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.

Wireless networks transmit data using radio waves. For AQA 8525, Bluetooth is the required PAN example. Wi-Fi is a familiar example of a wireless LAN, useful for understanding wireless trade-offs.

Wi-Fi is the standard for wireless LANs. Devices connect to a wireless access point or router, which links them to the rest of the network or the internet. Wi-Fi operates over distances of tens to hundreds of metres depending on the environment.

Bluetooth operates over short distances (typically under 10 metres) and is primarily used for PANs — connecting peripherals such as keyboards, headphones, and smartwatches to a phone or computer.

Advantages of wireless over wired:

• No cabling — easier and cheaper to add or relocate devices
• Mobile devices (phones, tablets, laptops) can move freely within range
• No installation disruption in buildings where running cables is difficult

Disadvantages of wireless compared to wired:

Issue	Detail
Speed	Generally slower than an equivalent wired connection
Security	Signals travel through air and can be intercepted if not encrypted
Interference	Affected by walls, microwaves, neighbouring wireless networks
Range	Signal strength drops with distance; dead zones can occur
Congestion	Many devices sharing one access point reduce bandwidth per device

Connecting a network to the internet or to external devices introduces security risks. AQA 8525 requires knowledge of four network security methods.

Firewall — a system (hardware, software, or both) that monitors network traffic and permits or blocks packets according to a set of security rules. Firewalls sit between a trusted internal network and an untrusted external one (the internet). A rule might allow outbound web traffic while blocking all uninitiated inbound connections.

MAC address filtering — every network interface card has a unique hardware identifier called a MAC address (Media Access Control address). A router or wireless access point can maintain a list of approved MAC addresses and refuse connection requests from any device not on that list.

Method	What it controls	Limitation
Firewall	Type and source of traffic entering or leaving the network	Cannot stop threats that match the patterns of allowed traffic
MAC filtering	Which devices are permitted to connect to the network	MAC addresses can be spoofed (impersonated) using software tools

Both methods contribute to a layered security approach. No single measure is sufficient on its own.

Authentication verifies the identity of a user or device before granting network access. At a minimum, this means requiring a password to connect. Stronger authentication uses certificates, two-factor methods, or biometric checks.

Authentication prevents unauthorised users from accessing a network even when they are physically present — for example, in range of a wireless access point.

Encryption transforms data into an unreadable format (ciphertext) that can only be decoded with the correct key. On a network, encryption ensures that intercepted data cannot be read.

Encryption context	What it protects
WPA2 / WPA3	Data transmitted over a wireless LAN
HTTPS	Data between a browser and a web server
VPN	All traffic between a device and a remote private network

Without encryption on a wireless network, anyone in range can intercept and read all transmitted data — including passwords and personal information — as plain text.

Authentication confirms who you are. Encryption protects what you send. Both are needed for a fully secure network connection.

1. Confusing LAN and WAN by size alone

The key distinction between LAN and WAN is ownership and infrastructure management, not just physical size. A LAN is typically owned and managed by a single organisation. A WAN spans infrastructure owned by multiple organisations or telecoms providers. Two offices in the same city connected by leased lines form a WAN, even though they are geographically close.

2. Saying wireless networks are always less secure

Wireless networks with proper encryption (WPA2 or WPA3) can be just as secure as wired networks. The security risk is from poor configuration — an open, unencrypted access point is vulnerable; a properly configured encrypted one is not.

3. Claiming MAC filtering cannot be bypassed

MAC filtering reduces casual unauthorised access, but MAC addresses can be spoofed using freely available software tools. It is a useful layer but not an absolute barrier.

4. Describing Bluetooth as a WAN or LAN technology

Bluetooth is a PAN technology with a typical range of under 10 metres. It is designed for short-distance device-to-device connections, not local or wide-area networking.

5. Treating authentication and encryption as the same thing

Authentication verifies identity — who is allowed to connect. Encryption protects data in transit — preventing interception from being useful. They are separate mechanisms targeting different threats and are both necessary in a secure network.