Traffic Policing, Traffic Shaping, And Line Rate Overview; Traffic Evaluation And The Token Bucket - H3C S5120-EI Series Operation Manual

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Traffic Policing, Traffic Shaping,and Line Rate
Configuration
When configuring traffic classification, traffic policing, traffic shaping, and line rate, go to these section
for information you are interested in:

Traffic Policing, Traffic Shaping, and Line Rate Overview

Traffic Evaluation and the Token Bucket

CAR/GTS/Line Rate Configuration
Displaying Line Rate
Traffic Policing, Traffic Shaping, and Line Rate Overview
If the traffic from users is not limited, a large amount of continuous burst packets will result in worse
network congestion. The traffic of users must be limited in order to make better use of the limited
network resources and provide better service for more users. For example, if a traffic flow obtains only
the resources committed to it within a certain period of time, network congestion due to excessive burst
traffic can be avoided.
Traffic policing and traffic shaping are traffic control policies for limiting traffic and resource usage
by supervising the traffic. The prerequisite for traffic policing and traffic shaping is to determine
whether or not the traffic exceeds the set threshold. Traffic control policies are adopted only when
the traffic exceeds the set threshold. Generally, token bucket is used for evaluating traffic.
The line rate of a physical interface specifies the maximum rate for forwarding packets. Line rate
also uses token buckets for traffic control.
Traffic Evaluation and the 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.
Evaluating traffic with the token bucket
The evaluation for the traffic specification is based on whether the number of tokens in the bucket can
meet the need of packet forwarding. 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.
When the token bucket evaluates the traffic, its parameter configurations include:
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).
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.
An evaluation is performed on the arrival of each packet. In each evaluation, if the bucket has enough
tokens for use, the traffic is controlled within the specification and a number of tokens equivalent to the
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