LAN - Local Area Network..

A local area network is a computer network covering a small geographic area, like a home, office, or group of buildings. Current LANs are most likely to be based on switched IEEE 802.3 Ethernet technology, running at 10, 100, 1,000 or 10,000 Mbit/s, or on IEEE 802.11 Wi-Fi technology. Each node or computer in the LAN has its own computing power but it can also access other devices on the LAN subject to the permissions it has been allowed. These could include data, processing power, and the ability to communicate or chat with other users in the network.

The defining characteristics of LANs, in contrast to WANs (wide area networks), include their much higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines.

Technical aspects

Although switched Ethernet is now the most common data link layer protocol (OSI 7-Layer Model), and IP as a network layer protocol, many different options have been used (see below), and some continue to be popular in niche areas. Smaller LANs consist of a few switches typically connected to each other and with one connected to a router, cable modem, or DSL modem. A traditional model of access, distribution, and core switches was popularized by Cisco Systems and has been in use for many years.

Larger LANs are characterized by distributing Ethernet traffic roles within the network. Each layer aggregates traffic of the layer below it and will typically maintain redundant links with switches capable of quality of service and spanning tree protocol to prevent loops and the recovery of failed uplinks.

LANs may have connections with other LANs via routers and leased lines. Traditionally, the network connecting two or more LANs is referred to as the WAN (Wide Area Network). Recently, service providers have begun to offer additional services to link LANs together. These technologies, such as Metropolitan Area Networks (MANs), and MPLS/VPN services have diversified the standard model of interconnecting sites. There are also methods of connecting LANs together through the use of Internet connections, VPN software or hardware, and 'tunneling' across the Internet using VPN technologies.

Topology, protocols and media (The cables, like CAT5, or radio waves that connect devices in the LAN) are the characteristics that differentiate LANs.

Home networks

With the proliferation of computers and IT devices in the modern home has come the frequent use of LANs to connect them together. Many of these home LANs are wireless, using the 802.11g/b wireless standards