Committed information rate

The committed information rate (CIR) for a queue performs the following functions:

• minimum bandwidth guarantees

  The queue CIR setting provides the bandwidth for the 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 the queue is linked to scheduler prioritizing behavior, as described in the following bullet point.

• 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. See Port scheduler policies for information about the scheduler behavior on different 7210 SAS platforms.

The in-profile and out-profile state of the queue does not change the packets profile state based on the queue CIR or PIR values. The in-profile and out-profile state of the queue interacts with the scheduler mechanism and provides the minimum and maximum bandwidth guarantees.

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 if the hardware does not support the exact CIR and PIR combination specified. See Adaptation rule for queues for information about the interpretation of the administrative CIR.

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 — example under access port policies, network queue policies, and so on.