Traffic Policing, Traffic Shaping, And Line Rate Overview; Traffic Evaluation And Token Buckets - H3C S5820X Series Configuration Manual

5
Traffic Policing, Traffic Shaping, and Line Rate
Configuration
This chapter includes these sections:

Traffic Policing, Traffic Shaping, and Line Rate Overview

Configuring Traffic Policing
Configuring GTS
Configuring the Line Rate
Displaying and Maintaining Traffic Policing, GTS, and Line Rate
Traffic Policing, Traffic Shaping, and Line Rate Overview
Without limits on user traffic, a network can be overwhelmed very easily. To help assign network
resources such as bandwidth efficiently to improve network performance and hence user satisfaction,
QoS technologies such as traffic policing, traffic shaping, and rate limit were introduced. For example,
you can configure a flow to use only the resources committed to it in a certain time range, thus
avoiding network congestion caused by burst traffic.
Traffic policing and generic traffic shaping (GTS) limit traffic rate and resource usage according to
traffic specifications. Once a particular flow exceeds its specifications, such as bandwidth assigned to
it, it is shaped or policed to ensure that it conforms to the specifications. Generally, token buckets are
used to evaluate traffic specifications.

Traffic Evaluation and Token Buckets

Token bucket features
A token bucket is analogous to a container holding a certain number of tokens. The system puts tokens
into the bucket at a set rate. When the token bucket is full, the extra tokens overflow.
Evaluating traffic with the token bucket
The evaluation of traffic specifications is based on whether the number of tokens in the bucket is
enough to forward packets. Generally, one token is associated with a 1-bit forwarding authority. In
other words, when a packet of n bits is forwarded, n tokens are taken out of the token bucket. If the
number of tokens in the bucket is enough for forwarding the packets, the traffic conforms to the
specification and is called conforming traffic. Otherwise, the traffic does not conform to the
specification and is called excess traffic.
A token bucket has the following configurable parameters:
Mean rate at which tokens are put into the bucket, which is the permitted average rate of traffic. It
is usually set to the committed information rate (CIR).
Burst size or the capacity of the token bucket. It is the maximum traffic size permitted in each burst.
It is usually set to the committed burst size (CBS). The set burst size must be greater than the
maximum packet size.
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