LAN, which stands for Local Area Network, is a medium-sized computer network featuring data transmission rates that are faster in comparison to Wide Area Networks (WAN), and unlike WANs, leased telecommunication lines are unnecessary in LANs.
Introduced in the late 1970's, LANs are generally used for the home or office, or a group of buildings. Of the various LAN technologies, Ethernet over unshielded twisted pair cabling and wireless fidelity (Wi-Fi) are currently the most commonly used. Other technologies include Attached Resource Computer Network (ARCNET) and Token Ring among others.
Smaller LANs commonly consist of one or more switches linked to each other, with one usually connected to a router, cable modem or Digital Subscriber Line (DSL) modem for internet access, while larger LANs use redundant links with switches, preventing loops by making use of the spanning tree protocol.
Larger LANs also use Quality of Service (QoS) to manage different traffic types, and segregate them through Virtual LAN (VLAN). At present, switched Ethernet is the most common data link layer protocol, and Internet Protocol (IP) as a network layer protocol.
However, certain niche areas may use other options. Leased lines, leased services, and the process of tunneling through the use of virtual private network (VPN) technologies are all means used to connect LANs with other LANs.
LANs were developed with the objective of creating high-speed links among several large central computers at one site. Prior to the late 1970's, a site may have had only one central computer that was accessed by users through computer terminals over simple low-speed cabling.
Through the increasing popularity of Control Program/Monitor (CP/M) and Disk Operating System (DOS)-based personal computers later in the 1970's, a single geographical location was able to accommodate dozens or possibly hundreds of personal computers.
Networking these computers became in-demand in order to enable sharing of disk space and laser printers. This concept was met with much enthusiasm by computer industry pundits.
The incompatibility of physical layer and network protocol implementations, as well as the confusion over how to best share resources, proved to be problems in the concept of the LAN.
Each vendor usually provided its own type of network card, cabling, protocol and network operating system (OS). This problem would be solved through the inception of Novell NetWare in 1983.
The numerous competing card and cable types had support from Novell NetWare, and it also provided a remarkably more sophisticated OS, in comparison to its competitors.
NetWare went on to achieve much popularity in the personal computer LAN business up until the mid-1990's, dominating other competitors such as Banyan Vines and 3Com.
In the 1990's came the introduction of Windows NT Advanced Server and Windows for Workgroups by the software company Microsoft.
Software vendors including Hewlett-Packard, NeXT, Sun Microsystems, Intergraph, Apollo and Silicon Graphics had UNIX computer workstations that began using Transmission Control Protocol/Internet Protocol (TCP/IP)-based networking. This contributed to the domination of the TCP/IP protocol over other protocols such as Internetwork Packet Exchange (IPX), NetBIOS Frames (NBF) protocol and AppleTalk.