CHAPTER 6 Performance Monitoring
Mediant 800 SBC | SNMP Reference Guide
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2:
Second last completed interval
When the current interval (Interval 0) completes (reaches 15 minutes), Interval 2 is discarded,
Interval 1 becomes Interval 2, Interval 0 becomes Interval 1, and a new Interval 0 is created.
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The interval’s start time is synchronized with the device’s clock so that the
intervals begin on the hour (e.g., 12:00). If you are using NTP, then it is likely that
the last interval within the first hour after device startup will be cut short to
accommodate for this synchronization.
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Some performance monitoring parameters support a history with more than two
intervals. These include conference calls, trunk-test calls and digit-collect
requests.
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An attribute whose value is -1 means that the attribute isn’t relevant at that point of
time.
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If the device has just started up and the first measuring interval has not elapsed,
intervals 1 and 2 are not applicable and their data values are typically displayed as
"-1" or as empty cells.
The following figure shows an example of a monitored parameter, in this case, the number of
utilized B-channels in a single trunk:
The x-axis is the time within the interval; the y-axis is the number of used channels. The
parameter’s value is a gauge. While the interval index is 0 (i.e., current interval), any GET on
the parameter value will return a y-axis value at that moment. When the interval is complete
(index 1 or 2), the gauge value is no longer relevant and other attributes become relevant such
as the average (area in green divided by the interval length in seconds), which is called time-
based statistics.
The following figure shows an example of the last three intervals. In this example, the device
was powered up at 11:24. The first interval (of 15 minutes) ended at 11:39 and the second
interval (of 15 minutes) ended at 11:54. The current interval (Interval 0) has not completed the
15 minutes. Typically, you would want the measured performance of the last completed
interval (i.e., Interval 1).
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