Juniper EX9200 Series, Features Manual

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CHAPTER 14
Basic Single-Rate Three-Color Policers
• Single-Rate Three-Color Policer Overview on page 153
• Example: Configuring a Single-Rate Three-Color Policer on page 154
Single-Rate Three-Color Policer Overview
A single-rate three-color policer defines a bandwidth limit and a maximum burst size for
guaranteed traffic and a second burst size for peak traffic. A single-rate three-color policer
is most useful when a service is structured according to packet length and not peak arrival
rate.
Single-rate three-color policing meters a traffic stream based on the following configured
traffic criteria:
•
Committed information rate (CIR)—Bandwidth limit for guaranteed traffic.
• Committed burst size (CBS)—Maximum packet size permitted for bursts of data that
exceed the CIR.
•
Excess burst size (EBS)—Maximum packet size permitted for peak traffic.
Single-rate tricolor marking (single-rate TCM) classifies traffic as belonging to one of
three color categories and performs congestion-control actions on the packets based
on the color marking:
• Green—Traffic that conforms to either the bandwidth limit or the burst size for
guaranteed traffic (CIR or CBS). For a green traffic flow, single-rate marks the packets
with an implicit loss priority of
low
and transmits the packets.
•
Yellow—Traffic that exceeds both the bandwidth limit and the burst size for guaranteed
traffic (CIR and CBS) but not the burst size for peak traffic (EBS). For a yellow traffic
flow, single-rate marks the packets with an implicit loss priority of
medium-high and
transmits the packets.
• Red—Traffic that exceeds the burst size for peak traffic (EBS), single-rate marks
packets with an implicit loss priority of
high
and, optionally, discards the packets.
If congestion occurs downstream, the packets with higher loss priority are more likely to
be discarded.
153 Copyright © 2016, Juniper Networks, Inc.