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The Many Sides of Radia Perlman

Call her a mother of two, but don’t call Radia Perlman the “Mother of the Internet.”

Engineer, author, inventor and, Intel’s director of Network and Security Technology, Perlman never cottoned to the label despite its use nearly every time she speaks at a technical conference or is written about in a story.

Radia Perlman
“‘Mother of the Internet.’ I did not come up with that,” says Radia Perlman of Intel.”

“‘Mother of the Internet.’ I did not come up with that,” Perlman said. “I was interviewed for some thingy or other, and the writer came up with that. I didn’t see the article in advance, and it kinda stuck. One reason they thought they could get away with it is because several people claim being the ‘Father of the Internet,’ and ‘Mother of the Internet’ wasn’t already staked out.”

The reason Perlman winces at the label is “it’s a title that one has no clear way of getting, unlike, for example, a Ph.D.,” said Perlman, who earned hers in computer science from MIT in 1988. “It’s overreaching because I don’t think any single individual deserves credit for inventing the Internet. Many people had large roles, including, actually, Al Gore, and in a sense it was something that was inevitable. Also, being called ‘Mother of the Internet’ is a little strange in that it emphasizes gender. I mostly don’t even think about gender.”

Coined by a publication whose name she forgets — hence, “thingy” — the cringe-worthy nickname is probably something she’s stuck with. Not helping her cause is a Wikipedia entry that references the maternal moniker in the opening sentence. But also noted are her myriad accomplishments and honors: SIGCOMM lifetime achievement award and similar honor from the advanced computing systems association USENIX … lauded as one of the 20 most influential people in the tech industry by Data Communications magazine … named Silicon Valley Inventor of the Year by an intellectual property law association … an honorary doctorate from the Royal Institute of Technology of Sweden … one of three recipients of the inaugural Women of Vision Award from the Anita Borg Institute. That’s only the short list for the daughter of engineering-grounded parents.

The achievement that has made Perlman a household name in certain cerebral circles is the spanning tree algorithm, which she invented in 1985 while working for the now-defunct Digital Equipment Corporation. Her protocol transformed Ethernet from a technology that could only work with a few nodes over a limited distance, into something that could create fairly large networks. Her protocol, as the name suggests, creates a spanning tree within a mesh network of connected layer-2 bridges, which are typically Ethernet switches, then disables the links that are not part of that tree.

“The protocol is really very simple,” Perlman said. “I can summarize it in a poem!”

Poem? Yep, the woman who has made large contributions to many areas of network design and standardization is also a poet. Her ode to the spanning tree algorithm, titled “Algorhyme,” is a geek favorite and has even been set to music, thanks to her son, Ray. Perlman’s daughter, Dawn, an amateur opera singer, even performed it at a recital. The proud mom accompanied on piano.

The poem, Perlman’s first, could serve as a “Spanning Tree for Dummies,” and was the abstract of the paper in which Perlman published the spanning tree algorithm:


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 that 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.

Perlman said she is a bit surprised that the spanning tree is what she’s most known for given that “I always thought it was a bad idea to forward Ethernet packets” and that it took her less than a week to invent the algorithm, write the specification and, of course, pen the poem. Other networking contributions include inventing concepts that made a particular type of routing protocol, called “link state routing,” stable, scalable and easy to manage. The protocol she designed for DECnet got adopted by the International Organization for Standardization and renamed IS-IS, and is the routing protocol of choice in most ISPs today. Recently she’s been working on standardizing TRILL (TRansparent Interconnection of Lots of Links), a concept she introduced to the industry that allows forwarding Ethernet packets using IS-IS instead of spanning tree. (“My apology to the world for introducing spanning tree,” she mused.) Perlman also has done important work in security, including the ability to make data expire and become unreachable, even though backups of the data still exist.

When Perlman isn’t inventing or dabbling in poetry, she’s writing books. While their titles suggest dry reading that only a computer scientist would relish — “Interconnections: Bridges, Routers, Switches and Internetworking Protocols” and “Network Security: Private Communication in a Public World” — Perlman said one mustn’t judge her books by their covers.

“They’re not just technical books,” she said. “They’re actually very funny.”

When talking about the lighter side of Radia Perlman, one must include her stab at stand-up comedy. Yes, stand-up comedy. While on a cruise to Novosibirsk, Russia to see a solar eclipse in full glory, Perlman signed up to perform in a passenger talent show.

“To play piano,” she recalled. “On the day of the show, Charlie [Perlman’s significant other] and I walked around the ship and it dawned on us that we hadn’t seen a piano. When we were told there wasn’t one, I decided to try stand-up comedy. It’s something I always wanted to do.

“That night at the talent show, the audience was pretty drunk and I couldn’t possibly have been as funny as they were acting like I was. They were rolling! The next day we kept hearing other passengers talking about my performance and retelling some of the stories.”

Creative writing skills and a penchant for comedy are desirable attributes, but not why Intel hired Perlman, who turns 60 in December. Based out of Redmond, Wash., she joined the company in early March as an Intel Fellow, one of the highest levels of technical achievement within the company. Now after a couple of months on the job, Perlman, who was at Sun for 13 years, and also previously worked for Novell and Digital, finds herself at a company that was never on her radar as a place of employment.

“I never thought about working at Intel,” Perlman said. “I always figured they did all these mysterious chip things. I am in awe of it, but never thought about working here because I have no expertise in things like doubling the number of transistors every 2 years just because Moore’s Law says you can, or how to make a room really, really, really clean. I never thought there would be anything interesting for me to do and they wouldn’t be interested in me.”

Jesse Walker, a principal engineer at Intel Labs, recommended Perlman to Intel Labs Vice President Wen-Hann Wang, and the recruitment effort obviously panned out. It didn’t hurt that Perlman’s daughter had babysat Walker’s kid.

“I’ve always been pretty happy where I’ve worked, but so far I’m the happiest here,” she said. “People tend to be intellectually curious and invite participation and advice from those who have fresh eyes and fresh expertise. They have passionate discussions as nerds do, but people do listen to each other.”

This content was originally published on the Intel Free Press website.

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