Instructor: In this Lesson,
we're going to talk about twisted pair cable.
Now twisted pair is going to be the most popular local area
network cabling technology
that we're going to use in our networks today.
If you're plugging in a network cable to your laptop
or your desktop,
you're usually doing this using a copper twisted pair cable.
Inside this cable,
there are eight individually insulated wires
that are going to be inside of this cable sheath.
And each of those is twisted up into a pair,
which is why we call it twisted pair cable.
Now if you open up this cable,
you can see there are going to be four pairs,
each twisted with two wires in each of those pairs.
Now the twist here is really important.
The more twists you have within an inch of the cable,
the better the protection that cable has
from electromagnetic interference or EMI.
If you have less twist,
then the cable becomes more susceptible
to more electromagnetic interference.
And this will also mean
you have slower speeds for your cable.
This becomes really important
because the more interference you have,
the worse your data transmission rate is going to be
because you have to retransmit your data more often.
This is going to slow down
your overall throughput and bandwidth in your network.
As we go through this lesson, we're going to start to
discuss the different categories of cable,
going from Cat5, up to Cat8.
And the common theme here
is at the higher the category number,
the more twist you're going to find per inch of cable,
and therefore the higher speed that particular cable
category is going to be able to achieve.
Now when we're dealing with the twisted pair cabling,
you're going to hear it broken down into one of two types,
either UTP or STP.
UTP stands for unshielded twisted pair,
and STP stands for shielded twisted pair.
On this screen, you can see an example
of an unshielded twisted pair cable.
Now notice the wires are twisted
and they're covered in this plastic jacket on the outside
that's going to protect it from the elements.
Now with UTP, you're going to find a much cheaper cable.
When you start using STP,
it's going to be a little bit harder to use
and it's going to cost a little bit more.
When you're dealing with UTP,
there is no metal being used in the part of the shielding
and therefore UTP is going to be cheaper
because it's all plastic, except for those thin copper wires
inside of our four pairs,
making up those eight wires.
Now because of its low cost and its easy use,
unshielded twisted pair cabling is the medium of choice
for most local area networks these days.
UTP can be bent very easily
as you're pushing it through conduit
throughout your ceilings and your walls,
and you can install it with very low cost tools
and just a few days of training in most cases.
The second type of twisted pair cable is known as STP
or shielded twisted pair.
Now STP is just like UTP,
except each twisted pair inside that cable sheath
is going to be wrapped with some metal foil.
And there's also going to be
this braided metallic shield wrapping
around all four of those pairs.
This means the wires in an STP cable
are going to be twisted up in pairs just like they were in UTP,
but the difference is they have this metal shielding
that helps minimize EMI
between the inner twisted pairs even more.
And there's also this outer braiding shield
to minimize EMI from the outside environment too.
Essentially, we're taking the best things from UTP
and all that shielding from using a coaxial cable
and putting it into one device.
Now because of all this extra metal though,
this is going to make shielded twisted pairs cost more
than an equivalent category of unshielded twisted pair.
Other than that, STP and UTP operate about the same
with the exception of the EMI interference
that's going to be less with STP.
Now, both STP and UDP
both have the same amount of distance limitations.
Either of them can go about a 100 meters
which is around 300 feet.
Both also use the same type of connectors to terminate them,
and the wires on the inside are exactly the same
with the exception of that metal shielding
being wrapped around them in the case of STP.
Now, speaking of connectors,
let's talk about the two connector types
that's used with twisted pair cabling.
These are RJ45 and RJ11.
Now RJ45
is the most commonly used connector in our networks.
The RJ45 connector is a plastic eight pin connector
and it looks like a fatter version
of a traditional landline phone jack.
Now RJ45 is used all the time in ethernet based networks,
including ones
with Cat5, Cat6, Cat7 or Cata cables.
If you're using an RJ45 connector with a Cat5 cable,
it's only going to have to use four of the eight pins.
The other four are reserved for future use,
but they can be used for other applications
such as power over ethernet and things like that.
Ever since we moved to gigabit ethernet
with 1000 based T and higher,
all four pairs and their eight pins
are going to be used for data transfer.
We're going to talk more about the different categories
and speeds in just a moment.
The second type of connector that we use
with twisted pair cables is known as RJ11.
Now RJ11 is a six pin connector.
And when used in an RJ11 configuration,
only two of those pins are actually going to be used.
Commonly, you're going to find this in phone systems
to connect your phone to a landline jack.
Now, one of these pins is going to be reserved for the ring
and one is going to be reserved for the signal
inside of these phone systems.
If you're using a DSL modem for your internet connectivity
or you're providing VoIP services
through an analog telephone adapter,
you may come across an RJ11, but otherwise,
they're not very common inside our local area networks.
When creating one of these phone lines,
you can simply use Cat5 or similar cabling
and then put an RJ11 connector on the end
instead of an RJ45.
Now as I said, in most networks,
you are going to be using an RJ45 connector
at the end of an unshielded twisted pair cable
because these are the most common thing
you're going to run across in the field.
Now you may be wondering, "I keep saying, RJ,
what does RJ stand for?
Like RJ45 and RJ11?"
Well, it stands for registered jack.
Basically, they are the standardized telecommunication
network interfaces that are used to carry voice or data
and they specify the standards that the device needs to meet
in order to connect to the phone or data network.
There are lots of different variants out there,
but RJ11 is used for phone networks
and RJ45 is used for data networks
as the two most popular ones out there,
and these are the only two you need to know for the exam.
All right, let's talk about bandwidth and throughput.
Bandwidth is your theoretical measure
of how much data could be transferred
from a source to its destination.
Throughput on the other hand is the actual measure
of how much data is successfully transferred
from a source to its destination.
Now notice, these terms are very closely related
and you'll often hear people use them interchangeably
when you're working in the field,
but technically there is a subtle difference here.
As we talk about the different cables and categories,
we're going to be talking about them in terms of bandwidth,
which is their theoretical measure
of how much data could be transferred
from the source to a destination,
as opposed to what you may see in your own networks
under real world conditions, that real world conditions
and the things you're seeing, that is throughput.
All right, for the exam,
you need to know several different categories
of twisted pair cabling,
specifically Cat5, Cat5e, Cat6, Cat6a, Cat7, and Cat8.
For each cable type,
you need to know it's category number,
it's ethernet standard,
the bandwidth or transmission speed it uses
and the maximum distance it can operate.
Now when I mention an ethernet standard,
this is going to be a designation
given to a particular category
and allows us to really easily understand the bandwidth
and the cable type that's going to be used.
For example, just looking at that standard number,
you can tell if it's copper or fiber.
First, we have Cat5 with a 100 based TX,
which was called fast ethernet.
Now fast ethernet operates at a 100 megabits per second,
which is why it is called a 100 based TX network,
now the TX here stands for twisted pair fast ethernet
and is the only twisted pair network
that uses something other than a T in the base notation.
Cat5 cables or 100 base TX cables
can only go up to a 100 meters in length
before their signal must be repeated using a switch,
a router or some kind of a repeater device.
Next we have Cat5e, which is known as 1000 base T.
Now a 1000 base T network or gigabit ethernet
is going to operate at 1000 megabits per second,
which is also known as one gigabit per second.
Again, our distance here is limited to only 100 meters.
Next we have Cat6,
which can operate either 1000 based T or 10G based T.
Now if Cat6 is going to be used with a 1000 based T network,
it can operate at 1000 megabits per second,
or one gigabit per second, just like Cat5e did,
and it goes up to 100 meters in length.
Now Cat6 can also go faster
and it can go up to 10 gigabits per second,
using a 10G based T network.
But when you use this higher speed,
you can only go 55 meters instead of the full 100 meters.
Next we have Cat6a, which was an improvement over Cat6,
Cat6a will allow you to operate 10G based T networks
at that full 10 gig bits per second,
all the way up to a 100 meters.
Next we have Cat7 and Cat7
is going to operate 10 G based T as well,
giving you that full 10 gigabits per second
at up to a 100 meters.
Oddly enough, Cat7 was actually released over six years
before Cat6a was,
but it could use either a traditional RJ45 style connector
or a different connector known as TERA, T-E-R-A,
and therefore it was able to reach 10 gigabit speeds,
much faster over the a 100 meters
before Cat6 could be modified into the newer Cat6a standard.
All that said, for the exam,
I just need you to remember that both Cat6a and Cat7
are both considered 10 G based T networks
and can operate up to a maximum of 100 meters
at a speed of 10 gigabits per second.
Finally, we have Cat8,
which can operate 40 G based T networks,
which is able to provide 40 gigabits per second,
but only up to 30 meters.
All right, let's summarize with a chart
and see if we can find the easy way
to memorize all these different facts and figures,
starting with Cat5 and going up to Cat7
we can just start multiplying by 10 each time
to get our bandwidth and our ethernet standards.
So we go to a 100 megabits per second,
to a 1000 megabits per second, to 10 gigabits per second.
For Cat8, you just have to remember that it switches
by multiplier of four,
getting us up to 40 gigabits per second.
Now for the distance, this is also pretty easy
because it's almost always going to be 100 meters.
Now there are only two exceptions,
so if you can remember, the exceptions are Cat6 at 55 meters
and Cat8 at 30 meters,
then you just need to remember the rest
are all going to be 100 meters.
Now let's talk about length for just a minute here
because you're going to get questions on the exam
where the answer comes down
to how long the cable's going to be.
Now they won't usually come straight out
and ask you a question like,
what's the maximum length of a Cat5e cable,
that would be way too easy.
So instead they're usually going to incorporate it
into some kind of troubleshooting question.
For example, you might get something that looks like this,
"You are working as a network technician
and a user in the corner office is complaining
that they're having intermittent network
connectivity issues when using a Cat5e cable
and connected to the LAN.
Their office is 85 meters
from the closest intermediate distribution frame.
Which of the following might be the source
of their connectivity issues?"
Then you might get some options like,
"The connection is set to half duplex
instead of full duplex",
or, "The connection may have exceeded the maximum distance
for a Cat5e cable"
or, "The connection is using WPA instead of WPA2"
or "The connection needs to be set to encrypted
instead of unencrypted."
The answer here would be that the connection
may have exceeded the maximum distance for a Cat5e cable.
But wait a minute, Jason, didn't you just say
the maximum cable length was a 100 meters?
And this question said, we were only 85 meters away.
What the heck is going on here?
Well, yes, the maximum cable length is a 100 meters,
but that's often the maximum, not the minimum.
Oftentimes in the real world, you're going to see
that you can't get a full a 100 meters in cable length
from these type of cables because there's interference
from fluorescent lights and other sources of EMI.
Also, the question said that the IDF was 85 meters away.
Not that the cable length was 85 meters.
So if the IDF is 85 meters away,
you're still going to have to run that cable
from the patch panel up from the IDF into the ceiling
and then from the ceiling over to the office
and from the office ceiling, down to the wall drop.
And then from the wall drop,
you have a patch cable connecting to the computer.
All of this is going to add length
because going up and down to the ceiling
might be another four or five meters.
You might also have to go from that patch cable,
might be a 15 or 20 meter cable
going from one side of the office to the other.
You can't just assume that there's a straight line
from the IDF to the corner office,
because it might not be true.
For this reason, I usually recommend keeping your cable runs
under 70 meters in length when you're going from the IDF
to the office that you want to run the jack to,
this allows for the ups, downs, overs and arounds
that you're going to actually have to do
when you're running that cable.
Now, would I expect you to get this question right
if I asked it to you right now?
Well, no, because we hadn't even covered
all the things covered in this question,
but I wanted to give you an idea
of how these questions are going to be worded
and work together to combine concepts
across different domains into a single question.
All right,
so now that we've talked about the different cable types,
their categories and the connections, we need to talk about
how to actually wire these cables into the connectors
to allow us to connect these things to our devices
using the right pinouts, because one of the exam objectives
states that you should be able to troubleshoot common issues
using the appropriate tools, such as a cable stripper,
cable crimper and cable tester.
So to ensure you're ready for that,
we need to talk a bit more about the way the ends are wired
and the proper sequence
for the pinouts of these connectors.
Now, a straight through cable
is also known as a patch cable.
This type of cable contains the exact same pinouts
on both ends of the cable,
this is why it's known as a straight through,
because pin one on one side goes straight on through
to pin one on the other side of the cable.
Now to keep everyone consistent when we make cables,
you're going to find there's a standard pinout known as a 568A
and a 568B standard.
Now 568B is the standard that's preferred
for wiring jack's inside your buildings.
And most people are going to use a 568B
to 568B wiring scheme for straight through patch cables.
Now what does that look like?
Well, if we count our pins from one to eight,
we're going to have a color scheme of orange white, orange,
green white, blue, blue white, green, brown white, brown.
That is going from pins one to eight.
So both sides of our cable will match up,
and this will create a straight through patch cable.
But if I wanted to connect a switch to another switch,
I have to use a different type of cable
known as a crossover cable.
Any time you connect a terminal to a terminal
or communication equipment to communication equipment,
you have to use a crossover cable.
So if I connect a computer to a laptop,
that's going to need a crossover cable.
If I'm connecting a computer to a switch, I don't need one,
I can use a patch cable.
So what makes a crossover cable so special?
Well, a crossover cable
is going to take your send and receive pins from that cable
and swap those on the other end
when you create your connector and you pin it out.
So on one end, you're going to need to have a 568B,
and on the other end, you're going to have a 568A.
This is used to connect a workstation to a workstation,
or a switch to a switch.
Now in general, you should always use a crossover cable
when you're going from a switch to a switch.
For the exam,
I want you to remember that a switch to a switch
requires a crossover cable.
The reason I'm making a big deal about this
is that in the real world, this isn't always the case.
Now this is because most modern switches
have something known as MDIX,
which stands for medium dependent interface crossover.
Essentially MDIX is an automated way
to electronically simulate using a crossover cable
even if you're using a straight through patch cable.
Essentially your moderate switch if it supports MDIX
will allow you to use a patch or a straight through cable
and it will switch the pinout electronically inside itself
to make it work.
Remember, when there are two switches
and they're not communicating,
it's usually because somebody is putting a patch cable there
or a straight through cable there
instead of doing a crossover cable
and that switch doesn't support MDIX.
If your switch doesn't support MDIX,
you'll have to use a crossover cable
to make those devices talk.
All right, let's look at the pinout a little bit closer,
and this time let's look at our 568A
and 568B wiring standards.
Remember 568B
is the standard we use for all our interior wiring
and for both ends of a straight through cable or walljack.
But if we want to do a crossover cable,
we're going to use 568B on one end and 568A on the other end.
When you do this,
you're going to start with 568B on one end
and then switch out pins one, two, three, and six
on the other end so that we have our transmit
and receive pins in a different place
when we create that crossover cable.
Essentially, your origining your green pairs
are going to swap places.
Now do you have to memorize this?
In the real world,
you really don't have to have it memorized
because you can carry your smartphone with you
or a small chart in your pocket.
And whenever you're going to make a cable,
you could pull it out of your wallet and look at it.
But for the exam, you need to know this pattern.
When it comes to the physical construction of your cables,
there are three types you need to be aware of.
These are known as direct burial, plenum and non-plenum.
Direct burial cables
are cables that can be run directly in the ground
and then covered with dirt, cement or concrete.
And these tend to have a thicker sheathing,
which helps them protect themselves from the weather,
from the water and other environmental elements.
If your cable is not rated for direct burial,
you'll need to run conduit first and then place your cables
inside that conduit before burying it under the ground.
Now, the last thing we need to talk about
in terms of copper cabling
is the concept of plenum versus non-plenum.
So what does plenum mean?
Well, plenum cable is a special coating
that's put on an unshielded or shielded twisted pair cable
and it provides a fire retardant chemical layer
to the outer insulating jacket of that cable.
Now if you have a plenum rated cable,
this means it's more fire resistant,
and it also minimizes the amount of dangerous fumes
that are released if the cable catches on fire.
If you're going to be running cables
in a place that you physically can't see,
such as the ceiling, the walls, a raised floor
or near air ducts,
you must use plenum cable per the laws
and county requirements in your state
or in the county in which you live.
Now, plenum cable is a bit more expensive
than non-plenum cable,
but it is a major safety issue to not use plenum cable.
So you simply have to use plenum cable
anytime you're going to put a cable
in a place that your users can't visibly see.
Now on the other hand, if you're running a cable
from a walljack to the back of your desktop or laptop,
you don't need to spend the extra money on plenum cable.
For these connectors,
it's okay to save a little bit of money
by using these non-plenum rated cables.
non-plenum rated cables are also known as PVC,
and they can either be shielded
or unshielded twisted pair of cables.
Now on the exam, remember
plenum is for anything you cannot see,
but again, you cannot put non-plenum cables
in your ceilings, walls, raised floors or air ducts.
This is a big, big no-no
and it's a very dangerous thing
for the safety of your networks and your people.