Radia Perlman: Primarily my role has been in invent­ing tech­nol­o­gy that has been get­ting used in the Internet. So, my phi­los­o­phy on tech­nol­o­gy is that peo­ple should­n’t have to under­stand it in order to be able to use it. And I’m not a real fan of gad­gets. I’m not a first adopter. I’m a last adopter kick­ing and scream­ing of all these things. 

But I under­stand things con­cep­tu­al­ly. So I’ve designed things that make the net­work self-configuring. It just…you plug it togeth­er and it works. Robust. Meaning that with­out me, some of the design, some of the alter­nate designs, if you just blew on the Internet it would fall over and die. Which is very…bad, because on your a per­son­al com­put­er, if it gets into a bad state, which it does all the time, you know that you turn off the pow­er and turn it back on again. But in a net­work there’s no on/off but­ton. So the net­work can’t get into these weird states. 

So the things that I designed made it so that the net­work would…you know, be self-fixing and self-organizing. There’s a lot of things that oth­er peo­ple designed that are fan­cy fea­tures that work if you’ve con­fig­ured them exact­ly right but if you make mis­takes it just will be hor­ri­ble. And so I’ve tried to talk to peo­ple like that some­times, and they claim their cus­tomers love to con­fig­ure things and they nev­er make mis­takes. And I don’t believe that. So my con­tri­bu­tions have been a sort of doing the oppo­site, of mak­ing things very sim­ple designs, very scal­able, and very robust.

Intertitle: Describe one of the break­through moments of the Internet in which you have been a key participant?

Perlman: So, the one that I’m kind of most known for is the span­ning tree algo­rithm. Now, with that is is that Ethernet was this tech­nol­o­gy that allowed a bunch of machines to all sit on the same wire. Just like in a con­fer­ence room, if there’s no mod­er­a­tor call­ing on peo­ple who raise their hands and you just have to talk when you want to, it’s good if you fol­low the Ethernet rules. It CSMA/CD. CS means ​“Carrier Sense,” means lis­ten before you start talk­ing. If some­one else is talk­ing, don’t talk. MA is ​“Multiple Access,” mean­ing be aware there’s oth­er peo­ple that are shar­ing the same band­width. And CD is ​“Collision Detect,” mean­ing if you’re talk­ing and some­body else talks, stop because you can’t be under­stood if both of you are talk­ing at the same time. And I’m kind of amazed at how many peo­ple don’t fol­low that. But at any rate, that only works for maybe a few hun­dred nodes, or else there’s just so many col­li­sions when peo­ple try to talk at the same time. 

So, I under­stood Ethernet as being a cheap way of hook­ing a few hun­dred nodes togeth­er, but it still was only one kind of link in the net­work. And the stuff I was design­ing was how you move data around from one link to anoth­er. But, kind of to my hor­ror, peo­ple thought that Ethernet was the new way of doing net­work­ing. So actu­al­ly I believe that if they called it Etherlink instead of Ethernet the world would not have been quite as con­fused. But because of that peo­ple were not doing the stuff that I had done, and instead only build­ing appli­ca­tions to talk over Ethernet. Which would mean only in a sin­gle build­ing, only with­in a few hun­dred nodes. 

So I tried to argue and peo­ple said ​“Oh, go away Radia. You’re just upset because nobody needs your lay­er any­more.” And I said, ​“Oh, but you may want to talk from one Ethernet to another.”

So as it turned out, a few years lat­er peo­ple real­ized ​“Hey, we do want our appli­ca­tions to work beyond a sin­gle build­ing.” So that was where my man­ag­er, because I do dis­trib­uted algo­rithms, he said ​“Oh, invent a mag­ic box that will sit between two Ethernets and move pack­ets around with­out the end nodes imple­ment­ing the same lan­guage as the switch.” You know, like IP as a Layer 3 thing. So with­out that, with only Ethernet. 

And so with the con­straints that we had at that point in time, which was that there was no spare fields in Ethernet, the pack­et had a max­i­mum size so that you could­n’t add any fields to it, I had to fig­ure out a mag­ic way of mov­ing them around. So it was a fair­ly sim­ple idea, but the prob­lem was that there had to be only one way to get from any place to any oth­er place, or else pack­ets would just kind of move around and mul­ti­ply and it would be a dis​as​ter​.So that’s why the span­ning tree algo­rithm, where span­ning means ​“reach­es every­body,” tree means ​“no loops.” 

So the sto­ry of invent­ing it was kind of fun­ny. Which was my man­ag­er asked me to design this on a Friday, and he was going to be gonna vaca­tion the whole next week. So that night I real­ized oh my good­ness, it’s real­ly sim­ple. You know, with no con­fig­u­ra­tion what­so­ev­er it just all works, and I could prove that it worked. So Monday and Tuesday of next week when my man­ag­er was gone, I wrote the spec. And I did it in enough detail that the imple­menters got it work­ing in just a cou­ple of months with­out ask­ing me a sin­gle ques­tion. But then I had three more days to the week when my man­ag­er was still gone, and this was before peo­ple would send email or cell phones or any­thing. So I could­n’t con­cen­trate on any­thing else because I was so excited. 

So I spent the remain­der of the week work­ing on the poem that goes along with the algo­rithm. And it’s the abstract of the paper in which I pub­lished it. So the poem is called the ​“Algorhyme,” because every algo­rithm should have an algo­rhym. And the poem is

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.
An algo­rithm for dis­trib­uted com­pu­ta­tion of a span­ningtree in an extend­ed LAN

So anoth­er con­tri­bu­tion that I think that I’ve made is the books that I’ve writ­ten. Where most books are just telling you the exact details of what’s cur­rent­ly deployed, as if stu­dents should just mem­o­rize that but it does­n’t teach you to think crit­i­cal­ly at all, and it’s full of acronyms and mar­ket­ing FUD and so it’s hard to read but not tech­ni­cal­ly deep, it’s sort of very super­fi­cial, mine are quite the oppo­site. They’re easy to read but thought-provoking. And I don’t just say ​“Here’s all of the details of the one thing that’s deployed,” I say ​“Here’s a con­cep­tu­al prob­lem. Here’s sev­en dif­fer­ent ways that it could’ve been done. Here are the pros and cons.” And then I’ll say, ​“And by the way IP did this, AppleTalk did this, IPX did this.” 

And some pro­fes­sors, accord­ing to the pub­lish­er, say ​“Why is this book telling my stu­dents stuff that they don’t need to know?” Because no recruiter is going to ask you whether you know AppleTalk. As if stu­dents’ brains are very very tiny and if you fill them with any knowl­edge that you don’t need to know, then oth­er stuff won’t fit. But it actu­al­ly empow­ers them to be able to see oth­er ways of doing things. 

But at any rate. So I wrote this— Oh. Before that, even though I did real­ly impor­tant things, it was kind of the stereo­typ­i­cal thing that at a meet­ing peo­ple would not hear what I said until some­one told tall and pompous said it. So unfor­tu­nate­ly you know, relent­less­ly self-promoting peo­ple do real­ly well, and oth­er people…you know, don’t get rec­og­nized. And that would’ve been the case for me had I not writ­ten that book. 

So I wrote the book and it became kind of the book at exact­ly the right time. And that changed my pro­fes­sion­al life, because I did­n’t have to act all pompous and sneer­ing and con­de­scend­ing in order for peo­ple to take me seri­ous­ly. It would still be the same thing that they’d be intro­duced to me and just take one look at me and just sort of yawn. It was like ​“Yeah yeah.” But then they’d hear my name, and I was like ​“Oh! I learned the field from your book.” So that was real­ly cool.

But the fun­ny sto­ry about it was that a cou­ple years after it was pub­lished, I had a four-hour lay­over in a Chicago air­port. And I was just so tired, and I did­n’t know what I was going to do for four hours. So I was just wan­der­ing around in a daze. And for some rea­son the air­port was almost desert­ed. I passed by this group of like five men sit­ting togeth­er and I thought I heard some of the right words, like ​“bridges” and ​“routers.” But I was­n’t sure, because I was­n’t quite close enough. And one of them had a book on his lap that all I could see was the edges because there were papers on top of it. 

So, with­out think­ing I just decid­ed in this emp­ty air­port to maneu­ver myself to sit right next to them. At which point they stopped talk­ing and they stared at me. And I real­ized oh, I’m act­ing bizarre. This is embar­rass­ing. But then I said to them, ​“Oh I’m just curi­ous, what is that book?” So he pulled out the book and it was my book. It was Interconnections. So I said, ​“Oh! I’m Radia Perlman.” And they all turned com­plete­ly white and said ​“No!” And then when one of them final­ly kind of recov­ered well enough to talk, he said ​“We are in a pan­ic try­ing to pre­pare a cus­tomer pre­sen­ta­tion. And we don’t know what we’re doing. And right before you showed up, one of us said ​‘If only the author of that book were here.’ ”

And I said, ​“Oh, it’s not a prob­lem. It comes with the book. You wish for me, I appear. How can I help?” So I helped them with the pre­sen­ta­tion, I signed their book, and I nev­er had a bet­ter time at an airport.

Intertitle: Describe the state of the Internet today with a weath­er anal­o­gy and explain why.

Perlman: Yeah, that’s a very good ques­tion. It’s…excitingly won­der­ful, and excit­ing­ly ter­ri­fy­ing at the same time. So, I’m not quite sure what kind of weath­er that sig­ni­fies. But it’s trans­form­ing soci­ety. The fact that you can buy things from all over the world. The fact that some­one with an inno­v­a­tive prod­uct does­n’t have to do mil­lions of dol­lars of mar­ket­ing, or have a store­front where lots of peo­ple can reach them is amaz­ing. The oppor­tu­ni­ties for bring­ing edu­ca­tion and knowl­edge of the out­side world to remote places is unbe­liev­ably excit­ing as well. 

But there are real­ly ter­ri­fy­ing things, which is all of the scams that hap­pened, just…hundreds of them every day that you see. And the fact that there’s still peo­ple get­ting tak­en in by this is real­ly kind of aston­ish­ing. There’s just the annoy­ing in-your-face push­ing adver­tis­ing at you. Like mak­ing you watch videos before you can watch the video that you want. Not ever doing things in writ­ten form, so if you’re just try­ing to qui­et­ly read some news, your machine sud­den­ly blares some ads for things. 

There’s misinfor­ma­tion as well that gets prop­a­gat­ed. So, how do you know whether any­thing’s true or not. There’s no over­head what­so­ev­er to post­ing things. So a lot of peo­ple think that soci­ety is get­ting so much better-informed because there’s so much data on the Internet, but it actu­al­ly can be just the oppo­site. Because you can choose what you want to look at. And so what­ev­er your bizarre views are, you can find fifty peo­ple across the world that believe the same views. And if you only read the things that this lit­tle com­mu­ni­ty posts, it winds up with peo­ple get­ting less-informed and soci­ety get­ting more polar­ized. And that’s very scary.

Intertitle: What are your great­est hopes and fears for the future of the Internet?

Perlman: One of the con­cerns is that pri­va­cy is just absolute­ly gone. So we can blame the younger gen­er­a­tion for post­ing stuff on Facebook with­out any notion of pri­va­cy. But that’s not real­ly the prob­lem. Because even if they did­n’t, all of this infor­ma­tion is har­vestable by stuff on the Internet. Everything’s on the Internet. 

There used to be a sep­a­rate phone net­work, and tele­phone calls would work. And these days since even if it’s not a cell phone a lot of the links are going to be over the Internet, and we just are accept­ing the fact that phone calls are going to be of unac­cept­able qual­i­ty a lot of the time. And this is real­ly unfortunate. 

But yeah, in a soci­ety where you can’t hide, no matter…every trans­ac­tion that you do, some­body can fig­ure out where you are, is extreme­ly scary. So with a fair­ly benev­o­lent gov­ern­ment, it’s not so bad. But if the gov­ern­ment decid­ed to do some sort of geno­cide and hunt down every­body of a—it would be extreme­ly dif­fi­cult to do any sort of resis­tance or hid­ing with basi­cal­ly every­thing that you do being mir­rored and acces­si­ble some­how over the Internet.

Intertitle: What action should be tak­en to ensure the best pos­si­ble future?

Perlman: I’m not sure I know. Because it’s so won­der­ful­ly con­ve­nient to have every­thing con­nect­ed, and every­thing acces­si­ble. To be able to pay your tax­es online. To be able to vote online. To be able to shop online. All of these things are won­der­ful. But it also leads to the com­plete lack of any abil­i­ty to have pri­va­cy. And the abil­i­ty for any­one to post any infor­ma­tion is also incred­i­bly won­der­ful. But how do you fil­ter out cor­rect infor­ma­tion from incor­rect infor­ma­tion. And I’m not sure that I have any answers that can help either of these things.