Explain the different approaches to network troubleshooting. Explain how to use

Question

Explain the different approaches to network troubleshooting.

Explain how to use common problem solving tools.

List at a minimum 2 real world scenarios of common issues that would cause you to use troubleshooting tools, detail how you would use these tools to fix the existing issues.

Discuss how to document a network properly, what the benefits of a properly documented network are, and list and describe what elements should be contained in a properly documented network.

Detail a real world scenario that would require a change to network documentation.

Explanation / Answer

Trouble shooting consists of 3 steps:

Different approaches to network troubleshooting are:

1. Bottom-up The bottom-up approach is my personal favorite. As the name implies, start at the bottom—Layer 1, the physical layer—and work your way up to the top layer (application). The physical layer includes the network cable and the network interface card. So if you encounter a broken or disconnected network cable, there's probably no need to do anymore troubleshooting. You must resolve any physical layer problems before moving on. After fixing the problem, check to see if the trouble still exists. If so, move on to troubleshooting the data link layer.

2. Top-down Once again, the name of this methodology implies the approach. With the top-down method, start at the top of the OSI model (i.e., the application layer) and work your way down to the bottom layer (i.e., physical).

3. Divide and conquer This approach involves a little more intuition. With the divide and conquer method, start at whichever layer you best feel is the root cause of the problem. From there, you can go either up or down through the layers.

Common problem solving tools:

Level 1 conceptualization

What is the simplest, most global level of conceptualization of network communication? Let us call this a "level 1" analysis. In this level, there are only three subparts. How does this very simple level of conceptualization help with network problem solving? The first thing is to establish that there is IN FACT a continuous path between yourself and the remote other. Now usually you cannot physically examine the complete path, but a surprisingly high percentage of network problems can be solved by checking whether there is in fact SOME kind of connection as far as you can easily trace it. Many problems with telecommunications are due to the simple fact that you aren't really plugged into a network. "Things work better when they're plugged in."One useful way to narrow down network problems is to try alternatives. In this case, you have two options. First you can try to establish a successful network connection with an alternative remote other. If that works, then that tends to support the conclusion that the problem is with the "remote other", not the network connection. Secondly you can try to establish a successful alternative network connection between yourself and the remote other, then that will identify the connection as being the problem. If the alternative connection does NOT work, then that points to the problem being with the "remote other".

L 2 conceptualization of networks

If the remote other doesn't respond, then there is not much you can do to fix the problem beyond notifying them of the problem and hoping that they can fix it. However if the problem is in the connection between you and the remote other, then you can move to a more detailed conceptualization of networks. Telecommunications is a two way flow of information. At this level, the network system has been represented as three parts: my computer system, the network, and the remote computer system. When you're establishing a connection, there is often a sequence of actions, as each part is activated, starting with the most local and moving outward. For example, often you start up some communication program on the local computer system, which establishes a link to a network and then finally reaches the remote computer system. When the whole system is working correctly, the user doesn't need to know about this flow. However, when things fail, then paying attention to this sequence can be an important diagnosis tool. How far does this startup process proceed before an error message appears? Problem solving can start by focusing on the part in which the connection process gets stuck. Once you have a concept of a system with a set of interconnected parts, then you can proceed with problem solving by checking the connections between these parts. There is a wire that connects your computer system with the network (either a LAN or telephone network). Is that connected? There is also a wire that connects the network with the remote computer, which you may be able to have somebody at the remote computer end check. If the problem is not in the connections, you can narrow down the problem by swapping equivalent parts. Guided by the "flow diagnosis" described above, you can try replacing the suspect part with an "equivalent" part. You can try a different local computer system with the same network to the same remote other. Or you can try a different network with the same local computer to the same remote other. Or you can try the same local computer with the same network to a different computer used by the remote other. Suppose that you determine by this "swap equivalent parts" action that one of these subparts are the likely cause of the problem. What then? Well, at this point you can call in an expert, directing him or her toward the problematic part. Or you can continue your network problem solving process, moving to a more detailed level of conceptualization.

L 3 conceptualization of networks

Each level of conceptualization consists of a set of subparts, interrelated in ways that represent the structure of the overall concept. At that level, the subpart is a "black box", defined only in terms of its functions with no internal structure (Miyake, 1986). As we proceed to more detailed levels, the subpart itself is structurally represented by a set of interrelated sub-subparts. Thus at the next level of conceptualization of networks, each of the subparts from level 2 can be conceptualized in more detail (Levin & Miyake, 1996). Even though this level of analysis is only slightly more detailed than the previous level, it does highlight the special hardware associated with connecting the local computer with the network. There is the local network interface box (a modem or an Ethernet box or ...) that is either built into the local computer or is connected to a port on the computer. And there is a network jack (either a phone jack or another kind of network jack), often the only easily visible part of the network to the typical network user. At each more detailed level of analysis, there are more connections to check. At this level, there is the connection between the computer and the network box, the connection between the network box and the network jack, the connection between the network jack and the rest of the network, etc. Let's take the first of these as an example: Is there a connection between the computer and the network box? This can be checked in two ways. First, is there a physical connection? Is there a wire that goes from the computer to the network box. Secondly, is there a functioning connection? Can you issue commands to the network box successfully? For example, if the network box is a modem, then you can use a simple communications application to issue a simple "AT" command. Do you get "OK" back? If so, then there is a functioning connection between the computer and the modem. You can then move on to check the next connection. Is there a physical wire that goes from the network box to a network jack? If so, then you can again try to check the functionality of the connection. If the network box is a modem, if you issue an "ATD" command, do you hear a dial tone? If so, then you have verified both of the next two connections, the one from the modem to the phone jack, and the one from the phone jack to the rest of the telephone network.

L 4 conceptualization of networks and beyond

As may now be apparent, there are conceptualizations of the network at more and more specific levels of analysis, where each component at a given level is represented by an interacting set of subcomponents at the next more detailed level. For many problem solving purposes, however, these first few levels are sufficient to either solve network problems or to narrow down the problem either to fix the faulty component or to allow it to be permanently replaced by a functional component. As has been shown by other research on expert problem solvers, this strategy of starting with a general level of conceptualization and then moving progressively to more and more specific levels allows the problem solving to follow a systematic plan, rather than to unsystematically examine the large number of possible problem areas presented at a detailed level of conceptualization. Even if the network problem is not solving, this "top-down" strategy can often progress far enough to eliminate some of the possible problem areas, making it easier to turn the problem over to someone else to solve.

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