Cisco IE 4000, Software Configuration Manual

Page: 589 / 1066

585
Configuring QoS
Understanding QoS
For 1-rate, 2-color policing, youYou use the police policy-map class configuration command to define the policer, the
committed rate limitations of the traffic, committed burst size limitations of the traffic, and the action to take for a class
of traffic that is below the limits (
conform-action ) and above the limits ( exceed-action ). If you do not specify burst size
(bc), the system calculates an appropriate burst size value. The calculated value is appropriate for most applications. For
more information, see
Attaching a Traffic Policy to an Interface, page 609 .
When you configure a 2-rate policer, in addition to configuring the committed information rate (CIR) for updating the first
token bucket, you also configure the peak information rate (PIR) at which the second token bucket is updated. If you do
not configure a PIR, the policer is a standard 1-rate, 2-color policer.
For 2-rate, 3-color policing, you can then optionally set actions to perform on packets that conform to the specified CIR
and PIR (conform-action), packets that conform to the PIR, but not the CIR (exceed-action), and packets that exceed the
PIR value (violate-action).

If you set the CIR value equal to the PIR, a traffic rate that is less than or equal to the CIR is in the conform range.
Traffic that exceeds the CIR is in the violate range.

If you set the PIR greater than the CIR, a traffic rate less than the CIR is in the conform range. A traffic rate that
exceeds the CIR but is less than or equal to the PIR is in the exceed range. A traffic rate that exceeds the PIR is in
the violate range.

If you do not configure a PIR, the policer is configured as a 1-rate, 2-color policer.
Setting the burst sizes too low can reduce throughput in situations with bursty traffic. Setting burst sizes too high can
allow too high a traffic rate.
Note: The switch supports byte counters for byte-level statistics for conform, exceed, and violate classes in the show
policy-map interface privileged EXEC command output.
To make the policy map effective, you attach it to a physical port by using the service-policy input interface configuration
command. Policing is done only on received traffic, so you can only attach a policer to an input service policy.
You can use the conform-action and exceed-action policy-map class configuration commands or the conform-action
and exceed-action policy-map class police configuration commands to specify the action to be taken when the packet
conforms to or exceeds the specified traffic rate.
Conform actions are to send the packet without modifications, to set a new CoS, DSCP, or IP precedence value, or to set
a QoS group value for classification at the egress. Exceed actions are to drop the packet, to send the packet without
modification, to set a new CoS, DSCP, or IP precedence to a value, or to set a QoS group value for classification at the
egress.
You can use the conform-action , exceed-action , and violate-action policy-map class configuration commands or the
conform-action , exceed-action , and violate-action policy-map class police configuration commands to specify the
action to be taken when the packet conforms to or exceeds the specified traffic rates. Conform, exceed, and violate
actions are to drop the packet, to send the packet without modifications, to set a new CoS, DSCP, or IP precedence value,
or to set a QoS group value for classification at the egress.
You can configure each marking action by using explicit values, table maps, or a combination of both. Table maps list
specific traffic attributes and map (or convert) them to other attributes.
You can configure multiple conform and exceed actions simultaneously for each service class. You can configure multiple
conform, exceed, and violate actions simultaneously for each service class. If you do not configure a
violate-action , by
default the violate class is assigned the same action as the exceed-action .
After you create a table map, you configure a policy-map policer to use the table map.
Note: When you use a table map in an input policy map, the protocol type for the from –action in the table map must be
the same as the protocol type of the associated classification. For example, if a class map represents 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 .