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7.5 10-Mbps Configuration Guidelines: Model 2

Finding the Worst-Case Path

You begin the process of checking your network by finding the path in the network with the maximum delay. This is the path with the longest round trip time and largest number of repeaters between two stations (DTEs). In some cases you may decide that you have more than one candidate for worst-case path in your system. If that's the case, identify all the paths through your network that look like they are worst-case. Then do the calculations for each worst-case path you have found. If any path exceeds the limits for round trip timing or interframe gap, then the network system does not pass the test.

You should have a complete and up-to-date map of your network on hand that you can use to find the worst-case path between two DTEs. However, if your system is not well documented then you will have to investigate and map the network yourself. You need to find out what kinds of segments are in use, how long they are, the location of all repeaters, and how the system is laid out. Once you have this information, then you can determine what the maximum path is and what kinds of segments are used in the maximum path.

Once you've found your worst-case path(s), then the next thing you do is make a model of your path using the network model in Figure 7.4. You do this by assigning the segment at one end of your worst-case path to be a left end segment, which leaves a right end segment and possibly one or more middle segments. To help do this, you can draw a sketch of your worst-case path, noting the segment types and lengths. Then simply assign one of the end segments to be the left end, which leaves you with a right end segment. All other segments in the path become middle segments.

Quick Reference Guide to 10-Mbps Multi-Segment Configuration - 09 SEP 95
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