Cisco ASR 5000 Series Administration Manual page 25

Enhanced Charging Service Overview
Regex ruledefs are ruledefs that contain regex rule expressions. A ruledef can contain both regex and regular
rule expressions.
Regex group-of-ruledefs are group-of-ruledefs that contain regex ruledefs. A group-of-ruledefs can contain
both regex and regular ruledefs.
2. After the regex ruledefs are configured, on the expiry of an internal 30 second timer, building of the regex
engines is triggered.
Note that one regex engine is built per each regex rule expression type.
Just as with first-time or incremental configurations, SessCtrl/SessMgr recovery/reconciliation also triggers the
building of regex engines.
3. The regex engine matches the regex string (specified in the regex expression) against live traffic, and returns all
matching ruledefs.
4. The rule matches are then verified with those configured in the rulebase to determine the best matching rule.
Limitations and Dependencies
This section lists known limitations and restrictions to regex rule matching.
 Changes to ruledefs cause the optimization engines to get updated, hence any changes to ruledefs must be done
with care. Preferably during low load times.
 Addition, modification, and deletion of regex ruledefs will result in rebuilding of regex engines, which is time
consuming and resource intensive. While the engines are being rebuilt, rule-matching based on the old engines
and old configurations may yield inconsistent results.
Addition, modification, and deletion of action priority lines inside the rulebase has no impact on the regex
engines. The regex engines remain intact and the removed action priorities from the rulebase are ignored
during rule matching. Similarly, addition, modification (adding or removing ruledefs from it), or deletion of a
group-of-ruledefs has no impact on regex engines.
 When adding regex ruledefs, use the following guidelines:
 Avoid configuring "xyz*" or "*xyz*" type of regex rule expressions as they are known to consume
 Do not configure rules frequently. Push as much configuration as possible simultaneously so that all the
 Do not configure large number of regex rules as memory utilization will be high depending on the type
 Frequently monitor status of the engine using the
 When deleting ruledefs use the following guidelines:
 Avoid deleting ruledefs at heavy loads, instead remove them from the required rulebases using the
large memory. Instead, configure Aho-Corasick rules using "starts-with xyz" or "contains xyz"
constructs, which comparatively consume less memory. The "starts-with" and "contains" operators
are specially tailored for these types of operations, and work much faster (with lot less memory) than
the corresponding "regex xyz*" or "regex *xyz*" operators. Hence, it is recommended that the
"starts-with" and "contains" approach be preferred.
regex rules are available for engine building at the same time. Frequent configuration changes may
result in infinite loops with wasted memory and CPU cycles.
of regex rules.
| instance <instance> }
instance number.
action priority <action_priority>
Mode. Doing so has no impact on regex building, although it uses additional memory there is no
impact on traffic processing.
show active-charging regex status { all
CLI command in the Exec Mode. Where
CLI command in the ACS Rulebase Configuration
Cisco ASR 5x00 Enhanced Charging Services Administration Guide ▄
Basic Features and Functionality ▀
is the SessMgr
<instance>
no
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