Adaptation rule for queues

The adaptation rule provides the QoS provisioning system with the ability to adapt specific CIR and PIR defined administrative rates to the underlying capabilities of the hardware where the queue is created to derive the operational rates. The administrative CIR and PIR rates are translated to actual operational rates enforced by the hardware queue. The rule provides a constraint used when the exact rate is not available as a result of hardware implementation trade-offs.

For the CIR and PIR parameters individually, the system attempts to find the best operational rate, depending on the defined constraint. The supported constraints are:

• minimum

  Find the hardware supported rate that is equal to or higher than the specified rate.

• maximum

  Find the hardware supported rate that is less than or equal to the specified rate.

• closest

  Find the hardware supported rate that is closest to the specified rate.

Depending on the hardware on which the queue is provisioned, the actual operational CIR and PIR settings used by the queue depend on the method the hardware uses to implement and represent the mechanisms that enforce the CIR and PIR rates.

The 7210 SAS uses a single rate step value to define the granularity for both the CIR and PIR rates. The adaptation rule controls the method the system uses to choose the rate step based on the administrative rates defined by the rate command.

Table: Supported hardware rates and CIR/PIR values for 7210 SAS-T and 7210 SAS-Sx/S 1/10GE devices lists the supported hardware rate steps that correspond to the CIR and PIR ranges between 0 and 1 Gb/s on 7210 SAS-T and 7210 SAS-Sx/S 1/10GE devices. Table: Supported hardware rates and CIR/PIR values for 7210 SAS-Mxp lists the supported hardware rate steps that correspond to the CIR and PIR range values between 0 to 1 Gb/s for the 7210 SAS-Mxp. Table: Supported hardware rates for CIR and PIR values for 7210 SAS-R6 and 7210 SAS-R12 lists the supported hardware rate steps that correspond to the CIR and PIR range values between 0 to 1 Gb/s for the 7210 SAS-R6 and 7210 SAS-R12. Table: Supported hardware rates and CIR/PIR values for 10-Gig port for all platforms lists the supported hardware rate steps that correspond to the CIR and PIR ranges between 0 to 10 Gbps on 10-Gig ports on all platforms. Table: Supported hardware rates and CIR/PIR values for 7210 SAS-Sx 10/100GE lists the supported hardware rate steps that correspond to the CIR and PIR range values between 0 to 1 Gb/s for the 7210 SAS-Sx 10/100GE.

To illustrate how the adaptation rule constraints of minimum, maximum, and closest are evaluated in determining the operational CIR or PIR for the 7210 SAS, assume there is a queue where the administrative CIR and PIR values are 90 Kbps and 150 Kbps, respectively.

If the adaptation rule is minimum, the operational CIR and PIR values are 96 Kbps and 152 Kbps respectively, as the native hardware rate is greater than or equal to the administrative CIR and PIR values.

If the adaptation rule is maximum, the operational CIR and PIR values are 88 Kbps and 144 Kbps.

If the adaptation rule is closest, the operational CIR and PIR values are 88 Kbps and 152 Kbps, respectively, as those are the closest matches for the administrative values that are even multiples of the 8 Kbps rate step.