10. 6.9 Punch-Down Blocks
So far in this module, we’ve been talking about 66 blocks and 110 blocks as punch-down blocks that we might find in a wiring closet where we’re physically punching down building wiring into the conductors inside the punch-down blocks. But CompTIA wants us to know about a couple of extra punch-down block types for the Network Plus exam.
So that’s what we’re going to be doing in this video. We’ll compare the 66 and 110 blocks, as well as two others we should be familiar with: The Chrome and Bix punch down blocks. Now, let’s begin with the 66th block. And this is almost a legacy punch down block because it has been used for decades. It was used for PBX connections. It used category 3 cabling, which let us go at a blazing speed of ten megabits per second. But some newer variants of the 66 block can actually support category 5E, so they still might have a place in today’s networks. Now, the 110 block is what we typically prefer over the 66 block; it’s generally going to give us support for category six A and anything lower than that, and category six A is going to get us ten gigabits per second, possibly over 100 meters. Those are the ones that we’ve talked about thus far.
Now, the two extra pushdown block types that CompTIA says we should know about are the Crone and the Bix punch down blocks. First, consider the crone—by the way, that’s the German word for crown. And we might see a Crone punch down block as opposed to a 110 block in Europe. And it does have a characteristic that is really unique. Instead of the solid copper wires that a 66-block or a 110-block would require, the Chrome punch down block will allow us to punch down stranded conductors as well as solid conductors.
The Bix is another punch down block top I want you to know about. Bix is an acronym that stands for Building Industry Cross Connect. And typically, a Bix punch down block is going to support category 5E. But there’s a variant to BIKs called Gigabytes, and that’s the Gigabytes standard. It exceeds category-six specifications. Specifically, it supports a maximum bandwidth of four to eight gigabits per second. And that’s a look at four different types of pushdown blocks that CompTIA says we should know about for the Network Plus exam.
11. 6.10 T568 Standards
within a twisted pair Ethernet cable Each of the eight wires in that cable has an outer insulator with a unique colour code. It might be a solid color. It might be a couple of colors, where one of those colours is white. For example, the solid colors are going to be either orange, blue, green, or brown brown.
And the two colour combinations are going to be white, orange, white, green, white, blue, white, and brown. So when you’re connecting the end of one of these Ethernet cables into an RJ 45 connector, what colour insulator should go to what pin of that RJ 45 connector? That’s what we’re going to be discussing in this video. First, let’s talk about a couple of standards bodies. There is the American National Standards Institute (ANSI), which we pronounce ANSI, and the Telecommunications Industry Association, or Tia. We pronounce Tia, and there are different ANSI Tia standards for cabling. But the specific standards we’re focusing on here dictate which wire insulator colour gets connected to which pins in an RJ-45 connector.
And the two main standards And you see those pictures here on the screen as the T 568 A and T 568 B standards. And if you look at an RG-45 plug from the bottom, that is, from left to right, the tabs on the opposite side, We’re going to be numbering the pins one through eight. And when you’re wiring a jack or connecting an RJ-45 plug to a twisted pair cable, most often today we’re going to be using the T-568-B standard that you see on screen.
Notice that on pin 1, we have a primary white insulator with an orange stripe. Pin two is going to have a solid orange wire. And if you look closely at the diagram of the RJ45 connector on screen, you’re going to see that this RJ45 connector is wired using the T 560 B standard. And that’s most likely what you’re going to be working with today. However, if you do go into an older installation, please keep in mind that it might have been wired using the older T568A standard. And as a reference on screen, I’m showing you what that color code is.
12. 6.11 Straight-Through vs. Crossover Cables
When we’re looking at an RG-45 connector on the end of an Ethernet cable, it’s likely to be color-coded like we see here. This is the T568B standard, where pin one is a white wire, pin two is an orange wire, and so on. And different wires are used for different purposes. And this is great if we have a straight-through cable with the same pinout on both sides of the cable and we’re connecting a PC to a switch. Everything works out perfectly. In fact, let’s take a look at using a straight through cable between a PC and a switch, and we’ll take a look at 10 BASE-T and 100 BASE-TX. First of all, these are older technologies running attend megabits per second and 100 megabits per second. And the PC is going to be called a Media-Dependent Interface, or MDI for short. And on the MDI side of the connection, pins 1 and 2 are used for transmission, and pins 3 and 6 are used for reception. But we’re plugging this into a switch, and it expects straight cables coming into it from end devices.
So it knows that whoever is connecting to it is probably transmitting on pins one and two. As a result, the switch will receive on pins one and two. We want to transmit on one side and receive on the other. And similarly, on the switch side of the connection, pins 3 and 6 are going to be used for transmit because those pins are used for receiving on the PC side and because the roles have been reversed. Instead of calling the switch port an MDI port, it’s called an MDI exporter or a Media dependent Interface crossover. And that brings up the question, “What if we’re interconnecting two switch ports?” They’re both MDIX ports; they’re both trying to receive on pins one and two, and they’re both trying to transmit on pins three and six.
How does that work? Well, a lot of switches have a feature called AutoMDX that will allow the two switches to determine which side is going to be using pins one and two for transmitting and which side is going to be using pins one and two for receiving. They’ll negotiate that between themselves. with automatic MDIX However, this straight-through cable works perfectly when we’re just going from a PC into a switch. But if we’re trying to interconnect a couple of PCs, for example, then we have an issue. Those PC network interface cards most likely do not support Auto MDIX. Instead, we need a cable that will take the transmit leads on one end and map them to the received leads on the other, and vice versa. That’s what we get with a crossover cable.
And here we see a crossover cable that we might use in the older 10 BASE-T and 100 BASE-TX networks, where we’re just using pins 1, 2, 3, and 6. Notice how pins 1 and 2 on one side are mapped to pins 3 and 6 on the other. So transmit is going to receive, but we’re having to terminate that cable differently in order to make that swap. It’s not happening automatically. And something else I want you to notice is that in this eight-wire cable, with these older standards of 10 BASE-T and 100 BASE-TX, we’re only using four wires. We’re only using pins 1, 2, 3, and 6. And in my early days of networking, this was back in the 1990s, when we were wiring up offices in a university for 100 base TX. We thought we could save some money by only using one cable to service two PCs in an office. Here was the thought process.
We thought we’d got eight wires; each PC only needs four wires. So we would do what was called “splitting the pairs.” We would run one cable into an office, and we would take four of those wires in that cable and wire them to an Ethernet jack on pins 1, 2, 3, and 6 of that Ethernet jack. And we’d connect the other four wires to a different Ethernet jack on pins 1, 2, 3, and 6. And then, down in the wiring closet at the other end of the cable, we would take those pairs again and split them into two different connectors going into our Ethernet switch. And we thought it was a great way to save money while wiring offices with multiple connections. However, that presented a problem when speeds increased and we got up to one gigabit per second, because with 10BaseT networks, now we’re using all eight wires.
So now those PCs that only had four wires going to their jack because their neighbor was using the other four wires, yes, those had to be rewired. So it was not a good solution in the long term. And here we see that pin out. For one gigabit per second Ethernet, we’re using all eight wires. And if you wanted to cross over a cable like this so one PC could talk to another PC as a reference, here’s what those pin mappings would look like. And that’s a look at straight-through cables, where the pinout on one side matches the pinout on the other side of the cable. And crossover connections, in which the receive leads on one side of the cable map to the transmit leads on the other, and vice versa.
13. 6.12 Ethernet Standards
In this video, we want to talk about some different Ethernet standards. Some of these standards will employ copper cabling (also known as twisted pair cabling), while others will employ fibre optic cabling. And then we’ll talk about some different approaches for carrying on multiple conversations simultaneously. I brought this to Cabling, and this is one of those videos where you might need to make some flashcards for your study. Now, this is not a comprehensive list of all the different Ethernet standards out there. There are many more. However, these are the ones that I want you to memorize. First, consider the copper cabling Ethernet standards, beginning with Ten Base T. This is now a legacy technology, but Ten-based T running at a blistering ten megabits per second could use existing cabling thanks to PBX Systems. That’s right, the telephone system wiring in a lot of buildings could be used to carry 10-base T. And that was a way that we hooked up networks in the early days. And that’s what I did back in the early 1990s. And we had a distance limitation of 100 meters. However, ten megabits per second is fairly slow, so we went up to 100 megabits per second. In other words, 100-base-TX over Cat-5 is still unshielded twisted pair capable of 100 megabits per second. Same distance limitation: 100 meters. Then there was 1000 base T.
In other words, one gigabit per second. That would require a category of five or higher. And the recommendation is that you go higher. The recommendation is that you should use at least Cat 5 E if you’re doing 1000 base T. Although technically the specs say that it will work on Cat 5, Again, we have that 100-meter distance limitation. When we go up to ten gigabits per second, then you have the option of using Cat 6 at the low end or Cat 6 A or higher.
And when my wife and I recently built a new home, I thought, “I’m going to wire this so that it can do ten gigabits per second over 100 meters.” And I finally used the Cat 6. A cable. I kind of wish I’d use the Cat-6 cable at this point because the Cat-6 A cable is thicker. I had to get special terminators for it. It had all this shielding on it—foil and wire mesh. It was difficult to work with. And I really didn’t need 100 meters. In my home, 55 metres would have been fine. And Cat 6 cabling allows you to travel 55 metres much more easily. But if you need the 100 meters, yeah, you might want to use Cat 6A or higher. And in data centers, you may see 40 Gbit/s running at 40 gigabits per second. Now, that’s going to fall under category eight cabling, and it only runs 30 meters. That’s why I emphasise that it’s probably going to be used in a data centre environment.
This would not be good for your building infrastructure. That might be a little too limiting when it comes to distance. But if you’re making these short runs within a datacenter and you want to do it using copper, yeah, you can do that using category 8 copper. Consider fibre optic cabling and recall that there are two broad categories: multimode fibre and single mode fiber, or MMF and SMF, respectively. With multimode, or MMF, we typically have shorter distances that we can travel because we have multiple modes of light in this fibre optic core.
Then we can have multimode delay distortion, where one binary bit literally passes up another binary bit because of the way that other binary bit is bouncing back and forth off of the cladding. We don’t want to corrupt our data by going too far on a multimode fiber. And 100-base FX uses multimode fiber, and this is what I used at a university where I used to work. And it would run at 100 megabits per second, and we would interconnect buildings using 100 base FX. There was a two-kilometre distance limitation, and that was fine for connecting any two buildings we had on campus. The 100 base SX was a less expensive version. This still uses multimode fiber. It still gave us 100 megabits per second, but the distance was limited to 300 meters. The reason is the hardware used in the light source and the light sensor. Those were less expensive.
They were manufactured to less exacting tolerances. Therefore, it was less expensive. But you sacrificed the distance. If you want to go up to one gigabit per second on fiber, you’ve got several options. One option is 1000 base SX, and this is for shorter connections as opposed to longer connections. That’s 1000 base LX for longer connections with SX; for shorter connections, you actually get different distance limitations depending on the diameter of the core in your multimode fiber. Now, there’s a lot of multimode fibre out there. Primarily, what I’ve used has a diameter of 62.5 m. However, there is a different type of multimode fibre that has a smaller core.
Its core diameter is 50. Because the core is smaller in diameter, we’re going to have less multimode delay distortion, which means we can go a longer distance. So using multimode fibre with 1000 base SX, we can go 220 metres if we’re using the very common core diameter of 62 m. But if we have that other type of multimode fibre with a core diameter of 50 m, yes, we can get up to 550 meters. With 1000 base LX, we could use either multimode fibre or single-mode fiber. If we are using multimode fiber, the maximum distance we can get is the same as what we could get with 1000 base SX, which is 550 meters. But if you happen to be using single-mode fiber, where we’re not worried about that multimode layer distortion, we can go much further. We can go to number five.
Let’s take a look at 10-gig solutions. Ten G of base SR SR stands for short range and will employ multimode fiber. It does give us ten gigabits per second, but the distance is fairly limited. And the distance, again, depends on the core diameter of that multimode fiber. There are actually different grades of multimode fiber, and I’m showing you the best grades. Distance limitations for these two different diameters are as follows: at 62 5GB, SR can go a maximum of 33 meters, or with the highest grade of multimode fiber, whose core diameter is 50 m, we can go a maximum of 400 meters. For longer range, we might turn to a ten-G-based LR. For long range, that’s going to use, of course, single-mode fibre to avoid that multimode distortion, and it does give us ten gigabits per second. Technically, it gives us a little bit more than that, but we say ten gigabits per second, and the distance limitation is 10.
That’s quite a distance between different pieces of equipment. And when we’re using fibre optic cabling, we probably want to have multiple channels being carried simultaneously over that fibre optic cable. We don’t want all of our users to take turns and say, “All right, now it’s your turn to transmit.” Now it’s your turn to transmit, since we’re only carrying one channel across the fibre cable. Now we want to typically have multiple channels, and we can do that using a technology called multiplexing. With multiplexing, we can use different wavelengths of light. The Greek letter lambda you see on screen is used to represent a wavelength of light. And some of the carriers will talk about giving you a certain lambda. They’re talking about giving you a certain wavelength, or a colour of light, if you will, and by having different communication flows, using different colours of light, or, in other words, different wavelengths.
We can keep those different communications flows separate in their own channels without interfering with one another because they’re using different wavelengths. And one method for doing so is known as CWDM, or wavelength division. Multiplexing. And this approach is typically going to support eight channels, although over short distances you can technically get 18 channels out of this. But typically, you’re going to see a maximum of eight channels with coarse wavelength division multiplexing. And each channel’s wavelength has a 20-nanometer separation, so it can go up to a maximum of 80. It is limited to 80 kilometres because amplifiers are not supported. However, if we separate each channel’s wavelength by a smaller amount, and this is going to require more expensive lasers and photo detectors, so this is more expensive, we can cram more channels into a single fibre cable using dense wavelength division multiplexing, or DWDM. Here we can have a maximum of 80 channels, where each channel’s wavelength is separated not by 20 nm but by 4 nm. This can typically transport data over a distance of about 3000 km. That’s a long way. And one of the reasons we can travel such long distances is because of dense wavelength division multiplexing. It does support amplifiers. So that’s the big distinction.
I want you to know about how we can multiplex data on fibre optics. We can have less precise optics and save money, but the tradeoff is that we get fewer channels, typically eight channels at most with wavelength division multiplexing. Or we can have tighter tolerances with our optics. It’s going to be more expensive to do that, but we can get a lot more channels, as we see with the 80-channel DWDM solution. And when we’re doing either one of these, we’ve got an option. We could use one fibre optic strand just to transmit, and then we could receive over that other fibre optic strand. However, to save money on fiber, an option is to use bidirectional wavelength division multiplexing, or bidirectional WDM. Here we can have a single fiberoptic strand carry both the transmission and the reception of a channel. And the way that’s done is instead of giving a channel a single wavelength or a single lambda, we give each channel two lambdas, or in other words, two wavelengths.
One wavelength is used for receiving on that channel, and the other wavelength is for transmitting on that channel. So this will save you on fibre costs. However, the big tradeoff is that you get fewer channels. If you had an 80-channel DWDM solution where you were sending 80 channels on one strand and receiving 80 channels on the other strand, if you went with bidirectional WDM and were doing dense wavelength division multiplexing, now you have 40 channels instead of 80 channels. So you have to weigh in on your design. Is having a reduced number of channels worth having lower fibre costs? And that’s a look at the collection of Ethernet standards. Again, they are not comprehensive, but these are the ones I would like you to memorize. And you might want to do this using flashcards. I would recommend you have physical flashcards or maybe an app that does electronic flashcards, where on one side of the flashcard it lists the standard, like 100 base TX. And on the back, it would have information such as, “What kind of media does this use?” And the answer would be a category five unshielded twisted pair at the very least.
What is the distance limitation? and it would be 100 meters. I would like you to know that kind of information about the different Ethernet standards that we went through. And also from this video, I want you to be able to distinguish between wavelength division multiplexing and less expensive optics. We have a wider separation between our channels, and as a result, we usually only have eight channels max. but we save money. Or we could spend more money and have more exacting tolerances in the manufacturing of the optics. The channels are packed tightly together, hence the name. And that can give us a maximum of 80 channels. So you need to weigh your channel needs against the cost. And then we wrapped up by talking about how to do bidirectional communication on a single fiberoptic strand by giving the transmit and receive portions of a single channel different wavelengths. That’s going to reduce our channel capacity, but it’s going to save us on fiber.
