Dynamic policers and queue mappings

Once traffic is processed by the dynamic policers on ingress, the traffic flows through the policer-output-queues shared queues. Traffic through dynamic policers always bypass subscriber queues or policers on ingress that are statically configured in the base QoS policy.

Similar behavior is exhibited when static policers are configured on egress. Traffic outputting dynamic policer is never mapped to another static policer. Instead, such traffic is mapped to the corresponding shared queue in a queue-group. By default, this queue-group is the policer-output-queue group. However, the selection of the queue-group is configurable.

In contrast to the above, traffic processed by dynamic policers can be fed into statically configured subscriber (local) queues on egress. Dynamic policers and subscriber queues are tied through the forwarding-class.

The policer to local queue mapping and inheritance of the forwarding-class is shown. In this example, the mapping of traffic —> forwarding-class in rule 2 (flow 2) depends on the DSCP bits in the traffic flow. If the DSCP value in this traffic flow are different from the explicitly configured DSCP values in the static (base) QoS policy, then traffic is mapped to the default forwarding-class.

Figure: FC inheritance for dynamically instantiated policers on egress