Network Fundamentals
A network is just devices connected so they can share data, but how they're connected, and who's in charge of coordinating that sharing, changes everything about cost, speed, and what happens when something breaks. This page makes those trade-offs concrete: you'll actually cut a cable and watch a network survive or fail.
LAN vs WAN
The difference is purely about geographic scale and who owns the connecting infrastructure.
| LAN (Local Area Network) | WAN (Wide Area Network) | |
|---|---|---|
| Scale | A single site: one building, one school, one home | Multiple sites, often across cities, countries, or the whole planet |
| Ownership | Usually owned entirely by the organisation using it | Usually leased from a third party (telecoms companies), since no single organisation owns the cables between cities |
| Speed | Generally very fast, short distances, dedicated cabling | Generally slower and more variable, shared infrastructure over long distances |
| Example | Every computer in one school building | The internet itself, or a company connecting offices in London and Tokyo |
The internet isn't a single network, it's a WAN made of millions of interconnected LANs and other WANs, which is exactly why the topologies and protocols on this page matter: something has to make all those independently-owned networks work together.
Topologies: proof by cutting a cable
A topology is just the shape of the connections. The real question that shape answers: when one link fails, physically, what happens to everyone else? Click any connection line below to cut it and see for yourself, not just read the answer.
Choose a topology
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Click any line in the diagram to cut it.
| Topology | What a single cable failure does | Cost to build |
|---|---|---|
| Star | Only the one disconnected device is affected, everyone else is fine, unless the central hub itself fails, which takes down everyone | Needs one cable run per device, more cable than bus |
| Bus | Catastrophic: the backbone splits into two halves that can no longer reach each other | Cheapest, one shared backbone cable |
| Ring | A single cut still leaves every device reachable, just going the other way around the ring | One cable per device, similar to star |
| Mesh | Barely noticeable, there are usually several alternative paths between any two devices | Most expensive by far, cable count grows fast as devices are added |
This is the real trade-off examiners want you to explain: resilience against cost. Mesh is the most resilient and the most expensive, bus is the cheapest and the most fragile.
Network hardware: who does what
Click a device to see what it actually does, and why it's not interchangeable with the others.
Client-server vs peer-to-peer
Same five devices, same file to distribute, two completely different architectures. Watch how long each takes and notice where the bottleneck sits.
Architecture
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Exam tips
- Client-server: a dedicated server holds and controls the data. Clients only ever talk to the server, never directly to each other. Easier to secure and manage centrally, but the server is a single point of failure and a bottleneck.
- Peer-to-peer: every device is both a client and a server (a "peer"). No central authority, peers share directly with each other, which is exactly how file-sharing protocols like BitTorrent distribute large files quickly.
- Neither is universally "better", it's a genuine trade-off between central control and distributed speed.