In the 1970s, ISI joined universities and the federal government to help create what has become the defining technology of our age: the Internet. The Defense Department tool was known as the Advanced Research Projects Agency network, or ARPAnet.

ISI played several key roles in the Net’s evolution. Under DARPA contracts, ISI researchers helped refine Transmission Control Protocol and Internet Protocol into TCP/IP, now the dominant communications paradigm for carrying Net information.

An ISI researcher, Jonathan Postel, developed and maintained the “Requests for Comments” that provided crucial communication among Net architects from 1969 to his death in 1998. Postel also managed the Internet Assigned Numbers Authority (IANA), which oversaw global address allocation during the Net’s early years. (As traffic exploded, responsibility was shifted to the US Department of Commerce. The role now is held by the Internet Corporation for Assigned Names and Numbers, or ICANN, which operates the IANA.)

ISI colleague Paul Mockapetris meanwhile created the Domain Name System (DNS), which has remained the standard through the Net’s explosive growth. Postel also managed other vital Internet functions, including the "Request for Comments" written documentation that both catalyzed and captured the emerging Internet's technical structure and operations - a novel use of the Net in its own evolution. In recognition, Mockapetris and fellow Net pioneer Danny Cohen were elected into the prestigious U.S. National Academy of Engineering in 2006, largely for their work at ISI.