Jon Postel, 55, who as manager of the Internet Assigned Numbers Authority (IANA) was a trailblazer on the international information superhighway, died Oct. 16 at a hospital in Santa Monica, Calif., after surgery for a heart ailment. He lived in Los Angeles.

The pioneer who largely created the Internet address system was credited by industry figures as wielding legendary influence over the technical management of the worldwide computer network. He was regarded by leaders in the computer industry, academic research and the government as a key player in the growth and direction of the Internet.

At the time of Dr. Postel's death, the federal government was in the process of all but turning over management of the Internet to a nonprofit organization he had helped found.

Dr. Postel was as highly regarded and influential within the computer and communications industries as he was little known to the general public. The IANA director was said to be an intensely private man who enjoyed wilderness hiking, but he also wielded policing authority over the Internet address system, allowing the Internet to connect computers throughout the world.

Both the Economist and Financial Post magazines have called Dr. Postel a "god" of the Internet. Others did not go quite as far. But in July, he was awarded the prestigious Silver Medal of the International Telecommunications Union -- the United Nations' specialized agency for telecommunications -- for his contributions to the development of the Global Information Infrastructure.

Dr. Postel, who was director of the computer networks division of the University of Southern California's Information Science Institute, became involved in the Internet before the Internet existed.

In 1969, the Defense Department established the Advanced Research Projects Agency Network (ARPANet). The then-obscure organization was established to connect computers at government sites and various research universities for better communication. Dr. Postel assisted in the installation of ARPANet's first communications switch.

After that, Dr. Postel began doing a job he later joked no one else wanted: He began compiling a list of network protocol numbers for the system. He said that the first list was simply kept on scraps of notebook paper and mushroomed from there.

At age 25, he was involved with the Network Management Center, which conducted tests and did analysis of ARPANet. Since then, he had developed such Internet protocols as the Domain Name System, File Transfer, Telnet and the Internet Protocol itself. For the last 25 years, he had served as editor of Request for Comments, a document series that has been called "the working papers of the Internet."

If his career and the growth of what became the Internet seem one unstoppable success story, it would not be entirely true. A colleague once recalled that Dr. Postel was summoned at great haste to an Air Force base for emergency work on its aging communications system. There was a seemingly inexplicable delay in his arriving at the communications center. It turned out he had been denied admission to the base because he was not wearing shoes.

Dr. Postel, a native Californian, was a 1966 graduate of the University of California at Los Angeles, where he also received a master's degree in engineering and a doctorate in computer science.

In recent years, he had been working on advanced research in such areas as multimedia conferencing, very large networks and very high-speed communications. And he seemed most involved with and impassioned by the future of the Internet.

Dr. Postel made headlines earlier this year, and drew heated criticism from some, after redirecting half the Internet's 12 directory-information computers to his own system. Afterward, he told government officials that he was merely running a test.

A researcher at the University of Maryland at College Park, which controls one of those computers, told a Washington Post reporter: "If Jon asks us to point somewhere else, we'll do it. He is the authority here."

Dr. Postel, almost a parody of the bearded and bespectacled scientist, was once described by Industry Standard magazine as looking like Burl Ives posing as a member of ZZ Top.

Survivors include his companion, Susan Gould of Los Angeles; his mother, Lois Postel of Sherman Oaks, Calif.; two brothers; and a sister.