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A computer network is two or more computing devices connected together so that they can communicate and share resources. Networks are fundamental to modern computing — from the small Bluetooth connection between your phone and headphones to the global infrastructure of the internet.
This lesson covers the three main types of network you need to know for GCSE Computer Science: LAN, WAN and PAN.
A Local Area Network (LAN) covers a small geographical area, typically a single building or a campus of buildings. Examples include:
| Feature | Detail |
|---|---|
| Geographical size | Small — a single building or site |
| Ownership | Owned and maintained by the organisation or individual that uses it |
| Hardware | Typically uses switches, wireless access points and a router |
| Connection media | Ethernet cables (copper or fibre optic) and/or Wi-Fi |
| Speed | Generally high speed (100 Mbps to 10 Gbps on modern networks) |
| Cost | Low ongoing cost once installed, because the organisation owns the infrastructure |
A Wide Area Network (WAN) connects computers and LANs over a large geographical area — a city, a country or even the entire world. The internet is the largest and best-known example of a WAN.
| Feature | Detail |
|---|---|
| Geographical size | Large — cities, countries, continents |
| Ownership | Uses infrastructure owned by third parties, such as telecommunication companies |
| Hardware | Routers, leased lines, satellite links, undersea cables |
| Connection media | Fibre optic cables, telephone lines, satellite, microwave links |
| Speed | Varies — can be slower than a LAN due to distance and congestion |
| Cost | Higher ongoing cost because of leased lines and third-party infrastructure |
| LAN | WAN | |
|---|---|---|
| Area | Small (single building/site) | Large (city/country/global) |
| Ownership | Owned by the organisation | Uses third-party infrastructure |
| Speed | Typically faster | Typically slower |
| Cost | Lower running costs | Higher running costs |
| Security | Easier to secure | Harder to secure due to scale |
A Personal Area Network (PAN) is the smallest type of network and covers the area immediately around an individual person, typically within a few metres.
| Feature | Detail |
|---|---|
| Geographical size | Very small — typically within a few metres |
| Connection | Usually Bluetooth or USB |
| Devices | Personal devices (phone, tablet, headphones, smartwatch) |
| Speed | Relatively low compared to LAN |
Networks can also be classified by how they are organised:
In a client-server network, one or more powerful computers called servers provide services (files, printing, email, web pages) to other computers called clients.
In a peer-to-peer network, all computers are equal — there is no dedicated server. Each device can act as both a client and a server.
| Feature | Client-Server | Peer-to-Peer |
|---|---|---|
| Central server | Yes | No |
| Security | Centralised, easier to manage | Decentralised, harder to manage |
| Backup | Centrally managed | Each user backs up their own files |
| Cost | More expensive (server hardware and software) | Cheaper to set up |
| Best for | Large organisations | Small networks or home use |
Exam Tip: You may be asked to compare LAN and WAN. Make sure you can describe at least three differences, covering area, ownership and speed.
The boundary between a LAN and a WAN is not always obvious in real-world scenarios, and the AQA examiner often deliberately probes that boundary. The defining test is ownership and geography, not raw size. A university campus that spans 800 metres and uses its own fibre between buildings is still a LAN, because the institution owns the infrastructure end-to-end. The moment that data leaves owned infrastructure and traverses a third-party telecommunications carrier — whether a leased line, a cellular link or the public internet — you have crossed into WAN territory.
Worked example — High-street retail chain. A supermarket chain has 920 stores in the UK. Each store has roughly 40 devices: tills, handheld stock scanners, back-office PCs, CCTV recorders and a wireless access point for staff devices. Inside each store, the devices form a LAN built around a star topology with a managed switch and a single edge router. Each store's edge router is connected to the chain's central data centre via a leased line rented from a national telecoms provider. The interconnection of all 920 store LANs through that telecoms infrastructure forms the corporate WAN. The data centre itself runs another LAN behind a hardware firewall. So the same organisation simultaneously operates 921 separate LANs and one WAN that stitches them together.
Consider a 25-device network. A wired LAN using a 24-port managed switch and Cat6 cabling might cost roughly £450 in hardware and £600 in labour, plus a £400/year broadband contract. Over five years that is £450 + £600 + (5 x £400) = £3,050. By contrast, a WAN-style connection between two offices with a 100 Mbps leased line typically costs £350 per month, giving (5 x 12 x £350) = £21,000 for the same period before any equipment costs. The cost gap is precisely why most organisations only deploy a WAN where geography forces them to.
Although both arrangements appear in LANs and WANs, the choice between client-server and peer-to-peer is driven by three factors: scale, security and administrative budget. A client-server network is the right answer whenever (a) more than about 10 users need shared resources, (b) data must be backed up centrally, or (c) user accounts and permissions must be managed centrally. A peer-to-peer arrangement is appropriate where the user count is small, no full-time administrator is available, and the value of the shared data is low.
| Decision factor | Choose client-server | Choose peer-to-peer |
|---|---|---|
| User count | 10 or more | Fewer than 10 |
| Central backup needed | Yes | No |
| Shared accounts/permissions | Required | Not required |
| Dedicated admin | Available | Not available |
| Initial budget | Higher (server hardware, NOS licences) | Lower |
| Sensitive data | Yes — central control needed | No — informal data only |
A small primary school of 200 pupils almost always picks client-server because pupil work must persist on a file server, accounts must be managed by year group, and the school employs (or contracts) a network manager. A three-person plumbing firm sharing a printer and a folder of invoices runs perfectly well on peer-to-peer.
Two terms are often confused. Bandwidth is the maximum data rate of a link, measured in megabits per second (Mbps) or gigabits per second (Gbps). Latency is the time taken for a single packet to travel from sender to receiver, typically measured in milliseconds (ms). A LAN typically delivers 1 Gbps of bandwidth and a latency under 1 ms. A typical UK home broadband WAN connection delivers between 50 Mbps and 1 Gbps of bandwidth, with a latency of 10–25 ms to UK servers and 80–150 ms to North American servers. The latency cost is driven primarily by the speed of light through fibre and by the queuing delay at every router along the route — both of which are unavoidable on a packet-switched WAN.
Exam-style question (6 marks). A new sixth-form college has 60 staff and 800 students spread across two buildings on a single site. Compare a LAN and a WAN, and recommend which is appropriate for the college, justifying your choice.
Grades 3–4 response. A LAN is a network in one building. A WAN is a network over a big area like the internet. The college should use a LAN because the buildings are close together. They can share files and printers on the LAN.
Why this lands at 3–4: the candidate identifies the basic difference and reaches a recommendation, but uses imprecise terms ("big area"), gives no figures, and does not address ownership or third-party infrastructure.
Grades 5–6 response. A LAN covers a small geographical area such as a single building or campus and is owned by the organisation, whereas a WAN covers a large area, often using third-party infrastructure such as leased lines. A LAN typically offers higher bandwidth (1 Gbps Ethernet) and lower latency than a WAN. The college should use a LAN because the two buildings sit on a single site, so the college can run its own fibre between them and avoid the cost of a leased line. A LAN also lets the college centrally back up student work to a server.
Why this lands at 5–6: terminology is precise (bandwidth, latency, leased line), the recommendation is justified with reference to the scenario, and ownership is addressed.
Grades 7–9 response. A LAN is bounded by ownership of the physical infrastructure: the college can lay its own fibre or copper between the two buildings on its single site, place its own switches at the centre of a star topology, and use its own router as the gateway. A WAN, by contrast, traverses infrastructure owned by a telecommunications provider — typically a leased line or the public internet — which incurs a recurring monthly cost and adds latency measured in tens of milliseconds because packets must be packet-switched through several hops. For the college I would deploy a client-server LAN spanning both buildings, linked by a single fibre run between the two switches. This delivers gigabit bandwidth, sub-millisecond latency, central authentication and centrally managed backups for the 860 users. Only the connection to the public internet — required for student research, cloud services and email — would constitute a WAN link, terminated at a hardware firewall on the college's edge router. This separation lets the college apply tighter encryption and access controls to the WAN edge while keeping internal traffic on the high-speed LAN.
Why this lands at 7–9: the response uses precise terminology (packet, packet-switched, latency, bandwidth, topology, encryption), distinguishes the LAN from the WAN edge, and links every recommendation to a justification grounded in the scenario.
AQA alignment: This content is aligned with AQA GCSE Computer Science (8525) specification — specifically section 3.6 Computer networks (3.6.1 Networks and topologies, 3.6.2 Wired and wireless networks/protocols and layers, 3.6.3 Network security, 3.6.4 Systems architecture [client-server/P2P]). Assessed on Paper 2.