Huawei v200r001 user manual Introduction to Traffic Policing, Features of Token Bucket

User Manual - Configuration Guide (Volume 3)	Chapter 2
Versatile Routing Platform	Traffic Classification and Policing

2.1.2 Introduction to Traffic Policing

For ISP (Internet Service Provider), it is necessary to control the load and traffic imported into the network by the user. For the Intranet, traffic controlling of some applications will also prove an effective means to control the network state.

The typical function of the Traffic Policing is to supervise the specification of the imported traffic and confine it to a committed range. If the packet traffic is oversized on a connection point, under the Traffic Policing, some packets will be dropped or precedence of the packets will be reset (i.e., confine HTTP packet to less than 50% of the network bandwidth). Therefore, the network resource and carrier’s interest is protected from damage.

One example of Traffic Policing is CAR (Committed Access Rate). CAR is widely used for monitoring and classifying the traffic entering the network of ISP (CAR is so well known as to be the second name for Traffic Policing). CAR predefines monitoring actions according to the different evaluation results of the traffic. These actions include:

zForward. Forward the packet with the evaluation “conforming”.

zDrop. Drop the packet that does not conform to the traffic rule.

zLower the precedence level and forward. Mark the packet evaluated as “partly conforming” with lower precedence and forward it.

zEnter the monitoring of next level. Traffic Policing can be divided into multiple levels and each level focuses on more specific objects.

Traffic Policing adopts Token Bucket algorithm, as shown in Figure QC-2-1.each type of service has a corresponding number of Tokens. The Token is sent out at the specified speed. If the user service arriving speed is greater than the Token sending speed, actions need to be taken towards these service data which exceed the prescribed speed (for example, these data can be marked and forwarded only when there is no congestion. When congestion occurs in the network, these data will be dropped first.). these packets can also be dropped at the beginning. The specific method depends on the protocols and rules adopted between the carrier and the user.

I. Features of Token Bucket

Token Bucket can be seen as a vessel with limited capacity containing Tokens. The system puts Tokens into Token Bucket at a specified speed. when the Bucket is full, extra Token will overflow and the number of Tokens inside the Bucket will stop increasing.

Put Token into Token Bucket at specified speed

Classify

Packet to be	Token Bucket
transmitted
	Drop

Forward

Figure QC-2-1Packet classification and traffic policing

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