Extreme Networks ExtremeWare XOS 11.1, Manual

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Adding CLEARFlow Rules to ACLs
ExtremeWare XOS 11.1 Concepts Guide
257
The
period <interval>
statement is optional and sets the sampling interval, in seconds. This
statement specifies how often the rule is evaluated by the CLEARFlow agent. If not specified, the
default value is 5 seconds.
The
hysteresis <hysteresis>
statement is optional, and sets a hysteresis value for the threshold.
After the
delta
statement is true, the value of the threshold is adjusted so that a change smaller than
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
delta counter1 >= 100
and
hysteresis 10
,
then the condition would only be true after the delta of the counter reached at least 100. At the time it
became true, the hysteresis value would be subtracted from the threshold. With the threshold now at 90,
the condition would stay true until the delta of the counter became less than 90.
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 difference 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, “CLEARFlow Rule Actions” on page 259 .
See the section, “Delta Rule Type Example” on page 262 , for an example.
Ratio Rule Type
A CLEARFlow ratio rule compares the ratio of two counter values with the threshold value. The
following is the syntax for a CLEARFlow ratio rule:
entry <CLFrulename> {
if { ratio <counterNameA> <counterNameB> REL_OPER <countThreshold> ;
period <interval> ;
min-value <min-value> ;
hysterisis <hysterisis> ;
}
then {
<actions>;
} else {
<actions>;
}
}
The
ratio
statement specifies how to compare the ratio of two counters with its threshold. The value of
<counterNameA>
is divided by the value of
<counterNameB>
, to compute the ratio. That ratio is
compared with the
<countThreshold>
. The
REL_OPER
is selected from the relational operators for
greater than, great than or equal to, less than, or less than or equal to (>, >=, <, <=).
The
period <interval>
statement is optional, and sets the sampling interval, in seconds. This
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>
statement is optional, and sets a hysteresis value for the threshold.
After the
ratio
statement is true, the value of the threshold is adjusted so that a change smaller than