The Five Components
Every time data goes from one device to another, the same five things are at work. Learn their names, and then take them away one at a time — the quickest way to see what each one is for.
1The five components
The device that sends the data.
Examples: A computer, a phone, a smartwatch, a video camera.
The device the data is sent to.
Examples: A computer, a phone, a printer, a smart TV.
The data or information being sent.
Examples: Text, numbers, images, audio, video — or a mix of them.
The path the message travels along from sender to receiver.
Examples: Wired: a network cable. Wireless: radio waves through the air.
The set of rules that sender and receiver both follow.
Examples: HTTP for web pages, SMTP for sending email.
A device is not always a sender or always a receiver. When you reply to a message, your phone becomes the sender and your friend’s phone the receiver.
Communication media gets a whole chapter of its own, Transmission Media. Protocols get one too, Network Protocols, where you will meet HTTP, SMTP and the rest.
2Take one away
Each component is needed for a different reason. Remove one, press Send, and watch where the message fails. Try all five.
Remove a component, press Send, and see why the message needs it. Drag sideways to turn.
Four of them stop the message from arriving at all. The protocol is different: without it the data does arrive, but the receiver cannot make sense of it. That is the easiest one to forget, and the one exams ask about most.
3Why protocols are needed
Think of a letter in the post
Computers are made by many companies and run different software. A protocol is what lets them work together. It decides things like:
- how the data is arranged, so the receiver knows where each part is,
- how the sender and receiver are addressed,
- how fast the data is sent,
- how to check that the data arrived without mistakes,
- what to do if something goes wrong.
Read the situation and pick the component it describes.
4From the board papers
▶Show the answer
Protocol. “Set of rules” is the phrase to spot.
▶Show the answer
Protocols are needed so that devices can communicate successfully and reliably. They set the rules both sides follow — how the data is arranged and addressed, how it is sent, and how errors are checked — so that devices from different makers, running different software, can understand each other.
5Check yourself
Which of these is NOT one of the five components of data communication?
Two computers are joined by a working cable, but they follow different protocols. What happens when one sends a message?