Networks, Network Types and Protocols
What Is a Computer Network?
A computer network is two or more devices linked so they can exchange data and share resources. Networks range from two laptops connected at home to millions of devices spanning the globe. Without networks, every device would be an island: no email, no streaming, no online banking, no shared printing in a school.
Networks offer significant advantages: files can be shared between users without physical media, a single internet connection can be shared across many devices, centralised storage makes backups easier, and users can communicate in real time. The disadvantages include the cost of setting up and maintaining the hardware, the risk of spreading malware across connected devices, and the need for security measures to protect shared data.
The three main network types are: PAN (Personal Area Network) — a very short-range network between personal devices, typically using Bluetooth; LAN (Local Area Network) — covers a small area such as a school or office and is usually owned by one organisation; WAN (Wide Area Network) — covers a large geographic area and is typically under collective or distributed ownership.
PAN, LAN and WAN
A PAN (Personal Area Network) connects devices within the range of a single person, typically up to about ten metres. Bluetooth is the technology you need to know for PANs: it connects a smartphone to wireless earbuds, a laptop to a wireless keyboard, or a smartwatch to a phone. PANs are low-cost and require no infrastructure, but they are only suitable for personal device pairing, not for sharing resources across an organisation.
A LAN (Local Area Network) covers a relatively small area — a school, a hospital ward, an office floor. The hardware (cables, switches, routers) is usually owned and managed by the organisation itself. LANs typically offer high-speed connections because devices are physically close together and the network infrastructure is dedicated to that organisation.
A WAN (Wide Area Network) covers a wide geographic area, connecting multiple LANs across cities, countries, or continents. WANs rely on third-party telecommunications infrastructure — leased telephone lines, undersea cables, or satellite links — meaning no single organisation owns the whole network. The internet is the largest example of a WAN.
LANs cover a small area; WANs cover a large area. LANs are typically owned by one organisation; WANs use infrastructure owned by multiple parties. LANs tend to offer higher speeds and lower latency because devices are physically close; WAN speeds vary and depend on the quality of telecommunications links between sites. Setting up a LAN is relatively low-cost; connecting to a WAN typically involves paying for leased lines or internet service provider fees. Both can use wired or wireless technology.
Wired vs Wireless Networks
Wired networks use physical cables. Fibre optic cable carries data as pulses of light and can achieve very high speeds over long distances with minimal signal degradation — it is used for backbone connections between buildings and for connecting homes to the internet. Copper cable (such as twisted-pair Ethernet cable) is cheaper and easier to install, but its speed and range are more limited and it is more susceptible to electrical interference.
Wireless networks transmit data using radio waves. The main advantage is mobility: devices can connect from anywhere within range without needing a physical cable. This makes wireless ideal for laptops, tablets and smartphones. However, wireless connections are generally slower and less reliable than wired equivalents, more susceptible to interference from walls and other devices, and potentially less secure because any device within range can attempt to connect. Wireless signals can also be degraded by distance from the access point.
Network Protocols
A network protocol is an agreed set of rules for communication. Without protocols, devices from different manufacturers using different operating systems could not exchange data reliably. Protocols define how data is formatted, addressed, transmitted, and error-checked.
The protocols you must know: IP (addresses and routes data packets across networks), TCP (sets up the connection and ensures reliable delivery), HTTP (transfers web pages), HTTPS (encrypted web transfer), SMTP (sends emails), IMAP (receives and manages emails on a mail server).
IP (Internet Protocol) — assigns a unique address to every device on the internet and handles the addressing and routing of data packets. When data is sent across the internet, IP ensures each packet is labelled with the source and destination address so routers can forward it along the correct path.
TCP (Transmission Control Protocol) — works with IP to set up a reliable connection between two devices. TCP breaks data into packets, numbers them, and checks that all packets arrive and are reassembled correctly. If a packet is lost, TCP requests it to be sent again.
HTTP (Hypertext Transfer Protocol) — defines how web browsers and web servers exchange web pages. When you type a website address, your browser sends an HTTP request; the server responds with the page content.
HTTPS (Hypertext Transfer Protocol Secure) — an encrypted version of HTTP. The data exchanged between browser and server is scrambled so it cannot be read if intercepted. Essential for banking, shopping and login pages.
SMTP (Simple Mail Transfer Protocol) — used to send emails from a client to a mail server, and between mail servers. When you press Send, your email application uses SMTP.
IMAP (Internet Message Access Protocol) — allows an email client to access and manage email stored on a remote mail server. Emails remain on the server and are synchronised across all devices. This is important: note that POP3 is not on the required protocol list for this specification — IMAP is the email-receiving protocol to know.