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WHAT IS INTERNET AND INTRANET AND EXTRANET

Internet, intranet, and extranet are three terms that describe “Internet-type” applications that are used by an organization.

INTERNET:
If you wish to expose information to everyone in the world, then you would build an Internet type application. An Internet-type application uses Internet protocols such as HTTP, FTP, or SMTP and is available to persons anywhere on the Internet. We use the Internet and web applications as ways to extend who the application can reach. For example, I no longer need to go to the bank to transfer funds. Because the bank has built a web site on the Internet, I can do that from the comfort of my own home.
Figure 1: Internet
INTRANET:
An application is considered to be on the company’s intranet if it is using Internet-type protocols such as HTTP or FTP but the application is available only within the company. The information on a company’s intranet would not be accessible to persons on the Internet because it is not for public use. For example, a few years ago I was sitting with my banking officer going over my account and noticed that the bank had moved all of its customer account information to a web site and that the banking officer was using a web browser to retrieve my account details. Although the application was being used by a web browser, it was still an “internal” application meant only for banking officers.
Figure 2: Intranet
EXTRANET:
From time to time, an application that has been built for the company’s intranet and used by internal employees will need to be extended to select business partners or customers. If you extend your intranet out to select business partners or customers, you have created an extranet. An extranet cannot be used by anyone else external to the company except for those selected individuals. Figure displays the basic configurations of Internet, intranet, and extranet.
Extranet
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