Quality of Service
QoS Advanced Mode
Cisco 350, 350X and 550X Series Managed Switches, Firmware Release 2.4, ver 0.4 437
23
Aggregate Policer
You can measure the rate of traffic that matches a pre-defined set of rules, and to enforce
limits, such as limiting the rate of file-transfer traffic that is allowed on a port.
This can be done by using the ACLs in the class map(s) to match the desired traffic, and by
using a policer to apply the QoS on the matching traffic.
A policer is configured with a QoS specification. There are two kinds of policers:
• Single (Regular) Policer—A single policer applies the QoS to a single class map, and
to a single flow based on the policer's QoS specification. When a class map using
single policer is bound to multiple ports, each port has its own instance of single
policer; each applying the QoS on the class map (flow) at ports that are otherwise
independent of each other. A single policer is created in the Policy Table page.
• Aggregate Policer—An aggregate policer applies the QoS to one or more class maps,
and one or more flows. An aggregation policer can support class maps from different
policies. An aggregate policer applies QoS to all its flow(s) in aggregation regardless
of policies and ports. An aggregate policer is created in the Aggregate Policer page.
An aggregate policer is defined if the policer is to be shared with more than one class.
Policers on a port cannot be shared with other policers in another device.
Each policer is defined with its own QoS specification with a combination of the following
parameters:
• Peak Enforcement—Select to enable action if peak burst size is exceeded.
• Peak Information Rate (PIR)—Enter the peak traffic rate (PIR) in kbits per second
(kbps).
• Peak Burst Size (PBS)—Enter the peak burst size (PIR) in kbits per second (kbps).
• Violate Action—Select one of the following actions if peak size is exceeded:.
- Drop—Drop the frames violating the peak size.
- Out-of-Profile DSCP—Mark frames violating the peak size with the DSCP value
with previously-set DSCP value.
• A maximum allowed rate, called a Committed Information Rate (CIR), measured in
Kbps.
• An amount of traffic, measured in bytes, called a Committed Burst Size (CBS). This is
traffic that is allowed to pass as a temporary burst even if it is above the defined
maximum rate.
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