Let's take a look at computer networking.
The definition of a network is two or more devices
that can communicate with each other.
So the first networks were really quite simple.
We put a crossover cable between two different systems and
so they could communicate and share data.
That expanded later to the idea of a hub where we had
many devices that could all share data, and for example,
now as we see in this diagram, three computers could share the same printer.
The problem with a hub was that all the traffic going from one device
to another was also shared with all of the others.
So along came the idea of a switch, and in fact,
joining switches together so we could have different local area networks,
each attached to their own switch, but then joined together,
and maybe we could call it a tree type of assembly.
The advantage of a switch is that traffic going from one device to
another only went to that destination device and wasn't shared with
everybody else on the network as well.
When we look at network transmission,
the first network transmissions really were wired using
copper to join two devices together,
but then came the idea of using coaxial cable,
a little higher bandwidth or more traffic you could put down.
The idea of fiber greatly increased the speeds of many of our networks,
but also we saw the development and evolution of different types of wireless.
We had wireless access points and wireless fidelity,
the idea of Wi‑Fi being that now we had a wireless access point
that provided access to many devices in that area.
Satellite and microwave were two of the types of wireless
communications that required line of sight.
The device that was going to communicate with a satellite,
or between two microwave systems,
had to be able to see that other destination point.
We couldn't have trees or other things in the way.
We also had the development of infrared,
used a lot in conferences and so on where we could actually
transmit data using infrared signals.
So we have had many different types of networks.
Some networks, by their very nature, are more secure than others.
For example, fiber tends to be a rather secure type of network communications,
whereas something like satellite,
the traffic can be picked up by many thousands of devices
over hundreds of square miles or kilometers.
When we look at network types, we, of course,
have local area networks, which are networks within one fixed,
usually small geographic area.
Then we had wide area networks where we could join
different local area networks together, often a distance apart,
usually using some type of leased line from a telecommunications carrier.
We had personal area networks.
Many of us are very familiar with this.
We have maybe a set of AirPods in our ear talking to the phone on our hip,
and those are communicating via Bluetooth,
and we would call that a personal area network.
We've also seen the development of DARPANET and,
of course, the internet as a result of that,
a combination of many,
many networks joined together into an international network,
which is why we call it internet.
The idea, of course,
of the internet is it that allows us to communicate now all over the world,
and it's a network that's highly resilient to failure
because if traffic has a problem in one area,
it can route over a different direction or a different path.
The Key Points Review.
Networks can be very small, two devices,
and very simple, but of course,
we know that they can also become very large and complex and international.