for the ping?

4.  Roughly what proportion of the the delays you've observed do you believe are due to propogation delay and how much to other sources of delay? 

5.  Using the ping option that allows you to change packet size, can you determine if any of the delays have a significant bandwidth delay component?

6. Use the tracert utility to examine the path a packet takes to a site. Observe the path for several sites with a (round-trip) latency greater than 100ms. Is there a correlation between the number of hops taken by the packet (i.e. the number of routers it passes through) and the latency? You may need to find more than the three sites from question one to answer this question.

7. For the sites you observed for question six, how is the packet's travel time distributed among the hops it takes? Is one hop responsible for the delay, or does each link take about the same time? Can you find examples of both? (Hint: Yes, you can. Show the examples, and explain intuitively what causes the difference.)

Submission: Write your answers up in a plain text file, and submit it via CMS. Send Peter an email if CS419 is not listed as a course for you in CMS.