3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 2 Traffic Classification, Policing, and Shaping3Com Corporation2-3out. Otherwise, it shows that too much tokens have been used, and trafficspecifications are exceeded.III. Complicated evaluationTwo Token Buckets can be configured to evaluate conditions that are more complexand to implement more flexible regulation policy. For example, Traffic Policing (TP) hasthree parameters, as follows:z CIR (Committed Information Rate)z CBS (Committed Burst Size)z EBS (Excess Burst Size)It uses two Token Buckets with the token-putting rate of every bucket set as CIR equally,but with different capabilities: CBS and EBS (CBS < EBS, called C Bucket and EBucket), which represents different bursting class permitted. In each evaluation, youmay use different traffic control policies for different situations, such as "C bucket hasenough tokens”; "Tokens of C bucket are deficient, but those of E bucket are enough”;"Tokens of C bucket and E bucket are all deficient”.2.2.2 Traffic PolicingTypically, traffic policing is used to monitor the specification of certain traffic entering thenetwork and keep it within a reasonable bound, or it will make “penalty” on theexceeding traffic so as to protect network resources and profits of carriers. For example,it can restrict HTTP packets to occupy network bandwidth of no more than 50%. Oncefinding the traffic of a connection exceeds, it may drop the packets or reset theprecedence of packets.Traffic policing allows you to define match rules based on IP precedence or DiffServcode point (DSCP). It is widely used by ISP to police the network traffic. TP alsoincludes the traffic classification service for the policed traffics, and depending upon thedifferent evaluation results, it will implement the pre-configured policing actions, whichare described as the following:z Forward: For example, continue to forward the packets evaluated as “conform”.z Drop: for example, dropping the packets evaluated as “not conform”.z Reset precedence and forward: For example, for packets evaluated “partlyconform”, to sign another priority then forward them.z Enter the policing of the next level: Traffic policing can stack gradually with eachclass caring and policing objects that are more specific.2.2.3 Traffic ShapingTraffic shaping is an active way to adjust the traffic output rate. A typical application is tocontrol the output traffic with TP index based upon downstream network nodes.
