WEBVTT

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 Hello and welcome to this video
 titled Wifi Components.

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 In this short video, really going to
 be covering just one thing which

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 is the different types of wifi components
 or what makes up a wireless

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 LAN. More terminology than anything
 else, but let's just dig into the

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 three primary components you'll find
 in a wifi network, starting with

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 the wifi clients.

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 So wifi client, technically the
 term for this is a wifi station.

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 So if you were reading an IEEE document
 and you see the word station or

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 sometimes just STA, that's
 referring to wifi client.

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 So this would be anything that is an
 endpoint for data, anything that's

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 for example originating data and then
 sending it on to the wifi, or maybe

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 data is coming through the wireless
 LAN and terminating on this device.

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 So wifi client means that data is not passing
 through it, it's not transporting

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 or forwarding data, it is the origination
 point for the data or the termination

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 point for the data.

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 So wifi clients as you can see here in
 these graphics here would be consisting

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 of things like your laptop, your smartphone,
 your tablet, these would

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 be examples of wifi clients.

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 Basically the thing that you use to
 get on the internet or whatever to

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 do your wifi networking.

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 So what makes some things, you know,
 obviously different from their form

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 factor clearly tablets and smartphones
 and laptops physically look different,

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 but inside these devices what are some
 other differentiators between wifi

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 clients or wifi stations?

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 Well, number one,
 the power source.

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 So wifi clients are basically subdivided
 into either those that utilize

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 batteries like your smartphone or your
 tablet and those that have an AC

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 power source. Now, why would
 we care about that?

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 Well, if you know anything about wifi
 physical layer or phi standards,

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 you'll know that wifi bystanders have
 a maximum theoretical data rate.

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 For example, 802.11n which came out in
 like 2009 had a maximum theoretical

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 data rate of 600 megabits
 per second.

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 But there's a lot of things that are
 involved in getting as close as you

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 can to that maximum theoretical data
 rate, part of which is your power.

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 So if you want to get as close to the
 maximum theoretical data rate as

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 possible, your wifi client needs to
 have as much power available to push

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 out that signal.

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 So clearly if I have two clients I'm
 using, one is plugged in with an

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 AC power source, the other of which
 is using a battery, there's a very

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 good chance that the device is operating
 under the battery is not going

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 to be able to get as close to that maximum
 theoretical rate as the device

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 that's using the AC power source because
 it just doesn't have as much

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 electrical energy available to it to
 push out those radio frequencies.

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 So that's one difference
 here and a big one.

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 Another one is the quantity
 and types of antennas.

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 The more antennas you have,
 the faster your wifi is.

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 So let's back up for a little bit.


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 When wifi first came out in 1997 and
 then was really became popular in

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 1999 with 802.11b, there was only
 a requirement for one antenna.

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 That's all you need is.

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 Matter of fact, you couldn't find anything
 that had more than one antenna.

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 But as these wifi clauses and amendments
 have come out over time like

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 802.11b, then 802.11n, and then 802.11ac,
 they have found ways of manipulating

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 the electromagnetic energy by
 using more than one antenna.

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 So once again, with the newer standards
 of like 802.11n, AC, and soon

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 we're going to have AX, once again,
 to get closer to that theoretical

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 maximum data rate, you have to have
 more antennas available to you.

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 And this is also something that's
 different with clients.

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 For example, a lot of wifi clients like
 a smartphone will only have one

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 antenna in it. Now, by way of comparison,
 802.11n is a very good option.

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 Specifies that you could have, I believe,
 will definitely with 802.11ac.

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 Let's talk about AC.

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 With AC to get as close as you can to
 that maximum theoretical data rate,

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 you would need 8 antennas.

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 That's right. Imagine
 it for a second.

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 Imagine looking at something that
 has 8 antennas sticking out of it.

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 You would need to use all 8 of those
 to get as close as you could to that

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 maximum multi-gigabit rate
 that 802.11ac offers you.

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 Have you ever seen a tablet or smartphone
 or anything else that has 8

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 antennas sticking out of it?

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 Probably not. So your tablet, your
 smartphone typically only has 1 or

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 2 antennas in it.

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 Your notebooks and your laptops
 might have 3 antennas in them.

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 So what we're saying here is the more
 antennas you have, the faster you

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 can go. And that's another thing that differentiates
 one client from another.

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 And then lastly, the quantity
 and types of transceivers.

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 And you might be thinking, what
 the heck is a transceiver?

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 I've never heard of that before.

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 All right, well, think about this.


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 When using radio waves, you've
 got transmitters and receivers.

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 For example, think of the radio
 in your car, in your automobile.

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 That just has a receiver in it.

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 There's no way, even if you're a MacGyver
 or somebody else, there's no

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 way you could tweak that to
 transmit something out.

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 It doesn't electrically have the components
 to push out to originate a

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 radio frequency.

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 All it can do is listen for radio frequencies
 coming in and then decode

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 those. That's an example
 of a receiver.

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 So a transceiver is a component that
 has both transmission capabilities.

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 It can originate radio waves.

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 And it has receiving capabilities.


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 Hence we say transceiver.

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 Well, once again, in the original world
 of Wi-Fi back in 1999, you only

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 needed one transceiver to push out
 the electrical energy through your

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 antenna. Or that's when it was transmitting
 or when it was listening,

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 it would receive electrical, I would
 receive radio frequencies on the

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 antenna and then turn that into electrical
 energy inside the body of the

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 receiver and the receiver would
 decode that into ones and zeros.

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 You only need one.

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 But once again, with the newer standards
 of like AC and AX to get as close

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 as possible to that really, really
 fast rate, you need more than one.

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 So this also differentiates one type
 of Wi-Fi client from another is how

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 many transceivers it has.

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 So if you're ever in the market for
 a new smartphone, tablet or laptop,

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 now you have something
 to think about.

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 In addition to looking at how much memory
 it has, well, how fast the CPU

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 is, you might want to dig into the specifications
 and ask yourself, hmm,

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 between these two laptops I'm looking
 at, does one have more antennas

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 than the other? Does one have more
 Wi-Fi transceivers than the other?

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 That will also be a buying
 decision for you.

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 So we clearly have the clients.

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 Also some Wi-Fi clients don't support
 the newer Wi-Fi standards.

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 For example, 802.11AX, which has not
 been completely standardized yet

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 and ratified, but they're expecting
 to do so in 2020, you might have a

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 client right now that like a laptop
 or tablet that doesn't support 802

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.1X. It physically, its transceivers don't
 have the capability to manipulate

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 the radio frequencies the way
 that 802.11AX requires it.

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 So that's another thing.

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 You might, once again, if you're in a
 buying situation with two different

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 laptops, one laptop may have been produced
 two months ago, very expensive.

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 Another laptop may have
 been produced last year.

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 You can save a few hundred dollars by
 buying that one, but in the Wi-Fi

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 world, that one might not support the latest
 and greatest Wi-Fi developments,

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 so you might not be getting as fast
 Wi-Fi on that as if you bought the

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 latest and greatest laptop.

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 What's another component
 of a wireless LAN?

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 So we've got our clients.

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 Well those clients are going to connect
 wirelessly to a central point,

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 which is called an access
 point or a wireless AP.

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 So this is a consolidation
 point for clients.

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 When Wi-Fi first came out, once again
 going back to 1997 and 1999, you

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 had an option. You could actually have
 Wi-Fi clients like two PCs use

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 their transceivers to talk
 directly to each other.

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 That was called ad hoc mode.

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 And then alternatively, you could have
 them talk to a consolidation point

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 called an access point.

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 These days in 2019, most Wi-Fi clients
 out there don't even have the ability

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 to talk to each other.

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 When you go into their Wi-Fi settings
 or into your networking mode, you

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 can't even get them to do that.

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 So pretty much all Wi-Fi, you know,
 indoor and outdoor Wi-Fi these days

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 involves a client connecting
 to an access point.

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 And the access points function is not
 only to let different clients talk

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 to each other, so for example, if you
 and your coworker Bob are sitting

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 next to each other and you want to share
 data over the Wi-Fi, you're not

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 going to be sharing data
 directly with each other.

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 Your radios are not going
 to be talking directly.

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 You're going to be talking to the access
 point and then the access point

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 will then send your signal
 over to Bob and vice versa.

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 So that's one way an access
 point can be used.

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 But 99.9% of the time, when you're sending
 your data, sending or receiving

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 data via Wi-Fi, the destination is
 not meant for somebody sitting next

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 to you. It's meant for somebody
 on the wired network.

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 Or maybe even far away
 across on the internet.

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 So this is another point that
 the access point does.

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 The access point bridges the
 wireless and wired domains.

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 It has the ability to take in Wi-Fi
 frames and convert them into wired

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 Ethernet frames and then put
 them onto the wired network.

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 Because remember that the way Wi-Fi frame
 headers are created are completely

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 different than the way that wired
 Ethernet frames are created.

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 So your access point knows the difference
 and can translate from one type

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 of frame to the other.

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 So maybe you're in the market for purchasing
 an access point and there's

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 a lot of them out there.

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 How do you differentiate
 between them?

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 What are some of your
 buying decisions?

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 Well, number one, you have to decide
 do I want a centrally managed access

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 point? We sometimes call this
 a lightweight access point.

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 Or do I want an individually managed
 or autonomous or standalone access

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 point? What this is referring to is let's
 say you're purchasing an access

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 point for your house.

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 You want to have some wireless
 connectivity in your home.

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 Well, in that case, you're probably
 going to want to get yourself what's

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 called an autonomous or
 standalone access point.

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 That's an access point that like it says
 doesn't need any external device

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 to control it. Once you plug in that
 access point, you can get access

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 directly to its GUI or its command line
 that's built right into that access

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 point box itself.

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 And by connecting to the access point,
 you can configure it, you can manage

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 it, you can change it, you can
 turn features on and off.

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 It all has that ability
 right there.

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 Whereas let's say you're a network
 administrator in a company that has

0:11:12.880000 --> 0:11:15.460000
 dozens or hundreds
 of access points.

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 Well, you're probably not going to
 want to log into each access point

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 one at a time to configure
 it and manipulate it.

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 So that would be a case where you probably
 want to purchase what's called

0:11:23.760000 --> 0:11:28.600000
 lightweight access points, which are
 centrally managed by a central box

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 that we're going to get into the next
 slide that controls all of these

0:11:33.440000 --> 0:11:37.580000
 access points. So in that case, the
 access point itself might not even

0:11:37.580000 --> 0:11:40.700000
 have a GUI. It might not even have a
 command line that you could get into

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 even if you wanted to.

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 You'd have to access this other box
 itself and from there, it can manage

0:11:47.420000 --> 0:11:49.100000
 the access point.

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 What other things make access points
 different from each other?

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 Well, the quantities and types of transceivers
 or you could say the radios

0:11:57.560000 --> 0:12:04.200000
 within them. Most access points these
 days support both a 2.4 gigahertz

0:12:04.200000 --> 0:12:07.540000
 transceiver and a 5 gigahertz
 transceiver.

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 Now these are physically separate electronic
 components, a 2.4 gigahertz

0:12:12.580000 --> 0:12:16.980000
 transceiver. If that burns out and gets
 fried, if your 5 gigahertz transceiver

0:12:16.980000 --> 0:12:20.380000
 is still working, you can still connect
 to that with your Wi-Fi clients.

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 They're physically
 distinct things.

0:12:23.180000 --> 0:12:25.160000
 And how many of them you have?

0:12:25.160000 --> 0:12:30.360000
 You know, back in the old days, back
 in 2000, 2001, your typical access

0:12:30.360000 --> 0:12:34.480000
 point on the market would just have
 one 2.4 gigahertz transceiver and

0:12:34.480000 --> 0:12:37.100000
 one 5 gigahertz transceiver.

0:12:37.100000 --> 0:12:38.380000
 And that was it.

0:12:38.380000 --> 0:12:44.600000
 Nowadays with the newer Wi-Fi standards
 of 802.11ac, ad, and aX coming

0:12:44.600000 --> 0:12:47.720000
 out, access points need to
 have multiple transceivers.

0:12:47.720000 --> 0:12:53.300000
 Maybe 4 or 5 or even 8 of the 5
 gigahertz transceivers alone.

0:12:53.300000 --> 0:12:56.340000
 And maybe 4 or 5 of the 2
.4 gigahertz transceivers.

0:12:56.340000 --> 0:13:00.220000
 So the more transceivers you have,
 the faster that access point can go

0:13:00.220000 --> 0:13:03.840000
 and the more clients
 can connect to it.

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 And the quantities and
 types of antennas.

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 I just talked about this in the terms
 of Wi-Fi stations or clients.

0:13:09.600000 --> 0:13:12.720000
 The same thing here holds
 true with an access point.

0:13:12.720000 --> 0:13:14.980000
 Well, look at that access point in
 the lower right corner there, that

0:13:14.980000 --> 0:13:18.560000
 circle. You don't see it, but there's
 actually antennas in there.

0:13:18.560000 --> 0:13:21.120000
 And I can guarantee you, it's
 got more than one antennas.

0:13:21.120000 --> 0:13:25.900000
 That access point probably has at least
 three or four antennas built into

0:13:25.900000 --> 0:13:30.740000
 it, minimum. So the quantities and
 types of antennas is important.

0:13:30.740000 --> 0:13:34.060000
 So once again, if you're in a buying
 situation with access points and

0:13:34.060000 --> 0:13:37.180000
 you can spend a little bit more money
 getting the access point that has,

0:13:37.180000 --> 0:13:41.940000
 let's say, 8 antennas versus the other
 access point that only has 4, you'd

0:13:41.940000 --> 0:13:45.100000
 be better going with the more expensive
 access point because it can have

0:13:45.100000 --> 0:13:50.780000
 more clients connected to
 it and it can go faster.

0:13:50.780000 --> 0:13:55.140000
 Another differentiator is whether the
 access point is indoor or outdoor.

0:13:55.140000 --> 0:13:58.000000
 A lot of times we don't really think
 of this, but this is true.

0:13:58.000000 --> 0:14:00.760000
 There are outdoor access
 points you can get.

0:14:00.760000 --> 0:14:04.800000
 These are typically installed like on
 the walls of buildings, externally

0:14:04.800000 --> 0:14:09.760000
 facing buildings or maybe on light
 posts outside or telephone poles.

0:14:09.760000 --> 0:14:13.120000
 But these are meant to give people
 outside walking around or possibly

0:14:13.120000 --> 0:14:16.740000
 even driving access to
 Wi-Fi connectivity.

0:14:16.740000 --> 0:14:21.620000
 But clearly an outdoor access point
 has different needs than an indoor

0:14:21.620000 --> 0:14:24.920000
 access point. An outdoor access point is
 going to have all sorts of fluctuations

0:14:24.920000 --> 0:14:28.100000
 in temperature. It might
 get rained upon.

0:14:28.100000 --> 0:14:31.340000
 It might get snowed on and
 icicles might hit it.

0:14:31.340000 --> 0:14:36.860000
 So it has to be able to withstand
 all those weather elements.

0:14:36.860000 --> 0:14:39.040000
 An indoor access point,
 not so much.

0:14:39.040000 --> 0:14:43.460000
 So you could say that an outdoor access
 point is more ruggedized than

0:14:43.460000 --> 0:14:44.920000
 an indoor access point.

0:14:44.920000 --> 0:14:47.300000
 And you're going to pay a little bit
 more for that outdoor access point

0:14:47.300000 --> 0:14:49.300000
 because of that.

0:14:49.300000 --> 0:14:56.160000
 And then lastly, another differentiator
 is enhanced and proprietary features.

0:14:56.160000 --> 0:15:02.240000
 So your typical Wi-Fi standards of
 like 802.11n, 802.11ac, if you read

0:15:02.240000 --> 0:15:06.900000
 those documents which are really heavy
 reading by the way, there are lots

0:15:06.900000 --> 0:15:10.440000
 of different features that
 the standard itself can do.

0:15:10.440000 --> 0:15:15.740000
 Some of which are mandatory, some of
 which the document will say, hey,

0:15:15.740000 --> 0:15:19.060000
 if you want to, you can use this feature
 and you can use this feature.

0:15:19.060000 --> 0:15:23.520000
 So any access point that supports, let's
 just pick one out of thin air,

0:15:23.520000 --> 0:15:29.420000
 802.11ac. Any access point that says
 it's 802.11ac should support every

0:15:29.420000 --> 0:15:34.860000
 single feature whether it's optional or mandatory
 that's in the AC specification.

0:15:34.860000 --> 0:15:39.980000
 But above and beyond that, if that access
 point was created by Cisco as

0:15:39.980000 --> 0:15:44.060000
 an example, Cisco quite probably will
 also have their own proprietary

0:15:44.060000 --> 0:15:49.020000
 features built into that access point
 as well to do it other fancy spiffy

0:15:49.020000 --> 0:15:54.260000
 things that maybe a maraki or a ruckus
 or an aruba access point would

0:15:54.260000 --> 0:15:55.440000
 not be able to do.

0:15:55.440000 --> 0:15:57.560000
 So that's another thing that
 differentiates them.

0:15:57.560000 --> 0:16:00.960000
 So so far in a wireless LAN, we've talked
 about two different components.

0:16:00.960000 --> 0:16:05.940000
 The two main components you have to
 have are your stations, which are

0:16:05.940000 --> 0:16:09.600000
 your clients, and they all
 connect to an access point.

0:16:09.600000 --> 0:16:14.220000
 The third thing which is optional
 is called a Wi-Fi controller.

0:16:14.220000 --> 0:16:17.900000
 Now this goes with those lightweight
 access points I just talked about.

0:16:17.900000 --> 0:16:23.500000
 This manages a group of access points
 if they are lightweight access points.

0:16:23.500000 --> 0:16:25.060000
 So it controls them.

0:16:25.060000 --> 0:16:29.260000
 It can also control Wi
-Fi access for clients.

0:16:29.260000 --> 0:16:33.340000
 So if you're a network administrator
 for a large company that has dozens

0:16:33.340000 --> 0:16:36.560000
 or hundreds of access points, you're
 probably going to want them to be

0:16:36.560000 --> 0:16:40.000000
 centrally managed by one of these
 things called a controller.

0:16:40.000000 --> 0:16:42.820000
 And sometimes a controller is a physical
 box like here's a very small

0:16:42.820000 --> 0:16:44.500000
 one that we see right here.

0:16:44.500000 --> 0:16:47.520000
 Sometimes a controller will just be
 a software element that you'll load

0:16:47.520000 --> 0:16:51.260000
 into a server. But either way, the main
 point that controller is to number

0:16:51.260000 --> 0:16:53.380000
 one, discover all
 the access points.

0:16:53.380000 --> 0:16:57.180000
 It has to somehow know where they are
 and what their IP addresses are.

0:16:57.180000 --> 0:17:01.560000
 Number two, it'll probably download
 some software or firmware onto those

0:17:01.560000 --> 0:17:04.480000
 access points to make sure they're
 all operating at the same software

0:17:04.480000 --> 0:17:08.140000
 levels. Number three, it'll probably
 push out a standard configuration,

0:17:08.140000 --> 0:17:11.180000
 all of them saying, hey,
 access point over here.

0:17:11.180000 --> 0:17:14.520000
 Okay, your Wi-Fi network is
 going to be called payroll.

0:17:14.520000 --> 0:17:17.720000
 Access point over here, your Wi-Fi
 network is going to be called HR.

0:17:17.720000 --> 0:17:20.480000
 So it'll push that stuff down
 to the access points.

0:17:20.480000 --> 0:17:26.700000
 And then from a security perspective,
 we have the question of who is allowed

0:17:26.700000 --> 0:17:28.360000
 on the Wi-Fi network?

0:17:28.360000 --> 0:17:31.420000
 What are they allowed to do when
 they get on the Wi-Fi network?

0:17:31.420000 --> 0:17:33.740000
 The controller can
 also control that.

0:17:33.740000 --> 0:17:38.540000
 So when a client, like a laptop, a
 PC, or a tablet, first connects to

0:17:38.540000 --> 0:17:42.320000
 an access point, the access point
 might say, hey, who are you?

0:17:42.320000 --> 0:17:43.800000
 Give me your credentials.

0:17:43.800000 --> 0:17:46.460000
 Once that client provides the credentials,
 maybe just something as simple

0:17:46.460000 --> 0:17:47.600000
 as a passphrase.

0:17:47.600000 --> 0:17:51.360000
 At that point, you as a network administrator,
 you have a choice.

0:17:51.360000 --> 0:17:55.080000
 Even though that's a lightweight access
 point, you could say, hey, access

0:17:55.080000 --> 0:17:59.560000
 point, you yourself are going to be in
 charge of authenticating this client.

0:17:59.560000 --> 0:18:01.640000
 We're not going to bother
 the controller with that.

0:18:01.640000 --> 0:18:04.680000
 I'll give you the information you need
 to be able to do that yourself.

0:18:04.680000 --> 0:18:08.120000
 Or we could have the authentication
 information pass through the access

0:18:08.120000 --> 0:18:10.320000
 point and go up to the controller.


0:18:10.320000 --> 0:18:13.200000
 So that's what this saying right here,
 control Wi-Fi access for clients.

0:18:13.200000 --> 0:18:16.820000
 Maybe we want the controller to have
 the visibility of every single client

0:18:16.820000 --> 0:18:20.700000
 that's connected, what credentials they
 have supplied, how long they've

0:18:20.700000 --> 0:18:24.220000
 been connected, and variety
 of other things.

0:18:24.220000 --> 0:18:27.220000
 So you're in the market
 for a Wi-Fi controller.

0:18:27.220000 --> 0:18:30.260000
 What are some differentiators
 of those?

0:18:30.260000 --> 0:18:35.120000
 Number one, the quantity of Wi
-Fi clients that are supported.

0:18:35.120000 --> 0:18:38.420000
 Pretty much every controller that's
 out there will support at least 100

0:18:38.420000 --> 0:18:42.840000
 or so clients. But a lot of the bigger
 controllers can support tens of

0:18:42.840000 --> 0:18:45.540000
 thousands of Wi-Fi clients.

0:18:45.540000 --> 0:18:49.740000
 Clearly, the features that are available,
 and depending on who produced

0:18:49.740000 --> 0:18:53.500000
 the controller, whether it's Cisco or
 Ruba or somebody else, you'll have

0:18:53.500000 --> 0:18:55.600000
 different features available.

0:18:55.600000 --> 0:18:59.200000
 And the control you're buying is an
 appliance, or is it cloud-based?

0:18:59.200000 --> 0:19:01.460000
 An appliance would be like what we
 see here in the graphics, something

0:19:01.460000 --> 0:19:05.360000
 you can physically hold in your hands,
 you can plug a cable into, requires

0:19:05.360000 --> 0:19:07.260000
 you to plug it into
 a power source.

0:19:07.260000 --> 0:19:08.200000
 That's an appliance.

0:19:08.200000 --> 0:19:12.060000
 Cloud-based is a software
-based controller.

0:19:12.060000 --> 0:19:17.240000
 So you could actually have a controller
 residing in Amazon web services,

0:19:17.240000 --> 0:19:21.320000
 for example. You could use AWS and have
 your controller there, and it's

0:19:21.320000 --> 0:19:24.600000
 able to reach out and talk to
 all of your access points.

0:19:24.600000 --> 0:19:27.160000
 That's possible as well.

0:19:27.160000 --> 0:19:30.640000
 And the type and quantity
 of up-link interfaces.

0:19:30.640000 --> 0:19:35.100000
 So your controller is going to be physically
 connected to the wired network.

0:19:35.100000 --> 0:19:38.040000
 That's how it's going to talk
 to the Wi-Fi access points.

0:19:38.040000 --> 0:19:41.860000
 So while each access point is doing
 Wi-Fi with its clients, the access

0:19:41.860000 --> 0:19:46.280000
 point also has at least one
 wired Ethernet cable.

0:19:46.280000 --> 0:19:49.680000
 Probably a fast Ethernet, maybe a gigabit
 Ethernet cable, but that's how

0:19:49.680000 --> 0:19:53.300000
 it connects to the wired network, and
 that's the cable it uses to talk

0:19:53.300000 --> 0:19:54.840000
 to the controller.

0:19:54.840000 --> 0:19:58.240000
 So another different share of controllers
 is how many physical cables

0:19:58.240000 --> 0:19:59.460000
 can they connect to?

0:19:59.460000 --> 0:20:03.220000
 Do they have connectors for 10 gigabit,
 40 gigabit, fiber optic cables,

0:20:03.220000 --> 0:20:04.680000
 or just copper cables?

0:20:04.680000 --> 0:20:07.340000
 Those are some differentiators
 there as well.

0:20:07.340000 --> 0:20:11.700000
 So as we can see here, the three to
 sum it up, the three components of

0:20:11.700000 --> 0:20:16.620000
 a wireless LAN or a Wi-Fi network are
 your Wi-Fi stations, which is the

0:20:16.620000 --> 0:20:20.460000
 technical term for your clients, like
 your laptops, your PCs, your tablets,

0:20:20.460000 --> 0:20:21.720000
 your smartphones.

0:20:21.720000 --> 0:20:26.440000
 All those devices connect to a central
 consolidation point called an access

0:20:26.440000 --> 0:20:31.060000
 point. So at minimum, you have to have
 those two, and then optionally,

0:20:31.060000 --> 0:20:34.700000
 you could get a controller involved which
 controls and manages the access

0:20:34.700000 --> 0:20:38.100000
 points if you have a lot of
 access points to deal with.

0:20:38.100000 --> 0:20:40.520000
 So that concludes this video.

0:20:40.520000 --> 0:20:42.080000
 Thank you very much for watching.