Local Area Network (LAN)
LOCAL AREA NETWORK (LAN)
Local area networks, more commonly known as LANs, typically connect a geographically restricted group of clients, such as a group of employees in an office building, to a server. Clients simply are stand-alone personal computers (PCs) or other types of workstations, while servers are faster computers that house the programs and data distributed to the workstations. Servers either can be mainframe computers or sophisticated PCs. Several network operating systems exist, including Microsoft Windows NT, Macintosh's AppleTalk, and Novell's NetWare. These systems are housed directly within the machine acting as the server. Related software within each client allows it to access programs and data on the server, just as if the applications and files were actually on the hard drive of the client's machine. Some LANs also allow clients to communicate with each another via e-mail messages or real-time chat programs. Particularly large LANs may require several dedicated servers, while smaller LANs may actually be nothing more than a peer-to-peer network, in which a few workstations act as servers by allowing the users at each station to access files and applications on one another's machines.
In some cases, clients must access a server for all the software applications and data files they need. However, LANs also can be set up with servers that only provide select applications to clients. For example, some workstations equipped with their own printers may access their LAN each time they perform a word processing or data processing function, yet not need the LAN when actually printing documents. Other LANs may link printers directly to servers to allow a single printer to be shared by several workstations, a cost saving technique used by many corporations, libraries, schools, and other institutions.
To actually transfer data, LANs use protocols like IBM's Token Ring, which typically arranges computers in a ring or star shape to facilitate connection. Ethernet, which was developed by Bob Metcalfe and Xerox Corp. in the early 1970s, is the most common LAN protocol. It uses coaxial cables or twisted pair wires to connect machines arranged most commonly in a bus layout, where all computers are connected to a central line. Another protocol, Fiber Distributed-Data Interface (FDDI), uses fiber optic lines to connect up to thousands of workstations as far as 124 miles apart. Networks much bigger than this typically begin to connect LANs together to form a wide-area network, or WAN. Data transmission speeds for these technologies range from roughly 1 million bytes per second for Ethernet and Token Ring to 10 million bytes per second for FDDI. Efforts to improve network speed have resulted in the creation of new technologies like Fast Ethernet, the even faster Gigabit Ethernet, and Fast Token Ring.
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SEE ALSO: Communication Protocols; Wide Area Network (WAN)
local area network
local area network
lo·cal ar·e·a net·work (abbr.: LAN) • n. a computer network that links devices within a building or group of adjacent buildings. Compare with wide area network.