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.