No doubt you've heard of a computer network, a group of computers that are wired together so that they can communicate with one another. When computers are hooked together in a network, users of those computers can send each other messages and share computer files and programs.
Computer networks today can be as small as two PCs hooked together in an office. They can be as big as thousands of computers of all different types spread all over the world and connected to one another not just by wires, but through telephone lines and even through the air via satellite.
To build a really big network, you build lots of little networks and then hook the networks to each other, creating an internetwork. That's all the Internet really is: the world's largest internetwork (hence its name ). In homes , businesses, schools , and government offices all over the world, millions of computers of all different types ”PCs, Macintoshes, big corporate mainframes, and others ”are connected together in networks, and those networks are connected to one another to form the Internet. Because everything's connected, any computer on the Internet can communicate with any other computer on the Internet (see Figure 1.1).
Figure 1.1. The Internet is a global internetwork, a huge collection of computers and networks interconnected so they can exchange information.
A Little History Lesson
The successful launch of Sputnik by the Soviets in 1957 might have triggered the space race, but it also helped bring about the Internet (although somewhat indirectly). In part because of Sputnik, the Advanced Research Projects Agency (ARPA) was formed as part of the U.S. Department of Defense, also in 1957.
Among other things, ARPA created research centers at a number of universities across the country. It soon became clear that these research centers needed to be able to communicate with each other through some type of infrastructure. The first four sites to be connected were at the University of California-Los Angeles (UCLA), the Stanford Research Institute, the University of California-Santa Barbara (UCSB), and the University of Utah.
Because this first network was military-oriented, the distribution of information through it was highly secretive. A system of splitting data into tiny "packets" that took different routes to the same destination was developed to make it more difficult to "eavesdrop" on these transmissions. It is this method of "packet switching" that allows the Internet to function as it does today: Large numbers of computers can go down, and data can still be transferred.
By 1969, new research into networking was being conducted . Standard systems of networking were needed in order for computers to be able to communicate with each other. Over time, a system known as TCP/IP was developed; it became the standard protocol for internetworking in 1982.
Because all these internetworks communicated in the same way, they could communicate with one another, too. The government, defense contractors, and scientists often needed to communicate with one another and share information, so they hooked all of their computers and networks into one big TCP/IP internetwork. And that fat internetwork was the infant Internet.
What It Became
The first great thing about the Internet's design is that it's open to all types of computers. Virtually any computer ”from a palmtop PC to a supercomputer ”can be equipped with TCP/IP so it can get on the Net. And even when a computer doesn't use TCP/IP, it can access information on the Net using other technologies, "back doors" to the Net, so to speak.
The other important thing about the Net is that it allows the use of a wide range of communications media ”ways computers can communicate. The "wires" that interconnect the millions of computers on the Internet include the wires that hook together the small networks in offices, private data lines, local telephone lines, national telephone networks (which carry signals via wire, microwave, and satellite), and international telephone carriers .
It is this wide range of hardware and communications options, and the universal availability of TCP/IP, that has enabled the Internet to grow so large so quickly. That's also why you can get online from your home or office, right through the same telephone line you use to call out for pizza. Heck, you can even get online from the neighborhood park using wireless technology. It's a crazy world.