How To Guides > Application Performance Scores (APS) > How an Application Performance Score is Calculated

How an Application Performance Score is Calculated

The Application Performance Score object defines the application traffic that will be monitored, and which application performance metrics should be evaluated providing application performance thresholds to be used in the evaluation.

For each metric, the observed traffic is compared against the threshold and is classified into one of three categories:

Good — The baseline for the application is good, which indicates that the application is performing within the expected levels (below the threshold). The users should be happy with the performance of the application.
Tolerated — The performance of the application is less than expected, but is still performing within a range that users should be able to tolerate (between the threshold and four times the threshold). The performance is not great, but users should tolerate it.
Frustrated — The application is performing poorly (more than four times the threshold). The users will be frustrated with the performance.

The number of good observations for all metrics with a threshold are totaled and given a full weighting; the number of tolerated observations for all metrics with a threshold are totaled and given a half weighting; and all frustrated observations are given a zero weighting. These weighted totals are summed and divided by the total observations.

aps = 10 * ((1 x number of satisfied samples) + (0.5 x number of tolerated samples) + (0 x number of frustrated samples)) / total samples

E X A M P L E

For HTTP, a threshold is configured for Network Delay as T = 300 msec and a threshold is configured for round-trip time (RTT) as T = 40 msec.

In one 10s period, 11 flows are sampled for HTTP with the following results:

2 flow samples have a network delay of > 1200 ms (frustrated samples)
3 flow samples have a network delay of > 300 ms but < 1200 ms (tolerated samples)
6 flow samples have a network delay of < 300 ms (satisfied samples)
1 flow sample has a RTT of > 40 ms but < 160 ms (tolerated samples)
10 flow samples have a RTT of < 40 ms (satisfied samples)

The APS score is calculated as follows:

aps = 10 * ( 1 * (6 + 10) + 0.5 * (3 + 1) + 0 * 2) / 22 = 8.1