Paul Mockapetris is the computer scientist who designed the Domain Name System, the naming layer that the entire internet still depends on. He did the work in 1983 while at the University of Southern California’s Information Sciences Institute (USC/ISI), one of the institutions at the heart of early ARPANET research. The Internet Hall of Fame, which inducted him, records plainly that “Paul Mockapetris expanded the Internet beyond its academic origins by inventing the Domain Name System (DNS) in 1983.”
The problem he set out to solve was concrete. The early ARPANET stored every name-to-address mapping in a single file, HOSTS.TXT, maintained centrally and copied to every host. As the network grew, that arrangement strained under the load of updates and distribution. Mockapetris proposed replacing it with, in the Hall of Fame’s words, “a distributed and dynamic naming system, essentially the DNS of today” — a hierarchical namespace whose branches could be delegated to the organizations that owned them, so that no single file or party had to hold everything.
His authorship is recorded directly in the primary record. RFC 882, “Domain Names: Concepts and Facilities,” and its companion RFC 883 appeared in November 1983 under his name, introducing “a tree structured name space” and the machinery of name servers and resolvers. Four years later he produced the definitive revision: RFC 1034 and RFC 1035, both dated November 1987 and both authored by P. Mockapetris. Those two documents remain the foundation of DNS to this day.
The design choices Mockapetris baked in have aged unusually well. Hierarchical delegation, caching governed by time-to-live values, and a simple query/response message format allowed DNS to scale from a few hundred ARPANET hosts to billions of internet-connected devices without a structural rewrite. For this work he received the SIGCOMM Award and induction into the Internet Hall of Fame, and DNS is routinely cited as one of the inventions that made the internet usable for ordinary people rather than only for those who could memorize numeric addresses.