Network types: LAN, WAN, MAN, VPN, SAN, CAN, intranet and extranet

Classified by size

LAN: Local Area Network

A LAN covers a small area such as one building or a group of nearby buildings. It is usually privately owned and offers high data rates. Most LANs today use Ethernet for wired connections and Wi-Fi for wireless. LANs are designed to:

• work within a limited area;
• give many users fast, shared access;
• be controlled privately by local administrators;
• provide full-time access to local services such as file servers and printers.

Typical LAN devices: switches, access points and (in older networks) hubs, bridges and repeaters.

WAN: Wide Area Network

A WAN covers a large area: a country, a continent or the whole world. It joins LANs together over long distances, usually using lines rented from service providers. WAN links have traditionally been slower and more expensive than LAN links. The internet is the largest WAN. Typical WAN devices: routers, modems and service-provider equipment.

MAN: Metropolitan Area Network

A MAN sits between a LAN and a WAN: it covers a town or city, for example linking a university's campuses or a city's offices with high-speed fibre.

PAN: Personal Area Network

A tiny network around one person: a phone connected to earbuds, a smartwatch or a laptop over Bluetooth.

Classified by purpose

VPN: Virtual Private Network

A VPN uses a public network, usually the internet, to give remote offices or individual users secure access to their organisation's private network. Traffic is encrypted, so anyone in between sees only scrambled data. VPNs became essential as more people worked from home and branch offices replaced expensive private lines. Benefits: lower cost than private circuits, easy to scale, and strong security when configured well. Learn how they work in IPsec explained.

VAN: Value-Added Network

A network run by a third party that adds services on top of basic connectivity, historically used by businesses to exchange orders and invoices electronically.

SAN: Storage Area Network

A SAN is a dedicated high-speed network that connects servers to shared storage. Servers see SAN storage as if it were a local disk, because data is accessed in blocks rather than as files. Benefits:

• storage is managed centrally;
• space can be moved between servers without moving cables or disks;
• high performance and easy growth.

CAN: Controller Area Network

A CAN bus is a simple, robust network that lets microcontrollers, sensors and actuators talk to each other in real time without a central computer. It was developed for vehicles, where it connects parts such as the engine control unit, brakes and airbags, and is now also used in factories, medical equipment and building systems.

Classified by who can use it

• Intranet: a private network for people inside one organisation, protected from outsiders by a gateway and firewall. It typically uses private IP ranges such as 192.168.0.0/16.
• Extranet: part of an organisation's network opened securely to selected outsiders, such as suppliers or partners, who log in with their own accounts.
• Internetwork: two or more separate networks connected together, often of different types. The internet is the largest internetwork of all.