Local area network (LAN)

Local area network (LAN)

LAN is very small network within a single building or campus of up to few kilometers.


When two or more computers are connected in a small area i.e. within a distance of not more than a few kilometers then such a network is known as local area network. It is made for an organization and most of the times it is within a single building. The data rate in LAN is of the order of Mbps i.e. Megabits per second. A LAN consists of:

·         Computers

·         Graphic, stations

·         User terminal stations or workstations

·         Cables of transmission media

·         Peripherals like printer, scanner etc.

·         Network interface unit

All the LAN components are connected through cables or some transmission media transmission media. A LAN may use one of the various topology, ring topology, bus topology (Dual bus or bus in the repeater) etc. It uses physically transmission medium. The overall purpose of LAN is to provide inter connection in order to find resource sharing and cost reduction.

·         A LAN has following characteristics.

·         It covers an area of less than 5 kilometers.

·         It provides high speed data communication.

·         The physical interconnecting medium is privately owned.

·         The physical inter connecting medium is usually shared by all station or nodes connected to LAN.

·         They have low error rates.

·         They have simple data communication protocols.

·         Usually the implementation is homogeneous i.e. the computers are of same brand or compatibles in the network.

In local area networks the transmission medium is generally twisted pair cable, coaxial cable or fiber optical cable. Choice of transmission medium depends on its bandwidth, connectivity, noise immunity, security and cost.


The hardware required for LAN. Includes NIU i.e. network interface unit. The NUI connects each device in a LAN network to shared transmission device. It contains rules and logics to access the LAN. It is used to implement LAN protocol and for device attachment. Its function depends on type of topology used in LAN.


LAN is mostly characterized by their geographical scope which range from few hundred meters to few hundred meters to few kilometers. Their speed of transmission varies from 1 to 100 mbps.



To operate LAN system LAN operating system required. It has two aspects

·         Server software

·         Workstation software

A LAN operating system provides resources sharing, data security and connection to other network. Various LAN operating systems are ARCnet, Ethernet, Corvus, Omninet, Penet Novel Network.