>> Now, as we mentioned earlier,
when we have a network,
we have a group of interconnected devices.
How do we connect those devices?
We connect them through media and through
specific devices designed to connect computers.
Hubs are what we used to use
very commonly back in the day,
simply for the fact that they were cheap.
But hubs introduced problems and
some security vulnerabilities into the network,
so we moved from hubs to switches.
Switches give us greater control of traffic,
and switches, in a lot of ways,
act like a police officer of a busy intersection;
directing traffic from one path to another.
Switches will allow you to manage
traffic on your network more efficiently.
Routers are primarily about
connecting to different networks.
If I want to connect to the Internet,
I usually do so through a router.
If I want to connect to my branch in Minnesota,
usually I connect to an
external network through my router.
VLANs are going to give us
benefits of both switches and routers.
A VLAN is going to be a virtual LAN,
so we'll be able to segment
our network into different subnets,
if you will, and we can do so on a switch.
We'll talk about why that's desirable later.
Then of course, we have to consider
wireless access and wireless access points,
and how we'll allow these hosts to
connect without being physically wired in.
Another thing to consider is VPN servers,
and with wireless and VPN,
we'll talk about those ideas when we get to
the remote access section.
Every one of these terms we'll go into more deeply.
The next thing we have to have if we're going to
allow communication is a protocol.
A protocol is really important because you could
think of this as the language that computers speak,
and we have to speak the same language.
Quite honestly, that's not
the best definition you're going to hear.
But it is a good way to think about it
because if I'm speaking
Greek and you're speaking Spanish,
we're not going to be able to communicate
unless we have a translator.
The more translators we have,
the more unreliable the communication is.
If you ever want to do something fun,
use Google Translate to speak
a phrase and translate it into Spanish,
then take that Spanish phrase
and translate it back to English,
then take that result and translate it back to Spanish.
Do that about 10 times and you'll
find the end result is hysterical.
By the end, you don't have
anything you were originally communicating.
That's the problem when it comes to protocols.
When you have too many different protocols,
even though we can get a conversion
and can get a device called a gateway,
that's a protocol converter,
we don't get good true communication.
What we like to be doing is to
>> all use the same protocol.
>> A better definition of a protocol is that it's
the set of rules or requirements
that govern communication.
Things like how much data can be sent at once,
how do I know if I'm sending
more data than you can receive,
how long should data exist on the network,
and how should the packets be formatted,
are all examples of information
>> that make up a protocol.
>> But again, from this stand point,
you can think of it as a language.
We have to share the language.
The most common protocol we have and use by
far is the TCP/IP protocol.
It's actually not a protocol.
It's called a protocol stack or suite.
It's called a protocol stack because it's
made up of a lot of little protocols.
As a matter of fact, you already know two of
these protocols, TCP and IP.
There's also HTTP, UDP, ICMP, LMNOP it feels like.
>> There are a lot of
>> protocols that make up the TCP/IP suite.
Each of them have a particular purpose.
Just like everything, we're going to go
over this in more depth later.
The medium, cable or the airwaves.
With cable, there are
three main types that we use for networking;
coaxial, twisted pair,
and fiber optic cable.
Each of these are in use today,
and they each have their place.
We'll cover this in another chapter where we get into
more details and specifics of mediums.
We have to have cable or airwaves if we're going to
traverse because we need that path for data to travel.
Ultimately, what we talked about
here is the fact that there are a lot of elements
that have to come together
if we're going to be able to share
resources and communicate across the network.
At the very basic level,
we have the systems we want to connect.
Then if we want a domain environment,
we have to have a network operating system.
That creates the domain or the realm.
We use connectivity devices and protocols,
that way we can agree on how to communicate.
Of course, there is media,
which is what we traverse.
Also mentioned here,
we have certain network services that we
utilize like DNS and DHCP.