Network Cabling – CompTIA A+ 220-901 – 2.2

| December 6, 2015 | 0 Comments

Your network is only as good as the cabling. In this video, you’ll learn about the characteristics of fiber communication, twisted pair copper cabling, cable categories, cabling in the plenum, and coaxial cables.

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Many networking environments use fiber optics for their network communication. This is transmission using light instead of radio frequency. Since there’s no radio frequency signal, it becomes very difficult to monitor or tap this information. You’ll often see fiber optics used in very highly secure environments.

One of the advantages of light, of course, is that it’s very slow to degrade. So we can extend it over a very long distance. It’s very common to use fiber optic cables to connect sites that are very far apart. And since there’s light inside of these cables instead of radio frequencies, it’s not subject to interference from things like radio signals or electrical interference.

Here’s a close-up of a fiber optic connection. The connectors themselves are relatively large. The fiber optic is this smaller strand that’s coming out the back of that connector. If we’re going over longer distances, we’ll even put a coating around that so that there’ll be a little bit of a thicker connection so we can go a longer distance without damaging the fiber inside.

We often forget how small these fiber optic cables really are. The fiber optics are here in the core of the cable. And then in that smaller strand, you can see that orange cladding that was around the outside. To protect it even further, we’ll put that very large coating around the outside as well.

These fiber optics are very fragile. And so on the connectors that we use to plug into our components, we usually have this very hard ferrule that’s wrapped around the fiber core. It’s even difficult to see the fiber core in this picture. I’ll get rid of my highlighting so that we can point directly to the center. You can see the little bit of a difference in color there in the very center of that ferrule. And that is the core of the fiber optic.

For what we call a short-range communication with fiber optics– this is distances that go up to about two kilometers– we generally use multi-mode fiber. It’s called multi-mode because when we put the light into the fiber, it tends to bounce around and hit the sides of the fiber and bounce around to the other side. And it can enter the fiber and bounce around in different modes.

You can see three different light sources here. And you can see they’re bouncing a little bit differently in those multiple modes within the fiber. We usually have an inexpensive light source, like LEDs. And by using multi-mode fiber, we can keep the cost down instead of using a more expensive fiber type and a more expensive light source.

The more expensive fiber types of light sources are going to go longer distances. So we use single-mode fiber for those connections. Single-mode fiber allows us in some cases to go up to 100 kilometers without having to regenerate the signal and send it on its way. This is usually using a laser as the light source. And that’s why it’s relatively more expensive than a multi-mode fiber connection. This is a single-mode, so when the light goes into the fiber, we have a single light source going all the way through the connection. There won’t be multiple light modes coming into the connector on the other side.

Instead of using fiber in many of our home offices and larger organizations, we’re using a less expensive form of wiring in the form of twisted pair copper cabling. This twisted pair cabling uses a communication method called balanced pair operation. That means that the two wires that we send in a pair are going to send equal and opposite signals through this connection. That means when the signal is received on the other side, if there’s any interference in that connection, that common mode signal can be filtered out and you’re left with the original signal that came through the wire.

That’s a big reason why we twist these cables. That means that with the cables constantly twisting, there’s one wire that’s always going to be farther away from the point of interference. That way, on the other side, it makes it very easy to compare both of those wires, determine what type of interference might be in that signal, and easily remove it.

To also help remove that common mode interference, you’ll notice that the different pairs of wires within the same cable are twisted at different rates. So it’s this combination of a balanced mode operation, the twist within the individual pairs of cables, and the different twists rates that help us remove all of the interference from that cable once the signal is received on the other side.

The vast majority of the copper cabling that you’ll see used for Ethernet is unshielded twisted pair, or UTP. This unshielded twisted pair doesn’t have any additional shielding between those wires in the outside world. So if there is anything creating interference, it isn’t stopped by anything inside of that cable itself.

For environments that have a lot of electrical interference, you may want to consider using STP, or shielded twisted pair. This is exactly the same type of wiring inside of the cable, but there’s additional shielding that’s wrapped around those wires to help protect from that interference. It’s very common to see STP being used in environments where you’re in a factory or environment where there’s a lot of radio interference. That way, you can help protect the signal that’s inside of that cable. Another feature in an STP cable that is different than the UTP is this ground cable. That way, you’re able to keep the same ground across that very long distance on both sides of those connectors.

Not all twisted pair cables are created the same. So we’ve created a set of standards that we call cable categories that help describe how a cable is manufactured. On our list, we have a Category 3 cable. This was one of the earlier types of Ethernet cables that helped support 10BASE-T and allowed us to run that 10BASE-T to 100 meters.

Another type of cable that we don’t see any longer is the Category 5. This was used for 100BASE-TX and 1000BASE-T. And we generally see that also extending out and allowing us to run 100 meters for those topologies. We no longer see Category 3 or Category 5. Those category types are now deprecated. We tend to see Category 5e and higher these days.

Category 5e stands for enhanced. This allows us to run now 100BASE-TX and 1000BASE-T to 100 meters. The Category 5e was created because this 1000BASE-T, this gigabit connection, was extending 100 meters but there were certain situations where the signal was not as strong as we would have liked. So we created the Category 5e as an enhancement to improve this 1000BASE-T distance so that we could really get 100 meters out of it in the largest number of environments.

When 10 gigabit Ethernet over copper cabling was introduced, we needed a new category of cabling. So we create Category 6. Category 6 cabling could support 10GBASE-T on distances from 37 to 55 meters maximum. We also created Category 6A. A stands for augmented. This improved on this standard. We could still used this 10GBASE-T connection but we were now able to run it a maximum of 100 meters.

Another category of cable that you may see is Category 7. And I put an asterisk next to this so that you can see that it’s not a standard from the EIA/TIA. It’s just one that we happen to be using because the industry has just chosen the next number in the list. This is a shielded version of Category 6. And it’s still allowing 10GBASE-T over 100 meters. But with that shielding, we’re able to use it in environments where there’s a lot of radio interference.

In many commercial buildings, there’s actually a space between the ceiling, which is usually a drop ceiling, and the actual ceiling of the building. And inside of that space, you can have a number of different things. There can be pipes, there can be air supplies, and there can be network cabling.

If your air system isn’t using that section above your ceiling as an air space but instead has its own duct work, then you don’t have to worry about having a certain type of cabling up there because there is no plenum where you’re pulling air from a shared area above the ceiling. Instead, you have your own ductwork providing air to the floor and your own ductwork that is bringing the air back to the air conditioning system.

Some environments may not use duct space for sending or receiving the air to the HVAC. Instead, the air may be provided through ductwork, but the return air may be using the shared area, or the plenum, that’s above the drop ceiling. It’s the shared plenum where we are more concerned about our network cables that may be in this space. That’s because if there’s a fire, all of the smoke and chemicals that are on our network cables are going to get into the air space. So we have to think about exactly what type of cables we’re going to use in the plenum.

Fortunately, there’s a type of twisted pair cabling that is designed to be used in the plenum. This uses a flourinated ethylene polymer with a low-smoke PVC, this polyvinyl chloride. This means that we’re able to use this cable. And if there is a fire, it’s going to have a minimal amount of smoke when you compare it to the other types of twisted pair cabling.

This cable, however, may not be as flexible. It’s not going to have the same bend radius because it’s a different type of jacket on the outside of the cable. But you have to think about this, especially when you’re considering the worst-case scenario of a fire and making sure that everyone can get out of the building safely.

Another popular copper networking cable is a coaxial cable. Coaxial cable has a single access, or single wire conductor than is shared between two devices. So unlike twisted pair where there are multiple pairs of wires inside of that cable, in the case of coax, there is a single wire conductor.

The type of coax cable that we often see– the cable company used into our building– is RG-6. It’s used for television and digital cable. And it’s commonly used to send that internet connection over that coax, as well. Inside of our buildings, we tend to use RG-59. It’s a type of coax cable that’s specifically designed for smaller runs of patches inside of our building. We commonly don’t see RG-59 being used over longer distances.

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Category: CompTIA A+ 220-901