Imagine yourself as a network administrator, responsible for a 2000 user network. This network reaches from California to New York, and some branches over seas. In this situation, anything can, and usually does go wrong, but it would be your job as a system administrator to resolve the problem with it arises as quickly as possible. The last thing you would want is for your boss to call you up, asking why you haven't done anything to fix the 2 major systems that have been down for several hours. How do you explain to him that you didn't even know about it? Would you even want to tell him that? So now, picture yourself in the same situation, only this time, you were using a network monitoring program. Sitting in front of a large screen displaying a map of the world, leaning back gently in your chair. A gentle warning tone sounds, and looking at your display, you see that California is now glowing a soft red in color, in place of the green glow just moments before. You select the state of California, and it zooms in for a closer look. You see a network diagram overview of all the computers your company has within California. Two systems are flashing, with an X on top of them indicating that they are experiencing problems. Tagging the two systems, you press enter, and with a flash, the screen displays all the statistics of the two systems, including anything they might have in common causing the problem. Seeing that both systems are linked to the same card of a network switch, you pick up the phone and give that branch office a call, notifying them not only that they have a problem, but how to fix it as well. .
Early in the days of computers, a central computer (called a mainframe) was connected to a bunch of terminals using a standard copper wire. Not much thought was put into how this was done because there was only one way to do it: they were either connected, or they weren't. If something went wrong with this type of system, it was fairly easy to troubleshoot, the blame almost always fell on the mainframe system.