Good day, viewers. In this segment, we’ll cover a very brief
history of the internet. So, you can see here I’ve drawn you a
rough timeline for the internet. And it goes, from say, let’s call it 1970
to today. So, we’re spanning more than four decades
here. and over that period of time, I’ve drawn
three main phases that I’m going to talk about as the internet having gone through
with ARPAnet phase and NSFnet phase. And really, the modern internet and the
web as we know it today. Throughout those phases, the internet has
grown enormously. In fact, from every phase to the next, we
have about a factor of a 1000 growth which is just huge.
So, for the end of the ARPAnet from a thousand through to, you know, a billion
hosts today, and this is all very rough. We can go into more detail as you’d like,
for many resources you can read to find out a little more about this.
Okay. So, let me tell you a little bit about
each phase. So in the beginning, there was the
ARPAnet. The ARPAnet was a, a network that was
built and sponsored by the US Department of Defense.
It was the precursor to the internet, so it became the internet.
This network was motivated for resource shating.
obtaining access to some, you know, early and relatively powerful, for those days,
computers from offices at different locations.
It was actually launched with a, just a modest four nodes in 1969.
And during the ARPAnet phase, it grew up to be hundreds of hosts.
In fact, during this phase, one of the first killer apps in the internet
emerged. It was email.
this was not what the network was intended for, it was intended for
resource sharing. But email, which was written just a small
handful of years after the ARPAnet was born.
became very popular as people used it to exchange messages.
During this time there were several key influences.
So, I’ve shown here some key influences, leading up to the creation of the
internet. And one of the key influences here is
what is called Packet Switching. Packet switching is something that was
pioneered by Donald Davies in the UK and Len Kleinrock in the United States,
amongst others. And packet switching was really
interesting. It’s really just the notion of packets
and sending them through networks, is what we would think of today.
It’s interesting because it’s quite different than the circuit switching,
which was used as part of the telephone network at that time.
The whole notion was to organize information in small units of packets
through which they were sent through the network.
And this could be much more efficient for connecting computers together.
And using telephone circuits, which are maybe good for people because computer
traffic is very bursty. So, we might sometimes have many packets,
but often times there will be no packets. So, dedicating a whole circuit would be
wasteful. Whereas, if we use packets, we’ll get the
advantages of statistical multiplexing that we talked about in terms of getting
better use out of the links. So, this was one key influence.
Another key influence was that of decentralized control.
from the early efforts of Paul Baran, who produced various designs that emphasized
decentralized control. In those days, the telephone network was
organized very hierarchically. So, that if you took out a high layer
node, you would really paralyze a lot of the network.
Being able to create networks where control is fully decentralized.
So that if you blew up a portion, the rest of the network could continue to
function, was obviously very appealing to the military at the time.
And so, this is often why you often hear the Internet, the ARPAnet, has been
created to withstand a, a nuclear war in which a portion of it was lost.
But really, this is just one of the influences leading up to it as the
ARPAnet took off in the very early Internet.
Another key influence became paramount, and that was Internetworking.
Internetworking here was pioneered by Vint Cerf and Bob Kahn, shown here in
their pictures. internetworking is all about connecting
different networks together into a single larger network.
So, Cerf and Kahn pioneered a fairly early on in the ARPAnet started like in
’74. And this later, because the TCP and IP
protocols. So, really the key idea of internet
networking is that we have different network technologies.
One way you can build a big network is by getting everyone who used the same
technology mandating it. But Cerf and Kahn realized that this was
infeasible already. There were packet radio networks,
satellite networks, and the ARPAnet are all different kinds of technologies.
Cerf and Kahn instead proposed to use a higher layer of interconnection to a
level of in direction, if you will, to combine all of these different networks
together. And they solved the problems which are
were required to be able to inter network these technologies.
For this achievement, their popularly known as the fathers of the internet and
they have received many awards for this. Okay.
So, here’s a early geographical map and a network topology map for the ARPAnet.
It comes from around 1978. You can see by now the ARPAnet has grown
up a fair bit, although by today’s standards, it’s still a very small
network. All of these different so because these
are different kinds of nodes, they were known as IMPs.
This was the name for the early router. I think that’s IMP as in Internet Message
Processor. And the links between things, well here’s
our link here, they ran at 56 kilobytes per second.
So, you can see we’ve got a network here which is growing up.
As it grew up, and now we’ve passed on to I guess thousands of different nodes.
as it grew up, the NSF commissioned a network which played a key role and this
was called NSFnet. The ARPAnet really connected people who
were doing business with the US Department of Defense.
And there were many of players who didn’t have a contract with the US Department of
Defense. Who want to be able to connect using
these interesting, new fango technology. So, the NSF built the network which will
allow all different kind of educational institution, universities to connect to
these network. Initially, this network connected
supercomputer of different sites together.
But eventually, it connected many different sites, and it became the
backbone for all internet traffic, effectively replacing the ARPAnet.
It’s during this period, this was a tremendous growing up period, this period
of a decade or more. It’s true in this period that the classic
internet protocols as we know them today have emerged.
All of TCP/IP the DNS, and the sockets API which around 83 quite a year, I
guess. And an internet running in the form of
PGP, that’s protocol we’ll get to later in the course.
Took a little longer to emerge in the modern form of the blue wrecking lights,
but it was around by ’93. During this period also, there was
tremendous growth and interest in computing and networking technologies.
The personal computer was really coming into it’s own and personal computers
appeared. well, computers appeared and then became
personal computers, first really on campus’ educational institutes for
research. As they became effective, they made their
way to businesses and events in the form of personal computers into home.
So, it’s not just personal computers there computing but networking technology
Ethernet. The most popular form of local area
networking emerged in this period, too. And it took off like wildfire, allowing
all of these early computers to be connected.
And so, the result is that by about ’93, we had maybe a million hosts that were
all connected together as part of the internet, it’s growing up.
Here’s the architecture of this early internet when the NSFnet was in use.
And you can see this picture here is really its meant to just be very simple
and hierarchical. The NSFnet here is the backbone.
What that means is if the two customers in different places want to communicate
with one another. A local customer network, might be a
university network with some packets up to it’s regional network.
Which would send packets to the NSFnet backbone network, which would send
packets down. Which would carry packet, I guess, across
the country and deliver them to the right regional network.
Which would carry packets to the right customer network and we would achieve
connectivity. Now, the early NSF network backbone, you
can see here just the speed it use. Started off with 56 kilobits per second
links, fairly quickly upgrade to 1.5 megabits per second link.
and then to 45 megabit per second links. So, the network was really growing quite
fast in terms of speed, as well as in terms of size.
Well, after a decade or so of all of this growth and the popular technologies in
computing and networking, we arrive at the birth of the modern internet.
which contains the internet and the web as we know it today, is really a
continuation of what was started here. And this was around the year, the early
90s. There are two major changes I want to
point out to you compared to the earlier structure.
Now the, the first is that after around ’95 connectivity was no longer provided
by the single NSF internet backbone. Instead, connectivity is provided by
large ISPs. There are several different ISPs,
handfuls of them, and they’re providing connectivity to people across a wide
area. And they’re also competing with each
other as a business. So, there are now multiple players at
that top level. And the way we’re making sure that
packets get everywhere is that all of these different players.
These large players, interconnected IXPs, Internet Exchange Points, so that they’re
able to exchange traffic and get it anywhere on the internet.
And later, large content providers also come along and connect into these ISPs,
IXPs, so that they can distribute content all over the internet.
So, that’s one change we route across the internet and the architecture of the
internet. Another big change is really the web.
The web which was pioneered by this man over here, Sir Tim Berners-Lee, emerged
and burst onto the scene really because it took off so rapidly.
It emerged around ’93. And it really took off, in terms of
traffic. And it caused a lot of interest in the,
in the internet, everyone wanted to get on it.
The growth led to the formation of what are called Content Distribution Networks,
to be able to efficiently distribute all of this content.
Naming became much more of a concern and this led to the establishment of the body
called ICANN. The Internet Corporation for Assigned
Numbers and Names later on, around ’98. the content has continued to evolve ever
since. most bits now actually video that’s going
around the internet, just because videos are so large.
And most of the traffic is soon to be going over wireless networks.
and probably for mobile devices, not quite yet.
but it’s skewing rapidly in this direction.
And really, the new kinds of content are driving the internet, that’s where we are
today. And I’ll skip all the, the later you
know, Facebook and everything. Because I’m sure you’re more familiar
with the evolution of these particular companies in the internet ecosystem.
Really, it’s the web and the continuation of the web that they’re providing.
and finally, I just want to show you the modern internet architecture.
So, this picture here is to contrast with your previous picture of the NSF network
backbone. You can see here I have the IXPs as the
point of interconnection and different transit providers.
Here’s a transit provider. This is like a big ISP.
Connect to different ISPs, IXPs, and content providers.
Also connect to the ISPs. So, what you might have now is that you
might have the case that content is going from here through an IXP.
To a transit provider and then down to a particular customer or we, we might be
sending traffic from this customer here. If this customer wants to get traffic to
the other customer, we might go up through the transit network.
And then we might go through to the transit ISP, then we might go to an IXP.
And be routed to another transit provider who we would then send traffic down and
let’s say, now we’re going to this customer.
So, you can see they all fit together in a rather different architecture with no
single back part up at the top. That’s the defining characteristic of
today’s internet architecture. Okay.