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Network Media

Network media is what is used to connect Point A to Point B. Most people think of media as cables, but air is also media for wireless devices.


I will explain several different types of media - Coaxial cable, Unshielded Twisted Pair cable, fiber optic cable, and wireless media (air).


Coaxial Cable
Coaxial cable, also known as "coax", utilizes one wire. There is a copper wire in the middle of the cable that is used for data transmission. Around it, there is an insulator that prevents the copper cable from touching the braided shield layer. If the copper core touched the shield layer, the signal would get scrambled or there could be an electrical short, so the insulator prevents that. The braided metal shield is to keep outside interference to a minimum. The interference, or noise, that occurs from other equipment like lights, motors, or any electrical device, can interfere with the signal in the copper core. The shield conducts the noise as it comes near the cable, and it is grounded. The shield is connected to a ground when you plug the cable in, so the electrical noise gets terminated.


Electricity flows on the outside of the copper wire, so the thickness of the wire makes a difference. You can't send as much electricity through a thinner wire or else it will get hot and catch on fire or melt. If you pass the same amount of electricity through a thicker wire, it won't get hot. This is where standards come in. You want to get the right cable so the electricity can flow correctly. The more data you transmit, the more electricity is sent through the cable. These cables have an extremely low voltage, so they won't catch on fire if you use the wrong one, but the data might not get tranmitted correctly if you use the wrong cable. There are distance limitations on these cables. For example, you could have an RG-58 cable that is up to 185 meters long, but if it were any longer, the signal would start to get weaker and it would become unreadable by the computer or device you want to communicate with.


Thin Ethernet, or RG-58, has a distance limitation of 185 meters. Thick Ethernet, or RG-8 or RG-11, has a distance limitation of 500 meters. ARCNet, or RG-62, has a variable distance limitation.


UTP Cable
UTP stands for Unshielded Twisted Pair. These cables are just copper wire pairs with no shield. Each pair of wires is twisted to prevent interference, or crosstalk. Since there are several wires in the cable, the electrical signal on one wire could interfere with another wire's signal. So each pair is twisted, which forms sort of a force-field around the pair to lessen interference. The more twists per inch on the wire, the more protection it has against interference, and therefore it is better quality. The UTP cables are labeled with a category, or CAT. UTP cables have a distance limitation of 100 meters when sending binary data (not analog data, such as telephone communication).
CAT 1 - your basic cheap telephone wire. It uses 2 pairs of wires.
CAT 2 - also for telephones or alarm systems. It uses 2 pairs of wires.
CAT 3 - higher quality, and you can send data on it - up to 16 Megabits per second (Mbps). It uses 4 pairs of wires. Out of those, only 2 pairs are used (4 wires).
CAT 4 - 20 Mbps, 4 pairs.
CAT 5 - 100 Mbps, 4 pairs, higher quality (more twists per inch).
CAT 6 - 1Gbps (Gigabit per second), 4 pairs, very high quality with several more twists per inch. Also the pairs are twisted around each other.


Fiber Optic Cable
Fiber optic cables use light, therefore almost eliminating interference. Electrical signals and magnetism will not interefere with the light signals inside of a fiber optic cable. The light signals will be produced with either a laser or a light emitting diode (LED). A laser is more powerful and expensive, so it is used for long distance cables, while LEDs are used for shorter distances.


There are two different types of fiber used - single mode and multi mode. The single mode fiber has a smaller diameter than multi mode fiber. It is so small that it is actually more expensive to make than multi mode fiber. Around the fiber is a cladding. The cladding reflects the light along the fiber. With a thinner fiber, there is less room for the light to bounce around, and therefore it can go a longer distance before the light dissipates and the signal gets too weak. Because single mode fiber is more expensive and can go longer distances, it is commonly used in WANs (Wide Area Networks), while multi mode is commongly used in LANs (Local Area Networks).


Wireless
Just as it sounds, wireless networks don't use wires, they use radio frequency. The 3 primary wireless standards are 802.11a, 802.11b, and 802.11g. 802.11 is the IEEE standard for wireless communication.


802.11a uses the 5GHz frequency to communicate. It can communicate at 54Mbps, which is fast for wireless, but it has a short range of 150 feet. 802.11b uses the 2.4GHz frequency to communicate. It can communicate at just 11Mbps, but it has a range of 300 feet. Because it uses the 2.4GHz frequency, you might run into some problems when using a cordless phone or microwave, because many of those products also use the 2.4GHz frequency. 802.11g also uses the 2.4GHz frequency to communicate. It can communicate at 54Mbps and has a range of 300 feet. Even though it uses the same frequency as 802.11b, it is faster because it sends and recieves data differently.


802.11g is backwards-compatible with 802.11b. This means that if you have an 802.11b network, and a laptop with an 802.11g wireless card, it will be able to connect to the network. The 802.11g card will just slow down to 11Mbps (the limit on 802.11b networks).


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Source: www.a1articles.com