Module one then, looking at the concepts and the different models. I would say it's really important to have a firm understanding of this first module. It's really important. And I'll stress some topics as we move through the module for you to investigate further if you need to, or to come back and revisit if you're not completely comfortable with them. So what we'll do first is, look at what networking is, what are we talking about with networking? We'll look at the accepted network models. We will then move forward to look at one of those models, the OSI Model, which is a seven layered model in more depth. And so during this module, we will look at layer one, two, three, four, five, six, and seven. So networking, what are we talking about? Well, this is when we exchange data between two or more systems. And initially when computers were first created, they stored data, and there was a need to move data between one system and another. It was desirable to share. So when we're talking two or more systems, we can talk about a local area network, computers talking within one geographical area, one premises, one physical building, or connecting those networks together into a wide area network. And the internet itself, is a connection of those wide area networks. All those different networks and systems connected together globally. When networks are transmitting data, the data that's transmitted has to be formatted in a way that computers can understand it firstly, but also that it can be transmitted. And the way we transmit data is in a binary number system, a base two number system. It's called the base two number system, because it only has two different numbers. We have zero one and one. Our decimal system has 10 different numbers 0123456789, before we advance onto the next digit 10, 11, 12. And then another 10 before we move on to 20,30 and so on. So binary counting looks really unusual. If you've never seen it before, it would start zero zero. We then move on to zero one, but we can't go any higher than the number one. So the very next number, would be to increment into what would be the equivalent of 10, which is one zero. We would then have one one, and then we have run out of digits, we would need a third binary digit to move any further forward in the binary numbering system. If we're sending, if we're transmitting data using binary has an advantage. What we're trying to send is nothing, or something, zero or the one. And so to transmit, we need something that will support that system of zero and one. So we've got three main methods of transmission. We've got traditional cabling, and this uses electrical impulses. So something like copper, and when a one is being represented on the wire, it will be transmitted as a an electrical impulse. Zero would be represented as no electrical impulse. We then have wireless a radio wave, and again, an electromagnetic impulse of some kind of radio wave would indicator one. The absence of that radio wave would represent a zero. And then fiber connectivity using light, or photons, to send a message here light or photons would represent a one and darkness a zero. So a really simple way of transmitting data. And when we first started transmitting data, the speeds were incredibly slow, and we got faster and faster at sending these zeros and ones. So when we talked about local area networks were connecting limited devices in the same building, or within certainly close geography. Usually, this is to connect server and clients. And this was the dominant method of connecting systems together. In the 1980s we were trying to connect computers together within a geographical location, something like an office building, or a university maybe. Gradually, though what we found was a need to exchange data more widely than this. And here, we're talking about wide area networking, connecting together perhaps different universities, a customer and a supplier. And some of these links in the 1980s, 1990s, were dedicated links. If you were ordering goods from a supplier, you may have a dedicated link to that supplier. Now, what we have is something much more flexible, an existing connection that everybody connects into this internet, this network of networks. So in our homes we connect to a network, which is our local area network that we connect on wards to the Internet through a device called a router, or a router, depending on your preferred pronunciation. We have the idea of a cloud and this is more abstract. The simple way to think of cloud based services is that, they are somebody else's computer. Using cloud services, you're using somebody else's resources, somebody else's server. Instead of being on premise in your location, now it's somewhere else. But we'll look more closely at cloud later in this chapter, because there are standards we can look at and different definitions that we need to be familiar with, before we close the chapter out.