Where does a click go?
You click a link on your laptop at school. A page appears from a computer in another country. Your click did not fly. It went through your cable, a box in the cupboard, a bigger box, a line in the street and many more boxes.
Today you name each box and say what it does.
Key words
| Word | What it means | Example |
|---|---|---|
| Switch | a device that joins devices on one network and sends data only to the right one | |
| Router | a device that joins networks and sends data between them | |
| ISP | internet service provider: the company that gives you internet | a broadband company |
| Backbone | the main high-speed links that carry internet traffic between big networks | |
| Client | a computer that asks for a service | |
| Server | a computer that gives a service | |
| Network | devices joined so they can share things | |
| Packet | a small piece of data sent over a network | |
| IP address | a number that names a device on a network | |
| MAC address | a number built into a network card that names it |
The cells students fill in are left blank in this preview.
By the end of this lesson
Note
I can say what a server, client, switch, router and the internet backbone each do.
Starter
Have a go
Starter
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Servers give, clients ask
A server gives a service: web pages, files, email or logins. It is on all the time. A client is the computer that asks. Your laptop is a client when you open a web page.
One computer can be both. It is the job, not the box, that decides.
A switch joins, a router connects
A switch joins the devices in one network. It learns each device's MAC address and sends data only to the port where that device is. This keeps traffic tidy and fast.
A router joins different networks. It reads the IP address on each packet and chooses where to send it next. Your home router joins your network to the internet.
Switch compared with router
| Question | Switch | Router |
|---|---|---|
| What does it join? | Devices in the same network | Different networks |
| What address does it use? | MAC address | IP address |
| Where is it? | In the room or the cupboard | At the edge of the network |
| Example job | Sends a file from a PC to the printer | Sends a web request out to the internet |
The cells students fill in are left blank in this preview.
Extra: Where does a computer send outside traffic?
sudo ip netns exec h1 ip routeA command for the lesson’s lab terminal. It is shown here and not run.
Extra: Which devices has it talked to?
sudo ip netns exec h1 ip neighA command for the lesson’s lab terminal. It is shown here and not run.