Network design software

The single-rate three-color marker/policer was a significant improvement for policers, in that it made allowance for temporary traffic bursts (as long as the overall average transmitted rate was equal to or below the CIR) and network design software. However, the variation in the number of accumulated excess burst credits could cause a degree of unpredictability in traffic flows. To improve on this, a two-rate three-color marker/policer was defined in RFC 2698. This policer addresses the peak information rate (PIR), which is unpredictable in the RFC 2697 model. Furthermore, the two-rate three-color marker/policer allows for a sustainable excess burst (negating the need to accumulate credits to accommodate temporary bursts) and allows for different actions for the traffic exceeding the different burst values

The two-rate three-color policer also uses an algorithm with two token buckets, but the logic varies slightly. Instead of transferring unused tokens from one bucket to another, this policer has two separate buckets that are filled each second with two separate token rates. The first bucket is filled with the PIR number of tokens and the second bucket is filled with the CIR number of tokens. In this model, the Be works the same as the Bc, except for the PBS bucket (not the CBS bucket). This means that Be represents the peak limit of traffic that can be sent during a subsecond interval.