Local networks

A local area network (LAN) is the set of hardware and software resources that enable a group of computer devices to communicate. It is characterized by its small size and high transmission rates. A LAN typically covers the area of a company or institution, from a few hundred meters to a kilometer. Data rates range from tens of megabits per second to gigabits per second in recent proposals. The implementation of a local area network makes it possible to offer users IT services such as data storage, document printing and, more recently, videoconferencing.

Local area networks are characterized by low installation costs. The cost of cabling plays a significant role in network installation. The type of cabling used has evolved towards a single medium using unshielded twisted pairs. With the explosion of laptops and PDAs, local networks are now incorporating wireless technology. This technology reduces network installation costs and satisfies users' new nomadic needs. Local networks are also easy to set up and configure.

Equipment is identified on a local network by addresses assigned to it at the time of construction. These devices can be inserted or removed, or even be inactive on the network, without disrupting its operation.

Local networks use a shared transmission medium to which all equipment is connected. To ensure fair access to the transmission medium, different access control methods are used. The most common method offers no control at all, and is limited to consequence management. Access methods require a maximum number of devices and a maximum length of transmission medium. In general, this maximum distance does not exceed a hundred meters. Consequently, local networks are made up of several segments, interconnected by equipment such as repeaters, bridges or switches. These devices are used to efficiently extend the range of a local network and interconnect a larger number of devices.

Several LAN standards have been standardized by IEEE and ISO, including the IEEE 802 reference model. The wireless LAN and Ethernet technologies widely deployed in today's networks are based on this reference model.

This article reviews the various technologies available, and describes in detail those most commonly used, such as Ethernet and wireless LANs. Both technologies use the most common transmission media in local networks.

This article traces the evolution of local network technologies to deliver higher data rates and subsequently more advanced services. Finally, it describes the various techniques available for interconnecting local networks.