Today
discuss local area networks. The local area network (LAN) constitutes a
relatively new arena for data communication. LAN technology. began
to gain attention in the mid-1970s and today it is one of the fastest-growing industries
in data communication. The basic idea of a LAN is to provide easy access to
DTEs within the office. These DTEs are not only a computer but also common
devices found in offices such as printer plotter and electronic files
and databases. Current LAN is used for interconnecting almost any type of
computing device including mainframe, workstation, personal computer, servers, and other peripheral devices. Many LAN is further connected to other LANs or
WANs via bridges and gateways, LAN is configured to provide the channel and
communication protocols between the work stations and commuters.
LAN, generally are privately owned networks
within a single building or campus of up to a few kilometers in size. LAN is mostly used
to increase employees' productivity and efficiency. At least 70% of time of
employee is spent in communicating. The study says that the automation of work
& the communicating concepts has increased the working & decreased the
redundancy. So it supports decision making & increases the output.
LAN consist of basic components :
1. User Station This helps the user to access
the LAN. It runs special network software, most commonly network drivers
for accessing the LAN. E.g. PC
2. LAN protocol stock It is protocol layer. It
is the hardware card inside user station. Contains microprocessor and firmware
which implements the non-physical protocols.
3. Physical Interface Unit This directly
interfaces the user station based LAN hardware to LAN physical medium. It depends
on LAN physical medium. E.g. coaxial cable connector and cable TV taps.
4. Physical medium This is physical path for
signals to travel between stations. Coaxial cable, optical fiber and infrared
light Classification of interconnected processors by scale LAN is available as
either a Broadband or Baseband system.
Broadband :
A
broadband sector is characterized by the use of analog terminology. It uses a
modem to introduce carrier signal into the transmission medium. The carrier signals are then modified (modulated) by a digital signal. Because of analog nature of the network broadband system are often frequency division-
multiplexer (FDM), providing the ability to carry multiple carriers and subchannel on one path. Broadband system is so named because of the analog carrier
signal operator in the high-frequency Radio Range (Typically 10 to 400
meters). Not all analog LAN's operators at this high frequency in which case they are not considered broadband systems. Broadband has an additional cost, each device requires its own modem, transmission is in one way only, two channels
need to be provided, one for each direction. It covers a larger distance compared to baseband.
|
Baseband : |
The
baseband network uses digital terminology. The baseband network does not use
analog carrier or FDM —frequency division multiplexing techniques. The channels
then act as a transport mechanism by which the digital voltage pulses
propagate through the channel. However multiple accesses to a medium can be
provided by the time-division multiplexed (TDM) or protocols. It is a simple and
inexpensive digital technique.
The
baseband LAN is quite prevalent. However, some of the small baseband systems
(lesser than 30 stations) are been replaced with private branch exchanges. Some
layer LAN's more than 100 stations generally used Broadband techniques.
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