WEBVTT 1 00:00:00.360 --> 00:00:01.470 Now up to this point 2 00:00:01.470 --> 00:00:03.270 I've mentioned a few wireless standards 3 00:00:03.270 --> 00:00:06.390 like B and G, N, and AC. 4 00:00:06.390 --> 00:00:09.150 Next I'm going to provide you with a nice little summary chart 5 00:00:09.150 --> 00:00:11.340 that's going to cover all the wireless networking standards 6 00:00:11.340 --> 00:00:13.380 that you need to memorize for the exam. 7 00:00:13.380 --> 00:00:15.750 This is one that I would print out and memorize. 8 00:00:15.750 --> 00:00:19.200 You need to know the standard and you need to know the band, 9 00:00:19.200 --> 00:00:21.540 and you need to know the maximum bandwidth. 10 00:00:21.540 --> 00:00:24.450 These three pieces of information are very important. 11 00:00:24.450 --> 00:00:26.400 Now, when we started out with wireless networks 12 00:00:26.400 --> 00:00:28.440 all the way back in the early 1990s, 13 00:00:28.440 --> 00:00:31.350 we only had the 802.11 standard. 14 00:00:31.350 --> 00:00:33.750 This standard though, was not commercially viable. 15 00:00:33.750 --> 00:00:35.940 It was essentially a big proof of concept. 16 00:00:35.940 --> 00:00:38.160 It didn't really make it into the marketplace. 17 00:00:38.160 --> 00:00:40.830 It operated in the 2.4 gigahertz spectrum, 18 00:00:40.830 --> 00:00:42.060 but it only operated 19 00:00:42.060 --> 00:00:44.640 at about one to two megabits per second. 20 00:00:44.640 --> 00:00:45.630 Now, for your chart, 21 00:00:45.630 --> 00:00:48.120 I wouldn't even bother writing that one down. 22 00:00:48.120 --> 00:00:50.010 Instead, you need to know about 23 00:00:50.010 --> 00:00:55.010 A, B, G, N, AC and AX for our exam. 24 00:00:55.530 --> 00:00:57.960 Those six Wi-Fi types are the ones you need to memorize 25 00:00:57.960 --> 00:01:00.990 for the exam with those three pieces of critical information 26 00:01:00.990 --> 00:01:02.940 to make sure you're successful on the exam 27 00:01:02.940 --> 00:01:04.770 for wireless networking questions. 28 00:01:04.770 --> 00:01:06.480 Let's talk about each one now. 29 00:01:06.480 --> 00:01:10.350 First, let's talk about Wireless A or 802.11a. 30 00:01:10.350 --> 00:01:12.630 This operated in the 5 gigahertz spectrum, 31 00:01:12.630 --> 00:01:13.980 which was a very expensive radio 32 00:01:13.980 --> 00:01:16.200 to build and manufacturer at that time, 33 00:01:16.200 --> 00:01:18.630 but it did give us a good amount of speed 34 00:01:18.630 --> 00:01:21.540 because it operated at 54 megabits per second. 35 00:01:21.540 --> 00:01:23.760 This was really good in the late nineties, 36 00:01:23.760 --> 00:01:26.520 but again, unfortunately it cost a lot of money. 37 00:01:26.520 --> 00:01:27.960 Because of that high cost 38 00:01:27.960 --> 00:01:30.030 only business users really ended up using it, 39 00:01:30.030 --> 00:01:32.040 and it wasn't really that commercially viable 40 00:01:32.040 --> 00:01:33.600 in the mainstream market. 41 00:01:33.600 --> 00:01:35.370 Now, since it wasn't getting as much traction 42 00:01:35.370 --> 00:01:36.600 in the commercial markets, 43 00:01:36.600 --> 00:01:39.090 they decided to make something cheaper and easier, 44 00:01:39.090 --> 00:01:42.000 so the manufacturers decided to create Wireless B, 45 00:01:42.000 --> 00:01:44.730 which operates in the 2.4 gigahertz spectrum. 46 00:01:44.730 --> 00:01:46.770 Now, this frequency range is commonly used 47 00:01:46.770 --> 00:01:48.720 by a lot of other household devices, 48 00:01:48.720 --> 00:01:51.030 things like security cameras, walkie-talkies, 49 00:01:51.030 --> 00:01:53.550 baby monitors, microwaves, and more. 50 00:01:53.550 --> 00:01:56.670 Now, this made the radios in the 802.11b wireless devices 51 00:01:56.670 --> 00:01:58.290 very cheap and easy to get, 52 00:01:58.290 --> 00:02:01.680 and it led to widespread adoption of Wi-Fi throughout homes, 53 00:02:01.680 --> 00:02:04.710 businesses, and schools, bringing us to where we are today. 54 00:02:04.710 --> 00:02:06.600 Now using this cheaper chipset 55 00:02:06.600 --> 00:02:07.980 and the way the frequencies worked 56 00:02:07.980 --> 00:02:09.660 actually slowed down our networks, 57 00:02:09.660 --> 00:02:11.730 so we went from 54 megabits per second 58 00:02:11.730 --> 00:02:13.800 down to 11 megabits per second, 59 00:02:13.800 --> 00:02:16.080 which today sounds extremely slow, 60 00:02:16.080 --> 00:02:18.840 but again, we're talking about the late 1990s here. 61 00:02:18.840 --> 00:02:20.490 We weren't doing a lot of streaming video, 62 00:02:20.490 --> 00:02:23.130 and so 11 megabits per second was actually fast enough 63 00:02:23.130 --> 00:02:24.810 for most home users. 64 00:02:24.810 --> 00:02:27.120 Now, over time though, networks got faster 65 00:02:27.120 --> 00:02:28.380 and we wanted more speed, 66 00:02:28.380 --> 00:02:32.160 and so Wireless G came out as a replacement for Wireless B. 67 00:02:32.160 --> 00:02:36.930 Now, wireless 802.11g is also in the 2.4 gigahertz spectrum, 68 00:02:36.930 --> 00:02:40.020 but it operates at 54 megabits per second. 69 00:02:40.020 --> 00:02:42.570 Now, eventually we wanted to go even faster than this, 70 00:02:42.570 --> 00:02:44.520 so engineers kept working on new solutions 71 00:02:44.520 --> 00:02:46.590 and new ways to manipulate the frequencies, 72 00:02:46.590 --> 00:02:48.900 and eventually they came up with Wireless N, 73 00:02:48.900 --> 00:02:51.090 which is also called Wi-Fi 4 74 00:02:51.090 --> 00:02:53.580 since it was the fourth generation of Wi-Fi. 75 00:02:53.580 --> 00:02:56.610 Now 802.11n really wanted to increase speed, 76 00:02:56.610 --> 00:02:59.190 so moved back to the 5 gigahertz spectrum again. 77 00:02:59.190 --> 00:03:00.480 And this allowed it to get up to speeds 78 00:03:00.480 --> 00:03:03.450 of 300 to 600 megabits per second. 79 00:03:03.450 --> 00:03:05.520 This allowed for really fast networks, 80 00:03:05.520 --> 00:03:06.960 but the big problem 81 00:03:06.960 --> 00:03:09.000 is that this newer 5 gigahertz spectrum 82 00:03:09.000 --> 00:03:11.190 wasn't compatible with all the existing devices 83 00:03:11.190 --> 00:03:12.023 that were out there 84 00:03:12.023 --> 00:03:13.650 because they were Wireless B and G, 85 00:03:13.650 --> 00:03:15.930 and they operate at 2.4 gigahertz. 86 00:03:15.930 --> 00:03:19.500 So people were resistant to buying Wireless N at first. 87 00:03:19.500 --> 00:03:20.640 Now, to overcome this, 88 00:03:20.640 --> 00:03:23.040 manufacturers started making hybrid devices 89 00:03:23.040 --> 00:03:25.470 that were marketed under the name Wireless N, 90 00:03:25.470 --> 00:03:28.020 and these type of devices had a wireless access point 91 00:03:28.020 --> 00:03:29.880 with two sets of radios in them. 92 00:03:29.880 --> 00:03:32.160 One was for the 2.4 gigahertz spectrum 93 00:03:32.160 --> 00:03:34.500 and one for the 5 gigahertz spectrum. 94 00:03:34.500 --> 00:03:36.450 This way, if you had a mixture of devices 95 00:03:36.450 --> 00:03:39.270 that were 802.11b and G and N, 96 00:03:39.270 --> 00:03:42.210 you could connect to the slower 2.4 gigahertz spectrum, 97 00:03:42.210 --> 00:03:44.760 and it would support Wireless B speeds, Wireless G speeds 98 00:03:44.760 --> 00:03:46.500 or newer Wireless N speeds, 99 00:03:46.500 --> 00:03:49.200 that went up to about 150 megabits per second. 100 00:03:49.200 --> 00:03:50.460 Now, if someone connected 101 00:03:50.460 --> 00:03:52.530 to the more modern Wireless N radios 102 00:03:52.530 --> 00:03:54.450 using the 5 gigahertz spectrum, 103 00:03:54.450 --> 00:03:55.590 they could actually reach speeds 104 00:03:55.590 --> 00:03:57.960 up to 600 megabits per second 105 00:03:57.960 --> 00:04:00.480 by using a technology known as MIMO. 106 00:04:00.480 --> 00:04:03.180 MIMO stands for multiple input and multiple output, 107 00:04:03.180 --> 00:04:04.470 which means that the access point 108 00:04:04.470 --> 00:04:07.350 could use multiple antennas to send and receive data 109 00:04:07.350 --> 00:04:09.720 instead of putting it all through a single antenna. 110 00:04:09.720 --> 00:04:11.700 Essentially, your data was going to be split 111 00:04:11.700 --> 00:04:14.580 across multiple antennas and was received on the other end, 112 00:04:14.580 --> 00:04:16.980 it was multiplexed back into a single data stream 113 00:04:16.980 --> 00:04:18.150 for processing. 114 00:04:18.150 --> 00:04:20.550 This is why you can see Wireless N access points 115 00:04:20.550 --> 00:04:23.880 that have one, two, three, or even 5 antennas 116 00:04:23.880 --> 00:04:25.350 because the more antennas you had, 117 00:04:25.350 --> 00:04:28.560 the more data transfer they could support simultaneously. 118 00:04:28.560 --> 00:04:30.480 Next, we have Wireless AC, 119 00:04:30.480 --> 00:04:34.980 which is also called Wi-Fi 5 or 802.11ac. 120 00:04:34.980 --> 00:04:37.320 This was the fifth generation of Wi-Fi. 121 00:04:37.320 --> 00:04:39.690 Now, Wireless AC operates exclusively 122 00:04:39.690 --> 00:04:41.370 in the 5 gigahertz spectrum, 123 00:04:41.370 --> 00:04:43.230 and technically it does not provide 124 00:04:43.230 --> 00:04:45.150 any kind of backward compatibility. 125 00:04:45.150 --> 00:04:47.400 These 802.11ac networks 126 00:04:47.400 --> 00:04:51.330 can operate at speeds up to 6.9 gigabits per second or more. 127 00:04:51.330 --> 00:04:54.180 These networks are really fast in theory. 128 00:04:54.180 --> 00:04:56.040 Now to achieve these higher speeds, 129 00:04:56.040 --> 00:05:01.040 802.11ac networks uses a technology known as MU-MIMO, 130 00:05:01.050 --> 00:05:04.200 which is multiple user multiple input multiple output. 131 00:05:04.200 --> 00:05:06.630 It's a newer variation of the MIMO technology 132 00:05:06.630 --> 00:05:10.170 that was first developed back with 802.11n networks. 133 00:05:10.170 --> 00:05:12.660 Now, MU-MIMO is a multi-path 134 00:05:12.660 --> 00:05:14.370 wireless communication technology 135 00:05:14.370 --> 00:05:17.010 that allows multiple users to access the wireless network 136 00:05:17.010 --> 00:05:19.350 and access point at the same time. 137 00:05:19.350 --> 00:05:21.240 This is different than a regular MIMO 138 00:05:21.240 --> 00:05:23.760 where a single user support it at one time 139 00:05:23.760 --> 00:05:25.980 and the access point switches between users 140 00:05:25.980 --> 00:05:28.170 to share the bandwidth across all the users 141 00:05:28.170 --> 00:05:29.640 who are requesting services. 142 00:05:29.640 --> 00:05:31.740 So if you only have one person requesting services, 143 00:05:31.740 --> 00:05:33.210 they get a really fast network, 144 00:05:33.210 --> 00:05:35.400 but if you have two or three, it starts slowing down 145 00:05:35.400 --> 00:05:37.050 because you have to share the bandwidth. 146 00:05:37.050 --> 00:05:38.520 Essentially, with MIMO, 147 00:05:38.520 --> 00:05:40.800 the wireless network acts more like a hub, 148 00:05:40.800 --> 00:05:43.680 but with MU-MIMO, it begins to act more like a switch 149 00:05:43.680 --> 00:05:46.260 and helps avoid collisions and congestion. 150 00:05:46.260 --> 00:05:48.090 Now, when it comes to Wireless AC, 151 00:05:48.090 --> 00:05:50.640 some of the original and older AC devices 152 00:05:50.640 --> 00:05:53.160 actually still use the older MIMO technology, 153 00:05:53.160 --> 00:05:55.140 whereas the newer Wireless AC devices 154 00:05:55.140 --> 00:05:57.780 will use the MU-MIMO for faster speeds. 155 00:05:57.780 --> 00:05:59.610 Now, this brings us to the latest generation 156 00:05:59.610 --> 00:06:03.000 of wireless networks, 802.11ax. 157 00:06:03.000 --> 00:06:05.760 Wireless AX is known as Wi-Fi 6 158 00:06:05.760 --> 00:06:08.520 because it's the sixth generation of wireless networks. 159 00:06:08.520 --> 00:06:10.650 This was introduced in 2021, 160 00:06:10.650 --> 00:06:12.570 and it can be used in the 2.4 gigahertz 161 00:06:12.570 --> 00:06:16.560 and 5 gigahertz spectrum under the marketing term Wi-Fi 6 162 00:06:16.560 --> 00:06:19.800 or in the newer and faster 6 gigahertz spectrum 163 00:06:19.800 --> 00:06:22.440 under the marketing term Wi-Fi 6E 164 00:06:22.440 --> 00:06:24.540 or high efficiency Wi-Fi. 165 00:06:24.540 --> 00:06:27.510 Now, these Wi-Fi 6 and Wi-Fi 6E networks, 166 00:06:27.510 --> 00:06:29.670 these 802.11ax networks, 167 00:06:29.670 --> 00:06:33.270 can reach speeds up to 9.6 gigabits per second 168 00:06:33.270 --> 00:06:35.490 using MU-MIMO technology. 169 00:06:35.490 --> 00:06:37.410 Also, because these access points 170 00:06:37.410 --> 00:06:38.910 have both the 2.4 gigahertz 171 00:06:38.910 --> 00:06:40.860 and 5 gigahertz radios inside them, 172 00:06:40.860 --> 00:06:43.770 they're fully backwards compatible with all devices, 173 00:06:43.770 --> 00:06:48.660 including Wireless A, B, G, N, and AC. 174 00:06:48.660 --> 00:06:50.130 All right, for the exam, 175 00:06:50.130 --> 00:06:51.150 I want you to remember 176 00:06:51.150 --> 00:06:53.100 there are different wireless networks out there. 177 00:06:53.100 --> 00:06:58.080 These include A, B, G, N, AC, and AX. 178 00:06:58.080 --> 00:06:59.250 You also need to remember 179 00:06:59.250 --> 00:07:02.520 that if it's A, B, G, N, or AX network, 180 00:07:02.520 --> 00:07:05.610 it's going to support 2.4 gigahertz as a spectrum. 181 00:07:05.610 --> 00:07:08.220 If it's A, N, AC, or AX, 182 00:07:08.220 --> 00:07:10.830 it supports 5 gigahertz as a spectrum. 183 00:07:10.830 --> 00:07:12.780 You also need to remember the relative speeds 184 00:07:12.780 --> 00:07:14.580 of these different wireless devices 185 00:07:14.580 --> 00:07:17.280 going from 11 megabits per second for Wireless B, 186 00:07:17.280 --> 00:07:18.930 all the way up to the gigabits per second 187 00:07:18.930 --> 00:07:21.690 used in AC and AX networks. 188 00:07:21.690 --> 00:07:23.250 This is important for the exam 189 00:07:23.250 --> 00:07:26.520 because on Test A, you may get questions about frequencies, 190 00:07:26.520 --> 00:07:28.260 things like which of these frequencies 191 00:07:28.260 --> 00:07:30.270 do not support 5 gigahertz, 192 00:07:30.270 --> 00:07:32.880 and the answer would have to be either B or G 193 00:07:32.880 --> 00:07:34.980 for Wireless B and Wireless G. 194 00:07:34.980 --> 00:07:37.080 Now you may get a question asking you to select 195 00:07:37.080 --> 00:07:39.900 which wireless standard doesn't support 2.4 gigahertz, 196 00:07:39.900 --> 00:07:40.740 and in this case, 197 00:07:40.740 --> 00:07:43.890 you'd need to select Wireless A or Wireless AC. 198 00:07:43.890 --> 00:07:45.900 If they wanted to make it more difficult for you, 199 00:07:45.900 --> 00:07:46.890 They can ask the question 200 00:07:46.890 --> 00:07:48.780 as more of a troubleshooting scenario. 201 00:07:48.780 --> 00:07:51.420 For example, you are working as a network technician 202 00:07:51.420 --> 00:07:52.680 on an older laptop, 203 00:07:52.680 --> 00:07:55.380 and it's failing to connect to your Wireless AC network. 204 00:07:55.380 --> 00:07:56.700 You check the laptop and see 205 00:07:56.700 --> 00:07:58.680 that it has a Wireless B network card. 206 00:07:58.680 --> 00:07:59.940 What is the problem? 207 00:07:59.940 --> 00:08:00.990 Then you're going to find the answer 208 00:08:00.990 --> 00:08:02.400 that has something to do with the fact 209 00:08:02.400 --> 00:08:03.990 that there's a frequency mismatch 210 00:08:03.990 --> 00:08:06.570 because Wireless AC supports 5 gigahertz 211 00:08:06.570 --> 00:08:09.090 and Wireless B supports 2.4 gigahertz 212 00:08:09.090 --> 00:08:11.520 and therefore you can't connect to the network. 213 00:08:11.520 --> 00:08:13.920 Now, one more thing to keep in mind as you're studying 214 00:08:13.920 --> 00:08:16.410 is that marketers sometimes mislabel things 215 00:08:16.410 --> 00:08:18.210 to make it easier for our consumers, 216 00:08:18.210 --> 00:08:21.510 but on test day, you have to go by the official standards. 217 00:08:21.510 --> 00:08:23.970 A great example of this is Wireless AC, 218 00:08:23.970 --> 00:08:26.280 the 802.11ac standard. 219 00:08:26.280 --> 00:08:27.960 It only specifies operation 220 00:08:27.960 --> 00:08:30.060 in the 5 gigahertz frequency band, 221 00:08:30.060 --> 00:08:31.860 but if you go to the store, 222 00:08:31.860 --> 00:08:34.140 and you find a Wireless AC access point, 223 00:08:34.140 --> 00:08:35.100 the box will tell you 224 00:08:35.100 --> 00:08:38.430 it supports both 5 gigahertz and 2.4 gigahertz. 225 00:08:38.430 --> 00:08:41.340 This is a lie, and you will get in trouble on the exam 226 00:08:41.340 --> 00:08:42.630 if you pick this answer 227 00:08:42.630 --> 00:08:45.090 because you think it's dual band, and it's not. 228 00:08:45.090 --> 00:08:46.980 The truth is Wireless AC 229 00:08:46.980 --> 00:08:49.710 only operates in the 5 gigahertz spectrum. 230 00:08:49.710 --> 00:08:50.543 When you're buying 231 00:08:50.543 --> 00:08:52.470 that Wireless AC access point at the store, 232 00:08:52.470 --> 00:08:54.510 and it says it supports both frequencies, 233 00:08:54.510 --> 00:08:57.840 it's actually a wireless access point with two radios in it. 234 00:08:57.840 --> 00:09:00.630 One radio is 5 gigahertz for Wireless AC 235 00:09:00.630 --> 00:09:03.720 at speeds up to about 1300 megabits per second. 236 00:09:03.720 --> 00:09:07.200 The other one is a 2.4 gigahertz radio for Wireless N 237 00:09:07.200 --> 00:09:09.600 at speeds of up to 600 megabits per second 238 00:09:09.600 --> 00:09:11.820 with a MIMO antenna configuration. 239 00:09:11.820 --> 00:09:14.700 Now while in real life, your users really don't care 240 00:09:14.700 --> 00:09:17.250 and they just say, hey, I have a wireless AC access point, 241 00:09:17.250 --> 00:09:18.930 and they think it supports both 5 gigahertz 242 00:09:18.930 --> 00:09:20.400 and 2.4 gigahertz, 243 00:09:20.400 --> 00:09:22.800 on the exam you will get the question wrong 244 00:09:22.800 --> 00:09:26.160 if you select 2.4 gigahertz for Wireless AC. 245 00:09:26.160 --> 00:09:29.430 Remember, Wireless AC only supports 5 gigahertz 246 00:09:29.430 --> 00:09:30.930 for its operations. 247 00:09:30.930 --> 00:09:32.700 The only dual band standards we have 248 00:09:32.700 --> 00:09:35.340 are Wireless N and Wireless AX. 249 00:09:35.340 --> 00:09:38.100 Both of those support both 2.4 gigahertz 250 00:09:38.100 --> 00:09:42.330 and 5 gigahertz frequency bands per the 802.11 standards. 251 00:09:42.330 --> 00:09:45.180 Now let's talk about radio frequency interference 252 00:09:45.180 --> 00:09:47.250 or RFI for a minute here. 253 00:09:47.250 --> 00:09:49.080 Radio frequency interference is caused 254 00:09:49.080 --> 00:09:51.390 when there are similar frequencies to wireless networks 255 00:09:51.390 --> 00:09:52.620 in your area. 256 00:09:52.620 --> 00:09:54.360 For example, I mentioned earlier 257 00:09:54.360 --> 00:09:57.990 that one of the reasons we went to 2.4 gigahertz for Wi-Fi B 258 00:09:57.990 --> 00:09:59.880 was the fact that there was other radios out there 259 00:09:59.880 --> 00:10:00.810 that already used it. 260 00:10:00.810 --> 00:10:03.150 Things like baby monitors and cordless phones 261 00:10:03.150 --> 00:10:05.820 and microwave ovens and other security devices. 262 00:10:05.820 --> 00:10:07.860 Now, this means that 2.4 gigahertz 263 00:10:07.860 --> 00:10:10.050 as a spectrum is fairly crowded. 264 00:10:10.050 --> 00:10:11.760 This is what made the radios cheap, 265 00:10:11.760 --> 00:10:13.800 but it made it very difficult for us 266 00:10:13.800 --> 00:10:15.900 because it causes a lot of interference. 267 00:10:15.900 --> 00:10:17.640 Over time, as more and more devices 268 00:10:17.640 --> 00:10:19.590 moved into the 5 gigahertz spectrum, 269 00:10:19.590 --> 00:10:22.290 there's also more interference in that area too. 270 00:10:22.290 --> 00:10:24.390 All these other electronics can cause interference 271 00:10:24.390 --> 00:10:26.010 with your wireless networks, 272 00:10:26.010 --> 00:10:27.600 so you have to think about these things 273 00:10:27.600 --> 00:10:28.830 as you're developing your networks 274 00:10:28.830 --> 00:10:30.510 and troubleshooting your networks. 275 00:10:30.510 --> 00:10:31.343 For example, 276 00:10:31.343 --> 00:10:34.380 if you have a 2.4 gigahertz Wireless G network in use 277 00:10:34.380 --> 00:10:35.460 and the access point happens 278 00:10:35.460 --> 00:10:37.290 to be sitting in the break room at the office 279 00:10:37.290 --> 00:10:39.000 and every time somebody turns on the microwave 280 00:10:39.000 --> 00:10:41.430 to reheat their burrito, the network drops, 281 00:10:41.430 --> 00:10:44.160 this is probably because the 2.4 gigahertz frequency 282 00:10:44.160 --> 00:10:46.560 is being interfered with by those microwaves 283 00:10:46.560 --> 00:10:49.200 that are operating in that same frequency band. 284 00:10:49.200 --> 00:10:51.330 In addition to all this frequency interference, 285 00:10:51.330 --> 00:10:53.970 you might also see things like physical interference. 286 00:10:53.970 --> 00:10:55.110 This is where physical things 287 00:10:55.110 --> 00:10:56.970 can block your wireless signals. 288 00:10:56.970 --> 00:10:58.770 For instance, I live in Puerto Rico 289 00:10:58.770 --> 00:11:01.710 and the walls in my house are solid concrete. 290 00:11:01.710 --> 00:11:03.960 I also have a refrigerator inside my kitchen. 291 00:11:03.960 --> 00:11:06.600 I have kitchen cabinets and those block the signal. 292 00:11:06.600 --> 00:11:09.330 All these things can cause signal strength issues for you. 293 00:11:09.330 --> 00:11:10.890 If your signals are too weak, 294 00:11:10.890 --> 00:11:12.090 and it can't make it around a corner 295 00:11:12.090 --> 00:11:14.910 or through a wall, that signal is going to get blocked, 296 00:11:14.910 --> 00:11:17.700 or it suffers what's known as attenuation. 297 00:11:17.700 --> 00:11:19.560 All of these things can lead to interference, 298 00:11:19.560 --> 00:11:21.180 which will slow down your ability 299 00:11:21.180 --> 00:11:23.490 for your network to operate at top speed. 300 00:11:23.490 --> 00:11:25.290 As your signal decreases in strength 301 00:11:25.290 --> 00:11:27.240 or interference increases, 302 00:11:27.240 --> 00:11:29.730 we get a worse signal-to-noise ratio. 303 00:11:29.730 --> 00:11:31.920 This is going to cause additional retransmissions 304 00:11:31.920 --> 00:11:35.040 because most of the time we're sending things over TCP. 305 00:11:35.040 --> 00:11:36.690 When TCP retransmits, 306 00:11:36.690 --> 00:11:38.640 this creates additional network baggage 307 00:11:38.640 --> 00:11:41.010 that's being taken up and bandwidth that's being used 308 00:11:41.010 --> 00:11:42.660 for all these retransmissions, 309 00:11:42.660 --> 00:11:45.210 and this slows down the network even more. 310 00:11:45.210 --> 00:11:46.620 You want to make sure you have good signal 311 00:11:46.620 --> 00:11:48.270 throughout your entire structure 312 00:11:48.270 --> 00:11:50.550 to increase the efficiency of your network. 313 00:11:50.550 --> 00:11:53.130 To do this, you would do what's called a site survey 314 00:11:53.130 --> 00:11:55.470 where you check the signal strength in different areas 315 00:11:55.470 --> 00:11:56.850 and make sure you have the right antennas 316 00:11:56.850 --> 00:11:59.250 and the right repeaters throughout the building.