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Leonard Kleinrock

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Nationality  United States
Known for  Internet development
Institutions  UCLA
Name  Leonard Kleinrock

Doctoral advisor  Edward Arthurs
Role  Computer scientist
Doctoral students  Chris Ferguson
Books  Queueing systems
Leonard Kleinrock Take Two Internet pioneer Leonard Kleinrock on the 39dark

Born  June 13, 1934 (age 81) New York City (1934-06-13)
Alma mater  City College of New York, MIT
Residence  Los Angeles, California, United States
Education  Massachusetts Institute of Technology (1963)
Awards  Charles Stark Draper Prize, Marconi Prize
Fields  Engineering, Computer Science
Similar People  Lawrence Roberts, Paul Baran, Robert E Kahn, Donald Davies, Vint Cerf

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Leonard Kleinrock (born June 13, 1934) is an American computer scientist. A 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 foundations of computer networking. He played an influential role in the development of the ARPANET, the precursor to the Internet, at UCLA.


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Ucla s leonard kleinrock displays internet s first router

Education and career

Leonard Kleinrock Leonard Kleinrock Big Think

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 in 1959 and 1963 respectively. 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.

Packet switching

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Kleinrock's best-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 of 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:

Leonard Kleinrock History of Computers and Computing Internet Birth Leonard Kleinrock

"Basically, what I did for my PhD research in 1961–1962 was to establish a mathematical theory of packet networks..."

Leonard Kleinrock UCLAs Leonard Kleinrock displays Internets first router YouTube

In 2001 he received the Draper Prize "for the development of the Internet". However, Kleinrock's contribution to packet switching is disputed by some, including Robert Taylor, Paul Baran and Donald Davies.

Leonard Kleinrock Leonard Kleinrocks Home Page

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


Leonard Kleinrock UCLAs Leonard Kleinrock to receive National Medal of Science UCLA

The first message on the ARPANET was sent by UCLA student programmer Charley Kline, at 10:30 p.m, on October 29, 1969 from Boelter Hall 3420, the school's main engineering building. Supervised by Kleinrock, 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 IMP at UCLA and the IMP at the Stanford Research Institute. By December 5, 1969, the entire four-node network was established.

In 1988, Kleinrock was the chairman of a group that presented the report Toward a National Research Network to the U.S. Congress. This report was highly influential and was used to develop the High Performance Computing Act of 1991, that was influential in the development of the Internet as it is known today. Funding from the bill was used in the development of the 1993 web browser Mosaic, at the National Center for Supercomputing Applications (NCSA).

Room 3420 at Boelter Hall was restored to its condition of 1969 and converted into the Kleinrock Internet Heritage Site and Archive. It opened to the public with a grand opening attended by Internet pioneers on October 29, 2011. Kleinrock claims to have committed the first illegal act on the Internet, having sent a request for return of his electric razor after a meeting in England in 1973. At the time, use of the Internet for personal reasons was unlawful.


He has received numerous professional awards. Kleinrock was selected to receive the prestigious National Medal of Science, the nation's highest scientific honor, from President George W Bush in the White House on September 29, 2008. "The 2007 National Medal of Science to Leonard Kleinrock for his fundamental contributions to the mathematical theory of modern data networks, and for the functional specification of packet switching, which is the foundation of Internet technology. His mentoring of generations of students has led to the commercialization of technologies that have transformed the world." In 2010 he shared the Dan David Prize. In 2012, Kleinrock was inducted into the Internet Hall of Fame by the Internet Society. Leonard Kleinrock was inducted into IEEE-Eta Kappa Nu (IEEE-HKN) in 2011 as an Eminent Member. The designation of Eminent Member is the organization's highest membership grade and is conferred upon those select few whose outstanding technical attainments and contributions through leadership in the fields of electrical and computer engineering have significantly benefited society. In September 2014, Leonard Kleinrock was awarded the ACM SIGMOBILE Outstanding Contribution Award at MobiCom 2014.

Leonard Kleinrock has been granted with the 2014 BBVA Foundation Frontiers of Knowledge Award “for his seminal contributions to the theory and practical development of the Internet,” in the words of the jury’s citation.


  • Kleinrock, Leonard (May 1961). "Information Flow in Large Communication Nets". Ph.D. Thesis Proposal. Massachusetts Institute of Technology. 
  • Kleinrock, Leonard (July 1961). "Information Flow in Large Communication Nets". RLE Quarterly Progress Report. Massachusetts Institute of Technology. 
  • Kleinrock, Leonard (April 1962). "Information Flow in Large Communication Nets". RLE Quarterly Progress Report. Massachusetts Institute of Technology. 
  • Kleinrock, Leonard (December 1962). "Message Delay in Communication Nets with Storage" (PDF). (PhD thesis). Cambridge, MA: Massachusetts Institute of Technology. Archived from the original (PDF) on 2009-03-26. 
  • Kleinrock, Leonard (1964). Communication Nets: Stochastic Message Flow and Design. McGraw-Hill. p. 220. ISBN 978-0486611051. 
  • Kleinrock, Leonard (2 January 1975). Queueing Systems: Volume I – Theory. New York: Wiley Interscience. p. 417. ISBN 978-0471491101. 
  • Kleinrock, Leonard (22 April 1976). Queueing Systems: Volume II – Computer Applications. New York: Wiley Interscience. p. 576. ISBN 978-0471491118. 
  • Kleinrock, Leonard; Kamoun, Farok (January 1977). "Hierarchical Routing for Large Networks, Performance Evaluation and Optimization". Computer Networks. 1 (3): 155–174. 
  • Kleinrock, Leonard; Gail, Richard (12 April 1996). Queueing Systems: Problems and Solutions. Wiley-Interscience. p. 240. ISBN 978-0471555681. 
  • References

    Leonard Kleinrock Wikipedia