Characteristics of Computer Network Media
With the emergence of the Ethernet LAN (Local Area Network) introduced in the early 1970s by Xerox, the telecommunications world has welcomed this newfound gift with open arms. Since communications is such a vital aspect of all businesses these days, proper acquaintance with this marvelous technology can greatly enhance your company's productivity and efficiency. In this paper, we will reflect into the many different characteristics of media that the LANs are based upon and compare/contrast these different medias.
There are basically four types of media used for Local Area Networks. The most commonly used are twisted copper pairs, Coaxial cables, Fiber Optic, and the Wireless technology.
Twisted copper wire, also known, as the common telephone wire is very similar to the wires used in telephone systems. However, the twisted pair wire required for reliable data transmission is of a heavier gauge than the telephone wire. It uses 24 to 26 AWG (American Wire Gauge, www.datapro.com). The purpose of twisting the copper wires together is to minimize the interference between the two adjacent wires. Otherwise, there would be too much line noise to transfer voice or data efficiently. There are two different types of twisted pairs that are used to transmit data. The STP (Shielded Twisted Pair) and the UTP (Unshielded Twisted Pair). Just like it sounds, the STP is a special kind of copper telephone wiring used in some business installations. An outer covering or a shield is added to the twisted pair acting as a ground. This process shields the twisted pair from EMI (Electro-magnetic Interference), which will disturb the data transmission greatly. The UTP is just a twisted pair without the extra shielding. It just relies on the copper twists to protect it from the EMI. The twisted pairs are grades into five different categories by their data carrying ability. The 6th grade is still in the works. (Please refer to the diagram below: www.whatis.com)
Category Maximum data rate Usual application
CAT 1 Less than 1 Mbps Analog voice (plain old telephone service)ISDN Basic Rate InterfaceDoorbell wiring
CAT 2 4 Mbps Mainly used in the IBM Cabling System for Token Ring networks
CAT 3 16 Mbps Voice and data on 10BASE-T Ethernet
CAT 4 20 Mbps Used in 16Mbps Token RingOtherwise not used much
CAT 5 100 Mbps 100 Mbps TPDDI155 Mbps ATM
As you can see, the twisted pairs can range greatly in bandwidth by the different levels of CATs. For a LAN environment, the CAT 2 and above are used because they can transmit greater amounts of data. These generally are used for Token Ring LANs except for the CAT 3, which is only supported by the Ethernet LANs. Most companies who have networks in the offices use twisted pair system to run their LAN. Using the twisted pair media for LANs is very attractive because of its low cost; mainly the UTP setup because it cost much less than the STPs and the STP...