1-8
Protocol Priority Protocol packets carry their own priority. You can modify the priority of a protocol packet to implement
QoS.
Priority Marking The priority marking function is to use ACL rules in traffic classification and reassign the priority for the
packets matching the ACL rules.
Traffic Policing and Traffic Shaping The network will be made more congested by plenty of continuous burst packets if the traffic of each
user is not limited. The traffic of each user must be limited in order to make better use of the limited
network resources and provide better service for more users. For example, a traffic flow can be limited
to get only its committed resources during a time period to avoid network congestion caused by
excessive bursts.
Traffic policing and traffic shaping is each a kind of traffic control policy used to limit the traffic and the
resource occupied by supervising the traffic. The regulation policy is implemented according to the
evaluation result on the premise of knowing whether the traffic exceeds the specification when traffic
policing or traffic shaping is performed. Normally, token bucket is used for traffic evaluation.
Token bucket
The token bucket can be considered as a container with a certain capacity to hold tokens. The system
puts tokens into the bucket at the set rate. When the token bucket is full, the extra tokens will overflow
and the number of tokens in the bucket stops increasing.
Figure 1-5 Evaluate the traffic with the token bucket
Token bucket
Drop
Packet
classification
Packets to be s ent
through this port
Continue to send
Put tokens in the bucket at the set rate