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Definition: LAN


(Local Area Network) A communications network that is confined to a building or building complex. A LAN is a local network, whereas a WAN is a wide area network that spans long distances (see WAN). A wireless router generally has four or more LAN ports that create a small local network in the home or office (see wireless router).

The "clients" in a LAN are the user's computers running Windows, Mac or Linux, while the "servers" hold programs and data shared by the clients. Servers come in a wide range of sizes from PCs to mainframes (see server). The Internet hosts millions of them.

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

Thick and Thin Clients
In a company LAN, the client machines are typically Windows or Mac, possibly some Linux, and each platform has many installed applications. These "thick" clients are the norm; however, some organizations use "thin" clients, whereby their PCs function like terminals to a server (see Remote Desktop Services). See thin client and client/server.

The Network OS
The software that enables sharing between machines is the network operating system, typically Linux, Windows or Unix. The network OS is in the servers with a component in each client, allowing each to access files from each other. Folders must be made "sharable" for file transfers to work.




Clients and Servers in a 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 uncommon to see a remote access server for 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.