Alcatel-Lucent 7450 Quality Of Service Manual page 677

Advanced QoS Policies
min-only]
Context config>qos>adv-config-policy>child-control>offered-measurement
Description
This command is used to increase the measured rate of the policer or queue associated with the policy.
The offered rate (capped by the administrative PIR configured on the queue or policer) is usually used
unaltered by the parent virtual scheduler. The add command allows this measured rate to be increased
by the specified amount or by a percentage of the administrative PIR. The resulting rate will not exceed
the administrative PIR.
The parent scheduler uses the modified measured rate as the available work load for the queue or
policer in determining how much bandwidth the child should receive from the bandwidth distribution
algorithm.
One example of when an increase in the measured offered rate may be desired is when a queue or
policer is handling VOIP traffic. A characteristic of VOIP is the step nature in how traffic is used. Each
call typically adds a certain maximum amount to the overall load. By using the add command, the
bandwidth required for the next added call may be included in the current measured rate. This allows
the virtual scheduler to allocate sufficient bandwidth to the queue or policer so that when the call is
made the scheduling algorithm does not need to run to increase the bandwidth.
A side effect of increasing the measured offered rate is that if the extra bandwidth is allocated by the
virtual scheduler, the available bandwidth to lower priority queues or policers is diminished even
though the extra allocated bandwidth may not be in use. If this is the case, the effect will be seen as an
underrun in the aggregate output of the virtual scheduler.
If the add 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.
Except for the overall cap on the offered input into the virtual scheduler, the child's administrative PIR
has no effect on the calculated increase if an explicit rate is specified.
If the child's administrative PIR is modified while a percent based add is in effect, the system
automatically uses the new relative increase value the next time the child's offered rate is determined.
When the add command is not specified or removed, the child's offered rate used by the child's virtual
scheduler is not increased.
The no form of this command is used to remove an offered rate increase from all child policers and
queues associated with the policy.
Quality of Service Guide 679