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Jon Postel

Summary

Jon Postel (1943 to 1998) was an American computer scientist who edited the Request for Comments (RFC) series, the documents that define the internet's protocols, from 1971 until his death, and who ran the Internet Assigned Numbers Authority (IANA) at the University of Southern California's Information Sciences Institute. He edited the core specifications for IP and TCP in 1981 and wrote the email standard SMTP in 1982. He died on October 16, 1998, three days after IANA submitted its proposal for the nonprofit that became ICANN.

Web Building Encyclopedia · People · Last reviewed October 22, 2026 · 11 min read

Who Jon Postel was

Jon Postel was an American computer scientist who spent almost three decades keeping the internet‘s paperwork in order. As the editor of the Request for Comments (RFC) series, he published the documents that define how the network works, and as the head of the Internet Assigned Numbers Authority (IANA), he kept the lists of numbers and names that every computer on it must agree on.1

He was born in 1943 and died in Santa Monica, California, on October 16, 1998, at the age of 55.231 He wrote or edited the specifications for several of the internet’s core protocols, including the Internet Protocol, the Transmission Control Protocol and the Simple Mail Transfer Protocol used for email.456 A protocol is a set of rules that two computers follow so they can understand each other.

UCLA and the ARPANET

Postel went to Van Nuys High School in Los Angeles, the same school as two later internet pioneers, Vint Cerf and Steve Crocker, though they were in different classes.7 He earned a bachelor’s degree from the University of California, Los Angeles (UCLA) in 1966, a master’s in engineering there in 1968 and a doctorate in computer science in 1974.38

As graduate students, Postel and Cerf both worked for Professor Leonard Kleinrock on the ARPANET project.7 ARPANET was the packet-switching network, funded by the US Department of Defense, from which the modern internet grew.1 In 1969 Postel helped install the ARPANET’s first communications switch at UCLA, according to his New York Times obituary.3

His habit of keeping track of shared numbers started early. In RFC 349, dated May 30, 1972, he wrote that standard protocols needed agreed socket numbers (the numbered doors through which programs on a host talk to the network) and proposed “a czar (me ?) who hands out official socket numbers.”9 The title “Czar of Socket Numbers” first appeared in RFC 433 in December 1972.10

Postel then worked at SRI, a research institute in California, during the 1970s. Elizabeth Feinler, a colleague there, recalled that he had the office next to hers, became the Network Information Center’s contact in the Network Working Group and left SRI in 1976 to join the University of Southern California’s Information Sciences Institute (ISI) in Marina del Rey.11 Danny Cohen, a colleague, dates their work together at ISI from 1977.12 Postel stayed at ISI for the rest of his life and became director of its computer networks division.82

Editing the RFCs

Steve Crocker started the RFC series at UCLA in 1969. When Crocker left for ARPA in June 1971, Postel took over looking after the RFCs, Crocker later wrote, and became the first RFC Editor.10 Over time he went from handing out numbers to exercising editorial judgment over what was published, and he defined many of the series’ early procedures.10 The title “RFC Editor” was formalized in RFC 902 in July 1984.10

In the 1999 retrospective RFC 2555, Robert Braden wrote that Postel had collected, archived and edited the series for 28 years, and that it then held more than 2,500 documents. Feinler called him “Mister RFC.”11 A 1988 list of official standards from the Internet Activities Board gives Postel as the RFC Editor and says submissions went to him by email.13 He was a founding member of the Internet Architecture Board and served on it continuously until his death.7

He did not do the work alone. He recruited Joyce K. Reynolds from ISI, and she and Bob Braden kept the RFC Editor running after he died.10 ISI hosted the RFC Editor until a transition that began in October 2009. In 2010 the production and publishing contracts went to Association Management Solutions (AMS).10

The protocols he wrote

Postel helped shape the split between the two protocols that carry internet traffic. In IEN 2, a note dated August 15, 1977, he wrote that the designers were breaking the principle of layering by using TCP for two jobs at once, and argued that TCP should be used strictly as an end-to-end protocol between hosts, with addressing and routing handled by a separate internet protocol.14

That separation is how the standards came out. As editor at ISI, prepared for the Defense Advanced Research Projects Agency (DARPA), he produced:

  • Internet Protocol (IP). RFC 760 in January 1980, then RFC 791 in September 1981.154 As of October 2026, RFC 791 is still the Internet Standard STD 5 and has not been obsoleted; it defines version 4 of IP, whose numeric addresses are explained in the IP address entry.164
  • Transmission Control Protocol (TCP). RFC 761 in January 1980, then RFC 793 in September 1981.175 TCP makes sure data arrives complete and in order. RFC 793 stood for four decades until RFC 9293, an IETF standard, replaced it in 2022.18
  • User Datagram Protocol (UDP). RFC 768, dated August 28, 1980, a way to send single messages with a minimum of protocol machinery. It does not guarantee delivery, and points applications that need ordered, reliable delivery to TCP.19
  • Simple Mail Transfer Protocol (SMTP). RFC 821, August 1982, credited on its title page to Jonathan B. Postel. Its stated objective is to transfer mail reliably and efficiently.6
  • File Transfer Protocol (FTP). RFC 959, October 1985, written with Joyce Reynolds.20

The web’s own protocol, HTTP, runs on top of this stack.

The robustness principle

Postel’s best-known sentence appears in section 2.10 of the January 1980 TCP specification, under the heading “Robustness Principle”: “be conservative in what you do, be liberal in what you accept from others.”17 The same sentence is in RFC 793.5 The IP specifications state the idea as a rule for implementations: be conservative in sending and liberal in receiving.154

The 1989 host requirements standard, RFC 1122, restated it with the order reversed, liberal in accepting and conservative in sending, and added that software should be written to deal with every conceivable error.21 The rule is often called Postel’s law.22 Sources differ on its first appearance: Eric Allman, writing in ACM Queue in 2011, said Postel formulated it in 1981, while RFC 9413 traces its earliest form in the RFC series to RFC 760 of 1980.2223

The principle has been questioned in later years. Allman argued that accepting sloppy input can contribute to security problems on a hostile internet.22 RFC 9413, published by the Internet Architecture Board in June 2023, says the principle has been interpreted in many ways, some of which harm interoperability over time, and recommends active protocol maintenance instead.23

IANA, the DNS and .us

Cerf wrote that Postel volunteered to be the “Numbers Czar” and later became the IANA once the internet was in place.7 The Internet Hall of Fame credits him with creating IANA, a job he first did by hand.1 By December 1988, the Internet Activities Board’s list of official standards said its protocol standards were managed for the board by the Internet Assigned Numbers Authority.13

IANA was less an organization than a role. The US government’s June 1998 White Paper said IANA, headed by Postel, coordinated the system but was not formally organized: “It describes a function more than an entity.” It added that Postel had begun maintaining the lists of host names and addresses as a graduate student at UCLA.24 The Assigned Numbers document of October 1994, RFC 1700 by Reynolds and Postel, called IANA the central coordinator for assigning unique values used by internet protocols, and gave its address as [email protected].25 In January 2002, RFC 3232 recorded that, since 1994, the Assigned Numbers RFCs had been replaced by an online database, now at iana.org.26

Postel was also central to the Domain Name System, the internet’s directory that turns names into addresses. The DNS entry covers how he asked his ISI colleague Paul Mockapetris to design it. ICANN’s Root Server System Advisory Committee (RSSAC) records that Postel set out the timeline for the move to DNS in RFC 881, and that he and Mockapetris set up the first root server at ISI in 1984.27 In October 1984, RFC 920 by Postel and Reynolds named the first top-level domains: GOV, EDU, COM, MIL, ORG and a temporary ARPA domain, plus two-letter country codes.28

Through the 1990s, Postel chose which organizations would run root servers. The RSSAC history says he picked them for technical expertise, internet connectivity and diversity, approved new servers and their renaming under root-servers.net, and asked Network Solutions to set up extra servers that would later move to other operators.27 In March 1994, his RFC 1591 set out how top-level domains were delegated. It made IANA responsible for the overall coordination and management of the DNS, and described the people running a top-level domain as trustees with a duty to serve the community.29

Postel also looked after the United States’ own country code domain, .us. RFC 1480 of June 1993, by Ann Westine Cooper and Postel, which replaced their RFC 1386 of December 1992, names the two of them as its administrators at ISI.30 Their plan organized .us by political geography, with names in the form entity.locality.state-code.US.2930 Cerf described him as the custodian of the .US domain.7 The National Telecommunications and Information Administration’s (NTIA’s) list of .us contracts begins in 2001, with NeuStar.31 On October 1, 2026, NTIA announced Identity Digital as the new administrator of .us, under a contract dated September 30, 2026.3231 As of October 22, 2026, IANA’s root zone database still listed Registry Services, LLC as the manager of .us, in a record last updated on August 5, 2026.33

Postel had other roles outside ISI. He was a founder of Los Nettos, a regional network for the Los Angeles area, one of the founders of the Internet Society and its first individual member, and a trustee of the society from 1993 to 1998.17 In 1998 he received the silver medal of the International Telecommunication Union.87

The 1998 root zone test and ICANN

By 1998, the US government was planning how to move control of names and addresses out of government contracts. Network Solutions (NSI) ran the main “A” root server, from which the other root servers copied the root zone, the master list of top-level domains.2734 The NTIA issued its proposal for reorganizing the system, later called the Green Paper, on January 30, 1998.24

In January 1998, Postel asked Jim Koda and Paul Vixie to set up a test primary root server at ISI, named DNSROOT.IANA.ORG. Once it was verified, he told several root server operators to copy the root zone from it instead of from NSI’s A root. A few days later he ended the test and asked all operators to switch back, according to the RSSAC history.27

Accounts differ on the details:

  • Scope. A 2012 account published by the Internet Hall of Fame says Postel emailed eight of the 12 organizations running root servers, and that they made the switch.35 The RSSAC history says only that several operators did.27
  • Dates. Tech Monitor reported on February 9, 1998, that Postel said the test ran from January 23 to February 4.34 A 2016 history by the registrar Gandi dates his email to the operators to January 28, 1998.36
  • Purpose. Tech Monitor quoted Postel as saying the test showed the secondary root servers could be reconfigured. It also reported that he ran it without the knowledge of NSI or the government, which funded IANA, and that some people saw it as an attempt to hijack the internet.34 The 2012 account says some called it a test and others a statement to the White House about who should control the root.35 The New York Times obituary said Postel described it as an experiment to show the network’s backup capability, and that it caused no disruption.3
  • Why it ended. The RSSAC history says only that Postel concluded the test and asked operators to switch back.27 A later, unconfirmed account comes from a July 2025 post to the Internet Society’s internet-history mailing list, in which John Gilmore wrote that Postel reversed the change after a phone call “on 1998-01-30 or so” from Ira Magaziner, whom President Clinton had asked to look into the dispute.37 Gilmore does not say he was on the call or how he learned of it, and none of the other sources cited here mention it.

Later that year, Postel worked on the private body the government had asked for. On October 13, 1998, IANA submitted its proposal to the NTIA, with draft articles and bylaws for the Internet Corporation for Assigned Names and Numbers (ICANN), a new nonprofit public-benefit corporation that the announcement described as formally incorporated in California. The announcement said Postel had directed IANA since its start and was recovering from surgery.38 In 1999, USC transferred responsibilities, including the L root server, to ICANN.27

Death and legacy

Postel died on Friday, October 16, 1998, at St. John’s Hospital in Santa Monica, of complications after heart surgery, according to The New York Times, ISI and the RSSAC history.38227 The RFC series’ own 2019 timeline, RFC 8700, gives the date as October 15.10 After his death, the RSSAC history notes, there was no one to drive the assignment of the last two root servers, and the root server operators began meeting as a formal group.27

Vint Cerf’s tribute, RFC 2468, is titled “I Remember IANA.” It is dated October 1998 and says: “For nearly 30 years, Jon has served us all.”7 Danny Cohen’s eulogy, delivered at UCLA on October 30, 1998, and published as RFC 2441, calls him the internet’s corporate memory and says he was, in effect, IANA itself.12 ISI later set up the Postel Center for Experimental Networking in his name.2

In RFC 2468, Cerf pledged to create an award in Postel’s name for long service to the internet community, with Postel as its first recipient.7 The Internet Society’s Jonathan B. Postel Service Award was established in 1999, and Cerf presented the first one, to Postel posthumously, at INET’99.3940 It recognizes outstanding and sustained contributions in service to the internet community.39 Recipients include Joyce Reynolds and Bob Braden (2006), Elizabeth Feinler (2013), Steve Crocker and Xing Li (2024) and David Clark (2025); no award was made for 2021 or 2023.40 As of October 2026, the Internet Society lists a US$20,000 honorarium and an engraved crystal globe, and its timeline lists the 2026 presentation for November 18, 2026, during the IETF 127 meeting.40

The Internet Hall of Fame inducted Postel in 2012.1

Timeline

  1. David Clark receives the Postel Service Award40
  2. Steve Crocker and Xing Li named recipients of the 25th Postel Service Award39
  3. Postel is inducted into the Internet Hall of Fame1
  4. First Jonathan B. Postel Service Award is presented to Postel posthumously40
  5. Postel dies in Santa Monica after heart surgery, aged 553
  6. IANA submits its proposal for ICANN to the NTIA38
  7. Postel runs a test that has root servers copy the root zone from ISI27
  8. RFC 1591 sets out how top-level domains are delegated29
  9. RFC 1480 names Postel and Ann Westine Cooper as administrators of .us30
  10. RFC 920 by Postel and Reynolds lists the first top-level domains28
  11. RFC 821 defines the Simple Mail Transfer Protocol6
  12. RFC 791 (IP) and RFC 793 (TCP) are published with Postel as editor4
  13. RFC 761 states the robustness principle17
  14. Postel leaves SRI to join USC's Information Sciences Institute11
  15. Postel takes over the RFC series from Steve Crocker10

What it means for your website

Postel’s work is not something you install, but you use it every time someone visits your site or emails you. A few practical points follow from it.

  • Your domain sits in a system he set up. RFC 1591 describes whoever runs a top-level domain, such as .com or .us, as a trustee with a duty to serve the community.29 Before you buy a domain name, it is worth knowing who runs the extension. Our guide to domain extensions covers the common ones.
  • The .us domain has a government contract behind it. NTIA supervises .us and awards the contract to run it. On October 1, 2026, it named Identity Digital as the new administrator, under a contract dated September 30, 2026.3231 As of October 22, 2026, IANA’s database still listed Registry Services, LLC as the .us manager.33 If you own a .us name, watch for notices from your registrar about the handover.
  • Your email still runs on SMTP. Mail sent from your domain is carried by the protocol Postel specified in RFC 821. As of October 2026, the current version is RFC 5321 of October 2008, updated by RFC 7504.41 Our page on websites and email explains the records that help that mail get delivered.
  • Do not count on the other side forgiving mistakes. RFC 9413 warns that tolerating faulty input lets errors pile up until they become part of how things work.23 For a site owner, the safe reading is to send correct output: valid HTML, properly formed DNS records and correctly set up email, rather than relying on browsers and mail servers to work around errors.
  • The numbers your host mentions come from IANA. Port numbers, DNS record types and many other protocol values are listed in the online registries that replaced the printed Assigned Numbers lists, as RFC 3232 records.26

See also

References

  1. Jon Postel. Internet Hall of Fame, Internet Society. 2012. accessed October 22, 2026.
  2. ISI Pioneer's Internet Legacy Celebrated in Computerworld. USC Information Sciences Institute. 2007-07-10. accessed October 22, 2026.
  3. Jonathan Postel Is Dead at 55; Helped Start and Run Internet. Katie Hafner, The New York Times, as forwarded to the linux-kernel mailing list. 1998-10-18. accessed October 22, 2026.
  4. RFC 791: Internet Protocol. Jon Postel (ed.), USC Information Sciences Institute, for DARPA, RFC Editor. 1981-09. accessed October 22, 2026.
  5. RFC 793: Transmission Control Protocol. Jon Postel (ed.), USC Information Sciences Institute, for DARPA, RFC Editor. 1981-09. accessed October 22, 2026.
  6. RFC 821: Simple Mail Transfer Protocol. Jonathan B. Postel, USC Information Sciences Institute, RFC Editor. 1982-08. accessed October 22, 2026.
  7. RFC 2468: I Remember IANA. Vint Cerf, RFC Editor. 1998-10. accessed October 22, 2026.
  8. Dr. Jonathan B. Postel (press release on his death). USC Information Sciences Institute, postel.org. 1998-10-20. accessed October 22, 2026.
  9. RFC 349: Proposed Standard Socket Numbers. Jon Postel, RFC Editor. 1972-05-30. accessed October 22, 2026.
  10. RFC 8700: Fifty Years of RFCs. H. Flanagan (ed.), Internet Architecture Board, RFC Editor. 2019-12. accessed October 22, 2026.
  11. RFC 2555: 30 Years of RFCs. RFC Editor et al.. 1999-04-07. accessed October 22, 2026.
  12. RFC 2441: Working with Jon, Tribute delivered at UCLA, October 30, 1998. D. Cohen, RFC Editor. 1998-11. accessed October 22, 2026.
  13. RFC 1083: IAB Official Protocol Standards. Internet Activities Board, RFC Editor. 1988-12. accessed October 22, 2026.
  14. IEN 2: Comments on Internet Protocol and TCP. Jon Postel, Internet Experiment Note, RFC Editor history archive. 1977-08-15. accessed October 22, 2026.
  15. RFC 760: DoD Standard Internet Protocol. Jon Postel (ed.), USC Information Sciences Institute, RFC Editor. 1980-01. accessed October 22, 2026.
  16. Information on RFC 791 (STD 5). RFC Editor. accessed October 22, 2026.
  17. RFC 761: DoD Standard Transmission Control Protocol. Jon Postel (ed.), USC Information Sciences Institute, RFC Editor. 1980-01. accessed October 22, 2026.
  18. RFC 9293: Transmission Control Protocol (TCP). W. Eddy (ed.), IETF, RFC Editor. 2022. accessed October 22, 2026.
  19. RFC 768: User Datagram Protocol. J. Postel, USC Information Sciences Institute, RFC Editor. 1980-08-28. accessed October 22, 2026.
  20. RFC 959: File Transfer Protocol (FTP). J. Postel and J. Reynolds, USC Information Sciences Institute, RFC Editor. 1985-10. accessed October 22, 2026.
  21. RFC 1122: Requirements for Internet Hosts, Communication Layers. R. Braden (ed.), RFC Editor. 1989-10. accessed October 22, 2026.
  22. The Robustness Principle Reconsidered. Eric Allman, ACM Queue, vol. 9, no. 6. 2011. accessed October 22, 2026.
  23. RFC 9413: Maintaining Robust Protocols. M. Thomson and D. Schinazi, Internet Architecture Board, RFC Editor. 2023-06. accessed October 22, 2026.
  24. Management of Internet Names and Addresses (statement of policy, the White Paper). National Telecommunications and Information Administration, Federal Register vol. 63, no. 111. 1998-06-10. accessed October 22, 2026.
  25. RFC 1700: Assigned Numbers. J. Reynolds and J. Postel, USC Information Sciences Institute, RFC Editor. 1994-10. accessed October 22, 2026.
  26. RFC 3232: Assigned Numbers: RFC 1700 is Replaced by an On-line Database. J. Reynolds (ed.), RFC Editor. 2002-01. accessed October 22, 2026.
  27. RSSAC023v2: History of the Root Server System. ICANN Root Server System Advisory Committee. 2020-06-17. accessed October 22, 2026.
  28. RFC 920: Domain Requirements. J. Postel and J. Reynolds, USC Information Sciences Institute, RFC Editor. 1984-10. accessed October 22, 2026.
  29. RFC 1591: Domain Name System Structure and Delegation. Jon Postel, USC Information Sciences Institute, RFC Editor. 1994-03. accessed October 22, 2026.
  30. RFC 1480: The US Domain. A. Cooper and J. Postel, USC Information Sciences Institute, RFC Editor. 1993-06. accessed October 22, 2026.
  31. .us Domain Space. National Telecommunications and Information Administration. accessed October 22, 2026.
  32. NTIA Announces Identity Digital as New Administrator of .us Top Level Domain. National Telecommunications and Information Administration. 2026-10-01. accessed October 22, 2026.
  33. Delegation Record for .US. Internet Assigned Numbers Authority (IANA). 2026-08-05. accessed October 22, 2026.
  34. Postel's DNS Root Re-direction Test Now Complete. Tech Monitor (Computergram). 1998-02-09. accessed October 22, 2026.
  35. Remembering Jon Postel, and the Day He Redirected the Internet. Cade Metz, Internet Hall of Fame. 2012-10-15. accessed October 22, 2026.
  36. Tech Fundamentals: IANA. Gandi. 2016-03-10. accessed October 22, 2026.
  37. [ih] Jon Postel's papers. John Gilmore, Internet-history mailing list, Internet Society. 2025-07-18. accessed October 22, 2026.
  38. Internet Address Arbiter: Proposed Transfer of Function to Private Sector. ICANN announcements archive. 1998-10-13. accessed October 22, 2026.
  39. Internet Society Announces Recipients of 25th Annual Jonathan B. Postel Award. Internet Society. 2024-11-07. accessed October 22, 2026.
  40. Jonathan B. Postel Service Award. Internet Society. accessed October 22, 2026.
  41. Information on RFC 5321: Simple Mail Transfer Protocol. J. Klensin, RFC Editor. 2008-10. accessed October 22, 2026.

Web Building Encyclopedia. First published October 22, 2026. Last reviewed October 22, 2026. Every fact on this page is linked to a source we opened. Spotted an error? Write to [email protected].