H3C S5100-SI Operation Manual page 403

Traffic policing
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 exceeding
traffic. In this way, the network resources and the interests of the carrier are protected. For
example, you can limit the 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 to
re-mark the priority of the packets.
Traffic policing is widely used for policing traffic entering the network of internet service
providers (ISPs). It can classify the policed traffic and perform pre-defined policing actions
based on different evaluation results. These actions include:
Dropping the nonconforming packets.
Forwarding the conforming packets or nonconforming packets.
Marking the conforming packets or nonconforming packets with 802.1p precedence
and then forwarding the packets.
Marking the conforming packets or nonconforming packets with DSCP values and
forwarding the packets.
Traffic shaping
Traffic shaping provides measures to adjust the rate of outbound traffic actively. A typical
traffic shaping application is to limit the local traffic output rate according to the
downstream traffic policing parameters.
The major difference between traffic shaping and traffic policing is that the packets to be
dropped in traffic policing are cached in a buffer or queue in traffic shaping, as shown in
Figure 1-7. When there are enough tokens in the token bucket, the cached packets are
sent out at an even rate. Traffic shaping may introduce an additional delay while traffic
policing does not.
Figure 1-7 Diagram for traffic shaping
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