Operation Manual – QoS-QoS ProfileH3C S5600 Series Ethernet Switches Chapter 1 QoS Configuration1-11TokenbucketDropPacketclassificationPackets to be sentthrough this portContinueto sendPut tokens in the bucket at theset rateFigure 1-5 Evaluate the traffic with the token bucketII. Evaluating the traffic with the token bucketWhen token bucket is used for traffic evaluation, the number of the tokens in the tokenbucket determines the amount of the packets that can be forwarded. If the number oftokens in the bucket is enough to forward the packets, the traffic is conforming to thespecification; otherwise, the traffic is nonconforming or excess.Parameters concerning token bucket 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.One evaluation is performed on each arriving packet. In each evaluation, if the numberof tokens in the bucket is enough, the traffic is conforming to the specification and youmust take away some tokens whose number is corresponding to the packet forwardingauthority; if the number of tokens in the bucket is not enough, it means that too manytokens have been used and the traffic is excess.III. Traffic policingThe typical application of traffic policing is to supervise specific traffic into the networkand limit it to a reasonable range, or to "discipline" the extra traffic. In this way, thenetwork resources and the interests of the operators are protected. For example, youcan limit HTTP packets to be within 50% of the network bandwidth. If the traffic of acertain connection is excess, traffic policing can choose to drop the packets or to resetthe priority of the packets.
