Extreme Networks ExtremeWare XOS Guide Manual page 258

CLEARFlow
the hysteresis value will not cause the statement to become false. For statements using the REL_OPER >
or >=, the hysteresis value is subtracted from the threshold; for < or <=, the hysteresis value is added to
the threshold.
For example, if the match condition had the clauses
, then the condition would only be true after the ratio of the counters reached at least 5. At the time it
1
became true, the hysteresis value would be subtracted from the threshold. With the threshold now at 4,
the condition would stay true until the ratio of the counters became less than 4.
If the statement becomes false, the threshold is reset to its original value. You would use the hysteresis
value to prevent the rule from vacillating between the true and false states if the ratio between the
counter values is near the threshold. If the hysteresis value is greater than the threshold value, the
hysteresis value will be set to zero.
The action lists will be discussed in the section,
See the section, "Ratio Rule Type Example" on page
Delta-Ratio Rule Type
A CLEARFlow delta-ratio rule is a combination of the delta and ratio rules. The CLEARFlow agent
computes the difference from one sample to the next for each of the two counters. The ratio of the
differences is then compared to the threshold value. The following is the syntax for a CLEARFlow delta-
ratio rule:
entry <CLFrulename>
if { delta-ratio <counterNameA> <counterNameB> REL_OPER <countThreshold> ;
period <interval> ;
min-value <min-value> ;
hysterisis <hysterisis> ;
}
then {
<actions>;
} else {
<actions>;
}
}
The statement specifies how to compare the ratio of the counter differences with its
delta-ratio
threshold. The difference of the sample values of
sample values of
<counterNameB>
The is selected from the relational operators for greater than, great than or equal to, less than,
REL_OPER
or less than or equal to (>, >=, <, <=).
The
period <interval>
statement specifies how often the rule is evaluated by the CLEARFlow agent. If not specified, the
default value is 5 seconds.
The min-value statement is optional, and sets a minimum value for the counters. If either counter is less
than the minimum value, the expression evaluates to false. If not specified, the minimum value is 1.
The
hysteresis <hysteresis>
After the statement is true, the value of the threshold is adjusted so that a change smaller than
ratio
the hysteresis value will not cause the statement to become false. For statements using the REL_OPER >
ExtremeWare XOS 11.1 Concepts Guide
"CLEARFlow Rule Actions" on page
{
<counterNameA>
, to compute the ratio that is compared with the
statement is optional, and sets the sampling interval, in seconds. This
statement is optional, and sets a hysteresis value for the threshold.
ratio counter1 counter2 >= 5
263, for an example.
is divided by the difference of the
and
hysteresis
259.
.
<countThreshold>
258