Alcatel-Lucent 7950, Quality Of Service Manual

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In This Section
Page 572 7950 XRS Quality of Service Guide
Parent Policer Priority and Unfair Sensitive Discard
Thresholds
Priority level bandwidth control is managed on the parent policer through the use of progressively
higher discard thresholds for each in use priority level. Up to eight priority levels are supported
and are individually enabled per parent policer instance based on child policer priority level
association. When multiple child policers are associated with a parent policer priority level, two
separate discard thresholds are maintained for that priority level. A lower “discard-unfair”
threshold ensures that when a child policer has exceeded its FIR rate, its unfair packets are
discarded first (assuming the parent policer’s bucket depth has reached the priority level’s
“discard-unfair” threshold) protecting the priority level’s fair traffic from the priority level’s unfair
traffic.
A second “discard-all” threshold is used to discard all remaining packets associated with the
priority level in the case where higher priority traffic exists and the sum of both the priority level’s
traffic and the higher priority traffic exceeds the parent policer rate. This protects the higher
priority traffic on the parent policer from being discarded due to lower priority traffic. The child
and parent policers operate in an atomic fashion, any conform effect on a child policer's bucket
depth is canceled when the parent policer discards a packet. See
Figure 24 for a description of
policer bucket rate and packet flow interaction with bucket depth. See Figure 25 for a description
of parent policer bucket and priority thresholds.