3Com Switch 8800 Advanced Software V5 Configuration Guide

834 CHAPTER 61: TRAFFIC CLASSIFICATION AND TRAFFIC SHAPING CONFIGURATION
It uses two token buckets, with the token-putting rate of every bucket set as CIR
and PIR and the capability of every bucket set as CBS and EBS (CBS < EBS, called C
bucket and E bucket), which represents different bursting class permitted. In each
evaluation, you may use different traffic control policies for different situations,
such as "C bucket has enough tokens"; "Tokens of C bucket are deficient, but
those of E bucket are enough"; "Tokens of C bucket and E bucket are all
deficient".
Traffic policing
Typically, traffic policing is used to monitor the specification of certain traffic
entering the network and keep it within a reasonable bound, or it will make
"penalty" on the exceeding traffic so as to protect network resources and profits
of carriers. For example, it can restrict HTTP packets to occupy network bandwidth
of no more than 50%. Once finding the traffic of a connection exceeds, it may
drop the packets or reset the precedence of packets.
Traffic policing allows you to define match rules based on IP precedence or
DiffServ code point (DSCP). It is widely used by ISP to police the network traffic. TP
also includes the traffic classification service for the policed traffics, and depending
upon the different evaluation results, it will implement the pre-configured policing
actions, which are described as the following:
■ Forward: For example, continue to forward the packets evaluated as
"conform".
■ Drop: For example, dropping the packets evaluated as "not conform".
Traffic shaping
Traffic shaping is an active way to adjust the traffic output rate.
The main difference between traffic shaping and traffic policing is: the packets to
be dropped in traffic policing will be stored during traffic shaping - generally they
will be put into buffer or queues, as shown in
Figure 249. Once there are enough
tokens in token bucket, those stored packets will be evenly sent. Another
difference is that traffic shaping may intensify delay, yet traffic policing seldom
does so.