WEBVTT 00:00.770 --> 00:06.170 It takes an amazing amount of software and hardware working together to make a network function. 00:06.170 --> 00:11.210 So the challenge to all of this is that if you have different pieces of software and hardware they don't 00:11.210 --> 00:15.000 have to be able to talk to each other and interact and able to make your network go. 00:15.050 --> 00:20.840 You might have a network card from 3Com and you might be running a Windows 8 operating system and all 00:20.840 --> 00:25.600 of these devices have to work together to help make interconnectivity work. 00:25.670 --> 00:32.120 Then came up with something a long time ago called the OS 7 layer model the OS 7 layer model is seven 00:32.120 --> 00:35.140 distinct functions that a network must do. 00:35.180 --> 00:38.990 Now the LSI is being supplanted with something called the TCAP model. 00:38.990 --> 00:45.950 So let's do a quick overview and take a look at OS I and TZP now for OS I we're going to start basically 00:45.950 --> 00:51.020 there's no real bottom or top but I tend to look at it at the bottom which is your most basic part which 00:51.020 --> 00:54.020 is what we call the physical layer the physical layer is. 00:54.260 --> 00:56.690 That's like the easiest part of the OS 7 layer model. 00:56.690 --> 01:00.460 It's just what type of cables do I use and things like that. 01:00.500 --> 01:02.900 Now coming up from that is the data Linkletter. 01:02.960 --> 01:05.130 Now the data like layers a little bit more important. 01:05.150 --> 01:09.320 Basically anything that works with a MAC address works at the data Linkletter. 01:09.320 --> 01:13.940 So when we're talking about data link we start talking about things like the network cards themselves 01:14.150 --> 01:17.250 start talking about switches things like that. 01:17.330 --> 01:19.380 The third layer is the network layer. 01:19.390 --> 01:24.890 Now the network layer is important because the network layer has to do with logical addresses. 01:24.890 --> 01:28.330 So when you see the network layer you're talking about IP addresses. 01:28.430 --> 01:35.930 So things like routers in particular work at Layer 3 the next layer up is the transport layer the transport 01:35.930 --> 01:37.740 layer is kind of interesting. 01:37.760 --> 01:39.340 Data is big. 01:39.440 --> 01:43.320 And the actual chunks of data that go through a network are relatively small. 01:43.370 --> 01:49.310 So there has to be a assembly disassembly area for data as it gets broken down into individual packets 01:49.310 --> 01:52.650 and that's what the transport layer is all about the transport layer. 01:52.670 --> 01:58.780 Not only disassembles packets but make sure the packets get to the other system in good order. 01:58.870 --> 02:00.620 Next one is the session. 02:00.620 --> 02:04.640 Now the session is kind of interesting when we work at a session layer here we're talking about the 02:04.640 --> 02:06.860 actual connection between two systems. 02:06.920 --> 02:12.440 Are we making a TZP connection between a web server and a web client or are we just sending e-mail. 02:12.440 --> 02:15.470 Are we sharing a folder between two computers on a local network. 02:15.590 --> 02:20.180 And it's the session layer that defines what's taking place in terms of how that connectivity really 02:20.180 --> 02:21.810 works. 02:21.830 --> 02:27.980 Next is the presentation layer the presentation layer is old and weird but since it is on the OS I would 02:27.980 --> 02:33.110 need to at least make a quick mention of it just because a big chunk o data comes into your computer 02:33.320 --> 02:38.200 does that necessarily mean that this data is in a form that your computer can read it. 02:38.200 --> 02:41.830 Now let's use Microsoft Office as an example. 02:41.840 --> 02:47.920 If I open up my Microsoft Office I can open up almost any kind of document you can dream of. 02:48.020 --> 02:50.920 Office has the smarts built into it to automatically read it. 02:51.080 --> 02:52.760 But that wasn't always the case. 02:52.820 --> 02:58.880 So the presentation layer used to be used to convert data into a format that your applications can read 02:59.990 --> 03:05.540 or at the top is applications applications is important because it's the applications themselves and 03:05.540 --> 03:08.000 it's not really the applications you have to be careful here. 03:08.000 --> 03:13.940 What we're talking about is the smarts in the applications that make the network aware little simple 03:13.940 --> 03:15.170 things that you and I never think of. 03:15.170 --> 03:21.830 For example if we were to open up Microsoft Word and we could literally go to the network to go find 03:21.830 --> 03:23.240 a particular file. 03:23.240 --> 03:26.730 And that's because Microsoft Office itself is network aware. 03:26.750 --> 03:33.440 We often use the term API or application programmers interface as the definition of the smarts that 03:33.440 --> 03:39.160 are built into an application that allows us to make the application network aware. 03:39.410 --> 03:41.440 So this is the most high. 03:41.580 --> 03:42.110 All right. 03:42.230 --> 03:48.790 The TCAP IP model is more simplistic than the OS simply because if you're using only TCAP IP there's 03:48.800 --> 03:50.810 a lot of parts don't really come into play as much. 03:50.810 --> 03:52.330 Let me show you what I'm talking about. 03:52.370 --> 03:56.930 First of all we have what they call the network interface layer so the network interface layer covers 03:57.110 --> 04:03.650 all the physical cabling MAC addresses network cards pretty much everything in terms of hardware with 04:03.650 --> 04:09.350 a couple of small exceptions routers are all covered here under network interface so that ties similarly 04:09.350 --> 04:12.460 to the data link and physical for the OS side. 04:12.470 --> 04:14.480 Now your next one is your internet link. 04:14.510 --> 04:17.220 Your indirect leads for IP addresses. 04:17.420 --> 04:22.660 So things like routers or anything it has to do with an IP address works at the Internet layer. 04:22.790 --> 04:24.580 The next one is transport. 04:24.590 --> 04:30.860 Now transport does all the assembly and disassembly but it also has to do with whatever it takes to 04:30.860 --> 04:33.780 connect to the other system to make sure the data gets there. 04:33.890 --> 04:40.640 So in this case we're talking about things like for example TZP or UDP whatever it takes to get those 04:40.850 --> 04:44.350 chunks of data from one application to the next. 04:44.360 --> 04:46.730 Now the last one is called application. 04:46.730 --> 04:54.020 So application actually takes into consideration the old OS application presentation and session layer. 04:54.050 --> 04:58.060 So everything that has to do with the application itself works at this layer. 04:58.070 --> 05:04.430 Keep in mind that the IP model looks at this a little bit differently the no S-I TCAP model looks at 05:04.430 --> 05:11.050 applications as applications for example email or FGP or telnet. 05:11.060 --> 05:16.970 All of these very distinct things that each have their unique port numbers all play into this one particular 05:16.970 --> 05:17.690 area. 05:17.930 --> 05:23.420 So if it were up to me and it's not but to me I would change just a little bit. 05:23.420 --> 05:29.690 First of all I would go ahead and take the transport layer and put the old OS I.S. layer into that as 05:29.690 --> 05:31.070 well as the transport layer. 05:31.070 --> 05:34.910 But that's really not the way we look at it for the example we put that back. 05:35.120 --> 05:38.380 And that's pretty much your TZP IP model. 05:38.390 --> 05:41.360 Now what I want to do is let's take a look at both of these guys. 05:41.360 --> 05:47.810 First we have the OS I model older more detailed and then we have the TCAP IP model more modern. 05:47.840 --> 05:51.140 Not as much detail but not as complicated. 05:51.170 --> 05:55.340 Make sure for the network plus exam that you know both of these models that don't worry about it we've 05:55.340 --> 05:56.450 got a lot more to talk about. 05:56.450 --> 06:00.710 We've got lots of episodes that are going to break down all the different layers in these models and 06:00.710 --> 06:01.950 a lot more detail. 06:02.000 --> 06:06.800 But for right now the important thing you need to appreciate is that each one of these layers has a 06:06.800 --> 06:08.050 distinct function. 06:08.090 --> 06:09.660 Each one of these layers has a name. 06:09.680 --> 06:11.810 But not only that it's also got a number. 06:11.870 --> 06:13.950 So let's use as an example. 06:14.000 --> 06:19.090 If I'm talking about OS I am looking at the network layer now understand its network layer but there's 06:19.100 --> 06:22.820 also numbers associated with it and they go from one up to seven. 06:22.820 --> 06:28.420 So if I'm talking about OS I and I say Layer 3 you need to know that I'm talking about the network level. 06:28.490 --> 06:30.590 That's also very true with TCAP IP.