The Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked web pages and other documents of the world wide web.
The USSR's launch of Sputnik spurred the United States to create the Advanced Research Projects Agency, known as ARPA, in February 1958 to regain a technological lead.[1][2] ARPA created the Information Processing Technology Office (IPTO) to further the research of the Semi Automatic Ground Environment (SAGE) program, which had networked country-wide radar systems together for the first time. J. C. R. Licklider was selected to head the IPTO, and saw universal networking as a potential unifying human revolution.
Licklider had moved from the Psycho-Acoustic Laboratory at Harvard University to MIT in 1950, after becoming interested in information technology. At MIT, he served on a committee that established Lincoln Laboratory and worked on the SAGE project. In 1957 he became a Vice President at BBN, where he bought the first production PDP-1 computer and conducted the first public demonstration of time-sharing.
At the IPTO, Licklider recruited Lawrence Roberts to head a project to implement a network, and Roberts based the technology on the work of Paul Baran who had written an exhaustive study for the U.S. Air Force that recommended packet switching (as opposed to circuit switching) to make a network highly robust and survivable. After much work, the first node went live at UCLA on October 29, 1969 on what would be called the ARPANET, one of the "eve" networks of today's Internet. Following on from this, the British Post Office, Western Union International and Tymnet collaborated to create the first international packet switched network, referred to as the International Packet Switched Service (IPSS), in 1978. This network grew from Europe and the US to cover Canada, Hong Kong and Australia by 1981.
The first TCP/IP-wide area network was operational by January 1, 1983, when the United States' National Science Foundation (NSF) constructed a university network backbone that would later become the NSFNet.
It was then followed by the opening of the network to commercial interests in 1985. Important, separate networks that offered gateways into, then later merged with, the NSFNet include Usenet, BITNET and the various commercial and educational networks, such as X.25, Compuserve and JANET. Telenet (later called Sprintnet) was a large privately-funded national computer network with free dial-up access in cities throughout the U.S. that had been in operation since the 1970s. This network eventually merged with the others in the 1990s as the TCP/IP protocol became increasingly popular. The ability of TCP/IP to work over these pre-existing communication networks, especially the international X.25 IPSS network, allowed for a great ease of growth. Use of the term "Internet" to describe a single global TCP/IP network originated around this time.
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