COSC 4377 - Introduction to Computer NetworksSpring 2012MW 1:00-2:30pm at PGH347
Homework 10 : Understanding the Internet PathsDue: midnight April 11, 2012In this assignment, we will study the quality of paths in the Internet. Often we are interested in knowing how long it takes to send data from one machine in the Internet to another, e.g., a web server to a client that wants to browse the site. We will learn how to measure latency between machines in the Internet, visualize the latencies, and make recommendations for service placement based on the information we collect. Although bandwidth of a path is also an important metric, we will focus exclusively on latency in this assignment. Latency is more important than bandwidth in interactive online applications that do not transfer a lot of data. Measuring LatencyWe can use the "ping" command to measure the RTT between a machine on which you are logged in to an arbitrary host in the Internet as long as that host replies to ping messages.Here is an example of using ping to measure RTT: $ ping www.google.com PING www.l.google.com (74.125.227.112): 56 data bytes 64 bytes from 74.125.227.112: icmp_seq=0 ttl=51 time=22.235 ms 64 bytes from 74.125.227.112: icmp_seq=1 ttl=50 time=21.460 ms 64 bytes from 74.125.227.112: icmp_seq=2 ttl=51 time=23.291 ms 64 bytes from 74.125.227.112: icmp_seq=3 ttl=51 time=23.881 msIn the example above, the first line is the command. Rest of the lines are output from the ping command. We can see the first RTT is 22.235ms, second one is 21.460ms, etc. We collect a number of these measurements, and report the mean latency as the latency between the host in which we ran ping and www.google.com. Depending on your platform, the output of ping command might be slightly different. Participant MachinesThere will be 20 machines available to you for approximately 10 days. In the meantime, you can prepare your scripts and commands on bayou. While on bayou, you can run ping commands to 127.0.0.1 or localhost and "pretend" they are different machines for testing your methodology.
Questions
SubmissionAll the answers to questions should be in a single pdf, no longer than three pages in length. You should also include latencies.txt in your submission. If you wrote custom scripts/programs in this assignment, please include the source. Put all the files into a folder with the name: uhid_hw10, where uhid is the prefix of your .uh.edu email address. Then, zip the directory and upload the zip file using Blackboard. |