The Internet is a network of computers that offer access and information to people. To use the internet, you run many different programs depending on the type of information you wish to view.
For example, you might use one program for mail, another program for retrieving files and et a third for playing fantasy games with many people at once. The kind of information freely available includes government documents, scientific data, hobbyist lists, business and personal advertising, databases and much more. Even though the Internet is nebulous and difficult to define, its value is easy to see. If you have regular access to it, you can communicate with anyone else on the Internet quickly and easily. Almost anything you can do through the regular mail system or on the telephone can also be done on the Internet.
The Internet is open to anyone who can use a computer and a modem and can call into a computer that is on the Internet. At many universities and companies, the entire network at the location is connected to the Internet. Most people. however, access the Internet from their own computers through modems.
In the mid-1960s, computer networking was in its infancy. The most common from of communication between the two computers was manual. More advanced computer communication networks had been developed, but they were crude in comparison to today's computers. A network of three ore more computers could be wired together and could communicate at low speeds. but a constant problem with early communication was that each computer had to be functioning for the network to function. Thus, if one computer was turned off for maintenance, the network would not function unless the computer was removed from the network. This made networking unreliable and difficult to manage.
The U.S. Department of Defense was an early supported of much of the research into advanced computers and networking. A network that could be shut down by a single computer's malfunction was major vulnerability, so the military wanted to developed a network that could survive even if one or many of the computers on the network didn't.
Around 1970, the Advanced Research Projects Agency, part of the Department of Defense, set up the first parts of what would become the Internet. There were many goals for this network, dubbed the ARPAnet, all of which were implemented and are still a part of today's Internet. Some of those goals included the following.
The network would be available even if many of the computers of the connections between them failed.
To accommodate the many different types of computers coming onto the market, the Defence Department wanted dissimilar computers to be able to exchange information smoothly. Thus, the networking method had to be unstable by computers with vastly different hardware configuration.
The network would be capable of automatically rerouting information around non-functioning parts of the network. To compare this with a road trip, imaging you are driving from New Delhi to Mumbai. If your planned route through Jaipur was blocked by an accident, you could take the highway through Agra instead. if both the route were not available, you could take a third route via Kanpur. The network had to be capable of this ort of automatic rerouting.
The ARPAnet was to be a network, not just a network of computers. Only one computer on a network had to be connected directly to the APRnet hardware. Every other computer on that local network would appear to be 'on' the APR net and could communicate with other computers on the APRAnet through the one connection.
The APRAnet expanded to non-military uses in the 1970s, when universities and companies doing defense-related research were allowed to use the network. This increased use allowed the researchers, who maintained to APRAnet, to study how growth in the number of computers and users changed the way the ARPAnet responded.
In the late 1970s, the ARPAnet was so large that the original standard would not support the rate of growth of the network. After years of resaech and a fair amount of arguing, the ARPAnet switched from a technology known as Package Switch Nodes to the TCP/IP is a communication protocol that defines how to send particular kind of messages between different computers. The biggest advantage of TCP/IP was that it allowed for almost ultimate growth in the size of the network and was easily implemented on a variety of computer hardware.
Creating a network of networks was a radical idea at the start. However, the Internet was so successful that the concept of internet working, instead of having a single monolithic network has become standard throughout the computer industry. It is useful to know a little about the structure of the Internet and how the individual user relates to it in order to see why it is amenable to rapid growth. Any computer that uses the TCP/IP networking protocol and is physically connected to another computer on the Internet is itself on the Internet. If the computer is on an 'Island' (either unconnected to any computer or only connected to computer that are not connected outside the local network), it is not on the Internet.
For many years, the NSFnet was called the backbone of Internet. The backbone was a series of cable and connecting hardware that passed data at very high speed. Recently, the NSF stopped running the backbone and so many networks now have high speed connection that consented to the remnants of the NSFnet that it is possible to specify what is the Internet backbone and what isn't. However the concept of the backbone still exists. Basically, the backbone is the central set of high speed links. This set of links is growing rapidly and its hardware and harder to determine what is 'central' on the backbone.
Anything connected to the backbone, directly or indirectly can be considered part of the Internet. As long as a single computer in one country is connected to another computer connected to the backbone, that country has access. The more connections there are, the more likely it is that all users in that country can access the Internet more often. This is how the Internet has reached over 100 counties.