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Definition: LAN


(Local Area Network) A communications network that is confined to a building or complex. A LAN is a local network, whereas a WAN is a wide area network that spans long distances (see WAN). For example, a home network is a LAN; the Internet is a WAN.

The Transport
Data transfer over a LAN is managed by the TCP/IP protocol, and the physical transmission by cable is Ethernet. Mobile devices are connected by Wi-Fi, Ethernet's wireless counterpart. See twisted pair, TCP/IP and Ethernet.

The Wireless Router
A wireless router provides the required LAN hardware. The router creates the Wi-Fi hotspot and generally contains four Ethernet ports for cabling computers, printers and other devices to the LAN (see wireless router).

Clients and Servers
The "clients" in a LAN are the user's computers running Windows, Mac or Linux, while the "servers" are computers that hold programs and data shared by the clients. A printer is a type of server. See server and client/server.

In Companies: Thick and Thin Clients
In a company LAN, the user's computer may have many installed applications. These "thick" clients are the norm and contain full installations of software; however, some organizations use "thin" clients, whereby their PCs function like terminals to a server in the company datacenter or to servers on the Internet (see Remote Desktop Services and cloud computing). See thin client and client/server.

What enables sharing between machines is the network operating system in the server, which is geared to servicing multiple users. The network counterpart in each client machine can turn any user machine into a server for other users on the network. Folders are made "sharable" to allow file transfers.

In the Home: Thick Clients
In the home, the user's computer generally has several programs installed along with a Web browser that provides access to websites on the Internet. A major difference between a home LAN and a company LAN is that most homes do not use dedicated servers. See home network.




Clients and Servers in a Company LAN
This shows the private employee-facing side and the public-facing site. In large companies, multiple servers are used for each type of service. Today, it is rare to see a remote access server for analog dial-up connections.






Software in a Network Client
These are examples of common applications found in a user's machine. Printers may be connected to clients or servers wired or wireless (see print server).






Software in a Network Server
These are the common services in a network server.