3.3 Automating Worksheet Computations


3.3 Automating Worksheet Computations

To provide readers with the ability to automate the traffic estimation process, a worksheet template was created for computing the projected activity on an Ethernet network. This template was created using Microsoft's Excel program and can be easily modified for Token Ring and Gigabit Ethernet.

Figure 3.5 illustrates the Traffic Estimation Worksheet template that is available at the indicated Web URL as a Microsoft Excel file named TRAFFIC.XLS in the EXCEL directory. Note that the column labeled "Frame Size in Bytes" is uniformly set to a value of 1526, which represents the maximum length Ethernet frame. Because most activities that have a major effect on a network, such as program loading, file transfers, and Web page surfing, result in most of the frames used to transport the activity flowing as maximum length frames, setting the frame length to 1526, while not fully correct, will provide a very accurate estimate and is much simpler than attempting to precisely estimate the length of each frame. In addition, because we are estimating traffic, it is doubtful if we will ever approach 100 percent accuracy.

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Figure 3.5: The Traffic Estimation Worksheet Excel Template for Ethernet LANs

To complete the worksheet, you need to enter, at a minimum, the number of stations for a workstation class and for each activity performed the message size in Kbytes, the number of frames/message, and the frequency/ hour for the activity. Figure 3.6 illustrates an example of a completed template for five activities performed by a presumed workstation class called Engineers. Note that by entering data for five activities the worksheet automatically computes the resulting bit rate for each activity, the subtotal bps rate for all activities, and the total bit rate for all workstations in the class, the latter placed in the box in the lower-right corner of the spreadsheet. The EXCEL template shown in Figure 3.6 is stored under the filename trafficexample.xls in the directory EXCEL at the Web URL that can be accessed by purchasers of this book.

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Figure 3.6: An Example of a Completed Traffic Estimation Worksheet Excel Template



Enhancing LAN Performance
Enhancing LAN Performance
ISBN: 0849319420
EAN: 2147483647
Year: 2003
Pages: 111
Authors: Gilbert Held

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