Saturday, November 18, 2006

What is a Local Area Network?


A set of computers and peripherals connected together by a medium is called a network. All these devices on the netwok communicate with each other through a protocol. All these devices on a netwok can be in the same room or scattered through a building or scattered in different buildings or different cities. All these devices can be separated by many miles by the use of dedicated telephone lines or microwave etc.

Peripherals are nothing but Printers,Scanners,Modems,Plotters etc.
Protocol is a predefined set of rules.

Local Area Network:

If the devices on a network are located in a single place such as a building or a group of rooms,they are called a local area network. Usually all these devices on the network are connected by a single type of network cable in Lan's.

LAN Topologies:

The main dominant Lan topologies are Bus,Hub(Star) and ring.

Bus Topology:

Bus network consists of a single linear cable called a Bus(or Backbone). Each device is attached to this backbone through a junction box or transceiver. From each transceiver another short cable runs to the device's netwok adapter. Signal bounce is eliminated by a terminator at each end of the bus. Barrel connectors can be used to lengthen the cable. For regenerating signals Repeaters are used.Each device has a special address. Data is sent to all devices on the backbone. Each device examines every packet and accepts only messages addressed to them.

Main advantage of bus network is that it allows for a high speed bus. But performance degrades when more devices are added to the bus. Bus topology is good for small network. The entire network goes down if the backbone goes down.

Hub Topology:

This network uses a main cable called the backplane. From the backplane set of cables goes to hubs. All devices are connected to the ports of these hubs. We can set up small hub network with standard Ethernet cables. Also we can set up large hub network by using a high speed fibre optic backplane.The hub networks are easy to set up and maintain.

In this network all devices are connected by cable segments to a centralized hub. Signal travels through the hub to all the computers. The network functions normally if a computer goes down. This network requires more cable.

Ring Topology:

All the devices are connected on a single circle of cable. No termination required as in Bus topology. For regenerating signals no repeaters are used. The computers act as repeaters. The Ring networks are easy to set up and maintain.

Note: Articles on Windows NT,Windows 2000 Server,Windows 2003 Server will come soon on my blog under the same NETWORKING section.

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