37• Peak information rate (PIR)—Rate at which tokens are put into bucket E, which specifies the averagepacket transmission or forwarding rate allowed by bucket E.• Excess burst size (EBS)—Size of bucket E, which specifies the transient burst of traffic that bucket Ecan forward.CBS is implemented with bucket C, and EBS with bucket E. In each evaluation, packets are measuredagainst the following bucket scenarios:• If bucket C has enough tokens, packets are colored green.• If bucket C does not have enough tokens but bucket E has enough tokens, packets are coloredyellow.• If neither bucket C nor bucket E has sufficient tokens, packets are colored red.Traffic policingIMPORTANT:The S5120-EI switch supports policing only the incoming traffic.A typical application of traffic policing is to supervise the specification of certain traffic entering anetwork and limit it within a reasonable range, or to "discipline" the extra traffic to prevent aggressiveuse of network resources by a certain application. For example, you can limit bandwidth for HTTPpackets to less than 50% of the total. If the traffic of a certain session exceeds the limit, traffic policing candrop the packets or reset the IP precedence of the packets. Figure 9 shows an example of policingoutbound traffic on an interface.Figure 9 Traffic policingTraffic policing is widely used in policing traffic entering the networks of internet service providers (ISPs).It can classify the policed traffic and take pre-defined policing actions on each packet depending on theevaluation result:• Forwarding the packet if the evaluation result is "conforming"• Dropping the packet if the evaluation result is "excess"• Forwarding the packet with its precedence, which can be DSCP precedence, re-marked if theevaluation result is "conforming"
