AQA GCSE Computer Science 3.5 Fundamentals of computer networks: LANs and WANs, topologies, wired and wireless, protocols, layers and security

What area 3.5 actually demands

Fundamentals of computer networks explains how computers are joined together and communicate. It is a definition-heavy area in Paper 2, where the marks reward precise terms and clear comparisons. You need to know the types and shapes of networks, how devices connect by cable or wirelessly, the rules (protocols) and the layered model that make communication work, and how a network is kept secure.

This guide ties together the four dot-point pages for the area.

Networks and topologies

A network is two or more devices connected to share data and resources. A LAN is local and usually owned by one organisation; a WAN spans a large area using third-party infrastructure, the internet being the largest WAN. The two topologies are the star (every device connected to a central switch, so one cable failure affects only that device) and the bus (all devices on a single shared backbone, cheap but congestion-prone and reliant on the backbone).

Wired and wireless

Devices connect by wired links (cables, generally faster, more reliable and more secure) or wireless links such as Wi-Fi (radio waves, allowing free movement but generally slower and easier to intercept). Because wireless signals can be intercepted, wireless networks use encryption to scramble the data.

Protocols and layers

Communication relies on protocols, agreed rules such as TCP/IP (packets, addressing and routing), HTTP and HTTPS (web pages, HTTPS encrypted), FTP (files) and the email protocols SMTP, IMAP and POP. These are organised into the four-layer TCP/IP model (application, transport, internet/network, link/data link), and layering breaks the complex task into independent parts that can be developed and changed separately.

Network security

Finally, a network is kept safe by combining authentication (proving who a user is), encryption (scrambling data), firewalls (controlling traffic in and out) and MAC address filtering (allowing only approved devices). No single method is sufficient alone.

Check your knowledge

A mix of recall and comparison questions covering area 3.5. Attempt them, then check against the solutions.

1. State what a network is. (1 mark)
2. State one difference between a LAN and a WAN. (2 marks)
3. Give one advantage of a star topology. (1 mark)
4. Give one advantage and one disadvantage of wireless compared with wired. (2 marks)
5. State why wireless networks use encryption. (1 mark)
6. Name the four layers of the TCP/IP model. (2 marks)
7. State what the HTTPS protocol is used for. (1 mark)
8. Name two methods used to keep a network secure. (2 marks)