What is ARPAnet?

ARPAnet is considered the first implementation of what we now know as the Internet. The ARPAnet name comes from the Advanced Research Projects Agency (ARPA), which was created in 1958 by President Dwight D. Eisenhower, to drive research into technology and science that would ensure the U.S. military’s leadership role in science and technology.

One of the chief motivations for ARPA’s creation was the launch of the Soviet satellite, Sputnik. The Sputnik launch caught the U.S. defense and intelligence establishment completely by surprise and kicked off what would become known as the “space race” between the U.S. and USSR. But even though the space exploration element was its most prominent feature, the space race was actually a technology race, and ARPAnet was one of its many products.

ARPA, the agency, was renamed as the Defense Advanced Research Projects Agency (DARPA) in 1972. But less than a year later, the agency’s name was changed back to ARPA. Finally, it was renamed DARPA again in 1996 and has been known as such since then. Throughout its entire history, ARPA/DARPA has been an agency within the U.S. Department of Defense.

DARPA launches ARPAnet

The initial version of ARPAnet officially went into operation in 1969 with four routers that linked network servers located at Stanford University, the University of California Los Angeles (UCLA), the University of California Santa Barbara (UCSB) and the University of Utah. It quickly grew to 40 router locations throughout the U.S. by 1973.

Also in 1973, ARPAnet reached outside the U.S., with a satellite link to Norway and a cable link to London. Until 1983, ARPAnet was still a U.S. military project. It was only in that year that ARPAnet separated its military and civilian networks. DARPA officially decommissioned ARPAnet in 1990.

Purpose and origin of ARPAnet

Contrary to popular belief, ARPAnet was not created to ensure that the U.S. had a communication network that would survive a nuclear attack. That false rumor was purportedly started by a RAND Corporation report. and the researchers who did develop ARPAnet have subsequently confirmed that was not their mission.

ARPAnet was established as a packet switching network using the Transmission Control Protocol and Internet Protocol (TCP/IP) standards. Packet switching broke up messages into smaller, more manageable packets that would then be transmitted over the network. The TCP/IP protocols defined how those packets are organized, labeled and transmitted.

The individual packets for one message could take different routes to get from the sender’s computer to the receiver’s computer. The TCP/IP protocols and packet switching model ensured that a breakdown in one link on the Internet would not permanently stop the message from reaching its target destination. TCP/IP would re-route the packets through other available routers. The receiver will then put together the received packets into the full message, unless an error is detected.  This error-correction and routing feature may be the reason why some believed that ARPAnet was designed to survive a nuclear attack.

The packet switching model was based on the works of Paul Baran, Donald Davies and Lawrence Roberts. Robert Kahn and Vinton Cerf are credited with developing the TCP/IP protocols, as part of their work for ARPAnet.


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