Minggu, 05 Februari 2017

UTP and STP cabling

We strongly recommend you to read the article first to increase knowledge about the Fiber Optic, Gigabit Ethernet, The Physical Network before proceeding to the next page.

- The number one type of cabling that we use in networks today is called unshielded twisted pair. Now a lot of times you hear the term Ethernet, and we'll cover Ethernet in other episodes. But ethernet is simply a way to make a network go. And unshielded twisted pair is only one way to make Ethernet go. So I wanna get something down right now. I'm gonna be showing you unshielded twisted pair, it is used on Ethernet networks but it can be used on all kinds of other stuff too. So let's just talk about the cabling itself, good old unshielded twisted pair, better know as UTP.

Now it all starts off right here. If you take a look inside this cable you can see in this particular case I've got four pairs. Now there's a little string here, see if I can get that. This string is actually kevlar, same stuff they make bullet proof vests out of, and it's used so you can pull 500 feet of this through a piece of pipe and not snap it in half. So the work is actually done through four pairs, now unshielded twisted pair doesn't mean four pairs. There's a lot of places where unshielded twisted pair might only have two pairs, for example, in telephones.

But in the networking world it almost always uses four pairs. So this is four pair UTP. Okay now that is the basics of the cabling itself. But the thing you need to remember about unshielded twisted pair is that networks keep getting faster and faster. Pretty much they always increase by a factor of 10. The first generation networks ran at 10 megabits per second The next generation ran at 100 megabits per second. The one after that was times 10, 1,000 megabits per second, or gigabit. And today the newest networks are currently running at 10 gigabits per second.

So they always multiply by a power of 10. Now you have to have cabling that can handle these types of transmission speeds. So they break all the different types of unshielded twisted pair down into these groupings known as CAT levels. So it all started back a million years ago with something called CAT 1 which was just used for voice telephone lines. And CAT 1, CAT 2, CAT 3, CAT 4, CAT 5, CAT 5e, and CAT 6a. Why don't we run over the ones that are actually on the exam Number one, there's gonna be CAT 3.

CAT 3 is very similar to the piece that I have right here in my hand. The only way you can tell a CAT level is, I'm gonna see if we can actually get this on camera. You can read the cable itself. So in this case you can actually see printed on here, it says, "CAT 5e". So this particular piece of cable is CAT 5e. It's hard to tell the difference between different CAT levels by simply looking at the cable. So let me just tell you what the differences are. Number one CAT 3.

CAT 3 was designed to run at a very interesting speed of about 16 megahertz. Now when we're talking about the signals that a piece of wire can handle we talk in terms of cycles per second, we say "hertz". However there's fairly close to a one to one correlation of bits per second to hertz so we'll just go ahead and use that. So CAT 3 was designed to run up to 16 megahertz and bring it down a little bit. That's what we used on the old 10 megabit networks. So that's the oldest one you're gonna see on the exam.

The next one is CAT 5. CAT 5 was designed to run at 100 megabits per second however there were problems with it and that's where that CAT 5e came from. You see when they designed CAT 5 they didn't make the rules quite tight enough so they improved the rules a little bit and came up with CAT 5e. So both of those cables are designed to run 100 megabits. The next one is CAT 6. I've actually got a piece of CAT 6 right here, I wanna show this to ya. So if you take a look at this, this is CAT 6. First of all the one thing you'll definitely notice is that the cables are a lot heaver than we saw with the CAT 5e.

And you'll also notice that they're more twisted. That's one of the things that makes one CAT level different from another is the number of twists per inch. So the more twists per inch, you tend to be able to handle a faster signal. The other thing that makes CAT 6 very distinct is that CAT 6 is going to have some kind of piece of tape or something in here that actually separates the different pairs to keep them from interfering with each other. So that's CAT 6. CAT 6a is kinda the same situation we had with CAT5 and CAT 5e.

They added a few more improvements to it but the big thing with CAT 6 and CAT 6a is that they can run 10 gigabit per second networks. And those are the questions you're gonna be seeing on the network plus. "What is the fastest network that CAT 3 can run? "10 megabits per second. "What's the fastest network that CAT 6a can run? "10 gigabits per second." So make sure you know those. So we have these different CAT levels, let's talk about some of the connectors. There are two connectors that you will see on these types of unshielded twisted pair cables.

Now here on your left, on my right, is an old school RJ11 connector. RJ11 is not gonna be used on networks it's gonna be used on telephone systems. And it's a modular plug and it is used for telephones. Over here is a very famous connector known as the RJ45. The RJ45 connector is also known as the, you ready, 8P8C but nobody uses that except for me so we'll just keep calling it RJ45 and that's what it's gonna be on the test too.

And the RJ45 has eight connectors designed to handle four pairs of cablings, so you'd be able to recognize the difference between an RJ45 and an RJ11. Now there's one other type of twisted pair I wanna show you. It's kinda rare and interesting. It's called shielded twisted pair. I got a piece right here. Now if you take a look at this cable you'll see that it's still twisted pair, nothing special there, it even says CAT 6 on here, but what you do notice is that there's foil.

This foil acts as a shield, in fact this shielding even goes onto the RJ45 connector itself. You see that metal shield? These are gonna be used in networks where you got a lot a noise. Lots of big electric motors and things like that that can cause interference and cause trouble for unshielded twisted pair. But otherwise pretty much unshielded twisted pair is the way to go. Now the last thing I wanna talk about in terms of cabling is fire ratings.

So if you take a look at this box, unshielded twisted pairing invariably comes in these big boxes of 1,000 feet spools. And if you take a look at it somewhere on the box there's going to be some documentation that tells you what the fire rating is. There are three fire ratings that you'll run into with twisted pair. The most basic one, which is barely no fire rating at all, is called PVC. PVC is cheap plastic and it will catch on fire and make noxious fumes and smoke. And a lot of times it's cheap but not the kind of stuff you wanna be putting into offices and things like that.

The next step up from PVC is Riser. Riser is designed primarily to run between floors of buildings. That's where its name came from, Riser. It has a good amount of protection but it's not designed to take tons of heat over a long amount of time. The big one and the one we tend to use more than anything else is called plenum rating, P-L-E-N-U-M. Plenum rating is the big super, fire retardant type cabling. And it's really designed to really resist all of these different types of fire issues.

No smoke, no noxious fumes, or anything like that. It's important to understand these fire ratings for one very simple reason. If you're gonna be putting cable into a ceiling or into a floor you're gonna have to be dealing with inspectors and things like that. Cities have codes that define exactly what type of fire rating you need to be able to deal with. So make sure you know 'em. So with UTP the big thing to remember more than anything else is your CAT levels, your connectors, and your fire ratings.
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