Cisco IE 4000, Software Configuration Manual

Page: 588 / 1066

584
Configuring QoS
Understanding QoS

Precedence to CoS

Precedence to DSCP

Precedence to precedence
Table maps modify only one parameter (CoS, IP precedence, or DSCP, whichever is configured) and are only effective
when configured with a
set command in a policy map or with a conform-action or exceed-action command in a police
function. Individual policers also support the violate-action command, but aggregate policers do not support table maps
with violate-action.
Table maps are not supported in output policy maps. For more information, set the Configuring Table Maps, page 608 .
Policing
After a packet is classified, you can use policing as shown in Figure 80 on page 584 to regulate the class of traffic. The
policing function limits the amount of bandwidth available to a specific traffic flow or prevents a traffic type from using
excessive bandwidth and system resources. A policer identifies a packet as in or out of profile by comparing the rate of
the inbound traffic to the configuration profile of the policer and traffic class. Packets that exceed the permitted average
rate or burst rate are
out of profile or nonconforming . These packets are dropped or modified (marked for further
processing), depending on the policer configuration.
Policing is used primarily on receiving interfaces. You can attach a policy map with a policer only in an input service policy.
The only policing allowed in an output policy map is in priority classes. See
Unconditional Priority Policing, page 588 .
Figure 80 Policing of Classified Packets
These sections describe the types of policing supported on the switch:

Individual Policing, page 584

Aggregate Policing, page 586

Unconditional Priority Policing, page 588
Individual Policing
Individual policing applies only to input policy maps. In policy-map configuration mode, you enter the class command
followed by class-map name, and enter policy-map class configuration mode.
Cisco Industrial Ethernet Switches support 1-rate, 2-color ingress policing and 2-rate, 3-color policing for individual or
aggregate policing.
141153
Receive
Classify
Drop
Queuing,
scheduling,
and shaping
An exceed-action at this
point results in dropped
or reclassified packets.
Packets that conform
to the committed
information rate (CIR)
Packets that exceed
the CIR