WEBVTT 1 00:00.000 --> 00:05.610 Wireless roaming is a big part of wireless network deployments, configurations, 2 00:05.610 --> 00:06.960 and designs. 3 00:06.960 --> 00:11.680 The idea here is that we need to cover a lot of space, therefore we're going to 4 00:11.680 --> 00:11.880 need a 5 00:11.880 --> 00:13.920 lot of access points. 6 00:13.920 --> 00:19.880 And if I'm a user on a mobile device here, maybe I've got a video call going on 7 00:19.880 --> 00:20.880 my phone 8 00:20.880 --> 00:24.990 and I'm connected to this access point on the left, well, I'm very likely to be 9 00:24.990 --> 00:25.480 mobile 10 00:25.480 --> 00:26.480 with my mobile device. 11 00:26.480 --> 00:29.000 That's why we call them mobile devices. 12 00:29.000 --> 00:34.140 And now all of a sudden I'm over here, apparently bending over almost backwards WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 12 00:29.000 --> 00:34.140 And now all of a sudden I'm over here, apparently bending over almost backwards 13 00:34.140 --> 00:35.280 with my phone, 14 00:35.280 --> 00:37.820 maybe trying to get a good angle for my video call. 15 00:37.820 --> 00:43.240 But either way, we are now connecting probably to a different access point. 16 00:43.240 --> 00:47.360 And this process is known as a ROM. 17 00:47.360 --> 00:51.160 Before we really jump into the weeds of wireless networking, we might just 18 00:51.160 --> 00:52.040 think that this 19 00:52.040 --> 00:53.560 is a very easy process. 20 00:53.560 --> 00:55.600 I am connected to this access point. 21 00:55.600 --> 00:59.000 Now I'm connected to this access point and life should be good. 22 00:59.000 --> 01:02.400 However, there's a lot of implications to this. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 22 00:59.000 --> 01:02.400 However, there's a lot of implications to this. 23 01:02.400 --> 01:08.160 First and foremost, just performing a ROM itself, just from an 802.11 24 01:08.160 --> 01:09.360 perspective, is 25 01:09.360 --> 01:10.720 going to be very disruptive. 26 01:10.720 --> 01:16.820 I have to actually issue a association request here to get onto the access 27 01:16.820 --> 01:18.080 point to start 28 01:18.080 --> 01:19.080 with. 29 01:19.080 --> 01:23.210 And then I have to initiate a re-association request over on this side to 30 01:23.210 --> 01:23.800 suggest that I 31 01:23.800 --> 01:25.040 want to roam. 32 01:25.040 --> 01:27.680 But keep in mind that there's an authentication part to this. 33 01:27.680 --> 01:31.720 I need to make sure that I'm allowed to be on the access point on this Wi-Fi WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 33 01:27.680 --> 01:31.720 I need to make sure that I'm allowed to be on the access point on this Wi-Fi 34 01:31.720 --> 01:32.720 connection. 35 01:32.720 --> 01:35.440 So there's a back and forth negotiation here. 36 01:35.440 --> 01:38.320 And then when I perform re-association, I'm going to have to perform back and 37 01:38.320 --> 01:38.640 forth 38 01:38.640 --> 01:40.280 negotiations. 39 01:40.280 --> 01:45.200 And I'm going to have to make sure that I'm allowed to be on the Wi-Fi again. 40 01:45.200 --> 01:50.320 And this whole process, before we even get into anything connected on the back 41 01:50.320 --> 01:50.800 end of 42 01:50.800 --> 01:53.920 the access points, is going to require a lot of time. 43 01:53.920 --> 01:57.620 And this alone might make it so that I drop my video call, even if it's for a 44 01:57.620 --> 01:58.160 couple of 45 01:58.160 --> 02:00.640 seconds before it comes back. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 45 01:58.160 --> 02:00.640 seconds before it comes back. 46 02:00.640 --> 02:04.120 But for some video calls, that means that that call will get dropped. 47 02:04.120 --> 02:06.840 And that is again very disruptive. 48 02:06.840 --> 02:10.550 Now one thing we might consider trying to do is to make the environment a 49 02:10.550 --> 02:11.200 little bit 50 02:11.200 --> 02:14.200 more favorable as far as creating ROMs. 51 02:14.200 --> 02:18.160 So one of the things we can do is deploy our access points. 52 02:18.160 --> 02:23.600 So there's a lot of overlap, meaning that when I'm walking this direction, even 53 02:23.600 --> 02:24.200 by the time 54 02:24.200 --> 02:28.250 I say, okay, I'm going to roam over to this new AP, ideally I still have really 55 02:28.250 --> 02:29.040 good signal 56 02:29.040 --> 02:31.320 to the previous access point. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 56 02:29.040 --> 02:31.320 to the previous access point. 57 02:31.320 --> 02:36.990 But it's always worth noting that the ROM is not a decision that's made by the 58 02:36.990 --> 02:37.600 access 59 02:37.600 --> 02:46.080 points, but rather it's decided by the device itself, by the wireless station. 60 02:46.080 --> 02:51.010 And so this is something that as network admins can make us very upset and 61 02:51.010 --> 02:52.400 frustrated with, 62 02:52.400 --> 02:56.200 is we have no control over these devices and when they decide to roam. 63 02:56.200 --> 02:57.200 Why do they roam? 64 02:57.200 --> 03:00.620 Well, they're going to be paying attention to the RSSI, that's that received WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 64 02:57.200 --> 03:00.620 Well, they're going to be paying attention to the RSSI, that's that received 65 03:00.620 --> 03:01.360 signal strength 66 03:01.360 --> 03:04.760 indicator of the access point they're connecting to. 67 03:04.760 --> 03:08.620 They're going to pay attention especially to that signal to noise ratio, the SN 68 03:08.620 --> 03:08.960 R. 69 03:08.960 --> 03:11.960 We covered these concepts earlier on in the course. 70 03:11.960 --> 03:16.680 And so they're going to largely just be looking at their signal strength. 71 03:16.680 --> 03:20.520 And at some point, they have to decide that it's time to roam. 72 03:20.520 --> 03:23.990 Now this takes a little bit of nuance because we might think, okay, well, again 73 03:23.990 --> 03:24.560 , maybe this 74 03:24.560 --> 03:28.890 is straightforward, I get close to another access point over here and my device 75 03:28.890 --> 03:29.440 decides 76 03:29.440 --> 03:31.160 to roam. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 76 03:29.440 --> 03:31.160 to roam. 77 03:31.160 --> 03:35.840 That is maybe a little bit true, but we have to find a balance. 78 03:35.840 --> 03:43.360 So imagine if I as a user, I sit apparently very crooked here, still having 79 03:43.360 --> 03:44.880 some problems. 80 03:44.880 --> 03:49.760 But I sit at my desk every day doing my work and my mobile devices here and I 81 03:49.760 --> 03:50.440 happen to 82 03:50.440 --> 03:54.440 have an office that's between two access points. 83 03:54.440 --> 03:58.460 Now if this mobile device was just constantly looking at to say, hey, which of 84 03:58.460 --> 03:59.000 these is 85 03:59.000 --> 04:02.920 better, chances are that changes throughout the day. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 85 03:59.000 --> 04:02.920 better, chances are that changes throughout the day. 86 04:02.920 --> 04:06.590 So maybe this access point on the left is better when I sit down at the start 87 04:06.590 --> 04:07.680 of the day. 88 04:07.680 --> 04:10.320 And so I associate to this AP. 89 04:10.320 --> 04:14.460 But then a few minutes later, this access point actually appears like it's 90 04:14.460 --> 04:16.000 going to be better. 91 04:16.000 --> 04:17.240 And this goes back and forth. 92 04:17.240 --> 04:20.440 Well, I certainly don't want this mobile device to be performing something 93 04:20.440 --> 04:21.160 disruptive like 94 04:21.160 --> 04:23.680 a roam constantly throughout the day. 95 04:23.680 --> 04:25.000 So there's a threshold here. 96 04:25.000 --> 04:29.260 We're saying, hey, yeah, maybe this access point on the right here, let's say 97 04:29.260 --> 04:29.680 it's a 98 04:29.680 --> 04:34.520 negative something like 63 dBm. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 98 04:29.680 --> 04:34.520 negative something like 63 dBm. 99 04:34.520 --> 04:37.200 And this over on the left, I've been associated to it for a while. 100 04:37.200 --> 04:39.880 But for whatever reason, it's now looking bad. 101 04:39.880 --> 04:44.960 This is a negative 68 dBm, just still a really good signal. 102 04:44.960 --> 04:48.120 But maybe not quite as good for voice calls. 103 04:48.120 --> 04:51.270 Well, is this enough of a signal difference to say, let's go ahead and do a 104 04:51.270 --> 04:51.880 disruptive 105 04:51.880 --> 04:52.920 roam. 106 04:52.920 --> 04:53.920 It depends on the client. 107 04:53.920 --> 04:57.840 Again, we don't get to control that as the network admins for the most part. 108 04:57.840 --> 05:01.640 We are just going to have to hope that these devices stay stable. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 108 04:57.840 --> 05:01.640 We are just going to have to hope that these devices stay stable. 109 05:01.640 --> 05:05.120 And so it's a matter of saying, well, now this is a negative 75. 110 05:05.120 --> 05:07.060 This is a really bad signal. 111 05:07.060 --> 05:11.500 We do need to trigger in those situations, but we don't want to be stuck just 112 05:11.500 --> 05:12.080 constantly 113 05:12.080 --> 05:14.320 roaming back and forth. 114 05:14.320 --> 05:18.240 So be aware that our wireless stations get to make those decisions. 115 05:18.240 --> 05:23.240 And sometimes there's not a lot we can do about that on the networking side. 116 05:23.240 --> 05:29.190 Now, in addition to having just the whole roam and associate and re-associate 117 05:29.190 --> 05:30.080 process, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 117 05:29.190 --> 05:30.080 process, 118 05:30.080 --> 05:34.920 we have to worry a little bit about what's on the back end here behind the 119 05:34.920 --> 05:36.280 access points. 120 05:36.280 --> 05:41.980 So when we look at autonomous access points, so this is before lightweight, we 121 05:41.980 --> 05:42.440 have our 122 05:42.440 --> 05:46.340 access points here, and they're connecting maybe into some kind of switched 123 05:46.340 --> 05:47.440 infrastructure. 124 05:47.440 --> 05:49.760 And I'm going to perform this roam. 125 05:49.760 --> 05:54.400 Well, like we mentioned, we have to do, in order to make this roam happen, we 126 05:54.400 --> 05:54.920 have to 127 05:54.920 --> 05:58.480 do our authentication and our security. 128 05:58.480 --> 06:02.170 And so this is going to allow me to make sure that I'm allowed to be again on WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 128 05:58.480 --> 06:02.170 And so this is going to allow me to make sure that I'm allowed to be again on 129 06:02.170 --> 06:03.920 this network. 130 06:03.920 --> 06:07.710 One thing that we can do, or we were able to do with autonomous access points 131 06:07.710 --> 06:08.160 back in 132 06:08.160 --> 06:13.660 the day, was have a shared key mechanism, which would allow this access point 133 06:13.660 --> 06:15.400 over here to 134 06:15.400 --> 06:21.270 tell the new AP, because I'm over here, tell that access point, hey, this 135 06:21.270 --> 06:22.240 person is allowed 136 06:22.240 --> 06:24.120 to be on the network. 137 06:24.120 --> 06:29.120 And so this was especially common with deploying into Cisco networks. 138 06:29.120 --> 06:35.480 We'd have CCKM, for example, which is Cisco centralized key management. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 138 06:29.120 --> 06:35.480 We'd have CCKM, for example, which is Cisco centralized key management. 139 06:35.480 --> 06:40.310 And it would allow us to effectively skip the authentication process on a new 140 06:40.310 --> 06:40.840 access 141 06:40.840 --> 06:44.850 point, even though this was an autonomous architecture, meaning each AP was 142 06:44.850 --> 06:45.360 configured 143 06:45.360 --> 06:50.560 individually, technology such as CCKM would allow us to greatly speed up the 144 06:50.560 --> 06:52.560 roaming process. 145 06:52.560 --> 06:57.760 But this was largely required because each access point was its own entity. 146 06:57.760 --> 07:02.480 Well, now let's look at things from a lightweight perspective. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 146 06:57.760 --> 07:02.480 Well, now let's look at things from a lightweight perspective. 147 07:02.480 --> 07:07.120 When we have a lightweight architecture, we have a wireless LAN controller. 148 07:07.120 --> 07:12.920 And the wireless LAN controller might have two different access points. 149 07:12.920 --> 07:16.920 And I want to perform the ROM now from one AP to the other on the same 150 07:16.920 --> 07:17.960 controller. 151 07:17.960 --> 07:21.360 Well, at that point, the keys are being managed by the controller. 152 07:21.360 --> 07:25.400 And so I can receive the key and then forward it down to the new AP. 153 07:25.400 --> 07:28.360 And now it happens as part of a centralized architecture. 154 07:28.360 --> 07:31.840 So we can skip the authentication mechanism as well. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 154 07:28.360 --> 07:31.840 So we can skip the authentication mechanism as well. 155 07:31.840 --> 07:35.880 However, now we have to think about what happens if we have two wireless LAN 156 07:35.880 --> 07:37.560 controllers. 157 07:37.560 --> 07:41.960 And we have two different access points that are connecting to the two 158 07:41.960 --> 07:42.320 different 159 07:42.320 --> 07:45.440 WLCs, and I want to roam from one to the other. 160 07:45.440 --> 07:48.310 Well, now we're going to find that we need some communication back and forth 161 07:48.310 --> 07:48.560 between 162 07:48.560 --> 07:49.720 the wireless LAN controllers. 163 07:49.720 --> 07:54.460 And so we're still going to need some form of key management to allow us to 164 07:54.460 --> 07:55.120 pass keys 165 07:55.120 --> 07:56.120 back and forth. 166 07:56.120 --> 08:00.080 But that is going to be a big part of speeding up the roaming process. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 166 07:56.120 --> 08:00.080 But that is going to be a big part of speeding up the roaming process. 167 08:00.080 --> 08:03.960 Now there's another big aspect to roaming. 168 08:03.960 --> 08:08.200 And this has to do with layer two versus layer three. 169 08:08.200 --> 08:12.880 If we think about it, an access point is essentially like a switch. 170 08:12.880 --> 08:14.200 It's a wireless bridge. 171 08:14.200 --> 08:18.480 It has a physical connection here and it has a wireless connection here, but it 172 08:18.480 --> 08:18.760 's really 173 08:18.760 --> 08:21.880 just switching traffic back and forth at layer two. 174 08:21.880 --> 08:23.680 It's a layer two device. 175 08:23.680 --> 08:28.100 So if I have a mobile device here and it's on an SSID, this SSID might be on a 176 08:28.100 --> 08:28.840 specific 177 08:28.840 --> 08:31.280 VLAN like VLAN five. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 177 08:28.840 --> 08:31.280 VLAN like VLAN five. 178 08:31.280 --> 08:36.220 And then that either gets chunked or not, either way, maybe it's an access port 179 08:36.220 --> 08:36.280 , but 180 08:36.280 --> 08:40.120 it gets handed off to a switching infrastructure here. 181 08:40.120 --> 08:44.290 And so if I want to roam to another access point, maybe this access point, by 182 08:44.290 --> 08:44.960 the way, 183 08:44.960 --> 08:46.960 is just part of the same layer to domain. 184 08:46.960 --> 08:48.840 It's not part of the same switch. 185 08:48.840 --> 08:52.770 It's not connected to the same switch, but VLAN five exists throughout this 186 08:52.770 --> 08:54.040 whole infrastructure 187 08:54.040 --> 08:55.840 because of trunk links. 188 08:55.840 --> 09:02.220 And so if I want to roam over to this new AP, I can just get on to that same SS WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 188 08:55.840 --> 09:02.220 And so if I want to roam over to this new AP, I can just get on to that same SS 189 09:02.220 --> 09:02.840 ID and 190 09:02.840 --> 09:06.080 be part of VLAN five and nothing changes. 191 09:06.080 --> 09:12.940 Maybe my p address is something like 10 dot 10 dot five dot one 31, where five 192 09:12.940 --> 09:13.160 is the 193 09:13.160 --> 09:16.280 subnet that is associated with VLAN five. 194 09:16.280 --> 09:21.920 So once I roam, I'm still on VLAN five, I can still be dot one 31. 195 09:21.920 --> 09:23.760 Life is still good. 196 09:23.760 --> 09:25.120 Well, here's the question. 197 09:25.120 --> 09:32.440 What happens then if I'm going to end up roaming through a layer three boundary WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 197 09:25.120 --> 09:32.440 What happens then if I'm going to end up roaming through a layer three boundary 198 09:32.440 --> 09:32.520 ? 199 09:32.520 --> 09:40.440 So now we have an access point over here and it's advertising the same SSID, 200 09:40.440 --> 09:41.400 but it's 201 09:41.400 --> 09:43.880 associated with a different VLAN. 202 09:43.880 --> 09:46.440 It's let's say VLAN 11. 203 09:46.440 --> 09:48.720 So now can I roam this way? 204 09:48.720 --> 09:50.960 Well, I can technically roam. 205 09:50.960 --> 09:52.240 It's the same SSID. 206 09:52.240 --> 09:57.570 It's the same network name, but now can I maintain my same IP address in the 207 09:57.570 --> 09:58.160 autonomous 208 09:58.160 --> 09:59.160 world? 209 09:59.160 --> 10:01.000 The answer is no, I cannot. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 209 09:59.160 --> 10:01.000 The answer is no, I cannot. 210 10:01.000 --> 10:05.120 And the reason for that is because VLAN five doesn't exist over here. 211 10:05.120 --> 10:06.560 That subnet doesn't exist. 212 10:06.560 --> 10:11.800 If if a packet comes in destined for 10 dot 10 dot five, that would be the sub 213 10:11.800 --> 10:12.320 net I'm 214 10:12.320 --> 10:13.320 on. 215 10:13.320 --> 10:15.360 And let's just say it's a slash 24. 216 10:15.360 --> 10:16.920 What's the layer three device going to do? 217 10:16.920 --> 10:21.480 It's going to forward it this way because this is where that subnet lives. 218 10:21.480 --> 10:27.950 So if my wireless device is now over here, trying to use 10 dot 10 dot five dot 219 10:27.950 --> 10:28.680 one thirty 220 10:28.680 --> 10:34.590 one, at that point, we're not going to ever get traffic because we performed a WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 220 10:28.680 --> 10:34.590 one, at that point, we're not going to ever get traffic because we performed a 221 10:34.590 --> 10:35.360 layer three 222 10:35.360 --> 10:37.120 roam as such. 223 10:37.120 --> 10:41.620 This is even more disruptive than having to do re association and reauthent 224 10:41.620 --> 10:42.440 ication because 225 10:42.440 --> 10:45.680 now I have to get a new address. 226 10:45.680 --> 10:51.480 I have to do DHCP, I have to get a 10 dot 10 dot 11 dot whatever address. 227 10:51.480 --> 10:55.870 And so I've got to get a new IP address by the time that process completes, not 228 10:55.870 --> 10:56.120 only 229 10:56.120 --> 11:00.490 does that take a while, but on top of that, now I no longer have this IP WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 229 10:56.120 --> 11:00.490 does that take a while, but on top of that, now I no longer have this IP 230 11:00.490 --> 11:01.360 address. 231 11:01.360 --> 11:05.230 So whatever sessions I was in, maybe it was a video call, for example, I'm 232 11:05.230 --> 11:05.840 probably going 233 11:05.840 --> 11:10.060 to drop that call immediately because it's looking for this IP address and I 234 11:10.060 --> 11:10.640 now have 235 11:10.640 --> 11:12.520 a new IP address. 236 11:12.520 --> 11:16.800 So a layer two Rome, we'll change colors here a little bit. 237 11:16.800 --> 11:21.680 So a layer two Rome is exactly what we saw here, roaming between access points 238 11:21.680 --> 11:22.200 that's 239 11:22.200 --> 11:24.760 part of the same layer two domain. 240 11:24.760 --> 11:29.450 Layer three roaming is what we saw down here, where we roamed to a new access 241 11:29.450 --> 11:30.200 point with WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 241 11:29.450 --> 11:30.200 point with 242 11:30.200 --> 11:36.860 the same SSID, but it's part of a different routed network, at least over on 243 11:36.860 --> 11:37.600 that side 244 11:37.600 --> 11:42.400 of a layer three boundaries, where we have new subnets and new VLANs. 245 11:42.400 --> 11:49.520 So a layer three Rome must be avoided at all costs. 246 11:49.520 --> 11:53.640 Now a lightweight architecture might have a little bit something to say about 247 11:53.640 --> 11:54.160 helping 248 11:54.160 --> 11:55.480 us out with that. 249 11:55.480 --> 11:58.480 For example, now we have wireless LAN controllers. 250 11:58.480 --> 12:01.600 So is that going to be able to help us out? WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 250 11:58.480 --> 12:01.600 So is that going to be able to help us out? 251 12:01.600 --> 12:05.860 Because maybe these access points are still part of a different layer three 252 12:05.860 --> 12:06.600 network. 253 12:06.600 --> 12:10.800 This access point roaming to this access point, if they're part of, they're 254 12:10.800 --> 12:11.600 basically in the 255 12:11.600 --> 12:16.120 same architecture where they're on opposite sides of a layer three boundary, 256 12:16.120 --> 12:16.560 what does 257 12:16.560 --> 12:18.520 this Rome end up doing? 258 12:18.520 --> 12:22.880 Well this Rome ends up still being a layer two Rome, thanks to the wireless LAN 259 12:22.880 --> 12:23.840 controller. 260 12:23.840 --> 12:27.730 This is a way that lightweight architectures greatly help us out because we 261 12:27.730 --> 12:28.680 have the ability 262 12:28.680 --> 12:32.960 to centralize a lot of our operations via the controller. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000 262 12:28.680 --> 12:32.960 to centralize a lot of our operations via the controller. 263 12:32.960 --> 12:37.440 So this is a presentation largely of the challenges that we have with roaming 264 12:37.440 --> 12:39.360 in a wireless environment. 265 12:39.360 --> 12:43.230 Roming is almost never good, however we do have things that we can do to 266 12:43.230 --> 12:44.040 improve it, 267 12:44.040 --> 12:46.800 such as improving our authentication. 268 12:46.800 --> 12:49.610 But when it comes to layer two and layer three roaming, there might even be 269 12:49.610 --> 12:50.160 things that we 270 12:50.160 --> 12:53.480 can do in lightweight to mitigate the effects of that. 271 12:53.480 --> 12:55.360 And we're going to take a look at that in the next video.