Unit introduction

Parts of this lesson have been adapted from code-it.org.uk by Phil Bagge on a Creative Commons licence. The original planning can be found on Phil's excellent site here.

This unit aims to help students understand how the Internet is works, how data travels around it and how it is built with code. The first three lessons look at the journeys that data takes as it moves around the internet and the following lessons look at web coding with HTML and CSS, how that can be remixed  and how students can begin to build their own web content by using and remixing code.

 

Key terms and information (read before lesson)

Be sure to check out the key vocabulary on the unit home page before you start this lesson! You can find it here.

Some key things to know about are also listed below:

Server - The heart of any school network is the server or servers. These are computers made from the best components. Typically schools spend 10 times as much money on a server than any other computer. Find out where your servers are stored. Servers are rarely turned off.

Server Jobs - Manage a list of people who are allowed on the network (logon), hold all school saved work, manage printers. 

Switch - A box that switches data from one computer to another. Schools can have lots of switches but this model is best served by one. All wired computers connect back to the switch. 

Wireless Access Point (WAP) - A box that takes data from a wired network and converts it into wireless signals. Schools can have lots of WAPs but our model is best served by one. 

Router - A box that connects the a household, business or the school’s network to the internet. There are millions of routers across the world that route data from one location to another via the internet. 

Firewall - Software that tries to reduce the amount of viruses, malicious software and hackers that can come into the school network from the Internet.

Proxy server - A proxy server improves Internet access speeds from a network primarily by using a caching system. Caching saves recently viewed Web sites, images, and files on a local hard drive so that they don't have to be downloaded from the Web again. The other main purpose a proxy server is to filter what is allowed into the network. The proxy server can limit what Web sites users on the network can access.

Wired Network - These are wires that go from the switch to every wired computer. These are typically much faster than wireless connections and are usually ethernet cables. On our diagram these will be solid lines.

Wireless Network - Signals that pass through the air from the wireless access point to laptops or tablets.

Laptops - Most laptops are wireless computers managed by the server.

Computers or PCs - Personal computers that are managed by the server, typically these are wired into the network. Every school is different but if you have a suite or banks of computers they are most likely to be wired.

iPads or Android Tablets - Typically most of these devices are not managed by the server but do use the network to access the internet and sometimes share media such as photos and videos Every network is different but this basic model is similar to most primary school networks.

 

Introduction

The lesson begins in the classroom but later parts of lesson need a big space, such as the playground or your hall. 

Begin by asking the class - What is the internet?

Ask them to come up with a clear definition in small groups and then ask groups to share with the class.

It can be described as a network of networks, but then what is a network? At this point, introduce the lesson objectives.

Define a network as a group of connected devices that can communicate and share data and resources.

 

Our teacher presentation shows an example of what a typical school network might look like. device types and numbers will vary, but this shows a common kind of setup.

 

Later in the lesson we will act out how the network functions, but to begin with, let's take a look at some of the key parts.

 

Server

Start with the server. Mention that it is the most important computer in the school and that it is typically 10 times more expensive than other school computers. Explain that it has a list of everyone who is allowed to login to the school network (usernames and passwords). it also stores all files that are saved locally on the network. 

The teacher presentation show how increasingly larger sizes of servers are required as organisations and data requirements grow, right up to companies like Google, who have enormous warehouse sized server rooms to store all the data needed for their tools such as Gmail, Google Drive, Google Maps, YouTube and much more.

This video in the presentation gives an idea of what their data centres are like.

 

 

 

The switch box

A switch box is basically a junction box of plug sockets that allow all the wires from the network devices around school to come together and connect to the server. It's a bit like a plug extension lead where four plus can connect to one plug socket in the wall.

The more wired devices you have, the more switch boxes you need.

Wired devices

All the wired devices in school are physically connected to the server, via the switch box using ethernet cables. These carry data from the computers, through the cables in the walls and ceilings, to wherever your switch and server are located in school. 

 

 

 

Wireless devices

Other devices inside your school are wireless. These could be tablets, laptops, interactive boards and other things too. They send and receive data through the air with radio waves.

 

Wireless access points send and receive wireless signals and connect these devices back to the wired network. 

 

 

Connecting to the internet

Your device in school does not connect directly to the internet. There are several steps between your device and the internet to help keep you safe and protected.  

 

A router routes (directs) data from one location to another via the internet. There are millions of routers around the world which direct the traffic of data on the internet. You will probably have a router in your home with a built in modem and wireless access point. 

 

Firewalls

 A firewall is software (a computer program) that tries to reduce the amount of viruses, malicious software and hackers that can come into the school network from the Internet. It acts like a wall to try and keep the bad stuff out.

 

Proxy server

A proxy server improves Internet access speeds by using a caching system. Caching saves recently viewed Web sites, images, and files so that they don't have to be downloaded again. It also adds another layer of protection by providing filters for which websites users on the network can access. 

 

How a network functions roleplay

To help us understand how a network functions and performs the jobs we use every day, we’re going to act it out. 

We will look at:

• What each part’s job is.
• What happens when you log in on a computer on your network.
• What happens when we open a file that is saved on the server.
• What happens when we access the internet and the job of the firewall.

Head outside or to somewhere in school with plenty of space, such as the hall. You can use our 'Build your own network role play cards' to help you with this activity. The diagram on the first slide is to show you roughly how the whole thing can be laid out, and where you will need children to play the various roles.

If you are outside, you can draw in the wires and wireless connections with chalk on the floor, otherwise use balls of string or wool. Try and have two different colours to represent wired and wireless connections.

1. The Server

Start with the server. Remind the class that it stores saved files and controls when someone logs on to a computer. Choose a child to model the server and sit them behind the card of a server.

Now draw a line (or use string/wool) from the server to switch box. Explain that the switch carries signals from the server to every other computer on your network and back again. 

 

2. Logging on

Continue your line (string/wool) from your switch box to link up the wired computers (PCs). Sit two children behind each PC. Ask one child from each pair to act out a login request. They should walk along the wire, past the switch to the server and ask "Can I log in please?"

At this point the server requires a username and password for each user trying to log on. "Let me see if  you are on the server list"  "Do you have an account I recognise?"

Ask the server child to act out accepting their username and password and then provide them with one of the 'I'm logged in' cards. Each child should take this back to their PC.

Ask the class - What will happen if we spell our username incorrectly or get our password wrong? If this happens the server won’t find the user on its list and won’t let them login.

What happens when everyone tries to login at the same time? It creates a queue! The more jobs the server has to do at the same time, the slower the network will function.

 

3. Opening Files

What happens when we save or open up work from the network?

The other child from each PC should return to the server and request the piece of work they have previously saved. The server should provide one of the 'Saved piece of work' cards and the PC child should take it back to their PC.

If they work on it during a lesson and then save it again, the file should be taken back to the server. Model this with one PC (and pupil helpers).

 

4. Wireless devices

Now wire up the switch to the wireless access point (with chalk/string/wool). Explain that this converts the signal from data in a wire to data that can be carried through the air. Draw a dashed line (or a different colour of string/wool) to one of the wireless laptops. 

 

5. Connecting to the Internet

Explain that not every device on the network is controlled by the server. Most tablets and Chromebooks don’t logon to the server and many don’t save work on the server either. Instead, they save files to the cloud (internet servers) or locally on the device itself. 

But these mobile devices do connect to the Internet through the school network. Connect up any mobile devices you have on your network (with dotted lines or the same coloured string/wool you used for wireless connections earlier) to the wireless access point. Here, their connection to the network becomes wired again. 

Connect the wireless access point to the switch and the switch to the router with solid lines.

 

6. The router and websites

Explain that the router carries signals beyond the school all over the world to fetch web pages, emails, videos and other internet services.

Now join the router to the firewall. Appoint a child to be the firewall and explain that their job is to check data to see if it has viruses before letting it in or out of the school.

Add another wire from the router to the proxy server and another from the proxy server to the The Internet. 

Go back to the children at the mobile devices. Explain that we are going to act out what happens when they try and open a website on their device.

One child from one pair will represent this journey. They should walk to the wireless access point with it's request to access a website. The wireless access point should send them to the switch, the switch should send them to the router, the router should send them to the firewall and proxy server which should both let them pass. From here they reach The Internet, which should hand them all four 'View a website' cards.

The child should then begin their journey back, but stop at the proxy server to drop off three of the 'View a website' cards. Stop again at the firewall which must decide it the data coming into the network is safe. Continue through the router, switch and wireless access point, back to their device. Point out that this takes less than a second typically! 

Now a child from each of the other three mobile devices can repeat this process, but they only need to go as far as the proxy server as it has cached the website they want to access (the three website cards we dropped off their), which saves the website data more locally and prevents the final journey to the web server of the Internet. Collect the website cards and return to their devices through the network.

 

7. Security

Back to the PCs. Choose two children to represent trying to download a file from a website. Each child should make the journey through the network to the switch, to the router, through the firewall and proxy server to the Internet. Here they should collect the two file cards (safe and infected). On the journey back illustrate how the firewall should allow the safe file through but block the infected file.

 

Network Printing

Finally, model the safe document (that was just downloaded) being sent to the server and then to the printer where it is printed. A print server manages the printing queues.

Get some photos and then tidy up and head back to the classroom. 

Creating their own Map

Back in the classroom, give each child a copy of My school network - Pupil worksheet. 

Explain that they are going to draw the network and explain how some of it works. On the front of the sheet, they can draw out a version of the network diagram modelled outside, or one closer to your actual school network. Key components and icons are shown to help them.

On the back of the sheet they should answer the two questions to show their understanding. Key words for them to use are provided.

An example network map is shown in the presentation.

 

Plenary

Review the purposes of some of the key equipment in a network that they should have added to their diagram, asking students to explain what each part does.