Dual Token Bucket Single Rate Class Based Policing Cont

Cir Pir Bucket

Traffic is conforming, exceeding, or violating

Using a dual token bucket model allows traffic exceeding the normal burst rate (CIR) to be metered as exceeding and traffic that exceeds the excess burst rate to be metered as violating traffic. Different actions can then be applied to the conforming, exceeding, and violating traffic.

This topic describes how traffic can be policed using a dual-rate metering scheme.

Dual-Rate Class-Based Policing

Cisco Qos Token Dual Bucket

Tc: Tokens in CIR bucket Tp: Tokens in PIR bucket

Enforce traffic policing according to two separate rates:

- Committed Information Rate

- Peak Information Rate

Tc: Tokens in CIR bucket Tp: Tokens in PIR bucket

Enforce traffic policing according to two separate rates:

- Committed Information Rate

- Peak Information Rate

With dual-rate metering, traffic rate can be enforced according to two separate rates: CIR and peak information rate (PIR). Before this feature was available, you could meter traffic using a single rate based on the CIR with single or dual buckets. Dual-rate metering supports a higher level of bandwidth management and supports a sustained excess rate based on the PIR.

With dual-rate metering, the PIR token bucket fills at a rate based on the packet arrival rate, and the configured PIR and the CIR token bucket fills at a rate based on the packet arrival rate and the configured CIR.

When a packet arrives, the PIR token bucket is first checked to see if there are enough tokens in the PIR token bucket to send the packet. The violating condition occurs if there are not enough tokens in the PIR token bucket to transmit the packet. If there are enough tokens in the PIR token bucket to send the packet, then the CIR token bucket is checked. The exceeding condition occurs if there are enough tokens in the PIR token bucket to transmit the packet but not enough tokens in the CIR token bucket to transmit the packet. The conforming condition occurs if there are enough tokens in the CIR bucket to transmit the packet.

Dual-rate metering is often configured on interfaces at the edge of a network to police the rate of traffic entering or leaving the network. In the most common configurations, traffic that conforms is sent and traffic that exceeds is sent with a decreased priority or is dropped. Users can change these configuration options to suit their network needs.

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