(redirected from LAN (disambiguation))
Also found in: Dictionary, Thesaurus, Medical, Financial, Wikipedia.


(computer science)



(Local Area Network) A communications network that is typically confined to a building or premises. The "clients" are user workstations running the Windows, Mac or Linux operating systems, while the "servers" hold programs and data shared by the clients. Servers come in a wide range of sizes from PC-based servers to mainframes.

A LAN is a local network, whereas a WAN (wide area network) spans long distances. See WAN.

Thick and Thin Clients
In a company LAN, the client machines are mostly Windows PCs; however, Macs are widely used and may be the only platform in some companies. Each PC or Mac contains a variety of installed applications. These "thick" clients are the norm; however, some organizations use "thin" clients, which perform no business processing on their own. For example, a Windows PC can be turned into an input/output terminal (see Remote Desktop Services). See thin client.

The Network OS
The software that enables sharing is the network operating system in the servers, typically running Windows, Linux or Unix. A component part resides in each client operating system, which allows the application in the client to read and write data from the server as if it were on the local machine.

Client workstations can also function as a server, allowing users access to data on another user's machine. These "peer-to-peer" networks are often simpler to install and manage, but dedicated servers provide better performance and handle higher transaction volume. In large networks, multiple dedicated servers are used.

The Transport
Data transfer over the LAN is managed by the TCP/IP transport protocol, and the physical transmission is handled by Ethernet. The actual communications path is twisted pair wire or optical fiber, which physically interconnects each client, server and network device. Using Wi-Fi, the wireless counterpart of Ethernet, clients and servers can connect without cables. See WAN, TCP/IP, Ethernet and client/server.

Clients and Servers in a LAN
This overview of clients and servers in a LAN shows the private employee-facing side and the public-facing site. In large companies, multiple servers are used for each type of service.

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.