What you'll learn
A network is two or more computers or devices connected so they can share data and resources. This guide covers the types of network (LAN and WAN), the hardware that builds them (routers, switches, access points, network interface cards and modems), wired and wireless connections, network models (client-server and peer-to-peer), the star topology, and how the internet works — IP addresses, DNS, protocols, packets and bandwidth. It also covers the difference between the internet and the World Wide Web, intranets, VPNs and mobile broadband.
Networking questions mix definitions with practical judgement: why an office might choose wired over wireless, why a school uses a client-server network, how long a download will take, or why a household's video keeps buffering. You need both the vocabulary and the reasoning.
Key terms and definitions
Network — Two or more devices connected to share data and resources.
LAN (local area network) — A network covering a small area, such as one building or site, usually owned by one organisation.
WAN (wide area network) — A network covering a large geographical area, often linking LANs; the internet is the largest WAN.
Router — Forwards data between networks, such as between a home network and the internet.
Switch — Connects devices within a LAN and sends data only to the device it is addressed to.
Wireless access point (WAP) — Lets wireless devices connect to a wired network.
NIC (network interface card) — Hardware that lets a device connect to a network; each has a unique MAC address.
Modem — Converts digital data into signals that can travel over lines such as telephone cables, and back again.
IP address — A number that identifies a device on a network.
DNS (Domain Name System) — Converts domain names such as example.com into IP addresses.
Protocol — A set of rules that devices follow to communicate.
Bandwidth — The amount of data that can be transmitted per second, measured in bits per second.
Packet — A small unit of data sent across a network, with addressing information.
Intranet — A private network using internet technologies, open only to an organisation's members.
VPN (virtual private network) — An encrypted connection over the internet to a private network.
Core concepts
Why network computers?
Networks allow users to share files, printers and internet connections, communicate by email and messaging, log in from any machine, and have data backed up centrally. The costs are the equipment, the need for technical staff, the risk that a fault can affect many users, and security risks: malware and intruders can spread across a network.
LANs and WANs
A LAN covers a single site, such as a school, office or home. The organisation owns the cabling and equipment. LANs are fast and relatively cheap to run.
A WAN connects sites that may be in different towns or countries. Organisations usually lease connections from telecommunications companies or connect over the internet. A business with offices in two countries uses a WAN so staff can share files, email and systems between sites, though long-distance links cost more and are often slower than a LAN.
Network hardware
- NICs connect each device to the network, by cable or wirelessly.
- Switches connect devices in a LAN. A switch learns which device is on each port and forwards data only to the intended recipient, reducing unnecessary traffic.
- Routers connect different networks and choose where to send data next. A home "router" usually combines a router, switch, wireless access point and modem in one box.
- Wireless access points spread Wi-Fi coverage. Several may be used across a large building, and mesh systems use multiple units to cover a whole home.
- Modems convert between the digital data computers use and the signals carried on telephone or cable lines.
Wired and wireless connections
Wired (Ethernet) connections use copper or fibre-optic cables. They are faster, more reliable, suffer less interference and are harder to intercept. However, installing cables costs money and devices cannot move freely.
Wireless (Wi-Fi) uses radio waves. Devices can move around freely and no cables are needed, which suits laptops, phones and older buildings. However, Wi-Fi is usually slower, signals weaken with distance and through walls, other devices can cause interference, the bandwidth is shared between all connected users, and data must be encrypted to stop it being intercepted.
Bluetooth is a short-range wireless technology for linking nearby devices directly, such as headphones, keyboards and smartwatches. It uses very little power, which is why it suits battery-powered accessories.
Mobile broadband (4G and 5G) provides internet access over mobile phone networks. 5G offers higher bandwidth and very low latency (delay), which helps applications that need near-instant responses.
Network models
In a client-server network, one or more powerful servers provide services — file storage, logins, printing, email — to client computers. Security, user accounts, software and backups are managed centrally, which suits large organisations such as schools. Servers are expensive, need skilled staff, and if a server fails, many users are affected.
In a peer-to-peer network, every computer is equal and shares its own resources. There is no dedicated server, so it is cheap and simple to set up, which suits small homes and offices. As the network grows, it becomes hard to manage security and backups, since each computer must be looked after individually.
The star topology
In a star network, each device connects by its own cable to a central switch. If one cable fails, only that device is affected, and faults are easy to find. Adding devices is simple. The weakness is the central switch: if it fails, the whole network goes down, and more cable is needed than in some other layouts.
How the internet works
The internet is a worldwide network of networks. The World Wide Web is a collection of linked web pages accessed over the internet using browsers. Email, streaming and online gaming also use the internet but are not the web.
Each device has an IP address. Because people remember names more easily than numbers, DNS servers translate domain names into IP addresses when you type a web address.
Data is split into packets. Each packet carries the destination and source addresses and a sequence number. Packets may travel by different routes and are reassembled in order at the destination. If one is lost, only that packet needs resending. The internet has many alternative routes between networks, so traffic can be sent around faults and congestion.
Protocols make communication possible between devices from different manufacturers. Examples: TCP/IP for sending data across the internet, HTTP for web pages, and HTTPS, which encrypts data between the browser and the website so passwords and card details cannot be read if intercepted.
A URL is the full address of a resource, such as https://www.example.com/page. An ISP (internet service provider) is a company that sells internet access.
Bandwidth and speed
Broadband speeds are advertised in megabits per second (Mbps). Real speeds are often lower because of congestion at busy times, distance from the exchange, older copper lines, Wi-Fi interference, and sharing the connection between several users. Rural areas often have slower connections because they are far from exchanges and installing fibre to scattered homes costs more.
Intranets and VPNs
An intranet uses web technology but is accessible only to members of an organisation. It is used to share internal news, policies and forms. A VPN creates an encrypted "tunnel" over the internet, letting remote workers access internal systems securely as though they were in the office.
Types of internet connection
Homes and businesses connect to the internet in several ways:
- Fibre-optic broadband carries data as pulses of light. It offers the highest speeds and is least affected by distance. "Full fibre" runs all the way to the building; some connections use fibre to a street cabinet and copper for the final stretch.
- Copper telephone-line broadband uses existing phone lines. It is widely available but slower, and speed falls the further the building is from the exchange or cabinet.
- Cable broadband uses the coaxial cables of cable television networks.
- Mobile broadband (4G/5G) uses phone networks; it is convenient and portable but can be affected by signal strength and data limits.
- Satellite broadband reaches remote areas without cables, but the distance to the satellite can cause noticeable delay (latency), which affects video calls and gaming.
The best choice depends on availability, required speed, reliability, latency and cost. A rural home might choose satellite or 4G because fibre is not available; a business doing frequent video conferencing would prioritise a fast, low-latency fibre connection.
Worked examples
Example 1: Download time
How long will it take to download a 600 MB file on a steady 40 Mbps connection?
Convert megabytes to megabits: 600 × 8 = 4,800 megabits. Time = 4,800 ÷ 40 = 120 seconds (2 minutes). Forgetting to multiply by 8 gives the wrong answer of 15 seconds.
Example 2: Choosing a network model
A school has 500 computers used by 1,200 pupils. Explain why a client-server network is suitable. (3 marks)
Answer: Pupils can log in on any computer and access their own files, which are stored on the server (1). Security, user accounts and software can be managed centrally by technicians (1). Backups of all pupils' work can be made centrally, so work is not lost if one computer fails (1).
Example 3: Wired or wireless
An architects' office is replacing its network. Its designers use powerful desktops that never move and transfer very large files. Recommend wired or wireless.
Answer: Wired. The desktops do not move, so the flexibility of Wi-Fi is not needed. Wired Ethernet offers higher, more reliable speeds for large files, with less interference and better security. Wi-Fi could still be added for visitors' and staff phones.
Example 4: Slow streaming
A family finds video buffering every evening when everyone is online. Explain why.
Answer: The household's bandwidth is shared between all the devices. When several people stream, game and download at once, total demand exceeds the available bandwidth, so each device gets a smaller share. Evening is also peak time, when congestion on the wider network is highest.
Common mistakes and how to avoid them
- Saying the internet and the web are the same. The web is one service that runs on the internet.
- Confusing routers and switches. Switches connect devices within a LAN; routers connect different networks.
- Mixing bits and bytes in speed calculations. Speeds are in bits per second; file sizes are usually in bytes. Multiply bytes by 8.
- Saying wireless is "always worse". It has real advantages; give a balanced comparison.
- Forgetting the central weakness of a star network — the switch.
Exam technique for "Networks: LAN, WAN and the Internet"
- For hardware questions, say what the device does and where it sits (within a LAN, between networks).
- For comparisons (wired/wireless, client-server/peer-to-peer), use consistent criteria: speed, cost, security, reliability, management, flexibility.
- In calculations, write the conversion step clearly and give units.
- In "explain how" questions about the internet, sequence the steps: DNS lookup → packets sent with addresses → routed across networks → reassembled.
Quick revision summary
- LAN = one site; WAN = large area; the internet is the biggest WAN.
- Switch within a LAN; router between networks; WAP for wireless; NIC in each device; modem converts signals.
- Wired: faster, more secure, less flexible. Wi-Fi: flexible, cheaper to set up, slower, shared and needs encryption. Bluetooth: short-range, low power.
- Client-server: central control, costly. Peer-to-peer: cheap and simple, hard to manage at scale.
- Star: one cable fault affects one device; the switch is a single point of failure.
- IP addresses, DNS, packets and protocols (TCP/IP, HTTP, HTTPS) make the internet work.
- Download time = (file size in bits) ÷ (speed in bits per second).