Determining Proper Burst Size for Traffic Policers
This topic covers the following information:
•
Policer Burst Size Limit Overview on page 30
•
Effect of Burst-Size Limit on page 31
•
Two Methods for Calculating Burst-Size Limit on page 32
•
Comparison of the Two Methods on page 32
Policer Burst Size Limit Overview
A policer burst-size limit controls the number of bytes of traffic that can pass unrestricted
through a policed interface when a burst of traffic pushes the average transmit or receive
rate above the configured bandwidth limit. The actual number of bytes of bursty traffic
allowed to pass through a policed interface can vary from zero to the configured burst-size
limit, depending on the overall traffic load.
By configuring a proper burst size, the effect of a lower shaped rate is alleviated. Use the
burst-size-limit
statement to configure the burst size.
NOTE:
If you set the burst-size limit too low, too many packets will be
subjected to rate limiting. If you set the burst-size limit too high, too few
packets will be rate-limited.
Consider these two main factors when determining the burst size to use:
•
The allowed duration of a blast of traffic on the line.
•
The burst size is large enough to handle the maximum transmission unit (MTU) size
of the packets.
The following general guidelines apply to choosing a policer burst-size limit:
•
A burst-size limit should not be set lower than 10 times the MTU of the traffic on the
interface to be policed.
•
The amount of time to allow a burst of traffic at the full line rate of a policed interface
should not be lower than 5 ms.
•
The minimum and maximum values you can specify for a policer burst-size limit
depends on the policer type (two-color or three-color).
BEST PRACTICE:
The preferred method for choosing a burst-size limit is
based on the line rate of the interface on which you apply the policer and the
amount of time you want to allow a burst of traffic at the full line rate.
Copyright © 2016, Juniper Networks, Inc.
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Traffic Policers Feature Guide for EX9200 Switches
Summary of Contents for EX9200 Series
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