ARPANET Definition

ARPANET was a pioneering wide area network (WAN) that was created by the U.S. Defense Advanced Research Project Agency (ARPA) in 1969. It was the world's first packet switching network and the precursor to the Internet.

The first message was sent over the ARPANET on October 29, 1969. It was transmitted over leased telephone lines from a computer in the Department of Engineering at the University of California at Los Angeles (UCLA) to a computer at the Stanford Research Institute (SRI) at Stanford University.

The first permanent ARPANET link was established shortly thereafter on November 21 between the UCLA and SRI. By December 5, links had been added to the University of California at Santa Barbara (UCSB) and the University of Utah, thus completing the initial four-host network. The network continued to grow rapidly thereafter, linking many universities and research centers, and serving as a testbed for new networking technologies.

ARPANET was highly successful with regard to all of its major goals, which included: (1) providing reliable communication even in the event of a partial equipment or network failure, (2) being able to connect to different types of computers and operating systems and (3) being a cooperative effort rather than a monopoly controlled by a single corporation.

In order to provide reliable communication in the face of equipment failure, ARPANET was designed so that no one point or link was more critical than any other. This was accompanied by the building of redundant routes and the use of on-the-fly rerouting of data if any part of the network failed.

The goal of being able to link to a wide variety of computers and operating systems was established at a time when universities, government agencies and other organizations were using a wide array of hardware and software. Because of the extremely high costs of hardware at that time, it was not practical for such organizations to buy new hardware for networking use. Along with achieving this goal, ARPANET also demonstrated the ability to connect to other types of computer networks, such as local area networks (LANs), from around the world through the existing public telephone network (POTS).

The goal of not being controlled by a single corporation was formulated in an era when telecommunications in the U.S. and most other countries were dominated by nationwide monopolies. A major reason for it was to promote a cooperative effort among many engineers at many locations who desired to improve the network for the sake of the network rather than leaving development just to a relatively small and less diverse group of engineers who would be more focused on the profits of a single company. Another reason was that it was consistent with the design philosophy of dispersed control and not relying on any critical point, link or other element in order to facilitate network recovery in the event of some disaster.

Despite, or perhaps because of, its great success, ARPANET was dissolved as a single entity in 1989, leaving the public infrastructure, now known as the Internet, and the military system, which was renamed DARPAnet (Defense Advanced Research Projects Agency network).

Created October 11, 2005.
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