Extreme Networks ExtremeWare XOS Guide Manual page 383

the counters is near the threshold. If the hysteresis value is greater than the threshold value, the
hysteresis value will be set to zero.
In Table 54 is an example of evaluating the CLEAR-Flow delta-ratio expression above multiple times.
Notice that the rule is not triggered at the second evaluation because both counters have not yet reached
the min-value of 100. The rule first triggers at evaluation 4, when ratio of the two counters exceeds 5.
Once the rule is triggered, it remains triggered until the ratio value is less than 4 (the original threshold
minus the hysteresis), at evaluation 6. At evaluation 8, the rule is again triggered when the ratio reaches
5. The rule will remain triggered until the ratio drops below 4.
Table 54: Delta-Ratio Expression Evaluation Example
counter1
Evaluation value
1 110
2 537
3 1478
4 3953
5 6261
6 8574
7 12171
8 17511
See the section, "Delta-Ratio Expression Example" on page
CLEAR-Flow rule using a delta-ratio expression.
Rule-True-Count Expression
A CLEAR-Flow rule-true-count expression compares how many times a CLEAR-Flow rule is true with a
threshold value. One use is to combine multiple rules together into a complex rule. The following is the
syntax for a CLEAR-Flow rule-true-count expression:
rule-true-count <ruleName> REL_OPER <countThreshold> ;
The statement specifies how to compare how many times a CLEAR-Flow rule is true
rule-true-count
with the expression threshold. The
is the value compared with the number of times the rule is true. The
<countThreshold>
selected from the relational operators for greater than, great than or equal to, less than, or less than or
equal to (>, >=, <, <=).
For example, the following delta-ratio expression:
rule-true-count cflow_count_rule_example >= 5 ;
will only be true after the CLEAR-Flow rule cflow_count_rule_example has been true at least five times. If
the rule cflow_count_rule_example becomes true and remains true, and the period for
cflow_count_rule_example is the default five seconds, the rule would have to be true for at least 20
seconds before the rule-true-count expression will become true. If the period of the rule
cflow_count_rule_example is 10 seconds, it will need to be true for at least 40 seconds before the rule-
true_count expression becomes true.
ExtremeWare XOS 11.3 Concepts Guide
counter1 counter2
delta value
N/A 20
427 90
941 325
2475 737
2308 1307
2313 2078
3597 2977
5340 4042
is the name of the CLEAR-Flow rule to monitor and the
<ruleName>
Adding CLEAR-Flow Rules to ACLs
counter2
delta Ratio
N/A N/A
70 6
235 4
412 6
570 4
771 3
899 4
1065 5
392, for a full example of an ACL and a
Rule
triggered?
No
No
No
Yes
Yes
No
No
Yes
is
REL_OPER
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