A Concise History of the Internet—I.

In this two-part article, I trace the history of the Internet. The Internet started in 1969 as an experiment by the Advanced Research Projects Agency (ARPA) of the US Department of Defense to use packet switching on leased telephone lines to connect four mainframe computers. Email was invented in 1971 and it became a "killer application" as it promoted easy interaction among its users. By 1972, fifty computers were connected using leased telephone lines to form what was known as the ARPANET which was successfully demonstrated at an international conference — ICCC 72. ARPANET was followed by Packet Radio Network (PRNET), which connected mobile computers, and Satellite Network (SATNET), which connected computers in Europe with those in the US. A protocol named Transmission Control Protocol/ Internet Protocol (TCP/IP) was invented in 1973 to interconnect ARPANET, PRNET, and SATNET. The success of the TCP/IP protocol in connecting disparate networks paved the way for the development of the Internet. [ABSTRACT FROM AUTHOR]