Alcatel-Lucent 7750 Configuration Manual page 562

Interfaces
Description This command defines the minimum required separation between each in-use discard threshold maintained
for each parent policer context associated with the policer-control-policy. The min-thresh-separation value
may be overridden on each SAP or sub-profile to which the policy is applied.
The system uses the default or specified min-thresh-separation value in order to determine the minimum
separation required between each of the of the parent policer discard thresholds. The system enforces the
minimum separation based on the following behavior in two ways. The first is determining the size of the
shared-portion for each priority level (when the mbs-contribution command's optional fixed keyword is
not specified):
• When a parent policer instance's priority level has less than two child policers associated, the shared-
portion for the level will be zero.
• When a parent policer instance's priority level has two or more child policers associated, the shared-
portion for the level will be equal to the current value of min-thresh-separation.
The second function the system uses the min-thresh-separation value for is determining the value per pri-
ority level for the fair-portion:
• When a parent policer instance's priority level has no child policers associated, the fair-portion for the
level will be zero.
• When a parent policer instance's priority level has one child policer associated, the fair-portion will be
equal to the maximum of the min-thresh-separation value and the priority level's mbs-contribution
value.
• When a parent policer instance's priority level has two or more child policers associated, the fair-portion
will be equal to the maximum of the following:
–min-thresh-separation value
–The priority level's mbs-contribution value less min-thresh-separation value
When the mbs-contribution command's optional fixed keyword is defined for a priority level within the
policy, the system will treat the defined mbs-contribution value as an explicit definition of the priority
level's MBS. While the system will continue to track child policer associations with the parent policer prior-
ity levels, the association counters will have no effect. Instead the following rules will be used to determine
a fixed priority level's shared-portion and fair-portion:
• If a fixed priority level's mbs-contribution value is set to zero, both the shared-portion and fair-portion
will be set to zero
• If the mbs-contribution value is not set to zero:
–The shared-portion will be set to the current min-thresh-separation value
–The fair-portion will be set to the maximum of the following:
min-thresh-separation value
mbs-contribution value less min-thresh-separation value
Each time the min-thresh-separation value is modified, the thresholds for all instances of the parent policer
created through association with this policer-control-policy are reevaluated except for parent policer
instances that currently have a min-thresh-separation override.
Determining the Correct Value for the Minimum Threshold Separation Value
The minimum value for min-thresh-separation should be set equal to the maximum size packet that will be
handled by the parent policer. This ensures that when a lower priority packet is incrementing the bucket, the
Page 562 7750 SR Interface Configuration Guide