INTERNET

The Internet is an international system of interconnected computer networks of government, educational, nonprofit organization, and corporate computers. The computers and networks are connected to each other by high-speed data communications lines, and even dissimilar computers are able to exchange data with each other using a set of data communications protocols called TCP/IP (Transmission Control Protocol/Internet Protocol). TCP/IP supports Simple Mail Transfer Protocol (SMTP) to permit the sending of electronic mail (E-mail) messages, File transfer protocol (FTP) for moving files between computers, and telnet which makes it possible to log in and interact with a remote computer. TCP controls the transmission of data between computers, and IP controls the automatic routing of the data over what might be a chain of computers.

The Internet's structure is based on a predecessor network called ARPAnet, which was established by the U.S. Department of Defense's Advanced Research Project Agency (ARPA) in 1969 as an experiment to determine how to build a network that could withstand partial outages, such as from an enemy attack. Each computer on the network communicates with others as a peer instead of having one or a few central hub computers, which would be too vulnerable. In the late 1980s ARPAnet was replaced by NSFNET, run by the National Science Foundation, which expanded the network, replaced its telephone lines with faster ones, and funded more college and university connections to the network. Thus, educational institutions became the dominant users in the 1980s. Other organizations and corporations joined by linking their computers, local area networks (LANs), and wide area networks (WANs) to the Internet and adopting TCP/IP to connect their computers. As a result, the Internet comprises some networks that are publicly funded and some of which are private and which charge network access fees. Consequently, different users pay different fees, or none at all, for the same services. In the 1990s corporations and consumers became the biggest users of the Internet.