H3C S5820X Series Configuration Manual

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H3C S5820X Series Configuration Manual Manual pdf 51 page image

39A token bucket has the following configurable parameters:• Mean rate at which tokens are put into the bucket, which is the permitted average rate of traffic. Itis usually set to the committed information rate (CIR).• Burst size or the capacity of the token bucket. It is the maximum traffic size permitted in each burst.It is usually set to the committed burst size (CBS). The set burst size must be greater than themaximum packet size.Each arriving packet is evaluated. In each evaluation, if the number of tokens in the bucket is enough, thetraffic conforms to the specification and the tokens for forwarding the packet are taken away; if thenumber of tokens in the bucket is not enough, the traffic is excessive.Complicated evaluationYou can set two token buckets, bucket C and bucket E, to evaluate traffic in a more complicatedenvironment and achieve more policing flexibility. For example, traffic policing uses the followingparameters:• CIR: Rate at which tokens are put into bucket C. It sets the average packet transmission orforwarding rate allowed by bucket C.• CBS: Size of bucket C, which specifies the transient burst of traffic that bucket C can forward.• 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 buckets and colored following these rules:• 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 policingNOTE:Traffic policing polices inbound and outbound traffic. The outbound traffic is taken for example.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. The network resourcesand the interests of the carrier are protected. For example, you can limit bandwidth for HTTP packets toless than 50% of the total. If the traffic of a certain session exceeds the limit, traffic policing can drop thepackets or reset the IP precedence of the packets.