7.2. Threshold values and types

Every threshold has a current value, which is displayed by the threshold indicator . The value ranges from 0 - 100%, and the position of the bar in the indicator shows this value. In addition, as the threshold value exceeds predefined points, the colour of the indicator will change. If the threshold is normal, then the indicator is shown in green. As its value reaches 70%, then the threshold turns marginal, and is shown in yellow. At 90%, the threshold is critical, which is indicated by red.

The value of the threshold is defined by two factors: the trigger, and how long the threshold must have triggered for. For example, for the errors threshold, you might consider that the trigger is 5 errors per second. The duration might be 4 out of the previous 10 minutes. If the number of errors per second was 5 or more, in at least 4 out of the previous 10 minutes, then the threshold value would be 100%. The percent value is a combination of how long the trigger was exceeded for, relative to the configured setting, and how close the parameter being monitored was to the trigger.

To make it easier to find interfaces which have exceeded thresholds, the value of the threshold propagates up from a switch interface to the overall threshold value for the switch, and then from there to the overall threshold value for the network as a whole. The maximum threshold value propagates up, so that the overall value for a switch is the largest of the values for each of its interfaces.

Thresholds can be set on six different parameters:

Utilization
The percent utilization of an interface.
Unicasts
The number of unicast frames per second.
Broadcasts
The number of broadcast frames per second.
Multicasts
The number of layer 2 multicasts per second.
Errors
The number of errored frames per second.
Discards
The number of discarded frames per second.

When viewing the threshold table, you can click on any threshold indicator, to drill-down further and determine the cause of the threshold violation. If you click on a switch threshold, then the thresholds for all the interfaces in that switch will be displayed in the table. If you click on an interface threshold, then sFlowTrend-Pro will jump to the charts for that interface, to give a view of the traffic seen on that interface. The traffic view selected is smart, so that the traffic highlighted will be related to the type of threshold clicked on (eg, if you click on the errors threshold for an interface, the Interface counters chart will be displayed with the errors/s trend selected).