QoS Overview
Page 36 7210 SAS D, E, K OS Quality of Service Guide
converted to an operational CIR should the hardware not support the exact CIR and PIR
combination specified. Refer to the interpretation of the administrative CIR in Adaptation Rule for
Meters on page 40.
Peak Information Rate
The peak information rate (PIR) defines the maximum rate at which packets are allowed to exit the
meter. It does not specify the maximum rate at which packets may enter the meter; this is governed
by the meter's ability to absorb bursts and is defined by its maximum burst size (MBS).
When defining the PIR for a meter, the value specified is the administrative PIR for the meter. The
7210 SAS devices have a number of native rates in hardware that it uses to determine the
operational PIR for the meter. 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
combination specified. Refer to the interpretation of the administrative PIR in Adaptation Rule for
Meters on page 40.
Adaptation Rule for Meters
The adaptation rule provides the QoS provisioning system with the ability to adapt the
administrative rates provisioned for CIR and PIR, to derive the operational rates based on the
underlying capabilities of the hardware. The administrative CIR and PIR rates are translated to
actual operational rates enforced by the hardware meter. The rule provides a constraint, when the
exact rate is not available due to hardware capabilities. The supported constraints are:
• Minimum: Find the next multiple of the hardware step size that is equal to or higher than
the specified rate.
• Maximum: Find the next multiple of the hardware step size that is equal to or less than the
specified rate.
• Closest: Find the next multiple of hardware step size that is closest to the specified rate.
Adaptation Rule for Meters in 7210 SAS-E Devices
Hardware supports rates to be in the multiple of 64 kbps, the system attempts to find the best
operational rate depending on the defined constraint. The supported constraints are:
• Minimum: Find the next multiple of 64 kbps that is equal to or higher than the specified
rate.
• Maximum: Find the next multiple of 64 kbps that is equal to or less than the specified rate.
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