A Lan or Local area network is a
computer network that spans a relatively small area.
Most LANs are confined to a single building or group of
buildings. However, one LAN can be connected to other
LANs over any distance via telephone lines and radio
waves. A system of LANs connected in this way is called
a wide-area network (WAN).
Most LANs connect workstations and personal computers.
Each node (individual computer ) in a LAN has its own
CPU with which it executes programs, but it also is able
to access data and devices anywhere on the LAN. This
means that many users can share expensive devices, such
as laser printers, as well as data. Users can also use
the LAN to communicate with each other, by sending
e-mail or engaging in chat sessions.
There are many different types of LANs Ethernets being
the most common for PCs. Most Apple Macintosh networks
are based on Apple's AppleTalk network system, which is
built into Macintosh computers.
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The following characteristics differentiate one LAN from
another:
Topology :
The geometric arrangement of devices on the network. For
example, devices can be arranged in a ring or in a
straight line.
Protocols :
The rules and encoding specifications for sending data.
The protocols also determine whether the network uses a
peer-to-peer or client/server architecture.
Media :
Devices can be connected by twisted-pair wire, coaxial
cables, or fibre optic cables. Some networks do without
connecting media altogether, communicating instead via
radio waves.
LANs are capable of transmitting data at very fast
rates, much faster than data can be transmitted over a
telephone line; but the distances are limited, and there
is also a limit on the number of computers that can be
attached to a single LAN.