Taylor, who became IPTO director in 1966, worried about the duplication of expensive computing resources at the various sites with ARPA contracts. He proposed a networking experiment in which users at one site accessed computers at another site, and he co-authored, with Licklider, a paper describing both how this might be done and some of the potential consequences (Licklider and Taylor, 1968). Taylor was a psychologist, not a computer scientist, and so he recruited Larry Roberts of MIT's Lincoln Laboratory to move to ARPA and oversee the development of the new network. As a result of these efforts, ARPA became the primary supporter of projects in networking during this period.

In contrast to the NSF, which awarded grants to individual researchers, ARPA issued research contracts. The IPTO program managers, typically recruited from academia for 2-year tours, had considerable latitude in defining projects and identifying academic and industrial groups to carry them out. In many cases, they worked closely with the researchers they sponsored, providing intellectual leadership as well as financial support. A strength of the ARPA style was that it not only produced artifacts that furthered its missions but also built and trained a community of researchers. In addition to holding regular meetings of principal investigators, Taylor started the "ARPA games," meetings that brought together the graduate students involved in programs. This innovation helped build the community that would lead the expansion of the field and growth of the Internet during the 1980s.

During the 1960s, a number of researchers began to investigate the technologies that would form the basis for computer networking. Most of this early networking research concentrated on packet switching, a technique of breaking up a conversation into small, independent units, each of which carries the address of its destination and is routed through the network independently. Specialized computers at the branching points in the network can vary the route taken by packets on a moment-to-moment basis in response to network congestion or link failure.

One of the earliest pioneers of packet switching was Paul Baran of the RAND Corporation, who was interested in methods of organizing networks to withstand nuclear attack. (His research interest is the likely source of a widespread myth concerning the ARPANET's original purpose [Hafner and Lyon, 1996]). Baran proposed a richly interconnected set of network nodes, with no centralized control system—both properties of today's Internet. Similar work was under way in the United Kingdom, where Donald Davies and Roger Scantlebury of the National Physical Laboratory (NPL) coined the term "packet."

Of course, the United States already had an extensive communications network, the public switched telephone network (PSTN), in which digital switches and transmission lines were deployed as early as 1962.



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