6.8 Activity 5
The aim of this activity is to give you a personal feel for the technology of IP addresses and packets in action.
This activity will help you to:
see the unique IP address assigned to your computer when you are logged onto the internet;
look at a server which traces the route taken by a packet sent from your computer to another on the internet;
conduct a small experiment to see how long it takes to get a packet from your computer to others elsewhere on the internet.
There is some software that can provide a fascinating graphical illustration of the route taken by test packets during transmission from one end of a TCP/IP network to the other (in other words, from your computer to a chosen destination). This service is provided by Traceroute Web servers. You are going to connect to one and see what information you can find about the route taken by packets of information transmitted across the internet.
The one I want you to try is a particularly easy-to-use service providing a clear graphical traceroute – the VisualRoute server in Richmond, Surrey.
Connect to the VisualRoute server.
Note: when you use this service for the first time you have to register. There is no cost involved.
When you connect to the VisualRoute server website, the IP address of your own computer is displayed in the (to) box. It is a numeric address such as ‘18.104.22.168’. This is the unique internet address currently assigned to your computer. No other computer on the Net can have this address, and when you send out a packet, the IP layer in your TCP/IP stack places this number in the ‘Source Address’ field in the header which it places on the packet. Make a note of the IP address of your computer.
Note: If you have time, it would be worth repeating this activity the next time you log on to your computer. You may find that your computer now has a different IP address rather than a static one. Most ISPs have a batch of IP addresses assigned to them, and their server allocates addresses from this batch as computers dial in.
Next, click on the start button beside the box with your IP address in it.
The software then analyses your connection to the VisualRoute server. Clicking on the “Summary”, “Table” and other tabs gives you a range of useful information on your connectivity including:
the number and IP addresses of all the separate computers involved in passing on the test packets to their eventual destination;
the percentage loss of information;
the locations of the various nodes and networks involved ;
the time in milliseconds for each ‘hop’;
a map showing the route of the packets across the world.
Now enter the URL of a website in the UK or USA to which you would like VisualRoute to send test packets (for example, the New York Times server would be entered by typing ‘www.nyt.com’) and click on the start button to the right of the url entry box. The software analyses VisualRoute’s connection to the chosen website. This information can be accessed by clicking on the “Summary”, “Table” and other tabs as before.
If you have the time and inclination, it would be worth repeating this activity at different times of the day, especially early in the morning UK time (before the USA goes to work) and mid-afternoon in the UK (when the USA is busy). Compare the time taken and any differences in the routes used.
You could also repeat the process for other addresses across the world, or for a target address in the UK, such as the Open University or the BBC.
Note: The VisualRoute utility was tested and found to work in Microsoft Internet Explorer version 6. It did not work with the Firefox browser version 3.0.5”
6.7 The importance of end to end
6.9 Summary and SAQs