4. Internet

Internet experiments


As already mentioned in the video, shipping takes place in so-called parcels. But how does this parcel shipping work? Is it handled by DHL, Hermes or DPD? (#dadjoke)

Of course, you know that no logistics company is responsible for shipping the parcels, but it is precisely this parcel shipping on the Internet that we now want to analyze in more detail.



 

The traceroute program

Every computer has a small program that records the path of an Internet request: traceroute.

In order to use traceroute you have 2 options:

  • You use a Webversion of traceroute like for example https://gsuite.tools/de/traceroute (recommended)
  • You are using the version installed on your computer of traceroute.



!     Choose a version of traceroute and follow the description to make your first traceroute request.

Note: Use the version on your computer

In order to use traceroute you have to open the Command line input (or Shell or Terminal). If you do not know how this works, you can follow the relevant instructions for your operating system.

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Mac OS

Open Spotlight (press CMD+Spacebar simultaneously) and search for terminal.app. Confirm with Enter or open the displayed program.

 

Windows

Select start or the Windows icon and input cmd (short for command) or command prompt . Confirm with Enter or open the displayed program.

 

Linux

Search for Terminal in your application menu. In the popular Linux distribution Ubuntu, a terminal can also be opened with the key combination Ctrl+Alt+T.

_____________

 

After you have opened the command line, enter

in the command line and confirm your entry with Enter. 
Instead of www.google.de you can also request other so called hostnames. 
The host name is the unique designation of a computer within a network.
Try for example www.wikipedia.de, www.fau.de oder www.facebook.com.

Hint: Use the web version

Enter a host name such as www.fau.de or www.google.de in the Host (Domain/IP) field. The hostname is the unique designation of a computer in a network.

Please note: All web tool requests are started here from London. If you were to execute the same request from your computer, a different route would result.


EXERCISE 1

!     How many stations does your request need of www.fu-berlin.de or www.northwestern.edu?

Possible solutions (to compare)

The IP numbers are addresses of computers around the world on the Internet (something like telephone numbers). The data packets virtually jump from one computer to another. It's quite exciting to see how many computers your packets travel through to reach their destination.

Our request for www.northwestern.edu for example looks like this:

 

Hint: * respectivaly. ***
Lines in which there is no information, just one (*) or three stars (* * *) are not unusual.

They indicate that a time limit has been exceeded. Do not let this unsettle you.
But: Stations from which no response was received are of course not displayed on the map in the web tool.

If this happens, try to start the request again. If this does not help either, try a different host name.



 EXERCISE 2

Hint for the solution
The routes do not have to be identical. It can of course happen that the same route is chosen several times. However, this is not generally the case. Depending on the utilization of a path or similar, the packages can take different routes. Try your request to www.google.de again (and check all stations, including the last one wink)

Hint for the solution
Depending on the current network utilization or availability, the selected route may not always be the geographically closest option. Perhaps a country is better connected via a third country that is not on the route.

Try: vhportal.ceniai.inf.cu (Cuba), www.mfa.gov.il (Israel), www.fu-berlin.de (Germany) or www.supremecourt.gov.np (Nepal)


Experiment with traceroute

!     Experiment a little more with the Internet by using traceroute. Below you will also find a few tips. Have fun!

Note: Interpreting the output of traceroute
Traceroute determines via which stations packets reach the queried computer (also the last in the list).

A request traceroute www.fau.de gives us the following result, for example (your result will be different!):
> traceroute www.fau.de
  1     3 ms     2 ms     3 ms  fritz.box [192.168.178.1]
  2     9 ms     9 ms    10 ms  loopback1.0002.acln.01.ber.de.net.telefonica.de [62.52.201.185]
  3    10 ms     9 ms     9 ms  bundle-ether16.0004.dbrx.01.ber.de.net.telefonica.de [62.53.2.94]
  4     9 ms     8 ms    10 ms  ae2-0.0001.prrx.01.ber.de.net.telefonica.de [62.53.11.127]
  5    11 ms    10 ms     9 ms  dfn.bcix.de [193.178.185.42]
  6    18 ms    14 ms    14 ms  cr-lap1-be8.x-win.dfn.de [188.1.144.25]
  7    19 ms    19 ms    18 ms  kr-erl74-6.x-win.dfn.de [188.1.237.202]
  8    21 ms    18 ms    18 ms  constellation.gate.uni-erlangen.de [131.188.20.95]
  9    22 ms    18 ms    18 ms  prime.gate.uni-erlangen.de [131.188.10.27]
 10    19 ms    19 ms    18 ms  zuvcmslb.rrze.uni-erlangen.de [131.188.16.209]
The output of traceroute is made up of 3 components:
  • As a rule, three packets are sent to each computer. The three values displayed in milliseconds indicate the response time to these three packets (e.g. 3ms 2ms 3ms).
  • fritz.box oder dfn.bcix.de sind hostnames.
  • We will see later what the number sequences such as 192.168.178.1 are all about!
The various computer networks are also clearly recognizable. First of all, our route takes us via our router, in this case a Fritzbox. Router is simply the name for a computer that forwards information between different networks (in this case your local home network and the Internet).

The request then went via several telefonica computers (telefonica is an Internet service provider) and DFN computers (DFN stands for the German Research Network) to FAU computers.
Hint: Possible hostnames

Here are a few suggestions: