The committed information rate (CIR) for a queue performs two distinct functions:
Minimum bandwidth guarantees
Queue’s CIR setting provides the bandwidth that is provided to this queue as compared to other queues on the port competing for a share of the available link bandwidth. The queue CIR does not necessarily guarantee bandwidth in all scenarios and also depends on factors such as CIR over subscription and link port bandwidth capacity. For each packet in a queue, the CIR is checked with the current transmission rate of the queue. If the current rate is at or below the CIR threshold, the queue is considered in-profile. If the current rate is above the threshold, the queue is considered out-of-profile. The in-profile and out-profile state of queue is linked to scheduler prioritizing behavior as discussed below.
Scheduler queue priority metric
The scheduler serving a group of queues prioritizes individual queues based on their current CIR and PIR states. Queues operating below their CIR are always served before those queues operating at or above their CIR. Also see information about schedulers to know the scheduler behavior on different 7210 SAS platforms.
The in-profile and out-profile state of the ingress queue determines the packet’s final profile state based on the queue CIR, PIR values. The in-profile and out-profile state of the ingress queue also interacts with the scheduler mechanism and provides the minimum and maximum bandwidth guarantees. This is true only for ingress queues and not for egress queues. That is, the in-profile and out-profile state of the egress queue does not change the packets final profile state based on the queue CIR, PIR values. The in-profile and out-profile state of the egress queue only interacts with the scheduler mechanism and provides the minimum and maximum bandwidth guarantees. See Ingress profile assignment for more information.
When defining the CIR for a queue, the value specified is the administrative CIR for the queue. User has some control over how the administrative CIR is converted to an operational CIR should the hardware not support the exact CIR and PIR combination specified. The interpretation of the administrative CIR is discussed below in Adaptation rule for queues.
Although the 7210 SAS is flexible in how the CIR can be configured, there are conventional ranges for the CIR based on the FC of a queue. An egress queue associated with the high-priority class normally has the CIR threshold equal to the PIR rate although the 7210 SAS allows the CIR to be provisioned to any rate below the PIR should this behavior be required.
The CIR of the queue is configurable under the different QoS policies that provide the option to configure the queue parameters; for example, under service ingress and service egress queue policies, access port policies, and network queue policies.