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NAF Principles of Information Technology

Lesson 10How the Internet Works

Teacher Resources

Resource Description

Teacher Resource 10.1 Presentation and Notes: How Data Travels the Internet (includes separate PowerPoint file)

Teacher Resource 10.2 Multi-Pass Instructions: How Data Travels the Internet

Teacher Resource 10.3 Bingo Cards: How the Internet Works (separate Word file)

Teacher Resource 10.4 Bingo Game: Terms and Definitions

Teacher Resource 10.5 Quiz: How the Internet Works

Teacher Resource 10.6 Answer Key: How the Internet Works Quiz

Teacher Resource 10.7 Key Vocabulary: How the Internet Works

Teacher Resource 10.8 Bibliography: How the Internet Works

Copyright © 2007–2016 NAF. All rights reserved.

NAF Principles of Information TechnologyLesson 10 How the Internet Works

Teacher Resource 10.1

Presentation Notes: How Data Travels the InternetBefore you show this presentation, use the text accompanying each slide to develop presentation notes. Writing the notes yourself enables you to approach the subject matter in a way that is comfortable to you and engaging for your students. Make this presentation as interactive as possible by stopping frequently to ask questions and encourage class discussion.

This presentation explains how data is packaged to travel across the Internet and how computers that connect to the Internet send and receive the packaged data.

Presentation notes



The Internet is the world’s largest computer network. It is, at the most basic level, a WAN made up of many, many smaller WANs and LANs.

This picture shows an artist’s view of the Internet. Does it remind you of galaxy or star maps you have seen in science classes? It is not hard to think of the Internet, with its millions and millions of connection points, as being a lot like the universe, with its millions and millions of stars.

Image retrieved from http://commons.wikimedia.org/wiki/File:Internet_map_1024.jpg on June 21, 2012, and reproduced here under the terms of the Creative Commons Attribution 2.5 Generic license. Image created using data from The Opte Project.

Presentation notes



Every device on the Internet has an IP address. Think of it like the street address for a house. This address tells data where it should be delivered and also helps track where data has been sent from.

To find your computer’s IP address, click the Windows Start icon and type command prompt in the search box. When the Command Prompt window opens, type ipconfig. In Mac OS X or Linux/Unix, open a terminal window and use ifconfig (or the newer ip addr command).

A computer’s IP address is usually assigned “dynamically” by the router and may change whenever the computer is rebooted. However, computers or servers that host web pages must have a fixed, or strategic, IP address, since the Domain Name Service (DNS) must know where to find the website.

Presentation notes



As this chart shows, data is placed into logical packets that are addressed individually with the destination. This allows multiple messages (packets) to be turned into one coherent message.

Presentation notes



Computers in a home or an office often use a router and cable modem to connect to the Internet through an ISP. Data from the Internet comes through the ISP’s network to the user’s cable modem.

Once it arrives at the cable modem, the router takes over, directing the information to its intended recipient on the network. The router can tell which machine to send data to based on the IP information in each packet; it matches the data to the IP address assigned to each machine. A cable modem may include the capabilities of a router, simplifying the home network.

Presentation notes



Once a user has requested data from a website, the request and reply are sent across the Internet using many different computers and computer networks. Each stop along the route is called a “hop.” This request, sent from a computer in the San Francisco Bay Area to the BBC News website in London, England, took 16 hops.

As a request or data transmission is sent to a router, the router analyzes the packets and then looks at the available routes to send the data. The router then sends each packet on to the next most-efficient location. Sometimes a packet may spend most of its time traveling through a single data network (as the example here shows, where the packet spent most of its time in the network owned and operated by the firm Level 3). Other times, a packet might change networks or travel along a large backbone connectivity line before reaching its destination.

Depending on the path each packet takes, packets will likely arrive out of order. The destination computer reassembles the packets into the correct order and can send a request for re-transmission if a packet is missing or corrupted.

Presentation notes



If you are worried that your connection to another computer is not working well, you can “ping” that other computer. When you ping a machine, test packets are sent over the Internet to the other machine and then evaluated to see if they were delivered and how long they took to arrive. This example shows a successful ping test—no packets were lost during the test transmission and response.

Sometimes a ping request doesn’t work even if the connection to the other site is working, because many ISPs block Internet Control Message Protocol (ICMP), which is the protocol needed for ping requests. If ICMP is blocked, the ping will fail, even if the other site is working.

Presentation notes



A firewall can protect your computer from Internet threats. It is usually a software program that filters the messages that reach your computer over an Internet connection. If an incoming message is flagged by the filter, the firewall does not allow that message to pass. Firewalls also filter outgoing messages.

The operating system on your PC probably includes a software-based firewall. You can even download a free firewall program from the Internet. Although you can customize the firewall on your own PC, most people rely on the firewall in their operating system, which uses default rules and restrictions.

You can also connect a hardware-based firewall device to your computer using an Ethernet cable. Many routers that send and receive data between networks use a hardware firewall. Hardware firewalls are sometimes more secure, although software-based firewalls are convenient and inexpensive. Most of the time, hardware and software firewalls can coexist, although this may not significantly improve your protection from outside threats.

Presentation notes



A firewall works by having rules that define types of acceptable and unacceptable messages. The firewall compares messages against the rules. A rule will have some matching criteria, and if the message matches, the rule is “fired” (executed). The criteria of the rule might be specific to a website (reject all messages from Facebook.com), specific to a port (accept all messages from port 22), or based on other features such as the size of the message, the time that the message was sent, or the protocol used to send the message (reject any message sent by ICMP but accept any message sent by HTTP).

Schools, large companies, and other organizations configure their firewalls to comply with a set of rules. These rules determine what information can pass to and from the computers based on certain words, websites, or IP addresses.

Presentation notes



As we’ve seen, the Internet is a vast, complicated system of data transfer rules. Because the packets we send follow these rules, the Internet is also a highly reliable way to send and receive information, whether that information is traveling across town or across the world.

Internet travel time is measured in seconds or less. It is common for a user to see the result of clicking a hyperlink in a second or less. The time it takes to transfer content is more likely to be affected by the amount of traffic a server is dealing with than by physical distance.

Presentation notes




Multi-Pass Instructions: How Data Travels the Internet These instructions apply if you choose to print out the corresponding student resource reading pages and post them around the room. It’s important to print the student reading pages rather than the PowerPoint slides, because the reading pages include notes that have further important information for students to consider about each key concept. Instruct the students to take several passes around the room, each time noting the information described below.

First Pass: Survey (5 minutes)● Read the title and introduction, and note the sections of the presentation.

● Examine the illustrations: Have you seen any screenshots like these before?

● Read the headings to see how the presentation is organized.

● Paraphrase the information acquired. What information has been the most surprising to you?

Second Pass: Size Up (15 minutes)● Identify key concepts by using titles and headings, visuals, bold print, and italics. Have you

encountered any of the hardware or other equipment mentioned before?

● Generate questions about key concepts related to the Internet’s connectivity and answer them by looking at the slides.

● Paraphrase key concepts. How is the Internet organized? How does each machine send and receive data over the Internet?

Third Pass: Sort Out (5 minutes)● Answer student-generated questions, and reinforce key concepts.




Bingo Game: Terms and DefinitionsDirections: Call out the definitions only, in random order, giving students time between each definition to look at their bingo card and put a placeholder on the term they think you have defined. Fill in your own bingo card as you go so that you can check for accuracy when a student shouts “bingo!”

1. Internet: The world’s largest computer network.

2. packets: All data travels the Internet in frames that contain these.

3. client: A computer that connects to a server computer.

4. ISP: A company that manages and sells consumer access to the Internet.

5. LAN: A type of network where computers are close together, typically in the same building or office.

6. hop: A stop along the route that data travels across the Internet.

7. WAN: A type of network where computers are far apart—in different buildings, cities, or countries.

8. firewall: A piece of hardware or software on a network designed to limit access to certain machines or users.

9. HTTP: A networking protocol that allows web browsers to talk to web servers.

10. router: A device that links two computer networks or that links a LAN to the Internet.

11. ARPANET: The first wide area network (WAN), which sent its first message in 1969.

12. FTP: A protocol that allows files to be transferred through a network.

13. IP address: A unique set of numbers assigned to a specific computer that is connected to the Internet.

14. HTTPS: A networking protocol that allows web browsers to talk to web servers, using only encrypted messages.

15. URL: The address for a resource, typically a web page.

16. ipconfig: You use this command to show a computer’s IP address in Windows.

17. TCP/IP: The standard Internet protocol used since 1983 that networks use to exchange data.

18. cable modem: This is often used, along with a router, to connect home and office computers to the Internet; it uses the same coaxial lines that go to your television.

19. Domain Name Service (DNS): This is like a phonebook for the Internet: it looks up a host name and returns an IP address, or vice versa.

20. domain name: A name that identifies a computer network on the Internet.



21. DSL modem: This is often used, along with a router, to connect home and office computers to the Internet. It uses phone line connections to connect to the Internet, but since data travels at a higher frequency, the line can simultaneously be used for phone calls.

22. server: A computer that provides information or services to other computers.

23. IPv6: The most recent style of Internet address that uses 128 bits.

24. frames: Web pages and files travel as a series of packets in these.




Quiz: How the Internet WorksStudent Name: _______________________________________________________ Date: ___________

Directions: Respond to the questions and statements below.

1. What is the Internet? What is it made up of?

2.

3. How does data travel the Internet? How does it know where to go?

4.

5.

6.

7. Draw a simple LAN diagram showing IP addresses and how each computer connects to the Internet.

8. What is an ISP? How does it work?




Answer Key: How the Internet Works QuizWhile student answers will vary, the following answer key contains the basic knowledge and concepts to be stated in their responses. Use your preferred scoring or point system to assess the quizzes.

1. What is the Internet? What is it made up of?

2. The Internet is the world’s largest computer network. At its most basic level, it is a WAN made up of many, many smaller WANs and LANs. The Internet links together billions of computers and networks around the world.

3. How does data travel the Internet? How does it know where to go?

4. Each device on the Internet has an IP address, which is similar to the street address for a house. The IP address tells data where it should be delivered and also tracks where data has been sent from. Data travels the Internet in frames that contain packets. Web pages and files travel as a series of packets encapsulated in a frame. Data is divided into packets, packets travel along different networks toward their destination, and then packets are reassembled at their destination. Routers are the devices that receive the frame and process each packet’s IP address.

5. Draw a simple LAN diagram showing IP addresses and how each computer connects to the Internet.

Student drawings should resemble the diagram below.

6. What is an ISP? How does it work?

An ISP is an Internet service provider. It is a company that provides individuals and companies with a connection to the Internet. An ISP’s services usually include providing users with email addresses and providing access to online storage space, and they sometimes offer web hosting services. DSL and cable Internet are the most common types of consumer Internet connections provided by ISPs. How it works depends upon the type of modem you connect your computer to. DSL modems use phone lines to connect to the Internet. But since the lines carry digital data at a higher frequency, they do not tie up the phone line. For this reason, DSL can be “always on.” Cable modems work like DSL but use the same coaxial lines that go to your television.




Key Vocabulary: How the Internet WorksTerm Definition

backbone Large fiber-optic cables (or bundles of them) that move much of the data packets on the Internet from one place to another.

broadband An Internet connection that is made using a modem but is always on (dialing in to establish a connection is not needed).

client A computer that connects to a server computer.

digital subscriber line (DSL) A type of Internet connection that uses phone lines but transmits signals digitally across an always-open connection.

domain name A name that identifies a computer network on the Internet.

File Transfer Protocol (FTP) One particular protocol that allows files to be transferred through a network.

Hypertext Transfer Protocol (HTTP)

The networking protocol used by the World Wide Web. It defines how messages are formatted and transmitted, and the actions web servers must take in response to requests received from clients.

Hypertext Transfer Protocol Secure (HTTPS)

A variation of HTTP in which messages are encrypted before they are transmitted. This assures a user that any information entered into a web form, such as a credit card number, cannot be intercepted or understood by a third party. HTTPS is needed because HTTP is not secure.

integrated services digital network (ISDN)

An older type of Internet connection that uses standard circuit-switched phone lines to send digital data.

Internet Protocol (IP) address A unique set of numbers assigned to a specific computer that is connected to the Internet. This is similar to a house’s street address.

Internet service provider (ISP) A company that sells and manages consumer access to the Internet.

IPv4 An older form of addressing that limited the number of unique IP addresses available.

IPv6 A newer form of addressing that has a nearly unlimited number of unique IP addresses. IPv6 also provides a form of encryption technology not available in IPv4.

router Networking hardware responsible for keeping data going from hub to hub across a network.

server A computer that provides information or services to other



computers.

Transmission Control Protocol/Internet Protocol (TCP/IP)

The set of networking rules that control how data is sent from one specific machine (as defined by its IP address) to another.




Bibliography: How the Internet WorksThe following sources were used in the preparation of this lesson and may be useful for your reference or as classroom resources. We check and update the URLs annually to ensure that they continue to be useful.

PrintGralla, Preston. How the Internet Works, 8th ed. Indianapolis, IN: Que Publishing, 2007.

OnlineCerf, Vinton G. “How the Internet Really Works.” NetLingo, http://www.netlingo.com/more/cerfart.cfm (accessed May 24, 2016).

“History of the Internet.” Internet Society, http://www.isoc.org/internet/history/ (accessed May 24, 2016).

Internet World Stats Usage and Population Statistics, http://www.internetworldstats.com/stats.htm (accessed May 24, 2016).

Nuasoft Internet Surveys, http://www.nua.ie/surveys/ (accessed May 24, 2016).

Ookla Speedtest, http://www.speedtest.net/ (accessed May 24, 2016).

“Packet Switching.” Wikipedia, https://upload.wikimedia.org/wikipedia/commons/f/f6/Packet_Switching.gif (accessed May 24, 2016).

Speakeasy, http://www.speakeasy.net/ (accessed May 24, 2016).

“Three Technology Revolutions.” Pew Internet & American Life Project, http://www.pewinternet.org/three-technology-revolutions/ (accessed May 24, 2016).

Zakon, Robert H. “Hobbes’ Internet Timeline.” Zakon.org, http://www.zakon.org/robert/internet/timeline/ (accessed May 24, 2016).

Abby Ryan Design. “PC Ninja”. http://www.abbyryandesign.com/pc-ninja/ (accessed January 30, 2018).


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