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Averages on Interfaces (Are they really correct)

clucas over 15 years ago

When I eyeball an interface graph it would appear to me that the average is different then what is stated under the graph. I have even exported the data to excel then run my own average and my number comes up to what I would think it would be from eyeballing it. Has anyone else seen this before? I have attached an example

0 mark_wiggans over 15 years ago

The Excel report will be more accurate as compared to the chart values. The report calculates the values directly from the database, where the chart plots the values to the graph with some rounding off which is why you see the small difference. A similar topic was previously discussed here
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0 clucas over 15 years ago in reply to mark_wiggans

1. Is the average calculated using all data or with the top 5% thrown out?
2. Why can’t the graph display the information accurately since it looks at the database?
3. On a daily report using 'report writer' does it represent data equal to the graph of to the raw data?
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0 FormerMember over 15 years ago in reply to clucas

1. the top 5% is included, except for the 95th percentile report
2. It's looking at the database, but it's "bucketing" the data for the sake of the graphs
3. Not sure I understand the question.
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0 clucas over 15 years ago in reply to FormerMember

2. Why would you want to display a graph which is not correct? It just does not look good. I would classify this as a problem.
3. What I am trying to ask is. I run reports of certain interface daily and sent them out to management. There are many times that these reports represent over 100% utilization on an interface, which is the same figure which is displayed on the graph many times. Does a report display the same information as a graph?
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0 FormerMember over 15 years ago in reply to clucas

clucas,
The way NPM calculates utilization is to divide the traffic it sees by the bandwidth. It reads that bandwidth from the device. You can, however, override the device settings, at which point NPM will use the new custom bandwidth settings. It sounds like your bandwidth setting is wrong for some reason. If you go into the settng and adjust it for the actual bandwidth you're seeing, then you should no longer see values over 100%.
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0 Network_Guru over 15 years ago in reply to FormerMember

The text underneath the chart is incorrect. This has been a bug since day one.
The utilization is actually 95th percentile and NOT average.
It would be nice if we could edit out "Average" from this line, as Average and 95th Percentile are two completely different things.
95th percentile is used for billing of WAN services by service providers.
It is the most commonly used figure for calculating circuit capacity.
See also these posts:

Here is how the footer can be removed completely:
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0 clucas over 15 years ago in reply to FormerMember

I checked the settings and it is correctly pulling the interface speed from the device. But currently its not running over the 200MB.
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