Networks & Topologies (Years 8–11) — Computer Science

How computers are connected: LANs and WANs, star and mesh topologies, and the client-server versus peer-to-peer models.

The moment two computers are joined so they can share data, you have a network. From two laptops swapping a file over a cable to the billions of devices on the internet, the idea is the same: connect machines so they can talk. Understanding how they are wired together — the shape, or topology — explains why some networks are fast and reliable while others crawl or collapse.

Why this matters: Every school, shop and hospital runs on a network. The choices an engineer makes about topology and about who holds the data decide the cost, the speed and what happens when one machine fails. These are the first decisions in building any computer system.

A star topology — every node has its own cable to a central switch.

LAN and WAN: near and far

A WAN joins separate LANs across distance, usually over rented lines.

A LAN (Local Area Network) covers a single site — one building or campus — and the owner supplies its own cabling and hardware. Your school network is a LAN. A WAN (Wide Area Network) joins LANs across large distances, using infrastructure the owner usually rents from telecoms companies. The internet is the biggest WAN of all. Think of a LAN as the corridors inside one building, and a WAN as the motorways linking cities.

Feature	LAN	WAN
Area covered	One site	Countries / global
Cabling owned by	The organisation	Rented (telecoms)
Typical speed	Very high	Lower, more variable
Example	School network	The internet

Topologies: star vs mesh

In a mesh, many links mean data reroutes when one path (dashed) fails.

In a star topology, every device has its own cable to a central switch. It is fast and reliable — if one cable fails, only that one device drops off — but the switch is a single point of failure and the cabling costs more. In a mesh topology, devices connect to many others, so data has several possible routes. If one link breaks, traffic simply reroutes. Mesh is extremely resilient (it is how the internet survives) but expensive to wire fully. A star is like spokes on a wheel; a mesh is like a road map where you can always find a detour.

Client-server vs peer-to-peer

Clients depend on one server; peers are all equal and share directly.

Networks also differ in who holds the data. In a client-server model, powerful central servers store files and control access, and ordinary clients request what they need. It is easy to back up and secure centrally, but the server is costly and, if it fails, everyone stops. In peer-to-peer (P2P), every computer is equal, sharing files directly with no central server — cheap and simple for small groups, but hard to back up and secure.

Scenario: A 600-pupil school needs pupils to log in anywhere, with files backed up nightly and websites blocked centrally. Choose client-server: a central server enforces logins and filtering and holds every file in one place to back up. A two-person startup swapping design files would instead pick peer-to-peer — no server to buy or maintain.

Common mistake: Confusing topology (the physical shape — star, mesh) with the model (who holds data — client-server, P2P). A star-shaped network can be either client-server or peer-to-peer; they answer different questions.

Tip: When a question asks you to justify a choice, always tie it to consequence — cost, speed, security, or what happens when one part fails. That reasoning earns the marks, not just naming the type.