In this video I'm going to discuss Wi-Fi.
Wi-Fi is so important I think for many of us today.
There's no question why we need to learn this.
It's really good that Cisco have put it back into the CCMA in the really old CCMA.
They had Wi-Fi then it was removed but now it's back.
Wi-Fi is really really important in today's networks.
Can you imagine life today without Wi-Fi or wireless connections.
We today take it for granted that we going to have Wi-Fi when we go to the office or a coffee shop or
even for a lot of us at home.
When we book a hotel we expect Wi-Fi connections.
How many of you I mean I do this all the time but do you do this when you check a new hotel that you
want to stay in.
Do you make sure that they've got Wi-Fi or an Air B and B.
I really like air BMD but one of the first things that I'll check is if they have Wi-Fi I'll consider
staying there.
If they don't have Wi-Fi I won't consider staying there.
They have to have Wi-Fi it's that important for so many of us today.
Okay.
Now there's obviously a big difference between Wi-Fi connections and cable connections in the bad old
days.
And I've got a old laptop here in the bad old days.
Laptops such as these had Ethernet connections bolting.
So I would be able to connect a ethernet cable directly to the laptop but modern laptops don't have
that.
I mean your laptop maybe you've got a Mac or a P.C..
They typically don't have any connections for Ethernet cables.
They can only connect to the network or to the Internet using Wi-Fi.
If I wanted to add an Ethan connection to this laptop as an example I have to plug in a USP ethernet
adapter and then I can add this to a wired network.
So for a lot of us today a lot of devices only support Wi-Fi.
A lot of devices today don't support wired connections that's especially true I think with devices such
as these IO T devices.
I mean this is a huge bold it seems ridiculous.
But in the past I would have had to have used Ethan a cable to get a device like this onto the network.
I mean that doesn't make any sense today.
Devices are getting so small.
I mean it doesn't make sense to try and connected ethernet cable to a bulb.
What about your phone.
I mean can you imagine having to connect it even a cable to a phone and then having to be connected
to a physical network so you can't walk around with your mobile device.
The whole point about a mobile device is it's mobile.
I can move this around and still be connected to the network without any problems.
Now that is a big difference between say a wired connection which in this example is using fiber notice
the difference here.
This fiber connection and has the light going through the fiber cable is contained or constrained with
in this cable.
So the signal stays within the cable.
And if I bend it really badly I can get some of the light to come out of the cable.
That's not a good idea.
Bending the cable does affect the transmission especially on multi-modal fiber.
The idea however here is the signal is contained within the cable.
There are advantages however to using wide connections such as this compared to Wi-Fi.
The first thing is typically you can go a lot further.
So with light as an example we can go a lot further.
The cables under the sea of fiber cables we can go much further in distance than we would with the Wi-Fi
connections that we have in our homes or in companies.
Now there is a difference between the signals used in a Wi-Fi network versus a cellular network.
They use different frequencies.
Governments around the world dictate which frequencies are available for which applications so applications
such as 3G 4G 5G use a certain range of frequencies Wi-Fi uses a different range of frequencies and
we'll talk more about those in a moment.
We have two main bands that we need to know about and that's 2.5 gigahertz and 5 gigahertz bands.
Typically the lower the frequency the further the transmission but the lower the data rate or the throughput
5 gigahertz as an example can't go as far as 2.5 gigahertz.
It also can be absorbed a lot more easily.
So as an example 5 gigahertz gets absorbed a lot more by a concrete wall or brick wall compared to 2.5
gigahertz.
So if you want further distance or you want to go through walls as an example it's better in some cases
to use 2.5 gigahertz than 5 gigahertz but 5 gigahertz allows for higher throughput or more data transmission
through the network.
So there's always advantages and disadvantages to any technology that you use.
Copper cables are generally a lot easier to work with than fiber cables.
If a cable breaks it's easier to repair that we're using copper than fiber but fiber is more secure.
So if you want more security as an example in a military environment it's much harder to tap into a
fiber connection than it is a copper connection.
So you may want to use fiber rather than copper fiber can go longer distances than copper can.
But in this part of the course we are concentrating on Wi-Fi and I'm going to talk about the different
Wi-Fi standards.
You need to know that for the exam we're going to talk about the different frequencies I've mentioned
2.5 gigahertz and 5 gigahertz.
Those are the two ones that you need to remember.
We're going to talk about channels.
I'm also going to talk about some of the issues using Wi-Fi.
You've probably experienced a lot of these already.
So as an example if you move to a certain part of a room or a building you get a dead spot where you
can't get a connection.
You move a few meters or a few feet away you get a better signal or better transmission.
So there are a lot of advantages to using Wi-Fi but there are also disadvantages to using Wi-Fi.
One of the big ones is security.
I can use Kelly Linux as an example with a Wi-Fi adapter and I can listen in on your conversation.
Wi-Fi is a hub now a lot of people tell me David there's no point learning about hubs but if you don't
understand what a hub is then you don't understand that Wi-Fi acts like a hub.
In other words we are using the same frequency in the air.
If I listen in on the same frequency that you're transmitting at I can hear your conversation.
I mean we as humans can do that.
You and I are speaking and listening on the same frequency ranges.
Humans can hear at a certain frequency now obviously older people generally have worse hearing than
younger people.
Younger people can hear a wide range of frequencies than older people but for the most part we are listening
on a certain band of frequencies.
If you speak and I stand near you I can hear you.
Now you may be talking to someone else but if I stand near enough I can hear your conversation and the
same is true and Wi-Fi.
If you speak depending on the antenna you have what are called directional antennas that will send a
signal only in certain in one direction it's kind of like a torch will take a beam and then we can direct
the beam so redirecting it in a certain direction but an omnidirectional antenna which is what a lot
of organizations use will send the signal in all directions.
So you get different types of signals different kinds of devices a bridge as an example will push the
signal in a certain direction and omnidirectional or all direction and Tennant sends the signal everywhere.
So if you are speaking to that wireless access point and I'm in the vicinity I'll be able to hear your
transmission.
So security is a big problem in Wi-Fi networks in the past.
We had mechanisms to encrypt data but they were weak and they could be cracked.
Today we use better encryption and authentication methods.
But once again they can also be cracked.
If someone knows what they doing and you using a weak password it's important to use strong passwords
and strong authentication mechanisms especially in corporate environments.
Okay so I've been talking now for a long time.
I think it's time to jump into the details of Wi-Fi.