WEBVTT 00:01.100 --> 00:08.540 So I had some time to kill recently and I was on YouTube checking out channel of a colleague and there 00:08.540 --> 00:15.980 was such an interesting discussion going on over there and that was about should we be teaching the 00:15.980 --> 00:17.890 OSSI model anymore? 00:17.900 --> 00:24.750 And they were, you know, discussing this in any technical trainer type of a context, right? 00:24.770 --> 00:28.520 If you're teaching cybersecurity, should you teach the OSCE model? 00:28.520 --> 00:31.820 If you're teaching just basic networking, should you teach it? 00:32.030 --> 00:34.250 Should you teach it if you're teaching a plus? 00:34.250 --> 00:41.690 And I really couldn't even believe it was being discussed because I think we have to teach the OSCE 00:41.720 --> 00:45.380 model for a whole bunch of important reasons. 00:45.560 --> 00:48.920 And I really do mean it when I say we have to teach it. 00:49.370 --> 00:56.360 One of the reasons I believe this is true is because of the fact that this terminology of layers is 00:56.360 --> 01:02.990 just so ingrained in technology today that will still see it presented that way. 01:02.990 --> 01:09.440 And we don't want to be at a loss when folks start talking about layers, but I'm getting ahead of myself, 01:09.440 --> 01:09.950 I guess. 01:09.950 --> 01:13.760 Why is the OSCE model such a great thing? 01:14.090 --> 01:21.260 Well, it was originally created for stuff to have a chance to be able to communicate together. 01:21.560 --> 01:29.300 You see, when networking and all of this amazing technology with compute really started taking fire 01:29.300 --> 01:33.110 in the sixties and seventies and eighties. 01:33.290 --> 01:41.570 One of the challenges in those decades was that you would have equipment from one manufacturer like 01:41.570 --> 01:47.750 IBM that couldn't communicate with like NBC or DEC, you know. 01:47.750 --> 01:54.290 So there was all these vendors that had great stuff, but it didn't interoperate. 01:54.680 --> 02:02.000 So obviously we needed interoperability so that we could have the incredible Internet filled with its 02:02.000 --> 02:04.190 diverse systems that we have today. 02:04.880 --> 02:14.990 So the reason the OSSI model was created is one thing that's kind of historical, but how can it help 02:14.990 --> 02:15.620 us today? 02:15.920 --> 02:19.760 Well, one of the ways it's going to help us today is in troubleshooting. 02:20.150 --> 02:21.470 I mean, think about it. 02:21.470 --> 02:30.950 When we break down the network around us into these layers and we recognize there's a problem at layer 02:30.950 --> 02:33.650 three, the network layer. 02:33.830 --> 02:35.750 So we number from the bottom up. 02:35.930 --> 02:41.850 Layer one is the physical layer two is data link, layer three is network and layer four is transport. 02:42.290 --> 02:49.940 When we talk about there being a problem at layer three, we know that this is most likely causing the 02:49.940 --> 02:56.960 issue at layer four, layer five, layer six, layer seven, because those layers depend on the network. 02:56.960 --> 03:05.930 Layer a fun, totally like in-your-face example of this would be if I unplug your laptop and there's 03:05.930 --> 03:10.670 no battery inside it, so I unplug your computer and it loses power. 03:10.880 --> 03:11.120 Yeah. 03:11.420 --> 03:13.370 So you're not going to be able to get email. 03:13.670 --> 03:20.480 The physical layer is dead and therefore so is layer two, layer three, layer four, layer five, layer 03:20.480 --> 03:23.600 six, and the application layer layer seven. 03:24.410 --> 03:28.760 Now, one of the first skills that you're going to need is just memorizing the layers. 03:28.760 --> 03:35.990 And there's two famous ways to do that, if you stay with the bottom up, are also popular in pubs, 03:35.990 --> 03:36.470 by the way. 03:36.470 --> 03:38.000 Bottoms up anyways. 03:38.960 --> 03:48.860 If you stay at the physical and work up it's people are oh no it's please do not throw sausage pizza 03:48.860 --> 03:49.430 away. 03:49.550 --> 03:53.930 And that's the one I always like because I'm Italian and I love sausage pizza. 03:53.930 --> 03:59.660 So please do not throw sausage pizza away if you're a top down person. 03:59.660 --> 04:06.230 It's all people seem to need data processing, but you just obviously would have these memorized. 04:06.500 --> 04:10.490 I don't have to think about these anymore as far as you know. 04:10.490 --> 04:12.830 Please do not throw sausage pizza away. 04:12.830 --> 04:14.510 I don't need to play games like that. 04:14.900 --> 04:21.740 When you've been in this industry for any amount of time, these are just ingrained inside you. 04:22.400 --> 04:24.920 Now, what do they actually mean? 04:24.920 --> 04:28.130 What's actually happening happening here? 04:28.670 --> 04:34.340 Well, what's happening is encapsulation of information. 04:34.460 --> 04:35.960 That's really what's happening. 04:36.560 --> 04:45.320 What what we do is we are wanting to send data from one network device to another network device. 04:45.620 --> 04:51.290 And there's going to be a bunch of encapsulation that takes place. 04:51.710 --> 05:00.350 And what this means is additional information that's going to be added to our data so that the community. 05:00.390 --> 05:02.610 Stations actually works. 05:02.910 --> 05:05.040 Let me walk you through this with some examples. 05:05.490 --> 05:08.430 So here we can see the OCI model. 05:08.460 --> 05:15.960 Often called the OCI stack because of course we're stacking these layers on top of each other and think 05:15.960 --> 05:23.520 about us transmitting information from one workstation to another workstation in an organization. 05:23.970 --> 05:27.540 And what they're communicating with is copper. 05:27.840 --> 05:34.290 Yeah, the physical media is copper that is inside of Ethernet cables. 05:34.560 --> 05:37.590 So the physical layer consists of copper. 05:37.830 --> 05:47.310 And the physical layer kind of encapsulation involves chopping up our data into the appropriate bits 05:47.460 --> 05:50.910 for transmission on to the copper wire. 05:51.630 --> 05:57.810 Then what happens is we are about to send this over an Ethernet network. 05:57.930 --> 06:06.190 So at the next layer of the OCI model, the data link layer, we will encapsulate and we don't do it. 06:06.210 --> 06:07.560 The machine does it for us. 06:07.560 --> 06:16.110 Thank goodness the computer will encapsulate onto our data information about our MAC address because 06:16.110 --> 06:22.560 the MAC address is the identifier of a workstation in an Ethernet network. 06:22.890 --> 06:30.450 So now that the MAC address has been appended to the data, it can be handled by the network layer. 06:30.690 --> 06:38.010 This is going to be responsible for taking what we call a packet and sending it on its way throughout 06:38.010 --> 06:42.690 the entire network, maybe even the Internet, the global Internet. 06:43.170 --> 06:46.410 Once again, addressing is needed here. 06:46.650 --> 06:51.540 So we had a layer two data link, layer example of a mac address. 06:51.750 --> 06:59.550 And at the network layer, with the TCP IP protocol, we have an IP address that meet that would be 06:59.550 --> 07:04.440 appended or encapsulated is the best way to say it to our data. 07:05.010 --> 07:11.790 At the transport layer, we have options for how this data will be transported through the network. 07:12.030 --> 07:20.340 For example, if we use transmission control protocol, we'll be transporting the data reliably. 07:20.640 --> 07:26.130 If we use user datagram protocol will be transporting it unreliable. 07:26.790 --> 07:34.800 I'll do videos on this for you to make sure you understand TCP and UDP fully, but for right now we 07:34.800 --> 07:42.090 note that the TCP or UDP information would be encapsulated on our data. 07:42.360 --> 07:49.770 So the data is picking up little ingredients, picking up additional addressing parameters, picking 07:49.770 --> 07:56.070 up additional pieces of information so that we can successfully send it through the network. 07:56.610 --> 08:04.590 The next layer is the session layer, and an example would be the when protocol of X25 or the secure 08:04.590 --> 08:09.600 copy protocol for securely transferring files through a network. 08:09.900 --> 08:18.630 The session layer does just what it sounds like it is, making sure that sessions often secure sessions 08:18.630 --> 08:19.680 can be established. 08:20.250 --> 08:27.270 The presentation layer is doing just what it sounds like, ensuring that things are formatted in an 08:27.270 --> 08:31.320 understandable way by the next layer up the application layer. 08:31.710 --> 08:38.820 So we might have ASCII for text or mime for email messaging, and then there's the application layer 08:39.000 --> 08:46.380 and it's going to be speaking the application layer protocols like the language of love for the Internet. 08:46.650 --> 08:54.000 The World Wide Web is, of course, powered by the hypertext transfer protocol or HTP, just like the 08:54.000 --> 08:58.650 world of email is handled by the simple mail transfer protocol. 08:58.860 --> 09:02.220 We're file transfers by the file transfer protocol. 09:02.700 --> 09:09.180 So notice there is additional information appended to our data for the application layer to consume. 09:09.630 --> 09:16.740 Each layer encapsulates additional information that's going to be required in our environment for proper 09:16.740 --> 09:17.730 communications. 09:17.970 --> 09:24.360 It's really a glorious invention, and it wasn't all that unique. 09:25.140 --> 09:31.440 As a matter of fact, we're going to see in the next video how the Department of Defense here in the 09:31.440 --> 09:37.740 United States had actually created a model that gave rise to this OSA model. 09:37.740 --> 09:45.810 Years later, we'll take a look at the amazing TCP IP architecture model that the DOD came up with and 09:45.810 --> 09:49.440 that really helped fuel the push towards the OSA model. 09:50.010 --> 09:57.150 Now, before I wrap up this video, we also need to realize, and you heard me mentioning these, that 09:57.150 --> 09:59.640 we give specific names to the. 09:59.720 --> 10:09.320 Bottom four layers of the encapsulated data with its you know whatever was encapsulated do it right 10:09.320 --> 10:17.780 so at the physical layer we save the data in any encapsulation information are just bits at the data 10:17.780 --> 10:18.680 link layer. 10:18.740 --> 10:26.390 When we encapsulate, let's say, the Mac address information, we call this a frame at the network 10:26.390 --> 10:32.960 layer, we call the data and the encapsulated information a packet and at the transport layer, layer 10:32.960 --> 10:35.180 four, we call it a segment. 10:35.720 --> 10:42.020 Now, I've never heard a, you know, mnemonic device that will help you memorize these. 10:42.020 --> 10:48.710 So I invented one and I invented it decades ago, and I wrote it in a couple of my books and it actually 10:48.710 --> 10:49.400 caught fire. 10:49.700 --> 10:53.690 So I think if you hear this from someone else, they got it from me. 10:53.960 --> 11:00.440 And it's some people fear birthdays and notice I use the top down approach for segment packet frame 11:00.440 --> 11:01.040 in bits. 11:01.370 --> 11:09.950 Some people fear birthdays, so that's an easy way to remember those protocol data units and you will 11:09.950 --> 11:15.230 really want to practice with that and practise thinking in those terms. 11:15.230 --> 11:22.820 Because when you are talking to networking, cyber security analysts and specialists that are your peers, 11:23.090 --> 11:27.980 they're going to be talking in terms of, hey, what did you find in the packet? 11:28.190 --> 11:33.980 And they want you to know that they're talking about the IP network layer information or they'll say, 11:33.980 --> 11:38.840 What did you find out for the source address in the frame and you need to write away, go. 11:38.840 --> 11:39.140 Okay. 11:39.140 --> 11:42.200 They're talking about a mac address at the data link layer. 11:42.440 --> 11:45.200 So this terminology is super important. 11:45.620 --> 11:52.580 By the way, do we call the information of the session presentation and application layer something 11:52.580 --> 11:53.120 special? 11:53.120 --> 11:55.280 Now we just tend to call that data. 11:55.700 --> 11:56.090 Okay. 11:56.090 --> 12:01.430 So the PD you for all three of those layered layers would just be considered data. 12:02.120 --> 12:08.720 It's the lower four layers where we have the specialized terms that I want you to memorize those layer 12:08.930 --> 12:10.520 four lower layers. 12:10.760 --> 12:20.180 Those are all so specific in what they do that they get big time scrutiny by a cyber security people 12:20.180 --> 12:30.290 because the stuff of the session presentation and application layers that is much less related to networking 12:30.290 --> 12:36.800 than these lower layers, as you might expect, you know, pure networking and pure communications, 12:37.700 --> 12:41.990 the abstraction increases as you go up is another way to think about it. 12:42.560 --> 12:43.010 All right. 12:43.010 --> 12:44.600 Well, enough about this. 12:44.630 --> 12:49.760 Let's turn our attention to the next video where I just wanted to make sure you were clear on the model 12:49.760 --> 12:51.540 that actually predated. 12:51.590 --> 12:52.010 That's right. 12:52.010 --> 12:53.150 Came before this one. 12:53.360 --> 12:56.240 It's that TCP IP architecture model.