Basic of Computer Networks

Information and communication are two of the most important strategic issues for the success of every enterprise.

While today nearly every organization uses a number of computers and communication tools (like telephone or fax), they are often still isolated. While managers today are able to use applications like word processors or spreadsheets, not very many of them use computer-based tools to communicate with other departments or information retrieval programs.

To overcome these obstacles in an effective usage of information technology, computer networks are necessary. They are a new kind of organization of computer systems produced by the need to merge computers and communications. Computer networks can manage to put down the barriers between information held on several systems. Only with the help of computer networks can a borderless communication and information environment be built.

Importance of Networking

Computer networks allow the user to access remote programs and remote databases either of the same organization or from other enterprises or public sources. Computer networks provide communication possibilities faster than other facilities. Because of these optimal information and communication possibilities, computer networks may increase the organizational learning rate

there are other reasons why any organization should have a computer network

cost reduction by sharing hardware and software resources
high reliability by having multiple sources of supply
cost reduction by downsizing to microcomputer-based networks instead of using mainframes
greater flexibility because of possibility to connect devices from various vendors

A network is two or more computers connected together to share information and files between them. Businesses aren't the only ones that can benefit from creating a network. Home users can enjoy sharing music, movies and printers from any computer.

File Sharing : Computers connected to a network can share files and documents with each other. Personal computers connected to a business network can choose which files and folders are available to share on the network.

Printers : Computers can print pages to another computer with a printer on the network. Additionally, printers can be connected using a print server, which allows direct printing from all computers.

Types of Networks

A) Local Area Networks (LAN)

B) Metropolitan Area Network (MAN)

C) Wide area network (WAN)

Network Components

1) Hub

A hub works in the physical layer of the OSI model. It is basically a non-intelligent device, and has no decision making capability. What a Hub basically does is take the input data from one of the ports and broadcast the information to all the other ports connected to the network.

To demonstrate its working, consider a 4 port network as shown in Fig 1. There are 4 computers connected to the 4 ports. Suppose, if Computer A wants to send some data to Computer B using a Hub, then, Computer A broadcasts the data on the network, and Computer B, being connected to the network, has access to the data. But, in this case all the other ports connected to the network has access to the data that is being transmitted by Computer A. This happens because, the Hub works in the Physical Layer and hence it does not know about the MAC addresses of the ports connected to the network. So, there is a lack of security in the Hub.

2) Switch

A switch is an intelligent device that works in the data link layer. The term intelligent refers to the decision making capacity of the Switch. Since it works in the Data link layer, it has knowledge of the MAC addresses of the ports in the network.

3)Bridge

A bridge is also a device which works in the Data Link Layer, but is more primitive when compared to a switch. Initial bridges were used to connect only 2 LAN’s, but the most recent ones perform similar operation as the switches. It also works on the principle of transfer of information using the MAC addresses of the ports.

4)Router

Any computer can be connected to the internet via MODEM, which performs the MODulation and the DEModulation operations. But, when there are more than one computer at home or in an organization, and you have a single internet connection, you need a Router. Router is a device which is used when multiple devices need to connect to the Internet using the same IP.

5)Gateway

The Gateway devices work in the Transport layer and above, where the different network technologies are implemented. A gateway is necessary when there are different technologies implemented by the different LAN’s which are to be connected together.

6)Modems

Modem is a device which converts the computer-generated digital signals of a computer into analog signals to enable their travelling via phone lines. The ‘modulator-demodulator’ or modem can be used as a dial up for LAN or to connect to an ISP. Modems can be both external, as in the device which connects to the USB or the serial port of a computer, or proprietary devices for handheld gadgets and other devices, as well as internal; in the form of add-in expansion cards for computers and PCMCIA cards for laptops.