Configuring a decision policy

Table 15: Decision policy commands
Command	Purpose
application	Associates an application with the decision policy.
l application-model enterprise l application-model multimedia l application-model other l application-model streaming l application-model voice l application-model web	Configures the application model. Options are: l enterprise l multimedia l other l streaming l voice l web For more information on application models, see Details on Application Models. To assign a model to the decision policy, use the set-application-model command.
as-path	Configures the values used by the CNA system to construct a synthetic AS-path for a route not obtained from BGP.
auto-create subnets	Enables and configures automatic creation of subnets.
bgp-community	Assigns a BGP community value to all routes selected route assertions. The only keyword that you can use in Policy Configuration mode is all.
damped-mode	Enables for disables damped mode. When damped mode is enabled, CNA selects a new winner for a subnet only if the current winner is no longer in the winner set.
decision-policy-assignment	Sets the length of time that an automatically assigned decision policy remains in effect. If no measurements are received from any subnets that are associated with this policy for this length of time, then the automatically assigned decision policy expires.
flap-control	Controls how often CNA sends updates to an edge router for subnets associated with the policy.
ignore-measurements	Prevents the CNA decision-maker from recording measurements for specified subnets in the CNA database. This command is designed to prevent health checks (Web hits that you initiate to verify the availability of the CNA system’s USTAT Web server) from skewing CNA-generated reports.
link	Accesses Link Policy Configuration mode. Important: When you access Link Policy Configuration mode, the commands that you enter apply to the link only for those subnets associated with the current decision policy.
load evaluation-interval	Sets a required time interval between load samples used for load optimization. For more information on load optimization, see Chapter 14, WAN Cost and Load Optimization.
load use-threshold-table	Sets usage thresholds and direction of data flow for load optimization. For more information on load optimization, see Chapter 14, WAN Cost and Load Optimization.
min-required-measure	Sets the minimum number of traffic test measurements required before CNA determines a best path for a subnet.
outage-detection active-probe	Sets the number of consecutive active-probe failures required for CNA to detect an outage for a subnet.
outage-detection brownout	Configures the parameters that CNA uses to detect network brownout. A network brownout occurs when application performance is significantly reduced for end users due to network problems such as congestion, packet loss, link or equipment failures, or configuration errors.
outage-detection silence	Sets the time between measurements that is required for CNA to detect an outage for a subnet.
outage-detection total-silence	Sets the parameters that CNA uses to detect that a subnet is totally silent--no measurements recorded for any of its links for a specific period of time.
persistent-hosts	Allow probe failures from hosts to mark a subnet not-rescued
prefer-in-winner-set bgp	Enables consideration of BGP status when CNA selects a performance route from the winner set. When this setting is enabled, the winning link must be at least as good as the BGP-selected route.
perfer-in-winner-set most-reliable	Enables consideration of a link reliability when CNA selects a performance route from the winner set. When this setting is enabled, the winning link must have the best reliability score, which is determined by the frequency that a link moves out of the winner set (for example, a link which rarely moves out of the winner set will tend to have better reliability).
priority	Assigns a priority to the decision policy. When more than one policy is associated with a subnet, the policy with a higher priority value is used. The default value is zero (0). If two policies have equal priority values, CNA chooses the policy based on alphabetical order (except for the global decision policy, which always has the lowest priority). For example, gnomon is chosen before vole).
priority-subnet	Prioritizes all subnets that are associated with the decision policy. When subnets are prioritized, they are processed by CNA decision-maker before non-priority subnets.
reliability half-life	Sets the half-life parameter, which influences link reliability.
reliability tolerance	Sets the tolerance parameter, which influences link reliability.
route-assert-filter	Configures the conditions under which the CNA decision maker asserts routes known to BGP.
set-application-model	Sets which application model CNA uses when making decisions for the decision policy. Options are: l enterprise l other l streaming l voice l multimedia l web If you do not assign an application model to the policy, then the globally set model is used. To set a global application model, enter this command while in Engine command mode. If no application model is set globally, then the default application model, web, is used.
winner-set-width	Sets the acceptable range for preferred-route performance scores. To be in the winner-set (the set of service provider links from which the best performing route will be selected), a route’s performance score must be within this range.

NOTE: Most of these commands are available both globally and for a specific decision policy. When applied globally, they affect all decisions for all subnets. When applied to a specific policy, the parameters are applied only to those subnets associated with the policy, and the policy values override the globally set parameters.

Any parameter not explicitly set in the decision policy assumes the globally set value for that parameter, and any link-specific setting not explicitly set in the decision policy assumes the value that was set for that link at the global level.