Sharla Boehm earned a teaching degree from the University of California, Los Angeles, before she channeled her talent for math into computer programming. While working at the RAND Corporation, she built a groundbreaking simulation, originally conceived to strengthen military communications during the cold war. The simulation—and her work—would ultimately lay the foundation for the modern Internet. 

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Archival: What if a warning siren sounds? What should you do? Don’t hesitate. Find cover.

Katie Hafner: In the early 1960s, the United States and the Soviet Union were in a treacherous standoff. Each side was on high alert, with a growing stockpile of nuclear weapons — ready to launch at the first sign of an attack.

U.S. authorities weren’t just worried about how to weather an initial attack. They worried about how they would mount a counterattack if a bomb knocked out communications.

After all, these fragile systems were highly vulnerable to nuclear attack. If one bomb hit just right, all military communications could go down, leaving the entire country essentially defenseless.

So, the U.S. military put scientists to work. Their charge: to invent a communications network that could survive an attack. And on the team was one scientist who created an ingenious computer simulation — using 1960s-era computers.

Doug Rosenberg: As a piece of programming, it’s just unthinkable that she could do what she did. I mean, beyond comprehension.

Katie Hafner: And then, she would all but disappear into history as soon as her work was done.

Katie Hafner: This is Lost Women of Science. I’m Katie Hafner. And today we have the story of Sharla Perrine Boehm, a brilliant computer programmer — and so much more.

The simulation she created in the early 1960s wouldn’t just be offered up as a way to safeguard U.S. communications in the event of a nuclear attack… It was so ingenious that later, long after she left the field, her work would help bring about one of the most world-changing inventions ever: the internet.

But before we start, a mea culpa from me. In 1996, my book, Where Wizards Stay Up Late: The Origins Of The Internet, was published. It's a definitive history of the Arpanet, the network that would eventually evolve into the internet. And I never once mentioned Sharla — never even came across her name. Actually, that can’t be true. She co-authored a major paper, a paper I must have seen, and yet I never thought to ask, “Who is that?” It was always the famous man, her colleague Paul Baran, that I focused on.

And so, I want to make up for that today. And since I’m clearly not the expert when it comes to Sharla Perrine Boehm, I’ve brought in our producer Samia Bouzid to tell us Sharla’s story.

Samia Bouzid: On the night of November 24, 1961, it seemed like the nation’s worst nightmare had come to pass. The ballistic missile early warning systems across the U.S. went dead all at once. At a base in Omaha, officers on overnight duty tried to call communications headquarters in Colorado Springs — but the phone lines were dead too. That could mean one of two things: Either there had been some inexplicably vast communications failure, or the U.S. was under attack.

The officers scrambled to wake up General Thomas Power, the commander in chief of the Strategic Air Command, who immediately ordered nuclear forces on full alert. In the dark, bomber crews guided their planes onto runways. The U.S. was ready to strike.

But minutes later, the Strategic Air Command finally made contact with communications headquarters, by sending radar messages through a bomber that was already in the air. And headquarters reported that there was no attack. It was just a regular, quiet night.

So what happened? It turned out that a single motor at a relay station out in Colorado overheated and caused the entire system outage. It just happened to be the one relay station that all communications passed through.

So here was the United States, one command away from an accidental nuclear war… all because of some janky phone circuits. Clearly, something had to be done.

Paul Baran: This was the height of the Cold War.

Samia Bouzid: This is the computer scientist Paul Baran, speaking in an oral history recorded by the Charles Babbage Institute in 1990.

Paul Baran: And it was a very dangerous situation because there's no communications that can survive an attack.

Samia Bouzid: At the time of that nearly fateful outage, he was working at the RAND Corporation, a prominent research institute in Santa Monica, California. Baran and others at RAND were working on national security issues, including what to do about its disastrously fragile communications system.

The problem boiled down to this: back in the early 1960s, military communications mostly happened over phone lines and shortwave radio. The circuits that transmitted these communications were centralized. That meant every message got routed through at most five nodes, or connecting points. If those nodes took a hit, there was no other path. The entire network went down.

And so Baran became convinced that the solution was to create a new form of communication. Not with phones or radio. One that sent messages through computers. And he was already envisioning a network that could survive a catastrophic accident or attack.

[Paul Baran speaking in background]

Basically, set up a network without any central node. Each node is just connected to its neighbors. And then, make sure it's connected to enough neighbors that even if some get knocked out, the network as a whole will still survive.

Unfortunately, selling his colleagues on the idea wasn't so simple. They were mostly experts in old-school analog communications, not digital computers. And they weren’t especially interested in hearing from the rogue computer scientist who had wandered into their turf.

Paul Baran: They'd get a little huffy about it because, uh, “What the hell is this guy in computer science talking about communications?” People who had a background in analog communication did not understand digital processing. So, some of the things one would say would sound like utter nonsense.

And Baran couldn’t stamp out their doubts. Every time he put one concern to rest, someone would raise another.

And his colleagues at RAND were just one problem. Some of his biggest detractors were also some of the most important people he had to convince: the managers of AT&T.

AT&T controlled everything to do with long distance communication, and so Baran really wanted to get them on board.

Paul Baran: The whole idea at the time was that we had hoped that AT&T would do this with the Air Force, cause AT&T had the monopoly.

Samia Bouzid: But when Paul Baran pitched his idea to the company, the response was a mix of skepticism and condescension. He never forgot how a room of AT&T engineers reacted when he tried to describe how his idea would work.

Paul Baran: “Wait a minute, son. You mean you open the switch here before the traffic has left the other end of the country?” I said, “Yeah.” And they look at each other, shake their heads and say, “Son, this is how a telephone works,” and it got pretty patronizing.

Samia Bouzid: No matter what he said, it just wasn’t enough to win over his colleagues, let alone the AT&T guys.

They just struggled to fathom that a digital network could reliably get a message from A to B without relying on any central nodes.

So what Paul Baran needed was some way — or someone — to prove his idea could work. And that someone turned out to be a young math teacher who worked across the street at Santa Monica High School. In the late 1950s and early 1960s, she spent summers and sabbaticals moonlighting at RAND, writing code. Her name was Sharla Perrine.

Sharla would have been the odd one out back then, the rare woman among a sea of men.

Doug Rosenberg: I mean, women were secretaries back then. There were not women in engineering jobs in 19, the early 1960s. It was a bunch of guys in crew cuts.

Samia Bouzid: This is Doug Rosenberg, a systems engineer.

Doug Rosenberg: There were not women in engineering jobs in the early 1960s. It was a bunch of guys in crew cuts.

Samia Bouzid: Doug was a close friend of Sharla’s husband, Barry Boehm. He says Sharla could hold her own. Born in Seattle, she had grown up in Santa Monica during the Depression. Her mother, who had immigrated to the U.S. from Sweden, raised Sharla by herself — her marriage ended around the time Sharla’s older sister died in 1932. Sharla was 2 at the time. So, in the Perrine household, there were no gender roles. If something broke, there was no man around to fix it and no money to hire someone. So, Sharla’s mother figured out how to do things herself.

Tenley Burke: Her mother was a carpenter, so that she could fix things and create things and not have to buy them. Anything that needed fixing they did themselves.

Samia Bouzid: This is Sharla’s daughter Tenley, and she says Sharla was the same way.

Tenley Burke: She was just no-nonsense, let’s do it ourselves, you can do anything. She didn’t like dilly dallying. She got down to business, and that’s just who she was. She was serious about everything she did.

Samia Bouzid: Sharla always had a knack for math, and after earning a degree in teaching from UCLA, she went on to teach math, first at a junior high and then at a high school. But she also gravitated toward programming.

Tenley Burke: I could see that RAND was a pull for her because it was so local and it was full of people who were thinking big thoughts. And she always said that she liked to talk to men at parties because they were talking about interesting things, and that’s what she wanted to be doing — she wanted to be in the interesting conversations.

Samia Bouzid: RAND did turn out to be an intriguing workplace. While she was waiting for her security clearance in 1959, she met someone who would join her in many interesting conversations: a computer scientist named Barry Boehm. Here’s how he told it to the Computer History Museum in 2017.

Barry Boehm: There we were down there in the basement and we, we got to know each other and she's now my wife.

[Background chatter]

Samia Bouzid: In addition to falling in love, Sharla also sharpened her programming skills writing simple computer code. And then, in the early 1960s, came her big assignment.

Paul Baran needed someone to prove that his big idea — the one that could save the country from its massively unreliable communications systems in the event of an attack — could actually work.

[AD BREAK]

Doug Rosenberg: The way you figure out if it's gonna work or not is you simulate it.

Samia Bouzid: Doug Rosenberg again. And simulating Paul Baran’s idea became Sharla’s job. The basic idea she needed to simulate went something like this:

Doug Rosenberg: So you first would take a message and you'd chop it up into little packets…

Samia Bouzid: Imagine cutting up a letter, and then sending each piece in a separate envelope across the country, from LA to New York. Each envelope takes a different route. And there’s no central post office that every letter has to pass through.

Doug Rosenberg: It could go from Los Angeles to Kansas City to Chicago to New York, or it should go from Los Angeles to Dallas to Atlanta to New York, right? So you can route this packet lots of different ways…

Samia Bouzid: This technology was nothing like an old-fashioned phone line, where a message followed a hard-wired path from A to B — and if something went down, the message was gone.

In fact, the way Sharla built her network, it could find a way to get each message packet through, no matter what. It was a lot like the country’s network of post offices. If one post office burned down, mail delivery wouldn’t stop. Mail would just get routed through another office. Same went for Sharla’s simulation. It had nodes, but no central one.

Doug Rosenberg: And then her simulation had some subroutine in there called “damage.” And, she could run this “damage” subroutine and say, “Alright, everything's running smoothly — now let's damage it by knocking out these five nodes,” and then see how it responded.

Samia Bouzid: Some message packets would inevitably get lost, but Sharla found that if you made a few copies of each packet and sent them down different paths, you could guarantee that at least one copy would make it. And then, once all the separate packets got to the other side, they would use serial numbers in their headers to arrange themselves back in order. And just like that, you could read the original message.

Paul Baran called this technique “hot potato routing,” because each time a packet arrived at a node, that node had to kick it to the next one as quickly as possible.

And the trick — really the genius — behind this technique was that there was no fixed path for each “hot potato.” The network itself made up the path in real time. So, if one node suddenly went down, the network would just send the hot potato a different way. Essentially, the network would heal itself.

Doug Rosenberg: It healed in terms of, “Oh, well you just took out those five nodes, but I know how to respond to that now.”

Samia Bouzid: In Sharla's simulation, each packet changed its route on the fly, depending on the state of the network. All in real time. And the fact that she pulled this off with 1960s computer power is pretty mind-blowing.

Doug Rosenberg: If this was 2025, this would be called machine learning because that's really what it was. She was teaching the network to learn how to respond to nodes dropping out. Machine learning was definitely nonexistent at that point. And yet, if you look at this 1964 paper, it's kind of unquestionably what it is.

Tony Rutkowski: To have this understanding of itself and to adapt itself is something that's pretty profound.

Samia Bouzid: That’s Tony Rutkowski. He’s an engineer and lawyer and history buff who’s spent more than 50 years working in information communications. He worked on internet policy at the Federal Communications Commission in the 1980s, and he was actually the one who tipped us off to Sharla’s incredible work.

Tony Rutkowski: Here you had the network itself imbued with this, this AI! It's the initial spark of, if you will, network AI that was created. That really changed everything.

Samia Bouzid: First and foremost, Sharla’s simulation gave Paul Baran the proof he was looking for. Proof that it was possible to create a nationwide network that was intelligent and resilient.

Her simulation showed that even if half the network got destroyed instantly, the remaining nodes reorganized themselves and got communications going again in under a second.

To Paul Baran’s frustration, AT&T never came around — but according to him, their resistance wasn’t all based on technical doubts.

Paul Baran: It got to a point once upon a time, near the end of dealing with them, is, they're saying, well, "First it isn't gonna work. And the second, if it did work, we're not gonna put [them] in competition with ourselves." So, it never got taken very seriously by AT&T all during that time.

Samia Bouzid: Nevertheless, both RAND and the Air Force were totally on board with putting hot potato routing into practice, and they could have gone ahead and done it — even without AT&T’s dollars. They just had to go through the Department of Defense to get the funding.

This is where I would love to be able to say that Sharla’s simulation quickly got built and we put down the weapons that were on high alert, and everyone breathed a sigh of relief. But, unfortunately that’s not exactly how it went.

The problem was, Paul Baran didn’t have much confidence in the Defense Communications Agency, which would be getting the funding from the DoD. He just didn’t think they could actually implement this new technology correctly. And he was afraid that if they botched it, it would be really hard to ever get the project off the ground again.

Paul Baran: We had zero technical competence. We had some discussions and mutually concluded that all they would do is screw it up. So I found myself in the position of recommending they not proceed. And that's what happened.

Samia Bouzid: The DoD did not give the agency the funds to build the distributed network. And Sharla’s brilliant work got tucked away… until it reemerged in a totally new form several years later.

In October 1969, a message popped up on a computer screen at Stanford University in Northern California. Well, part of a message. It was the letters “l-o,” sent from another computer hundreds of miles away at UCLA. The rest of what should have been the word “login” never made it.

But, as anticlimactic as that may sound, this incomplete message was the first communication sent over the ARPANET, an early computer network that the DoD’s Advanced Research Projects Agency was building — not to protect the country in case of an attack, but to share computing resources across institutions.

Within a few years of that first botched message, dozens of universities and government-run research organizations had connected to the network. And all of the messages sent across this network were happening thanks to one key technology: packet-switching.

This is what “hot potato routing” eventually came to be called. Those tiny chunks of broken-up messages are the “packets,” and it’s “switching” because of the way the routes between nodes change in real time. So, packet switching.

This technology — really, Sharla’s technology — is what made it possible for messages to get chopped up, fly across a computer network from UCLA to Stanford or MIT or NASA, and reassemble on the other end.

But the ARPANET was just the beginning.

Tony Rutkowski: What's referred to as the internet is actually another layer on top of the digital packet network.

Samia Bouzid: Tony Rutkowski again.

Tony Rutkowski: It's just another layer of an intelligent adaptive network on top of another one. You can actually concatenate these things in different layers.

Samia Bouzid: That’s right. That resilient network that Sharla coded up in the 1960s underpins our entire modern internet.

In the 1990s, there were some lively debates about who had been the “father” of the internet. A few names were bouncing around. Sharla’s colleague, Paul Baran, was one of them, thanks to his work on packet switching. Then there was the British computer scientist Donald Davies, who was working on similar things around the same time. Meanwhile, the American computer scientist Leonard Kleinrock argued that that honor of inventing packet switching actually belonged to him — and that he was, quote, the “Inventor of the Internet Technology.”

But as for Sharla Perrine Boehm, that name didn’t come up.

Maybe because, by the time the ARPANET was taking off, Sharla had left RAND — and the world of computer programming altogether.

In 1965, one year after her paper on packet switching was published, she had her first daughter. And she left RAND to become a stay-at-home mom. Her husband, Barry, stayed in the world of computer science, and he was closely involved as the ARPANET emerged. But, Sharla put that chapter of her life behind her. Here’s her daughter Tenley again.

Tenley Burke: What she really wanted to do was have a family, and participate in that family fully. And I put that down to her childhood and her mother being a single mother during the Depression and not being able to be home. I think it was a life achievement for her to be able to stay home.

Samia Bouzid: And Tenley thinks that the death of Sharla’s sister all those years ago influenced her decision too.

Tenley Burke: I think there were things that haunted her from her past that she just didn’t want to repeat. She wanted everyone to be safe and sound.

Samia Bouzid: For the next couple decades, she put all her energy into her family and community, especially the Girl Scouts. Caroline Batzdorf was friends with Sharla’s daughters and she was also one of those Girl Scouts. She knew Sharla really well.

Caroline Batzdorf: She was one of the most understated women I've ever known. Just quietly getting on with it. Not drawing attention to herself in any way, just putting other people forward. She was in the background with her hand at our backs. Encouraging us to strive, encouraging our creativity, showing up, being supportive, making sure that we were well-rounded, quietly persistent in all these ways where she made a difference.

Samia Bouzid: And Sharla never really talked about her past life as a computer programmer. Tenley was in her 20s before her mother even told her just what she had done at RAND.

Tenley Burke: Sharla poured herself into motherhood and community service and Girl Scouts, and yeah, there was just no sense in talking about, you know, “One time I was a programmer at RAND and I wrote some code.” It just wasn't something that she would mention.

Samia Bouzid: Hearing Sharla’s story, it would be easy to lump her in with so many women whose stories we explore on this podcast — women who had to give up their work to raise kids because society said so, women who had so much to offer, but just never got the chance.

But, everyone I talked to who knew Sharla personally insisted that she never saw it that way. She loved math and computer programming, but she moved on from RAND, even as the work went on without her.

Tenley Burke: I think she was proud of it. I think it was probably quirky to her that something she did in the early sixties turned into the internet. I mean, I mean, how bizarre is that?

Samia Bouzid: But she didn’t dwell on it. She had more to offer.

Tenley Burke: Sharla was so many things. She was intelligent, she was organized, she was strict. She was kind. She cared. She worried. She was present. She wanted to help. She wanted everyone to succeed and try their hardest.

Samia Bouzid: Friends who knew Sharla say she should absolutely be celebrated for her technological achievements, but not reduced to them because she did so much more with her life.

She raised a family, she nurtured her community, and she traveled often — accompanying her husband, Barry, whenever his work as a computer scientist took him to interesting places.

Tenley Burke: They were definitely two peas in a pod. As they aged, they would sit next to each other and fall asleep with their heads, like, tipped towards each other. It was the cutest thing. They were, they were quite the team.

Samia Bouzid: In 2012, Sharla had a stroke that left her unable to speak, though Tenley says she could still hear people and smile.

By the time Sharla Perrine Boehm died in 2023, at the age of 93, nearly two-thirds of the world’s population was using the internet that she had unknowingly helped usher in as a young computer programmer.

But throughout her decades as a teacher, mother, and community leader, she also touched many lives much more intimately. She was the woman supporting so many girls, focused not on her own legacy, but on theirs, on how much they could accomplish, now that the world was theirs.

Katie Hafner: This episode of Lost Women of Science was produced by Samia Bouzid, with help from senior producer Laura Isensee. Our senior managing producer is Natalia Sánchez Loayza.

David De Luca was our sound designer and engineer. Lizzie Younan composed all of our music. We had fact-checking help from Lexi Atiyah.

Thanks to Eowyn Burtner, our program manager, Amy Scharf, my co-executive producer, and Jeff DelViscio at our publishing partner, Scientific American.

Lost Women of Science is funded in part by the Alfred P. Sloan Foundation, the Anne Wojcicki Foundation, and many generous individual donors. We're distributed by PRX.

For show notes and an episode transcript, head to lostwomenofscience.org, where you can also support our work by hitting the donate button.

I’m your host, Katie Hafner. Thanks for listening!

Host
Katie Hafner

Producer
Samia Bouzid 

Senior Producer
Laura Isensee

Guests

Doug Rosenberg is a systems engineer and was a friend of Sharla’s husband, Barry Boehm. He is the founder and CEO of Parallel Agile, Inc. and teaches at the Caltech Center for Technology and Management Education.

Paul Baran was a computer engineer who worked at RAND in Santa Monica, California, where he helped create the underpinnings of the Arpanet, the government-sponsored precursor to the modern internet. He died in 2011. He is featured through excerpts from his oral history recorded by the Charles Babbage Institute.

Tenley Burke is one of Sharla’s two daughters. She has worked at the University of Idaho and is on the board of Boehm Center for Systems and Software Engineering. An avid traveler and gardner, she is also the proud mom of two boys.

Tony Rutkowski is an engineer, lawyer and history buff. His career spans telecommunications, mobile, internet, satellite and broadcasting fields in the U.S. and Europe. He worked on internet policy at the Federal Communications Commission in the 1980s.

Caroline Batzdorf was friends with Sharla’s daughters and involved in the Girl Scouts that Sharla helped support.

Further Reading:

Where Wizards Stay Up Late: The Origins of the Internet, Katie Hafner and Matthew Lyon, Simon & Schuster, 1996 

Recoding Gender, Women’s Changing Participation in Computing, Janet Abbate. MIT Press, 2012

Season 2: A Grasshopper in Tall Grass. Lost Women of Science, 2022