Dual Rate Three Color Policer Token Removal Criteria
When employing Dual Rate Three Color (DRTC) policers, it is important to understand when tokens are removed, and from which buckets, and when they are not.
The DRTC policer employs two token buckets, the Committed Information Rate (CIR) bucket and the Peak Information Rate (PIR) bucket, to categorize traffic into three types: conforming, exceeding, and violating.
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Conforming Packets: These packets are within the CIR, and they remove tokens from both the CIR and PIR buckets. Traffic at this level adheres to the guaranteed rate the network can manage without any performance degradation.
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Exceeding Packets: These packets surpass the CIR but remain under the PIR. Exceeding packets only remove tokens from the PIR bucket, as they are managed as allowable bursts without affecting the overall committed rate. Removing tokens from the CIR bucket would mistakenly classify these packets as conforming, potentially degrading network performance by incorrectly signaling available capacity.
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Violating Packets: Such packets exceed the limits of the PIR bucket as well, and thus, do not remove tokens from either bucket. Violation indicates that traffic should be managed to prevent saturation and performance issues.
The design ensures that packets exceeding the CIR do not misuse the token allocation meant for conforming traffic. This separation prevents unforeseen depletion of the CIR bucket, thereby maintaining accurate traffic classification and quality of service. The DRTC policer efficiently handles traffic spikes while preserving the network's intended throughput and performance guarantees.
Links
https://networklessons.com/quality-of-service/qos-traffic-policing-explained/
https://networklessons.com/quality-of-service/policing-configuration-example