User's Manual

4 Summary 7
7signal Ltd, Panuntie 6, FI-00620 HELSINKI, FINLAND, [phone], [e-mail], www.7signal.com
7signal Sapphire Loupe User Guide Release 3.1
4 SUMMARY
4.1 SLA Compliance KPI
To summarize the health of the network element, Loupe analyses multiple KPIs and based on
that computes one single value that is called the ‘SLA Compliance KPI’. The network element
may be either an access point or a link. There has to be a SLA group defined and bound to the
network element.
The measurement value calculates a geometric average of all the selected KPIs in the SLA
group. As such, this KPI does not provide any tools for analysis but it is rather to point out the
need for analysis for the network elements that do not fulfill the quality expectations.
SLA compliance is expressed in %
 100% means that all individual selected metrics met the set target level during the
calculation period
 Compliance may be calculated for hourly or daily averages
Geometric average is used in SLA compliancy calculation (NOTE: different than arithmetic
average)
 Key difference is that if one element fails completely (goes to 0), average gives 0 for
that time.
 This enables detecting full failure to meet completely any single element in the one
compliance metric.
The geometric mean, in mathematics, is a type of mean or average, which
indicates the central tendency or typical value of a set of numbers. It is similar to
the arithmetic mean, which is what most people think of with the word "average",
except that the numbers are multiplied and then the nth root (where n is the
count of numbers in the set) of the resulting product is taken.
For instance, the geometric mean of two numbers, say 2 and 8, is just the square
root of their product; that is
2
√2 × 8 = 4. As another example, the geometric mean
of the three numbers 4, 1, and 1/32 is the cube root of their product (1/8), which
is 1/2; that is
3
√4 × 1 × 1/32 = ½ .
Source: Wikipedia