Policy Framework Configuration Guide - Juniper Networks

Chapter 11: Policer Configuration
If traffic arriving on the logical interface is within the average rate of 40 Mbps (based on
the token bucket formula) or within the committed burst size limit of 100 KB, the packets
are “green” and are marked with an implicit loss priority of low. If traffic arriving on the
logical interface is above the committed information rate and above the committed burst
size but still within the excess burst size of 200 KB, the packets are “yellow” and are
marked with an implicit loss priority of medium-high. If traffic arriving on the logical
interface is above the excess burst size of 200 KB, the packets are “red,” are marked with
an implicit loss priority of high, and are discarded. In the “red” case, if you omit the action
statement, the packets are still marked with an implicit loss priority of high, but the
packets are transmitted. As the traffic rate slows and the newly arriving traffic conforms
to the configured limits, Junos OS stops marking packets with the medium-high and high
loss priorities and stops dropping red packets.
For single-rate, three-color policing, Junos OS uses two token buckets to manage
bandwidth based on the rate of traffic.
When the policer is color-aware, the local router can assign a higher packet-loss priority,
but cannot assign a lower packet-loss priority. For example, suppose an upstream router
assigned medium-high loss priority to a packet because the packet exceeded the
committed information rate on the upstream router interface. The local router cannot
change the packet-loss priority to low, even if the packet conforms to the configured
committed information route on the local router interface. However, if the stream exceeds
the excess burst size configured on the local router interface, the packets are assigned
high loss priority.
If you configure a policer to be color-blind instead of color-aware, the color-blind node
ignores preexisting markings. A packet with medium-high loss priority can be assigned
low or high loss priority.
Configuring a Single-Rate Three-Color Policer
You can apply a single-rate three-color policer to the input or output interface.
To configure a single-rate three-color policer:
1. Configure the policer.
[edit firewall three-color-policer policer2]
user@host# set single-rate color-aware
user@host# set single-rate committed-information-rate 40m
user@host# set single-rate committed-burst-size 100k
user@host# set single-rate excess-burst-size 200k
For three-color policers, the only configurable action is to discard red packets. Red
packets are packets that have been assigned high loss priority because they exceeded
the excess burst size (EBS).
[edit firewall three-color-policer srTCM1-ca]
user@host# set action loss-priority high then discard
2. Configure the policer type.
[edit firewall policer policer1]
user@host# set logical-interface-policer
Copyright © 2010, Juniper Networks, Inc.
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