Leonard Kleinrock

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Leonard Kleinrock
Leonard Kleinrock - Internet Hall of Fame inductees 2012 (cropped).jpg
Leonard Kleinrock at a meeting of the members of the Internet Hall of Fame
Born (1934-06-13) June 13, 1934 (age 88)
NationalityUnited States
Alma materCity College of New York, MIT
Known forQueuing theory, ARPANET, Internet development
Scientific career
Doctoral advisorEdward Arthurs[2]
Doctoral studentsChris Ferguson

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 science, in particular to the theoretical foundations of data communication in computer networking.

He played an influential role in the development of the ARPANET and supervised many graduate students who worked on the communication protocols for internetworking which led to the Internet.[3]

Education and career[edit]

Kleinrock was born in New York City on June 13, 1934, to a Jewish family,[4] 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.[5]


Queueing theory[edit]

Kleinrock's best-known and most-significant work is on queueing theory, a branch of operations research that has applications in many fields. His thesis proposal in 1961 led to a doctoral thesis at the Massachusetts Institute of Technology in 1962, later published in book form in 1964. In this work, he analyzed queueing delays in Plan 55-A, a message switching system operated by Western Union for processing telegrams.[6] Kleinrock later published several of the standard works on the subject.


Larry Roberts brought Leonard Kleinrock into the ARPANET project informally in May 1967.[7] Roberts learned about packet switching from a paper written by Donald Davies, presented at the October 1967 Symposium on Operating Systems Principles. Roberts subsequently incorporated the concept into the ARPANET design. He formally contracted with Kleinrock in 1969 to measure the performance of packet switching in the ARPANET. Kleinrock's mathematical work in the early 1970s influenced the development of the early ARPANET.[8][9][10][11]

The first message on the ARPANET was sent by a UCLA student programmer, Charley Kline, who was supervised by Kleinrock.[12] At 10:30 p.m, on October 29, 1969 from Boelter Hall 3420, the school's main engineering building,[13] 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 initial four-node network was established.[14][15]


In the mid-1970s, Kleinrock published research on the theory and application of queuing theory to computer networks. He supervised many graduate students who worked on the communication protocols for internetworking which led to the Internet, including Steve Crocker, Vint Cerf and Jon Postel. Collectively, they produced many research papers. Kleinrock proactively sought to disseminate his own and their research to wider audiences for academic and commercial use.[16] His theoretical work on hierarchical routing in the late 1970s 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 to request the return of his electric razor. At the time, use of the ARPANET for personal reasons was unlawful.[17]

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".[18] 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,[19] which helped facilitate development of the Internet as it is known today.[20] Funding from the bill was used in the development of the 1993 web browser Mosaic, at the National Center for Supercomputing Applications (NCSA).[21]

Packet switching 'paternity dispute'[edit]

In 1990, Kleinrock said:[16]

The thing that really drove my own research was the idea of a message switching network, which was a precursor to the packet switching networks. The mathematical tool that had been developed in queueing theory, namely queueing networks, matched perfectly the model of computer networks. Actually, it didn't match perfectly and I had to adjust that model to fit the realities of computer networks. Then I developed some design procedures as well for optimal capacity assignment, routing procedures and topology design.

Beginning in the mid-1990s, Kleinrock sought to be recognized "as the father of modern data networking".[22] In 2004, he described his work as:

Basically, what I did for my PhD research in 1961-1962 was to establish a mathematical theory of packet networks which uncovered the underlying principles that drives today's Internet.

However, Kleinrock's claims that his work in the early 1960s originated the concept of packet switching and that this work was the source of the packet switching concepts used in the ARPANET are disputed by other Internet pioneers,[22][23][24] including Robert Taylor,[25] Paul Baran,[26] and Donald Davies.[27][28] Baran and Davies are recognized by historians and the U.S. National Inventors Hall of Fame for independently inventing the concept of digital packet switching used in modern computer networking including the Internet.[29][30]

Awards and recognition[edit]

2012 Internet Hall of Fame inductees, including Leonard Kleinrock (seated, fifth from the left)

He has received numerous professional awards. In 1980, he was elected a member of the National Academy of Engineering for pioneering contributions to the field and leadership as an educator in computer communications networks.[31] In 2001 he received the Draper Prize "for the development of the Internet".[32] 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."[1]

In 2010 he shared the Dan David Prize.[33] UCLA 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.[13][34]

He was elected as a member into the National Academy of Engineering. In 2012, Kleinrock was inducted into the Internet Hall of Fame by the Internet Society.[35] Leonard Kleinrock was inducted into IEEE-Eta Kappa Nu (IEEE-ΗΚΝ) 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. He was elected to the 2002 class of Fellows of the Institute for Operations Research and the Management Sciences.[36] 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.[37]

See also[edit]



  1. ^ a b "Eight National Medals of Science Awardees Honored at Gala". NSF. 26 September 2008. Retrieved 19 May 2012.
  2. ^ Leonard Kleinrock at the Mathematics Genealogy Project
  3. ^ Rosenbaum, Philip (29 October 2009). "Web pioneer recalls 'birth of the Internet'". CNN. Retrieved October 30, 2009.
  4. ^ "Jews in Computer & Information Science". The Jewish Contribution to World Civilization web site. Retrieved 5 July 2011.
  5. ^ "Leonard Kleinrock's Profile". UCLA. 12 April 2011. Retrieved 24 May 2012.
  6. ^ Kleinrock, Leonard (December 1962). Message Delay in Communication Nets with Storage (PhD thesis) (PDF) (Thesis). Cambridge: Massachusetts Institute of Technology.
  7. ^ "SRI Project 5890-1; Networking (Reports on Meetings). [1967]". web.stanford.edu. Retrieved 2020-02-15. W. Clark's message switching proposal (appended to Taylor's letter of April 24, 1967, to Engelbart )were reviewed.
  8. ^ Abbate 2000, pp. 37–9, 58–9, 71–2, 230
  9. ^ Roberts, L.G. (1978). "The evolution of packet switching". Proceedings of the IEEE. 66 (11): 1307–1313. doi:10.1109/PROC.1978.11141. ISSN 1558-2256. S2CID 26876676.
  10. ^ Gillies, James; Cailliau, Robert (2000). How the Web was Born: The Story of the World Wide Web. Oxford University Press. p. 25. ISBN 978-0192862075.
  11. ^ C. Hempstead; W. Worthington (2005). Encyclopedia of 20th-Century Technology. Routledge. ISBN 9781135455514.
  12. ^ Orr, Tamra B. (2019-07-15). The Information Revolution: Transforming the World Through Technology. Greenhaven Publishing LLC. ISBN 978-1-5345-6786-3.
  13. ^ a b Savio, Jessica (1 April 2011). "Browsing history: A heritage site is being set up in Boelter Hall 3420, the room the first Internet message originated in". UCLA Daily Bruin. UCLA. Archived from the original on 5 January 2012. Retrieved 1 April 2011.
  14. ^ Sutton, Chris. "Internet Began 35 Years Ago at UCLA with First Message Ever Sent Between Two Computers". UCLA. Archived from the original on 8 March 2008. Retrieved 1 April 2011.
  15. ^ Kleinrock tells the story of the first Internet connection (UCLA video)
  16. ^ a b O'Neill, Judy (3 April 1990). "An Interview with Leonard Kleinrock" (PDF). p. 7.
  17. ^ Still, tapping into the ARPANET to fetch a shaver across international lines was a bit like being a stowaway on an aircraft carrier. The ARPANET was an official federal research facility, after all, and not something to be toyed with. Kleinrock had the feeling that the stunt he'd pulled was slightly out of bounds. 'It was a thrill. I felt I was stretching the Net'. – "Where Wizards Stay Up Late: The Origins of the Internet", Chapter 7.
  18. ^ Toward a National Research Network. 1988. p. 39. doi:10.17226/10334. ISBN 978-0-309-58125-7.
  19. ^ "High-Performance Computing Act of 1991". Archived from the original on 19 October 2015. Retrieved 21 March 2011.
  20. ^ "A Bill of Rights for the Internet: What Should it Have Been at the Outset" (PDF). Retrieved 21 March 2011.
  21. ^ Tuutti, Camille (23 September 2011). "R&D in IT essential to help US stay competitive". Federal Computer Week. Retrieved 25 May 2012.
  22. ^ a b Isaacson, Walter (2014). The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution. Simon & Schuster. pp. 244–5. ISBN 9781476708690. This led to an outcry among many of the other Internet pioneers, who publicly attacked Kleinrock and said that his brief mention of breaking messages into smaller pieces did not come close to being a proposal for packet switching
  23. ^ Alex McKenzie (2009), Comments on Dr. Leonard Kleinrock's claim to be "the Father of Modern Data Networking", retrieved April 23, 2015 "... there is nothing in the entire 1964 book that suggests, analyzes, or alludes to the idea of packetization."
  24. ^ Trevor Harris, University of Wales (2009). "Who is the Father of the Internet?". Variety in Mass Communication Research. Dr Willis H. Ware, Senior Computer Scientist and Research at the RAND Corporation, notes that Davies (and others) were troubled by what they regarded as in appropriate claims on the invention of packet switching
  25. ^ Robert Taylor (November 22, 2001), "Birthing the Internet: Letters From the Delivery Room; Disputing a Claim", New York Times, Authors who have interviewed dozens of Arpanet pioneers know very well that the Kleinrock-Roberts claims are not believed.
  26. ^ Katie Hefner (November 8, 2001), "A Paternity Dispute Divides Net Pioneers", New York Times, The Internet is really the work of a thousand people," Mr. Baran said. "And of all the stories about what different people have done, all the pieces fit together. It's just this one little case that seems to be an aberration.
  27. ^ Donald Davies (2001), "A Historical Study of the Beginnings of Packet Switching", Computer Journal, British Computer Society, 44 (3): 152–162, doi:10.1093/comjnl/44.3.152, I can find no evidence that he understood the principles of packet switching.[dead link]
  28. ^ Scantlebury, Roger (25 June 2013). "Internet pioneers airbrushed from history". The Guardian. Retrieved 10 September 2017.
  29. ^ "The real story of how the Internet became so vulnerable". Washington Post. Archived from the original on 2015-05-30. Retrieved 2020-02-18. Historians credit seminal insights to Welsh scientist Donald W. Davies and American engineer Paul Baran
  30. ^ "Inductee Details - Paul Baran". National Inventors Hall of Fame. Archived from the original on 6 September 2017. Retrieved 6 September 2017; "Inductee Details - Donald Watts Davies". National Inventors Hall of Fame. Archived from the original on 6 September 2017. Retrieved 6 September 2017.
  31. ^ "Dr. Leonard Kleinrock". NAE Website. Retrieved 2021-07-01.
  32. ^ "Draper Prize Honors Four 'Fathers of the Internet'". Wall Street Journal. February 12, 2001. Retrieved 5 September 2017.
  33. ^ Wileen Wong Kromhout (March 15, 2010). "UCLA Internet pioneer Leonard Kleinrock looks toward future, helps students do the same". UCLA Engineering. Archived from the original on April 21, 2010. Retrieved March 30, 2011.
  34. ^ McCarty, Meghan (19 July 2011). "Beginning of the Internet commemorated in new UCLA museum". Southern California Public Radio. Retrieved 21 July 2011.
  35. ^ "2012 Inductees". Internet Hall of Fame. Retrieved 24 April 2012.
  36. ^ Fellows: Alphabetical List, Institute for Operations Research and the Management Sciences, archived from the original on 2019-05-10, retrieved 2019-10-09
  37. ^ "Leonard Kleinrock". Premios Fronteras. Retrieved 2022-06-28.


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