WEBVTT

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 So I want to finish up this
 series on Ethernet.

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 It's talking a little bit about Ethernet
 cabling and sort of demystifying

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 some of these terms like what's the
 difference between category 5 and

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 category 6 cables and what does it mean
 when I see 10 base T versus 100

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 base T4? What does all that mean?

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 So that's what we're going to do
 in this wrap up session here.

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 So as I mentioned previously, when
 Ethernet first came out in the late

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 1970s, it used a very
 thick coaxial cabling.

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 They actually called
 that thick net.

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 And they came up with, after that, a
 thinner type of coaxial cable that

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 was a little bit more flexible
 called thin net.

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 But we don't use that anymore
 as Ethernet evolved.

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 It continued to operate over copper
 cable of various different types as

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 well as fiber optic cable because by
 transmitting those ones and zeroes

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 as light pulses instead of electrical
 energy, you can actually transmit

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 it faster and get more data through that
 cable if it's a fiber optic cable.

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 So a lot of times you're going to see
 when referencing Ethernet, especially

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 like Ethernet cables, you're going to
 see stuff like 100 base Tx or 1000

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 base Zx or something like that.

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 What does that mean?

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 So let's break that
 down a little bit.

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 So first of all, when you see something
 like that, the first number represents

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 the speed. So 10 is 10 megabits per second,
 100, 100 megabits per second.

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 And in terms of Ethernet, the next thing
 is always going to be the word

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 base, 100 base, 1000 base because Ethernet
 is what's called a baseband

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 technology, which means that the transmitting
 device, the device that's

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 sending has full use of all
 the bandwidth of the cable.

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 You can't divide up and have two or
 three devices transmitting at the

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 same time and using different
 frequencies or something.

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 Ethernet doesn't support that.

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 So baseband means one device is speaking,
 it's using all of the electrical

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 energy on that cable.

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 It has the cable reserved.

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 And then the last section could either
 be a digit or a number or a value.

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 So for example, if it's a digit, that
 represents the maximum cable length

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 in meters. So for example, some of
 the older Ethernet was like 10 base

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 2. 10 base 2 was 10 megabit per second
 Ethernet, baseband, that could

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 operate over a cable that was
 roughly 200 meters in length.

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 Actually it was supportive
 of about 185 meters.

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 There was also 10 base 5, which was
 an Ethernet cable that was up to 500

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 meters in length.

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 These days typically you'll
 see like a letter there.

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 For example, T means
 twisted cable.

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 So if you see a letter that's indicating
 the type of cable that you can

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 use. So T or TX would
 be twisted pair cable.

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 And in just a second I'm going
 to show you what that means.

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 T4 and T2, which you won't see anymore,
 was using either copper cabling

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 or also twisted pair but doing the cabling
 a little bit different, a little

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 bit of the signaling different.

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 If you see something that's a letter
 other than the T, for example ZX

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 or LH, a lot of represents fiber
 optic cabling of some sort.

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 Unless you see CX, C stands
 for copper cabling.

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 So most variants of Ethernet these
 days have some sort of letter which

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 doesn't really tell you
 how long the cable is.

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 It gives you more of a reference of
 what kind of cable you're using.

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 In just a second I'll show you a chart
 that shows you those various different

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 types of cables and their maximum distances
 and everything like that.

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 But the most common form of Ethernet
 you're going to see today in most

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 local area networks where you're connecting
 laptops and PCs and servers

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 into the network is what's called
 twisted pair cabling.

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 So why do we call it twisted pair?


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 Well in twisted pair cabling you have
 a pair of copper cables that are

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 forming a complete electrical loop so
 that you can send electrical energy

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 around in this loop much like we do
 in the telephone lines that connect

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 to your telephone.

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 So in this pair of cables, for example in
 this case here we have the transmitter

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 on the left and the receiver on the right,
 one wire and the pair is sending

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 the electrical current in one direction
 and it's looping around and sending

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 the electrical current back
 in the other direction.

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 This creates an entire
 electrical circuit.

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 So in a twisted pair cabling using Ethernet
 the earliest forms of Ethernet

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 specified you have two
 pairs of cables.

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 So that means a total of four
 cables, one pair and one pair.

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 Now why do they call
 it twisted pair?

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 Well if these cables are running right
 next to each other because of the

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 way electrical energy and magnetic and
 everything works along the cable

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 their electrical energy could actually
 influence each other and scientists

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 and physicists figured out a long time
 ago that if you take a pair of

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 cables and you wrap them you twist them
 among each other it helps to mitigate

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 or prevent this electromagnetic
 interference.

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 So you don't have to worry so much about
 your ones and zeros being corrupted

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 in one wire based on the ones and zeros
 being transmitted in the wire

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 right next to it.

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 So that's why we call
 it twisted pair.

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 So up up top here here we show an example
 of what twisted pair cable looks

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 like. Vast majority of twisted pair
 cable and you're going to see today

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 each individual cable is going to have
 an outer sheath of some sort of

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 a color and then every two cables
 are going to be twisted together.

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 And so the colors just help
 you track the cables.

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 And so that's what twisted
 pair cable would look like.

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 Your most common type of Ethernet
 connector is what we call an RJ45.

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 RJ stands for registered jack.

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 Register jack 45 and
 it looks like this.

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 So you can see here inside the plastic RJ45
 you can actually see the individual

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 cables and their pins connected
 to on this jack.

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 I'll refer to that here
 in just one second.

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 Another type of Ethernet connector is
 something called a small form factor

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 pluggable or an SFP small
 form factor pluggable.

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 And you're seeing a lot of these on
 the higher speed Ethernet connectors

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 especially like the gigabit and the
 10 gigabit connections allow those

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 make use of SFPs as opposed to RJ45s
 because they're small so you can

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 put you can cram more of these into
 the same space you would have less

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 RJ45s. So when it comes to twisted
 pair ethernet cabling so if you're

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 actually going to be cabling something
 in a lab or at your house you should

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 be aware that twisted pair cable
 comes in two varieties.

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 One is called straight
 through cable.

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 So what you've got here is you're actually
 seeing one you're seeing your

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 twisted pair cable opened up and you're
 seeing the cables the actual wires

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 inside of it. So the vast majority of
 twisted pair cable these days comes

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 with eight wires although only four
 of those wires are probably actually

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 going to be used in your implementation
 of ethernet.

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 So if you were actually to make your
 own twisted pair cable you could

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 actually get away with it.

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 A lot of times you'll see eight in
 here because the manufacture of the

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 twisted pair cable they don't know
 what you're going to use it for.

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 If they knew in advance that you're
 just going to use it for regular 10

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 megabit or 100 megabit ethernet they
 would just give you cable that has

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 four wires twisted into two pairs but
 there's certain flavors of gigabit

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 ethernet that actually use four or even
 eight pairs of wires and so that's

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 why most twisted pair cables these days
 will actually have all eight wires

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 in there. So straight through simply
 means that pin number one on one

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 end of the cable goes straight to pin
 number one on the other end of the

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 cable. Pin two goes to two, three
 goes to three, so on and so forth.

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 So in other words if I go back here if
 you had an RJ45 if you had a cable

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 and you know that both ends of the cable
 are going to have an RJ45 connector

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 if you held those two RJ45 connectors
 right up next to each other and

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 you looked at them in a straight through
 cable if one RJ45 connector had

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 for example red green blue in that order
 the other RJ45 connector would

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 also have red green blue in that order
 so it's going straight through.

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 A straight through cable is used when
 you're connecting devices that reside

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 at different layers
 of the OSI model.

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 What do I mean by that?

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 Well what layer of the OSI model
 would you typically put a switch?

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 Most people would say layer two, the
 dabeling layer whereas what layer

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 would you put a router?

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 Rowers typically fall at layer three
 so those two devices are different

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 layers of the OSI model so if I was
 connecting a switch to a router I

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 would use this I would use
 a straight through cable.

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 If I'm connecting a hub to a router
 I would use a straight through cable

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 but if I'm connecting devices they're
 at the same layer for example if

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 I want to connect a switch to another
 switch or router to another router

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 then I would use what's called a crossover
 cable so devices at the same

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 layer of the OSI model use crossover
 cables and you can see this is why

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 they call it crossover because pin one
 on one side ends up at pin three's

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 position on the other.

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 Pin two ends up at pin six and this
 actually is something that if you're

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 studying for your Cisco CCNA you would
 need to know that a crossover cable

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 if you could remember one to three,
 two to six so one goes to three, two

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 goes to six and this is for devices
 when you're a PC directly to another

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 PC, a switch to a switch you
 would need a crossover cable.

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 Fortunately for us a lot of networking
 devices these days they're networking

0:10:21.240000 --> 0:10:27.740000
 adapters are what's called auto MDIX
 and auto MDIX adapters actually are

0:10:27.740000 --> 0:10:32.580000
 able to automatically detect the cable
 type so even if you use the wrong

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 cable an auto MDIX adapter will be
 able to a lot of times when you go

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 down to your Home Depot or Lowe's or
 some other electronic store to buy

0:10:46.380000 --> 0:10:50.260000
 ethernet cable that you want to build
 yourself you'll see category five,

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 category five E, category
 six what's that all mean?

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 Well each of these categories of cables
 are tested by standards bodies

0:10:59.460000 --> 0:11:03.740000
 to see if they conform to certain
 stringent requirements.

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 They put certain voltage levels on
 there and they see what the voltage

0:11:06.820000 --> 0:11:14.780000
 level comes out and they check the heat
 of the cable they check all sorts

0:11:14.780000 --> 0:11:20.300000
 of things and so the category of the cable
 gives you an idea of how rigorously

0:11:20.300000 --> 0:11:25.900000
 this cable has been tested to meet
 certain standards and so typically

0:11:25.900000 --> 0:11:29.840000
 speaking we know that in twisted pair
 cable you've got each pair of cables

0:11:29.840000 --> 0:11:31.820000
 is twisted around each other.

0:11:31.820000 --> 0:11:36.540000
 One of the things that they measure
 is how many twists per centimeter

0:11:36.540000 --> 0:11:43.120000
 is there the more twists you have per centimeter
 the less chance of electromagnetic

0:11:43.120000 --> 0:11:47.760000
 interference but think about the manufacture
 of the cable it's actually

0:11:47.760000 --> 0:11:50.860000
 going to take them a little bit more
 work their machines have to be a

0:11:50.860000 --> 0:11:56.060000
 little bit more complex to add more twists
 per centimeter so they're going

0:11:56.060000 --> 0:11:59.500000
 to charge you a little bit more for that
 the sheath of the cable you know

0:11:59.500000 --> 0:12:03.800000
 the outer ring of the cable that that
 rubber or plastic sheath the thicker

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 it is the more it will prevent
 electromagnetic interference.

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 So with as far as categories of cables
 are concerned the higher the number

0:12:13.460000 --> 0:12:20.120000
 the more twists per inch the thicker
 the sheath of that cable.

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 So here's actually a visual representation
 of this so compare the category

0:12:24.660000 --> 0:12:29.200000
 5 cable on the top with the category
 6 cable on the bottom you can clearly

0:12:29.200000 --> 0:12:34.440000
 see that as far as twists per centimeter
 are concerned the category 6

0:12:34.440000 --> 0:12:40.460000
 cable has a lot more twists in a shorter
 space a shorter length than the

0:12:40.460000 --> 0:12:44.840000
 category 5 so that category 6 cable
 is going to be more expensive for

0:12:44.840000 --> 0:12:49.160000
 you but it will give you better electromagnetic
 interference it'll prevent

0:12:49.160000 --> 0:12:52.960000
 that electromagnetic interference
 from happening.

0:12:52.960000 --> 0:12:57.440000
 So typically what you'll hear is that
 you know as far as the cabling that

0:12:57.440000 --> 0:13:00.840000
 you're running from your laptop to
 your switch or your laptop to your

0:13:00.840000 --> 0:13:05.300000
 router a lower category of cable is fine
 because you're probably not going

0:13:05.300000 --> 0:13:08.320000
 to experience electromagnetic interference
 but if you're running cabling

0:13:08.320000 --> 0:13:12.000000
 for example in a wall where there's
 probably also going to be electrical

0:13:12.000000 --> 0:13:16.220000
 cables right next to it that's carrying
 high power electrical energy well

0:13:16.220000 --> 0:13:20.380000
 you'll probably want cable that's of a
 higher category in that case because

0:13:20.380000 --> 0:13:25.640000
 it's got more twists per inch in addition
 to that you can see here that

0:13:25.640000 --> 0:13:31.240000
 the outer covering the sheath is thicker
 the higher you go up in your

0:13:31.240000 --> 0:13:36.960000
 categories so that's one thing that
 makes different twisted pair cables

0:13:36.960000 --> 0:13:42.000000
 different from each other is is the category
 the 5 5e 6 it even goes higher

0:13:42.000000 --> 0:13:45.100000
 than that and I'll show you a chart
 here in just a moment another thing

0:13:45.100000 --> 0:13:49.280000
 you can think of is when you're buying
 pre-made cables pre-made ethernet

0:13:49.280000 --> 0:13:54.720000
 twisted pair cables you might see some
 listed as shielded twisted pair

0:13:54.720000 --> 0:14:00.500000
 and others as unshielded twisted pair
 what's that referring to well that's

0:14:00.500000 --> 0:14:06.340000
 referring to yet another attempt to block
 out electromagnetic interference

0:14:06.340000 --> 0:14:11.940000
 so shielded twisted pair is going to
 be far more expensive but that is

0:14:11.940000 --> 0:14:15.540000
 blocking out a lot more electromagnetic
 interference and shielded twisted

0:14:15.540000 --> 0:14:20.720000
 pair as you can see here each pair of
 wires not only is it twisting around

0:14:20.720000 --> 0:14:25.260000
 itself but there's an outer covering
 usually like some sort of foil or

0:14:25.260000 --> 0:14:30.400000
 some sort of mesh that's around each
 pair of wires to even give you more

0:14:30.400000 --> 0:14:36.240000
 protection against electromagnetic interference
 whereas unshielded twisted

0:14:36.240000 --> 0:14:41.780000
 pair doesn't really have that so the
 moral of the story is is if you're

0:14:41.780000 --> 0:14:45.760000
 installing ethernet cable next to something
 that has a lot of probability

0:14:45.760000 --> 0:14:48.540000
 of electromagnetic interference for
 example you're installing it in a

0:14:48.540000 --> 0:14:52.640000
 ceiling or in a wall that's right next
 to your power cables leading to

0:14:52.640000 --> 0:14:56.340000
 your you know AC outlets and stuff
 in your wall you're probably going

0:14:56.340000 --> 0:15:00.160000
 on use the highest category you can
 afford and it's best to use shielded

0:15:00.160000 --> 0:15:04.980000
 twisted pair if you can afford it whereas
 unshielded twisted pair is fine

0:15:04.980000 --> 0:15:09.540000
 connecting from your laptop or your PCs
 to the switch or router that they're

0:15:09.540000 --> 0:15:17.220000
 connected to so here is that chart I
 promise to show you that shows you

0:15:17.220000 --> 0:15:21.600000
 your different categories all they have
 to category eight when I was researching

0:15:21.600000 --> 0:15:26.320000
 this I there may even be category nine
 and ten available now I was not

0:15:26.320000 --> 0:15:29.620000
 able to find any information on category
 nine and ten by found some hints

0:15:29.620000 --> 0:15:34.420000
 to it so that might also be available
 but you can see here that the length

0:15:34.420000 --> 0:15:37.780000
 is pretty standard except when you get
 up to category eight that's pretty

0:15:37.780000 --> 0:15:42.660000
 short they all support 10 megabits and
 100 megabits but when you get up

0:15:42.660000 --> 0:15:47.340000
 into the higher speeds for example 40
 gigs we need category eight cable

0:15:47.340000 --> 0:15:58.120000
 to support 40 gigs and that concludes
 this session on Ethernet so that

0:15:58.120000 --> 0:16:03.840000
 being the case I hope this series of
 videos on Ethernet has been useful

0:16:03.840000 --> 0:16:07.900000
 and beneficial to you I hope you're
 able to use it in your studies and

0:16:07.900000 --> 0:16:10.640000
 as you move forward into the networking
 world and I hope to see you again