H3C Technologies H3C S7500E Series Switches - Manual (Page 54)

5-2
Evaluation is performed for each arriving packet. In each evaluation, if the number of tokens in the
bucket is enough, the traffic conforms to the specification and the corresponding tokens for forwarding
the packet are taken away; if the number of tokens in the bucket is not enough, it means that too many
tokens have been used and the traffic is excessive.
Complicated evaluation
You can set two token buckets, the C bucket and the E bucket, to evaluate traffic in a more
complicated environment and achieve more policing flexibility. For example, traffic policing uses four
parameters:
z CIR: Rate at which tokens are put into the C bucket, that is, the average packet transmission or
forwarding rate allowed by the C bucket.
z CBS: Size of the C bucket, that is, transient burst of traffic that the C bucket can forward.
z Peak information rate (PIR): Rate at which tokens are put into the E bucket, that is, the average
packet transmission or forwarding rate allowed by the E bucket.
z Excess burst size (EBS): Size of the E bucket, that is, transient burst of traffic that the E bucket
can forward.
CBS is implemented with the C bucket and EBS with the E bucket. In each evaluation, packets are
measured against the buckets:
z If the C bucket has enough tokens, packets are colored green.
z If the C bucket does not have enough tokens but the E bucket has enough tokens, packets are
colored yellow.
z If neither the C bucket nor the E bucket has sufficient tokens, packets are colored red.
Traffic Policing
Traffic policing supports policing traffic in the inbound direction and the outbound direction. Thereafter,
the outbound direction is taken for example.
A typical application of traffic policing is to supervise the specification of certain traffic entering a
network and limit it within a reasonable range, or to "discipline" the extra traffic. In this way, the network
resources and the interests of the user are protected. For example, you can limit bandwidth for HTTP
packets to less than 50% of the total. If the traffic of a certain session exceeds the limit, traffic policing
can drop the packets or reset the IP precedence of the packets.