Copper network cabling is one of the most popular ways to connect our computing devices, but not every copper cable is created alike. In this video, you’ll learn the fundamentals of twisted pair cabling, copper cable categories, cable termination standards, and much more.
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Your cabling is the foundation of everything that happens with your network. If the cabling is installed properly, then the network is going to operate at complete and full efficiency. If your cabling is not installed correctly, then nothing is going to work well. That’s why you really only get one opportunity to install your cable infrastructure correctly. You want to do this right from the very beginning or you’re going to run into problems very quickly with your network.
Even your wireless networks are going to rely on these cables, so you want to make sure your network is installed properly from the very beginning. Most of our ethernet networking operates using twisted pair wiring. This twisted pair copper cabling uses something called balanced power operation. That means there are two wires that interact with each other. They’re both sending the same information– one is a positive value and one is in negative value.
So you’ll see that as we’re communicating through the network, we’re twisting these wires also amongst each other. Because these wires are twisted, there will be a wire always moving away from any potential interference, and when this information gets to the other end of the wire, those opposite signals can be compared to each other to reconstruct anything that may have been corrupted by this interference.
One of the interesting characteristics of this twisted pair cable is that the different pairs of cabling are twisted at different rates. This becomes really obvious when you get up to a higher level categories such as Category 6. These different twist rates will also help in making sure that traffic is able to get through the network even when there’s interference.
Cabling is very standardized, and these standards for cabling come from many different organizations. One of these organizations is the Electronic Industries Alliance or the EIA. This is an alliance of trade organizations and they create standards for the entire industry. You’ll see their standards usually start with an RS, which stands for a Recommended Standard, or has an EIA at the beginning for the Electronic Industries Alliance. You can find all of their information at www.eia.org.
Another organization setting standards for our cabling is the Telecommunications Industry Association or TIA. In fact, the ANSI/TIA/EIA-568 standard is the Commercial Building Telecommunications Cabling Standard, and that is the standard that we always use whenever we’re putting in a cabling infrastructure in our buildings.
There is also a worldwide set of cabling standards. This is the International ISO/IEC 11801 cabling standards that define standards across any organization wherever they happen to be in the world.
These organizations have created standards for copper cabling that they call cable categories. This means that we as the end user can simply ask for the type of cable category that we need for a particular purpose rather than trying to find a cable that has a particular twist rate or a particular ohm value. For example, in our not-so-distant past, when we needed to run 10BASE-T ethernet standard, we would want to run that over 100 meters, and the type of cabling that we would need to support that would be Category 3 cabling.
When the speeds of our networks increased to 100 megabits and 1,000 megabits, using the ethernet standards of 100BASE-TX or 1000BASE-T, we could run those to 100 meters using Category 5 cabling. There were some minor changes made to the Category 5 standard. This change is the Category 5e standard. The e stands for enhanced. It still allowed us to run 100BASE-TX and 1000BASE-T ethernet standards to 100 meters, but it was able to do that with some minor enhancements to the standard.
When we jumped to 10 gigabit networking using the ethernet standard 10GBASE-T, we were able to network 37 to 55 meters of distance using Category 6 cables. And we were able to improve that distance to 100 meters using Category 6A– the A stands for augmented.
If you were to look at a cross-section of a commercial building, the place where everybody’s working is here in the bottom area underneath the drop ceiling. If you were to look above the drop ceiling of your office and you saw that there was duct work providing air supply from the HVAC and there was separate duct work providing the air returned to the HVAC, then you would say that there was no plenum in this office configuration.
This plenum is the shared area above the drop ceiling where you would have return air, but we might also run our network cables in that plenum– there might even be water pipes that run in that plenum. This is obviously a concern from a fire perspective. If you do have a fire that gets into the plenum and you have network cabling there, that network cabling could provide fumes that might be dangerous for other people in the building. So your worst-case planning would be to think about what happens during one of those situations, and you want to be sure to have the proper network cabling if it’s going to be in a plenum.
The jacket that’s on the outside of a network cable is traditionally made of PVC. This is polyvinyl chloride, and if polyvinyl chloride catches on fire, then there could be fumes that might be toxic to human beings. So if you’re running cable inside of a plenum, you want to use a plenum-rated cable– this is a fire-rated cable jacket that’s made of either FEP– this is fluoridated ethylene polymer, or something that is a low-smoke polyvinyl chloride. This is a way that you’re able to minimize the impact if there’s a fire but still have a proper type of cabling to use in that plenum area.
This plenum-rated cable jacket that’s on the outside of these cables may not be as flexible as your traditional PVC cable, so you do have to think about how you’re going to run that cabling if you get into a tight area. But the important thing to consider is that you have the proper safety precautions in place, and if you’re engineering or building out the cabling in your building, make sure you’re using the right kind of cabling depending on where it’s going inside of your plenum or outside of your plenum.
If you stripped away the outer jacket of the ethernet cable that you’re using on your computer, it would probably be UTP or Unshielded Twisted Pair. There’s no additional shielding in an untwisted pair cable, it’s simply the outer PVC jacket and the cables inside.
If you work in a manufacturing environment or an environment where there’s a lot of electrical equipment or other equipment that might cause interference, you might want to use STP or Shielded Twisted Pair, and you can see the shielded twisted pair, there is a foil shield that is around all of those wires. Some shielded twisted pair even has a shield around the individual pairs of wires themselves. You’ll notice the shield twisted pair also has a grounding wire, so that’s another consideration if you’re planning to install STP.
It’s difficult to know whether you’re using UTP or STP if you simply look at the outside of the cable. But there’s usually some printing on the outside that can help you make that determination. If you see an abbreviation of U, then it’s an unsheathed twisted pair cable; if you see S, it’s a braided shielding; and if you see an F on the outside of the cable, it is a foil shield.
So what you should expect to see is that there is a letter that identifies what the shielding is for the overall cable, and then a separate letter that identifies what the shielding is for the individual pairs. If your cables are like this one, it has foil around the cable itself but no shielding at all around the individual pairs, it will be labeled as F/UTP.
Here, for example, is a Category 7 cable that’s labeled with S/FTP. That S means that there is a shielded cable around all of the wires that are inside of this cable, and then the FTP specifies that each pair of wires will have a foil shield around each pair. You can see those combined together will be the S/FTP.
Now that we’ve chosen the right category of cable, we’ve decided whether it’s going in the plenum or outside of the plenum, and we’ve decided if it’s going to be unshielded twisted pair or shielded twisted pair, now we somehow have to match each one of those individual wires with the pins that happen to correlate to our ethernet connection. That standard for pins is called T568A and T568B termination standards.
These standards come from the EIA/TIA, and the standard that specifies the termination type is called 568B standard. Technically this is the eight conductor 100-ohm balanced twisted pair cabling standard. The connector that’s on the end of your ethernet cable is an RJ45 connector. This is also called an eight position, eight conductor connector. And this EIA/TIA standard specifies two different ways that you could punch down the pin-outs for any type of ethernet connection.
The standard specifies that you would run the pin-outs associated with T568A if you’re running cabling horizontally– that means on the same floor of a building. But many organizations have chosen to use 568B, and once you run one type of cabling standard in your environment, you tend to use that same standard everywhere.
What you don’t want to do is terminate one side of the cable with the 568A pin-out and the other side of the cable with the 568B pin-out. These will create problems for you– you won’t be able to run ethernet at gigabit speeds, for example, and you may find some confusion when you’re trying to troubleshoot problems with your cabling.
These are the two standards for 568A and 568B. These numbering standards are associated with the pins in your ethernet connector. You can see the RJ45 connector here, and they’re pins number 1 through pins number 8. We’re assigning a different color to each individual pin depending on whether it’s 568A or 568B.
One thing you’ll notice is that there are similarities between these two standards. For example, pins 4 and 5, which are blue and white and blue, and pin 7 and 8, which are white and brown and brown, are exactly the same whether you’re wiring with 568A or 568B. The only pins that are different between the two would be pins 1 and 2 and pins 3 and 6. And you can see that they are alternating between white and green and green and white and orange and orange.
With 568A, you have white and green and green in pins 1 and 2, and white and orange and orange in pins 3 and 6. With 568B, those colors are swapped. So you can see pins 1 and 2 are the orange pairs, and pins 3 and 6 are the green pairs.
Once you get some practice, you should be able to look at an ethernet cable and see the different colors and determine what cabling standard was used for this particular cable. You can see there is white and orange and orange, there’s white and green, blue, white and blue, green, what looks like white and brown, and then a brown. And if we were to look at our 568B standard, we would see that those colors match these pin-outs exactly.
Another type of cable that you might find for a wide area network cable modem and other uses is a coaxial cable. Coaxial means there are two or more forms that share a common axis in this cable. For example, we have the wire conductor that is in the middle of the cable. It is surrounded with a dielectric insulator, and around that is usually a metal shielding. All of this is then protected with a plastic jacket along the outside.
If you’re bringing in a digital cable modem connection, it’s probably coming into your facility using RG-6– that’s the coax standard for that cabling. If you are then patching that cable connection to other devices, you’re probably using RG-59, which is really designed for patch cables and not designed for a long distance communication over coax.
Category: CompTIA A+ 220-1001