Alcatel-Lucent 7450 Quality Of Service Manual page 684

Advanced QoS Policy Command Reference
Context config>qos>adv-config-policy>child-control
Description
This command modifies or controls the bandwidth distribution phase of the parent virtual scheduler.
This command edits the parameters that control the child given bandwidth for all policers and queues
associated with the policy.
above-offered-cap
Syntax [no] above-offered-cap {percent percent-of-admin-pir | rate rate-in-kilobits-per-second}
Context config>qos>adv-config-policy>child-control>bandwidth-distribution
Description This command is used to limit the operationally configured shaping or policing rate on the child
associated with the policy. After the parent virtual scheduler or policer control policy determines the
appropriate rate for a given child a separate operation decides the actual PIR that should be configured
for that child. When the parent determines that the distributed rate is equal to or less than the child's
offered rate, the configured operational PIR will be equal to that determined rate. But when the parent
determines that the child's offered rate is less than the available bandwidth the child could consume,
the operational PIR may be set to a value larger than the distributed bandwidth. This extra rate is not
currently used by the child since the offered rate is less. The system provides this extra bandwidth in
case the child's offered rate increases before the next sampling interval is complete in order to mitigate
the periodic nature of the child's operational PIR adjustments. The increase in the offered rate is not
subtracted from the parent's remaining distribution bandwidth for lower priority children, only the
determined rate is considered consumed by the parent virtual scheduler or policer control policy
instance. The actual operationally configured PIR will never be greater than the child's
administratively defined PIR.
This 'fair share' PIR configuration behavior may result in the sum of the children's PIRs exceeding
the aggregate rate of the parent. If this behavior violates the downstream QoS requirements, the above-
offered-cap command may be used to minimize or eliminate the increase in the child's configured PIR.
If the above-offered-cap command is used with a percent based value, the increase is a function of the
configured PIR value on the policer or queue. In this case, care should be taken that the child is either
configured with an explicit PIR rate (other than max) or the child's administrative PIR is defined using
the percent-rate command with the local parameter enabled if an explicit value is not desired. When a
maximum PIR is in use on the child, the system attempts to interpret the maximum child forwarding
rate. This rate could be very large if the child is associated with multiple ingress or egress ports.
If the child's administrative PIR is modified while a percent based above-offered-cap is in effect, the
system automatically uses the new relative limit value the next time the child's operational PIR is
distributed.
When this command is not specified or removed, the child's operational 'fair share' operational PIR
may be configured up to the child's administrative PIR based on the actual parental bandwidth
available at the child's priority level.
The no form of this command is used to remove a fair share operational PIR rate increase limit from
all child policers and queues associated with the policy.
686 Quality of Service Guide