The type of a queue dictates how it is scheduled relative to other queues at the hardware level. Being able to define the scheduling properties of a queue is important because a single queue allows support for multiple forwarding classes.
The queue type defines the relative priority of the queue and can be configured to expedited (higher priority) or best-effort (lower) priority. However, the instantaneous scheduling priority of a queue changes dynamically depending on its current scheduling rate compared to its operational Committed Information Rate (CIR) and Fair Information Rate (FIR) (see Queue scheduling). Parental virtual schedulers can be defined for the queue using scheduler policies which enforce how the queue interacts for bandwidth with other queues associated with the same scheduler hierarchy (see Scheduler policies).
The queue type of SAP ingress and egress queues, network queue policy queues, and ingress queue group template queues are defined at queue creation time. The queue type of egress queue group template queues and shared-queue policy queues can be modified after the queue has been created.
The default behavior for SAP ingress and egress queues, network queue policy queues, and shared queue policy queues is to automatically choose the expedited or best effort nature of the queue based on the forwarding classes mapped to it. This is achieved by configuring the queue type to auto-expedited. As long as all forwarding classes mapped to the queue are expedited (nc, ef, h1, or h2), the queue is treated as an expedited queue by the hardware schedulers. When any best effort forwarding classes are mapped to the queue (be, af, l1, or l2), the queue is treated as best effort by the hardware schedulers.
The default queue type for ingress queue group template and egress queue group template queues is best-effort.