Piano and Protocols: The Story of Inventor Radia Perlman

Network engineering and music are two disciplines that seem worlds apart.

One involves maintaining the connectivity of computer networks while the other organizes sound across instruments. At a surface level, it seems there are few points of intersection. In actuality, the two fields have much more in common than what is typically realized.

One engineer in particular has used her aptitude for science and the arts to push the boundaries of invention. NIHF Inductee Radia Perlman breaks the mold of what a “typical” inventor’s story looks like and proves that there is no single path to success. Thanks to an upbringing that encouraged her to explore different interests, she developed the ability to approach engineering in the same way she approached music: with a dedication to understanding the bigger picture.

Perlman grew up in New Jersey, the daughter of two engineers. Her father worked on radar while her mother was a computer programmer, and although she always excelled at math and science, Perlman says she also had an affinity for other subjects. “I was interested in artsy things,” she explained. “I loved classical music and played piano and French horn. I also loved writing, composing music and art.” At one point, she considered giving up on piano, until an elementary school chorus teacher chose her to play for the school choir. To this day, she enjoys playing as an accompanist for others.

Perlman was first introduced to computer programming in high school when a teacher took several students to a class at the Stevens Institute of Technology. Though initially it was an exciting opportunity, the experience proved discouraging for Perlman when she felt she could not keep up with the more advanced students in the class. It wasn’t until she was a sophomore at the Massachusetts Institute of Technology (MIT) in the 1970s that she saw the formerly unpleasant subject in a new light. While taking a physics class, a teaching assistant asked her if she’d like to be a programmer for a project he was working on. After telling him that she didn’t know how to program, he responded by saying, “Yes, I know. That’s why I’m asking you. You’re obviously bright, so I’m sure you can learn.”

Music and programming both require the ability to learn a new “language,” and Perlman’s study of music paralleled her study of programming concepts. She was able to master the technical aspects of program design in the same way that she learned to combine a scale of notes into a composition. While still an undergraduate, Perlman worked as a part-time programmer writing system software for MIT’s Logo Group and even created the Toddlers Own Recursive Turtle Interpreter System (TORTIS) to help teach children about computer programming.

Perlman observes children using the TORTIS Button Box, circa 1974-76. (Photo courtesy of Radia Perlman)

She stayed at MIT to earn her master’s degree in math, though the experience was not easy for her. As a shy student, Perlman struggled to find a thesis adviser and found herself unable to enjoy graduate school. Eventually, a friend suggested she join a group at BBN Technologies designing network protocols. It turned out that she loved the work, and 10 years later she returned to MIT to complete her doctorate in computer science.

In 1980, Perlman joined Digital Equipment Corporation (DEC) to design routing for DECnet, a network protocol developed to help computers better communicate with each other. Perlman described this opportunity as “the perfect job in the perfect place at the perfect time.” It was at DEC that she made her defining discovery: the Spanning Tree Protocol (STP). STP configures Ethernet networks to deliver data and avoid loops. The development of STP has been critical to the successful growth of the internet, enabling technology that can create large networks with hundreds of thousands of nodes over a large area.

In the excitement of completing the STP algorithm, Perlman channeled her nervous energy into writing a poem about it.
 

Algorhyme

I think that I shall never see
A graph as lovely as a tree.
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.
 

In the spirit of a true innovator, Perlman did not become complacent with her work. To improve STP, she began working on an updated version of it called TRILL (TRansparent Interconnection of Lots of Links). Essentially, the TRILL protocol expands on the work of STP to allow Ethernet to make optimal use of bandwidth.

While creating new internet frontiers, Perlman found time to author and co-author two books. “Interconnections” is a widely read text on network routing and bridging, and “Network Security” is a text on cryptography and how it is used in networks. She said “Interconnections” helped readers wade through the murky, jargon-filled world of networking. “My book created order. It was easy to understand while being conceptually thought-provoking, and a large part of the technology described was stuff I’d invented.”

In this instance, and likely many others, Perlman knew how to problem solve in the most effective manner. Her understanding of the need for clarity and order in computer science ties back to her knowledge of musical arrangement. In a similar way that a smooth sequence of notes creates a melodic sound, engineers must make connections between smaller parts to develop a greater mechanism.

For Perlman, this kind of comprehensive approach was the perfect harmony.