Dirt Roads Versus the DOT
You can spend a long time working around or in the networking arena and not ever need to worry about how structured cabling works. This section gives you a brief glimpse into the world of structured cabling, just so you know what people are talking about if they bring it up.
You can go to the store and buy premade Ethernet UTP cables with RJ-45 connectors on them. You can even buy a hub—and for not a lot of money, typically less than $20. You could then connect a bunch of computers to the hub using the straight-through Ethernet cables, and voil , you have a network, or at least the part that allows the computers to send and receive data. Running your own cabling is quick and easy.
In a real network in a real building, you will not typically get away with stringing cables on top of the carpet, over people's cubicles, and so on. Instead, you should allow the electricians to do their job right, which means that the cables will run either under the floor or inside the ceiling. Also, instead of a single cable from a PC to the hub, the equivalent will be created. First, you install a short cable from the PC to a wall plate. The electrician runs another cable from the back of the wall plate to the wiring closet into a patch panel. Finally, either the electrician or the network engineer connects a cable from the patch panel in the wiring closet to the hub. Together, these cables provide two twisted pair between the PC NIC and the hub. Figure 4-13 shows the major components.
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Figure
4-13
Major Components of a Structured Wiring Plan
Structured wiring allows the electrician to take care of the difficult part of cabling, with a minimum of cost, effort, and clutter, while still making sure that the cabling works correctly. Even though multiple cables are used, the net result of the cabling simply needs to ensure that the correct twisted pairs end up at the right place in the connectors at the endpoints. And the only cables that the people in the offices can see are the short ones between the PC and the wall plate; the rest of the cables are hidden.
Imagine that if instead of structured wiring, the electrician simply ran a single cable from the computer, under the floor, and straight into the hub in the wiring closet. Later, the person in the cubicle decides that she wants her PC on the left side of her desk, and she might discover that the cable is too short. So what does she do? She calls the electrician and asks for another cable to be run.
Of course, the electrician probably isn't going to want to run a new cable from the cubicle to the wiring closet. If he had used structured wiring, he could have run a cable from the wall plate to the patch panel in the wiring closet. A patch panel, sometimes called a wiring panel, provides the electrician a place to connect the actual wires in the cable on one side of the panel. On the other side, receptacles, much like the ones in the wall plate in the cubicle, allow the electrician or network engineer to use a short cable to connect those pairs of wires to some other devices, such as the hub shown in Figure 4-13.
Because the patch panel is located in a well-known place, and because the wall plate in the cubicles does not move, the electrician can do the hard part (running the cables under the floor) once. If the PC in the cubicle needs to be moved farther away from the wall, the PC user can get a slightly longer patch cable. A patch cable is simply a short LAN cable. Likewise, inside the wiring closet, short patch cables can be used to connect from the patch panel to the networking device, such as the hub shown in Figure 4-13.
You can think of structured wiring as the equivalent of having the DOT build your roads versus just using dirt roads. It takes time, planning, effort, and more cost, but in the end, you have a much better road system. With structured wiring, you end up with much better wiring and far less clutter. Furthermore, you can make changes without a lot of effort.
The benefits of structured cabling can be summarized as follows:
Helps minimize the need for running new cables because the distance from each wall plate to the wiring panel can be determined easily
Allows PC installers to run a short patch cable from the wall plate to the PC, without requiring help from the electrician
Allows network engineers to run a short patch cable from the wiring panel to the networking devices, such as a hub
Helps keep the wiring closet more organized