Description: This is a high level 'smart MIB' object. This object provides a running average of the proportion of the received frames that are forwarded. This value is calculated locally on the agent and so does not require processor bandwidth from the management station or occupy valuable network bandwidth communicating with that station. By default an agent supporting this parameter will exhibit the following characteristics:-

(1) The parameter will be recalculated at approx 60 second intervals

(2) Every calculation period the device will read the value of dot1dTpPortInFrames and dot1dTpPortInDiscards.

(3) The calculation will be performed on the most recent 4 samples as follows:

4 Sum(dot1dTpPortInDiscards(i)/dot1dTpPortInFrames(i)) * 1000/4 i=1

Which gives the percentage * 10 filtered, and then subtracting this from 1000 to give percentage * 10 forwarded.

dot1dTpPortInDiscards(i) is dot1dTpPortInDiscards(i) - dot1dTpPortInDiscards(i-1). dot1dTpPortInFrames(i) is dot1dTpPortInFrames(i) - dot1dTpPortInFrames(i-1).

The value is expressed as a percentage * 10.

A default threshold exists on this average so that if a calculated average exceeds 85% a trap will be sent to the management station. Further traps will not be sent until the average drops to below 50%.

A particular device may provide a means of changing the number of samples, the averaging period, threshold and threshold action if it so wishes.