ARPANET
The ARPANET (Advanced Research Projects Agency Network) created by ARPA of the United States Department of Defense, was the world's first operating packet switching network, and the predecessor of the global High Speed Internet. The ARPANET was developed by the IPTO under the sponsorship of DARPA, and conceptualized and designed by Lick Licklider, Lawrence Roberts, and others as described herein.
Packet switching, today the dominant basis for both data and voice communication worldwide, was a new and significant concept in data communications. Previously, information communication was supported upon the idea of circuit switching, as in the old typical telephone circuit, where a dedicated circuit is tied down for the length of the call and communication is only achievable with the single party on the other end of the circuit. With packet switching, a system could utilize one communication connection to communicate with more than one machine by breaking apart data into datagraphs, then assemble these as packets. Not just could the link be shared (very much like a single post box can be used to send letters to various destinations), but each packet could be sent independently of other packets. A sort of packet switching configured by Lincoln Laboratory scientist Larry Roberts underlay the design of ARPANET.
A climate of intense research encircled the entire history of the ARPANET. The Advanced Research Projects Agency was conceived with an emphasis towards research, and so was not oriented exclusively to a military product. The establishment of this agency was part of the U.S. response to the then Soviet Union's launch of Sputnik in 1957. ARPA was tasked to explore how to use their investment in computers via Command and Control Research (CCR). Dr. J.C.R. Licklider was selected to lead this effort. Licklider came to ARPA from Bolt, Beranek and Newman, (BBN) in Cambridge, MA in October 1962.
The earliest ideas of a computer network planned to allow for general communication between users of different computers were developed by J.C.R. Licklider of Bolt, Beranek and Newman (BBN) in August 1962, in a series of memos talking about his "Intergalactic Computer Network" concept. These ideas incorporated nearly everything that the Internet is today. In October 1963, Licklider was named head of the Behavioral Sciences and Command and Control programs at ARPA (as it was then named), the United States Department of Defense Advanced Research Projects Agency. He then convinced Ivan Sutherland and Bob Taylor that this was a very monumental concept, although he left ARPA prior to any actual work on his vision was performed.
ARPA and Taylor remained interested in producing a computer communication network, in part to permit ARPA-sponsored researchers in assorted locations to use various computers which ARPA was supplying, and in part to make new software and other issues widely accessible quickly. Taylor had three separate terminals in his office, connected to three different computers which ARPA was funding: one for the SDC Q-32 in Santa Monica, one for Project Genie at the University of California, Berkeley, and one for Multics at MIT. In order to work on one of those projects, he needed to go over to that particular computer.
By mid-1968, a comprehensive design had been prepared, and after approval at ARPA, a Request For Quotation (RFQ) was conveyed to 140 possible bidders. Most considered the proposal as outlandish, and just 12 companies presented bids, of which merely four were looked on in the top rank. By the end of the year, the arena had been narrowed to two, and after negotiations, a final selection was made, and the contract was granted to BBN on 7 April 1969.
BBN's proposal pursued Taylor's plan closely; it called for the network to be made up of small computers known as Interface Message Processors (more generally known as IMPs), what are today called routers. The IMPs at each site executed store-and-forward packet switching routines, and were linked to each other using modems connected to leased lines (initially running at 50 kbit/second). Host computers linked to the IMPs via custom bit-serial interfaces to connect to ARPANET.
BBN initially selected a ruggedized version of Honeywell's DDP-516 computer to make the first-generation IMP. The 516 was originally designed with 24 kB of core memory (expandable) and a 16 channel Direct Multiplex Control (DMC) direct memory access control unit. Custom interfaces were utilized to connect, via the DMC, to each of the hosts and modems. In addition to the lamps on the front panel of the 516 there was also a specific set of 24 indicator lights to display the status of the IMP communication channels. Each IMP could support up to four local hosts and could communicate with up to six remote IMPs across leased lines.
The small team at BBN (at first just seven people), helped substantially by the detail they had gone into to create their answer to the RFQ, quickly developed the first functioning units. The first protocol development lead to DEL (Decode- Encode-Language) and NIL (Network Interchange Language) were written through a series of meetings at this time. These languages were ahead of their time. The primary intent was to form an on-the-fly description that would tell the receiving end how to interpret the information that would be transmitted.
Yet, the first set of meetings were highly conceptual as neither ARPA nor the universities had held any official charter. The lack of a charter permitted the group to think broadly and openly however. BBN did present particulars as to the host-IMP interface specifications from the IMP side. This data supplied the group some distinct starting points to build from. The total system, including both hardware and the world's first packet switching software system, was designed and installed in nine months.
The ARPANET went to task on August 30, 1969, when BBN delivered the first Interface Message Processor (IMP) to Leonard Kleinrock's Network Measurements Center at UCLA. The IMP was made from a Honeywell DDP 516 computer with 12K of memory, configured to handle the ARPANET network interface. In a renowned piece of Internet lore, on the side of the crate, a hardware architect at BBN named Ben Barker had scrawled "Do it to it, Truett", in tribute to the BBN engineer Truett Thach who journeyed with the computer to UCLA on the plane.
The UCLA team responsible for installing the IMP and producing the first ARPANET node included graduate students Vinton Cerf, Steve Crocker, Bill Naylor, Jon Postel, and Mike Wingfield. Wingfield had constructed the hardware interface between the UCLA computer and the IMP, the machines were linked, and within a few days of delivery the IMP was communicating with the local NMC host, an SDS Sigma 7 computer operating the SEX operating system. Messages were successfully exchanged, and the one computer ARPANET was born.
The Culler-Fried Interactive Mathematics centre at the University of California at Santa Barbara was the third site added to the ARPANET, operating on an IBM 360/75 computer employing the OS/MVT operating system. The fourth ARPANET site was brought on in December 1969 at the University of Utah Graphics Department, operating on a DEC PDP-10 computer utilizing the Tenex operating system. These first four sites had been chosen by Roberts to comprise the initial ARPANET because they were already DARPA sites, and he thought they had the technical capability necessary to produce the requisite custom interface to the IMP.
Over the next few years the ARPANET grew rapidly. In July, 1975, DARPA reassigned management and operation of the ARPANET to the Defense Communications Agency, now DISA. The NSFNET then took over direction of the non-military side of the network during its first period of very rapid development, including connection to networks such as the CSNET and EUnet, and the subsequent evolution into the Internet we recognize today.