Network Cables – CompTIA A+ 220-1101 – 3.1

Our network cables are the foundation of any wired connection. In this video, you’ll learn about twisted pair cable categories, coaxial cable, cable shielding, direct burial cable, and more.

The cabling that’s in your network is the fundamental communications path to the rest of the world. So it’s important that you’re able to use exactly the right cable for the job. If you’re building out a new data center or building a new building, you really only have one chance to get this right. So you want to be sure you’re using exactly the right type of cable.

And although we’ve become very accustomed to using wireless networks, the bulk of our network communication takes place over a wired cable connection. For our ethernet networks, we very commonly used twisted pair of copper cabling. This is what it looks like inside of that ethernet cable. You can see that we have four pairs inside of that cable. Those four pairs have different colors. One is a solid blue. One is a blue and white. One’s a solid green. One’s a green and white. We have solid orange, orange and white, and solid brown, and brown and white.

These pairs of wires contain equal and opposite signals to each other. Sometimes you’ll see these referred to as a transmit plus and transmit minus to show that they are sending opposite signals from each other. We combine this difference in signal with a twisted cable to be able to get this information from one side of the network to the other. You can see that these have twists in them. And that means that the signal going through this wire is constantly twisting as well and effectively moving away from any type of interference as it’s moving through the cable.

When these signals arrive at the other end, those signals are compared with each other. And any interference that may have occurred through the wire is identified, because we now have two cables with different signals to be able to compare. Another interesting bit of engineering is that each of these pairs has a different level of twist rate. So there may be a tighter twist on one pair of wires then another pair. This means that if there’s interference to this cable as the data is moving through it, all four of these pairs will have different signals on the other end because they are all a different twist rates.

Of course, there’s more than just one kind of twisted pair cabling. Through the years we’ve created a number of different twisted pair types. Each one of these types has a different set of electrical characteristics and supports different kinds of networks. We refer to these different types of twisted pair cables as categories of cables. And in our ethernet standards, we create a minimum category of cable that’s supported by that standard. For example, in this chart we’ve used to different ethernet standards– a 1000BASE-T and a 10GBASE-T.

1000BASE-T is a 1 gigabit per second ethernet standard that operates on twisted pair copper cabling. And the other is 10GBASE-T which is a 10 gigabit per second ethernet that also runs over twisted pair cabling. If you were to look at the IEEE standard for 1000BASE-T, it supports a minimum of category 5 cabling to a maximum distance of 100 meters. Through the years we’ve taken that same category 5 cable and we’ve applied some additional validation tests to it. And to signify that those additional tests have been done, we refer to that cable as a category 5e. The E is for enhanced.

So if you were to purchase new cabling today, you would only find category 5e available. If you have an existing network infrastructure that already has cables in place, you may very well find category 5 being used on that network. And you can see that 1000BASE-T supports both category 5 and category 5e to a distance of 100 meters. There is an augmented version of category 6 called category 6A, which is also supported by 10GBASE-T to a maximum distance of 100 meters.

Another type of cable we commonly use, especially on cable modem networks, is a coaxial cable. Coaxial means there are two or more forms that share a common axis. And that’s certainly the case here. You can see the wire conductor is all one single conductor running the length of that coaxial cable. Around that is an insulator that also runs the same direction, with metal shielding around that and a plastic jacket around the outside. This is commonly the type of cable you would see used inside of your home with your cable television or your cable modem. And it commonly uses RG6 as the type of coax cable.

In your work environment, you might have a work area with a drop ceiling. And above that drop ceiling maybe ducts that supply the cold air and remove the warm air to send back to your air conditioning system. But with other environments, you may have ducts that provide the cool air, but the warm air or the air return is going into a shared airspace that we call the plenum. This plenum is a shared area. So not only is this an air return, but all of our network cables are usually in this airspace as well. If we have a fire in this building, we want to be sure that our network cables don’t create smoke or toxic fumes, which will then be grabbed by the air return and forced into every other part of the building.

This means if we have this shared plenum area, then we need to use a special type of network cable so that we don’t create more problems during a fire. The jacket that is around an ethernet cable is commonly made of PVC or polyvinyl chloride. If you’re putting this cable into a plenum, then you’ll need a special plenum-rated cable that has FEP, this is the fluorinated ethylene polymer, or a low smoke version of polyvinyl chloride. These cables may not be as flexible as a non-plenum rated cable, but they are safer in the case of a fire. So if you’re designing a new network run or you’re installing new cables into the plenum, make sure you’re using the appropriate type of cabling for this environment.

For most cable runs we’re using UTP or Unshielded Twisted Pair. This is a type of cable that doesn’t have any special shielding around the cables themselves or the individual wires. If you’re using ethernet cables at home, then you’re probably using UTP. In environments where there’s much more interference or you want to add some additional protection to the cable, you might want to use STP or Shielded Twisted Pair. There might be a shield around the entire cable or the individual wires themselves may have a shield. Most of these shielded cables will also have a grounding wire for some additional protection.

If you look at the outside of an ethernet cable, you’ll see some writing that describes what type of cable is on the inside. This uses abbreviations such as U for unshielded, S for braided shielding, and an F for foil shielding this is usually written with a letter, a slash, another letter, and then TP to describe the twisted pair. If there’s braided shielding around the entire cable and foil around the pairs, then we’ll have an S for braided shielding, a slash, an F for foil shielding, and then the twisted pair at the end. If we have foil around the entire cable but nothing is shielded around the individual pairs, then it is an F slash UTP.

In our picture of our shielded twisted pair here, you can see there is a shield around the entire cable but no shielding around the pairs. So this wire would be an F slash UTP. Here’s another cable. This one has a braided shield around the entire cable. And each individual pair of wires has a foil around it. The abbreviation for this is written on the cable as F slash FTP, which means we have a braided shield, slash foil twisted pair.

There may be occasions when you need to have a cable run that is outside. And in those cases, you may want to bury the cable directly in the ground, in some cases without any type of conduit. We refer to this as a direct burial STP for shielded twisted pair.

These cables are designed to be outside. So they have a special waterproofing inside of them. And sometimes they’re even filled with gel that helps keep the water away from the cable that’s on the inside. This means you may be able to put the cable directly in the ground instead of running a conduit and then putting the cable inside of that conduit. These are usually shielded twisted pair, which certainly helps to prevent any type of interference, but it also adds some rigidity and strength to the cable itself.

Here’s a cross section of a shielded twisted pair that we might use as a direct burial cable. You can see there are the four pairs of the ethernet cable. And around each of these four pairs is a waterproof gel which then has a shield around each individual pair. This helps keep the water away from any of these pairs within the cable. And there is what we call a drain wire, which is not referring to water, but instead draining away any additional voltages through a ground wire that extends the length of the cable.