comment marche Internet

Durée estimée: 45 minutes

Text Version


This lesson goes more deeply into the infrastructure and mechanics of the Internet. It explains packet switching, TCP/IP and the protocol hierarchy, as well as IP addresses and domain names.


How the Internet Works, Part 1

Activity 1 - Using Ping to Test the Reachability of Internet Hosts

The has free interactive tools that can be used to observe packet routing, latency time, and other Internet statistics. Just choose the tool you want to use from the navigation bar on the left.

Ping tests whether a host computer is reachable by repeatedly sending data packets from the server in Dallas, TX to the host computer.

  • For each of the following servers, write down the average round trip time (RTT):,,,
  • Some questions to discuss:
    • Did any of the servers lose packets?
    • Are you able to find a server that has a really long RTT or does lose packets?

Activity 2 - Using Traceroute to Observe How Packets are Routed

Traceroute lets you trace the route from the server in Dallas, TX to some destination server.
  • Use Traceroute to identify the IP addresses and trace the routes to the following host computers:,,,
  • Use the Monitis Traceroute tool to measure the average latency between various servers on the Internet. How much time and how many hops do the following routes take:

How the Internet Works, Part 2

Activity 3 - Packet Sniffers & Public Networks

Watch this video that describes how a hacker could view your data on a public network using a packet sniffer. Discuss with your classmates when and where you use public networks, how you use the Internet on them, and how you might protect your data.

How the Internet Works, Part 3

Activity 4 - Lookup Domain Names & IP Addresses

Using the tools below, try looking up the IP addresses for various websites, including their subdomains. Do you see any patterns? Now look up your school's domain name and IP address, and then the IP address for your computer or mobile device. Do you see any patterns?

  • - find the IP address for a given host name
  • - find the IP address of the device visiting the website
  • What's my IP? - mobile version
  • Possible searches: 1),; 2),; 3),


Here is a table of some of the technical terms discussed in this lesson. Hover over the terms to review the definitions.
adresse IP
nom de domaine
commutation de paquets
sniffeur de paquets
couche d'abstraction
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An IPv4 address ____________________.
Choose all that apply.
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True or False: The main difference between circuit switching and packet switching is that in circuit switching data is broken up and sent in parts and in packet switching data is sent out on a continuous circuit.
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The Domain Name System __________________.
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True or False: For every packet of data sent over the Internet, there is only one route it can take to reach its destination.
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When you send an e-mail message using Gmail in your browser or using the Gmail app __________________.

Sample AP CSP Exam Question

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According to the domain name system (DNS), which of the following is a subdomain of the domain

Still Curious

There is a wealth of good introductory and comprehensive information about the Internet and the WWW.

Reflection: For Your Portfolio

Create a page on your portfolio named How the Internet Works? under the Reflections category of your portfolio and answer the following questions:
  1. What are ping and traceroute? How does each work?
  2. What are the benefits of packet switching?
  3. What is the TCP/IP Model?
  4. What are packet sniffers? Why is it important to protect your data when using public wifi connections?
  5. What is the difference between IPv4 and IPv6? Why have we shifted to IPv6?
  6. What is the link between IP addresses and domain names?