-: In the last video, 2 2
we talked about the fact that there was Ad Hoc 3 3
and Infrastructure mode, 4 4
and I said, we'd come back to that and dig a little deeper. 5 5
Well, in this lesson, we're going to do that. 6 6
First. we have Ad Hoc mode. 7 7
Now, when we use Ad Hoc mode, 8 8
we're actually using what is called the IBSS 9 9
or the Independent Basic Server Set. 10 10
You'll notice in this diagram 11 11
that I have a wired network on the first floor 12 12
and I have two devices connecting wirelessly 13 13
to each other, on the second floor. 14 14
Notice, these two devices on the second floor 15 15
are not talking to anybody on the first floor. 16 16
They are a separate network and they are talking only 17 17
in a peer-to-peer configuration using that Ad Hoc mode. 18 18
So these devices, 19 19
because they're in an Ad Hoc mode, 20 20
have no access to the internet 21 21
and no access to the local area network. 22 22
They're operating solely in Ad Hoc mode, 23 23
in that peer-to-peer method. 24 24
Next, I want to show you what it looks like 25 25
when you have BSS, or a Basic Server Set. 26 26
Now, notice my second floor devices 27 27
are connecting wirelessly down to the wireless access point, 28 28
and the device on the first floor 29 29
is actually connecting wirelessly 30 30
to a wireless access point, as well. 31 31
Then there's a hard line cable 32 32
going between the access point and the switch. 33 33
This is how we're going to connect all of our stuff 34 34
in this small office, home office environment. 35 35
Now in your house, if you have wifi, 36 36
this is most likely what you're doing. 37 37
You have one access point that's connected to your network, 38 38
and that's how it makes a connection out to the internet. 39 39
Now, this is our first Infrastructure mode. 40 40
This is what we call the Basic Server Set. 41 41
Now, the second one we have 42 42
is what's known as an Extended Server Set or ESS. 43 43
Now, notice here because this building is so large, 44 44
I have two different wireless access points, 45 45
I have one for the first floor and one for the second floor. 46 46
Both of these access points are hardwired back using either 47 47
a Cat5 or a Cat5e cable, 48 48
to a switch on the first floor. 49 49
They're now providing service wirelessly 50 50
to their designated floor, 51 51
either the first floor or the second floor. 52 52
Now they're working in conjunction with each other 53 53
so that we have a full coverage over the entire building, 54 54
and they're all going to have the same wireless network name 55 55
when you look for it using your device. 56 56
So, if you come to my house, for instance, 57 57
we have a network called Dion. 58 58
We have several access points spread throughout the house, 59 59
operating in what's known as the Extended Server Set mode. 60 60
The reason why, is we wanted to have good coverage 61 61
for everyone in the house, no matter where they're standing. 62 62
If you're down in my basement, 63 63
or you're up on my main level, 64 64
you're still going to get good service 65 65
because of our Extended Server Set. 66 66
Now, the way you use this is through what's known as 67 67
the ESS, the Extended Server Set. 68 68
They all work together. 69 69
This gives you multiple access points 70 70
to give you good coverage across an entire building. 71 71
If you go to a large building for work, 72 72
or you go to a college campus, they use this all the time. 73 73
The reason why is, that a single access point 74 74
can only cover maybe 100 or 150 meters, 75 75
but by using multiple access points, 76 76
I can cover an entire college campus. 77 77
As long as they're all working together, 78 78
the end user just sees the one network as they roam around 79 79
the campus and move from building to building. 80 80
The next concept we need to talk about 81 81
is what's known as a Mesh Topology. 82 82
We covered this all the way back in our topology lessons, 83 83
back in the beginning of the course. 84 84
Now with a Mesh Topology, 85 85
they may not use a centralized control mechanism, 86 86
but instead it's going to combine a number of different ways 87 87
of doing wireless networks, into one manner. 88 88
So, you might use microwave, or cellular, or wifi 89 89
or any other type of wireless technology 90 90
and make one coherent network with it. 91 91
It works kind of like an ESS, 92 92
the Extended Server Set does for wifi, 93 93
but the difference here is we're not just using wifi, 94 94
we're combining other wireless mechanisms too. 95 95
So for example, 96 96
I have my laptop connecting wirelessly 97 97
to a wireless access point, 98 98
then that wireless access point connects 99 99
to a satellite connection, which is wireless 100 100
up to a satellite. 101 101
That satellite may then go up to the satellite 102 102
and down to a ground station, 103 103
and that ties back into a switch, 104 104
and then to another machine. 105 105
Now, if I look at the bottom of this diagram, 106 106
you can see where the internet is coming from. 107 107
It's connecting a wired internet 108 108
through a router, to a wireless access point. 109 109
Now there it's going into a TV and a laptop 110 110
and things like that. 111 111
Now, all of this can make up one big Mesh Topology, 112 112
as we connect through different devices using wifi, 113 113
and microwave and cellular 114 114
and other wireless technologies. 115 115
Now, if we want to take this a step further, 116 116
take a look at this diagram. 117 117
I showed you this in a smaller version back 118 118
in the Mesh Topology lesson as well, 119 119
but you can see here how we have 802.11 wifi zones, 120 120
and we have high-frequency antennas, 121 121
and high-gain antennas that cover vast distances. 122 122
We have satellite, we have microwave, 123 123
we might even have WiMAX in here. 124 124
All of this can work together to give us this perfect mesh 125 125
that covers a large range of areas, as we go through. 126 126
Now, as I mentioned before, 127 127
when we talk about Mesh Topologies, this is very popular 128 128
to use, in a disaster recovery situation. 129 129
If you lose landlines and they've gone down, 130 130
we need to start building up frequencies for us to be able 131 131
to use in a quick manner, and be responsive to a situation. 132 132
So, if there's an earthquake or a hurricane or a tornado, 133 133
the responders might come in and bring a satellite, 134 134
and a microwave link, and wifi access points, 135 135
so they can set up a network 136 136
and communicate that information back out 137 137
to the unaffected areas and get more assistance. 138 138
Next, let's talk about access point placement 139 139
because careful planning and placement 140 140
of your access points is really important 141 141
to make sure you don't have interference 142 142
and you can prevent network outage issues. 143 143
This will become very clear to you during 144 144
the troubleshooting section of this course, as well. 145 145
Your coverage area needs to have an overlap between 146 146
your different access points, 147 147
to make sure you don't have holes in your coverage 148 148
and to make sure everything is working properly. 149 149
So here on the diagram, for instance, 150 150
let's say that we have this office building 151 151
and we want to cover all of it with wifi. 152 152
Now, the way wireless radios work is that wherever 153 153
you put it, it's going to start in the center 154 154
and then access everything out, 155 155
in a circular pattern around it. 156 156
In this building, we have four different access points 157 157
that we're going to cover the entire building, 158 158
and I don't want to have any drops 159 159
as I walk from one room to another, 160 160
so, I need to have an overlap. 161 161
We want to have an overlap between the coverage zones, 162 162
but not an overlap in our frequencies. 163 163
If you know anything about radio frequencies, 164 164
you'll know that if we have two people transmitting 165 165
on the same frequency at the same time, that causes jamming 166 166
and collisions, and will drop the signal. 167 167
So if I'm using the 2.4 gigahertz spectrum, 168 168
which is used by wireless B, G and N, 169 169
we want to make sure we have an overlapping coverage 170 170
of 10 to 15 percent. 171 171
Now, as I blow up this diagram here, 172 172
you can see I have four wireless access points, 173 173
and they're all operating on channels, 1, 6 and 11. 174 174
That is going to make sure that no two circles 175 175
are touching, using the same channel frequency 176 176
because channel 1 uses a different frequency than channel 6, 177 177
and channel 6 uses a different frequency than channel 11. 178 178
Now, you'll see that channel 6 is on the left 179 179
and it's touching channel 1 and channel 11. 180 180
Channel 6 on the right, 181 181
is touching channel 1 and channel 11. 182 182
So again, I can't have channel 6 and channel 6 overlapping 183 183
because that would give me frequency issues 184 184
and we would have collisions and drop coverage. 185 185
Now, when we move into the newer spectrum of 5 gigahertz, 186 186
which is used by wireless N and wireless AC, 187 187
you're going to want to have overlapping coverage as well, 188 188
but because the way that we do this, 189 189
and there's some bleed over, 190 190
we want to make sure there's 191 191
no identical channels sitting next to each other, either. 192 192
These channels actually need to be separated 193 193
by at least two cells as you're designing your networks. 194 194
So, as we designate these cells 195 195
like a honeycomb pattern using the 5 gigahertz spectrum, 196 196
we want to make sure that we're making sure 197 197
there's at least two cells in between each of those 198 198
that have the same channel. 199 199
Now, this is different than the circles we used inside 200 200
the 2.4 gigahertz. 201 201
So if you look at my screen here, 202 202
you can see I have channel 36 in the upper-left corner, 203 203
and then you get there and you go through channel 52 204 204
and channel 54, 205 205
and then you finally come back to channel 36, again. 206 206
Notice I had at least two spots in my honeycomb 207 207
before I repeated a channel. 208 208
We have this honeycomb pattern and we keep this separation 209 209
because that's going to give us much better coverage 210 210
with no drops and no interference. 211 211
Now, when you go out and you do your site survey 212 212
and you start looking at a building, 213 213
and you start seeing where the access is, 214 214
you want to figure out where you have good coverage 215 215
and where you have bad coverage, 216 216
and you can actually produce what's known as a heat map, 217 217
and map out all those coverage zones, 218 218
and overlay it on top of your floor plan. 219 219
Now, in this example, we have a building 220 220
and you've seen that I've done a wireless survey 221 221
to determine my coverage areas. 222 222
Where it's blue, that's where the access point is, 223 223
and the blue is a really, really strong signal. 224 224
Green is a good signal. 225 225
Yellow is getting a little weaker 226 226
and red means I'm really weak, or out of signal. 227 227
Now there's a couple of offices in there 228 228
and in the middle of the diagram, 229 229
there's a red coverage area. 230 230
If I wanted to improve that, 231 231
I would move another access point into that region, 232 232
but overall, this has pretty good coverage, 233 233
except for that stairwell in the center of the screen. 234 234
Now you'll notice outside the building, 235 235
we do have red as well. 236 236
Now that's actually a good thing from security 237 237
because I don't want a lot of signal bleed 238 238
going outside of my building. 239 239
Now, what is considered a bad thing here? 240 240
Well, if you look in the bottom-center of the diagram, 241 241
we have green, yellow, and orange in the parking lot. 242 242
That means if I drove into this parking lot, 243 243
I could connect to your building's wireless network. 244 244
Now that's not necessarily a good thing, 245 245
and that's bad from a security standpoint 246 246
and I'd have to think about that as I'm building out my map. 247 247
and so maybe I want to take that access point 248 248
and move it a little bit more towards 249 249
the center of the building, and that will help alleviate 250 250
and bring some more red spots on the outside of the building 251 251
and alleviate those red spots 252 252
that were in the inside of the building. 253 253
We'll talk more about that as we go into wireless security, 254 254
later on in the course, 255 255
but for the time being, I want you to remember 256 256
that if you do a site survey, you may produce a heat map 257 257
that shows where your hotspots are, 258 258
where you have good coverage inside of a building 259 259
and where you have weak coverage, 260 260
and you can move your access points around 261 261
to give you a better coverage map. 262 262
Now, what is another great way 263 263
to get additional coverage, besides implementing something 264 264
like ESS with the Extended Server Set model. 265 265
Well, if you don't want to put up a full access point, 266 266
you can get what's called a Range Extender. 267 267
Now, what a range extender is, 268 268
is a specialized device that helps you overcome some 269 269
of your distance limitations. 270 270
Essentially it has a receiver and a transmitter, 271 271
and it's going to receive in the wireless signal 272 272
that's already there 273 273
and then transmit it out the other side, 274 274
as it does this, it's going to amplify your signal 275 275
and extend the reach of that wireless signal. 276 276
These are very small devices 277 277
and all you need to do is plug them into the wall 278 278
for them to work. 279 279
For instance, here, 280 280
you see the net gear displayed on the screen 281 281
and it has two antennas. 282 282
One of those is for listening 283 283
and one of those is for sending out the information. 284 284
If you have a large house 285 285
and your router is down in your basement, 286 286
you can actually use a wireless access point 287 287
down in the basement, 288 288
and then you might put one of these range extenders 289 289
in the stairs, to get that signal up into the second floor. 290 290
This can actually get your signal from the basement 291 291
and rebroadcast it upstairs like I said, 292 292
and essentially this becomes a wireless repeater. 293 293
Just like we would use an active hub 294 294
to repeat our signal on a cable and make it go further, 295 295
we can use a wireless range extender 296 296
to repeat our wireless signal 297 297
and give us additional range too.