-
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.
