COMPUTER NETWORKING:INTERNET, INTRANETS, EXTRANETS

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INTERNET, INTRANETS, EXTRANETS

The Internet is the world’s largest computer network. It is made up of thousands of independently operated (not necessarily local) networks collaborating with each other. This is why it is sometimes called the network of networks. Today it extends to most of the countries in the world and connects dozens of millions of computers, allowing their users to exchange e-mails and data, use online services, communicate, listen to or watch broadcast programs, and so on, in a very fast and cost- effective way. Millions of people are using the Internet today in their daily work and life. It has become part of the basic infrastructure of modern human life.

As was already mentioned above, the predecessor of the Internet was ARPANet, the first wide area packet switched data network. The ARPANET was created within a scientific research project initiated by the U.S. Department of Defense in the late 1960s. Several universities and research institutes participated in the project, including the University of Utah, the University of California at Los Angeles, the University of California at Santa Barbara, and the Stanford Research Institute. The goal of the project was to develop a new kind of network technology that would make it possible to build reliable, effective LANs and WANs by using different kinds of communication channels and connecting different kinds of computers. By 1974, the basics of the new technology had been de- veloped and the research groups led by Vint Cerf and Bob Kahn had published a description of the first version of the TCP / IP (Transmission Control Protocol and Internet Protocol) suite.

The experimental TCP / IP-based ARPANet, which in its early years carried both research and military traffic, was later split into the Internet, for academic purposes, and the MILNet, for military purposes. The Internet grew continuously and exponentially, extending step by step all over the world. Early in the 1990s, the Internet Society (see www.isoc.org) was established, and it has served since then as the driving force in the evolution of the Internet, especially in the technological development and standardization processes.

The invention of the World Wide Web in 1990 has given new impetus to the process of evolution and prompted the commercialization of the Internet. Today the Internet is a general-purpose public network open to anyone who wishes to be connected.

Intranets are usually TCP / IP-based private networks. They may in fact gateway through a TCP / IP node, but this is not common. They operate separately from the worldwide Internet, providing only restricted and controlled accessibility. Although an intranet uses the same technology as the Internet, with the same kinds of services and applications, it principally serves only those users belonging to the organization that owns and operates it. An intranet and its internal services are closed to the rest of the world. Often this separation is accomplished by using network addresses reserved for such purposes, the so-called ten net addresses. These addresses are not routed in the Internet, and a gateway must proxy them with a normal address to the Internet.

Connecting intranets at different geographical locations via the public Internet, results in extranets. If an organization is operating at different locations and wants to interconnect its TCP / IP-based LANs (intranets), it can use the inexpensive public Internet to establish secure channels between these intranets rather than build very expensive, large-scale, wide area private networks. This way, corporate-wide extranets can be formed, allowing internal users to access any part of this closed network as if it were a local area network.

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