Juniper EX9200 Series, Features Manual

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Logical Bandwidth Policer
A logical bandwidth policer is a bandwidth policer for which the effective bandwidth limit
is calculated based on the logical interface configured shaping rate. You can apply the
policer as a firewall filter policer only, and the firewall filter must be configured as an
interface-specific filter. When you apply an interface-specific filter to multiple logical
interfaces on supported routing platforms, any
count
or
policer
actions act on the traffic
stream entering or exiting each individual interface, regardless of the sum of traffic on
the multiple interfaces.
Three-Color Policers
The Junos OS supports two types of three-color policers: single-rate and two-rate. The
main difference between a single-rate and a two-rate policer is that the single-rate policer
allows bursts of traffic for short periods, while the two-rate policer allows more sustained
bursts of traffic. Single-rate policing is implemented using a single token-bucket model,
so that periods of relatively low traffic must occur between traffic bursts to allow the
token bucket to refill. Two-rate policing is implemented using a dual token-bucket model,
which allows bursts of traffic for longer periods.
Single-Rate Three-Color Policers
The single-rate three-color type of policer is defined in RFC 2697, A Single Rate Three
Color Marker . You use this type of policer to rate-limit a traffic flow to a single rate and
three traffic categories (green, yellow, and red). A single-rate three-color policer defines
a
committed bandwidth limit and burst-size limit plus an excess burst-size limit. Traffic
that conforms to the committed traffic limits is categorized as green (conforming). Traffic
that conforms to the bandwidth limit while allowing bursts of traffic as controlled by the
excess burst-size limit is categorized as yellow. All other traffic is categorized as red.
A single-rate three-color policer is most useful when a service is structured according to
packet length, not peak arrival rate.
Two-Rate Three-Color Policers
The two-rate three-color type of policer is defined in RFC 2698, A Two Rate Three Color
Marker . You use this type of policer to rate-limit a traffic flow to two rates and three traffic
categories (green, yellow, and red). A two-rate three-color policer defines a committed
bandwidth limit and burst-size limit plus a peak bandwidth limit and burst-size limit.
Traffic that conforms to the committed traffic limits is categorized as green (conforming).
Traffic that exceeds the committed traffic limits but remains below the peak traffic limits
is categorized as yellow. Traffic that exceeds the peak traffic limits is categorized as red.
A two-rate three-color policer is most useful when a service is structured according to
arrival rates and not necessarily packet length.
Two-Color and Three-Color Policer Options
Both two-color and three-color policers can be configured with the following options:
• Logical Interface (Aggregate) Policers on page 10
• Physical Interface Policers on page 10
9 Copyright © 2016, Juniper Networks, Inc.
Chapter 1: Understanding Traffic Policers