Operation Manual – QoSH3C S3610&S5510 Series Ethernet SwitchesChapter 2 Traffic Classification, TP, and TSConfiguration2-62.3.2 Evaluating the traffic with the token bucketThe evaluation for the traffic specification is based on whether the number of tokens inthe bucket can meet the need of packet forwarding. If the number of tokens in thebucket is enough to forward the packets, the traffic is conforming to the specification;otherwise, the traffic is nonconforming or excess.When the token bucket evaluates the traffic, its parameter configurations include:z Average rate: The rate at which tokens are put into the bucket, namely, thepermitted average rate of the traffic. It is generally set to committed informationrate (CIR).z Burst size: The capacity of the token bucket, namely, the maximum traffic size thatis permitted in each burst. It is generally set to committed burst size (CBS). The setburst size must be greater than the maximum packet length.An evaluation is performed on the arrival of each packet. In each evaluation, if thebucket has enough tokens for use, the traffic is controlled within the specification and anumber of tokens equivalent to the packet forwarding authority must be taken out;otherwise, this means too many tokens have been used — the traffic is in excess of thespecification.2.3.3 Complicated evaluationYou can set two token buckets in order to evaluate more complicated conditions andimplement more flexible regulation policies. For example, TP uses four parameters:z CIRz CBSz Peak information rate (PIR)z Excess burst size (EBS)Two token buckets are used in this evaluation. Their rates of putting tokens into thebuckets are CIR and PIR respectively, and their sizes are CBS and EBS respectively(the two buckets are called C bucket and E bucket respectively for short), representingdifferent permitted burst levels. In each evaluation, you can implement differentregulation policies in different conditions, including “enough tokens in C bucket”,“insufficient tokens in C bucket but enough tokens in E bucket” and “insufficient tokensin both C bucket and E bucket”.2.3.4 TPThe typical application of TP is to supervise the specification of certain traffic into thenetwork and limit it within a reasonable range, or to "discipline" the extra traffic. In thisway, the network resources and the interests of the operators are protected. Forexample, you can limit HTTP packets to be within 50% of the network bandwidth. If the
