How tech pioneer Radia Perlman overcame bias to invent a core component of the internet

By Cyril Bouquet, Jean-Louis Barsoux, and Michael Wade

Computer scientist Radia Perlman is often referred to as the “Mother of the Internet”—a title she shuns, but which has stuck due to her key role in driving the growth and development of the internet.

Perlman is rightly considered an internet pioneer, but she also encountered barriers because of her gender. And today, despite tremendous innovations by Perlman and other women like her, tech continues to be a tough environment for female engineers.

An accidental techie

When Perlman entered MIT in the late 1960s to study math, she had no interest in computer programming, thanks to a discouraging class she’d taken during high school. Ironically, this outsider status would serve Perlman well. Uncontaminated by computer industry norms, her boundary-spanning abilities would become a source of creative strength.

She finally learned computer programming thanks to a teaching assistant who asked her to do some coding for his project. She told him she didn’t know how to program, to which he responded: “I know. That’s why I’m asking you. I have no money to pay you. You’re obviously smart, and I’m sure you can learn.”

Despite the lack of pay, she decided to take on the challenge. Having learned to code, she became inspired to find a way to teach programming concepts to young children. During her masters’ degree, she designed a programming language, along with special keyboards and other input devices, that allowed preschoolers to control an on-screen turtle. Her work went on to spawn an entire field known as “tangible computing.”

Perlman soon realized she would never be taken seriously by other engineers if she continued to work with kids, but her experience of considering the needs of children, her end users, would inform her work in important ways.

Noticing what others miss

In 1976, Perlman began designing network protocols—the rules provided to computers when they interact in groups.

As she learned to write them, she began to appreciate the beauty of the invisible webs formed between computers. She also noticed that the routing algorithm for the ARPANET—the precursor to the internet—lacked stability, making it vulnerable.

“If you just injected a few bad messages, the network would be down forever,” she told an audience at an event hosted by the National Science and Technology Medals Foundation in 2019. “You could reboot your PC, but you can’t reboot a network. [I]f it’s broken, you’re really in trouble.”

Computer networks, she realized, could not afford to be this fragile. The epiphany led her to devote considerable time to thinking and writing about “self-stabilizing” networks.

In 1980, Perlman joined Digital Equipment Corporation (DEC), which was offering customers the equivalent of a miniature private internet known as an “Ethernet.” Called “DECnet,” the service could connect a few hundred computers, provided they were all housed in the same building.

Perlman quickly recognized the limitations of DECnet. Her work on routing protocols made her realize that these computer clusters could not communicate across separate Ethernets. She tried to argue that a network protocol could make that possible. But according to a 2018 interview of Perlman in Nature Electronics, her bosses responded by saying, “Our customers would never want to do that.”

Connecting Algorithm to ‘Algorhyme’

Years later, one of those bosses came back to her with a challenge: to design a “magic box” that would sit between two Ethernets, allowing people to communicate between interconnected networks. The catch? The new “box” should not interfere with the way users currently interacted with their computers. It should be as though they were speaking on a single Ethernet.

At first glance, this challenge might not seem very daunting. Communication could be achieved by simply sending data packets between the different networks. Think of these packets as cars traveling along highways. But there was a problem with this approach: If there were any “loops” on the highways, the packages of information would circle around forever, never reaching their destinations.

Perlman came up with a solution that was as simple as it was elegant. Drawing inspiration from nature, she decided to design a protocol based not on a highway, but on a tree—the revolutionary Spanning Tree Protocol (STP). To allow small groups of private computers to evolve into open networks, the STP uses a mathematical formula that calculates the shortest distance between one place and every other place. The end result resembles a tree in that the shortest distance from a single leaf to a single root is always directly backward and down the tree.

To underline the simplicity of her solution, she wrote a poem that captures its chief properties. Typical of her convention-busting attitude, she included the poem in the abstract of her patent application and the paper that she later published.

Algorhyme
I think that I shall never see
A graph more lovely than a tree.
A tree whose crucial property
Is loop-free connectivity.
A tree which must be sure to span
So packets can reach every LAN.
First the root must be selected.
By ID it is elected.
Least cost paths from root are traced.
In the tree these paths are placed.
A mesh is made by folks like me
Then bridges find a spanning tree.

‘Mother of the Internet’

Initially, thanks to shortsightedness and gender bias, the STP was not recognized for the breakthrough it was. It was “hard to explain to management that these guys [who] were making lots of money for the company had done it wrong,” explained Perlman on the Stroke of Genius podcast.

Perlman says her bosses also described her successes differently compared to her male colleagues: “My designs were so deceptively simple that it was easy for people to assume I just had easy problems,” she told The Atlantic in 2014. “Whereas others, who made super-complicated designs [that were technically unsound] and were able to talk about them in ways that nobody understood, were considered geniuses.”

Her achievement wasn’t fully recognized until consumer demand finally shifted in the direction she’d long predicted: People began demanding seamless communication between interconnected networks. Yet, she continued to experience bias.

“I had a manager once who was…really smart, really well-meaning,” she recalls in the same Atlantic interview. “But… he never quite knew what to make of me. When I did something really clever, he was smart enough to understand its importance, but then he’d look at me all confused and say, ‘How did you think of that?'”

What really changed the male-dominated industry’s perception of Perlman was her 1992 book Interconnections, which shed light on the field of computer networks and was based, in large part, on technology she’d invented and patented. As entertaining as it was enlightening, the book raised her profile and gave her a bigger voice, without having to shout.

Although the original STP has since been replaced by upgraded versions (often revised with Perlman’s input), her protocol design is still used for routing IP today. In 2014, her key contribution to the internet’s infrastructure finally led to her induction into the Internet Hall of Fame, prompting one journalist to dub her “The Mother of the Internet.”

Now, Perlman holds over 100 patents. Though she has reached retirement age, she remains active in the field as a fellow at Dell EMC.

A discouraging environment

The attitudes and attributions that Perlman fought against are unfortunately all too present in the technology industry, which remains a toxic, discouraging environment for women.

According to a nationally representative survey by the Pew Research Center published in 2018, women in the STEM sector are more likely than those not in STEM sector to say they have experienced discrimination in the workplace (50% vs. 41%). And although the STEM job cluster has seen the most growth in recent decades, women’s representation has decreased from 32% in 1990 to 25% today.

Most troubling though is the fact that over a third (35%) of women in STEM with a postgraduate degree believe their gender has made it harder to succeed on the job, compared with just 10% of women in STEM with some college or less education. In other words, those most likely to apply for patents are those who feel most discriminated against.

The barriers to innovation that women continue to face deprive organizations and society of potentially groundbreaking ideas of the kind generated by Radia Perlman. She persevered but countless others are discouraged. Had she not managed to overcome those barriers, the internet might never have become the reliable and ubiquitous tool it is today.

Cyril Bouquet, Jean-Louis Barsoux, and Michael Wade are IMD faculty members and the coauthors of ALIEN Thinking: The Unconventional Path to Breakthrough Ideas (PublicAffairs; March 16, 2021).