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An intranet is an internal network that implements Internet and Web technologies such as Web servers and Web browsers that use HTTP and HTML. An extranet is an intranet that has been extended outside the company to a business partner, with transmissions going over the Internet or across private lines. An intranet has the following characteristics:

• Intranets run the TCP/IP protocol and other Internet-related protocols.


• Web servers are used to publish information and provide access to back-end systems.


• Web browsers provide a universal client interface.


• Internet mail generally becomes the pervasive mail system.

Another significant characteristic of intranets is that they typically use private IP addressing rather than IP addresses that are assigned by Internet authorities. RFC 1918 (Address Allocation for Private Internets, February 1996) describes private IP network addressing schemes.