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QoS Overview
Peak Information Rate
The peak information rate (PIR) defines the maximum rate at which packets are allowed to exit the
queue. It does not specify the maximum rate at which packets may enter the queue; this is
governed by the queue's ability to absorb bursts. The actual transmission rate of a egress queue
depends on more than just its PIR. Each queue is competing for transmission bandwidth with other
queues. Each queue's PIR, CIR and the relative priority and/or weight of the scheduler serving the
queue, all combine to affect a queue's ability to transmit packets.
The PIR is provisioned on service egress queues within service egress QoS policies.
The PIR for network queues are defined within network queue policies based on the forwarding
class. The PIR for the queues is specified as a percentage of the network interface bandwidth.
When defining the PIR for a queue, the value specified is the administrative 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 CIR and PIR values specified. The interpretation of the
administrative PIR is discussed below in
Page 40
7210 SAS-X and 7210 SAS-R6 OS Quality of Service Guide
Adaptation Rulefor Queues on page 41
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