Computer Networks: LAN, WAN and Wireless

A computer network is two or more computers connected together to share resources and communicate.

Networks allow devices to share files, printers, internet connections, and data without transferring it manually on removable media. They underpin almost every modern computing environment, from a home router connecting a handful of devices to the global infrastructure of the internet.

Advantages of computer networks:

• Files and hardware resources (printers, storage) can be shared between devices
• A single internet connection can be shared across multiple devices
• Centralised management of data, software, and security — especially valuable in schools and businesses
• Communication between users (email, messaging, video calls) requires a network

Disadvantages of computer networks:

• Require hardware (routers, switches, cables or wireless equipment) and ongoing maintenance
• A network fault or failure can affect all connected devices simultaneously
• Shared access increases exposure to security threats — one compromised device can affect others
• Performance degrades under high traffic when many users or large transfers compete for bandwidth

The same properties that make networks useful — shared access and connectivity — are precisely what create the security challenges that network defences address.

Networks are classified by their geographic scope and how their infrastructure is owned and managed.

Type	Full name	Scale	Typical example
PAN	Personal Area Network	A few metres	Bluetooth headphones connected to a phone
LAN	Local Area Network	A building or campus	A school network or home Wi-Fi
WAN	Wide Area Network	Cities, countries, or globally	The internet; a company's offices in multiple cities

PAN — typically uses Bluetooth technology and connects devices owned by a single person over very short distances (under ~10 metres). A phone connecting to a wireless keyboard, earbuds, or smartwatch forms a PAN.

LAN — covers a small geographic area, typically within a single building or site. A LAN is owned and managed by a single organisation. Devices on a LAN can communicate directly without going via the internet.

WAN — spans a wide area, using infrastructure owned by multiple organisations or telecommunications providers. The internet is the largest WAN, connecting millions of individual networks globally. Unlike a LAN, no single entity owns or controls the whole WAN.

Wired networks transmit data as electrical signals through copper cable or as light pulses through fibre optic cable.

Property	Copper (twisted pair / coaxial)	Fibre optic
Transmission medium	Electrical signal	Light
Maximum speed	Up to several Gbps	Hundreds of Gbps
Interference	Susceptible to electromagnetic interference	Immune to electromagnetic interference
Cost	Cheaper, widely available	More expensive; specialist installation
Flexibility	Easy to install and terminate	Fragile; needs careful handling
Typical use	Internal LAN cabling, short runs	Long-distance links, internet backbones

Advantages of wired over wireless:

• Faster and more consistent data transfer speeds
• More secure — signals cannot be intercepted without physical access to the cable
• No interference from radio signals, walls, or other wireless devices
• Lower and more predictable latency

Fibre optic cables form the backbone of the internet (including undersea cables between continents) because of their high bandwidth and immunity to electromagnetic interference.