Hi, I’m Jim Kurose,
I’m a professor
at the University of Massachusetts at Amherst,
and I’ve been challenged to describe the internet
in five levels of increasing difficulty.
The internet is the most technically complex system
that humanity has ever built.
The internet is a network of networks.
It’s a platform on which all of the internet applications
that you’ve heard of can be built.
[bright music]
Hi, it’s really, really nice to meet you.
What’s your name?
My name is Skylar.
Skylar, we’re here to talk about the internet,
and I bet you must use the internet a lot, right?
Yeah.
What’s your conception about what the internet is?
The internet?
For me, it’s just something to use when I need
like to search up something or watch videos.
The internet is, physically, these computers
that all talk to each other.
Billions of computers, in the case of the internet.
The internet allows us to do
a lot of really, really interesting,
what we call applications.
You ever think about how that video gets to you
over the internet?
Yeah, I have no idea.
Got a favorite movie?
Matilda.
Matilda. All right.
We’re gonna actually build an internet.
I’ve got a couple of things here that I wanna show you,
or a couple of toys, actually.
Okay, let’s pretend that these round balls are computers.
And the internet is something that connects them.
And right now, the internet is just one communication link.
And Matilda is sent over the internet from this computer
to your computer.
So the internet is a network for carrying information
from one computer to another.
Now this network here looks pretty simple, doesn’t it?
Right? It’s just one thing.
Should we add some more friends in?
Yeah.
Let’s say we want to get a video from here, over to here.
How do you think that video would sort of travel
through this network?
Maybe it could go to here, to here, to here, to here.
That’s right.
So that’s pretty cool.
There are actually lots of different ways to actually go
through the internet to get from what we call a source,
the place that’s sending the information,
to the receiver, the place that’s actually gathering
the information together.
And that’s something we actually call routing.
Huh, but wouldn’t it just be easier
for it to go from here to here,
instead of going from here to here,
to here to here?
Yeah. So that’s a really good observation.
In most pieces of the internet,
that’s exactly what would happen.
We want to take what’s called a shortest path.
But still, there are multiple paths.
And why do you think that might be valuable?
Maybe one way is messed up or broken.
So you go the other way.
Exactly.
So, Skylar, that was a great discussion
about what we just built.
And I wanted to talk to you about,
or ask you about maybe one other really important
part about networks.
And it’s not