He received a B.E.E. from the City College of New York in 1960, and an M.A. and Ph.D. degrees from Princeton University in 1962 and 1964 respectively. He worked for a while at Bell Laboratories, and as an Assistant Professor of Electrical Engineering at MIT. He took a leave of absence from MIT to join Bolt Beranek and Newman (BBN), where he was responsible for the detailed overall design of the ARPANET, the first packet-switched network.

While working on a satellite packet network project, he came up with the initial ideas for what later became the Transmission Control Protocol (TCP), which was intended as a replacement for an earlier network protocol, NCP, used in the ARPANET. While working on this, he played a major role in forming the basis of open-architecture networking, which would allow computers and networks all over the world to communicate with each other, regardless of what hardware or software the computers on each network used. To reach this goal, TCP was designed to have the following features:

- Small sub-sections of the whole network would be able to talk to each other through a specialized computer that only forwarded packets (first called a gateway, and now called a router).

- No portion of the network would be the single point of failure, or would be able to control the whole network.

- Each piece of information sent through the network would be a given a sequence number, to ensure that they were dealt with in the right order at the destination computer, and to detect the loss of any of them.

- A computer which sent information to another computer would know that it was successfully received when the destination computer sent back a special packet, called an acknowledgement, for that particular piece of information.

- If information sent from one computer to another was lost, the information would be retransmitted, after the loss was detected by a timeout, which would recognize that the expected acknowledgement had not been received.

- Each piece of information sent through the network would be accompanied by a checksum, calculated by the original sender, and checked by the ultimate receiver, to ensure that it was not damaged in any way en route.

Vint Cerf joined him on the project in the spring of 1973, and together they completed an early version of TCP. Later, it was separated into two separate layers, with the more basic functions being moved to the Internet Protocol (IP). The two together are usually referred together as TCP/IP, and are the basis for the modern Internet.

He was awarded the SIGCOMM Award in 1993 for "for visionary technical contributions and leadership in the development of information systems technology", and shared the 2004 Turing Award with Vint Cerf, for "pioneering work on internetworking, including .. the Internet's basic communications protocols .. and for inspired leadership in networking."

He received the Presidential Medal of Freedom on November 9, 2005