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Paul Baran RAND (1960s)

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Paul Baran

The concept of packet switched communications was born in three diverse corners in the 1960s:

The first was Paul Baran, working at RAND for the U.S. Air Force. It was the height of the cold war, tensions were frayed, and the country was creeping towards a nuclear exchange. Baran was concerned that the military postures of the Cold War players was premised on a hair trigger weapons controlled by a flimsy command and control system.  In short, Baran was concerned about whether, in a time of crisis, national leaders could transmit a “Go – No Go” command to the troops.

1948: RAND Corporation established as independent non profit. [RAND]

1955: Baran joins Hughes, works on Minuteman Intercontinental Missile system

1959: Baran joins RAND

In the 1960s , Baran at RAND had been researching survivable networks in the event of a nuclear exchange, and had been consulting with DoD, US Air Force. Baran's analysis indicated that centralized networks had single points of failure that made them vulnerable to attack. The solution, Baran argued, was a distributed network design were traffic could be rerouted among multiple potential redundant routes and the loss of any no single point in the network would not result in a critical failure. Baran's goal was to build a resilient command-and-control network that could deliver a simple "Go / No Go" command to the troops.

"Both the US and USSR were building hair-trigger nuclear ballistic missile systems. If the strategic weapons command and control systems could be more survivable, then the country's retaliatory capability could better allow it to withstand an attack and still function; a more stable position. But this was not a wholly feasible concept, because long-distance communication networks at that time were extremely vulnerable and not able to survive attack. That was the issue. Here a most dangerous situation was created by the lack of a survivable communication system." [Baran in Abbate, 10].

"It was necessary to have a strategic system that could withstand a first attack and then be able to return the favor in kind. The problem was that we didn't have a survivable communications system, and so Soviet missiles aimed at U.S. missiles would take out the entire telephone-communication system. At that time the Strategic Air Command had just two forms of communication. One was the U.S. telephone system, or an overlay of that, and the other was high-frequency or shortwave radio. So that left us with the interesting situation of saying, Well, why do the communications fail when the bombs were aimed, not at the cities, but just at the strategic forces? And the answer was that the collateral damage was sufficient to knock out a telephone system that was highly centralized. Well, then, let's not make it centralized. Let's spread it out so that we can have other paths to get around the damage." [Baran quoted in Vanity Fair] [Paul Baran MP3 at Vanity Fair]

In 1964, Paul Baran published On Distributed Communications, in which he critiqued then existing military communications design as a vulnerable, centralized telecommunications network. Diagrammed as a spoke model with a hub in the middle, an enemy could successfully take out a single point causing the network to fail. Baran advocated that the U.S. Department of Defense redo their entire communications system, moving to a decentralized, packet switched design. In this network, diagramed as a mesh network, there is no central point of control and each node in the network is served by redundant links.  Data, transmitted over shared communications lines, would be in individually addressed packets, where nodes in the network would read the addresses and forward the packets to its destination along the best known available route. This network would have redundancy and ability to route around failure. Baran wrote,

We will soon be living in an era in which we cannot guarantee survivability of any single point. However, we can still design systems in which system destruction requires the enemy to pay the price of destroying n of n stations.  If n is made sufficiently large, it can be shown that highly survivable system structures can be built-even in the thermonuclear era. [Baran 1964 at 16].

A failure in the network is not fatal; the distributed mesh network merely routes the packets around the failure and crucial “Go – No Go” commands could continue to be transmitted. 

In 1965, Baran and RAND formally recommended to the US Air Force that they build a distributed network. AT&T, the communications contractor for DOD, rejected the proposal of packet switched networks, insisting that their networks were reliable. [Brand] AT&T recognized packet switching as a competitive threat to their long distance service, and would have no part setting up their own demise. [Cassidy] In 1966, this recommendation was passed on to the Defense Communications Agency (DCA will take over administrative responsibility for the ARPANET from DARPA in 1975). [Segaller 64] The staff of DCA were circuit-switched trained and thus the recommendation received no traction.

"The DCA was one of many agencies that had been created in an attempt to bring military operations under the central control of the Department of Defense, rather than allowing each of the armed services to build its own systems. In accordance with this centralizing strategy, the DOD administration made it clear during the review process that any new network would be built not by Air Force contractors but by the DCA, which had no expertise in digital technology. Baran and his Air Force sponsors, doubting that the DCA would be able to build the system that Baran had described, reluctantly decided to scrap the proposal rather than risk having it executed badly, which would waste large sums of money and perhaps discredit Baran's ideas." [Abbate p 20]

Those who were concerned about the unreliable nature of military communications were concerned with its unreliable nature on both sides. Baran stated in an interview with Stewart Brand,

We were a hell of a lot better off if the Soviets had a better command and control system. Their command and control system was even worse than ours. [Brand]

Therefore Baran and Rand made the research unclassified, published it, and gave courses on it, permitting the Soviets to benefit from the work as well.

Baran’s recommendation was comprehensive. He wanted to retool the entire DoD communications system, which was run by engineers trained in circuit-switched technology, to a new, untested packet-switched design. It was not a recommendation destined for success. However, Baran’s ideas were picked up by Don Davies in the U.K. and by Robert Taylor and Larry Roberts who incorporated them into the design of the ARPANET.

Destruction of Transcontinental Microwave Towers (Proving Baran's Point)

As it to prove Baran's point concerning the vulnerability of the existing communications network, on May 28, 1961, American radicals blew up AT&T microwave towers in the South West, going over the Rockies, interrupting the central transcontinental microwave routes, severing 2200 circuits. Porticus has great coverage of the incident including many photographs of the damage. [Porticus Long Lines] [Porticus Explosion Damage.]

Influence of Baran on ARPANet Design

Wired: The myth of the ARPANet - which still persists - is that it was developed to withstand nuclear strikes. That's wrong, isn't it?

Paul Baran: Yes. Bob Taylor had a couple of computer terminals speaking to different machines, and his idea was to have some way of having a terminal speak to any of them and have a network. That's really the origin of the ARPANet The method used to connect things together was an open issue for a time [WIRED 2001]

There is a myth that the Internet was designed to survive nuclear war (aka, Paul Baran's work). Essentially every Internet pioneer, including Paul Baran, Larry Roberts, and Vint Cerf are on record that this is inaccurate. While its not true that the Internet was designed to survive nuclear war, it is true that Baran's work influenced the design of the ARPANet and the Internet. [Salus p 6, 10, 24] The Internet Pioneers website relates the story as follows:

when Larry Roberts was beginning work on the ARPANET he heard of Baran's ideas. Roberts was not designing a network for use in wartime, but rather to facilitate communications between ARPA researchers and allow them to use remote computing resources effectively, but Baran's ideas for a robust network were appealing to Roberts. Baran's distributed network and packet-switching schemes were adopted, and Baran became an informal consultant for the ARPANET project. [IP Baran]

Origins of the Myth

The origins of the myth may date back to a Time Magazine article on the ARPANet, but I have not been able to confirm this. Early references in the media include the following: [NPR Newshour Sept. 10, 1998 "...the Internet was built to survive nuclear war. I guess the question tomorrow is can it survive the release of the Starr report?"] [Bruce Sterling, A Short History of the Internet, 1993]

Those of the "Internet Was Designed to Interconnect ARPA Funded Computers, not Survive Nuclear War" Faith

The Internet Society's Brief History of the Internet states

It was from the RAND study that the false rumor started claiming that the ARPANET was somehow related to building a network resistant to nuclear war. This was never true of the ARPANET, only the unrelated RAND study on secure voice considered nuclear war. However, the later work on Internetting did emphasize robustness and survivability, including the capability to withstand losses of large portions of the underlying networks. [ISOC Brief History n 5]

Janet Abbate wrote in her book, "[Donald] Davies was instrumental in passing on the knowledge of packet switching that he and Baran had developed to Lawrence Roberts, who was in charge of creating the ARPANET." [Abbate p 8] See also RAND, Paul Baran and the Origins of the Internet. She wrote:

Paul Baran, too, became directly involved in the early stages of planning the ARPANET. Roger Scantlebury had referred Lawrence Roberts to Baran's earlier work. Soon after returning to Washington from Gatlinburg, Roberts had read Baran's On Distributed Communications. Later he would describe this as a kind of revelation: "Suddenly I learned how to route packets." Some of the ARPANET contractors, including Howard Frank and Leonard Kleinrock, were also aware of Baran's work and had used in in their research. In 1967, Roberts recruited Baran to advise the ARPANET planning group on distributed communications and packets switching. [Abbate p 38]

However, Abbate notes that Roberts did not incorporate a number of Baran's Cold War threat designs as Roberts was not concerned with survivability. [Abbate p 39]

Others believe that Baran's work was separate from ARPA's work. Baran was working with the Air Force; the ARPANet was being developed by ARPA. The different research had different motivations:

It was from the RAND study that the false rumor started claiming that the ARPANET was somehow related to building a network resistant to nuclear war. This was never true of the ARPANET, only the unrelated RAND study on secure voice considered nuclear war. However, the later work on Internetting did emphasize robustness and survivability, including the capability to withstand losses of large portions of the underlying networks. [ISOC n 5]

Larry Roberts stated

"Recently, people have been [] Paul Baran wrote about a secure nuclear defense network, his concept of what the network was, and applying it to the ARPANet. Of course, they had nothing to do with each other. I went to Congress and defended it. And what I told Congress was that this was for the future of science in the world - the civilian world as well as the military - and the military would benefit just as much as the rest of the world. It was worthwhile being done under government and military sponsorship, but it clearly wasnt for military purposes. And I didnt mention nuclear war." "Time said the ARPANet was built to enable Defense Department scientists to connect to one another in the event of a nuclear war. I wrote a letter to Time pointing out they were mistaken, and they wrote a letter back to me assuring me that their sources were correct." [Segaller 70]

"Paul Baran, "On Distributed Communications Networks", IEEE Transactions on Systems. It is from this paper that the rumor was started that the Internet was created by the military to withstand nuclear war. This is totally false. Even though this Rand work was based on this premise, the ARPANET and the Internet stemmed from the MIT work of Licklider, Kleinrock and Roberts, and had no relation to Baran's work." [Roberts, Internet Chronology]

Roberts, Computer Science Museum 1988 ("When I came into contact with Paul's stuff, as I remember it, was at ARPA after I had started the Arpanet, and at that point, when we were studying all of the technology as we had planned the network, his stuff came up. We looked at it and found reading techniques and that sort of stuff, but I don't remember -- in fact, as best I remember it, to this point in time, I've checked -- in fact, I've searched for references in publications of Paul's, and the set of documents which I had at ARPA that were, some classified and so-on that -- after the Air Force were early, but I've never found the published article. So, if there is one, that's great, but I didn't see it.")

Note that in a 1970, Roberts cites to Paul Baran in explaining the design of the ARPANET:

The standard message switched service uses a large central switch with all the nodes connected to the switch via communication lines; this configuration is generally referred to as a Star. Star systems perform satisfactorily for large blocks of traffic (greater than 100 kilobits per message), but the central switch saturates very quickly for small message sizes. This phenomenon adds significant delay to the delivery of the message. Also, a Star design has inherently poor reliability since a single line failure can isolate a node and the failure of the central switch is catastrophic.

An alternative to the Star, suggested by the Rand study "On Distributed Communications"3, is a fully distributed message switched system. Such a system has a switch or store and forward center at every node in the network. Each node has a few transmission lines to other nodes; messages are therefore routed from node to node until reaching their destination. Each transmission line thereby multiplexes messages from a large number of source-destination pairs of nodes. The distributed store and forward system was chosen, after careful study, as the ARPA Network communications system.

[Roberts Wessler 1970 (emphasis added)]

Rhonda Hauben recounts

"Larry Roberts, also a pioneer during these important early days of networking, points out that Baran's work was either classified or otherwise "unfortunately... very sparsely published in the scientific press." Thus according to Roberts, the impact of Baran's work on the actual development of packet switching networks 'was mainly supportative, not sparking its development.'" [Hauben]

From a Vint Cerf Interview

Vint: "So the feasibility of intercomputer exchange in a kind of block like mode was being looked at in 1966. Of course, they were totally oblivious, I think, at the time, to Paul Baran's distributed communications report, which at the time was partly classified. It was done at RAND Corporation in 1964. Actually he did the work in 1962 and the final reports came out in 1964.

Interviewer: "As a graduate student involved in networking, were you aware of Baran's work? Had you looked at that?

Vint: "No, absolutely not... I was unaware at the time of that work. So my involvement in networking was literally a hands-on experience. We didnt know what computer networks were really, except that there was this thing that BBN had invented called an IMP. Somehow or other we were suppose to try to use it to make computers communicate with each other, make processes talk to each other." [Cerf, Oral History 1990]

Frank Heart (BBN):

Some versions of the story indicate that that the RAND researchers and the ARPA leadership met once and that the two lines of research were independent and did not influence each other. [Denning 2]

[Greenstein 23 ("this myth points in misleading directions. Surviving nuclear war was, at most, one of many motivations for the funding for the invention of what became the Internet. More concretely, it had little influence on the actual inventive activity of the researchers who did the inventing.")]

Those of the "Internet Was Designed to Survive Nuclear War" Faith

The NSFNet Final Report stated "An outgrowth of the Department of Defense's Advanced Research Projects Agency, the ARPANET's packet-switching scheme was meant to provide reliable communications in the face of nuclear attack." [NSFNet Final Report p. 6]

An evening with Paul Baran, Computer History Museum
Interview with Leonard Kleinrock re origins of ARPANet Inside the Internet

(BBC Documentary which includes Interviews with Leonard Kleinrock, Donald Watts Davies, Dennis Ritchie, Steve Bellovin, Berners Lee - includes statement by Kleinrock rejecting myth that Internet was invented to survive nuclear war)



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