OCR GCSE Computer Science 1.3 Computer networks, connections and protocols: LANs and WANs, topologies, hardware, wired and wireless, protocols and layers

What topic 1.3 actually demands

Computer networks explains how devices are connected and communicate. It is a definition- and comparison-heavy topic examined in Paper 1, where the marks reward precise roles and clear contrasts. You need to know the types and scales of network, what affects performance, the two management models, the two topologies, the hardware, wired versus wireless, and the protocols and layered model.

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

Networks, scale and management

A LAN covers a small area (one site); a WAN covers a large area (the internet is a WAN). Performance depends on bandwidth (shared between users), the transmission media (fibre over copper over wireless) and interference. A client-server network has central servers serving clients (control and security for organisations); a peer-to-peer network has equal computers sharing directly (cheap and simple for small setups).

Topologies and hardware

In a star topology every device connects to a central switch; it is reliable except that the switch is a single point of failure. In a mesh topology devices link to many others, giving multiple paths and no single point of failure but high cost. The key hardware: a NIC joins a device to a network, a switch directs data on a LAN by MAC address, a router connects networks and routes by IP address, and a wireless access point lets wireless devices join a wired network.

Wired, wireless and protocols

Wired (Ethernet) is faster, more reliable and more secure; wireless (Wi-Fi) is convenient and mobile but slower and easier to intercept, so encryption scrambles the radio data with a key. Protocols are agreed rules: TCP/IP packetises, addresses and routes data; HTTP/HTTPS fetch web pages (HTTPS encrypted); FTP transfers files; SMTP sends email; POP and IMAP retrieve it. A layer is a self-contained level handling one task, and layering makes networks manageable, independently updatable and interoperable.

Check your knowledge

A mix of recall and comparison questions covering topic 1.3. Attempt them, then check against the solutions.

1. State one difference between a LAN and a WAN. (1 mark)
2. State two factors that affect network performance. (2 marks)
3. State one advantage and one disadvantage of a star topology. (2 marks)
4. State the role of a switch. (1 mark)
5. Give two advantages of a wired connection over a wireless connection. (2 marks)
6. Explain why encryption is used on a wireless network. (2 marks)
7. State which protocol sends email and which two retrieve it. (2 marks)
8. Give one benefit of organising a network into layers. (1 mark)