Unshielded Twisted Pair or UTP is a set of 4 pairs of wires with each wire
in a pair being twisted around the other to prevent electromagnetic interference.
As an example notice here, we have a twisted pair.
4 pairs make up the UTP used in Ethernet.
Each wire has a color coded plastic insulation
and the wires are inside and outer jacket.
In an Ethernet environment the wires connected to RJ-45 connector as shown here.
The advantage of UTP or Untwisted Pair, is it's the less expenses and easier to install
than other cabling implementation such as shielded twisted pair or coaxial cable.
There are various categories of UTP which wie'll talk about in a moment.
The maximum distance is a 100 meters without the use of the signal regeneration device
such as a hub or switch, so this is the type of cabling you'll probably encounter
many, many times in your networking career, UTP uses RJ-45 connectors.
So let’s talk about the pin positions on an RJ-45 connector.
There are 2 main implementations which are T568A and T568B
and there's a slight difference with the pairing of cablings in each implementation,
TIA/EIA-568 was develop to define standards for telecommunications cabling systems
EIA is the Electronic Industries Alliance and is a standard base organization.
TIA/EIA-568C attempts to define structured cabling standard.
So the difference between A and B is the pairing of cabling.
Notice in A white green stripe and green solid are connected to pins 1 and 2
whereas in B white orange stripe and solid orange are connected to 1 and 2.
So there are several differences between the cabling
of orange and green in 568A and 568B.
Now this will make no difference as both configurations
wire the pin straight through.
In other words pin 1 goes to pin 1 onn both sides of the cable
pin 2 goes to pin 2 and so forth and so on.
So notice on pin 1 its white green in 568A but it's white orange in 568B.
The most popular implementation tends to be B, but it will make no difference
which one is use as long as both sides are connected straight through.
Now you could purchase pre-made cables or you may decide to cramp your own cables.
Pre-made cables tend to be more expensive but have the advantage that they’ve been
tested as well as the advantage that you don’t have to make them yourself.
Cramping cables yourself is cheaper
and you can make your cables for the length that you require.
When cramping your own cables you need to separate each individual colored wire
in the right order and then stick each colored wire
into the appropriate slot on the RJ-45 connector.
You then use the cramping tool to cramp the wire and finally don’t forget
to make sure that you test your cable to ensure that you've cramp it correctly.
The straight through cable is a type of twisted pair copper cable
which you're going to find very often in Local Area Network or LANs.
In a standard straight through cable each pin of the connector on one end
is connected to the corresponding pin on the other connector.
In other words pin 1 on the MDI device, in this case a PC
is connected to pin 1 on an MDIX device which in this case is a hub.
Pin 2 connects to pin 2, pin 3 to pin 3 and so forth and so on.
MDI or Media Independent Interface is an Ethernet port connections typically use
on Network Interface Card or NICs of PCs.
MDI is also use by routers and can be used on uplink ports on Ethernet switches.
On certain older switches you’ll see a button normally on the uplink port
that allows you to change how that port operates.
So you can change the mode from MDI to MDIX or back again.
This allows you to connect 1 switch to another switch using a straight through cable
rather than using a crossover cable which I'll mention in a moment.
So in the past, you may have connected your PC to a hub
such as this 2 using a straight through cable.
Now straight through cables are used in situations where you connect
the PC to a switch or a PC to a bridge, or q PC to a hub.
I’m gonna explain how this devices work in a moment
and the differences between a hub, bridge and switch
but from a cabling point of view
you would use a straight through cable from your PC to one of this devices.
In the past when connecting devices of the same type
such as 2 PCs or 2 routers, a crossover cable would be used.
So in this case rather than a pins being straight they crossed.
So in this example, we have 2 MDI devices in other words 2 PCs
which need to communicate and thus a crossover cable would be required.
This is an example for 10Base-T or 100Base-TX.
In this example pins 4, 5, 7 and 8 are not used but notice pin 1 is crossed with pin 3
pin 2 with pin 6, pin 3 with pin 1 and pin 6 with pin 2
in other words the TX or transmit and RX or receive are correctly cabled
so that TX+ is connected to RX+ and so forth and so on.
Pins 4, 5, 7 and 8 are configured in the straight through format
but are unused in this example.