3com 5500-ei pwr Instrução De Instalação

 

1-10 

Figure 1-5 Evaluate the traffic with the token bucket 

Token 

bucket

Drop

Packet 

classification

Packets to be sent 

through this port

Continue 

to send

Put tokens in the bucket at the 

set rate

 

 

When token bucket is used for traffic evaluation, the number of the tokens in the token 

bucket determines the amount of the packets that can be forwarded. If the number of 

tokens in the bucket is enough to forward the packets, the traffic is conforming to the 

specification; otherwise, the traffic is nonconforming or excess. 

Parameters concerning token bucket include: 

z 

Average rate: The rate at which tokens are put into the bucket, namely, the permitted 

average rate of the traffic. It is generally set to committed information rate (CIR). 

z 

Burst size: The capacity of the token bucket, namely, the maximum traffic size that is 

permitted in each burst. It is generally set to committed burst size (CBS). The set burst 

size must be greater than the maximum packet length. 

One evaluation is performed on each arriving packet. In each evaluation, if the number of 

tokens in the bucket is enough, the traffic is conforming to the specification and you must 

take away some tokens whose number is corresponding to the packet forwarding authority; 

if the number of tokens in the bucket is not enough, it means that too many tokens have 

been used and the traffic is excess. 

The typical application of traffic policing is to supervise specific traffic into the network and 

limit it to a reasonable range, or to "discipline" the extra traffic. In this way, the network 

resources and the interests of the operators are protected. For example, you can limit 

HTTP packets to be within 50% of the network bandwidth. If the traffic of a certain 

connection is excess, traffic policing can choose to drop the packets or to reset the priority 

of the packets. 

Traffic policing is widely used in policing the traffic into the network of internet service 

providers (ISPs). Traffic policing can identify the policed traffic and perform pre-defined 

policing actions based on different evaluation results. These actions include: