1 00:00:12,390 --> 00:00:14,440 In this video I'm going to discuss Wi-Fi. 2 00:00:14,440 --> 00:00:18,350 Wi-Fi is so important I think for many of us today. 3 00:00:18,400 --> 00:00:21,070 There's no question why we need to learn this. 4 00:00:21,370 --> 00:00:27,060 It's really good that Cisco have put it back into the CCMA in the really old CCMA. 5 00:00:27,130 --> 00:00:30,870 They had Wi-Fi then it was removed but now it's back. 6 00:00:30,880 --> 00:00:34,450 Wi-Fi is really really important in today's networks. 7 00:00:34,480 --> 00:00:39,370 Can you imagine life today without Wi-Fi or wireless connections. 8 00:00:39,370 --> 00:00:45,280 We today take it for granted that we going to have Wi-Fi when we go to the office or a coffee shop or 9 00:00:45,280 --> 00:00:46,890 even for a lot of us at home. 10 00:00:46,960 --> 00:00:50,610 When we book a hotel we expect Wi-Fi connections. 11 00:00:50,650 --> 00:00:57,040 How many of you I mean I do this all the time but do you do this when you check a new hotel that you 12 00:00:57,040 --> 00:00:57,880 want to stay in. 13 00:00:57,910 --> 00:01:02,040 Do you make sure that they've got Wi-Fi or an Air B and B. 14 00:01:02,080 --> 00:01:08,170 I really like air BMD but one of the first things that I'll check is if they have Wi-Fi I'll consider 15 00:01:08,170 --> 00:01:08,670 staying there. 16 00:01:08,680 --> 00:01:11,430 If they don't have Wi-Fi I won't consider staying there. 17 00:01:11,440 --> 00:01:15,750 They have to have Wi-Fi it's that important for so many of us today. 18 00:01:15,880 --> 00:01:16,140 Okay. 19 00:01:16,150 --> 00:01:22,030 Now there's obviously a big difference between Wi-Fi connections and cable connections in the bad old 20 00:01:22,030 --> 00:01:23,140 days. 21 00:01:23,360 --> 00:01:27,430 And I've got a old laptop here in the bad old days. 22 00:01:27,430 --> 00:01:31,410 Laptops such as these had Ethernet connections bolting. 23 00:01:31,780 --> 00:01:38,140 So I would be able to connect a ethernet cable directly to the laptop but modern laptops don't have 24 00:01:38,140 --> 00:01:38,450 that. 25 00:01:38,470 --> 00:01:43,150 I mean your laptop maybe you've got a Mac or a P.C.. 26 00:01:43,150 --> 00:01:48,680 They typically don't have any connections for Ethernet cables. 27 00:01:48,760 --> 00:01:53,520 They can only connect to the network or to the Internet using Wi-Fi. 28 00:01:55,200 --> 00:02:02,670 If I wanted to add an Ethan connection to this laptop as an example I have to plug in a USP ethernet 29 00:02:02,670 --> 00:02:08,090 adapter and then I can add this to a wired network. 30 00:02:08,190 --> 00:02:13,970 So for a lot of us today a lot of devices only support Wi-Fi. 31 00:02:14,400 --> 00:02:21,740 A lot of devices today don't support wired connections that's especially true I think with devices such 32 00:02:21,740 --> 00:02:23,630 as these IO T devices. 33 00:02:23,630 --> 00:02:28,180 I mean this is a huge bold it seems ridiculous. 34 00:02:28,200 --> 00:02:35,840 But in the past I would have had to have used Ethan a cable to get a device like this onto the network. 35 00:02:36,370 --> 00:02:37,850 I mean that doesn't make any sense today. 36 00:02:37,870 --> 00:02:39,800 Devices are getting so small. 37 00:02:39,970 --> 00:02:46,010 I mean it doesn't make sense to try and connected ethernet cable to a bulb. 38 00:02:46,030 --> 00:02:47,200 What about your phone. 39 00:02:47,230 --> 00:02:54,010 I mean can you imagine having to connect it even a cable to a phone and then having to be connected 40 00:02:54,040 --> 00:02:59,110 to a physical network so you can't walk around with your mobile device. 41 00:02:59,110 --> 00:03:02,170 The whole point about a mobile device is it's mobile. 42 00:03:02,260 --> 00:03:08,260 I can move this around and still be connected to the network without any problems. 43 00:03:08,260 --> 00:03:17,940 Now that is a big difference between say a wired connection which in this example is using fiber notice 44 00:03:17,940 --> 00:03:19,110 the difference here. 45 00:03:19,110 --> 00:03:26,400 This fiber connection and has the light going through the fiber cable is contained or constrained with 46 00:03:26,470 --> 00:03:29,070 in this cable. 47 00:03:29,070 --> 00:03:32,900 So the signal stays within the cable. 48 00:03:32,940 --> 00:03:38,250 And if I bend it really badly I can get some of the light to come out of the cable. 49 00:03:38,250 --> 00:03:39,910 That's not a good idea. 50 00:03:39,960 --> 00:03:45,560 Bending the cable does affect the transmission especially on multi-modal fiber. 51 00:03:45,570 --> 00:03:52,160 The idea however here is the signal is contained within the cable. 52 00:03:52,170 --> 00:03:59,660 There are advantages however to using wide connections such as this compared to Wi-Fi. 53 00:03:59,790 --> 00:04:02,280 The first thing is typically you can go a lot further. 54 00:04:02,340 --> 00:04:05,790 So with light as an example we can go a lot further. 55 00:04:05,970 --> 00:04:12,810 The cables under the sea of fiber cables we can go much further in distance than we would with the Wi-Fi 56 00:04:12,810 --> 00:04:16,230 connections that we have in our homes or in companies. 57 00:04:16,230 --> 00:04:22,350 Now there is a difference between the signals used in a Wi-Fi network versus a cellular network. 58 00:04:22,380 --> 00:04:24,280 They use different frequencies. 59 00:04:24,360 --> 00:04:30,570 Governments around the world dictate which frequencies are available for which applications so applications 60 00:04:30,570 --> 00:04:38,520 such as 3G 4G 5G use a certain range of frequencies Wi-Fi uses a different range of frequencies and 61 00:04:38,520 --> 00:04:40,230 we'll talk more about those in a moment. 62 00:04:40,230 --> 00:04:46,710 We have two main bands that we need to know about and that's 2.5 gigahertz and 5 gigahertz bands. 63 00:04:47,070 --> 00:04:53,190 Typically the lower the frequency the further the transmission but the lower the data rate or the throughput 64 00:04:53,650 --> 00:04:58,470 5 gigahertz as an example can't go as far as 2.5 gigahertz. 65 00:04:58,470 --> 00:05:01,670 It also can be absorbed a lot more easily. 66 00:05:01,740 --> 00:05:09,030 So as an example 5 gigahertz gets absorbed a lot more by a concrete wall or brick wall compared to 2.5 67 00:05:09,030 --> 00:05:09,840 gigahertz. 68 00:05:09,840 --> 00:05:15,690 So if you want further distance or you want to go through walls as an example it's better in some cases 69 00:05:15,690 --> 00:05:21,660 to use 2.5 gigahertz than 5 gigahertz but 5 gigahertz allows for higher throughput or more data transmission 70 00:05:21,960 --> 00:05:22,950 through the network. 71 00:05:23,010 --> 00:05:27,060 So there's always advantages and disadvantages to any technology that you use. 72 00:05:27,060 --> 00:05:30,960 Copper cables are generally a lot easier to work with than fiber cables. 73 00:05:30,960 --> 00:05:36,360 If a cable breaks it's easier to repair that we're using copper than fiber but fiber is more secure. 74 00:05:36,360 --> 00:05:43,020 So if you want more security as an example in a military environment it's much harder to tap into a 75 00:05:43,020 --> 00:05:45,440 fiber connection than it is a copper connection. 76 00:05:45,570 --> 00:05:50,700 So you may want to use fiber rather than copper fiber can go longer distances than copper can. 77 00:05:51,180 --> 00:05:56,070 But in this part of the course we are concentrating on Wi-Fi and I'm going to talk about the different 78 00:05:56,070 --> 00:05:56,870 Wi-Fi standards. 79 00:05:56,880 --> 00:06:00,870 You need to know that for the exam we're going to talk about the different frequencies I've mentioned 80 00:06:00,870 --> 00:06:02,840 2.5 gigahertz and 5 gigahertz. 81 00:06:02,880 --> 00:06:05,390 Those are the two ones that you need to remember. 82 00:06:05,460 --> 00:06:07,110 We're going to talk about channels. 83 00:06:07,230 --> 00:06:09,570 I'm also going to talk about some of the issues using Wi-Fi. 84 00:06:09,840 --> 00:06:12,260 You've probably experienced a lot of these already. 85 00:06:12,360 --> 00:06:18,210 So as an example if you move to a certain part of a room or a building you get a dead spot where you 86 00:06:18,270 --> 00:06:19,580 can't get a connection. 87 00:06:19,680 --> 00:06:25,200 You move a few meters or a few feet away you get a better signal or better transmission. 88 00:06:25,200 --> 00:06:30,490 So there are a lot of advantages to using Wi-Fi but there are also disadvantages to using Wi-Fi. 89 00:06:30,510 --> 00:06:32,740 One of the big ones is security. 90 00:06:32,850 --> 00:06:40,380 I can use Kelly Linux as an example with a Wi-Fi adapter and I can listen in on your conversation. 91 00:06:40,380 --> 00:06:46,590 Wi-Fi is a hub now a lot of people tell me David there's no point learning about hubs but if you don't 92 00:06:46,590 --> 00:06:51,050 understand what a hub is then you don't understand that Wi-Fi acts like a hub. 93 00:06:51,060 --> 00:06:55,430 In other words we are using the same frequency in the air. 94 00:06:55,500 --> 00:07:00,890 If I listen in on the same frequency that you're transmitting at I can hear your conversation. 95 00:07:00,990 --> 00:07:02,660 I mean we as humans can do that. 96 00:07:02,670 --> 00:07:08,010 You and I are speaking and listening on the same frequency ranges. 97 00:07:08,070 --> 00:07:14,160 Humans can hear at a certain frequency now obviously older people generally have worse hearing than 98 00:07:14,160 --> 00:07:15,150 younger people. 99 00:07:15,150 --> 00:07:22,620 Younger people can hear a wide range of frequencies than older people but for the most part we are listening 100 00:07:22,620 --> 00:07:24,840 on a certain band of frequencies. 101 00:07:24,870 --> 00:07:29,010 If you speak and I stand near you I can hear you. 102 00:07:29,010 --> 00:07:33,960 Now you may be talking to someone else but if I stand near enough I can hear your conversation and the 103 00:07:33,960 --> 00:07:35,550 same is true and Wi-Fi. 104 00:07:35,550 --> 00:07:39,630 If you speak depending on the antenna you have what are called directional antennas that will send a 105 00:07:39,630 --> 00:07:45,030 signal only in certain in one direction it's kind of like a torch will take a beam and then we can direct 106 00:07:45,030 --> 00:07:50,880 the beam so redirecting it in a certain direction but an omnidirectional antenna which is what a lot 107 00:07:50,880 --> 00:07:55,110 of organizations use will send the signal in all directions. 108 00:07:55,260 --> 00:07:59,250 So you get different types of signals different kinds of devices a bridge as an example will push the 109 00:07:59,250 --> 00:08:04,670 signal in a certain direction and omnidirectional or all direction and Tennant sends the signal everywhere. 110 00:08:04,710 --> 00:08:11,850 So if you are speaking to that wireless access point and I'm in the vicinity I'll be able to hear your 111 00:08:11,850 --> 00:08:12,950 transmission. 112 00:08:12,990 --> 00:08:17,280 So security is a big problem in Wi-Fi networks in the past. 113 00:08:17,280 --> 00:08:21,960 We had mechanisms to encrypt data but they were weak and they could be cracked. 114 00:08:21,960 --> 00:08:25,320 Today we use better encryption and authentication methods. 115 00:08:25,410 --> 00:08:27,340 But once again they can also be cracked. 116 00:08:27,360 --> 00:08:32,760 If someone knows what they doing and you using a weak password it's important to use strong passwords 117 00:08:32,820 --> 00:08:38,010 and strong authentication mechanisms especially in corporate environments. 118 00:08:38,210 --> 00:08:39,800 Okay so I've been talking now for a long time. 119 00:08:39,800 --> 00:08:42,320 I think it's time to jump into the details of Wi-Fi.