Editing Paul Baran (section)

==Packet switched network design==
[[File:The idea of the data packet (Baran, 1964)-en.svg|thumb|The "block message" as suggested by Paul Baran in 1964, this is the very first [[data packet]] that was ever proposed.]]
After joining the [[RAND Corporation]] in 1959, Baran took on the task of designing a "survivable" communications system that could maintain communication between end points in the face of damage from [[nuclear weapon]]s during the [[Cold War]].<ref name=bbc>{{cite news | url = https://www.bbc.co.uk/news/technology-12879908 | title = Internet pioneer Paul Baran passes away |date = March 28, 2011 | work = [[BBC News]] | access-date = March 28, 2011}}</ref> Then, most American military communications used [[high-frequency]] connections, which could be put out of action for many hours by a nuclear attack. Baran decided to automate RAND Director [[Franklin R. Collbohm]]'s previous work with emergency communication over conventional AM radio networks and showed that a distributed relay node architecture could be survivable. The [[Rome Air Development Center]] soon showed that the idea was practicable.<ref name=Brand>{{cite magazine |last=Brand|first=Stewart |author-link=Stewart Brand |date=March 2001 |title=Founding Father |magazine=[[Wired (magazine)|Wired]] |volume=9 |issue=3 |location=New York |publisher=[[Condé Nast Digital]] |issn=1059-1028 |oclc=433726773 |access-date=March 27, 2011 |url=https://www.wired.com/wired/archive/9.03/baran.html |quote=Paul Baran conceived the Internet's architecture at the height of the Cold War. Forty years later, he says the Net's biggest threat wasn't the USSR—it was the phone company}} Stewart Brand's interviews Paul Baran about his work at RAND on survivable networks.</ref>

Using the minicomputer technology of the day, Baran and his team developed a simulation suite to test basic connectivity of an array of nodes with varying degrees of linking. That is, a network of n-ary degree of connectivity would have n links per node. The simulation randomly "killed" nodes and subsequently tested the percentage of nodes that remained connected. The result of the simulation revealed that networks in which n ≥ 3 had a significant increase in resilience against even as much as 50% node loss. Baran's insight gained from the simulation was that redundancy was the key.<ref>{{cite web|url=https://www.rand.org/about/history/baran.list.html |title=Paul Baran and the Origins of the Internet |publisher=RAND corporation |access-date= March 29, 2011}}</ref> His first work was published as a RAND report in 1960,<ref>{{cite journal |title= Reliable Digital Communications Systems Using Unreliable Network Repeater Nodes |journal= RAND Corporation Papers, Document P-1995 |year= 1960 |author= Paul Baran |url= https://www.rand.org/pubs/papers/P1995.html |access-date= March 29, 2011}}</ref> with more papers generalizing the techniques in the next two years.<ref>{{cite journal |title= On Distributed Communications Networks |journal= RAND Corporation Papers, Document P-2626 |year= 1962 |author= Paul Baran |url= https://www.rand.org/pubs/papers/P2626.html |access-date= March 29, 2011 }}</ref>

After proving survivability, Baran and his team needed to show proof of concept for that design so that it could be built. That involved high-level schematics detailing the operation, construction, and cost of all the components required to construct a network that leveraged the new insight of redundant links. The result was one of the first store-and-forward data layer switching protocols, a link-state/distance vector routing protocol, and an unproved connection-oriented transport protocol. Explicit detail of the designs can be found in the complete series of reports ''On Distributed Communications'', published by RAND in 1964.<ref>{{cite web |title=On Distributed Communications |author= Paul Baran|year=1964 |publisher=Rand |url=https://www.rand.org/about/history/baran-list.html |archive-url= https://web.archive.org/web/20060615000308/https://www.rand.org/about/history/baran-list.html |archive-date= June 15, 2006 |display-authors=etal}}</ref>

The design flew in the face of telephony design of the time by placing inexpensive and unreliable nodes at the center of the network and more intelligent terminating 'multiplexer' devices at the endpoints. In Baran's words, unlike the telephone company's equipment, his design did not require expensive "gold plated" components to be reliable. The Distributed Network that Baran introduced was intended to route around damage. It provided connection to others through many points, not one centralized connection. Fundamental to the scheme was the division of the information into "blocks" before they were sent out across the network. That enabled the data to travel faster and communications lines to be used more efficiently. Each block was sent separately, traveling different paths and rejoining into a whole when they were received at their destination.

===Selling the idea===
After the publication of ''On Distributed Communications'', he presented the findings of his team to a number of audiences, including AT&T engineers (not to be confused with Bell Labs engineers, who at the time provided Paul Baran with the specifications for the first generation of T1 circuit that he used as the links in his network design proposal). In subsequent interviews, Baran mentioned how the AT&T engineers scoffed at his idea of non-dedicated physical circuits for voice communications, at times claiming that Baran simply did not understand how voice telecommunication worked.<ref>
{{cite news|url=https://www.wired.com/epicenter/2011/03/internet-architect-paul-baran-dies-at-84/|title=Internet Architect Paul Baran Dies at 84 |publisher=Wired |date= March 28, 2011|access-date= March 29, 2011|first=John C|last=Abell}}</ref>

[[Donald Davies]], at the [[National Physical Laboratory (United Kingdom)|National Physical Laboratory]] in the [[United Kingdom]], also thought of the same idea and implemented a trial network.<ref name="NYT-obit" /><ref name="Harvnb|Harris">{{Cite journal |last=Harris |first=Trevor, University of Wales |date=2009 |editor-last=Pasadeos |editor-first=Yorgo |title=Who is the Father of the Internet? The Case for Donald Davies |url=https://www.academia.edu/378261 |url-status=dead |journal=Variety in Mass Communication Research |language=en |publisher=ATINER |pages=123–134 |isbn=978-960-6672-46-0 |archive-url=https://web.archive.org/web/20220502025941/https://www.academia.edu/378261/Who_is_the_Father_of_the_Internet_The_Case_for_Donald_Davies |archive-date=May 2, 2022}}</ref> While Baran used the term "message blocks" for his units of communication, Davies used the term "packets," as it was capable of being translated into languages other than English without compromise.<ref name="Harvnb|Harris"/> He applied the concept to a general-purpose computer network. Davies's key insight came in the realization that computer network traffic was inherently "bursty" with periods of silence, compared with relatively-constant telephone traffic. It was in fact Davies's work on packet switching, not Baran's, that initially caught the attention of the developers of ARPANET at the [[Symposium on Operating Systems Principles]] in October 1967.<ref>{{cite book|last1=Isaacson|first1=Walter|url=https://books.google.com/books?id=4V9koAEACAAJ&pg=PA237|title=The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution|date=2014|publisher=Simon & Schuster|isbn=9781476708690|page=237}}</ref><ref>{{cite magazine |last=Metz |first=Cade |date=3 September 2012 |title=What Do the H-Bomb and the Internet Have in Common? Paul Baran |url=https://www.wired.com/2012/09/what-do-the-h-bomb-and-the-internet-have-in-common-paul-baran/ |magazine=WIRED |quote=He was very conscious of people mistaken belief that the work he did at RAND somehow led to the creation of the ARPAnet. It didn't, and he was very honest about that.}}</ref> Baran was happy to acknowledge that Davies had come up with the same idea as him independently. In an e-mail to Davies, he wrote:

{{Blockquote|You and I share a common view of what packet switching is all about, since you and I independently came up with the same ingredients.<ref name="Harvnb|Harris"/>|author=|title=|source=}}

[[Leonard Kleinrock]], a contemporary working on analyzing message flow using [[queueing theory]], developed a theoretical basis for the operation of [[message switching]] networks in his proposal for a Ph.D. thesis in 1961-2, published as a book in 1964.<ref>{{Citation | last = Kleinrock | first = Leonard | author-link = Leonard Kleinrock | title = Information flow in large communication nets | journal = RLE Quarterly Progress Report | issue =1 | year = 1961 }}</ref> In the early 1970s, he applied this theory to model the performance of packet switching networks. However, the representation of Kleinrock's early work as originating the concept of packet switching is disputed by other [[internet pioneers]],<ref>{{citation |title= Comments on Dr. Leonard Kleinrock's claim to be "the Father of Modern Data Networking" |year= 2009 |author= Alex McKenzie |url= http://alexmckenzie.weebly.com/comments-on-kleinrocks-claims.html |access-date= April 23, 2015}}
"...there is nothing in the entire 1964 book that suggests, analyzes, or alludes to the idea of packetization."</ref><ref>{{cite book|last1=Isaacson|first1=Walter|title=The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution|date=2014|publisher=Simon & Schuster|isbn=9781476708690|page=245|url=https://books.google.com/books?id=4V9koAEACAAJ&pg=PA245|quote=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}}</ref><ref name="Harvnb|Harris"/><ref>{{Cite AV media |url=https://www.inc.com/computerfreaks |title=Computer Freaks |date=June 22, 2023 |last=Haughney Dare-Bryan |first=Christine |type=Podcast |publisher=Inc. Magazine |series=Chapter Two: In the Air}}</ref> including [[Robert Taylor (computer scientist)|Robert Taylor]],<ref>{{cite news|title=Birthing the Internet: Letters From the Delivery Room; Disputing a Claim|url=https://www.nytimes.com/2001/11/22/technology/l-birthing-the-internet-letters-from-the-delivery-room-disputing-a-claim-325210.html|access-date=10 September 2017|work=[[The New York Times]]|date=22 November 2001|quote=Authors who have interviewed dozens of Arpanet pioneers know very well that the Kleinrock-Roberts claims are not believed.}}</ref> Baran<ref>{{citation |title= A Paternity Dispute Divides Net Pioneers |newspaper= New York Times|date= November 8, 2001 |author= Katie Hefner |url=https://www.nytimes.com/2001/11/08/technology/a-paternity-dispute-divides-net-pioneers.html?pagewanted=all|quote="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."}}</ref> and Davies.<ref>{{citation |title= A Historical Study of the Beginnings of Packet Switching |quote="I can find no evidence that he understood the principles of packet switching."|journal= Computer Journal, British Computer Society|year= 2001 |author= Donald Davies |volume=44 |issue=3 |pages=152–162 |doi=10.1093/comjnl/44.3.152 |url=http://comjnl.oxfordjournals.org/content/44/3/152.extract|url-access=subscription }}{{dead link|date=May 2021|bot=medic}}{{cbignore|bot=medic}}
</ref> 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.<ref>{{Cite news|url=http://www.washingtonpost.com/sf/business/2015/05/30/net-of-insecurity-part-1/|title=The real story of how the Internet became so vulnerable|newspaper=Washington Post|language=en-US|access-date=2020-02-18|quote=Historians credit seminal insights to Welsh scientist Donald W. Davies and American engineer Paul Baran}}</ref><ref>{{cite web|url=http://www.invent.org/honor/inductees/inductee-detail/?IID=316|title=Inductee Details - Paul Baran|publisher=National Inventors Hall of Fame|url-status=dead|archive-url=https://web.archive.org/web/20170906091231/http://www.invent.org/honor/inductees/inductee-detail/?IID=316|archive-date=6 September 2017|access-date=6 September 2017|postscript=none}}; {{cite web|url=http://www.invent.org/honor/inductees/inductee-detail/?IID=328|title=Inductee Details - Donald Watts Davies|publisher=National Inventors Hall of Fame|url-status=dead|archive-url=https://web.archive.org/web/20170906091936/http://www.invent.org/honor/inductees/inductee-detail/?IID=328|archive-date=6 September 2017|access-date=6 September 2017}}</ref>

In 1969, when the US [[Advanced Research Projects Agency]] (ARPA) started implementing the idea of an internetworked set of terminals to share computing resources, the reference materials that they considered included Baran and the RAND Corporation's "On Distributed Communications" volumes.<ref name="NYT-obit"/> The resiliency of a packet-switched network that uses [[link-state routing]] protocols, which are used on the [[Internet]], stems in part from the research to develop a network that could survive a nuclear attack.<ref name="NYT-obit" /><ref name="BBC-obit" />