A local area network (LAN) is a computer network that spans a relatively small area. Most often, a LAN is confined to one room, building or group of buildings; however, one LAN is often connected to other LANs over any distance via telephone lines and radio waves. in contrast, a good area network (WAN) not only covers a bigger geographic distance but also generally involves leased telecommunication circuits.
Ethernet and Wi-Fi are the two most common technologies in use for local area networks. Historical network technologies include ARCNET, Token ring, and AppleTalk.
A LAN could also be configured as (1) a bus, the main channel to which nodes or secondary channels are connected in a branching structure, (2) a ring, in which each computer is connected to two neighboring computers to form a closed circuit, or (3) a star, in which each computer is linked directly to a central computer and only indirectly to one another. Each of these has advantages, though the bus configuration has become the foremost common.
A number of experimental and early commercial LAN technologies were developed in the 1970s. Cambridge Ring was developed at Cambridge University starting in 1974. Ethernet was developed at Xerox PARC between 1973 and 1974. ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977. It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.
A system of LANs connected in this way is called a wide-area network (WAN). The difference between a LAN and WAN is that the wide-area network spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs) and are often connected through public networks. Most LANs connect workstations and personal computers.
Every computer or other device on an Ethernet has a unique 48-bit address. Any computer that wants to transmit listens for a carrier signal that indicates that a transmission is underway. If it detects none, it starts transmitting, sending the address of the recipient at the beginning of its transmission. Every system on the network receives each message but ignores those not addressed thereto. While a system is transmitting, it also listens, and if it detects a simultaneous transmission, it stops, waits for a random time, and retries. The random time delay before retrying reduces the probability that they’ll collide again.
In a wireless LAN, users have unrestricted movement within the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation. Most wireless LANs use Wi-Fi as it is built into smartphones, tablet computers, and laptops. Guests are often offered Internet access via a hotspot service.
LANs are capable of transmitting data at in no time rates, much faster than data will be transmitted over a telephone line; but the distances are limited and there’s also a limit on the number of computers that may be attached to one LAN. Simple LANs generally encompass cabling and one or more switches. LANs can maintain connections with other LANs via leased lines, leased services, or across the web using virtual private network technologies. Depending on how the connections are established and secured, and also the distance involved, such linked LANs might also be classified as a metropolitan area network (MAN) or a large area network (WAN).
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