Leonard Kleinrock

Leonard Kleinrock (born June 13, 1934) is an American computer scientist and Internet pioneer.

He is Distinguished Professor Emeritus of Computer Science at UCLA's Henry Samueli School of Engineering and Applied Science.

Leonard Kleinrock was born in New York City on June 13, 1934, to a Jewish family, and graduated from the noted Bronx High School of Science in 1951.

He received a Bachelor of Electrical Engineering degree in 1957 from the City College of New York, and a master's degree and a doctorate (Ph.D.) in electrical engineering and computer science from the Massachusetts Institute of Technology (MIT) in 1959 and 1963 respectively.

In the early 1960s, Kleinrock pioneered the application of queueing theory to model delays in message switching networks in his Ph.D. thesis, published as a book in 1964.

In the late 1960s and 1970s, he played an influential role in the development of the ARPANET.

His thesis proposal in 1961 led to a doctoral thesis at MIT in 1962, later published in book form in 1964.

In this work, he researched the configuration and operation of communication networks, considering design parameters such as "channel capacity, effect of priority discipline, choice of routing procedure, and design of topological structure".

He analyzed delays in Plan 55-A, a message switching system operated by Western Union for processing telegrams.

His thesis went on to apply probability theory to model queuing delays in a generalized communication network.

A contemporary from MIT, Larry Roberts, brought Leonard Kleinrock into the ARPANET project informally in early 1967.

Roberts learned about packet switching from a paper written by Donald Davies, presented at the October 1967 Symposium on Operating Systems Principles, and incorporated the concept into the proposal for the ARPANET.

Kleinrock was awarded a contract in 1968 to establish a Network Measurement Center to measure and model the performance of the network.

His mathematical work influenced the development of the early ARPANET.

In addition, Kleinrock managed the software team at UCLA — including Steve Crocker, Jon Postel, and Vint Cerf — who developed the host-host protocol for the ARPANET, the Network Control Program (NCP).

The first message on the ARPANET was sent by a UCLA undergraduate student, Charley Kline, who was supervised by Kleinrock.

At 10:30 p.m, on October 29, 1969, from Boelter Hall 3420, the school's main engineering building, Kline transmitted from the university's SDS Sigma 7 host computer to the Stanford Research Institute's SDS 940 host computer.

The message text was the word "login"; the "l" and the "o" letters were transmitted, but the system then crashed.

Hence, the literal first message over the ARPANET was "lo".

About an hour later, having recovered from the crash, the SDS Sigma 7 computer effected a full "login".

The first permanent ARPANET link was established on November 21, 1969, between the Interface Message Processor (IMP) at UCLA and the IMP at the Stanford Research Institute.

By December 5, 1969, the initial four-node network was established.

In the 1970s, he applied queueing theory to model and measure the performance of packet switching networks and published several of the standard works on the subject.

He supervised graduate students who worked on the communication protocols for the ARPANET including students whose later work on internetworking and the Internet protocol suite led to the networking technology employed in the Internet.

His theoretical work on hierarchical routing in the late 1970s with student Farouk Kamoun remains critical to the operation of the Internet today.

Kleinrock made several important contributions to the field of computer science, in particular to the theoretical foundations of data communication in computer networking.

He has received numerous prestigious awards.

Kleinrock later published several of the standard works on the subject in the 1970s.

Kleinrock's work published in the mid-1970s on the performance of the ARPANET underpinned the development of the Transmission Control Protocol of the Internet protocol suite.

His analytic work in the 1970s addressed packet switching networks, packet radio networks, local area networks, broadband networks, nomadic computing, peer-to-peer networks, and intelligent software agents.

Kleinrock's theoretical work on hierarchical routing with student Farouk Kamoun remains critical to the operation of the Internet today.

Kleinrock used the ARPANET for instant messaging from the U.S. to Larry Roberts in England in 1973, employing the network for a modern every-day use.

Kleinrock published hundreds of research papers, which ultimately launched a new field of research on the theory and application of queuing theory to computer networks.

In this role, he supervised the research of scores of graduate students.

He disseminated his research and that of his students to wider audiences for academic and commercial use, and organized hundreds of commercial seminars presented by experts and pioneers in the U.S. and internationally.

Many graduate students that Kleinrock supported based their careers on expertise they acquired while working on the ARPANET with him, including several whose later work on internetworking and the Internet protocol suite led to the networking technology employed in the Internet.

In 1988, Kleinrock was the chairman of a group that presented the report Toward a National Research Network to the U.S. Congress, concluding that "There is a clear and urgent need for a national research network".

He then joined the faculty at the University of California at Los Angeles (UCLA), where he remains to the present day; during 1991–1995 he served as the chairman of the Computer Science Department there.

Kleinrock's best-known and most-significant work is on queueing theory, a major topic of applied mathematics that has applications in many fields.

Although the U.S. did not build a nationwide national research and education network, this report influenced Al Gore to pursue the development of the High Performance Computing Act of 1991, which helped facilitate development of the Internet as it is known today.