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Understanding Strict-Priority Queues

You use strict-priority queuing and policing as follows:

  • Identify delay-sensitive traffic by configuring a behavior aggregate (BA) or multifield (MF) classifier.

  • Minimize delay by assigning all delay-sensitive packets to the strict-priority queue.

  • Prevent starvation on other queues by configuring a policer that checks the data stream entering the strict-priority queue. The policer defines a lower bound, marks the packets that exceed the lower bound as out-of-profile, and drops the out-of-profile packets if the physical interface is congested. If there is no congestion, the software forwards all packets, including the out-of-profile packets.

  • Optionally, configure another policer that defines an upper bound and drops the packets that exceed the upper bound, regardless of congestion on the physical interface.

To configure strict-priority queuing and prevent starvation of other queues, include the priority strict-high statement at the [edit class-of-service schedulers scheduler-name] hierarchy level and the if-exceeding and then out-of-profile statements at the [edit firewall policer policer-name] hierarchy level: