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 CCNA in the really old CCNA.
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're 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 Airbnb?
I really like Airbnb's, 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 cabled connections and the bad
old days.
And I've got an old laptop here in the bad old days.
Laptops such as these had Ethernet connections built in, 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 PC.
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 Ethernet connection to this laptop as an example, I have to plug in a USB 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 WiFi.
A lot of devices today don't support Wired connections.
That's especially true, I think, with devices such as these Iot devices.
I mean, this is a hue bulb.
It seemed ridiculous, but in the past I would have had to have used an Ethernet 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 connect an Ethernet cable to a bulb.
What about your phone?
I mean, can you imagine having to connect an Ethernet 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 he has the light going through the fiber cable
is contained or constrained within this cable, so the signal stays within the cable.
Now, 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 multimode 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 are 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 2.4 gigahertz and five gigahertz bands.
Typically, the lower the frequency, the further the transmission, but the lower the data rate or
the throughput.
Five gigahertz, as an example, can't go as far as 2.4 gigahertz.
It also can be absorbed a lot more easily.
So as an example, five gigahertz gets absorbed a lot more by a concrete wall or brick wall compared
to 2.4 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 2.4 gigahertz than five gigahertz, but five 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 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 2.4 gigahertz and five gigahertz.
So those are the two ones that 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 Kaili 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're 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 wider 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 in 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.
We would take a beam and then we can direct the beam.
So we directing 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 that bridges, in example, will
push the signal in a certain direction.
An omnidirectional or all direction antenna sends the signal everywhere.
So if you 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're doing and you're 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.