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Network Media
A Network Medium is the type of cabling used in a network. There are many types of cables used in networks today, although only a few are commonly used. The type of cabling can have an influence on the speed of the network. A Twisted-pair cable has a pair of wires twisted around eachother to reduce the interference. There can be two, four, or even more sets of twisted pairs in a network cable. Twisted-pair cables are usually attached to the network devices with a jack that looks like a telephone modular jack, but a little wider, supporting up to eight wires. The most commonly used jacks are called RJ-11 (6 wires) and RJ-45 (8 wires), depending on the size of the connector and the number of wires inside.
Figure 2 shows the symbol used for a Twisted-Pair line tag.
• A Unshielded Twisted-Pair (UTP) cable is one of the most commonly used network media because it is cheap and easy to work with. • A Shielded Twisted-Pair (STP) cable has the same basic construction as its unshielded cousin, but the entire cable is wrapped in a layer of insulation for protection from interference. The same type of connectors are used with both forms of twisted-pair cables. A Coaxial cable is designed with two conductors, one in the centre surrounded by a layer of insulation, and the second a mesh or foil conductor surrounded the insulation. Outside the mesh is a layer of outer insulation. Because of its reduced electrical impedance, coaxial is capable of faster transmission than twisted-pair cable. Coax is also broadband, supporting several network channels on the same cable.
Figure 3 shows the symbol used for a Coaxial line tag.
• Thick coax is a heavy cable that is used as a network backbone for the bus network. This cable is formally known as Ethernet PVC coax, but is usually called 10BASE5. Because thick coax is so heavy and stiff, it is difficult to work with and is quit expensive. • Thin coax is the most common type used in Ethernet networks. It goes by several names, including Thin Ethernet, 10BASE2, and cheapernet. Formally, thin coax is called RG-58. Thin coax is the same as your television cable. The inner connector can be made of a single solid copper wire or fashioned out of thin strands of wire braided together. Thin coax is quite flexible and has a low impedance, so it is capable of fast throughput rates. It is not difficult to lay out, as it is quite flexible, and it is easy to construct cables with the proper connectors, usually BNC connectors, at each end. Thin coax is broadband, although most local area networks use only a single channel of the cable. A Fibre-optic cable is becoming popular for very high-speed networks (500 Mbits). It is very expensive but capable of supporting many channels at tremendous speed. Fibre-optic cable is almost never used in local area networks, although some large corporations do use it to connect many LAN’s together into a wide area network. The supporting hardware to handle fibre-optic backbones is quite expensive and specialised.
Figure 4 shows the symbol used for a Fibre-optic line tag.
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