So, welcome back. Now the purpose, of course, of all this stuff that you had in
your office, and all that banging, and all the sqweeee squealing noise where we're
sending the data across the across the phone using sound. All the purpose was the
fact that computation was rare and extremely valuable. And for scientists who
were trying to solve research problems, access to computers was essential. And you
couldn't all sit, sort of in a little ring around the computer. It's so we would have
phones in our offices and we would, you know, work in our office, just like I'm
working in my office right now. But there wasn't enough computation [inaudible], any
work in my office so I had to connect to something outside. And so this was the way
of science. And, it, it, it was the fact that comp-, computing was rare, and access
to computing was a critical enabler of scientific research. Now, I'd mentioned
earlier, data transfer with leased lines. And so, while it. You tended to interact
with the computer that was rather local, geographically to you because you could
have this permanent dial up connection all day long without paying a permanent
charge. If you were a bank, or you had some really critical need you would lease
some line from the phone company 24 hours a day, seven days a week so you could send
data across that anytime that you wanted. No dialing, it's always connected and,
after while, I mean you can send data, we academics wanted to communicate with each
other. It would be nice to be able to use each other's computers, but we tended to
have too much, but sometimes we don't want to send a file, or some email, or
something like that. And so this led to the invention and the creation of store
and forward networking. And how this would work is we would sort of, you would sort
of have some thing and you would use a modem to do all your dialing, like that. I
mean maybe they had paper and, and didn't. That looks a little too advanced, but you
would have some geographically local computer that was your, sort of the compu
ter that did most of your work. You didn't have a computer in your office, you just
had a connection to the single campus computer or on a few campus computers. And
then what universities would do is they would lease a line. And then we could
send, write a mail program that would run on this computer and then would send mail
and then everyone else would read it. And what happened was is we sort of started
stringing them together in these snakelike structures and so, we could share this.
And so let me just show you kind of how the store and forward networking works. So
somebody sends a mail message in. Now let's say, let's say we are this bottom
person down here, okay. And so someone else has sent a mail message in, they're
sitting in there. And now the next person sends a mail message in and now ten
seconds later, you send a mail message in. Those mail messengers are sitting in a
cue. They're waiting just like waiting in line at the bus stop or waiting in line in
a train station. Waiting in line for a cup of coffee at Starbucks. They're waiting in
line, and what would happen is the computer that was our local computer would
then start sending that data across the line. Okay, and slowly but surely it would
take awhile. And everyone else had to sit and wait. Your poor message is last in
line so you have to wait. So finally this message gets across the closest link. And
then the, the next message starts being sent and you have to wait for that message
and wait and wait and wait and wait and wait. Wait and wait and wait! Hey wait.
Okay. Now its finally your turn. So your message finally gets to use the one
connected line. So they, they are sought of stand in line until your turn
[inaudible] runs acrossed. And they all, these messages aren't destined for just
one computer away, then they got to go through the whole thing again, move across
the next link until you know eventually you move across one link over here and
then go another, and then finally talks to the people who get their email. So its a
sought of dedicat ed line and you had to stand in line to get your chance. And the
key thing here is each of these lease lines has a fixed cost 24 hours a day
seven days a week, and it's very dependent on the distance, so we saw a weird
phenomena. ≫> And that is. ≫> If we could add hops, it would slow our
message down, but it would reduce our cost greatly. And so let's just say we have
Michigan State University, which is where I got all my degrees from. University of
Michigan here in Ann Arbor, which is where I work. And let's say, you know, we're
connecting to the rest of the world, and we're going through Cleveland, where Case
Western Reserve is. Case Western Reserve was the early innovator in, in networking,
and so we have two leased lines with a certain distance, right? One from East
Lansing to Ann Arbor and one from Ann Arbor to Cleveland and so we're sharing
the cost of these lines between three schools and we can all kind of connect to
the rest of the internet, all connect to the rest of the internet out here and, and
we just, some of us have, are farther away, and so we take longer. The folks in
Cleveland are closer. Like all the rest of the connection to like the East Coast and
the West Coast come through, say like here Cleveland, but if we can simply convince
somebody in between us like say Toledo to add a connection. Now of course. Of
course, this, [inaudible] Give me green. There we go.'Course this line probably
goes, probably went around when we just went straight to Cleveland, here. But
basically if we can convince Toledo to sort of put in their computer and hold
onto our messages for a while, we could send now one hop, two hops, three hops.
But the cost now is not that different, because the original long line between Ann
Arbor and Cleveland was distance sensitive. And, so, you can think of this
as, you can get this almost for free. And now we have a whole additional university.
Both to send stuff to, and they can send to the whole world as well. And so this
motivation to effectively take the same c ost, and now basically we're taking this
cost, and dividing it by four schools. And if you start thinking about it, it doesn't
take long to say, "You know what, let's put one here, one here, one here, one
here, and one here." Because the cost of the phone company isn't that different.
You can think of each of these as adding some delay to your message. You know, and
given the fact that each of these represents an outbound queue of messages
that are waiting to be sent, there's some delay. There's some cost adding this, but
It's so much cheaper. So our faculty have to wait another twenty minutes to get
their mail through if we can bring that many more universities on. And so this
just works out. There's this sorta motivation that if you can find an
intermediate person, geographically intermediate school or university or
company, and you can add them in, you can replace one long link with two short
links. And this led to long chains of mail. And so from the mid 70s to the late
80s most academics were communicating through a network that was like this. It
typically was email and I recall when I first started to use national email. It
took a long time for mail to go back and forth but it was actually quite magical I
mean who cares if it took an hour. Now we expect it in three seconds. We send an
email and hit the refresh buttons, hurry up, hurry up. You know, it could be hours,
it could be days if you were going far enough and your message was long enough
and you end up behind too many queues. And so you had this one computer locally and
every once in a while you'd do most of your communication computation locally.
And every once in a while you would fire a note off and that would kind of fight its
way through all those successive connections. This is sort of the life in
the early 1980s. One of the, most widely distributed networks of this kind was a
thing called Bitnet. And Princeton was kinda the hub of this and these tendrils
of connections ran out from Princeton. And by connecting to a, a network with lots of
oth er folks, then you had more people to talk to. And the more people that you,
that were connected the cheaper that it was for everybody. So it was a pretty, it
was the perfect kinda thing that caused people and com-, universities to want to
work together, because together their shared cost was much, much lower than to,
to provide this uniform connectivity and email. So at the same time, during that
same period, where most of us were using store and forward network, with our one on
campus computer, a bunch of computer scientists were funded by DARPA. The
Defense Advanced Research Projects Administration, to imagine a different
kind of network. And the idea was direct connections are expensive. The long trails
of store and forward networks, they're very slow, and if you had a giant message
that you got behind, then what, how do you get past that. It could clog the system up
for, for hours, if not days. And, and how do you keep from failures breaking the
entire system? If you think about a store and forward network, one computer going
down would cause data to back up on both sides of that computer until it's done.
And so, you don't really wanna have one outage and, and how if we have sort of
instead, instead of just a few messages, what if we just wanted all the messages to
go simultaneously, so that there's more of a fair allocation of the network, rather
than whoever gets there first gets it all until they're done with it. And, and so
Darpa wanted to solve the problem of outages. You know, many will say that it
had to do with, battlefield conditions, which is probably true They expected that
various connections would go out in, in, in dynamic situations. Maybe it was that
stuff was moving. But also how to be more efficient. And so, in effect, you can kind
of think of this as all a game, where the phone companies own the wire. So everyone,
even government, even military has to lease the wire from the phone companies.
And so everyone is like doing research to figure out or creating systems to figure
how not to pay t he phone company so much money, okay. So these research networks,
and so if we look for example at this one down here by 1972 they had this network. I
have my, I, yes I got a caller. So they have this network by 1972 and it's got,
like some [inaudible] right around twelve, fourteen, fifteen hosts in it, and it goes
cross-country. Now, now, the, the key about this is in 1972 to have leased lines
that were up 24 hours a day, seven days a week, all the way across the country? Very
expensive. But hey, it's a government project, and the government says this is
important so we're gonna spend the money because, so we're imagining battlefield
communications of the future and our own ability to do computations so they could
have comp-, computational equipment all over the place. So this was very
expensive, but research dollars were being flooded into it, because the q, they were
solving a research question. If you just think about this as a network, it was not
all [laugh], it wasn't sorta like, it was so costly that the average person wouldn't
like, pay $fifteen a month to use it. It would just be that costly. But it's okay.
Now if you look at this, you see that across the United States, there was always
at least one connection. They had three cross country links with totally
independent cross country links, with the ideas that you could take one of these
things out, and you could still be functioning. So they, they were able to
research all these things right, as well as the efficiency problem, which they
solved using packet switching. So, by the mid 70's there was quite a few folks on
this. And for a group of people they just started using it in production. It was
pretty cool, right? If you were, if you were one of these universities or
companies, you had a pretty cool, futuristic world. You could, you could
send email and get an answer back in two minutes, or a minute, or 30 seconds, even.
And so it was kind of this futuristic world that was heavily subsidized by the
government in the name of researching. And so there are two essential things that
really came out of this research. And one is the notion of what was called Packet
Switching. Packet Switching basically eliminates the problem where once the
message starts using that leased line wire, you have to wait till they're done.
As, as I showed in that in that store and forward. What you want is to be able to
send little pieces. Break the messages up into little pieces, and then they, they
Each, each message has a little bit of the network connectivity and then the next one
comes after it. And so you could have many messages going at the same time. And a
real long message won't fill up the network, fill up the connection forever
and ever and ever. So it and it also allows, if you to break the message up
into small parts, they can flow over different paths. The other thing that they
figured out was this notion of instead of oop, oop, oop come back here, come back
here. Instead of using computers as the intermediate stop points, because in store
and forward you could have a lot of messages so you tend to store them on
disks. Whereas routers, these packets were smaller individually than the entire
message and so they didn't need to store them nearly as long and they didn't need
as much storage. So these are, routers are just a form of computer, right? But they
were specialized for moving just data from one connection to the other without long
term, without storing that data for a long time. So, I like to think of packets as
postcards, letters and think of the Packet Switching Network as the postal system. So
let's say, for example, I had a friend, and his name is Glen, and I want to send
him a message. I want to send him a message that's hello there, have a nice
day. But I have a limitation. I have limitation. All I have is postcards that
it can, that can store ten characters on them, and I have to send my message to
Glenn using only 10-character postcards. And so, before Glenn and I part ways, we
agree on the following protocol: that I will take the first ten characters of the
me ssage and put them on one postcard, and then I will put an address from Chuck to
Glenn, and I'll put a sequence number. So that says that hey, hey Glenn, here comes
a message, this is part one. Then we take the next ten characters. And I mark that
as part two, from Chuck to Glen. And then here's the third part, it's marked as part
three, from Chuck to Glenn. And, so, what can I do now? Well, I walk out to my post
office box, and I send'em, I just stack'em in. I might stack them neatly in order.
Now, they go through the postal system. Like, they get dropped, some get dropped
on the ground. A couple of them get lost. Or they end up on the wrong truck. They go
through Kansas City by mistake. Blah, blah, blah, blah, blah, blah, blah. Blah,
blah, blah, blah, blah, blah, blah, blah, blah, blah, blah. But, you know, some days
later. They start arriving at Glen's house. And so, Glenn goes out to his post
office box, and he gets a message. It's hello ther-, and it's sequence number one.
So it looks like Chuck is going to send me a message, and I've got the first part of
it. That's pretty cool. So then he goes out the next day, and out comes, nice day.
But this is #three. So, because I've numbered them, Glenn knows that there's
some missing bits, right? So Glenn just can hold on to them, and leave a little
space on his kitchen table for what he hopes to be message number two. And so
message two finally comes out. And now Glen is capable of saying, "Looks like I
got the whole message and I can reassemble them. And, surprise, surprise. I have just
sent him. With a lot of effort in three packets. Hello there! Have a nice day."
And so this notion of breaking the message into packets, labeling each packet with a
sequence number, and then sending them to this network that can take multiple paths,
You can even have a situation where the you know, the message would go across one
link, it would get lost and then it would, you know go across a different link. So
you have ways of recovering. You can recover the messages. We'll talk about
that later as well. So this ends up with a sort of a structure that has these
computers that are specialized routers in the middle. And the routers have multiple
connections. And if we take a campus, for example, and the campus has some computers
and we have high-speed networking on this campus. We have some, you know, stuff in
our offices on the campus, and then we have some stuff in the machine room and we
talk to these things. And then, somehow, our entire campus has a little spicket to
the outside world and this is our, sort of, campus router and we get this router,
and then there are, sort of, intermediate routers that are inside the network. And
if you sort of look at a router, a router sort of simply forwards traffic and the
traffic now is these small packets, rather than whole messages, so you don't need a
disk drive on these, on these routers. There's no disk drive on these routers, so
that they just kind of grab a packet and they forward it. And the systems are
trained. And the software does not overflow the network. We'll talk about
that later, much later. And so these routers have these real simple view of the
world, they've got some incoming traffic, they've got some outgoing traffic,
outgoing traffic. And so they just grab and forward. It's like a intermediate
postal spot, right? They, they grab big thing of. Postcards and books. Send them
to the right place and, and they get where they do and so eventually the data gets.
Getting a little sloppy, getting a little messy, here. Eventually, the data sort of
is broken up, finds its way to the other end, and then dumps out in some campus
local area network and then somebody sees the data on the far end, okay? And so it
might different, take different routes, you know? It might get lost that might
crash and then it has to get sent again on a different route. And so these things,
these little pieces, these little postcards, find their way through the
series of routers. And we can, we both can see sort of like a, a whole campus being
connected. We can see individual folks who are, buying, buying some dial up through
cable or DSL, and at some point we like to represent this whole thing. Here is this
big cloud, this you don't worry about the detail inside here. Call that the cloud.
We'll see it in the future slides it`s just a cloud, a white, fluffy cloud. That
means that we are trying to hide the detail. But in there it`s just a bunch of
things that are connected. In a way it`s not that different in the store and
forward network, except for the fact that every message is tiny, so it doesn't clog
the whole network up, which means that routers don`t have to have a lot of
intermediate storage to hold on to these packets in flight. And it also means that
every packet can take a different path and if things get loaded up, they can
dynamically move. And so. Here's just sort of an example problem to solve. If you
think about it, these routers have a very limited view of the world. And there are
hundreds of thousands of routers around this world right now. And they don't know
the entire network, they kind of know the lines that come in to them and the lines
that go out, just like a post office in Kansas city doesn't know every address,
every house in the world. It just knows the trucks that are coming in and the
trucks going out. And so these packets that have to and from addresses can get a
little confused at times. So we won't solve this but if, if we had a situation
where This particular packet would come into a router, and it would route it here,
and then this packet would see it and then it would route it this way, this packet
would see it and route it this way, this packet would see that this router would
see it again and say, oh, I gotta route it that way. And so we end up in this
situation where we would create a loop. Okay. So this is the kind of technical
things they had to solve to keep these things from going round and round and
round and sort of melting the network. We'll talk more about that in a bit. So.
This was DARPANET. It was doing research on these kin ds of problems. The kinds of
problems of, you know what's the best way to do this? How big should packets be?
What should, how long should we wait until we send a packet again? You know, this
kind of thing. And so that was our research network. And the, that could've
gone on forever, it might've been a purely military project, but. At the University
of Illinois - Urbana Champagne - folks started to think about super computers and
starting all the way back to Bletchley Park, science was enhanced by the use of
computations. And so as the 70's and 80's were happening, all these scientists were
sort of like, "Wow, I can do better physics. I can do better chemistry. I can
do better material science. I can invent new plastics. I can do pharmacy. I can do
all kinds of things. With computers. And so what happened was is everyone started
asking the government. For money. For computers. It's like, "I need a bigger
computer. And if I, if I had this bigger computer. I could do research." Matter of
fact. I was part of all this. Matter of fact I wrote a book. High Performance
Computing. Here's the book. That's kind of what I did before I became an internet
guy. These are beautiful things. Here's, this isn't, was my baby, I never got this.
This is like about $8,000,000, it's not small like this, this is a model of a
Convex C3800 supercomputer. And each of these was the size of a refrigerator, it's
slightly taller than me. I would be about this tall, right here. And each of these,
I think this is like, like I said, like $8,000,000 or something. And I wanted one
just for me. And so the problem is, is that, you know, I'm a nice guy, and I'm
probably worth $8,000,000 of the governments money without a doubt, but not
that the government didn't always think about that. So we couldn't all have out
own personal computer, or at least our own personal supercomputers. Today, of course.
This has about as much power as this, but this is not a history of computers.
Computation. The iPhone is as powerful as this thing, it literally with abou t as
much storage, But what happened was, is, all these scientists would say give me,
give me this supercomputer. I need a supercomputer to do this, I need a
supercomputer to do that. And the National Science Foundation said oh, hmm, well, why
don't we just buy a few of these supercomputers and put them in these
supercomputer centers and then let people connect to them. And then make people, and
make it so they could share, so we didn't have to give every single scientist one of
these things. And so. The notion that we would create a network to connect these
things, again, seems completely logical today, but in 1981, 1982, 1983, it wasn't
entirely the most logical idea. And of course, the telephone companies might have
something to say about that and so the next person that you're going to meet is
Larry Smarr from NCSA, the National Center for Supercomputing Applications. And Larry
Smarr was one of the early innovators that sort of realized that we had to build
computational infrastructure and internet computational infrastructure. And did a
lot of work to convince the federal government that this is something that we
should do. And so let's go ahead and meet Larry Smarr.