Welcome back to the first lesson of module three in the foundations of computing, and the visual basic specialization course. Remember in this first course we're trying to understand enough material, to give us a sense of the environment within which our applications we develop will run. And in this first lesson, we're trying to get an overview of networking, okay? So we last talked about different transmission speeds. We now want to think a little bit about wireless networking. All right, so wireless networking is going to allow our communication to happen without cables. This allows you to not be tethered to one physical location, right? So I am sure you have all experienced this, right? You have a mobile phone, probably or Notebook or a netbook or tablet, and you can move around your home or maybe your office with your phone. Geographically you can move around anywhere in the country or maybe even overseas, right? That idea was very foreign a few decades back. We used to be tethered in one location, and if you only had a desktop computer you have one place you can work. There's lots of different ways to do wireless networking though. So we think primarily about our Wi Fi but there's all kinds of different wireless networking protocols. So radio wave, microwave, infrared signals, and our traditional mobile computers. And the benefit here is we can deliver data regardless of the location of your device. And just to give you an example, I had a customer, I used to have a software company that we built software that did ticketing for the entertainment industry. And I had a customer In the city of Panama, and they had an electronics store where they sold tickets to all the events, and they had microwave antennas on the roofs of their electronics stores around the geographic area of Panama City. Bluetooth you've probably used in your personal area network with maybe your headset, but we use it with wireless mices, cameras, video games, all sorts of things. Bluetooth has a range of between 30 and 50 feet. All right, next we want to think about a local area network using wireless. Essentially computers are going to transmit wirelessly to a base station. This is either a hub or router and that base station will have a wired connection. So this is probably what you have in your home, right? You probably have some sort of either cable modem or DSL or fiber optic cable coming into your home, that's wired to a router or an access point that you then use wirelessly around your home. This has a range between 150 and 300 feet, depending on the amount of walls and metal in your walls. So a little bit of terminology when we're thinking about wireless. Wi-Fi stands for wireless network communication. IEEE 802.11 is the standard for all the wireless protocols. And a Wi-Fi hotspot is a wireless or Wi-Fi that's available in some sort of public location. So a library, your campus, a coffee shop, that sort of thing. And a metropolitan area network or what we abbreviate is a MAN. Is a built-out wireless network that covers blocks or cities, right? The goal is that we'd have MANs in every city, right? And so you would rely less on your personal network and more on that metropolitan network as you moved around. This has not really come to fruition in the United States yet. There are a few cities with decent MANs but most cities are way behind here. All right, next we want to think about a wide area network wirelessly. So computers are going to transmit wirelessly to a remote base station which has a wired connection. Some sort of cellular technology is going to involve antennas on towers miles apart. So example 4G or 5G where we have voice and data. With 4G our transmission rates are at between 50 and 500 megabits per second. Unfortunately, the signal can be blocked indoors. Specifically, if you are in lower floors, in the basement, or subbasement floors. Any errors with data transmission can slower performance. And there is all kind of security concerns here. So our wireless signals are easy to intercept, and you've heard a lot of this stories in the news. And later on in this course we'll talk a little bit more about information security, and think about some of this security concerns. A local area network is typically used at a wired connection. So we're going to hook up our computers, our printers and servers and some close proximity. So an example is the same room, the same office building, or campus. This is typically privately owned and operated, so separate from like a coffee shop, right? That in your office you're wiring up the computers, because you have a better connection speed. But you maintain the equipment. There's several different topologies which are how the computers are connected, and we're going to talk about that a little bit later and it really affects how they communicate. And these local area networks can be made up of different types of systems and operating system install. So Macintoshes, Linux, Windows or Android, all on the same network. So we talked about topologies, there's three majors. A bus topology, which is this top image here, where essentially the computers are just nodes hung off a bus and at the ends of the bus we have terminators. And everyone who wants to communicate basically is broadcasting along the bus. The problem with a bus is only one person can talk at a time. So we have shared lines and you basically take turns. And the algorithm for taking turns is you try to talk and if someone else is talking, you wait a random amount of time before you try again. This works fine with a few machines, but as the more machines you get on that bus, the more crowded the signal, the more time everyone's waiting to communicate. So the next topology, is a ring topology, and a ring topology basically the message is going to circulate. And as a message comes to you, we call it a token, you can add a message and you can receive messages, so it's like a little bus that's going around the ring. And you can hop on with a message or pull messages off. So there's no collisions in a ring topology. And lastly is a star topology. And we see this a lot these days. So messages are sent to a central node, which routes messages to the destination. So either a switch or a hub or router in the middle here and we run cables off them in a star, all right? So just a little bit of review of that first lesson. A local area network spans a single geographic location or area. A wide area network's going to span multiple geographic areas. So maybe you've got a New York City Office and a California office, but they're networked together in a wide area network. And there are three main network topologies. These are the bus, the star, and the ring. All right, you've made it through lesson one. I'll see you in lesson two.
