That Blue Square Thing

AQA Computer Science GCSE

This page is up to date for the AQA 8525 syllabus for exams from 2022.

Networks – Network Protocols and TCP/IP

Data is sent across networks all the time.

When you opened this webpage your web browser sent a request (data) for the contents of the page to the server it's stored on (somewhere near Slough I believe). The server sent the data back as an HTML file, which your browser organised in to something that hopefully looks sort of like it should do.

The same sort of thing happens when you send an e-mail or an SMS. Or when you open a file stored on a school network or a cloud server. Or when you stream a film. Or play music using a bluetooth speaker. All of these involve data moving across networks.

PDF iconHow data is transferred across networks – the basic ideas which underpin everything else here

Network Protocols

All of this data communication is governed by network protocols.

Network protocols are sets of rules that are used to allow devices to communicate with each other effectively. Without protocols it would be impossible for one device to undersand the data sent from another.

Protocols are particularly important when it comes to sending data over the internet.

PDF iconProtocol Intro – slides I use in class

PDF iconThe 8+2 Protocols – ten in total (a simple list)

PDF iconProtocols – textbook style resource which deals with the protocols you need to know

You're going to want a little bit more detail on some of the protocols, especially when you come to revise.

PDF iconProtocols Summary – for revision
This is the full detail, adapted from a markscheme, of what you might need to know about each protocol.

This is a part of the exam where you might see multiple choice questions.

PDF iconMultiple choice questions

You'd never see eight mutiple choice questions in a row like this, but you might easily see 2 or 3. The exam board rules for answering these questions are show below:

multiple choice question rubric diagram

It would be best if you didn't need to make corrections as it seems quite complex! My tip of multiple choice questions is not to go anywhere near the answer lozenge to beging with. Mark down the left side which answers you know aren't the right answer first, leaving the possibilities. Then go on to the next question and come back to the multiple choice questions later.

At that point you can check again and make sure you have narrowed the possible answers down as much as you can. Then you go for your answer. The important thing is that you come back to them – they're really easy to mis-read the first time and you really don't want to end up having to go through the changing your answer procedure; especially not if you then decide that you were right the first time!

The TCP/IP Model

The TCP/IP model describes how the protocols and families of protocols work together to allow devices to access a network.

You need to know the layers in the TCP/IP stack, what they do and the order they go in as well as which layer each protocol fits in to. If you can see how the model works then that's great, but most questions you get on this will be related to the stack itself.

PDF iconThe basic TCP/IP model – the stack and what's in it

PDF iconThe TCP/IP model – text book notes and activities

PDF iconExplaining the TCP/IP model – how it works

Here's a one slide summary which might help with revision.

PDF iconTCP/IP summary – everything you have to know on one slide

The ways that devices interact with networks is to do with the client-server model. You might want to look at some slides which introduce this. It's not in the syllabus as such, but it's useful background.

PDF iconThe Client-Server model – slides to describe the basics of the model