Week 4: Day 011 - Cabling/Topology #2

Last class, I spent all class-time installing Linux into all the computers in the lab. Fortunately my peer and I were able to install it on all of them in time. Today, I will continue with the Cabling/Topology, but the rest of the chapter is really just about Cabling, as a note.

So let's start with talking about the coaxial cable. This cable is a "central conductor wire" as characterized in the textbook. The cable is literally just a bunch of shielding (metal shields) so data can travel safely without being interrupted by EMI (Electromagnetic Interference.) To be honest, anything that runs on electricity can interrupt the data transfer (ex: printers, fans, fridges.) Unfortunately, the NIC's would misinterpret the signals, which ends up shutting down the network. Referring back to the topologies, the Early-Bus topology networks would often use coax cables. However, nowadays it's simply used for cable modems in connecting to its ISP (Internet Service Provider) and connecting TV's and to Satellite Receivers or Cable Boxes. The head of the cable has an "F-Connector" used for screwing on to keep a secure connection. The more dominantly used cable, today, is the RG-6 (and almost never the RG-59.) These cables each have an RG (Radio Grade rating) which are developed by the United States military. But the most important number to look at on the cable is the "Ohm rating" which measures the amount of resistance put on the cable. The ratings are seen on the cables, and RG-6 and RG-59 both have 75 Ohms. Sometimes, you'll need to split a coax cable, and luckily there are coaxial splitters thanks to its popularity in today's world.

Next up, we have the Twisted Pair cables which are usually Shielded or not. These cables are the most common types used in networks. The cabling is made up of several wires which are twisted around each other. The STP (Shielded Twisted Pair) is exactly what is said in the name. It's a twisted pair surrounded by shielding, once again protecting it from EMI. These cables are surprisingly rare as there isn't a lot of need for shielding. A situation in which it is needed, is obviously when there is a lot of electronic disruptions and signals being thrown around the room. Now the UTP (Unshielded Twisted Pair) is the most common type of network cabling used. This cable is much cheaper than than the STP, but you must be careful for interference when installing the cable. Thankfully, the UTP cable provides a cheap and efficient way to run cable networks, but it's not exclusive to just cable networks. Other tech such as telephones use the same type of cabling. Sometimes this can confuse, because you may find the same set of cables, for those two different uses. However, to differentiate both, UTP cables have variations. These variations are known as CAT (Category ratings.) They are categorized in MHz (Megahertz) which tells you what the highest frequency is for each cable. What a megahertz is in a nutshell, is the cycles per second in a cable. An example in the textbook was that a 10 MHz cable could handle 10 million bits (10 Mbps) and the maximum amounts of data that can go through the cable per second is known as "bandwidth". Current networks have "bandwidth-efficient encoding schemes" which basically means, they cram as many bits as they can into the same signal, if the cable can handle it. Most networks run at 1000 MHz, and the common cabling used is CAT 5e, which is cheaper than CAT 6. In the future, CAT 6 will probably be used commonly. It's a great idea to be able to look at UTP and being able to figure out its CAT rating. The two places to look is in the box it came in, or on the cable itself. People who have set up telephones in the past, have probably seen RJ (registered jack) connectors used in UTP cables. As a quick note, telephones use RJ-11 connectors while networks use four-pair RJ-45 connectors. This concludes my blog entry, next time I will probably finish off this chapter. Thanks for reading, and tschuss!