1 00:00:12,260 --> 00:00:14,330 In this video I'm going to discuss wi fi. 2 00:00:14,360 --> 00:00:18,260 WI fi is so important, I think for many of us today. 3 00:00:18,260 --> 00:00:21,190 There's no question why we need to learn this. 4 00:00:21,200 --> 00:00:26,990 It's really good that Cisco have put it back into the CCNA in the really old CCNA. 5 00:00:27,020 --> 00:00:30,680 They had wi fi, then it was removed, but now it's back. 6 00:00:30,680 --> 00:00:34,370 WI fi is really, really important in today's networks. 7 00:00:34,370 --> 00:00:39,230 Can you imagine life today without wi fi or wireless connections? 8 00:00:39,230 --> 00:00:45,020 We today take it for granted that we're going to have wi fi when we go to the office or a coffee shop 9 00:00:45,020 --> 00:00:50,450 or even for a lot of us at home, when we book a hotel, we expect wi fi connections. 10 00:00:50,450 --> 00:00:56,930 How many of you I mean, I do this all the time, but do you do this when you check a new hotel that 11 00:00:56,930 --> 00:00:57,800 you want to stay in? 12 00:00:57,800 --> 00:01:01,520 Do you make sure that they've got wi fi or an Airbnb? 13 00:01:02,000 --> 00:01:08,180 I really like Airbnb's, but one of the first things that I'll check is if they have wi fi, I'll consider 14 00:01:08,180 --> 00:01:08,660 staying there. 15 00:01:08,660 --> 00:01:11,390 If they don't have wi fi, I won't consider staying there. 16 00:01:11,390 --> 00:01:12,620 They have to have wi fi. 17 00:01:12,620 --> 00:01:15,260 It's that important for so many of us today. 18 00:01:15,830 --> 00:01:16,100 Okay. 19 00:01:16,130 --> 00:01:21,860 Now, there's obviously a big difference between wi fi connections and cabled connections and the bad 20 00:01:21,860 --> 00:01:22,670 old days. 21 00:01:23,270 --> 00:01:27,350 And I've got an old laptop here in the bad old days. 22 00:01:27,380 --> 00:01:35,270 Laptops such as these had Ethernet connections built in, so I would be able to connect a Ethernet cable 23 00:01:35,270 --> 00:01:36,710 directly to the laptop. 24 00:01:36,710 --> 00:01:38,390 But modern laptops don't have that. 25 00:01:38,390 --> 00:01:42,560 I mean, your laptop, maybe you've got a mac or a PC. 26 00:01:43,070 --> 00:01:48,560 They typically don't have any connections for Ethernet cables. 27 00:01:48,560 --> 00:01:53,510 They can only connect to the network or to the Internet using wi fi. 28 00:01:55,060 --> 00:02:02,650 If I wanted to add an Ethernet connection to this laptop as an example, I have to plug in a USB Ethernet 29 00:02:02,650 --> 00:02:07,970 adapter and then I can add this to a wired network. 30 00:02:07,990 --> 00:02:14,050 So for a lot of us today, a lot of devices only support WiFi. 31 00:02:14,290 --> 00:02:17,710 A lot of devices today don't support Wired connections. 32 00:02:19,050 --> 00:02:23,340 That's especially true, I think, with devices such as these Iot devices. 33 00:02:23,460 --> 00:02:26,190 I mean, this is a hue bulb. 34 00:02:27,170 --> 00:02:33,350 It seemed ridiculous, but in the past I would have had to have used an Ethernet cable to get a device 35 00:02:33,350 --> 00:02:35,990 like this onto the network. 36 00:02:36,200 --> 00:02:37,830 I mean, that doesn't make any sense today. 37 00:02:37,850 --> 00:02:39,470 Devices are getting so small. 38 00:02:39,860 --> 00:02:45,320 I mean, it doesn't make sense to try and connect an Ethernet cable to a bulb. 39 00:02:45,860 --> 00:02:47,030 What about your phone? 40 00:02:47,060 --> 00:02:54,050 I mean, can you imagine having to connect an Ethernet cable to a phone and then having to be connected 41 00:02:54,050 --> 00:02:58,820 to a physical network so you can't walk around with your mobile device? 42 00:02:58,910 --> 00:03:02,180 The whole point about a mobile device is it's mobile. 43 00:03:02,210 --> 00:03:07,580 I can move this around and still be connected to the network without any problems. 44 00:03:08,060 --> 00:03:15,710 Now, that is a big difference between, say, a wired connection, which in this example is using fiber. 45 00:03:17,540 --> 00:03:23,270 Notice the difference here, this fiber connection and he has the light going through the fiber cable 46 00:03:23,960 --> 00:03:32,810 is contained or constrained within this cable, so the signal stays within the cable. 47 00:03:32,840 --> 00:03:38,210 Now, if I bend it really badly, I can get some of the light to come out of the cable. 48 00:03:38,210 --> 00:03:39,380 That's not a good idea. 49 00:03:39,800 --> 00:03:44,900 Bending the cable does affect the transmission, especially on multimode fiber. 50 00:03:45,410 --> 00:03:51,500 The idea, however, here is the signal is contained within the cable. 51 00:03:52,040 --> 00:03:59,420 There are advantages, however, to using wide connections such as this compared to wi fi. 52 00:03:59,750 --> 00:04:02,240 The first thing is typically you can go a lot further. 53 00:04:02,240 --> 00:04:05,780 So with light as an example, we can go a lot further. 54 00:04:05,810 --> 00:04:09,020 The cables under the sea are fiber cables. 55 00:04:09,020 --> 00:04:15,110 We can go much further in distance than we would with the wi fi connections that we have in our homes 56 00:04:15,110 --> 00:04:16,100 or in companies. 57 00:04:16,130 --> 00:04:22,200 Now, there is a difference between the signals used in a wi fi network versus a cellular network. 58 00:04:22,220 --> 00:04:23,990 They use different frequencies. 59 00:04:24,290 --> 00:04:29,330 Governments around the world dictate which frequencies are available for which applications. 60 00:04:29,330 --> 00:04:35,690 So applications such as 3G, 4G, 5G use a certain range of frequencies. 61 00:04:35,690 --> 00:04:38,390 WI FI uses a different range of frequencies. 62 00:04:38,390 --> 00:04:40,180 And we'll talk more about those in a moment. 63 00:04:40,190 --> 00:04:46,880 We have two main bands that we need to know about, and that's 2.4 gigahertz and five gigahertz bands. 64 00:04:46,880 --> 00:04:52,550 Typically, the lower the frequency, the further the transmission, but the lower the data rate or 65 00:04:52,550 --> 00:04:53,360 the throughput. 66 00:04:53,540 --> 00:04:58,250 Five gigahertz, as an example, can't go as far as 2.4 gigahertz. 67 00:04:58,250 --> 00:05:01,580 It also can be absorbed a lot more easily. 68 00:05:01,580 --> 00:05:08,270 So as an example, five gigahertz gets absorbed a lot more by a concrete wall or brick wall compared 69 00:05:08,270 --> 00:05:09,710 to 2.4 gigahertz. 70 00:05:09,710 --> 00:05:15,320 So if you want further distance or you want to go through walls as an example, it's better in some 71 00:05:15,320 --> 00:05:20,570 cases to use 2.4 gigahertz than five gigahertz, but five gigahertz allows for higher throughput or 72 00:05:20,570 --> 00:05:22,820 more data transmission through the network. 73 00:05:22,820 --> 00:05:26,420 So there's always advantages and disadvantages to any technology that you use. 74 00:05:27,020 --> 00:05:30,680 Copper cables are generally a lot easier to work with than fiber cables. 75 00:05:30,770 --> 00:05:35,090 If a cable breaks, it's easier to repair that using copper than fiber. 76 00:05:35,090 --> 00:05:36,380 But fiber is more secure. 77 00:05:36,380 --> 00:05:42,950 So if you want more security as an example, in a military environment, it's much harder to tap into 78 00:05:42,950 --> 00:05:45,410 a fiber connection than it is a copper connection. 79 00:05:45,410 --> 00:05:47,810 So you may want to use fiber rather than copper. 80 00:05:47,810 --> 00:05:50,870 Fiber can go longer distances than copper can. 81 00:05:50,990 --> 00:05:54,320 But in this part of the course, we are concentrating on wi fi. 82 00:05:54,320 --> 00:05:56,840 And I'm going to talk about the different Wi-Fi standards. 83 00:05:56,840 --> 00:05:58,520 You need to know that for the exam. 84 00:05:58,520 --> 00:06:00,410 We're going to talk about the different frequencies. 85 00:06:00,410 --> 00:06:02,600 I've mentioned 2.4 gigahertz and five gigahertz. 86 00:06:02,600 --> 00:06:05,330 So those are the two ones that that you need to remember. 87 00:06:05,330 --> 00:06:07,010 We're going to talk about channels. 88 00:06:07,130 --> 00:06:09,650 I'm also going to talk about some of the issues using wi fi. 89 00:06:09,680 --> 00:06:12,170 You've probably experienced a lot of these already. 90 00:06:12,170 --> 00:06:18,020 So as an example, if you move to a certain part of a room or a building, you get a dead spot where 91 00:06:18,020 --> 00:06:19,490 you can't get a connection. 92 00:06:19,490 --> 00:06:25,040 You move a few meters or a few feet away, you get a better signal or better transmission. 93 00:06:25,040 --> 00:06:30,260 So there are a lot of advantages to using wi fi, but there are also disadvantages to using wi fi. 94 00:06:30,260 --> 00:06:32,750 One of the big ones is security. 95 00:06:32,750 --> 00:06:40,190 I can use Kaili Linux as an example with a wi fi adapter and I can listen in on your conversation. 96 00:06:40,190 --> 00:06:43,070 WI fi is a hub now. 97 00:06:43,070 --> 00:06:47,000 A lot of people tell me, David, there's no point learning about hubs, but if you don't understand 98 00:06:47,000 --> 00:06:50,810 what a hub is, then you don't understand that wi fi acts like a hub. 99 00:06:50,840 --> 00:06:55,340 In other words, we're using the same frequency in the air. 100 00:06:55,370 --> 00:07:00,650 If I listen in on the same frequency that you're transmitting at, I can hear your conversation. 101 00:07:00,800 --> 00:07:02,570 I mean, we as humans can do that. 102 00:07:02,570 --> 00:07:10,730 You and I are speaking and listening on the same frequency ranges humans can hear at a certain frequency. 103 00:07:10,730 --> 00:07:15,020 Now, obviously, older people generally have worse hearing than younger people. 104 00:07:15,050 --> 00:07:19,430 Younger people can hear a wider range of frequencies than older people. 105 00:07:19,610 --> 00:07:26,360 But for the most part, we are listening on a certain band of frequencies if you speak. 106 00:07:26,440 --> 00:07:27,730 And I stand near you. 107 00:07:27,730 --> 00:07:28,760 I can hear you. 108 00:07:28,780 --> 00:07:33,580 Now, you may be talking to someone else, but if I stand near enough, I can hear your conversation. 109 00:07:33,580 --> 00:07:35,320 And the same is true in wi fi. 110 00:07:35,350 --> 00:07:39,580 If you speak, depending on the antenna, you have what are called directional antennas that will send 111 00:07:39,580 --> 00:07:41,610 a signal only in certain in one direction. 112 00:07:41,620 --> 00:07:42,700 It's kind of like a torch. 113 00:07:42,700 --> 00:07:45,610 We would take a beam and then we can direct the beam. 114 00:07:45,610 --> 00:07:51,190 So we directing it in a certain direction, but an omnidirectional antenna, which is what a lot of 115 00:07:51,190 --> 00:07:55,020 organizations use, will send the signal in all directions. 116 00:07:55,030 --> 00:07:58,870 So you get different types of signals, different kinds of devices that bridges, in example, will 117 00:07:58,870 --> 00:08:00,700 push the signal in a certain direction. 118 00:08:00,700 --> 00:08:04,390 An omnidirectional or all direction antenna sends the signal everywhere. 119 00:08:04,480 --> 00:08:11,860 So if you speaking to that wireless access point and I'm in the vicinity, I'll be able to hear your 120 00:08:11,860 --> 00:08:12,760 transmission. 121 00:08:12,760 --> 00:08:16,540 So security is a big problem in wi fi networks. 122 00:08:16,540 --> 00:08:21,810 In the past, we had mechanisms to encrypt data, but they were weak and they could be cracked. 123 00:08:21,820 --> 00:08:27,340 Today we use better encryption and authentication methods, but once again they can also be cracked. 124 00:08:27,340 --> 00:08:32,140 If someone knows what they're doing and you're using a weak password, it's important to use strong 125 00:08:32,140 --> 00:08:37,150 passwords and strong authentication mechanisms, especially in corporate environments. 126 00:08:38,110 --> 00:08:38,350 Okay. 127 00:08:38,350 --> 00:08:39,760 So I've been talking now for a long time. 128 00:08:39,760 --> 00:08:42,520 I think it's time to jump into the details of wi fi.