The Goliath of all computer networks, the Internet links hundreds of millions of computer users throughout the world. Strictly speaking, the Internet is a network of networks.
It consists of tens of thousands of separate computer networks, all interlinked, so that a user on any of those networks can reach out and potentially touch a user on any of the other networks. This network of networks connects more than half a billion computers to each other. (That’s right, billion with a b.)
One of the official documents (RFC 2026) of the Internet Engineering Task Force (IETF) defines the Internet as “a loosely organized international collaboration of autonomous, interconnected networks.” Broken down piece by piece, this definition encompasses several key aspects of what the Internet is:
Loosely organized: No single organization has authority over the Internet. As a result, the Internet is not highly organized. Online services, such as America Online or MSN, are owned and operated by individual companies that control exactly what content appears on the service and what software can be used with the service.
No one exercises that kind of control over the Internet. As a result, you can find just about any kind of material imaginable on the Internet. No one guarantees the accuracy of information that you find on the Internet, so you have to be careful as you work your way through the labyrinth.
International: Nearly 200 countries are represented on the Internet, from Afghanistan to Zimbabwe.
Collaboration: The Internet exists only because many different organizations cooperate to provide the services and support needed to sustain it. For example, much of the software that drives the Internet is open-source software that’s developed collaboratively by programmers throughout the world, who constantly work to improve the code.
Autonomous: The Internet community respects that organizations that join the Internet are free to make their own decisions about how they configure and operate their networks. Although legal issues sometimes boil up, for the most part, each player on the Internet operates independently.
Interconnected: The whole key to the Internet is the concept of interconnection, which uses standard protocols that enable networks to communicate with each other. Without the interconnection provided by the TCP/IP protocol, the Internet would not exist.
Networks: The Internet would be completely unmanageable if it consisted of half a billion individual users, all interconnected. That’s why the Internet is often described as a network of networks.
Most individual users on the Internet don’t access the Internet directly. Instead, they access the Internet indirectly through another network, which may be a LAN in a business or academic environment, or a dialup or broadband network provided by an Internet service provider (ISP). In each case, however, the users of the local network access the Internet via a gateway IP router.
The Internet is composed of several distinct types of networks: Government agencies, such as the Library of Congress and the White House; military sites (did you ever see War Games or any of the Terminator movies?); educational institutions, such as universities and colleges (and their libraries); businesses, such as Microsoft and IBM; ISPs, which allow individuals to access the Internet; and commercial online services, such as America Online and MSN.
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Source:http://www.dummies.com/how-to/content/network-administration-internet-basics.html
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