Heidelberg Lecture: The Origins and Evolution of the Internet
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00:00
Turing testNeuroinformatikMoment (mathematics)PlastikkarteMultiplication signScaling (geometry)Lecture/Conference
00:48
InternetworkingTime evolutionARPANETComputer networkControl flowComputerMobile WebSatelliteSoftwarePressureOpticsInternetworkingARPANETPhysical systemComputer scienceComputer networkMereologyArtificial neural networkProjective planeLecture/Conference
01:31
ARPANETComputer networkComputerControl flowMobile WebSatelliteSoftwareComputer scienceArtificial neural networkNeuroinformatikSoftwareCycle (graph theory)Bit rateARPANETLecture/ConferenceMeeting/Interview
02:15
ARPANETComputer networkControl flowComputerMobile WebSatelliteSoftwarePlastikkarteBit rateARPANETGame controllerNeuroinformatikArithmetic progressionGroup actionQuicksortCASE <Informatik>Moment (mathematics)Mobile WebInstallation artBinary multiplierInternetworkingLecture/Conference
03:18
PlastikkarteInternetworkingServer (computing)Physical systemArithmetic meanLink (knot theory)WeightSoftwareCartesian coordinate systemSatelliteNeuroinformatikLecture/ConferenceMeeting/Interview
04:22
PlastikkarteARPANETCartesian coordinate systemSoftwareNumberCuboidPlastikkarteOrder (biology)Workstation <Musikinstrument>Different (Kate Ryan album)Physical systemARPANETImplementationMultiplication signStudent's t-testNeuroinformatik19 (number)Lecture/ConferenceComputer animation
05:26
Limit (category theory)Router (computing)ARPANETRouter (computing)Multiplication signKälteerzeugungMessage passingCoprocessorInterface (computing)State observerFrequencyTwitterInternetworking40 (number)Lecture/ConferenceComputer animation
06:16
Mobile WebTwitterSoftwareAdditionAreaThomas BayesARPANETStorage area networkBitVery-high-bit-rate digital subscriber lineFrequencyVideoconferencingPhysical systemBit rateOperator (mathematics)Cylinder (geometry)Order (biology)Endliche ModelltheorieValue-added networkSampling (statistics)2 (number)TrailSpeech synthesisWeightInformationDiameterMultiplication signStreaming mediaQuicksortParameter (computer programming)Right anglePentagonSelf-organizationKey (cryptography)Form (programming)Game controllerCubic graphLecture/Conference
09:38
Mobile WebSatellitePhysical systemWorkstation <Musikinstrument>Value-added networkTwitterSatelliteDifferent (Kate Ryan album)Physical systemAdditionSoftwareBit rateChannel capacityError messageAreaMultiplicationARPANETStandard deviationLecture/Conference
10:40
InternetworkingSatelliteIterationOperations researchPhysical systemARPANETBayesian networkError messageARPANETSoftwareConstructor (object-oriented programming)Task (computing)FrequencyImplementationMultiplicationCommunications protocolIterationInternetworkingNumberMultiplication signRevision controlLecture/ConferenceComputer animation
11:51
Revision controlPhysical systemCommunications protocolInternetworkingComputer programmingOperating systemOrder (biology)Point (geometry)Link (knot theory)PhysicalismLecture/ConferenceMeeting/Interview
12:39
Computer networkInternetworkingUDP <Protokoll>File Transfer ProtocolData integrityLink (knot theory)ÜberlastkontrolleRouter (computing)AnwendungsschichtLink (knot theory)InternetworkingOSI modelSoftwarePhysicalismIntegrated development environmentCartesian coordinate systemTelecommunicationCommunications protocolComputer architectureWeightProcess (computing)BitSystem callComputer animationLecture/Conference
13:29
Router (computing)Computer networkLink (knot theory)AnwendungsschichtInternetworkingNetzwerkschichtVideoconferencingEmailCommunications protocolWeb pageNumberCommunications protocolCartesian coordinate systemWeightOSI modelInternetworkingDirection (geometry)Process (computing)Internet service providerNumberRouter (computing)Data transmissionOrder (biology)Dependent and independent variablesPhysical systemFrequencyMultiplication signTable (information)CASE <Informatik>Web pageWeb serviceOffice suiteDecision theoryUniverse (mathematics)Data recoveryPlastikkarteMechanism designGoogolComputer architecturePhysical lawLecture/ConferenceMeeting/Interview
17:01
CuboidInternetworkingOffice suiteWeb pageGame controllerCASE <Informatik>Domain nameFitness functionPhysical systemMechanism designData recoveryMultiplication signCoefficient of determinationBitDataflowLecture/Conference
17:49
Address spaceDNS <Internet>Domain nameWeb browserChi-squared distributionUniform resource locatorInternetworkingDomain nameOrder (biology)Cartesian coordinate systemNeuroinformatikEmailWeb browserIP addressNumeral (linguistics)HierarchyWeb serviceGoogolCommunications protocolMereologySoftwareType theoryServer (computing)Address spaceSoftware maintenanceComa BerenicesWebsiteLecture/Conference
18:41
Address spaceWeb browserDNS <Internet>Domain nameSoftware testingInternetworkingComputer networkInternetworkingSoftware maintenanceCommunications protocolOrder (biology)Domain nameNumberPhysical systemAlgorithmConnectivity (graph theory)MultiplicationPairwise comparisonDifferent (Kate Ryan album)Mobile WebPoint (geometry)SoftwareWeightMultiplication signGateway (telecommunications)Type theorySoftware testingValue-added networkSatelliteThomas BayesCuboidARPANETAreaLink (knot theory)Router (computing)SynchronizationLecture/ConferenceComputer animation
19:47
ARPANETGateway (telecommunications)Link (knot theory)SatelliteSoftwareMobile WebSynchronizationValue-added networkLine (geometry)Bit ratePhysical lawInformationLevel (video gaming)Meeting/InterviewSource code
20:30
InternetworkingSoftware testingComputer networkDesign of experimentsWeightSatelliteLevel (video gaming)SynchronizationSoftwareInternetworkingARPANET19 (number)Physical systemComputer programmingUniverse (mathematics)QuicksortMultiplication signCollisionDependent and independent variablesMeeting/InterviewSource codeComputer animationLecture/Conference
21:49
ARPANETComputer networkPressureDesign of experimentsWeightInternetworkingPhysical systemSynchronizationSatelliteWeightArithmetic meanSoftwareUniverse (mathematics)InternetworkingPower (physics)Communications protocol2 (number)Level (video gaming)Software developerFood energyElement (mathematics)Computer animationLecture/Conference
22:49
Computer networkDesign of experimentsWeightInternetworkingPower (physics)Flow separationSoftwarePhysical systemWeightRight angleSurfaceExecution unitMeeting/InterviewComputer animationLecture/Conference
23:33
Hill differential equationComputer networkDesign of experimentsWeightInternetworkingPhotographic mosaicBit rateHTMLHypertextTransportprotokollInternetworkingSoftwarePhysical systemGraph coloringHypertextCommunications protocolWeb 2.0ImplementationResultantCondition numberWeb browserBerners-Lee, TimMarkup languageComputer hardwareServer (computing)Autonomous system (mathematics)Cartesian coordinate systemGraphical user interface19 (number)Term (mathematics)Medical imagingFormal languageSupercomputerMultiplication signLecture/ConferenceComputer animation
25:24
Communications protocolPhotographic mosaicBit rateMarkup languageVideoconferencingInteractive televisionMathematicsInternetworkingBusiness modelOSI modelNumberBoom (sailing)Multiplication signLecture/Conference
26:37
Photographic mosaicBoom (sailing)Bit rateInternetworkingHTMLTransportprotokollHypertextDomain nameDNS <Internet>Information securityAddress spaceImage registration1 (number)Physical systemInternetworkingDifferent (Kate Ryan album)Point (geometry)Communications protocolSoftwareNeuroinformatikCartesian coordinate systemProgrammer (hardware)Radical (chemistry)Power (physics)ARPANETBitScaling (geometry)Multiplication signGoogolAddress spaceLecture/ConferenceComputer animation
28:07
Parallel portInternetworkingDomain nameInformation securityDNS <Internet>Image registrationAddress spaceDecision theoryBitNeuroinformatikAddress spaceMultiplication signRevision controlPoint (geometry)Level (video gaming)Radical (chemistry)Information securityIn-System-ProgrammierungInternetworkingSpacetimeCommunications protocolMobile WebProduct (business)Domain nameSoftwareScaling (geometry)Generic programmingNumberInternet der DingePhysical systemFormal languageForm (programming)Cartesian coordinate systemMechanism designSign (mathematics)Dressing (medical)Dot productMathematicsExecution unitCodeWeb serviceIntegrated development environmentComa BerenicesWeb 2.0Lecture/Conference
31:01
InternetworkingAuthenticationTransport Layer SecurityCryptographyMobile WebPlastikkarteAuthenticationPhysical systemDomain nameTransport Layer SecurityCryptographyPasswordElectronic mailing listElectric generatorAdditionMobile WebSoftwareInformation securityGoogolInternet der DingeDivisorSmartphoneIntegrated development environmentMereologyGame controllerInternetworkingMultiplication signMoore's lawWeb servicePoint (geometry)KälteerzeugungUtility softwareFrame problemMobile appProcess (computing)Lecture/ConferenceMeeting/Interview
33:09
InternetworkingFrame problemKälteerzeugungInternetworkingIP addressFamilyGraph coloringBlogEmailSystem callWebsiteElectronic mailing listRadio-frequency identificationLecture/ConferenceMeeting/Interview
34:13
InternetworkingElectronic visual displayElectronic mailing listSystem callKälteerzeugungEmailRow (database)WeightFamilyMereologyMachine visionInformationScaling (geometry)InternetworkingArtificial neural networkPoint (geometry)NeuroinformatikLimit (category theory)SoftwareRevision controlGoogolContext awarenessData conversionEndliche ModelltheorieArithmetic meanResultantPointer (computer programming)Right angleLecture/ConferenceMeeting/InterviewComputer animation
36:23
InternetworkingHecke operatorElectronic program guideMaxima and minimaMach's principleElectronic data interchangeFood energyServer (computing)SoftwareLaptopWaveInternetworkingWater vaporProduct (business)Server (computing)InformationDegree (graph theory)Row (database)Goodness of fitMessage passingLevel (video gaming)Self-organizationRouter (computing)Mobile WebPoint (geometry)Physical systemCASE <Informatik>Computer animationLecture/Conference
38:06
Physical systemMessage passingAuthenticationRadio-frequency identificationLecture/Conference
38:58
Software bugSampling (statistics)BuildingDifferent (Kate Ryan album)Physical systemDegree (graph theory)Lecture/Conference
39:45
Point cloudMobile WebLaptopInternetworkingSoftwareBuildingPhysical systemInformationMereologyWeightNumberMultiplication signAddress spaceOrder (biology)Level (video gaming)Sampling (statistics)Type theoryFunctional (mathematics)BlogAnalytic continuationGoogolLecture/Conference
41:38
GoogolData modelAnalytic continuationSampling (statistics)Bit rateSoftware bugEndliche ModelltheorieVideoconferencingProduct (business)Different (Kate Ryan album)Device driverLecture/ConferenceComputer animation
42:23
Software testingVideoconferencingLecture/ConferenceComputer animation
43:07
GoogolSign (mathematics)RadarRow (database)TrailRadarMetropolitan area networkRight angleOrder (biology)Window
43:50
Machine visionSoftware testingMachine visionVideo gameMultiplication signLecture/Conference
44:34
Independence (probability theory)Hill differential equationVideo gameIndependence (probability theory)Sound effectRight angle
45:20
Text editorData modelGoogolSoftware developerEndliche ModelltheorieObject-oriented programmingLecture/ConferenceComputer animation
46:11
InternetworkingTime evolutionComputer networkNetzwerkschichtCommunications protocolSoftware testingPhotographic mosaicInternet der DingeMessage passingMedical imagingMereology2 (number)Projective planeRule of inferenceComputer animation
47:05
GoogolAerodynamicsMereologyProjective planeInternet der DingeEvoluteInternetworkingFiber (mathematics)TelecommunicationDirection (geometry)Operator (mathematics)RoboticsWeb serviceCoefficient of determinationDynamical systemTerm (mathematics)Taylor seriesPoint (geometry)Lecture/ConferenceComputer animation
48:17
AerodynamicsCoefficient of determinationGoogolComputer animation
49:04
AerodynamicsStability theoryDisk read-and-write headCoefficient of determination
49:50
AerodynamicsCASE <Informatik>YouTubeRoboticsVideoconferencingCoefficient of determinationProjective planeGoogolBitComputer animation
50:54
AerodynamicsInternetworkingProjective planeBitImplementationRing (mathematics)RoboticsInternetworkingMultiplication signCommunications protocolTelecommunicationSoftwareNetwork topologyLink (knot theory)Series (mathematics)Integrated development environmentDirection (geometry)Game controllerQuicksortRoundness (object)Prime idealPoint (geometry)Dataflow40 (number)Lecture/ConferenceComputer animation
52:34
ExpressionDataflowGame controllerSurfaceOrbitPlanning2 (number)Bit rateMetreSpacetimeOrder (biology)SoftwareLecture/ConferenceComputer animation
53:59
Wage labourExpressionSpacetimeOrbitData storage deviceSurfaceSuite (music)Communications protocolConfiguration spaceFiber bundleSet (mathematics)Pole (complex analysis)PrototypePhysical systemDistanceReal numberImplementationReal-time operating systemFreewareInformation technology consultingMultiplication signSource codeUniverse (mathematics)Lecture/ConferenceComputer animationMeeting/Interview
55:29
Wage labourExpressionWhiteboardSource codeUniverse (mathematics)FreewareSpacetimeMultiplication signUltraviolet photoelectron spectroscopyInternetworkingComputer animationLecture/ConferenceMeeting/Interview
56:14
Hill differential equationComputer animationLecture/Conference
Transcript: English(auto-generated)
00:17
Thank you very much.
00:21
Well, I can see already I have to convince the computer that it's me. So one moment. There we are. So first of all, you have no idea what this is like, I think. Well, some of you have been up here before. But for me, this is very daunting.
00:41
I've never had this many Nobel Prize winners and smart people in the audience at the same time in this scale. So I hope I do reasonably well. Stefan held in an absolutely spectacular lecture on optical microscopy last year at the Heidelberg Laureate Forum, so I'm feeling a certain amount of pressure.
01:03
So let me start by saying I'm going to try to cover some of the history of the internet just to give you a sense for how it came about and then some ideas about where it's going in the future. So let's start out by reminding you that there was a predecessor system called the ARPANET.
01:22
The Defense Advanced Research Projects Agency, which is part of our Department of Defense in the US, began to explore the possibilities of computer networking. And it had a very practical reason for doing it. It was funding a dozen computer science departments during the 1960s to do research
01:41
in artificial intelligence and computer science. And everybody kept asking for the latest computing equipment every year. And they said we can't buy 12 new computers for 12 computer science departments every year. So we're going to build a network and you're going to have to share your resources. And people were reluctant to do that initially because they thought, well, if we have to share
02:01
resources, the other people will see our work and they'll steal our software or steal our code or use up all the cycles. And ARPANET said, just relax. We're funding all of you. This is no longer a competitive issue. We want you to share your experiences and your expertise so that we can accelerate the rate at which the research progresses.
02:21
So they built the ARPANET and it was successful. Then they realized after the success of the ARPANET that computers might be useful for command and control because if you could manage your resources better than an opponent owing to the use of computers, you might actually be able to defeat a larger opponent
02:42
with a smaller size group because you were managing to extend their capability better. We called that a force multiplier. But if that were going to be the case, then the computers would wind up having to be in aircraft and ships at sea and mobile vehicles. And at the moment, at that moment, only fixed installations had been built for the ARPANET.
03:03
So that's sort of the background for why the Defense Department, ARPA in particular, was interested in pursuing this. So this is all based on the concept of packet switching. And you're all using it, whether you know that or not. But some people don't fully appreciate how it works. And it's actually very simple.
03:21
If you know how postcards work, you know how the basic internet packets work as well. First of all, just like a postcard, they have no idea how they're being carried. The postcard doesn't know if it's going over in an airplane or a ship at sea or on the back of a postman or a bicycle. And the internet packets don't know how they're being carried. They don't know whether it's an optical fiber or a satellite link
03:43
or a radio channel or a hardwire Ethernet. And they don't care. The design of the system was carefully done to make sure that these internet packets were unaware of how they were being transported. Also, like a postcard, the internet packets don't know what's written on them.
04:01
So that turned out to be a very powerful tool because the meaning of the internet packets is only interpreted at the edges of the net by the computers that are either sending or receiving them. What that means is that when you develop a new application, you only have to change the software at the edges of the net
04:21
where the host computers are. You don't have to change the network because the network doesn't care what the application is, which opens up a huge number of possibilities when you want to invent a new application. You don't have to change all of the network. Postcards don't stay in order either. You put two postcards into the postbox and they'll, if they come out at all, they might come
04:41
out in a different order. And in fact, sometimes they don't all come out. And so you have this disorderly, not reliable system of postcard, electronic postcards, and that's the basic packet switching. So you might wonder how would anybody make anything useful out of that, and I hope I'll show you how that can work.
05:01
The original, initial implementation of the ARPANET had four nodes. I was at UCLA at the time as a graduate student, like many of you are, and wrote the software to connect the Sigma 7 computer to the first packet switch of the ARPANET in about 1969. The Sigma 7 is in a museum now somewhere
05:22
and some people think I should be there too, but I'm here. So that's the beginning, just a four-node network. It rapidly grew over time. What you see on the left is what a packet switch looked like. IMP stood for Interface Message Processor. We call them packet switches now, or routers.
05:41
This was the size of a refrigerator at the time, and you can tell that things have changed over the intervening 40 years or so. You can hold a router in your hand now. It's about the size of a simple Ethernet connector. And of course, it cost a lot less. These were $100,000 devices back in the day.
06:01
So that's how things have changed over a 40-year period. This, by the way, is a classic observation. Usually anything that you do that's new is big and expensive, and with experience over time, if it continues to work, it gets less and less expensive and often a lot smaller. And so you see this trend from expensive equipment that's owned
06:21
by institutions to maybe just departments and then eventually individuals who own these devices and carry them around. We were also concerned, of course, about mobile communication. And so we built a packet radio network in addition to the original ARPANET. This ran in the San Francisco Bay Area.
06:41
We had repeaters up in the mountaintops. And this particular nondescript van that was carrying equipment inside, which I can show you here, if you see, I guess I can point to them here, these things over here and over here are packet radios. They're about a cubic foot in size.
07:00
They cost $50,000 each back around 1975. And they were the sorts of things that you stick in your pockets now. But back then, the equipment was not quite as dense. We were able to get something on the order of 100 to 400 kilobits a second operating at 1710 to 1850 megahertz.
07:23
And we were modulating this stuff at fairly high speeds. So one of the things that we tried to do in addition to transmitting this data around, we recognized that, for command and control, we need voice and video. And so back in the 1970s, we were experimenting with packetized voice and packetized video.
07:44
Now, I have to tell you that the voice experiments were kind of interesting because a typical voice channel is 64,000 bits a second. You sample the voice stream at 8,000 times a second, taking 8 bits of information per second, or per sample. And we only had 50 kilobits per second available
08:03
in the ARPANET backbone and 100 kilobits in the packet radio net. So we decided in order to get more voice channels in the system, we would compress the voice down to 1,800 bits per second. And in order to do that, we modeled the voice track as a stack of 10 cylinders
08:20
that would change their diameters as the voice speech was being generated. And that little stack of cylinders was excited by a pitch, or form, and frequency. We sent the parameters, the diameters of all of those model cylinders, over to the other side. And that got the data rate down to 1,800 bits a second.
08:42
Although, you can imagine that the quality of the speech kind of reduced some when you went from 64 kilobits down to 1,800. So anyone who spoke through the system sounded like a drunken Norwegian. And I hope I haven't insulted any Norwegians in the audience. So the day came, but they were understandable,
09:01
but it was a very peculiar kind of sound. So the day came when I was, by this time, working in the Defense Department, and I had to demonstrate this system to some generals at the Pentagon, and I remember thinking, okay, how am I going to do this? And then I remembered that one of my colleagues who was working on the packet voice was Ingvar Lund from the Norwegian Defense Research Establishment.
09:23
So we had Ingvar speak first through the ordinary voice switch system, and then we had him speak through our packet voice system, and it sounded exactly the same. We didn't tell the generals that everybody would sound that way through the system. Well, as you can see on the right-hand side, that we've gone from these big, bulky pieces of equipment
09:42
that required a huge van to carry around, to things that we put in our pockets or even strapped to our wrists. And once again, this trend of going from big and expensive to small, portable, and often affordable by an individual is still holding true. There, in addition now, because we also wanted to deal
10:02
with ships at sea, we decided that satellites would be the appropriate technology because you could go long distances. So we put a packet satellite, well, we put a satellite, standard satellite system, Intelsat 4A, or used it, we leased some capacity on that network.
10:21
And we had multiple ground stations all contending for the same satellite channel, so it was kind of like an ethernet in the sky. And that allowed us to experiment with wide-area packet switching over a satellite channel. So we now had three different kinds of networks to deal with, packet radio, packet satellite, and the ARPANET.
10:40
And they all operated at different speeds. They had different error rates. They had different packet sizes. And yet, the problem that Bob Kahn and I had to solve was how do we make all of those diverse networks appear to be one network, even though they were all very distinct. So just to give you a sense for the course of this effort,
11:02
in 1969, the ARPANET begins construction. And then in 73, 74, after having about three or four years of experience with the ARPANET, Bob Kahn and I did the first design of the TCP protocol, which later became TCPIP.
11:20
And then during the 1975 to 78 period, we went through multiple iterations of implementation, test, and refining, and correcting of the protocols. And we found a number of mistakes that we had not anticipated. We had many different institutions working with us at the same time. And so if someone tells you
11:40
that the internet is purely an American invention, that's incorrect. We had colleagues from everywhere, people in Europe, people in Asia, some in my lab at Stanford before I came to ARPA and elsewhere. So there was a lot going on. And then finally, after we settled on the versions that you're mostly using today, you're using,
12:02
roughly speaking, the 1978 internet design, we began implementing those protocols on every operating system that we could find so that in 1982, we could announce to everyone who was on all of the systems that they would have to switch over to the new TCP protocols in order
12:20
to stay in the program. So on January 1, 1983, we turned the internet on, and it has been running since 1983, although it wasn't widely visible to anyone except the research community and the military. Now, just to give you another important point about the design of the system, it's layered.
12:40
So the lowest layers are, you know, physical transport over optical fiber or radio links and things like that. The internet protocol layer is the electronic postcards, and those are the things that are forwarded through the network and go back and forth between the hosts. Above that layer are the protocols that make this a more disciplined environment,
13:01
and finally, protocols that implement applications. So this is a layered architecture, and it's roughly one, two, three, four, five layers, if you like, physical layer, the data links, the discipline, the bits, and then finally the IP layer and transport and application.
13:21
So the way it physically works is that the hosts at the edge of the net implement all of the layers of protocol up to and including the application layer, but you'll notice that the things in the middle of the net that are responsible for switching internet packets don't know anything about transport layer protocols or application protocols.
13:42
All they see are internet packets, those little electronic postcards, and so their job is very simple. When they get a postcard, they look at it to see where it's supposed to go. They look in a table, which is generated by a routing protocol running in the background, and they just send it in whichever direction that table tells them to go.
14:00
And so it's a very simple concept, and the simplicity, I think, has helped make this a system which is not only scaled over time, but it's persisted over a 30-plus-year period. So this is another picture of the layered protocol architecture, and what's important is the little guy in the middle called the internet protocol. The thing which I want to emphasize in this picture is
14:23
that because the internet protocol layer doesn't care how the underlying layers work, the assumption is if you hand the underlying layers a packet that they will somehow pass along that channel, and they go from router to router to router to the destination host.
14:41
The consequence of that decision is that every time a new communication protocol came along or a new transmission technology came along, we just swept it into the internet. The internet didn't care, didn't notice it was anything new. It was just another way of carrying bits. By the same token, the absence of knowledge of the applications in the internet protocol meant
15:01
that when somebody wanted to invent a new application, they didn't have to go get permission from every internet service provider in the world. All they had to do was to go implement it at the edges of the net and proceed to send packets back and forth. So Larry and Sergey, when they started Google in their dorm room at Stanford University, did not have to negotiate with every internet service provider in the world.
15:22
They just put the service up on the net and let people try it out. That's why we've had such a cornucopia of applications coming out of the internet, despite the fact that there are literally hundreds of thousands of internet service providers all around the world. So in order to make the internet protocol layer more
15:40
disciplined, remember it's lossy, it loses things, it gets them out of order and everything else, we put another layer of protocol on the top called TCP. And you can understand very easily how it works if you imagine the problem of sending someone a book through a post office that only carries postcards. So imagine, what would you do?
16:01
Well, the first problem is you have to cut the pages up to get them to fit on the postcard. Then you'd notice that the post, not all the postcards have page numbers on them because you cut the pages up, and you know they're going to get out of order, and so you number every postcard, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. And you also know that some of the postcards are going to get lost, so you hang on to copies in case you have to retransmit them.
16:23
And then you figure, you want to know, well, how do I know when to stop sending, or how do I know when to keep, throw away the copies you've kept because, you know, the guy on the other end has received them. And you get this brilliant idea, you have the guy at the other end send you a postcard saying, I've got everything up to, you know, postcard number 420.
16:44
And then you realize, that postcard might get lost. So now you decide, well, I guess I'll just look at my watch, and if I haven't gotten any responses back from the other guy, I'm going to start sending copies until I do get a postcard that says I got everything up to number 420. So that's the basic timeout retransmission
17:02
recovery mechanism. You can filter things out because you know which postcards you've got. If a duplicate shows up, you can ignore that. Then the only other thing to worry about is the case where you have 1,000 page book, and you cut it up into 2,000 postcards, and you take them to the post office, and you give them to the post office all at once, and by a miracle,
17:21
the post office tries to deliver all of them at the same time on the same day. And, you know, they don't fit in the post box at the destination, and some of them fall on the floor, and the dog eats them, or they get blown away by the wind. So you have an agreement with your friend that you won't send more than 200 at a time until you get a postcard back saying I got all
17:42
of those, you can send some more. That's called flow control. So now you know how the internet works. That's all there is to it. Well, I left out a little bit. There's these domain name systems. You know how when you type the URLs and things like that, in the middle are domain names like www.google.com. There's a whole hierarchical structure of servers
18:01
that are scattered throughout the internet that your browser essentially applies to, or your email application. It says I'm trying to send an email to someone at google.com, or I'm trying to go to google.com to do a search. You can't get there using the domain name. Your computer actually has to go and consult
18:21
with the domain name service and say what's the numerical IP address of the destination? So domain name lookups produce a numerical address which the TCP IP protocols use in order to send packets back and forth across the network. And so that turns out to be a very important part
18:41
of the network as well. So you have the basic transport stuff. You have the internet packets. You have the TCP protocol to maintain things in order and to recover from failures. And you have the domain name system to figure out where things are supposed to go, but it's easier to remember the domain name than it is the number. And finally, you have the routing algorithms.
19:00
And that's basically the components of the internet that make it work. So in 1977, I'm now at the Defense Department running the program, and I've been at it now since 1973 at that point. And I really, really wanted to be able to demonstrate that this stuff actually worked. We'd only done pairwise tests among the various nets.
19:22
And to be honest with you, if you take two packet networks and you're just trying to connect two of them together, you could probably build a box in between them and do some crazy thing and it would make it work. But I wanted to show that a standardized box, which we called a gateway at the time because we didn't know they were supposed to be called routers, would work
19:41
with multiple networks of different types. So we had the mobile packet radio network in the Bay Area with the van going up and down the Bayshore Freeway, radiating packets through the gateway into the ARPANET. By this time, the ARPANET had been extended by an internal synchronous satellite link all the way to Sweden and Norway and then down to London
20:01
by landline where there was another gateway that connected the extended ARPANET back across the packet satellite network over the Atlantic, back to the ARPANET in the U.S. into another gateway and then all across the ARPANET to USC Information Sciences Institute in Los Angeles.
20:21
Now, between the packet radio, the mobile packet radio van in Los Angeles is about 400 miles. But if you follow the path of the packet, it's gone 100,000 miles because it's gone up and down to a synchronous satellite level twice and then all across the Atlantic and the U.S. as well.
20:42
And it worked. And I remember jumping up and down saying, it works, it works. Like it couldn't possibly have worked. It's software and it's a miracle when software works. So I was pretty excited about that. So this is the most important demonstration in the 1977 period. And as I say, we standardized shortly thereafter.
21:02
So another kind of timeline which I wanted to share shows you some of the other participants in the growing internet program. The ARPANET comes in 69. The University of Hawaii did an AlohaNet system based on a shared radio channel in 1971.
21:20
And they called it Aloha because basically you transmitted whenever you wanted to. And if there was a collision and you didn't hear a response, you assumed there was a collision and you retransmitted. And you were careful not to retransmit at a fixed time later, otherwise you have continuous collision. So instead, what they did was to have a variable timeout
21:41
so that if you had a collision with someone, the next time you each retried, it would be at a different time. And so Aloha is sort of a very hang loose kind of network. The packet satellite system was based on that same idea using the synchronous satellite channel. A guy named Bob Metcalfe visited the Aloha facility
22:02
and decided that he could do the Aloha system on a piece of coaxial cable and he invented the ethernet at Xerox Park in 1973 at three megabits a second. That was fairly impressive. And of course, then we were going through all of our software development. We turned the internet on on January 1st, 1983.
22:22
The National Science Foundation in the U.S. decides maybe this packet switching idea would be good to connect all of the universities in the U.S. So they build the NSF Net Backbone to connect 3,000 universities around the United States, including some intermediate level networks. NASA and the Department of Energy also decided that they would adopt the TCP IP protocols replacing their
22:44
high performance, or high power HP Net. It was, what is it? It's high power and high, I can't, Stephen what the hell was that? It was the high, it doesn't matter. It was for doing experiments with high energy physics.
23:02
It happened that it was a high energy physics net. And so they replaced all of their networks with TCP IP. And then around 1989, I got permission to connect some commercial systems up to the government backbone. And in that year, several commercial networks got started, UU Net, PSI Net, and Surf Net.
23:20
There's a whole story behind Surf Net. I won't bother you with it right now, but I didn't build it. They just borrowed my name and stuck it on it. And they did ask permission. And I remember thinking, if they mess it up, will I be embarrassed? And then I thought, wait a minute, people name their kids after other people, and if the kids don't come out right, they don't blame the people they named them after.
23:40
So I said, go ahead, go ahead and do it, it's okay. And it actually worked out all right. So this is what the internet looks like now. It's this giant, big ball of hundreds of thousands of networks. The reason that I wanted to show you this is that the colors represent just different networks. We call them autonomous systems formally.
24:01
But the thing is, this is not a top-down system. And so the people that run pieces of the internet pick which hardware they want to use. They pick which software they want to use. They decide who they're going to connect to and on what terms and conditions. And it just all comes together almost organically which is what Bob Kahn and I hoped in the first place. We published our results in 1974 saying,
24:24
if you can build something that works this way and find someone to connect to, it should work. And so what happened is the network grew in a very organic way. It only works because everybody's using the same protocols even though their implementations might vary. So that's how the internet has grown up until now.
24:42
The World Wide Web is one of the most important applications of the network. And I want to distinguish between the two because some people get confused about that. The World Wide Web is what many of us use all the time. Tim Berners-Lee and Robert Keough at CERN built the first hypertext markup language
25:00
and hypertext protocol implementation of browsers and servers at CERN. And nobody noticed, to be quite honest. However, two guys did notice. They were at the National Center for Supercomputer Applications, Marc Andreessen and Eric Bina. They did what was called Mosaic, which was the first graphical user interface for a browser.
25:21
It made the internet or the World Wide Web look like a magazine. It had formatted text. It had images. Eventually it got video and audio and things like that. It was a very spectacular change in the interactions that people could have. And so a guy named Jim Clark who had built Silicon Graphics in the Silicon Valley saw this
25:42
and brought Marc Andreessen and others from NCSA to the West Coast. They started Netscape Communications around 1994. They had their initial public offering in 1995. The stock went through the roof. It was the most spectacular IPO in history. And that started the dot boom, which meant every venture capital company in the valley
26:02
and elsewhere would throw money at anything that looked like it had something to do with the internet. It didn't matter if they had a business model or anything else. There's a huge amount of money went in. And a lot of companies failed around April of 2000. That was called the dot bust. But what was interesting is I was tracking, you know, how big is the internet
26:21
and how much is it growing? And it was doubling every year for quite a long time, even through the dot bust because people had real use for the underlying internet even though a lot of companies failed because they didn't really have a realistic business model. Just to point out to you about economics 101. Don't spend any more money than you have.
26:42
That's point number one. And the second one is don't confuse capital for revenue. Revenue is continuous and capital runs out. When you run out of capital and you don't understand the difference, then you're not surprised or you are surprised that you've just gone bankrupt. So the system grew very, very rapidly in spite of the dot bust.
27:00
And of course, all of you are using it today for many different purposes, including much of your scientific research. The internet itself, even though it was designed 40 years ago, is not static, it has continued to evolve in many ways, especially new protocols and new applications. And now I have to confess to you that Bob Kahn and I did make
27:20
at least one fairly major mistake. Apart from little details in the protocol design, we were trying to figure out how many termination points we were going to need for this internet thing. And so remember, it's 1973 and we're, you know, writing our little design. And so we said, okay, how many networks will there be per country? Because we were already thinking global. And we just finished doing the ARPANET and it was not cheap to build that on a nationwide scale.
27:44
So we thought, well, maybe there'll be two networks per country because there should be some competition. And then we said, how many countries are there? And we didn't know and there wasn't any Google to ask. So we guessed at 128 because that's a power of two and that's what programmers thinking.
28:04
So two times 128 is 256 and that's 8 bits. And then we said, how many computers will there be per network? And we thought, oh, you know, let's go crazy, 16 million, that's another 24 bits. So that's 32 bits of address space that's required. And we're making this decision at a time when computers were great big expensive things.
28:21
They were in air conditioned rooms and they did not move around. So 16 million was pretty ambitious. And that actually worked okay. The 4.3 billion terminations of IP version 4, which is what you're currently using mostly, lasted until 2011. And then we ran out. And so fortunately, the engineers, including me, started to get panicky around 1992
28:46
when we started seeing ethernets all over everywhere. And so we developed a new version of protocol called IP version 6. And it has 128 bits of address space. I don't have to tell you, you can do the math, you know, 3.4 times 10 to the 38th addresses,
29:00
which is a number that's, you know, big enough for the, even the Congress would appreciate that number. So we ended up, oh, by the way, some of you would wonder what happened to IP version 5. That was a protocol that was designed to do streaming video and audio, but it didn't scale very well. So we abandoned that and the next number was 6. So IP version 6 is the production version of the network.
29:23
And that's what you should be using. And if your ISP is not providing you with IPv6 service, please pound on the table and say give me a date certain when I can have IPv6 addresses because I need them for the Internet of Things and the mobiles and everything else. So we were a bunch of Americans and we only spoke English anyway.
29:41
So all we had was ASCII characters for the domain names, but it was pointed out to us later that there are some languages that can't be expressed with ASCII characters. And we said, oh, yeah, we forgot about that. So we added Unicode, which is what's used in the World Wide Web, in the domain names. So now you can have domain names in Russian and Cyrillic and Arabic and Hebrew and so on.
30:01
The original generic top level domains were only, you know, seven, like .com, .net, .org, .edu, .mil, .gov and so on. But the Internet Corporation for Sign Names and Numbers decided to open up the generic top level domain space a couple of years ago and they got 2,000 applications for new generic top level domains, you know, like things like .travel and .corporation and so on.
30:28
So, oh, and they charged $185,000 each. So they got $350 million came in upon opening up the top level domain space. There are additional things which I don't have time to go into much except to say
30:41
that there were security risks in the system which had been designed in a very friendly environment, mostly engineers. We didn't want to ruin everybody else's stuff and so we weren't attacking anything. But once you release the Internet into the global community, there are bad guys are out there too. So we've been adding more mechanisms for defending against various forms of attack,
31:01
against the domain name system and against the routing system. So those are the last two on the list. We've also been pushing two-factor authentication especially at Google where you have to have a device that will generate a cryptographic password in addition to your username and password. So even if somebody guesses your username and password, they don't have the little gadget
31:21
that does the crypto password generation as well and so they can't penetrate the account. We've added transport layer security which encrypts the traffic on the TCP layer and that inhibits the ability of somebody to snoop on what you're sending through the network. And of course, mobile smartphones and the Internet of Things have become part of the environment.
31:41
Just a brief footnote on smartphones, the mobile phone was actually developed in 1973 by a guy named Marty Cooper working at Motorola. Bob Kahn and I didn't know about that. But in 1983, Marty Cooper turned on the first mobile phone service.
32:00
And of course, his phone was about this big. It weighed three and a half pounds and had a whip antenna on the top. And I called him up to ask some questions with one of his phones. And one question I asked him was how long does the battery last? And he said 20 minutes, but it's okay. You can't hold the phone up longer than that anyway.
32:21
So they've gotten better since then. But probably, and so we were, so we got launched at the same time. Mobile phones and the Internet started officially and formally in 1983. But they really didn't have anything to do with each other until 2007 when Steve Jobs came home with the iPhone. And at this point now, the phone is capable of interacting with the Internet.
32:43
And what's interesting about this, of course, is that the two systems mutually reinforce their utility. The mobile phone's apps use computer power on the Internet. The Internet is accessible from any mobile phone, any smartphone. And so the two made themselves more useful. And finally, of course, as time has gone on, people have started
33:03
to use software instead of mechanical, electromechanical devices for control. And that leads to the Internet of Things. Now I will confess to you that in 1973, it did not occur to me that someone would want to attach their refrigerator to the Internet or a picture frame
33:20
or even a, I used to tell jokes. You know, someday, every light bulb will have its own Internet address, ha, ha, ha, except now I can't tell those jokes anymore. Phillips makes one called Hue, which you control from your mobile, both the intensity and the color of the bulb through the Internet. So I did wonder, you know, what would you do with an Internet-enabled refrigerator?
33:44
And well, in America, the way we communicate in our families is to put paper and magnets up on the refrigerator door. So this improves things because now we can communicate with websites and blogs and email and things like that. But we also thought, well, what would happen if the refrigerator knew what it had inside?
34:01
I mean, what if everything had a little RFID chip on it and you could sense what was in the refrigerator? So when you're out at work or off at school or something, the refrigerator is surfing the Internet looking for recipes that it could make with what it has inside. So when you come home, you see a list of recipes on the display. That sounds pretty good, but a good engineer will always extrapolate
34:22
to see what other things might happen. So you can imagine that you're on vacation and you get an email. It's from your refrigerator, and it says the milk has been in there for three weeks, and it's going to crawl out on its own if you don't do something about it. Or maybe you're shopping and your mobile goes off. It's the refrigerator calling. It says don't forget the marinara sauce.
34:41
I have everything else I need for a spaghetti dinner. Now, I'm sorry to tell you that our Japanese friends have spoiled this idyllic vision of the future because they invented an Internet-enabled bathroom scale. And when you step on the scale, it figures out which family member you are based on your weight, and it sends that information to the doctor, and it becomes part of your medical record, which is probably okay except for one thing.
35:03
The refrigerator is on the same network. So when you come home, you see diet recipes coming up on the display. Or maybe it just refuses to open, you know, because it knows you're on a diet. Really bad.
35:22
So in the lower right, you see our version one Google Glass being modeled by Sergey Brin, co-founder of Google. The reason I put this up is, of course, for one thing, it's a computer-enabled, Internet-enabled device. But what's interesting about it is that it allowed the computers to see what you see and hear what you hear.
35:43
And that's an interesting experiment because the possibility that the computer could understand what it was seeing and hearing, which, again, is pushing some of the limits of artificial intelligence, might mean that the computer could become part of the conversation. And so while you are having a dialogue with your colleagues and trying to argue
36:00
over some particular design point or other speculation, you might be able to invoke the computer, which would have context as a result. So it's very much like Star Trek, you know, when Captain Kirk would say computer, and you would hear Maysle Roddenberry's voice floating down from the ceiling. So this is actually an important experiment, and we're in the middle of designing a new version of the Google Glass.
36:23
I left the guy in the middle for last, though. This is an Internet-enabled surfboard. I've not met this fellow, but I imagine him sitting on the water, you know, down here, waiting for the next wave, thinking, you know, if I put a laptop
36:40
in the surfboard, I could be surfing the Internet while I'm waiting for the next wave. So he put a laptop in the surfboard, and he put a Wi-Fi server back in the rescue shack, and now he sells this as a product. So what else is coming? Well, sensor networks are already with us. Some of you have them at home already.
37:01
Sometimes it's a security system. Sometimes it's heating, ventilation, and air conditioning. In my case, I have an IPv6 self-organizing radio network at home. Each room in the house has a sensor, which also doubles as a little router, radio router, and every five minutes, it's sampling temperature, humidity, and light levels in the house and records that information through the network
37:23
to a server down in my basement. I know only a geek would do this, but the whole idea is that at the end of the year, I now have good engineering information about how well the heating, ventilation, and air conditioning work so we can make adjustments instead of relying on anecdotal information. Now, one room in the house is the wine cellar,
37:41
and there are 2,000 bottles of wine in there. So I care a great deal about keeping the temperature below 60 degrees Fahrenheit and the humidity up, you know, above 30 or 40% to keep the quartz from drying out. So that room has been alarmed. If the temperature goes above 60 degrees Fahrenheit, I get an SMS on my mobile,
38:00
and at one point, my wife, Sigrid, and I were away from the house, and I got the message saying, your wine is warming up, and nobody was there to reset the cooling system. So every five minutes for three days, I kept getting a message saying your wine is getting warmer. So it got up to like 70 degrees or something, which is not the end of the world. It's not great. So I called the guys that made this system, and they said,
38:22
do you guys make remote actuators? And they said, yes. So, you know, I'm thinking I could remotely reset the cooler. And they said, do you do strong authentication? And they said, yes. And I said, good, because there's a 15-year-old next door, and I don't want him messing around with my heating and air conditioning system. So we installed that. And then I got to thinking, you know, I can tell if somebody went into the wine cellar
38:44
because I could see that the light went off and on, but I don't know what they did in there. So I thought, well, what can I do about that? And I said, aha, I put an RFID chip on each bottle, and then I will put an RFID detector in the wine cellar so I can do a remote inventory, no matter where I am,
39:00
to see if any bottles have left the cellar without my permission. So I'm boasting to one of my engineering friends about this brilliant design, and he says, you have a bug. I said, what do you mean I have a bug? And he says, well, you could go into the wine cellar and drink the wine and leave the bottle.
39:21
So now I have to put sensors in the cork. And as long as I'm going to do that, I might as well sample the esters, which, you know, tell you whether or not the wine's ready to drink. So before you open the bottle, you interrogate the cork. And if that's the bottle that got up to 75 or 80 degrees, that's the one you give to somebody that doesn't know the difference.
39:42
So this is actually, I mean, the future really is going to be heavy in sensor systems all around, whether the buildings will be instrumented, the cars will be instrumented, you know, manufacturing facilities, and even ourselves, our bodies will be instrumented as well. And that will all be part of this vast quantity of information flowing around in the network.
40:03
So if we look over the next 20 years' time, some of these are, of course, just guesses. But today we think there could be 10 to 15 billion devices that are capable of communicating on the net. They typically are not all on at once necessarily, but there could be that many. And in 2036, 20 years from now, the numbers could reach a trillion.
40:23
I mean, there will be on the order of maybe 8.5 billion people in the world in 2036, and they might have anywhere from 100 to 110 devices either on their persons or at home or in the other places that they inhabit.
40:40
So these numbers are not totally crazy, but they do certainly motivate the need to get to IPv6 because we need all that address space for all these devices. Here are some of the things that we're experimenting with at Google. Our Verily company is experimenting with, it's not manufacturing, but it's experimenting with a contact lens
41:01
which can sense the glucose level in the tears of your eyes. That's related to the glucose level in your blood, although there's a delay function associated with going from blood glucose to the tears of your eyes. The idea is that if you're a type 1 diabetic and you're tired of pricking your finger to take blood samples all the time, this is an alternative way of gathering the data.
41:24
And since it's a potentially continuous monitoring system, we can establish a baseline of what is normal for you, and then excursions away from the baseline can be detected very quickly, and so you can recover either by adding more insulin or taking, eating something with sugar in it.
41:40
So this idea of continuous monitoring I think is a very important theme which you will see repeated over and over again. Continuous monitoring lets you see anomalies that you would not normally see if the sampling is too low a rate. So think about the guys never go to the doctor until they're sick, really sick, and so the doctor's model of you is you're always sick
42:01
because you never see the doctor when you're healthy, you only see him when you're sick. So this continuous monitoring could make a big difference. There are also Google self-driving cars. What you're seeing here is model number 2, but I have a video showing you the first model that we were testing with one of our blind employees to see whether we could actually have the car drive our
42:22
employee to work. So if I've done this right, I should be able to get the video to play.
43:13
Stop sign, and the car's using radars and laser to check and make sure there's nothing coming either way. I'm going to fight myself.
43:22
Old habits die hard, man. They don't die. Hey, anybody up for a taco? Yeah, yeah. What do you want to do today? I'm all for taco's on myself. All right, well, let's go get a taco at the drive-thru.
43:43
I'm going to creep along here. Does anybody have any money? I've got money. No, I've got my wallet right here. You can roll down your window and order a burrito. Yeah, put that on. I'm doing very well. How are you today? This is some of the best driving I've ever done.
44:03
Five percent of my vision is sheer timing in life.
44:30
Everything takes you much longer. There are some places that you cannot go. There are some things that you really cannot do.
44:43
Where this would change my life is to give me the independence and the flexibility to go the places I both want to go and need to go when I need to do those things.
45:17
And it's been nice, you know. It's been nice.
45:31
You can imagine we're pretty excited about all that, hoping to keep at it. We have new models, as you can see, under development.
45:41
There are other things that are happening. Drones, for example, are everywhere. Oops. Oh, it sounds like we're still running the video, doesn't it? It feels kind of like a playground. Sure up already. Big playground. There we go. Sorry about that.
46:06
Oh, no. It wants to take me all the way back to the beginning. I don't want to do that. Well, there we go. Fast forward. There we are.
46:20
Drones. Okay. So you all know about these. They're all over the place in the U.S. It's very exciting. The Federal Aviation Administration has been going a little crazy trying to figure out what the rules are for what may become 27 million drones flying around in the U.S. I know Jeff Bezos wants to use the drones
46:41
to deliver things for Amazon. And I had dinner once with him, and I had this image of, you know, a cartoon that showed a drone hovering in front of somebody's door and sending a text message inside saying, I'm here with your delivery, and if you don't open the door in the next 30 seconds, I'm blowing it down.
47:02
And Jeff laughed, and I got nervous that he might actually do that. So I hope he doesn't. So that's another part of this Internet of Things. And then there's Project Loon, because it's loony. These are balloons that Google has built that are operating up at about 60,000 feet in the stratosphere.
47:22
As they move up and down, they're blown in different directions depending on the wind. And so we actually steer them by changing the altitude. The idea is that they are doing Wi-Fi or LTE, long-term evolution radio communications from the stratosphere.
47:40
And the idea is that they circulate roughly at a given latitude. They look for tailwinds to get to the next service point, and then they look for headwinds to hover where they are. But they continue all the way around the world. We are in operation now in Sri Lanka, and we've been experimenting with this for about four years now.
48:02
So the idea here is to provide access to Internet in places that would be very difficult to bring fiber to, you know, up in the Andes Mountains, for example, or the Sahara Desert, or the middle of the ocean, for that matter. And finally, I thought I would show you the Boston Dynamics latest little robot. And this one is called Little Dog.
48:36
That's Big Dog behind him.
48:51
Oh, we've got advertisements here, don't we? That's Google.
49:16
Look at how, that's amazing. The stability of the head is incredible.
49:22
Look at that. This is really impressive.
49:41
There's a camera in the mouth that turns out. You don't have to build these the way dogs are built.
50:10
This is also pretty impressive. Going up the stairs is fairly straightforward for it. By the way, there are 51 videos of these things
50:21
on YouTube in case you want to go look, not just of the dog, but all the other robots that these guys make.
50:59
Okay, so I have a little bit more that I want to show you,
51:02
but what I am going to show you now is not a Google project. It's a project that was started at the Jet Propulsion Laboratory in Pasadena. My colleagues and I began this work in 1998. I've been a visiting scientist there since that time. So this is the implementation, design and implementation
51:23
of an interplanetary internet to support manned and robotic space exploration in the remainder of this 21st century. So we met right after the Pathfinder robot landed in 1997 successfully on Mars. This was after many, many attempts to get to Mars
51:40
after the 1976 Viking landers. And we got to speculating about this because the communications to support the Pathfinder was a direct point-to-point link between Earth and Mars. And of course, that was a pretty limited kind of networking capability, and we thought, what would happen if we had a richer networking environment kind of like the internet?
52:01
And we actually started out thinking that we could use the TCP IP protocols. They worked on Earth, so it ought to work on Mars. But when we started thinking about this, it didn't work very well. Those protocols didn't work very well between the planets, and it should be obvious to you. The speed of light is too slow. Between Earth and Mars, when we're closest together,
52:22
three-and-a-half minutes of one-way delay, and when we're farthest apart, it's 20 minutes one-way. Round-trip time is 40 minutes. The TCP protocol was not designed to deal with a 40-minute round-trip time for protocol, or for flow control. I mean, the flow control is really simple. When you run out of room, you tell the other guy stop sending, I run out of room.
52:41
And if that's only a few hundred milliseconds, that's great. But if it takes 20 minutes for that signal to get to the other guy, and he's blasting stuff at you for 20 minutes, full speed, the packets are falling on the ground and flying all over everywhere. So flow control didn't work. Then there's this other problem. The planets are rotating, and we don't know how to stop that.
53:00
So if you're talking to something on the surface, and the planet rotates after a while, you have to wait until it comes back around again. Or if it's an orbiter, it's a problem. So by 2004, we had the two rovers that were sent to Mars, Spirit and Opportunity. The original plan was to transmit data from the surface of Mars, the way we had with the Pathfinder.
53:22
And the radios overheated, and everybody got all worried about that. And they were only rated at 28 kilobits a second. So the scientists were not too happy about that kind of data rate coming from the surface. And then we said, we're going to have to reduce the duty cycle, because we don't want the radio to overheat and harm any of the other instruments or itself. So they were all upset.
53:41
And one of the engineers at JPL said, well, there's an X-band radio on the rover. There's also an X-band radio on the orbiters, which we had sent earlier to map the surface of Mars to figure out where the rover should go. So we reprogrammed the rovers and the orbiters, so that when the orbiter came overhead,
54:00
the rover would squirt data up to the orbiter. And the orbiter would hang onto the data and transmit it when it got to the right place in its orbit to reach the deep space network, which has these big 70-meter dishes at three places on the surface of the Earth. That's store and forward. And so we developed a whole suite of protocols, called the bundle protocol, to do that.
54:22
The prototypes are actually running now, pulling all the data back from Mars. And when we dropped the Phoenix Lander onto the North Pole, there wasn't any configuration that had a direct path back to Earth. So we used the same set of protocols. And when the Mars Science Laboratory landed, we did it again. So all the data that's coming back from Mars is going
54:42
through the prototype, bundle protocols, of the interplanetary system. We've uploaded those protocols onto the International Space Station. We've had the astronauts using the bundle protocols, the interplanetary protocols, to control rovers on the surface of Earth in real time, because the distance is fairly small.
55:01
They're using the interplanetary protocols, which work just fine over short delays, just like TCP does, but they also work over these long and variably connected systems. So what we're hoping, frankly, over time, is that as we've, oh, we've standardized the protocols with the Consultative Committee on Space Data Systems.
55:21
So now anyone can get access to them. They're fully standardized. The protocols are available. The implementations are available on source boards for free. For anyone who wants to download them and use them. In fact, there's a German university that's implemented these for Android mobile phones as well.
55:40
So what we're hoping is that as new missions get launched by the spacefaring countries of this planet, that they will adopt these protocols and use them for their missions, or even if they don't use them for the scientific mission, if they could reprogram the spacecraft after they've finished their primary missions, they can become nodes in an interplanetary backbone.
56:02
So we will literally grow the backbone over time as new missions get launched to the solar system. So that's the up-to-the-minute story on the interplanetary internet. And that is my last slide, so I'll finish, and thank you all very much for your time. Thank you.