From the course: CompTIA Network+ (N10-009) Cert Prep

100BASE-T

From the course: CompTIA Network+ (N10-009) Cert Prep

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100BASE-T

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- It wasn't that long after 10BASE-T was introduced that people were demanding higher speeds from the networks, and the ethernet people responded with 100 megabit ethernet. Now, people often ask me, they go, "Mike, why do we go from 10 megabit to 100 megabit to gigabit to 10 gigabit? Why is it always times 10?" And the answer is simply this: It is what they can do. It is the amount of speed that is worth it in terms of reinvesting in cabling and network cards and switches and whatever you might have by being 10 times faster. So there are variations. There were things like 20 megabit ethernet, but nobody wanted it, nobody bought it. It wasn't until we went to 100 that people got interested. So it's always times 10, with a few exceptions in there. So in this episode, I want to talk about 100 megabit ethernet. Now, 100 megabit ethernet, as it came out, this really was the big transition. First of all, when 100 megabit ethernet came out, we were still using hubs, and it was really as 100 megabit ethernet came out that certain standards said you can't use hubs anymore. So that was always a big challenge, is that even today, if you're in a situation where you might want to use a hub, you have to actually use 10 megabit everything, 10 megabit cards, the whole shebang, just to get it to work. So hubs really are obsolete. The other thing that took place around this time is we began to see the concept of moving from half-duplex to full-duplex. It's easier to understand half-duplex if you think about the days with CB radio. So you got a CB radio in your car, you can sit there and you can talk all you want there on a rubber duck in the walking chair and all that, and you can do all the talking you want, but you're not going to be able to hear anybody until you stop talking. So that's a perfect example of half-duplex. Now, full-duplex is if you're on the phone and you're talking to a friend of yours and you all start both trying to talk, "No, no, you go." "No, okay, look, I won't say anything, you go ahead," because you can both talk at the same time and it creates a lot of confusion. So full-duplex is when you can both listen and talk at the same time. So it was around the time of 100 megabit ethernet that we began to see full-duplex. Today, starting with 100, moving up to all the gigabit and 10 gig and all that, everybody's full-duplex today. So there were really a number of standards that came out with 10BASE-T. And I want to go ahead and just go through all these just very, very quickly. One of the oldest versions was known as 100BaseT4. Ran at 100 megabits per second. It had 1,024 nodes per hub, it actually used hubs. And from the hub to any node was 100 meters, and it used Cat 3 cabling. What's interesting about 100Base4 is that it was one of the first ethernets to use all four pairs inside of a unshielded twisted pair cable. Second was 100BaseTX. 100BaseTX ran at 100 megabits per second, 1,024 nodes per hub, 100 meters from the hubs to the individual nodes, and it used CAT 5e cable, and it only used two pairs. And yes, 100BaseTX was full-duplex. Now, here's the interesting part. We literally had two competing standards. They both used unshielded twisted pair. They both had hubs and switches, they had network cards, but you couldn't tell 'em apart simply by looking at 'em. You'd have to look at a switch and it would say 100BaseTX or 100BaseT4. The bottom line is that 100BaseT4 disappeared, it's gone. And 100BaseTX is now known as just simply 100BaseT. So if you find yourself a switch and it says 100BaseT on it, it's really 100BaseTX. but everybody just calls it 100BaseT. The other interesting part about 100 megabit ethernet was that we began to see fiber solutions, in particular, something called 100BaseFX. So it would run at 100 megabits per second, again, 1,024 nodes per hub, but you could run a piece of multi-mode fiber. You know, you'd have to have a fiber optic switch and you could run two kilometers. So there were a lot of places where suddenly fiber optic, especially for long distance throws, became extremely attractive as an option. So for the exam, the big thing I want you to keep in mind more than anything else is that make sure you're comfortable with the concept of hubs versus switches. And during the time, 100 megabit is where we really began to see that switch. Also, keep in mind, be comfortable with duplex versus half-duplex. In other episodes, that's going to become very handy. And make sure you're comfortable with the three versions of 100Base ethernet just described, why not? 'Cause it's going to be on the exam.

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