1 00:00:00,000 --> 00:00:01,680 In this video, we're going to discuss 2 00:00:01,680 --> 00:00:04,140 wireless considerations that you need to think about 3 00:00:04,140 --> 00:00:06,780 as you start to troubleshoot your wireless networks. 4 00:00:06,780 --> 00:00:09,450 We're going to begin by discussing antennas, their placement, 5 00:00:09,450 --> 00:00:11,430 their type, and their polarization. 6 00:00:11,430 --> 00:00:14,460 Then we're going to cover channel utilization, site surveys, 7 00:00:14,460 --> 00:00:16,050 and the types of information that those things 8 00:00:16,050 --> 00:00:18,660 can help us with as we troubleshoot our networks. 9 00:00:18,660 --> 00:00:20,970 Finally, we're going to talk about wireless access points, 10 00:00:20,970 --> 00:00:25,110 or AP association times, and how association actually works. 11 00:00:25,110 --> 00:00:27,510 First, let's talk all about antennas. 12 00:00:27,510 --> 00:00:29,610 Antennas can come in multiple different types, 13 00:00:29,610 --> 00:00:31,740 and each one has its own purpose. 14 00:00:31,740 --> 00:00:33,870 By default, most wireless access points 15 00:00:33,870 --> 00:00:35,850 are going to use omnidirectional antennas, 16 00:00:35,850 --> 00:00:37,320 and normally they're going to be located 17 00:00:37,320 --> 00:00:39,120 in a vertical form factor. 18 00:00:39,120 --> 00:00:41,760 Now for a vertical antenna, the radiation pattern 19 00:00:41,760 --> 00:00:44,220 for the radio frequency waves is going to extend outward 20 00:00:44,220 --> 00:00:46,320 in all directions away from that antenna 21 00:00:46,320 --> 00:00:48,210 and away from the wireless access point 22 00:00:48,210 --> 00:00:50,010 at an equal power level. 23 00:00:50,010 --> 00:00:51,540 As the radio waves travel further 24 00:00:51,540 --> 00:00:52,860 and further from that antenna, 25 00:00:52,860 --> 00:00:54,840 the signal is going to get lost a little bit 26 00:00:54,840 --> 00:00:57,330 and the power and strength is going to decrease. 27 00:00:57,330 --> 00:00:59,400 Now, if you're monitoring this from your client, 28 00:00:59,400 --> 00:01:00,540 you're going to see that you have 29 00:01:00,540 --> 00:01:03,330 more negative RSSIs as you go further 30 00:01:03,330 --> 00:01:06,000 from the wireless access point and its antenna. 31 00:01:06,000 --> 00:01:07,680 Now, for example, let's say you're sitting 32 00:01:07,680 --> 00:01:09,090 right next to the antenna. 33 00:01:09,090 --> 00:01:12,840 You might have an RSSI of -30 to -40 decibels, 34 00:01:12,840 --> 00:01:14,605 but if you move out a hundred feet away, 35 00:01:14,605 --> 00:01:17,580 that signal strength may now be at an RSSI 36 00:01:17,580 --> 00:01:20,790 of -65 or -70 decibels. 37 00:01:20,790 --> 00:01:22,365 Another type of antenna you might come across 38 00:01:22,365 --> 00:01:26,280 is known as a dipole antenna, or a bi-directional antenna. 39 00:01:26,280 --> 00:01:28,020 With a dipole antenna, the antenna 40 00:01:28,020 --> 00:01:29,880 is going to produce a radio frequency wave 41 00:01:29,880 --> 00:01:31,590 that extends outward in two directions 42 00:01:31,590 --> 00:01:33,180 away from the antenna. 43 00:01:33,180 --> 00:01:35,190 With a dipole antenna, you're normally going to see 44 00:01:35,190 --> 00:01:37,260 a higher RSSI on the client device, 45 00:01:37,260 --> 00:01:39,600 even when it's located further from the access point. 46 00:01:39,600 --> 00:01:42,030 Because this antenna can now focus its power 47 00:01:42,030 --> 00:01:45,443 in only two directions instead of the entire 360 degrees 48 00:01:45,443 --> 00:01:49,170 around itself like an omnidirectional antenna produces. 49 00:01:49,170 --> 00:01:51,120 So if you need the radio frequency waves 50 00:01:51,120 --> 00:01:52,560 to only go in two directions, 51 00:01:52,560 --> 00:01:54,810 a dipole is going to be a good option for you, 52 00:01:54,810 --> 00:01:56,250 but they're not heavily used 53 00:01:56,250 --> 00:01:58,950 in wireless networks for the most part. 54 00:01:58,950 --> 00:02:01,950 Next, we have this thing known as a Yagi antenna. 55 00:02:01,950 --> 00:02:04,243 Now, a Yagi antenna is a type of unidirectional antenna 56 00:02:04,243 --> 00:02:07,920 that sends the radio frequency waves only in one direction. 57 00:02:07,920 --> 00:02:09,780 Due to this focusing of the radio frequency 58 00:02:09,780 --> 00:02:12,030 in a singular direction, a Yagi antenna 59 00:02:12,030 --> 00:02:13,350 can send the radio frequency waves 60 00:02:13,350 --> 00:02:16,020 further in a single direction, using less power 61 00:02:16,020 --> 00:02:18,030 than an omnidirectional antenna will. 62 00:02:18,030 --> 00:02:20,370 Normally, you're going to see a Yagi antenna used 63 00:02:20,370 --> 00:02:21,930 when you're trying to connect two different sites 64 00:02:21,930 --> 00:02:23,490 using a wireless link. 65 00:02:23,490 --> 00:02:25,714 For example, you may want to connect two office buildings 66 00:02:25,714 --> 00:02:28,080 on a college campus using a wireless link 67 00:02:28,080 --> 00:02:30,510 instead of running a buried fiber optic cable. 68 00:02:30,510 --> 00:02:33,990 In this case, you're going to use a Yagi antenna to do that. 69 00:02:33,990 --> 00:02:36,990 Finally, we have a parabolic grid, or disc antenna. 70 00:02:36,990 --> 00:02:39,330 These antennas are unidirectional antennas 71 00:02:39,330 --> 00:02:40,860 just like a Yagi antenna is, 72 00:02:40,860 --> 00:02:42,900 but they're built a little bit differently. 73 00:02:42,900 --> 00:02:45,600 Now, parabolic grid antennas are most commonly used 74 00:02:45,600 --> 00:02:47,910 for site to site applications, where you need to connect 75 00:02:47,910 --> 00:02:49,350 buildings over a longer distance 76 00:02:49,350 --> 00:02:51,180 than you would with a Yagi antenna. 77 00:02:51,180 --> 00:02:53,760 Like a Yagi antenna, a parabolic antenna is going to allow 78 00:02:53,760 --> 00:02:56,490 the radio wave to be transmitted in only one direction, 79 00:02:56,490 --> 00:02:58,770 making it a unidirectional antenna. 80 00:02:58,770 --> 00:03:00,183 Now, when it comes to placing your antennas, 81 00:03:00,183 --> 00:03:03,150 this is going to be dependent on where you're going to place them, 82 00:03:03,150 --> 00:03:04,920 inside or outside of your building, 83 00:03:04,920 --> 00:03:07,110 to create the coverage that you desire. 84 00:03:07,110 --> 00:03:08,670 If you're setting up a site to site 85 00:03:08,670 --> 00:03:10,290 or building to building connection, 86 00:03:10,290 --> 00:03:12,330 you're going to want to use a unidirectional antenna, 87 00:03:12,330 --> 00:03:14,610 like a parabolic or a Yagi antenna. 88 00:03:14,610 --> 00:03:16,110 Now you're going to take that and mount it 89 00:03:16,110 --> 00:03:17,580 on the outside of your building, 90 00:03:17,580 --> 00:03:19,710 and usually you're going to attach it to the roof 91 00:03:19,710 --> 00:03:21,210 and make sure there's a clear line of sight 92 00:03:21,210 --> 00:03:24,060 between both antennas on each of those buildings. 93 00:03:24,060 --> 00:03:25,980 Now, one of the common issues you're going to experience 94 00:03:25,980 --> 00:03:27,870 with wireless antennas for a site to site 95 00:03:27,870 --> 00:03:29,370 or building to building connection 96 00:03:29,370 --> 00:03:31,860 is that the connection may deteriorate and slow down 97 00:03:31,860 --> 00:03:34,350 or completely stop over time. 98 00:03:34,350 --> 00:03:36,810 If this occurs, you need to ensure that both antennas 99 00:03:36,810 --> 00:03:38,760 still have a clear sight between them. 100 00:03:38,760 --> 00:03:40,742 For example, maybe you have two office buildings 101 00:03:40,742 --> 00:03:43,080 and they're only one or two stories high. 102 00:03:43,080 --> 00:03:45,390 You've gone ahead and installed the antennas in the fall, 103 00:03:45,390 --> 00:03:46,800 and there was no issues at all. 104 00:03:46,800 --> 00:03:48,870 You had a perfectly clear line of sight. 105 00:03:48,870 --> 00:03:50,670 But it's been about six months 106 00:03:50,670 --> 00:03:53,280 and now the seasons have changed and spring appears, 107 00:03:53,280 --> 00:03:55,530 and your wireless connection may start to be affected 108 00:03:55,530 --> 00:03:57,630 by trees because they've sprouted new leaves, 109 00:03:57,630 --> 00:03:59,550 and they are now blocking your line of sight clearly 110 00:03:59,550 --> 00:04:01,350 between those two buildings. 111 00:04:01,350 --> 00:04:04,050 Similarly, if in the wintertime there's a lot of snow, 112 00:04:04,050 --> 00:04:05,640 this can also block your signal. 113 00:04:05,640 --> 00:04:07,680 Or if it rains heavily in the summer, 114 00:04:07,680 --> 00:04:09,360 you could also have a deteriorating signal 115 00:04:09,360 --> 00:04:10,950 because the water droplets will block 116 00:04:10,950 --> 00:04:14,040 the wireless communication between these two antennas. 117 00:04:14,040 --> 00:04:15,840 So if you're working with antennas, 118 00:04:15,840 --> 00:04:17,100 you need to think about these things 119 00:04:17,100 --> 00:04:18,660 when you're working outside. 120 00:04:18,660 --> 00:04:19,493 Now, on the other hand, 121 00:04:19,493 --> 00:04:21,209 if you're working inside your building, 122 00:04:21,209 --> 00:04:23,190 you're going to be more likely to use omnidirectional 123 00:04:23,190 --> 00:04:25,020 or unidirectional patch antennas 124 00:04:25,020 --> 00:04:26,580 to control the signal being radiated 125 00:04:26,580 --> 00:04:29,250 by your wireless networks to each of your clients. 126 00:04:29,250 --> 00:04:30,690 With omnidirectional antennas, 127 00:04:30,690 --> 00:04:32,460 it's going to be common to place this on the ceiling 128 00:04:32,460 --> 00:04:34,650 in the middle of the office or classroom. 129 00:04:34,650 --> 00:04:36,450 For a unidirectional patch antenna, 130 00:04:36,450 --> 00:04:38,220 you're usually going to place this on an outer wall 131 00:04:38,220 --> 00:04:39,990 of the building facing inward, 132 00:04:39,990 --> 00:04:42,360 thereby directing all those radio frequency waves 133 00:04:42,360 --> 00:04:45,360 back inward towards the office or the classrooms. 134 00:04:45,360 --> 00:04:47,370 Now, the last thing we need to discuss with antennas 135 00:04:47,370 --> 00:04:49,560 is the concept of polarization. 136 00:04:49,560 --> 00:04:52,170 Polarization is the orientation of the electric field 137 00:04:52,170 --> 00:04:54,930 or transmissions that are occurring from that antenna. 138 00:04:54,930 --> 00:04:57,990 Basically, as the radio frequency waves leave the antenna, 139 00:04:57,990 --> 00:04:59,790 how is it going to be oriented? 140 00:04:59,790 --> 00:05:02,430 Every antenna has a polarization associated with it, 141 00:05:02,430 --> 00:05:03,720 and for Wi-Fi networks, 142 00:05:03,720 --> 00:05:05,850 our antennas usually are going to have a vertical 143 00:05:05,850 --> 00:05:08,820 or horizontal polarization associated with them. 144 00:05:08,820 --> 00:05:11,490 Now, most Wi-Fi clients that have external antennas 145 00:05:11,490 --> 00:05:13,620 are going to use vertical polarization, 146 00:05:13,620 --> 00:05:15,875 but your wireless access point could use vertical 147 00:05:15,875 --> 00:05:18,150 or horizontal polarization, 148 00:05:18,150 --> 00:05:20,340 depending on what type of antenna it has. 149 00:05:20,340 --> 00:05:22,080 Now, if you see a problem with some clients 150 00:05:22,080 --> 00:05:24,690 getting a poor RSSI, even though they're pretty close 151 00:05:24,690 --> 00:05:26,700 to your access point, this may indicate 152 00:05:26,700 --> 00:05:28,440 you have a polarization issue. 153 00:05:28,440 --> 00:05:30,510 If this is the case, I want you to try flipping 154 00:05:30,510 --> 00:05:32,190 the wireless access point antenna 155 00:05:32,190 --> 00:05:34,350 to allow the clients to better connect to that device 156 00:05:34,350 --> 00:05:36,690 if they support bending the antenna upwards. 157 00:05:36,690 --> 00:05:38,253 Or if you're using wireless access points 158 00:05:38,253 --> 00:05:39,960 that are sitting on the floor, 159 00:05:39,960 --> 00:05:42,330 you want to make sure you're using vertical polarization 160 00:05:42,330 --> 00:05:45,030 and radiating antennas to increase your coverage area. 161 00:05:45,030 --> 00:05:46,350 If you're using horizontal, 162 00:05:46,350 --> 00:05:48,780 it's going to keep sending those radio waves out horizontally, 163 00:05:48,780 --> 00:05:51,120 right along the floor, and add up to the desk level 164 00:05:51,120 --> 00:05:52,560 where everybody else is working. 165 00:05:52,560 --> 00:05:55,920 Remember, most Wi-Fi networks use vertical polarization, 166 00:05:55,920 --> 00:05:57,600 so your antennas should be sticking upward 167 00:05:57,600 --> 00:05:59,460 if you're using an omnidirectional antenna 168 00:05:59,460 --> 00:06:01,260 with your Wi-Fi networks. 169 00:06:01,260 --> 00:06:03,840 All right, next we have channel utilization. 170 00:06:03,840 --> 00:06:05,307 Channel utilization is a statistic 171 00:06:05,307 --> 00:06:07,830 or measure of the amount of airtime utilization 172 00:06:07,830 --> 00:06:09,850 that occurs for a particular frequency or channel. 173 00:06:09,850 --> 00:06:12,270 If there's a higher rate of channel utilization, 174 00:06:12,270 --> 00:06:13,500 then that means there's more traffic 175 00:06:13,500 --> 00:06:16,080 being transmitted over that particular frequency. 176 00:06:16,080 --> 00:06:18,030 In order to have a fast wireless network, 177 00:06:18,030 --> 00:06:21,600 you want to keep your channel utilization under around 30%. 178 00:06:21,600 --> 00:06:23,580 Now, channel utilization is not something 179 00:06:23,580 --> 00:06:24,960 you alone can control though, 180 00:06:24,960 --> 00:06:26,580 because there's lots of these different channels 181 00:06:26,580 --> 00:06:29,220 that overlap with other people in that area, 182 00:06:29,220 --> 00:06:30,780 and so these same channels and frequencies 183 00:06:30,780 --> 00:06:33,900 can be used by your network and other networks too. 184 00:06:33,900 --> 00:06:36,150 For example, let's say you're running a wireless B, 185 00:06:36,150 --> 00:06:38,340 or a wireless G, or a wireless N network, 186 00:06:38,340 --> 00:06:41,130 and you're operating in the 2.4 gigahertz spectrum. 187 00:06:41,130 --> 00:06:42,540 We are going to be using the same channels 188 00:06:42,540 --> 00:06:45,750 that everybody else is, channels one, six and 11. 189 00:06:45,750 --> 00:06:47,520 Now, if you have a large office building, 190 00:06:47,520 --> 00:06:48,615 this won't be a big problem for you 191 00:06:48,615 --> 00:06:50,100 because nobody else is going to be 192 00:06:50,100 --> 00:06:52,110 in the same general area as we are. 193 00:06:52,110 --> 00:06:54,000 But if you're in a crowded office building 194 00:06:54,000 --> 00:06:56,370 or a shopping mall or an apartment building, 195 00:06:56,370 --> 00:06:58,080 this can easily start to have a lot 196 00:06:58,080 --> 00:06:59,130 of different wireless networks 197 00:06:59,130 --> 00:07:02,340 operating on the same channels as ours in the same location. 198 00:07:02,340 --> 00:07:03,717 Now, when wireless access points 199 00:07:03,717 --> 00:07:06,180 and wireless clients are operating on the same channel 200 00:07:06,180 --> 00:07:08,670 and all of those things are in the same range of each other, 201 00:07:08,670 --> 00:07:11,250 they're going to begin to form a single broadcast domain, 202 00:07:11,250 --> 00:07:13,110 similar to an ethernet hub. 203 00:07:13,110 --> 00:07:15,360 All of the devices can hear each other's transmissions, 204 00:07:15,360 --> 00:07:17,760 and if any two devices transmit at the same time, 205 00:07:17,760 --> 00:07:20,760 their radio signals will collide and it becomes garbled, 206 00:07:20,760 --> 00:07:24,060 which results in data corruption or a complete frame loss. 207 00:07:24,060 --> 00:07:25,830 If there's an excessive amount of collisions, 208 00:07:25,830 --> 00:07:27,615 data will never be remitted successfully 209 00:07:27,615 --> 00:07:31,170 and the wireless network could become unusable. 210 00:07:31,170 --> 00:07:34,620 So to avoid collisions, 802.11 wireless devices 211 00:07:34,620 --> 00:07:36,540 use a "listen before they speak" approach 212 00:07:36,540 --> 00:07:38,460 when they're accessing the wireless medium, 213 00:07:38,460 --> 00:07:39,900 which is the radio frequency, 214 00:07:39,900 --> 00:07:44,160 following the CSMA/CA, or collision avoidance techniques. 215 00:07:44,160 --> 00:07:45,990 Now with this, devices are going to perform 216 00:07:45,990 --> 00:07:49,560 a Clear Channel Assessment, or CCA, by first listening 217 00:07:49,560 --> 00:07:51,900 to see if another device is actively transmitting 218 00:07:51,900 --> 00:07:54,360 on the channel before they attempt to send their own frames 219 00:07:54,360 --> 00:07:56,040 on that given frequency. 220 00:07:56,040 --> 00:07:58,149 Now, when a device detects another transmission in progress, 221 00:07:58,149 --> 00:08:00,480 it's going to perform a random back off 222 00:08:00,480 --> 00:08:01,950 for a short period of time, 223 00:08:01,950 --> 00:08:04,860 after which it's going to perform another CCA check 224 00:08:04,860 --> 00:08:06,690 before it attempts to transmit. 225 00:08:06,690 --> 00:08:08,520 If the channel is clear after the check, 226 00:08:08,520 --> 00:08:10,380 that device will be able to access the channel 227 00:08:10,380 --> 00:08:11,760 and send some data. 228 00:08:11,760 --> 00:08:13,908 Now, as the number of devices need to transmit frames 229 00:08:13,908 --> 00:08:16,050 starts increasing on a channel, 230 00:08:16,050 --> 00:08:18,030 this is going to cause congestion to occur 231 00:08:18,030 --> 00:08:20,340 to the point where devices can spend a lot more time 232 00:08:20,340 --> 00:08:22,650 waiting to be able to send something. 233 00:08:22,650 --> 00:08:24,060 This results in slower speeds 234 00:08:24,060 --> 00:08:25,560 because devices have to wait longer 235 00:08:25,560 --> 00:08:27,180 before they can send their data. 236 00:08:27,180 --> 00:08:28,500 This is the negative effect 237 00:08:28,500 --> 00:08:30,390 of having high channel utilization, 238 00:08:30,390 --> 00:08:33,450 and at least a slower throughput for our network devices. 239 00:08:33,450 --> 00:08:35,010 Now, how do we solve this problem 240 00:08:35,010 --> 00:08:36,929 of over channel utilization? 241 00:08:36,929 --> 00:08:40,200 Well, first we're going to start by conducting a site survey. 242 00:08:40,200 --> 00:08:42,650 Now, a site survey, also known as a wireless survey, 243 00:08:42,650 --> 00:08:43,860 is the process of planning 244 00:08:43,860 --> 00:08:45,450 and designing a wireless network 245 00:08:45,450 --> 00:08:46,620 to provide a wireless solution 246 00:08:46,620 --> 00:08:48,570 that will deliver the required wireless coverage, 247 00:08:48,570 --> 00:08:51,450 the data rates, network capacity, roaming capability, 248 00:08:51,450 --> 00:08:54,630 and quality of service that your organization desires. 249 00:08:54,630 --> 00:08:57,300 As part of the wireless survey, you need to determine 250 00:08:57,300 --> 00:08:59,100 where each access point is located, 251 00:08:59,100 --> 00:09:01,440 what power level it's using to transmit 252 00:09:01,440 --> 00:09:05,520 by using its effective isotropic radiated power, or EIRP, 253 00:09:05,520 --> 00:09:08,337 overlapping coverage areas for your wireless access points, 254 00:09:08,337 --> 00:09:10,620 and the other wireless access points in clients 255 00:09:10,620 --> 00:09:12,120 that may be operating in the same, 256 00:09:12,120 --> 00:09:14,430 or general area or channels is you. 257 00:09:14,430 --> 00:09:16,680 Now, by using this site survey information, 258 00:09:16,680 --> 00:09:17,790 you can determine if you need 259 00:09:17,790 --> 00:09:20,310 to change the channels you're using to a less busy, 260 00:09:20,310 --> 00:09:21,690 less utilized channel, 261 00:09:21,690 --> 00:09:23,790 or if you may need to upgrade your networks 262 00:09:23,790 --> 00:09:25,980 to a new frequency band altogether. 263 00:09:25,980 --> 00:09:27,750 After all, if you decide to upgrade 264 00:09:27,750 --> 00:09:31,200 to a wireless N, wireless AC, or wireless AX network, 265 00:09:31,200 --> 00:09:33,480 and you start using the five gigahertz spectrum, 266 00:09:33,480 --> 00:09:35,940 this gives you 24 non-overlapping channels 267 00:09:35,940 --> 00:09:38,820 instead of the three in the 2.4 gigahertz spectrum. 268 00:09:38,820 --> 00:09:41,430 So there's going to be a lot less overall utilization 269 00:09:41,430 --> 00:09:44,940 on each of those 24 channels in the five gigahertz spectrum. 270 00:09:44,940 --> 00:09:47,430 By conducting a site survey, you can better understand 271 00:09:47,430 --> 00:09:49,980 the wireless environment in and around your networks, 272 00:09:49,980 --> 00:09:52,080 and this is going to allow you to configure your devices 273 00:09:52,080 --> 00:09:53,790 to use the less utilized channels, 274 00:09:53,790 --> 00:09:55,980 ensure there's proper coverage for all of your work areas, 275 00:09:55,980 --> 00:09:57,990 and ensure your wireless network 276 00:09:57,990 --> 00:09:59,880 is not being blocked or interfered with 277 00:09:59,880 --> 00:10:02,550 by physical obstacles within the building. 278 00:10:02,550 --> 00:10:03,660 Finally, we need to talk 279 00:10:03,660 --> 00:10:06,330 about wireless access point association times. 280 00:10:06,330 --> 00:10:08,250 Now, when a wireless client attempts to connect 281 00:10:08,250 --> 00:10:11,970 to a wireless network, it goes through a seven step process. 282 00:10:11,970 --> 00:10:14,148 First, the wireless client is going to send a probe request 283 00:10:14,148 --> 00:10:16,933 to discover any 802.11 wireless networks 284 00:10:16,933 --> 00:10:19,530 in the general location that it's in. 285 00:10:19,530 --> 00:10:21,900 Essentially, it's going to send a broadcast message 286 00:10:21,900 --> 00:10:26,900 to the BSSID of ff:ff:ff:ff:ff:ff, 287 00:10:27,720 --> 00:10:29,670 and all the access points in that area 288 00:10:29,670 --> 00:10:32,520 that are using the same frequency, either 2.4 gigahertz 289 00:10:32,520 --> 00:10:35,400 or five gigahertz, will respond to that client. 290 00:10:35,400 --> 00:10:38,040 Second, any access points that receive this probe, 291 00:10:38,040 --> 00:10:40,230 will check to see if they can support the data rate 292 00:10:40,230 --> 00:10:42,690 that the client is now requesting in that probe. 293 00:10:42,690 --> 00:10:45,450 For example, if I'm a wireless AC access point 294 00:10:45,450 --> 00:10:47,940 and you just requested to communicate using wireless B, 295 00:10:47,940 --> 00:10:49,320 I'm going to ignore your request 296 00:10:49,320 --> 00:10:51,120 because I'm operating at five gigahertz 297 00:10:51,120 --> 00:10:53,520 and you're operating at 2.4 gigahertz. 298 00:10:53,520 --> 00:10:55,962 But if we both support wireless N, then I can respond 299 00:10:55,962 --> 00:10:59,310 with a probe response that provides my SSID, 300 00:10:59,310 --> 00:11:01,770 my supported data rates, my encryption types 301 00:11:01,770 --> 00:11:03,300 if I'm using wireless security, 302 00:11:03,300 --> 00:11:06,390 and other capabilities of my particular access point. 303 00:11:06,390 --> 00:11:08,520 Third, our wireless client will then send 304 00:11:08,520 --> 00:11:11,891 a low level 802.11 authentication frame to the access point, 305 00:11:11,891 --> 00:11:14,430 and this will begin the authentication handshake 306 00:11:14,430 --> 00:11:17,040 between my client and the access point. 307 00:11:17,040 --> 00:11:19,850 Fourth, the access point receives this authentication frame 308 00:11:19,850 --> 00:11:21,540 and responds with an acknowledgement 309 00:11:21,540 --> 00:11:23,190 to continue the handshake. 310 00:11:23,190 --> 00:11:24,870 If the wireless access point receives 311 00:11:24,870 --> 00:11:26,670 anything other than an authentication 312 00:11:26,670 --> 00:11:28,770 or a probe request from this client though, 313 00:11:28,770 --> 00:11:30,990 it's going to send a deauthentication frame 314 00:11:30,990 --> 00:11:33,060 and break the communication with this client, 315 00:11:33,060 --> 00:11:34,890 because this client is not yet part 316 00:11:34,890 --> 00:11:36,840 of my authenticated network. 317 00:11:36,840 --> 00:11:38,850 Fifth, the wireless client is going to choose 318 00:11:38,850 --> 00:11:40,920 the access point it wants to associate with 319 00:11:40,920 --> 00:11:42,630 and sends an association request 320 00:11:42,630 --> 00:11:45,390 using the encryption and 802.11 capabilities 321 00:11:45,390 --> 00:11:47,730 that are supported by that access point. 322 00:11:47,730 --> 00:11:49,920 Sixth, the access point is going to process 323 00:11:49,920 --> 00:11:52,110 the association request if the information 324 00:11:52,110 --> 00:11:54,090 sent matches its own capabilities, 325 00:11:54,090 --> 00:11:56,730 and then an association ID is being created 326 00:11:56,730 --> 00:11:59,370 for this wireless client and this access point. 327 00:11:59,370 --> 00:12:00,930 And the access point is going to respond 328 00:12:00,930 --> 00:12:03,570 with an association response of success. 329 00:12:03,570 --> 00:12:06,030 This way, the client knows it is now fully connected 330 00:12:06,030 --> 00:12:07,890 to this wireless access point 331 00:12:07,890 --> 00:12:09,450 Seven, now that the client 332 00:12:09,450 --> 00:12:11,370 is fully connected and associated, 333 00:12:11,370 --> 00:12:13,620 it can begin to conduct any data transfer it needs to 334 00:12:13,620 --> 00:12:16,920 and utilize the wireless network and its associated devices. 335 00:12:16,920 --> 00:12:19,320 Now, that's how everything is supposed to operate, 336 00:12:19,320 --> 00:12:21,720 but sometimes you're going to see a wireless network 337 00:12:21,720 --> 00:12:23,640 that has a really long association time 338 00:12:23,640 --> 00:12:25,260 for an end user's client. 339 00:12:25,260 --> 00:12:27,720 This is because the client has to scan the airwaves, 340 00:12:27,720 --> 00:12:29,880 find the access points it might want to connect to, 341 00:12:29,880 --> 00:12:32,910 request the association, authenticate to the access point, 342 00:12:32,910 --> 00:12:36,060 and then contact the DHCP server to get an IP address 343 00:12:36,060 --> 00:12:37,500 prior to being able to actually use 344 00:12:37,500 --> 00:12:40,290 that wireless network connection that we just established. 345 00:12:40,290 --> 00:12:42,150 This process can take just a few seconds 346 00:12:42,150 --> 00:12:43,860 in a not heavily loaded network, 347 00:12:43,860 --> 00:12:45,870 but it can take up to 30 to 60 seconds 348 00:12:45,870 --> 00:12:47,370 if you have a busier network. 349 00:12:47,370 --> 00:12:49,230 To speed up the association process, 350 00:12:49,230 --> 00:12:51,900 clients should be located in a high signal strength area. 351 00:12:51,900 --> 00:12:54,599 Those with the highest RSSIs during the association process 352 00:12:54,599 --> 00:12:56,820 are going to give us a stronger strength, 353 00:12:56,820 --> 00:12:58,140 and that's going to drastically reduce 354 00:12:58,140 --> 00:13:00,093 the wait time during this association.