Cisco IE 4000, Software Configuration Manual

Page: 593 / 1066

589
Configuring QoS
Understanding QoS
Switch(config)#
policy-map policy1
Switch(config-pmap)# class out-class1
Switch(config-pmap-c)# priority
Switch(config-pmap-c)#
police 200000000
Switch(config-pmap-c)# exit
Switch(config-pmap)# class out-class2
Switch(config-pmap-c)#
bandwidth 500000
Switch(config-pmap-c)# exit
Switch(config-pmap)# class out-class3
Switch(config-pmap-c)#
bandwidth 200000
Switch(config-pmap-c)# exit
Switch(config-pmap)# exit
Switch(config)#
interface GigabitEthernet1/17
Switch(config-if)# service-policy output policy1
Switch(config-if)# exit
Marking
You can use packet marking in input policy maps to set or modify the attributes for traffic belonging to a specific class.
After network traffic is organized into classes, you use marking to identify certain traffic types for unique handling. For
example, you can change the CoS value in a class or set IP DSCP or IP precedence values for a specific type of traffic.
These new values are then used to determine how the traffic should be treated. You can also use marking to assign traffic
to a QoS group within the switch.
Traffic marking is typically performed on a specific traffic type at the ingress port. The marking action can cause the CoS,
DSCP, or precedence bits to be rewritten or left unchanged, depending on the configuration. This can increase or
decrease the priority of a packet in accordance with the policy used in the QoS domain so that other QoS functions can
use the marking information to judge the relative and absolute importance of the packet. The marking function can use
information from the policing function or directly from the classification function.
You can specify and mark traffic by using the set commands in a policy map for all supported QoS markings (CoS, IP
DSCP, IP precedence, and QoS groups). A set command unconditionally marks the packets that match a specific class.
You then attach the policy map to an interface as an input policy map.
You can also mark traffic by using the set command with table maps.Table maps list specific traffic attributes and maps
(or converts) them to another attribute. A table map establishes a to-from relationship for the attribute and defines the
change to be made.
You can simultaneously configure actions to modify DSCP, precedence, and COS markings in the packet for the same
service along with QoS group marking actions. You can use the QoS group number defined in the marking action for
egress classification.
Note: When you use a table map in an input policy map, the protocol type of the from -type action in the table map must
be the same as the protocol type of the associated classification. For example, if a class map represents an IP
classification, the
from -type action in the table map must be either dscp or precedence . If the class map represents a
non-IP classification, the from -type action in the table map must be cos .
After you create a table map, you configure a policy map to use the table map. See Congestion Management and
Scheduling, page 593 . Figure 81 on page 590 shows the steps for marking traffic.