Introduction to networks

The essentials

A computer network is a group of two or more computers and other devices (nodes) connected to share data and resources such as printers and Internet access. Networking began with ARPANET in 1969, a project of the US Department of Defense that connected a few universities and research centres. Over time many networks were interconnected, and this network of networks grew into the Internet.

Key points

• Benefits of networks: resource sharing, communication (email, chat), data sharing and centralised backup.
• PAN (Personal Area Network): connects devices around one person, such as a phone, laptop and wireless earphones, often using Bluetooth or USB.
• LAN (Local Area Network): covers a small area such as a room, building or campus. It is usually privately owned and gives high speed.
• MAN (Metropolitan Area Network): covers a city or town, for example a cable TV network or connected branches across a city.
• WAN (Wide Area Network): covers a large area such as a country or continent, often connecting many LANs and MANs. The Internet is the largest WAN.
• In general, as the area increases (PAN → LAN → MAN → WAN), the cost and complexity rise while speed and reliability usually fall.
• A node is any device connected to the network; a server provides services, and a client uses them.

Exam tips

• Case questions describe distances: computers within one school building form a LAN; offices in different cities linked together form a WAN.
• Remember the chain: ARPANET → interconnected networks → Internet.

Common mistakes

• Calling the Internet a LAN or MAN. It is a global WAN made of many interconnected networks.
• Thinking a network must be wired; Wi-Fi LANs and Bluetooth PANs are wireless.