ARPANET is short for "Advanced Research Projects Agency Network".
ARPANET is a term that can be broken down into two segments: ARPA and NET. ARPA stands for the Advanced Research Projects Agency; which is an agency within the United States Department of Defense (Government department). ARPA was later to be renamed DARPA, which stood for: Defense Advanced Research Projects Agency.
ARPANET was one of the first 'wide area' computer networks, and was created to allow US research laboratories and universities to connect and exchange data. ARPANET was one of the first computer networks to feature packet switching. Packet switching would underpin how the Internet works. ARPANET is therefore viewed as a forerunner to the Internet.
In the early 1960's one of the first scientists to formulate the idea of a 'Intergalactic (global) Network' computer network - using a standardised computer language - was Joseph Licklider. Licklider was the first director of ARPA's Information Processing Techniques Office (IPTO) and he is usually referred to as being the individual who inspired (later) computer scientists to develop ARPANET. Additionally, the theory underpinning ARPANET was outlined in a book titled "Communication Nets" - authored by Leonard Kleinrock (1964). Paul Baran and Donald Davies attempted to develop packet switching networks in the 1960's and their work also influenced the scientists of ARPANET. While Licklider was not involved in creating ARPANET (he had left ARPA by that stage), his influence was crucial in persuading Ivan Sutherland and Robert Taylor - his successors - that the development of a 'wide area network' was of great importance.
In 1964, J Licklider was replaced as the director of the Information Processing Techniques Office (IPTO) by Ivan Sutherland. Licklider had previously met Lawrence Roberts, of MIT's Lincoln Lab, at a Homestead Meeting, and had evangelized Roberts about the creation of a global communications network. In early 1965, Ivan Sutherland provided the funding and contracted Lawrence Roberts and Thomas Marill to perform an early experiment in networking: the result proved a success and it connected a TX-2 computer to a Q-32 mainframe computer. The TX-2 computer was located at Roberts MIT Lincoln Lab (east coast of America) and the Q-32 mainframe computer was located at Marill's SDC's Lab (west coast of America).
In 1966, Sutherland was replaced as the director of the IPTO by Robert 'Bob' Taylor. Bob Taylor was impressed by the success of Roberts and Marill's experiment, and created a plan for a 'wide area' network. Bob Taylor received $1,000.000 in funding to build a 'wide area' computer network from Charles Herzfeld (director of ARPA). In 1966, Taylor persuaded - through the intervention of Herzfeld - Lawrence 'Larry' Roberts to leave MIT (Lincoln Laboratory) and build ARPA's computer network. Initially Lawrence Roberts refused the offer: as he was happy working at MIT's Lincoln Lab. Pressure was applied by Herzfeld, as ARPA was providing half of the funding for the Lincoln Lab, and the director of the Lincoln Lab explained to Lawrence Roberts that it may be a good career move to work at ARPA.
In 1967, Lawrence Roberts became the chief scientist of the ARPANET project and is credited as it's architect. Plans to build ARPANET began in 1967, and would be outlined by Roberts at the "ARPANET Design Session" in Ann Arbor, Michigan. Roberts had outlined the idea of a network with central mainframe computer providing the networking function, this proved unpopular. Wes Clark slipped a note to Roberts stating "you've got the network inside out". Clark believed the power of the network should be located at the edges and not the center. Clark explained to Roberts that the networking function should be handled be specialised minicomputers (IMPs). The IMPs would speak a universal computer language - as outlined previously by Licklider - and the computers connected to the IMPs would only need to translate this data. Clark's idea would simplify the network and impressed Roberts, who outlined the concept of the IMPs in a paper titled "Multiple Computer Networks and Intercomputer Communications". Barry Wessler assisted Larry Roberts in finalising the specification for the IMPs and E. B. Shapiro, who worked at the Stanford Research Institute, authored a report titled 'A Study of Computer Network Design Parameters' which aided Wessler and Roberts in defining their specification for the IMP.
By 1968, the plans for ARPANET were well under way, and Lawrence Roberts contracted Leonard Kleinrock at UCLA to undertake measurement calculations for the network. Roberts also sent a 'Request For Quotation' to over 100 companies to build the IMPs for ARPANET. ARPA eventually contracted the work of building the IMP to 'Bolt, Beranek and Newman' (BBN) technologies; Frank Heart's group at BBN would build the IMP. The Interface Message Processor was a micro-computer that functioned as a packet-switching node; the IMP technology was outlined in the first RFC document (RFC 1). Robert Kahn, who was part of Frank Heart's BBN group, authored "Host to IMP Spec. 1822", that outlined how to write an interface so that host computers could connect to an IMP.
The task of writing the host-to-host protocols for ARPANET was conducted by the Network Working Group (NWG) - a forerunner to the Internet Engineering Task Force (IEFT). The NWG was led by Stephen D. Crocker and supervised by Larry Roberts. It was Crocker who invented the Request for Comments (RFC) document system - to better handle the design process of the protocols - and who outlined the original ARPANET protocols in RFC1, RFC2, RFC3 and RFC4. The starting point for an ARPANET protocol was the 1822 protocol; this protocol would eventually be replaced by the Network Control Program (NCP) (designed by the NWG). The process of creating the protocols, was, according to Stephen Crocker, a haphazard process that did not adhere to a 'grand plan'.
The official plan for ARPANET was delivered by Lawrence Roberts to Bob Taylor on the 3rd of June, 1969. The team of computer scientists who helped to design and build ARPANET are amongst the Pioneers of the Internet.
The first IMP delivered by Bolt, Beranek and Newman technologies was shipped to University of California, Los Angeles (UCLA) in August, 1969. The team involved in it's installation included: Vint Cerf, Bill Naylor, Jon Postel, Steve Crocker, and Mike Wingfield; individuals who would play a major role in the ongoing development of the Internet. By September, the first message sent between UCLA's IMP and their mainframe computer (SDS Sigma 7); making it the first ARPANET node. By October, the first test of the ARPANET network between 2 nodes was conducted: the first node was located at UCLA and the second node was located at the Stanford Research Institute (SRI). Leonard Kleinrock and Douglas Engelbart, respectively, led the teams who conducted the test at these academic institutions. The first successful message sent on ARPANET was "login" and it was transmitted by Charles S. Kline at 10:30pm on the 29th of October, 1969.
When ARPANET was eventually launched, it was comprised of four nodes; each node featured an Interface Message Processor (IMP). The four nodes (locations) were:
As a side note: it may seem unusual for one of the nodes to be located in Utah; as the other nodes were located in California. Ivan Sutherland, previously a IPTO director and provided funding for an early Roberts / Marill networking experiment, was working at the University of Utah computer science department and led the team that installed the Utah IMP.
The first test of ARPANET proved a success and the importance of ARPANET led to Lawrence Roberts becoming the new director of the IPTO in 1969; Bob Taylor was sent by ARPA, in 1969, to probe conflicting reports coming from the Vietnam War. Lawrence Roberts was director of the IPTO from 1969-1973, and would investigate ways in which the network could be expanded and what uses it could provide.
The first authority created for ARPANET was the Network Information Center (NIC). The Network Information Center (NIC) was located at Douglas Engelbart's Augmentation Research Center (SRI) laboratory. Each host computer on the ARPANET was assigned a number. The issue with numbers are that they are difficult to memorise. Hostnames were devised to make it easy to memorise the address of host computers connected to ARPANET. The Network Information Center (NIC) was created to manage the process of assigning hostnames. ARPANET nodes could request a hostname from the Network Information Center (NIC). The NIC would manually store all the hostname information in a file named: HOSTS.TXT. Hosts would download this file from SRI and manually install it onto their host computer. Eventually, the Domain Name System (DNS) would be created (1984) to replace this system.
By 1973, Lawrence Roberts had overseen ARPANET being connected to over 25 nodes in the United States of America, and it's connection to it's first international nodes (in Norway and England). In 1973, the Mansfield Amendment directed ARPA to spend less funding on science projects and to focus on projects with a direct military use. While ARPANET would continue to be funded, it's funding was limited, and many of the computer scientists who created it moved to the private sector to develop commercial computer products; Lawrence Roberts was one of these scientits.
In 1975, due in part to the Mansfield Amendment of 1973, and the fact ARPANET was operational - ARPA was a development agenecy - the Defense Communication Agency (DCA) took operational control of ARPANET. The Defense Communication Agency (DCA) split ARPANET into a research and a military network. The military network was named MILNET and the research network was still named as ARPANET. Longterm plans were to phase out the research ARPANET network.
Despite the turbulence surrounding the operational control of ARPANET, the development of computer networking protocols was still being funded by ARPA (renamed DARPA). ARPANET originally used the Network Control Program (NCP). Bob Kahn joined DARPA in 1972, and had an idea for an 'open' network architecture that would solve some drawbacks of the NCP program. In 1973, Bob Kahn invited Vint Cerf to help him develop his idea into a working protocol. Vint Cerf joined DARPA in 1976, and the protocol he co-invented with Bob Kahn was the Transmission Control Program. Eventually this program would evolve to become TCP/IP. TCP/IP replaced NCP on ARPANET on the 1st of January, 1983; a date that is viewed as being the day the Internet was born.
ARPANET was slowly decommisioned from 1985 to 1989: due to the creation of NSFNET and the Federal Internet Exchange (FIX). The FIX allowed federal networks, like MILNET, to connect to the NSFNET backbone.