Hello and welcome to the networks and communication security conversation. In this area we're going to be dealing with the following objectives, you can see them on the screen in front of you. Describing network-related security issues, identify protective measures for telecommunications technologies, defining processes for controlling network access, identifying processes for managing LAN-based security. Describing procedures for operating configuring network based security devices, and defining procedures to implement and operate wireless technologies. Let's go ahead and jump into understanding security issues related to networks, our first conversational topic, our first area we we'll spend some time in. In this area, the module topics will include, OSI and the TCP IP Models. Internet protocol networking, so, IP based networking, network topographies and relationships, commonly used ports and protocols, always a favorite topic, and HTTP proxying. Let's begin with OSI and TCP IP models. When we start to think about networks, we start to think about how data is able to be communicated, managed, and maintained. Inside one system, between that system on the wire and another system and I would transmit data. We have to think about these two models, both of them are historically relevant. Both of them are going to represent a moment in time where we were transmitting, managing and manipulating data using a certain thought process. The OSI reference model is the one that we currently use. The TCP IP or what's known as DoD model is an older model that the OSI model comes out of. The OSI model's based on the DoD model, in another words, broadens, widens and add some depth, and specific demarcations deliniations, for certain functions to the DoD model. DoD models a little bit higher level, little bit older, kind of took place and was from a point in time where networking was simpler. As it became for complicated, the OSI model becomes the standard that we use. So let's drill it, let's see what the standard layers of the OSI model look like. We'll take a look at the DoD TCP IP base model a little bit later on. We'll just see what that looks like compared to the OSI model. You'll see there we have four layers in the TCP DoD model, compared to the seven layers that are going to be laid out here in the OSI model. We tend to look at the OSI model in one direction, meaning when we learn it we want to understand the model layers. We either go top down or bottom up, it does not matter which way we go, we can see the model operating bidirectionally, either up or down. Depending on whether it is processing information from the user that is inputting system data at the application layer, at an endpoint like a desktop computer. And then sending it out across the wire or on the receiving machine that's being sent that data, we're receiving it at the physical layer on the wire and moving it up into the application layer to be able to interact with it. Doesn't really matter to us, but all I'm suggesting to you is that you're going to have to learn the layers of the OSI model in order, understand what they are, how they operate, what goes on at each layer. So you're going to want to learn them in some order that's going to help you to better understand them. And to that end you're going to want to come up with what's known as a mnemonic, a memory device that aids you in understanding the different layers. Whether you go from the top down or you go from the bottom up will be up to you. But come up with some sort of mechanism that allows you to be able to learn them. When I learned it many, many moons ago, I learned it from the bottom to the top, using the first letter of each layer and its representative name to understand and represent what was going on. So my mnemonic was PDNTSPA I am a child of the 80s who wouldn't know that by looking at me of course. But because I'm so young and youthful as you can see, but given that by acronym PDNTSPA went as follows. P for people, people don't need to see Paula Abdul, little bit cruel perhaps I know, but being a child of the 80s that worked out for me. So people don't need to see Paula Abdul, from the bottom to the top, physical, data link, network, transport, session, presentation, and application layer. You come up with your own mnemonic, you search the Internet, there are many, many of them out there. You can come up with all sorts of great ones, make up your own, doesn't really matter. We're going to talk about what happens in each layer, make sure we understand what goes on. About the time we're done you'll be able to understand and obviously then also reproduce in order the layers as well. But you are going to need to know them, just to be clear, if you don't already know them, make sure you focus on them. So, let's dive in, you can see a high level of them here, we're going to go through each layer, kind of break them down step by step on some slides. But let's just quickly talk about them in a high level, and then we'll go ahead and we'll look at the detail. I'm going to start at the application layer at the top of the model, just because it's easier to deconstruct than it is to construct when we're first learning about the model. So, just going to draw ourselves a little arrow here so that way as we're going, going to remind ourselves that we are going down the model. That way we can keep track of where we are and what we're doing so, we are going to go, Down the model here. And we'll put a check mark next to each layer as we go ahead and we work with it that way you know that we've covered that particular layer. So I'll just get my little eraser out here and go ahead and do that and so we're ready for it. And then we'll go ahead and we will change our color. And we will go ahead and we will get ready to be able to put in the appropriate mark as necessary when we are ready. Let's start the application layer, seventh layer, the top layer number seven in the OSI model. Also put a little number here next to that layer, it's a little big, but that's going to be layer 7, or that's going to be number 7, so that way, we know what that is. want to make sure we understand the number, as well as the actual function. So that's going to be important, we'll just put a slightly smaller number there, that's going to be number seven. Seventh layer of the OSI model, it's the application layer, as you could see at the top layer network layer application programs. The idea here is you're sitting at your computer, you're opening up Internet Explorer or Chrome, or you're opening up Edge, or you're opening up Firefox, or you're opening up Safari, take your pick of whatever web browser you would like. Your on the web, you're interacting, your typing in something, you're going to go to Google, and you're going to search for the DoD model, the TCP IP model look it up. So you're using a web browser, and you're sitting at your keyboard, and you're going to put some information in there, Http www.google.com. You type that in, you hit Enter, search engine goes out, finds Google, we're going to talk later on about how all that happens with DNS resolution, but for now let's assume you know how it works and we find it. Google comes back, shows up on your web browser, and you can now type in in Google, I want to know about the TCP IP DoD model, Enter. Google goes out, searches the corners of the World Wide Web and Internet, brings back a wealth of useful information, shows up on your screen. All of that is happening because of the OSI model. So let's break down what's going on there and talk about the individual levels and how those levels are then going to help us to understand what's happening.
