Roberts engaged Howard Frank to consult on the topological design of the network.
Frank made recommendations to increase throughput and reduce costs in a scaled-up network.
By March 1970, the ARPANET reached the East Coast of the United States, when an IMP at BBN in Cambridge, Massachusetts was connected to the network.
Thereafter, the ARPANET grew: 9 IMPs by June 1970 and 13 IMPs by December 1970, then 18 by September 1971 (when the network included 23 university and government hosts); 29 IMPs by August 1972, and 40 by September 1973.
By June 1974, there were 46 IMPs, and in July 1975, the network numbered 57 IMPs.
By 1981, the number was 213 host computers, with another host connecting approximately every twenty days.

Larry Roberts saw the ARPANET and NPL projects as complementary and sought in 1970 to connect them via a satellite link.
Peter Kirstein's research group at University College London (UCL) was subsequently chosen in 1971 in place of NPL for the UK connection.
In June 1973, a transatlantic satellite link connected ARPANET to the Norwegian Seismic Array (NORSAR), via the Tanum Earth Station in Sweden, and onward via a terrestrial circuit to a TIP at UCL.
UCL provided a gateway for an interconnection with the NPL network, the first interconnected network, and subsequently the SRCnet, the forerunner of UK's JANET network.
Roberts engaged Howard Frank to consult on the topological design of the network. Frank made recommendations to increase throughput and reduce costs in a scaled-up network. By March 1970, the ARPANET reached the East Coast of the United States, when an IMP at BBN in Cambridge, Massachusetts was connected to the network. Thereafter, the ARPANET grew: 9 IMPs by June 1970 and 13 IMPs by December 1970, then 18 by September 1971 (when the network included 23 university and government hosts); 29 IMPs by August 1972, and 40 by September 1973. By June 1974, there were 46 IMPs, and in July 1975, the network numbered 57 IMPs. By 1981, the number was 213 host computers, with another host connecting approximately every twenty days.
Larry Roberts saw the ARPANET and NPL projects as complementary and sought in 1970 to connect them via a satellite link. Peter Kirstein's research group at University College London (UCL) was subsequently chosen in 1971 in place of NPL for the UK connection. In June 1973, a transatlantic satellite link connected ARPANET to the Norwegian Seismic Array (NORSAR), via the Tanum Earth Station in Sweden, and onward via a terrestrial circuit to a TIP at UCL. UCL provided a gateway for an interconnection with the NPL network, the first interconnected network, and subsequently the SRCnet, the forerunner of UK's JANET network.
ARPANET