In this chapter, you learned that latency is the delay caused by the time it takes messages to travel over network media from one place to another. This concept is easy to see in the real world, where it takes longer to travel across the country than it does to go to the grocery store. Even though network messages travel much faster than a car or even a jet plane, it still takes time for them to get from one place to another.

You might find this site useful to for this project: https://whois.icann.org/en/lookUP?name

If some sites dont work, try to find another site in the same country that might work.

Lets do a little experiment to see how distance affects a messages RTT (round trip time).

Open a command prompt and run tracert on a Web site whose servers are located on a different continent from you, across one ocean. If youre located in the Midwest or Eastern United States, for example, you can run the command tracert www.london.edu (London Business School). If you are on the West Coast, however, you might get more useful results for this step by targeting a server across the Pacific Ocean, such as tracert www.tiu.ac.jp (Tokyo International University).

Examine the output and find at what point in the route messages started jumping across the ocean. By what percentage does the RTT increase after the jump compared with before it? You can see an example in Figure 5-55, page 269.

To calculate the percentage for this jump, you would select a time from just after the jump (126, for example) and divide it by a time from just before the jump (such as 45), then multiply by 100%. In this case, the sample data would yield a 280% increase. It takes nearly three times as long for a message to go round trip across the Atlantic from the United States to Manchester, England (the location of this first European router) as it does for a message to travel round trip between two servers that are both located on the U.S. East Coast (this local computer and the last U.S. router in the route).

Choose a Web site whose servers are on a continent even farther away from you. For example, you could trace the route to the University of Delhi in India at the address du.ac.in. How many hops did it take until the route crossed an ocean? What other anomalies do you notice about this global route?

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Choose one more Web site as close to directly across the globe from you as possible. U.S. locations may want to use the University of Western Australia at uwa.edu.au. How many hops are in the route? Did the route go east or west around the world from your location? How can you tell?

[answer] 16 hops,

Scott Base in Antarctica runs several webcams from various research locations. Run a trace to the Scott Base Web site at antarcticanz.govt.nz. Is this Web server located in Antarctica? How can you tell?

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Think about other locations around the world that might be reached through an interesting route. Find a Web site hosted in that location and trace the route to it. Which Web site did you target? Where is it located?

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Try the ping command on several of these same IP addresses. Did it work? Why or why not?

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