The Peak Information Rate (PIR) defines the maximum rate at which packets are allowed to exit the queue. The PIR does not specify the maximum rate at which packets may enter the queue; this is governed by the queue's ability to absorb bursts and is defined by its maximum burst size (MBS).
The actual transmission rate of a service queue depends on more than just its PIR. Each queue is competing for transmission bandwidth with other queues. Each queue's PIR, CIR, FIR, and the queue type (see Queue type) all combine to affect a queue's ability to transmit packets, as described in Queue scheduling.
The PIR is provisioned on ingress and egress queues within service ingress and egress QoS policies, network queue policies, ingress and egress queue group templates, and shared queue policies.
When defining the PIR for a queue, the value specified is the administrative PIR for the queue. The router has a number of native rates in hardware that it uses to determine the operational PIR for the queue. The user has some control over how the administrative PIR is converted to an operational PIR should the hardware not support the exact PIR value specified. The interpretation of the administrative PIR is discussed in Adaptation rule.