Leonard Kleinrock is an American engineer and computer scientist. A computer science professor at UCLA's Henry Samueli School of Engineering and Applied Science, he made several important contributions to the field of computer networking, in particular to the theoretical side of computer networking. He also played an important role in the development of the ARPANET, the precursor to the Internet, at UCLA. His most well-known and significant work is his early work on queueing theory, which has applications in many fields, among them as a key mathematical background to packet switching, one of the basic technologies behind the Internet. His initial contribution to this field was his doctoral thesis at the Massachusetts Institute of Technology in 1962, published in book form in 1964; he later published several of the standard works on the subject. He described this work as: "Basically, what I did for my PhD research in 1961?1962 was to establish a mathematical theory of packet networks..." His theoretical work on hierarchical routing, done in the late 1970s with his then-student Farouk Kamoun, is now critical to the operation of today's worldwide Internet. 

June 13th, 1934 in New York City (Age 90)