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CP1402/CP5631 – Hands-On Activity: Latency Around the World In this chapter, you

CP1402/CP5631 – Hands-On Activity: Latency Around the World
In this chapter, you

CP1402/CP5631 – Hands-On Activity: Latency Around the World
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, for example, for you 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 a jet plane, it still takes time
for them to get from one place to another.
Complete the following steps to see how distance affects a message’s RTT (round trip time):
1. Open a Command Prompt window and run tracert on a website whose servers are located
on a different continent from you, across one ocean. If you’re located in the Midwest or
Eastern United States, for example, you can run the command tracert 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). What command did you use?
2. Examine the output and find the point in the route when 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 5-51.
To calculate the percentage for this jump, you would select a time from just after the jump
(229, for example) and divide it by a time from just before the jump (such as 39), then multiply
by 100 percent: 229/39×100=587%. In this case, the sample data would yield a 587 percent
increase. It takes nearly six times as long for a message to go round-trip across the Atlantic
from the United States to London, 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).
3. Choose a website whose servers are on a continent even farther away from you. For
example, if you are in Australia, you could trace the route to the University of Delhi in India
at the address www.du.ac.in. What command did you use? How many hops did it take until
the route crossed an ocean? What other anomalies do you notice about this global route?
4. Choose one more website as close to directly across the globe from you as possible.
Australia locations might want to use the University at Buffalo at www.buffalo.edu. What
command did you use? How many hops are in the route? Did the route go east or west
around the world from your location? How can you tell?
5. Scott Base in Antarctica runs several webcams from various research locations. Run a trace
to the Scott Base website at https://www.antarcticanz.govt.nz/. What’s the closest router to
Scott Base’s web server that your trace reached? If you can’t tell from the command output
where the last response came from, go to https://www.iplocation.net/ in your browser.
Enter the final IP address to determine that router’s location.
6. Think about other locations around the world that might be reached through an interesting
route. Find a website hosted in that location and trace the route to it. Which website did you
target? Where is it located? What are some locations along the route of your trace?7.
7. Try the ping command on several of these same IP addresses. Did it work? Why do you think
this is the case?

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