Alcatel-Lucent 7950 Quality Of Service Manual page 565

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.
Parameters
percent-of-admin-pir — When the percent qualifier is used, the following percent-of-admin-pir parameter
specifies the percentage of the child's administrative PIR that used as the fair share increase limit. The
new operational PIR result is capped by the child's PIR. If a value of 0 or 0.00 is used, the system will
disable the fair share increase function and only configure the actual distribution rate. If a value of 100
or 100.00 is used, the system will interpret this equivalent to executing the no above-offered-cap
command and return the fair-share operation to the default behavior..
Default
Values
rate-in-kilobits-per-second — When the rate qualifier is used, the following rate-in-kilobits-per-second
parameter specifies an explicit number of kilobits-per-second (1000 bits-per-second) that should be
used as the limit to the child's fair share increase to the operational PIR. The new operational PIR result
is capped by the child's PIR. If a value of 0 is used, the system will disable the fair share increase
function and only configure the actual distribution rate.
Default
Values
7950 XRS Quality of Service Guide
None, an increase limit percentage value must be specified when the percent qualifier is
used.
0.00 — 100.00
None, an increase limit rate value must be specified when the rate qualifier is used.
0 — 100,000,000
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