Understanding Ethernet Cables

It binds us. It connects us. It gives us knowledge. It’s omnipresent and omniscient. It’s…

Wi-Fi.

Well.  Sometimes we forget that Wi-Fi signals and connectivity still require a much underappreciated and most needed component –

The Ethernet cable.

Your mobile connectivity has to come from some sort of wireless hub, which is connected to either an Ethernet or fibre-optic cable these days. For this post, we’re looking at the standard Ethernet cable used for VoIP phones, routers, switches, hubs, servers, computers, network printers and more. To the casual user, these cables come in a confusing array of choices.

However, there is, in fact, a difference between all those network cables. They look and any of them will plug into an Ethernet port, but they do have some differences on the inside.

So let’s say you need to get some new cable to setup a small home network, and you walk into a gadget store and say “Hi, I’d like to get some computer cable”.

That’s not going to be helpful. The differences between each type of cable are due to various network standards. Here’s what you need to know about how they’ll affect the speed of your home or work network:

Cat5 – Oldest type and slowest – Category 5 cabling, also known as Cat5, was made to support theoretical speeds of 10-100Mbps (10BASE-T, 100BASE-TX). Since Cat5 is an older type of cabling, you probably won’t see it much in stores, but you may have gotten some with an older router or another networking device. Most Cat5 cables are unshielded, relying on the balanced line twisted pair design and differential signaling for noise rejection. Cat5 has been superseded by the CAT5e (enhanced) specification.

Cat5e – Faster with less interference – Category 5 enhanced cabling is an improvement on Cat5 cabling. It was made to support up to 1000 Mbps gigabit speeds, so in theory, it’s faster than Cat5. It also cuts down on crosstalk, which is the interference you can sometimes get between wires inside the cable. Both of these improvements mean you’re more likely to get a faster, more reliable speed out of Cat5e cabling compared with Cat5. This is the most common cable that is in use today.

More details of a Cat5e cable’s specifications can found here.

Cat6 – Consistent gigabit speeds – Category 6 cabling is the next step up from Cat5e, and includes a few more improvements. It has even stricter specifications when it comes to interference, and is even capable of 10-Gigabit speeds.

It’s used in large networks, small data centers and in a business environment. You probably won’t use these speeds at home, and the extra interference improvements won’t make a huge difference in regular usage, but if you’re purchasing a new cable, you might want to consider Cat6 for future upgradability.

One thing to note with extra shielding, Cat6 cables are slightly thicker and slightly less pliant, meaning they won’t bend around corners or coil as easily as compared with Cat5 cables.

Cat 6a (Augmented) – Server-type cables – These cables are the fastest and most expensive cables available for the highest consistent speeds in server farms, network servers and distributed / parallel computing applications.

All cables are backward compatible, meaning the higher categories can work with the lower categories of Ethernet. An interesting thing to note is that there are other categories of cable, Cat7-8, but they are not recognized by the TIA/EIA and few manufacturers make them.

So Which Should You Use?

It’s important to note that your network speed is different than your internet speed. Chances are, upgrading your cables isn’t going to make a difference in how fast you load that YouTube video. Your ISP speeds are likely to be much slower than your network. But if you are transferring files between computers (i.e. you’re backing up to a NAS) or streaming videos, then using gigabit-compatible hardware will speed up access time, but your router and computer ports should be gigabit-compatible as well, otherwise, the bottle neck is just shifted elsewhere. Also, if you’re running cable throughout your house, you may notice a decrease in speeds if you are using cables longer than 100 meters.

What type of cable are you using?

The printed text on the cable will usually give you some clues. In this example, the similar color arrangement of the cable tells us that the cable is a straight cable.

Straight and crossover cables are wired differently from each other. One way to tell what you have is to look at the order of the coloured wires inside the plastic RJ-45 housing. The RJ-45 connector is the standard type connector used for Ethernet connections compared with the smaller RJ-11 connections used on telephone cords. Crossover cables are less common and are used in computer-to-computer applications. The more common cable will be a straight cable, where you connect a network device (say a router) to your computer or wireless-access points.

What you can do is put both ends of the cable side by side with the connector facing the same way and see if the order of the wires is the same on both ends. If so, then you have a straight cable. If not, then it’s most likely a crossover cable or was wired wrong.

Our cable reads “CAT5E” “TIA/EIA568B” “4STP” “24AWG”, what it means:

  • Cat5e Category 5 Enhanced cable
  • TIA/EIA568B means this cable is compliant to the standards set by Telecommunications Industry Association (TIA) of the Electronic Industries Alliance (EIA) for commercial building cabling, pin/pair assignments for eight-conductor 100-ohm balanced twisted pair cabling. These assignments are named T568B, the latest version is T568C as of 2014, more of this standard here.
  • 4STP means four cables of S = braided shielding (outer layer only), TP = twisted pair. This is a four-wire shielded twisted pair (STP) of wires, more can be read on Ethernet cable construction here.
  • 24AWG denotes how thick the copper wires of the cable are. American wire gauge (AWG) is a standardized gauge system for indicating the diameter of conducting electrical wire and is commonly used among electrical engineers. The rating gives information regarding the resistance of the wire and the allowable current (ampacity) based on plastic insulation. In this case, 24 represents as cross-sectional diameter of 0.51054mm (0.205 mm2) and a copper resistance of 84.22mΩ/m (0.842Ω/metre), which is a typical impedance of 100 ± 15Ω.

Cable health

Ok, now you know a whole lot more about Ethernet cables, you fish out one from the rat’s nest where you’ve stored all the random cables in your house, you find the Ethernet cable and plug it in.

It doesn’t work.

Great, what now? How do you tell if it’s a bad cable?

Wouldn’t it be great to know if the wires inside the cable had broken? Especially if it’s an expensive Cat6 type cable or if the cable is especially long.

We got an RJ-45 network cable tester from Amazon, however, this little gadget isn’t intuitive at all. According to the poorly written manual, the lights will turn on sequentially from 1 to 8 if the tested cable if fully functional. It works sporadically and basically, gives an “OK/NOT OK” binary output by means of a single LED.

Next, we got ourselves RJ-45 punch-down blocks from Amazon, and they were a pain. The clips required pliers to remove and more wires needed to be punched in the teeth before any sort of testing could be done. A real inconvenience.

There must be a better way – so we created a new solution. The easy-to-use RJ-45 Ethernet cable tester for a quick, low-cost, painless way to test your Ethernet cables.

This is as simple as it gets – two RJ-45 receptacles. Plug in your Ethernet cable and use a continuity checker or a Multimeter and you will know if your cable works or is broken.

You can now test the resistances of each point in your cable using your Multi-meter and determine if your cable meets the necessary tolerances. Typical Cat5e cables have a 10ohm/100m conductor resistance, resulting in a 1ohm/10m loop resistance, with tolerances included, you should measure an end-to-end wire resistance of <20 ohms per 100m length, or about 0.2Ω/metre.

Or you could simply do a continuity test to ensure your cables aren’t broken or if there are missing wires. We tested all our Cat5/Cat5e cables, flat, shielded, long and short, in seconds! This nifty gadget was born out of frustration in finding a simple, low-cost means of testing lots of Ethernet cables quickly and easily and our engineers now use it frequently. It’s a must-have for any engineer/technician working with lots of Ethernet cables.

Our cable tester is now available on our distribution partner’s store.

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