Internet, Intranet, Extranet

An intranet is the generic term for a collection of private computer networks within an organisation. An "extranet" is a computer network that allows controlled access from the outside for specific business or educational purposes. Intranets and extranets are communication tools designed to enable easy information sharing within workgroups.

Internets

The internet is the world-wide network of computer accessible to anyone who knows their Internet Protocol (IP) address – the IP address is a unique set of numbers (such as 209.33.27.100) that defines the computer’s location. Most will have accessed a computer using their browser and the domain (such as http://www.domain.com). Before this named computer can be accessed, the name needs to be resolved (translated) into an IP address. To do this your browser (Internet Explorer, Chrome or Firefox) will access a Domain Name Server (DNS) computer to look-up the name and return an IP address – or issue an error mesage to indicate that the name was not found. Once your browser has the IP address it can access the remote computer. The actual server (the computer that serves up the web pages) does not reside behind a firewall – it it did, it would be an Extranet. It may implement security at a directory level so that access is via a username and password, but otherwise all the information is accessible.

Intranets

The term intranet is somewhat misleading conceptually, because it invites a contrast to the term internet. The real contrast is with the World Wide Web – an important distinction, because "Internet" focuses on physical and technical networks, while the Web focuses on the sets of content accessible on that physical and technical infrastructure.
Recognising the efficieny and power of the Internet, many organisations apply Internet and Web technologies to their own internal networks. An intranet (intra means within) is an internal network that uses Internet technologies. Intranets generally make company information accessible to employees and facilitate working in groups.

Simple intranet applications include electronic publishing or organizational material such as telephone directories, event calendars, procedure manuals, employee benefits information and job postings. Additionally, an intranet typically includes a connection to the Internet. More sophisticated uses of intranets include groupware applications such as project management, chat rooms, newsgroups, group scheduling, and video conferencing.

An intranet essentially is a small version of the Internet that exists within an organization. It has a Web server, supports multimedia Web pages coded in HTML, and is accessible via a Web browser such as Internet Explorer, Firefox, Chrome and Safari. Users update information on the intranet by creating and posting a Web page, using a method similar to that used on the Internet.

In its simplest form, an Intranet can be set up on a networked PC without any PC on the network having access via the Intranet network to the Internet. For example, consider an office with a few PCs and a few printers all networked together. The network would not be connected to the outside world. On one of the drives of one of the PCs there would be a directory of web pages that comprise the Intranet. Other PCs on the network could access this Intranet by pointing their browser to this directory. For example "H:\intranet\index.htm" from then onwward they would navigate around the Intranet in the same way as they would get around the Internet.

Extranet

An extranet is a private network that uses Internet technology and the public telecommunication system to securely share part of a business’s information or operations with suppliers, vendors, partners, customers, or other businesses. An extranet can be viewed as a part of a company’s intranet that is extended to users outside the company. It has also been described as a "state of mind" in which the internet is perceived as a way to do business with other companies as well as to sell products to customers.

An extranet requires security and privacy. These can include firewall server management, the inssuance and use of digital certificates or similar means of user authentication, encryption of messages, and the use of virtucal private networks (VPNs) that tunnel through the public network.

Companies can use an extranet to:

  • Exchange large volumes of data using Electronic Data Interchange (EDI)
  • Share product catalogs exclusively with wholesalers or those "in the trade"
  • Collaborate with other companies on joint development efforts
  • Jointly develop and use training programs with other companies
  • Provide or access services provided by one company to a group of other companies, such as an online banking application managed by one company on behalf of affiliated banks.
  • Share news on common interest exclusively with partner companies.

Essentially an extranet is actually an intranet that is partially accessible to authorised outsiders. The actual server (the computer that serves up the web pages) will reside behind a firewall. The firewall helps to control access between the Intranet and Internet permitting access to the Intranet only to people who are suitably authorised. The level of access can be set to different levels for individuals or groups of outside users. The access can be based on a username and password or an IP address (a unique set of numbers such as 209.33.27.100 that defines the computer that the user is on).