The character arc of Radia Perlman

Who is Radia Perlman?

She never took anything apart. She built what holds it together.

Both her parents were engineers for the United States government: her father on radar, her mother a mathematician by training working as a computer programmer. She found mathematics and science effortless and fascinating, and was a perfectionist about everything else too. She played the piano and the French horn. Her mother helped with the maths homework, but mostly they talked about literature and music.

She has been clear that she did not fit the stereotype. She did not take computers apart and put them back together. In her own words about the programming class she took in high school, where she was the only woman: she was not a hands-on type person, it never occurred to her to take anything apart, and she assumed she would either get electrocuted or break something. It was that class, not the taking apart, that made her consider a career in computers.

She went to MIT and learned programming for a physics class. Her first paid job, in 1971, was as a part-time programmer in the LOGO Lab at the Artificial Intelligence Laboratory, writing system software like debuggers. Under Seymour Papert she built a child-friendly version of the educational robotics language LOGO, called TORTIS, for toddlers. She took a bachelors and a masters in mathematics, joined the MIT group at BBN for her thesis and got into network protocols there, and later took a PhD in computer science at MIT in 1988, on routing in environments where malicious network failures are present, which is still the basis of much of that field.

She went to BBN after graduating, made an impression on a manager at Digital Equipment Corporation, and joined Digital in 1980. In 1984 she was asked to design a straightforward protocol letting network bridges find loops in a local area network, using a constant amount of memory however large the network got. Loops were a real danger: a redundant path meant a bridge could forward a frame in several directions at once and flood the network into collapse. She produced the Spanning Tree Protocol, which lets a network carry redundant links as automatic backups while keeping a single active path between any two points. It was standardised as 802.1d.

What she did next is unusual. She said publicly what was wrong with it: that it took about a minute to react to a change in topology, during which a loop could bring the network down, and she has criticised changes made during standardisation. Later she invented TRILL to correct the shortcomings of spanning trees and let Ethernet use its bandwidth properly. She left Digital in 1993 for Novell, and Novell in 1997 for Sun Microsystems, where she was a Sun Fellow and earned forty of her patents; she holds over two hundred in total. She wrote the textbook Interconnections and co-wrote Network Security, both standard. She has taught at Washington, Harvard, MIT and Texas A and M, took lifetime achievement awards from USENIX in 2006 and SIGCOMM in 2010, was elected to the Internet Hall of Fame in 2014, the National Inventors Hall of Fame in 2016 and the National Academy of Engineering in 2019, and as of 2022 was a Fellow at Dell Technologies.

The moments

Radia Perlman's timeline.

Radia Perlman: frequently asked questions

What people ask about her line.

Sources

• Radia Perlman, English Wikipedia biography, filed under living people.
• Her doctoral thesis on routing under malicious network failure, MIT, 1988.
• Interconnections, and Network Security, her textbooks.
• Her own reflections on the high school programming class, as quoted there.