- Implementing wireless security
- Threats to your wireless network
- Wi-Fi Protected Setup
- Installing a wireless network
- Cloud ownership and implementation
- Creating a virtual machine
- PaaS, SaaS, and IaaS
- Mobile networking
- Deploying mobile devices
Skill Level Beginner
- From my laptop to my smartphone, to my thermostat, to the Alexa in my living room, the world of wireless is here and it's been here forever. You get on airplanes and get on wireless these days. In this episode, what we wanna talk about is the standard that we use for wireless called 802.11. The 802.11 is the standard. When most people talk about, "I'm gonna get on Wi-Fi," or you're firing something up and you're looking for a network, that's what we're talking about when we say 802.11.
Now, the 802.11 standard has been around since the late 1990s. And it's gone through all kinds of changes and updates and all kinds of stuff. However, the core standard, which is what we're gonna cover in this episode, doesn't matter. So, if you're familiar with things like 802.11b or 802.11n or 802.11ac, we'll cover that another episode. Everything I talk about in this works for every version of 802.11. So, this is kinda like a overview to get us started into what 802.11 is.
802.11 uses radio waves to transmit network information between individual wireless nodes. Now, when we're talking about 802.11, pretty much everything starts off with something called a Wireless Access Point, or a WAP. And I've got a few of them right here. So, here's a really old Wireless Access Point. What we have are some antennas that are sending and receiving radio data. And it is a bridging device that bridges into an Ethernet network.
Say we've got an RJ45, and this guy plugs into my Ethernet network. He gets an IP address just like anything else on my network, but then he also speaks via radio waves to my wireless clients. Here's another example of a Wireless Access Point. Notice he's just got one RJ45 connection. All WAPs will normally, I'm sure there's an exception somewhere, have a single RJ45 connection. Now, the thing you gotta be careful about here is that the world is filled with devices that look like this.
I'm gonna hold it upside down so it's a little bit better lit. And what we have here is a typical home router. A home router is, we've got some switch ports in there, we've got an Internet connection. So, really what you're looking at here, folks, this is a Wireless Access Point. But it's also a switch, and it's also a router. This is a device that does all kinds of stuff all wrapped in one. So, you need to be careful when we talk about Wireless Access Points. There is a WAP in here, but there's a lot of other stuff as well.
So, don't go calling me up and say, "Mike, I have a WAP that has more than one RJ45." No, you have a router that also has a WAP built into it. So, the cornerstone of everything that makes 802.11 work is the concept of what's called as a Service Set Identifier, or an SSID. In the 802.11 world, in order to make the radio work you go into these devices one way or another and you set an SSID.
An SSID is a word or a term or a phrase that this device will then normally just broadcast out. And then as a client, I can try to log into that. And anybody who's ever looked at your laptop or your smartphone trying to get on a wireless network, what you're actually looking at there are SSIDs. Now, there's two ways to go about this. The first way to go about it, and by far the most common way, is what we call infrastructure mode. 802.11 infrastructure mode just means I'm using a Wireless Access Point.
That's all it means. So, if you're using a Wireless Access Point, you're using infrastructure mode. There is another way to do it called ad hoc mode. With ad hoc mode, you can set up, and most operating systems support this, you can just fire up your Windows laptop. And instead of looking for a network, you can basically go I'm going to start an ad hoc network and I'm gonna call it Mike's Temporary Network, Enter. And now other laptops, other smartphones, and what else can connect into you. So, ad hoc is a really common way if you need to do a quick ad hoc network, and that works great.
But most of the time for the serious heavy lifting of 802.11 we install a Wireless Access Point, configure it with an SSID, and off we go. Okay. Now, if you have a single WAP with a single SSID, you have what's known as a Basic Service Set Identifier, or a BSSID. Which is kinda cool because with 802.11 it is built from the ground up to support multiple WAPs that are working together.
So, I could if I wanted to grab one of these WAPs and then grab two or three more, plug them into the same switch, and as long as I give them each the same SSID name, the exact same name, all I have to do is type in the name, hit Enter, and these devices will start working with each other automatically. There's nothing I have to set up or configure. They'll do cool things like, for example, if somebody's really close to this Wireless Access Point, they'll connect to him. But as they walk away and get closer to another, they will automatically hand you off.
There's not even anything to set up or configure, it just works. One of the beautiful reasons that we love 802.11 so much. So, when you have lots of Wireless Access Points that are all working together and all their RJ45s are plugged into a common switch, a common broadcast domain, you have created what we call an Extended Service Set Identifier, or ESSID. Now, all 802.11 are designed to run within the industrial, scientific, and medical bands, the ISM bands.
Now, there's a number of bands, but the two that we use for any version of 802.11 is gonna be the 2.4 gigahertz band and the five gigahertz band. Now, when we say a band, we're talking about a range of frequencies. So, kinda like changing the channel on your television. You've got a band of frequencies and we chop it up into preset what we call channels. And these channels are individual frequencies. In order for my Wireless Access Point to talk to my client, I'm gonna have to go in and make sure that we're talking on the same channel.
Now, in other episodes we'll go into a lot more detail on this, but the 2.4 gigahertz band has a number of channels, one through eleven, we'll talk about this more later. And the five gigahertz band has a bazillion channels with numbers like 100 and 400 and 500. They go way up there. The nice part about all this is that, for the most part, our wireless client talks to this and they negotiate a channel and they stick to it. There's nothing for us to set. There's some situations where that might come into play. So, we've been talking about the Wireless Access Points.
I wanna talk about the clients for a minute. So, let me put up a bunch of pictures to help you understand what type of devices, the hardware, sits on the client side. So, let's start with this picture here. This is an old school wireless network card. It snaps into a slot on a desktop system. And you can see it has antennas. And this guy we can configure and that will allow that desktop system to act as a client. We can also see USB-based wireless NICs.
Here's an example of one that you just plug into a USB port and it allows that particular device to become a wireless client. Laptops pretty much have wireless built into them. Here's a picture of a laptop, and I've actually opened the bottom up. And you can really see the actual wireless NIC that's built into the laptop. And if you look very carefully, you can even see the antenna connections for that particular little tiny wireless device. But it doesn't stop there.
Take a look at, say for example, your common smartphone. All smartphones are wireless clients, so they have to have a wireless NIC built into them. They're usually just built so much into the actual smartphone itself, you don't see it. Same with tablets. Even things like my cameras today, my Nest thermostat that I use at my house. These are all wireless clients, they all have radios built into them with antennas that are designed to find these Wireless Access Points.
Alright. Now, if I'm gonna have these guys talking, one of the challenges we run into is how do we get radio signals from a client to a Wireless Access Point and back? I mean, anybody who's tuned in on an old AM radio can appreciate that it, you get all kinds of interference and problems like that. So, what we do in the world of 802.11 is we lean very heavily on something called Carrier-Sense Multiple Access Collision Avoidance.
Now, don't confuse that with the old Ethernet Carrier-Sense Multiple Access Collision Detection. With Carrier-Sense Multiple Access Collision Avoidance, what happens is that if I have a wireless client, he's not gonna send anything until he knows the coast is clear. So, with 802.11, they're always gonna use CSMA. There's never a collision with CSMA because they avoid each other and they have what's called a backoff time. They'll wait a few extra milliseconds before they resend data.
The actual transmission of the data itself comes in one of two forms. There's an old form called Digital Sequence Spread Spectrum. So, DSSS is kind of the original way we used to do this. And what would happen with this is that even within that channel, there's even more sub-frequencies. And we could spread a signal across these, and in the hopes that if one gets stopped for interference that another one would get through. Today, the primary way we do it is using something called OFDM, Orthogonal Frequency-Division Multiplexing.
In this particular case, we still are using a type of spread spectrum, but it can be in a much wider range. The channels, particularly in the five gigahertz band, can be very, very wide, which allows these guys to do a lot of variance in there. The nice part about DSSS or OFDM is that you don't set this. You just pick a particular type of 802.11, say 802.11ac, and that's already picked for you. The exam is curious about this stuff, and in other episodes I will break this down in a per type of 802.11 so you'll know all the answers for it.
So, that's the basics of 802.11. There's a lot more to do here, but the important thing is is that no matter what version of 802.11 that you're running, you will always have a WAP if you're running infrastructure mode. You will always have a client. You will always have at least an SSID. You're gonna be using one of two different ISM bands. And you're gonna be using some type of technology to get the data from the client to the WAP and back.