6.2. Computer Networking

Time Estimate: 45 minutes

6.2.1. Introduction and Goals

Computer systems and networks is one of the five Big Ideas of the CS Principles (CSP) curriculum and rightly so: The Internet has had a tremendous impact on our lives and on modern society. Yet, despite its impact and influence, most people do not really understand what the Internet is and how it works.

We introduced the Internet in Unit 2, where we covered the following points.
  • The Internet is the global public network of independent and autonomous networks that are governed by the Internet Protocol Suite.
  • The Internet is not the same as the World Wide Web (WWW). The WWW is an application that runs on the Internet using HTTP.
  • The Internet is based on open (non-proprietary) standards, which has enabled it to grow exponentially since its inception in the early 1980s.
  • The cloud is an everyday term for the Internet and/or WWW.

This lesson provides a high-level overview of some of the Internet's and WWW's key concepts and terminology. A follow-up lesson will go into greater detail in explaining how the Internet works.

Learning Objectives: I will learn to
  • explain the fundamentals of how the Internet works
  • describe the client/server model of networking
  • explain how bandwidth and latency independently affect an internet connection
  • describe issues that contribute to the digital divide
Language Objectives: I will be able to
  • use target vocabulary, such as protocol, bandwidth, latency, and digital divide while describing computer networks and their effects on society, with the support of concept definitions and vocabulary notes from this lesson

6.2.2. Learning Activities

Part 1. Basic Concepts and Terminology

In Unit 2 we defined the Internet as a network of disparate networks that is governed by systems of rules, known as protocols. In this first presentation we'll see some examples of different types of networks and we'll learn about the role that special devices known as routers play in enabling communication between different types of networks.

(Teacher Tube version)

Activity 1 

Answer the following questions in pairs, groups, or as class discussion:
  • Which country has the fastest download speeds on the Internet? Is the U.S. in the top 3? Try to guess the answers to these before looking them up on Speed Test Global Stats.
  • What is the percentage of Internet user penetration for the United States? The Internet user penetration is the percentage of the population that has access to and uses the Internet. Access to the Internet depends on the ability to connect a computing device to an Internet-connected device like a router. Do you think we are close to 100%? Try to guess before you look online. You may get different data depending on the date of the data. Some sources are https://en.wikipedia.org/wiki/List_of_countries_by_number_of_Internet_users, https://www.internetworldstats.com/stats.htm, and Internet Live Stats site which presents Internet penetration data by country.
  • Do all countries have similar Internet user penetration or is there a digital divide (a gap between those who have Internet access and those who don't)? How big is the digital divide between continents or countries? Find data online using the sources above or others to answer this question.
  • What can we do to reduce the effects of the digital divide both locally and globallly? Discuss in your class.

The digital divide refers to a gap or differing access to computing devices and the Internet based on socioeconomic, geographic, or demographic characteristics. It can affect both groups and individuals and can be affected by individuals, organizations and government actions. The digital divide raises issues of equity, access, and influence, both globally and locally. The digital divide is huge when we compare first and third world countries. But even students in the U.S. experience the digital divide in different schools. If you're interested in this topic, watch the National Geographic's Without a Net: Digital Divide documentary.

Part 2. Client/Server Model

When you are using the Internet to read email or visit a web site, your device (phone or tablet or computer) is playing the role of a client. It is using client software, such as a web browser or email application to communicate with a server, which is computer on the Internet that provides a specific service, such as email or web browsing. Clients and servers form a computing system which is a group of computing devices and programs working together for a common purpose. The TCP and IP protocols route messages between the clients and servers finding a path from the sender to the receiver. In this next presentation we'll look at how communication occurs between a client and server using HTTP.

(Teacher Tube version)

Activity 2: Client/Server Model

Complete the activity in this worksheet to review the client/server model.

Part 3. Internet Performance

In this next presentation we learn about two important measures of Internet performance. The first, bandwidth, refers to the amount of data that can be sent in a fixed amount of time and is usually measured in kilobits or megabits per second. The second, latency, refers to how long it takes a packet of data to go from its source (e.g., a client) to its destination (e.g., a server). You'll be introduced to some easy-to-use tools that will enable you to measure bandwidth and latency from your home or school networks.

(Teacher Tube version)

Activity 3: Measuring Bandwidth and Latency

Use the http://www.bandwidthplace.com/ tool (or  http://speedtest.xfinity.com/) to measure the bandwidth and latency of your Internet connection.
  1. What are the download and upload speeds for your Internet connection? Note that these bandwidth are measured in megabits per second (Mbps). Why do you think Internet Service Providers (ISPs) provide different bandwidths for downloading and uploading from the Internet?
  2. Measure the bandwidth at school and at home. Are they different? How do they compare to the fastest download speeds you found in Activity 1 on the Speed Test Global Stats site?
  3. This speed test also provides a latency test using a utility called ping which returns the amount of time (usually measured in milliseconds) to send a small packet of data from one computer (the bandwidthplace server) to another (your computer). What is the latency for your connection? Why is this a useful measurement?

6.2.3. Summary

In this lesson, you learned how to:

6.2.4. Still Curious

  • This video contains a very visual example of bandwidth using balloons and pipes that you could even recreate in your classroom.
  • This video compares bandwidth to vehicles such as buses and race cars. It also explains latency concepts in terms of the speed of light and queues (lines).

6.2.5. Self-Check

Here is a table of some of the technical terms we've introduced in this lesson. Hover over the terms to review the definitions.

network
World Wide Web
client
server
computing system
protocol
SMTP/POP
URI 		digital divide
ethernet
host
bandwidth
latency
modem
LAN
WAN 		HTTP
HTML
router
routing
Internet Service Provider (ISP)
wifi

6.2.6. Reflection: For Your Portfolio

Answer the following portfolio reflection questions as directed by your instructor. Questions are also available in this Google Doc where you may use File/Make a Copy to make your own editable copy.

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