What Is ARPANET?

Date First Published: 20th March 2022

Article Type: Computer Terms & Definitions

Difficulty: Medium

Difficulty Level: 6/10

Learn more about what ARPANET is in this article.

Short for Advanced Research Projects Agency Network, ARPANET was the first network that was developed by the ARPA, led by the DOD (US Department of Defence) in 1969. At the University of California at Los Angeles, the University of California at Santa Barbara (UCSB) and the University of Utah, it had four nodes. It was created during the Cold War when the US military was interested in creating a network and when universities were interested in developing a network that could tolerate faults over poor connections and a way for sharing data between different users around the world. The image above shows the APRANET logical map.

When ARPANET was developed, a number of standards were in development. The Network Control Program (NCP) would manage host-to-host communication and would support the first protocols, Telnet and FTP. It would communicate using packet-switching technology. The Interface Message Processor was created to enable messages to be passed between hosts. On October 29, 1969, the first message was sent over ARPANET. Charley Kline, a student at the University of California, Los Angeles (UCLA), attempted to log in to the computer at Stanford Research Institute (SRI). He typed the letters L and O successfully, but the computer crashed when he typed the G of the command LOGIN. However, they were able to establish a successful connection on that same day.

On November 21, 1969, the first permanent connection between UCLA and SRI was established. On December 5, 1969, two more colleges became founder members of ARPANET. The University of California, Santa Barbara, and the University of Utah School of Computing were the schools being considered.

In the early 1970s, ARPANET quickly grew. During this time, a lot of universities and government computers joined the network. ARPANET became active in 1975, and it was used to improve communications technologies. Eventually, satellite links were used to connect multiple computers to each other in other countries.

Due to the success of ARPANET, a lot of new packet-based networks were developed and because of the need for standardised equipment in the network, these different networks couldn't connect to each other. As a result, TCP/IP was created as a protocol to allow communication between networks. In 1977, it became active for the first time.

When the National Science Foundation (NSF) established the Computer Science Network (CSNET) in 1981, access to the ARPANET increased. The NSF funded the creation of national supercomputing facilities at various universities in the early 1980s, whilst the NSFNET project in 1986 offered network access and interconnectivity. After securing private sector expansion and future commercialisation of an extended worldwide network known as the internet through collaborations with the telecommunications and computing industries, ARPANET was officially discontinued in 1990.