H3C Technologies H3C SR8800 - Manual (Page 31)

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Configuring traffic shaping and line rate
Traffic shaping overview
If user traffic is not limited, burst traffic will make the network more congested. Therefore it is necessary
to limit user traffic to better utilize the network resources and provide better services for more users. For
example, you can configure a flow to use only the resources committed to it in a certain time range, thus
avoiding network congestion caused by burst traffic.
Generic traffic shaping (GTS) limits the traffic rate and resource use according to traffic specifications.
The prerequisite for GTS is to know whether a traffic flow has exceeded the specification. If yes, proper
traffic control policies are applied. Usually, token buckets evaluate traffic specifications.
Traffic evaluation and token bucket
Token bucket features
A token bucket is analogous to a container holding a certain number of tokens. The system puts tokens
into the bucket at a set rate. When the token bucket is full, the extra tokens will cause the token bucket to
overflow.
Figure 6 Evaluate traffic with the token bucket
Evaluating traffic with the token bucket
The evaluation of traffic specifications is based on whether the number of tokens in the bucket is enough
for forwarding the packets. Generally, one token is associated with a 1-bit forwarding authority. When
a packet of n bits is forwarded, n tokens are taken out of the token bucket. If the number of tokens in the
bucket is enough for forwarding the packets, the traffic conforms to the specification, and is called the
“conforming traffic”. Otherwise, the traffic does not conform to the specification, and is called the “excess
traffic”.