WEBVTT 0:00:03.140000 --> 0:00:06.460000 Welcome back. In this video, we're going to continue reviewing wireless 0:00:06.460000 --> 0:00:10.500000 LAN and Wi-Fi concepts by now talking about something called split Mac 0:00:10.500000 --> 0:00:17.580000 architectures. So we know that another type of access point you can have 0:00:17.580000 --> 0:00:21.520000 that you'll typically find in a corporate or campus environment is a lightweight 0:00:21.520000 --> 0:00:25.860000 access point. A lightweight access point typically does not provide you 0:00:25.860000 --> 0:00:30.500000 a GUI or a command line, because it is controlled on the back end by another 0:00:30.500000 --> 0:00:35.040000 device called a wireless LAN controller. 0:00:35.040000 --> 0:00:39.120000 So we just talked about how autonomous access point architecture is not 0:00:39.120000 --> 0:00:40.460000 really scalable. 0:00:40.460000 --> 0:00:46.980000 But by having a central point of control, this gives us a lot more flexibility. 0:00:46.980000 --> 0:00:50.320000 So lightweight access points, a lot of times are called laps. 0:00:50.320000 --> 0:00:53.400000 So you'll see that acronym throughout these slides and other white papers. 0:00:53.400000 --> 0:00:54.860000 So that just means lightweight access point. 0:00:54.860000 --> 0:00:58.200000 So now the question is, where do we place the controller? 0:00:58.200000 --> 0:01:00.040000 Because we have basically two options. 0:01:00.040000 --> 0:01:05.600000 The controller could be in the cloud or it could be on premise on site. 0:01:05.600000 --> 0:01:13.920000 Okay, so either way, whether the controller is in the cloud or on premise, 0:01:13.920000 --> 0:01:18.180000 we are probably going to implement what's called a split Mac architecture. 0:01:18.180000 --> 0:01:21.220000 This is the essence of a lightweight architecture split Mac. 0:01:21.220000 --> 0:01:22.480000 So what are we talking about? 0:01:22.480000 --> 0:01:28.540000 Remember, as far as the 802.11 Wi-Fi is concerned, Wi-Fi has a split Mac 0:01:28.540000 --> 0:01:32.680000 architecture. We've got the lower level, which is the PHY, which is stuff 0:01:32.680000 --> 0:01:37.200000 like controlling the antennas, controlling the usage of the radio frequency, 0:01:37.200000 --> 0:01:41.240000 how do we oscillate the radio frequency, how do we deal with contention? 0:01:41.240000 --> 0:01:43.660000 That's all stuff at the lower level, the PHY level. 0:01:43.660000 --> 0:01:47.180000 And then we have the layer two, which is called the Mac layer, which is, 0:01:47.180000 --> 0:01:51.580000 okay, when someone wants to get onto the Wi-Fi, when they want to associate 0:01:51.580000 --> 0:01:55.320000 to this access point, there's a variety of messages that are exchanged. 0:01:55.320000 --> 0:01:57.860000 There's some authentication security that's exchanged. 0:01:57.860000 --> 0:01:59.200000 There's that too. 0:01:59.200000 --> 0:02:02.960000 So a split Mac architecture involves a few things. 0:02:02.960000 --> 0:02:06.540000 Number one, we're going to implement an on premise controller. 0:02:06.540000 --> 0:02:11.400000 And then our lightweight access points are going to split that Mac into 0:02:11.400000 --> 0:02:17.600000 two sections. So the real time functions, the stuff that was handled at 0:02:17.600000 --> 0:02:22.320000 the PHY layer is actually going to still be handled by the access point, 0:02:22.320000 --> 0:02:27.360000 because actually, or the access point, it's got the transceiver in it. 0:02:27.360000 --> 0:02:29.380000 It has the antennas in it. 0:02:29.380000 --> 0:02:32.740000 So it's certainly going to be the one to deal with the radio frequencies 0:02:32.740000 --> 0:02:34.980000 and the electromagnetic radiation. 0:02:34.980000 --> 0:02:38.360000 The controller's not going to do that because he doesn't have any antennas. 0:02:38.360000 --> 0:02:39.700000 He doesn't have any transceivers. 0:02:39.700000 --> 0:02:42.560000 He can't deal with EMR. 0:02:42.560000 --> 0:02:46.900000 The management functions, however, are no longer handled by the access 0:02:46.900000 --> 0:02:51.060000 point itself. Those are offloaded to the controller. 0:02:51.060000 --> 0:02:53.300000 So as an example here, what is split? 0:02:53.300000 --> 0:02:57.280000 Well, our real time functions are handled by the lightweight access point. 0:02:57.280000 --> 0:03:02.480000 So the radio frequency transmit and receive of frames. 0:03:02.480000 --> 0:03:05.680000 Mac management, coordination of when there's a collision, what are we 0:03:05.680000 --> 0:03:08.440000 going to do about that collision? 0:03:08.440000 --> 0:03:12.260000 Possibly the encryption and decryption, although sometimes that goes all 0:03:12.260000 --> 0:03:14.120000 the way up to the controller. 0:03:14.120000 --> 0:03:17.840000 Management functions are offload to the controller. 0:03:17.840000 --> 0:03:19.980000 So, for example, RF management. 0:03:19.980000 --> 0:03:24.840000 So now the access point itself doesn't make the decision about what channel 0:03:24.840000 --> 0:03:26.200000 I should operate on. 0:03:26.200000 --> 0:03:29.760000 How strong should my power be, my transmit power? 0:03:29.760000 --> 0:03:35.780000 All that stuff is dictated to the access point by the controller. 0:03:35.780000 --> 0:03:38.320000 Association and roaming management. 0:03:38.320000 --> 0:03:41.140000 Client authentication, you know, what type of security are we going to 0:03:41.140000 --> 0:03:44.280000 use? The passwords and people submit their passwords. 0:03:44.280000 --> 0:03:47.660000 That password is going to be authenticated by the controller, not by the 0:03:47.660000 --> 0:03:52.120000 access point. Security policies and QOS. 0:03:52.120000 --> 0:04:01.000000 All right, so here we see on the left, we have our autonomous access point, 0:04:01.000000 --> 0:04:02.600000 where he's doing it all, right? 0:04:02.600000 --> 0:04:06.780000 Both the lower layer, that the real time RF information, as well as the 0:04:06.780000 --> 0:04:13.000000 higher stuff like security and QOS, VLAN assignment, decisions about what 0:04:13.000000 --> 0:04:15.740000 channel to select, he's doing it all. 0:04:15.740000 --> 0:04:20.600000 Whereas in a split Mac architecture, the lightweight access point at the 0:04:20.600000 --> 0:04:24.180000 bottom is still doing those real time functions, but it actually creates 0:04:24.180000 --> 0:04:27.900000 a special type of a tunnel called a CAPWAP tunnel. 0:04:27.900000 --> 0:04:31.860000 And then it uses that to control to the wireless LAN controller. 0:04:31.860000 --> 0:04:35.900000 So the wireless LAN controller can push down information to that lightweight 0:04:35.900000 --> 0:04:40.580000 access point, like, hey, here are the SSID's I want you to advertise. 0:04:40.580000 --> 0:04:44.000000 Here's the channel I want you to operate on. 0:04:44.000000 --> 0:04:48.060000 Here's how much transmit power you should be doing. 0:04:48.060000 --> 0:04:52.400000 All of that is tunneled in this thing called a CAPWAP tunnel. 0:04:52.400000 --> 0:04:54.820000 And that's what we're going to talk about in the next video.