Definition of ARPANET in Network Encyclopedia.

What is ARPANET?

ARPANET is an acronym for Advanced Research Projects Agency Network, a U.S. Department of Defense project begun in 1969 that was designed to provide high-speed network communication links between supercomputers located at different sites around the country.

Arpanet - Interface Message Processor
Arpanet – Interface Message Processor

ARPANET was a test-bed for the development of the TCP/IP protocol suite. The first node on the ARPANET was established in 1969 at UCLA, with other nodes at Stanford and ICSB soon following. The first Request for Comments (RFC) was proposed in the same year by Steve Croker and was entitled «Host Software».

By 1971, ARPANET had grown to over 20 hosts, including MIT, NASA, and the RAND Corporation. The first international nodes were established two years later in Norway and England. In 1983 MILNET was split off from ARPANET, and TCP/IP officially became the standard protocol for ARPANET, at which time ARPANET started to become widely known as the Internet. ARPANET continued to evolve until NSFNET was established in 1986. ARPANET formally died in 1989.

ARPANET logical Map, March 1977
ARPANET logical Map

Because ARPA’s name was changed to Defense Advanced Research Projects Agency (DARPA) in 1971, ARPANET is sometimes referred to as DARPANET. (DARPA was changed back to ARPA in 1993 and back to DARPA again in 1996.) The history of ARPANET and developments leading up to today’s Internet can be found in Where Wizards Stay Up Late, by Katie Hafner and Matthew Lyon.

The History of ARPANET and the INTERNET: Timeline

ARPANET completed its transition to TCP/IP on January 2, 1983, was later replaced by NSFNET in 1990, and then decommissioned on February 28, 1990.