Paul Baran, an engineer who helped create the technical underpinnings for the Arpanet, the government-sponsored precursor to today’s Internet, died Saturday night at his home in Palo Alto, Calif. He was 84.

The cause was complications from lung cancer, said his son, David.

In the early 1960s, while working at the RAND Corporation in Santa Monica, Calif., Mr. Baran outlined the fundamentals for packaging data into discrete bundles, which he called “message blocks.” The bundles are then sent on various paths around a network and reassembled at their destination. Such a plan is known as “packet switching.”

Mr. Baran’s idea was to build a distributed communications network, less vulnerable to attack or disruption than conventional networks. In a series of technical papers published in the 1960s he suggested that networks be designed with redundant routes so that if a particular path failed or was destroyed, messages could still be delivered through another.

Mr. Baran’s invention was so far ahead of its time that in the mid-1960s, when he approached AT&T with the idea to build his proposed network, the company insisted it would not work and refused.