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There are three basic types of Ethernet with which we should be familiar today. There have been other types, there has been coaxial cable used in the past, but it's not likely to be tested these days. Coaxial cable is, for all intents and purposes, being phased out. As a matter of fact, the first of the ones that we need to be familiar with, is, for all intents and purposes, being phased out as well. And that would be ten megabit per second connections. 10 BaseT, as it's also called, we will talk about that later on. But 10 megabits per second was by far the most common type of Ethernet, just plain old category-5 or category-4 cables connecting computers together. And 10 megabits per second is now being phased out for 100 megabits per second networks. Most network interface cards that we buy these days can use either 10 or 100 megabits per second, they're called 10-100 cards. And therefore all we need are the rest of the components on the network to be able to handle 100 megabits per second, and then we've got a network that can handle it. So, 100 megabits per second networks are quickly replacing older 10 megabit per second networks, because all it takes is a hub that can handle the transmission as well as the wiring. And all it takes is category-5 twisted pair cable, to handle 100 megabits per second. If we really want to fly, we can use 1000 megabits per second networks, and typically they are not called 1000 seconds megabits per second networks, they are called gigabit Ethernet. But it's 1000 megabits per second, 1000 BaseT, this is the newest technology. Expands the bandwidth and allows for voice data and video transmissions; all on the same wire. So this is the coming technology, this is where it's going, but the technology is still to come. In other words, most networks these days are probably 100 megabits per second, some are still 10 megabits per second. But 10 megabits per second is pretty well being phased out, 100 megabits per second is common. 1000 megabits per second is becoming more and more common especially in larger organizations. So what is all this base and T information mean; well, let's take a look at this. Base stands for Base Band transmission. Base band transmission means the wire is considered full when one signal is carried. So, Base band transmission means that I would have to have some type of a protocol like CSMA/CD sensing the wire, to determine whether anything is on the wire or not. That's what that's all about. Base band is opposed to broadband; with broadband we can have many signals on the same wire. We can do that by multiplexing; there's lot of different ways that we can use broadband. But, Base band is what we are using for local area network communications. 100 BaseT means 100 megabits per second Base band transmission. And what's the T stand for. Well, the T stands for twisted pair wires. The reason that the wires are twisted is to prevent cross talk. Now, cross talk doesn't have anything to do with one cable talking to another. What it has to do with is; the pairs of wires talking to each other, the ones that are in the same cable. So we twist them together or the company who makes the wire twists them together, so that the pairs of wires that are connected or that are sitting right next to each other, don't bleed into each other, the signal doesn't bleed in. And the tighter that we twist those wires, then the more information we can pump through them, and the faster we can pump information through them and not get cross talk. So the T stands for Twisted Pair Cable. So 100 BaseT stands for 100 megabits per second. Base band transmission which means that we are going to have to use something like Carrier sense multiple access with collision detection, and that's what Ethernet uses. Because the wire's going to be considered full if there's any signal on it whatsoever. And a distance limit also applies. And the distance limit with any thing that ends in a T, anything that's twisted pair, has a distance limit of 100 meters. And they say 100 meters without repeaters; well a repeater could be a hub. A hub is a multi-port repeater. So, we can go a little less than a 100 meters and then hit a hub and then go a little less than 100 meters again. And that's done in local area networks. But we can't go more than 100 meters without hitting some type of an amplifier - a hub, or just the device called a repeater, which just amplifies signal. And we can't go any further than 100 meters and expect to have any kind of reliable signal. In other words we might be able to physically stretch it further than the 100 meters. But the recommendation is to stay under 100 meters unless we're going to use repeaters. And that's what that whole rule stands for in regards to twisted pair wires. So anything that ends in a T, the 100 meters without repeaters rule applies. So, it's important to understand the local area network design, in order to be able to build the type of network that we need to have. In regards to the Cisco devices, it's important to understand the specifics of how they operate. So, in our next chapter, we are going to switch gears and talk about the Cisco IOS; that's next. work that we need to have. In regards to the Cisco devices, it's important to understand the specifics of how they operate. So, in our next chapter, we are going to switch gears and talk about the Cisco IOS; that's next.