H3C S9500 Operation Manual page 17

Operation Manual – QoS
H3C S9500 Series Routing Switches
Figure 2-2 Measuring the traffic with a token bucket
II. Measuring the traffic with Token Bucket
Whether or not the token quantity of the Token Bucket can satisfy the packets
forwarding is the basis for Token Bucket to measure the traffic specification. If enough
tokens are available for forwarding packets, traffic is regarded conforming the
specification (generally, one token is associated to the forwarding ability of one bit),
otherwise, non-conform or excess.
When measuring the traffic with Token Bucket, these parameters are included:
Mean rate: The rate of putting Token into Bucket, i.e. average rate of the
permitting traffic. Generally set as CIR (Committed Information Rate).
Burst size: Token Bucket's capability, i.e. the maximum traffic size of every burst.
Generally, it is set as CBS (Committed Burst Size), and the bursting size must be
greater than the maximum packets size.
A new evaluation will be made when a new packet arrives. If there are enough tokens in
bucket for each evaluation, it shows that traffics are within the bound, and at this time
the amount of tokens appropriate for the packets forwarding rights, need to be taken
out. Otherwise, it shows that too many tokens have been used, and traffic
specifications are exceeded.
III. Complicated evaluation
Two Token Buckets can be configured to evaluate conditions that are more complex
and to implement more flexible regulation policy. For example, traffic policing has four
parameters, as follows:
CIR (Committed information rate)
CBS (Committed burst size)
Chapter 2 Traffic Classification and Traffic
2-3
Shaping Configuration