LAN vs WAN

A network can cover a tiny area or the whole planet. AQA names two key types:

• LAN — Local Area Network — covers a small geographic area such as one building or site (a school, an office, a home). The organisation usually owns the hardware (cables, switches) that connects it.
• WAN — Wide Area Network — covers a large geographic area, often across cities or countries. The internet is the biggest WAN. WANs usually rely on third-party infrastructure (e.g. telecoms companies) because no single organisation owns all the cables.

Definition to memorise: the difference is mainly geographic size and ownership — a LAN is small and owned by one organisation; a WAN is large and usually leased from telecoms providers.

Which type of network?

Star & bus topologies

A topology is the layout — how the devices are wired together. AQA requires two:

• Star topology — every device connects to a central switch (or hub). If one cable fails only that one device is affected. It's reliable and fast, but needs more cable and depends on the central switch.
• Bus topology — all devices share a single backbone cable with terminators at each end. It's cheaper and uses less cable, but if the backbone fails the whole network stops, and data collisions can occur when devices transmit at once.

Exam skill: be able to compare the two — cost, cabling, and what happens when a single cable fails.

Wired vs wireless

Devices can connect over cables or over radio. Each has trade-offs:

Tip: in exam answers, link the choice to the situation — a busy office server room favours wired Ethernet for speed and security; a café or phone favours wireless for mobility.

Your turn — count the layers

A network of networks

The internet is a single global WAN made by joining millions of smaller networks together — that's why it's called a "network of networks". No single company owns it; it works because everyone agrees to use the same protocols to talk to each other.

Key point: the internet is the biggest WAN; the World Wide Web (web pages accessed with HTTP) is just one service that runs over the internet — they are not the same thing.

TCP/IP, HTTP & HTTPS

A protocol is a set of agreed rules that lets devices communicate. Key ones for AQA:

• TCP/IP — the core rules for the internet. It is a stack of layers: TCP breaks data into and reassembles packets; IP handles addressing and routing.
• HTTP — HyperText Transfer Protocol, the protocol for requesting and delivering web pages.
• HTTPS — the secure version of HTTP; the data is encrypted so it can't easily be read if intercepted.

Why layers? Splitting the task into self-contained layers makes the system easier to develop and maintain — one layer can be changed without rewriting the others.

What is HTTP for?

Splitting data into packets

Data isn't sent in one big lump. In packet switching a message is split into small packets. Each packet carries a header with the destination address and a packet number, so:

• packets can travel independent routes across the network;
• if a route is busy or fails they can be rerouted;
• the packet numbers let them be reassembled in order at the destination.

Why send packets on different routes?

NICs, switches, routers & addresses

Networks need physical devices to connect things together:

• NIC (Network Interface Card) — lets a device join a network (wired or wireless); it holds the device's MAC address.
• Switch — connects devices on a single LAN and sends data only to the device it's meant for (using MAC addresses).
• Router — connects different networks together and routes packets between them (e.g. your home LAN to the internet), using IP addresses.
• Wireless Access Point (WAP) — lets Wi-Fi devices connect to a wired network.

Two addresses: a MAC address is the permanent hardware address built into the NIC; an IP address is the device's address on a network and can change.

The big contrasts to know

Before the games, lock in the comparisons AQA loves to ask about:

• LAN vs WAN — small & owned vs large & leased (the internet is a WAN).
• Star vs bus — central switch, one fault = one device vs shared backbone, one fault = whole network.
• Wired vs wireless — fast/secure vs convenient/mobile.
• MAC vs IP — permanent hardware address vs changeable network address.

Speed: a good exam answer names the feature and its consequence — e.g. "bus uses one backbone, so a single break stops the whole network."

Where does it belong?

Tap a description, then tap the category it belongs to.

Match term to meaning

Tap a description on the left, then its matching term on the right.

Star topology wiring

The big ideas to know

You've covered all of AQA 3.5 — networks, topologies, protocols, packet switching and hardware. Press Finish to see your score.