ARPANET is short for "Advanced Research Projects Agency Network".
ARPANET is a term which 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 'wide area' computer network was Joseph Licklider. Licklider was the first director of the Information Processing Techniques Office (IPTO) of ARPA in the early 1960's and is often quoted as being the individual who inspired (later) computer scientists (at ARPA) to develop ARPANET. In 1963, J Licklider envisaged a 'Intergalactic (global) Network' which would use a standardised computer language. While Licklider was not involved in creating ARPANET (he had left ARPA), his influence was crucial in persuading Ivan Sutherland and Robert Taylor that 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. In 1966, Sutherland was replaced as the director of the IPTO by Robert 'Bob' Taylor. Robert Taylor had continued to pursue Licklider's idea of a 'wide area' network, and, in 1966, 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 and build ARPA's computer network. The theory underpinning ARPANET - packet switching - was outlined in 1964 by a book 'Communication Nets' authored by Leonard Kleinrock.
In 1967, Larry Roberts wrote a blue-print for ARPANET in a report titled 'Multiple Computer Networks and Intercomputer Communications'; this blue-print would be based upon ideas previously outlined by Leonard Kleinrock. Plans to build ARPANET began in 1967: specifically at the "ARPANET Design Session" in Ann Arbor, Michigan. It was at this meeting that Wesley A. Clark would suggest the concept of Interface Message Processors (IMPs) to Larry Roberts. Barry Wessler assisted Larry Roberts in finalising the specification for the IMPs in August of 1967. 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.
Larry Roberts, in 1968, sent a 'Request For Quotation' for the development of the IMP to over 100 companies. ARPA eventually contracted the work of building the IMP to 'Bolt, Beranek and Newman' (BBN) technologies in 1968. 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, whilst working for BBN, authored 'Host to IMP Spec. 1822' which outlined how to write an interface so that host computers could connect to the 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 team of computer scientists who helped to design and build ARPANET are known as the: Pioneers of the Internet.
The first IMP delivered by Bolt, Beranek and Newman technologies was shipped to UCLA. The team involved in it's installation included: Vint Cerf, Bill Naylor, Jon Postel, Steve Crocker, and Mike Wingfield; individuals who would all play a major role in the ongoing development of the Internet. The first message sent between by an IMP was sent to an SDS Sigma 7 computer; making it the first ARPANET node.
The first test of the ARPANET network was conducted between 2 nodes: one node was located a the University of California, Los Angeles (UCLA), and the second node was located at the Stanford Research Institute (SRI). Leonard Kleinrock and Douglas Engelbart, respectively, installed the IMP 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; the other nodes were located in California. Ivan Sutherland, previously a director at the IPTO of ARPA - a keen supporter for the funding of ARPANET - worked at the computer science department at the University of Utah.
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, ARPANET had been connected to over 25 nodes in the United States of America, and it had been connected to it's first international nodes (in Norway and England). The key individuals who developed ARPANET, such as Bob Taylor, left ARPA in 1973. 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.
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, while the research network was still referred to 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.