In this in-class assignment, we will use a command-line utility called traceroute to view the networks that a packet crosses as it travels the network from your computer to some popular websites.
To use traceroute, open up the command prompt on your computer. You can click start and type cmd in the “start search” dialog box.
At the prompt, enter the command tracert followed by the URL of a website you want to trace. In the example of Figure 1, we use tracert to trace a route from our computer to the website of the Illinois Institute of Technology (www.iit.edu). Each row in the output has ﬁve columns. The ﬁrst column is the serial count of the routers encountered in the path to the destination. This gives us a count of the number of hops required to reach the destination. The next three columns provide the round trip times (milliseconds) for three probe packets sent to the router at the location.
The last column gives us the name or numerical address of the router reached on the hop. For example, the router on the 7th hop in your assignment cab be rtr.chic.net.internet2.edu. Many ISPs give routers meaningful names that help network administrators quickly identify the location of the router on a map. For example, the jax in the router indicates that it is located in Jacksonville and the tlh in the router indicates that it is located in Tallahassee, Florida.
The router names also indicate the networks the routers belong to, so that the names of the organizations operating the routers can be easily checked on the web. For example, flr indicates that it belongs to the Florida Research and Educational Network, as can be checked by visiting the website www.ﬂrnet.org.
Figure 2 shows another route trace, this time to the University of Oxford. We see that the packets take the path from FAU → ﬂrnet → rtr → geant.net → janet.uk → U. Oxford.
The geographic names of the routers in Figure 18 also indicate the geographic path taken by the packets. Starting from the East Coast of the United States in Boca Raton, the packets travel via Jacksonville and Abilene, UK. In UK, the geant.net routes packets to the University of Oxford. Hops 17-20 are within the University of Oxford as the packets take many small hops within the university to reach its web server.
When packets cross submarine routes (e.g. hops 8), they typically encounter relatively larger delays because of the longer distances that need to be covered. Delays may also be caused when the network on a hop is very busy handling other trafﬁc.
1. Brieﬂy describe what traceroute does and how it is useful.
- Traceroute is a way to follow the route of packets to destination host from our server. This is useful for someone to see how fast the route travels and to see the different areas that it goes through.
2. Use traceroute to trace the route from FAU to Stanford University (www.stanford.edu). Show the traceroute