Actions Performed for Hierarchical Policers
The hierarchical parent policer impacts the packet loss priority (PLP) of the child policer.
The PLP-based actions defined in the then statement of the are performed, based on
the PLP derived from the combined processing of the child and parent policers. The then
statement defined in the parent policer is not effective. This section contains the following
topics that describe the methods of instantiation of aggregate or hierarchical policers
and child or normal policers.
NOTE: Hierarchical policer is not applicable on ACX5048 and ACX5096
routers.
Instantiation Methods for Child and Aggregate Policers
In the Junos OS, a certain policer configuration or a policer template is used to create
multiple instances of the policer in the hardware using the template attributes such as
the CIR, PIR, CBS, and PBS values specified in the template. You need not create multiple
policer configurations with the same attributes for effective management by using
aggregate policers.
Instantiation Methods for Child Policers or Normal Policers
For a normal policer or a child policer, if you specify a filter-specific attribute for a policer
by entering the filter-specific statement at the [edit firewall policer policer-name] or [edit
logical-systems logical-system-name firewall policer policer-name] hierarchy level, when
you specify a ‘filter-specific’ clause, a single policer instance is used by all terms (within
the same firewall filter) that reference the policer. For example, if a filter F1 contains
terms T1 and T2, they refer to the same policer, say P1. If you configure the policer P1 as
a filter-specific type, the same policer instance on the device is referred by both the terms
T1 and T2. In this case, F1 is attached to a logical interface named IFL1, which is configured
on the physical interface named IFD1.
By default, a policer operates in term-specific mode so that, for a given firewall filter, the
Junos OS creates a separate policer instance for every filter term that references the
policer. This operation is the default instantiation mode if you do not configure the
filter-specific statement. For example, consider a filter F1 that has two terms, T1 and T2.
Both these terms refer to the same policer, namely P1. With a term-specific mode of the
policer, two policer instances are created on the device, one each for terms T1 and T2.
Instantiation Methods for Aggregate Policers
The following modes of operations are possible for aggregate policers.
•
Global—Shares the same parent policer across all the child policer instances in the
system.
•
Physical interface-specific—Shares the same parent policer across all the child policer
instances of a certain physical interface. This mode is not supported on ACX routers.
929Copyright © 2017, Juniper Networks, Inc.
Chapter 27: Configuring Class of Service
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