1 1 00:00:00,590 --> 00:00:02,680 The TCP/IP model. 2 2 00:00:02,680 --> 00:00:04,540 Now, if you remember all the way back out 3 3 00:00:04,540 --> 00:00:06,790 when I started talking about the OSI model, 4 4 00:00:06,790 --> 00:00:09,810 we mentioned that the OSI model was a reference model, 5 5 00:00:09,810 --> 00:00:12,390 but it wasn't the only reference model out there. 6 6 00:00:12,390 --> 00:00:13,750 And the other one that we're going to talk about 7 7 00:00:13,750 --> 00:00:16,090 is known as the TCP/IP model. 8 8 00:00:16,090 --> 00:00:19,970 This is also called the TCP/IP stack or the DoD model 9 9 00:00:19,970 --> 00:00:22,840 named for the Department of Defense who created it. 10 10 00:00:22,840 --> 00:00:26,380 Now, the TCP/IP model is an alternative to the OSI model. 11 11 00:00:26,380 --> 00:00:28,800 And the nice thing is it's actually only four layers 12 12 00:00:28,800 --> 00:00:31,530 instead of the seven layers of our OSI model. 13 13 00:00:31,530 --> 00:00:33,000 This is going to make it a little bit easier 14 14 00:00:33,000 --> 00:00:34,490 for most people to understand. 15 15 00:00:34,490 --> 00:00:37,010 And it's also easier for us to learn this model. 16 16 00:00:37,010 --> 00:00:38,730 Now, it's also going to be a little bit more relevant 17 17 00:00:38,730 --> 00:00:40,250 than the OSI model today 18 18 00:00:40,250 --> 00:00:42,500 because almost all computer networks these days 19 19 00:00:42,500 --> 00:00:44,210 are TCP/IP-based 20 20 00:00:44,210 --> 00:00:47,200 and the TCP/IP model refers specifically 21 21 00:00:47,200 --> 00:00:49,440 to those four layers and how things work 22 22 00:00:49,440 --> 00:00:50,870 in today's modern networks. 23 23 00:00:50,870 --> 00:00:52,970 Whereas the OSI model is going to sometimes 24 24 00:00:52,970 --> 00:00:55,320 be a little bit more blurry as you're trying to force things 25 25 00:00:55,320 --> 00:00:57,540 into those seven individual layers. 26 26 00:00:57,540 --> 00:01:01,690 So how does the OSI model compare to the TCP/IP model? 27 27 00:01:01,690 --> 00:01:04,230 Well, I already mentioned that there's four layers in one 28 28 00:01:04,230 --> 00:01:05,430 and seven and the other. 29 29 00:01:05,430 --> 00:01:06,600 Let's take a look at that. 30 30 00:01:06,600 --> 00:01:09,130 So how exactly does the OSI model compare 31 31 00:01:09,130 --> 00:01:10,840 to the TCP/IP model? 32 32 00:01:10,840 --> 00:01:12,750 Well, it's actually pretty simple. 33 33 00:01:12,750 --> 00:01:15,760 If I take layers five, six, and seven from the OSI model, 34 34 00:01:15,760 --> 00:01:18,810 those top three layers, and I smash them all together, 35 35 00:01:18,810 --> 00:01:21,040 I get something known as the application layer 36 36 00:01:21,040 --> 00:01:23,220 inside the TCP/IP model. 37 37 00:01:23,220 --> 00:01:24,670 Now, the application layer here 38 38 00:01:24,670 --> 00:01:27,820 is going to contain application, presentation and session, 39 39 00:01:27,820 --> 00:01:29,790 all of those OSI model functions, 40 40 00:01:29,790 --> 00:01:32,370 into a single layer called the application layer 41 41 00:01:32,370 --> 00:01:34,350 under the TCP/IP model. 42 42 00:01:34,350 --> 00:01:36,980 Next, we have the transport layer from the OSI model, 43 43 00:01:36,980 --> 00:01:38,350 and this one is really easy 44 44 00:01:38,350 --> 00:01:40,400 because we're just going to take it and move it right in 45 45 00:01:40,400 --> 00:01:41,910 to the TCP/IP model. 46 46 00:01:41,910 --> 00:01:44,100 Everything the way that it was in the OSI model 47 47 00:01:44,100 --> 00:01:45,570 still applies here. 48 48 00:01:45,570 --> 00:01:48,660 Next, we get down to the network layer of the OSI model. 49 49 00:01:48,660 --> 00:01:50,150 Here, we're going to take this layer 50 50 00:01:50,150 --> 00:01:53,020 and move it straight over to the TCP/IP model as well. 51 51 00:01:53,020 --> 00:01:55,800 But when we do that, we're going to change its name. 52 52 00:01:55,800 --> 00:01:58,420 Instead of calling it the network layer under the OSI model, 53 53 00:01:58,420 --> 00:01:59,810 we're going to call it the internet layer 54 54 00:01:59,810 --> 00:02:01,600 inside the TCP/IP model, 55 55 00:02:01,600 --> 00:02:04,560 because it really is all about routing things externally, 56 56 00:02:04,560 --> 00:02:07,940 either to or from the internet, from within our networks. 57 57 00:02:07,940 --> 00:02:09,630 Then we have our final two layers 58 58 00:02:09,630 --> 00:02:11,160 at the bottom of the OSI model. 59 59 00:02:11,160 --> 00:02:13,570 This is our data link and our physical layers. 60 60 00:02:13,570 --> 00:02:15,060 These two layers are going to be combined 61 61 00:02:15,060 --> 00:02:16,680 under the TCP/IP model 62 62 00:02:16,680 --> 00:02:18,770 and called the network interface layer 63 63 00:02:18,770 --> 00:02:20,810 because this is how our users are going to interface 64 64 00:02:20,810 --> 00:02:23,030 with our networks and connect to them. 65 65 00:02:23,030 --> 00:02:25,060 So as you can see, this is pretty simple 66 66 00:02:25,060 --> 00:02:27,040 when you start looking at the OSI model 67 67 00:02:27,040 --> 00:02:29,870 versus the TCP/IP model in this way. 68 68 00:02:29,870 --> 00:02:31,450 You basically take the top three layers 69 69 00:02:31,450 --> 00:02:32,860 and you squish them all together. 70 70 00:02:32,860 --> 00:02:34,540 And this gives you the application layer. 71 71 00:02:34,540 --> 00:02:35,760 You take those bottom two layers 72 72 00:02:35,760 --> 00:02:37,030 and you squish those together 73 73 00:02:37,030 --> 00:02:39,300 and you move them over into the TCP/IP model. 74 74 00:02:39,300 --> 00:02:42,100 And that's how you go from seven layers of the OSI model, 75 75 00:02:42,100 --> 00:02:44,730 into the four layers of the TCP/IP model, 76 76 00:02:44,730 --> 00:02:46,900 by making sure you squish those top three 77 77 00:02:46,900 --> 00:02:49,210 and squish those bottom two layers together. 78 78 00:02:49,210 --> 00:02:52,640 Now, for the exam, you need to understand the TCP/IP model 79 79 00:02:52,640 --> 00:02:53,580 and it's layers. 80 80 00:02:53,580 --> 00:02:56,590 So if you can draw this diagram, you're going to be covered 81 81 00:02:56,590 --> 00:02:57,770 because you already know 82 82 00:02:57,770 --> 00:02:59,960 everything else you're going to need for test. 83 83 00:02:59,960 --> 00:03:01,320 See, what we're dealing with here 84 84 00:03:01,320 --> 00:03:03,860 is knowing what those seven layers are of the OSI model 85 85 00:03:03,860 --> 00:03:06,430 and how they represent themselves inside the four layers 86 86 00:03:06,430 --> 00:03:08,040 of the TCP/IP model. 87 87 00:03:08,040 --> 00:03:10,040 We already learned all about those seven layers individually 88 88 00:03:10,040 --> 00:03:11,110 in the OSI model. 89 89 00:03:11,110 --> 00:03:13,540 So that knowledge is going to carry over too. 90 90 00:03:13,540 --> 00:03:15,870 Now, let's take a quick look at these four layers 91 91 00:03:15,870 --> 00:03:19,100 in the TCP/IP model as a review from our days 92 92 00:03:19,100 --> 00:03:20,680 using the OSI model. 93 93 00:03:20,680 --> 00:03:22,110 First, starting at the bottom, 94 94 00:03:22,110 --> 00:03:24,090 we have the network interface layer. 95 95 00:03:24,090 --> 00:03:25,200 This is layer one. 96 96 00:03:25,200 --> 00:03:27,830 And it's all about physical and electrical characteristics, 97 97 00:03:27,830 --> 00:03:29,640 just like in the OSI model. 98 98 00:03:29,640 --> 00:03:30,760 Now here, we're going to describe 99 99 00:03:30,760 --> 00:03:32,810 how we're going to transmit bits across our networks, 100 100 00:03:32,810 --> 00:03:35,580 those ones and zeros that we had in our physical layer. 101 101 00:03:35,580 --> 00:03:36,840 It's also going to determine 102 102 00:03:36,840 --> 00:03:38,890 which type of network medium we're going to use. 103 103 00:03:38,890 --> 00:03:40,940 Are we going to be using twisted pair copper cabling, 104 104 00:03:40,940 --> 00:03:43,300 coaxial cable, fiber optic cable? 105 105 00:03:43,300 --> 00:03:44,480 What do we want to use here? 106 106 00:03:44,480 --> 00:03:46,110 Maybe we're going to use wireless. 107 107 00:03:46,110 --> 00:03:47,910 Are we going to run TCP over ethernet 108 108 00:03:47,910 --> 00:03:49,880 or are we going to use token ring, serial, 109 109 00:03:49,880 --> 00:03:51,460 or some other type of network? 110 110 00:03:51,460 --> 00:03:52,560 All of this gets put together 111 111 00:03:52,560 --> 00:03:54,730 inside our network interface layer. 112 112 00:03:54,730 --> 00:03:57,220 The second layer we have is known as the internet layer 113 113 00:03:57,220 --> 00:03:59,200 inside the TCP/IP model. 114 114 00:03:59,200 --> 00:04:01,040 This is where we take data and package it 115 115 00:04:01,040 --> 00:04:02,770 into those IP datagrams, 116 116 00:04:02,770 --> 00:04:05,950 just like we did with layer three of the OSI model of four. 117 117 00:04:05,950 --> 00:04:07,540 Now, it's going to contain your source 118 118 00:04:07,540 --> 00:04:08,900 and your destination IPs, 119 119 00:04:08,900 --> 00:04:10,570 and it's going to forward those datagrams 120 120 00:04:10,570 --> 00:04:13,040 between different hosts across the networks. 121 121 00:04:13,040 --> 00:04:13,873 These data grams 122 122 00:04:13,873 --> 00:04:16,110 are going to be pushed around the networks through routing, 123 123 00:04:16,110 --> 00:04:17,770 and we're going to use our routers to do this. 124 124 00:04:17,770 --> 00:04:19,720 And this connectivity is usually going to occur 125 125 00:04:19,720 --> 00:04:22,820 externally from your network to some remote network. 126 126 00:04:22,820 --> 00:04:24,810 This is where your internet is going to get connected 127 127 00:04:24,810 --> 00:04:25,970 to the intranet. 128 128 00:04:25,970 --> 00:04:28,570 This is internal versus external. 129 129 00:04:28,570 --> 00:04:31,620 Now, examples of the internet layer and TCP/IP 130 130 00:04:31,620 --> 00:04:35,820 include things like IP, ICMP, ARP, and Reverse ARP. 131 131 00:04:35,820 --> 00:04:38,290 And we're going to talk all about these things in more depth 132 132 00:04:38,290 --> 00:04:39,990 as we go through switching and routing 133 133 00:04:39,990 --> 00:04:41,510 later on in this course. 134 134 00:04:41,510 --> 00:04:44,360 Now, I understand I just threw a bunch of acronyms at you, 135 135 00:04:44,360 --> 00:04:46,400 but I promise I'm going to come back to them later 136 136 00:04:46,400 --> 00:04:47,430 and I'm going to teach you all about them. 137 137 00:04:47,430 --> 00:04:49,490 So don't worry about them yet. 138 138 00:04:49,490 --> 00:04:50,970 Next, we have our third layer. 139 139 00:04:50,970 --> 00:04:52,167 This is the transport layer, 140 140 00:04:52,167 --> 00:04:54,500 and it's exactly the same as the transport layer 141 141 00:04:54,500 --> 00:04:56,040 in the OSI model. 142 142 00:04:56,040 --> 00:04:57,690 It's going to define the level of service 143 143 00:04:57,690 --> 00:05:00,540 and the status of the connection being used by TCP, 144 144 00:05:00,540 --> 00:05:02,380 UDP, or RTP. 145 145 00:05:02,380 --> 00:05:04,560 TCP is our connection full protocol. 146 146 00:05:04,560 --> 00:05:06,540 UDP is our connectionless protocol, 147 147 00:05:06,540 --> 00:05:08,720 and RTP is our real-time protocol, 148 148 00:05:08,720 --> 00:05:11,580 which is normally used for streaming voice and video. 149 149 00:05:11,580 --> 00:05:13,850 The fourth and final layer of the TCP/IP model 150 150 00:05:13,850 --> 00:05:15,340 is the application layer. 151 151 00:05:15,340 --> 00:05:17,080 And this is going to combine the top three layers 152 152 00:05:17,080 --> 00:05:19,210 of the OSI model into a single layer 153 153 00:05:19,210 --> 00:05:20,770 to define the application protocol 154 154 00:05:20,770 --> 00:05:22,060 that we're going to be using. 155 155 00:05:22,060 --> 00:05:23,780 This is also going to dictate how the programs 156 156 00:05:23,780 --> 00:05:25,460 are going to interface with the transport layer 157 157 00:05:25,460 --> 00:05:27,010 by conducting session management. 158 158 00:05:27,010 --> 00:05:28,340 And it's going to be the layer 159 159 00:05:28,340 --> 00:05:30,300 where the user is going to interact with the network 160 160 00:05:30,300 --> 00:05:32,010 through some sort of program. 161 161 00:05:32,010 --> 00:05:34,750 Examples of this come from layers five, six, and seven 162 162 00:05:34,750 --> 00:05:36,050 of the OSI model, 163 163 00:05:36,050 --> 00:05:38,340 again, because we squished all three of those down 164 164 00:05:38,340 --> 00:05:40,410 into this one application layer. 165 165 00:05:40,410 --> 00:05:42,640 This would be things like the Hypertext Transfer Protocol 166 166 00:05:42,640 --> 00:05:45,410 for web browsing, Telnet for remote control, 167 167 00:05:45,410 --> 00:05:48,970 FTP for file transfer, SSH for remote shell, 168 168 00:05:48,970 --> 00:05:50,810 SNMP for network management, 169 169 00:05:50,810 --> 00:05:54,840 DNS for domain name resolution, SMTP for sending mail, 170 170 00:05:54,840 --> 00:05:58,570 an SSL or TLS for secure web browsing and encryption. 171 171 00:05:58,570 --> 00:06:00,290 All of these things are going to be found here 172 172 00:06:00,290 --> 00:06:03,150 in the application layer of the TCP/IP model. 173 173 00:06:03,150 --> 00:06:03,983 All right. 174 174 00:06:03,983 --> 00:06:06,710 So what are we going to cover in this section of the course? 175 175 00:06:06,710 --> 00:06:08,170 Well, we're going to be focused again 176 176 00:06:08,170 --> 00:06:10,590 on domain one, networking fundamentals, 177 177 00:06:10,590 --> 00:06:12,953 and we're going to cover objectives 1.1 and 1.5. 178 178 00:06:13,890 --> 00:06:16,550 Objective 1.1 says that you must be able to compare 179 179 00:06:16,550 --> 00:06:18,230 and contrast the OSI model layers 180 180 00:06:18,230 --> 00:06:20,100 and encapsulation concepts. 181 181 00:06:20,100 --> 00:06:22,720 Objective 1.5 states that you must be able to explain 182 182 00:06:22,720 --> 00:06:24,160 common ports and protocols, 183 183 00:06:24,160 --> 00:06:26,700 their applications and encrypted alternatives. 184 184 00:06:26,700 --> 00:06:28,980 We're also going to briefly dive into domain five, 185 185 00:06:28,980 --> 00:06:31,730 network troubleshooting, by returning to objective 5.3. 186 186 00:06:32,567 --> 00:06:36,050 Objective 5.3 states that given a scenario, you need to use 187 187 00:06:36,050 --> 00:06:38,880 the appropriate network software tools and commands. 188 188 00:06:38,880 --> 00:06:39,910 So in this section, 189 189 00:06:39,910 --> 00:06:41,930 we're specifically going to be doing some hands-on work 190 190 00:06:41,930 --> 00:06:43,920 with Nmap, the network mapper tool, 191 191 00:06:43,920 --> 00:06:45,610 to show you how this works. 192 192 00:06:45,610 --> 00:06:47,920 All right, let's get started talking all about ports 193 193 00:06:47,920 --> 00:06:50,200 and protocols using the TCP/IP model 194 194 00:06:50,200 --> 00:06:51,700 in this section of the course.