11-26-2019, 08:15 AM
geographically distributed computers were established in the mid-1960s (Davies and Barber, 1973; Marrill and Roberts, 1966). The ARPANET, which was to become the largest operational network in the world and to remain so for many years, was started as a four-node system by the Advanced Research Projects Agency of the U.S. Department of Defense in 1969 (Heart, 1975; Heart et al., 1978). According to Pool (1993), its successor, the Internet, connected about 1.7 million host computers and between 5 million and 15 million users as of 1993, and the numbers have been doubling annually.