Theory
What happens when you click a link
You tap a link on your hostel laptop, and a moment later a website appears. In between, your request travelled across one or more networks, out of your room, through devices you never see, to a server perhaps thousands of kilometres away, and back.
This whole subject follows that journey. To begin, we need the basic idea: what a network actually is, and the main ways networks are classified. Everything later, topologies, devices, the OSI layers, hangs off this foundation.
Theory
What a network is
A computer network is a collection of two or more computing devices connected together so they can communicate and share. What do they share? Data (files, messages), resources (a printer, an internet connection), and services (a website, email).
Without a network, each computer is an island. Connect them, and a student can send a file to a friend, a lab can share one printer, and any device can reach the internet. The reasons to build a network all come down to this: sharing resources and information, and enabling communication between people and machines.
Theory
Two ways to classify networks
Networks are sorted along two different axes, and it helps to keep them separate.
By size (scale): how much geographic ground the network covers, from a single room to the whole planet. This gives the familiar categories LAN, MAN, and WAN, which a later topic covers in detail.
By architecture (how devices relate): whether there is a central server or not. In a client-server network, dedicated servers provide services and other machines (clients) request them. In a peer-to-peer network, all devices are equals, each can both offer and request directly, with no central server.
At a glance
| Aspect | Client-server | Peer-to-peer |
|---|---|---|
| Roles | Dedicated server(s) serve many clients | All nodes are equal peers |
| Control | Central: managed from the server | Distributed: no central authority |
| Example | A website's server and its visitors | Direct file sharing between two laptops |
| Scales to | Large, managed networks | Small, informal groups |
Quiz
A website runs on a dedicated machine that many visitors' browsers connect to and request pages from. What network architecture is this?
- Peer-to-peer, because all devices are equal
- Client-server, because a dedicated server provides services to requesting clients
- A topology, not an architecture
- A LAN, because it is on the internet
Show the answer
Client-server, because a dedicated server provides services to requesting clients
This is client-server: a dedicated server (the website's machine) provides a service, and many clients (the visitors' browsers) request it, which is exactly the client-server pattern the whole web is built on. Option A is wrong: the devices are NOT equal here, one machine is the server and the rest are clients, so it is not peer-to-peer (where every node is an equal peer sharing directly). Option C confuses two ideas: architecture (client-server vs peer-to-peer) is about roles, while topology is about physical shape, a different classification. Option D misuses scale: LAN/MAN/WAN describe size, not the client-server relationship, and a website is reached over a WAN (the internet), not a LAN. Architecture is about roles: one server serving many clients.
Think first
Why connect computers at all, instead of using standalone machines?
What do you actually gain by networking computers rather than keeping each one separate? Then tap.
Show the answer
You gain SHARING and COMMUNICATION, which multiply what each machine can do. Standalone computers are isolated: to move a file you would carry a USB stick, every machine would need its own printer, and each would need its own separate internet link. Networking changes that completely. RESOURCE SHARING means one printer, one internet connection, or one storage server can serve a whole lab or office, saving cost and effort. DATA SHARING means files and databases live in one place and everyone can reach the current version, no more emailing copies around. COMMUNICATION means people can message, video-call, and collaborate in real time. CENTRAL MANAGEMENT means an administrator can back up, secure, and update many machines from one point. And ACCESS TO SERVICES, the web, email, cloud apps, only exists because networks connect your device to servers everywhere. In short, a network turns a room full of separate computers into a single cooperating system whose whole is far greater than its parts. That multiplier, shared resources, shared data, and human communication, is why virtually every computer today is networked. Connection creates capability.
Summary
Key takeaways
- A computer network is two or more connected devices that can communicate and share data and resources.
- Networking exists for sharing (files, printers, internet) and communication between people and machines.
- Networks are classified two ways: by size (scale) and by architecture (how devices relate).
- By size: LAN, MAN, WAN (covered in detail in a later topic).
- By architecture: client-server (dedicated servers serve clients) vs peer-to-peer (all nodes equal, sharing directly).
- The web is a giant client-server system: servers provide pages, browsers (clients) request them.
- Memory hook: a network is devices connected to share; sort them by size and by client-server vs peer-to-peer.