Curs PC si internet cap 8.3 Planning Structured Cabling: Identifying Potential Wiring Closets
8.3 Planning Structured Cabling: Identifying Potential Wiring Closets 8.3.1 Topology as floor plan Instructor Note The first step in locating a wiring closet is to obtain, or create, to-scale floor-plans of the area the network will service. You may use the diagram given in the curriculum. However, you may want to decide the wiring closet location for the actual area of your structured cabling installation project. If floor plan documents are not readily available, it is a worthwhile exercise to have students measure and draw such documents. Many students may show reluctance to drawing; coach them along, show them some drawing tips, and remind them that sketches and drawings are an important part of the networking professional's skill set. Note the standards for Cat 5 horizontal cable run (shown in the graphic) are 3m maximum for workstation cable, 90m maximum for the horizontal cable, and 6m maximum for the patch cord/jumpers -- this gives us the 100m rule. TIA/EIA-568-A specifies that when using an Ethernet star topology, every device that is part of the network must be connected to the hub by a run of horizontal cabling. The central point of the star topology, where the hub is located, is called the wiring closet. It helps to think of the hub as the center point of a circle which has lines of horizontal cabling radiating from it, like spokes from the center of a wheel. In order to determine the location of a wiring closet, begin by drawing a floor plan of the building (approximately to scale), and adding to it all of the devices that will be connected to the network. As you do this, remember that computers are not the only devices that you will want to connect to the network; there are also printers and file servers to consider.When you have completed this process, you should have a floor plan that is similar to the one shown in the Figure . Web Links Cabling Glossary 8.3 Planning Structured Cabling: Identifying Potential Wiring Closets 8.3.2 Selecting potential locations Instructor Note Criteria for selecting potential wiring closet locations are described. The concept of the POP is introduced; emphasize that at least one wiring closet will hopefully be near the POP. A good way to start looking for a potential wiring closet location is to identify secure locations that are close to the POP, that can serve as either the sole wiring closet, or as the MDF, if IDFs are required. The POP is where telecommunications services, provided by the telephone company, connect to the building's communication facilities. It is essential that the hub be located near it, in order to facilitate wide area networking and connection to the Internet. In the floor plan graphic, five potential locations for wiring closets have been selected. They are marked on the graphic as A, B, C, D, and E. Web Links Cabling Glossary 8.3 Planning Structured Cabling: Identifying Potential Wiring Closets 8.3.3 Determining number of wiring closets Instructor Note A procedure for determining the number of wiring closets is described. After you have drawn in all of the devices that are to be connected to your network (floor plan), the next step is to determine how many wiring closets you will need to serve the area covered by the network. You will use your site map to do this. Use your compass to draw circles that represent a radius of 50 m. from each of the potential hub locations. Each of the network devices that you drew on your floor plan should fall within one such circle. However, if each horizontal cabling run can only be 90 m. in length, can you think of a reason why circles with a radius of only 50 m. would be used?After you have drawn the circles, look at the floor plan again. Are there any potential hub locations whose catchment areas substantially overlap? If so, you could probably eliminate one of the hub locations. Are there any potential hub locations whose catchment areas can contain all of the devices that are to be connected to the network? If so, then one of them could probably serve as the wiring closet for the entire building. If you will need more than one hub in order to provide adequate coverage for all of the devices that will be connected to the network, check to see if one of them is closer to the POP than the other(s)? If so, you will probably want to select it to serve as the MDF. Web Links Cabling Glossary 8.3 Planning Structured Cabling: Identifying Potential Wiring Closets 8.3.4 Identification practice Instructor Note Based on the catchment area process, the locations of the wiring closets should be selected. Use the floor plan provided in this lesson. Notice that there are five potential locations for wiring closets indicated on the floor plan - A, B, C, D, and E. Using the scale indicated on the floor plan, set the compass so that it will mark a circle that equals 50 m in diameter. Mark circles for each of the potential wiring closet sites. Then answer the following questions: Do any of the circles overlap? Can any of the potential wiring closet locations be eliminated? Do any of the circles provide coverage for all of the devices that will be connected to the network? Which of the potential wiring closet locations seems to be the best? Are there any circles where only a few of the devices fall outside the catchment area? Which potential wiring closet is closest to the POP? Based on your findings, list the three best possible locations for wiring closets. Based on your findings, how many wiring closets do you believe will be required for this network? What are the advantages and disadvantages of each of the potential wiring close locations shown on the floor plan? Web Links Cabling Glossary
