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Cisco IE 3000 Switch Software Configuration Guide
OL-13018-03
Chapter 36 Configuring QoS
Understanding QoS
The policy map can contain the
police
and
police aggregate
policy-map class configuration commands,
which define the policer, the bandwidth limitations of the traffic, and the action to take if the limits are
exceeded.
To enable the policy map, you attach it to a port by using the
service-policy
interface configuration
command.
For more information, see the
“Policing and Marking” section on page 36-8
. For configuration
information, see the
“Configuring a QoS Policy” section on page 36-39
.
Policing and Marking
After a packet is classified and has a DSCP-based or CoS-based QoS label assigned to it, the policing
and marking process can begin as shown in
Figure 36-4
.
Policing involves creating a policer that specifies the bandwidth limits for the traffic. Packets that exceed
the limits are
out of profile
or
nonconforming
. Each policer decides on a packet-by-packet basis whether
the packet is in or out of profile and specifies the actions on the packet. These actions, carried out by the
marker, include passing through the packet without modification, dropping the packet, or modifying
(marking down) the assigned DSCP of the packet and allowing the packet to pass through. The
configurable policed-DSCP map provides the packet with a new DSCP-based QoS label. For
information on the policed-DSCP map, see the
“Mapping Tables” section on page 36-10
. Marked-down
packets use the same queues as the original QoS label to prevent packets in a flow from getting out of
order.
Note
All traffic, regardless of whether it is bridged or routed, is subjected to a policer, if one is configured.
As a result, bridged packets might be dropped or might have their DSCP or CoS fields modified when
they are policed and marked.
You can configure policing on a physical port. For more information about configuring policing on
physical ports, see the
“Policing on Physical Ports” section on page 36-8
.
After you configure the policy map and policing actions, attach the policy to an ingress port by using the
service-policy
interface configuration command. For configuration information, see the
“Classifying,
Policing, and Marking Traffic on Physical Ports by Using Policy Maps” section on page 36-44
and the
“Classifying, Policing, and Marking Traffic by Using Aggregate Policers” section on page 36-48
.
Policing on Physical Ports
In policy maps on physical ports, you can create these types of policers:
•
Individual—QoS applies the bandwidth limits specified in the policer separately to each matched
traffic class. You configure this type of policer within a policy map by using the
police
policy-map
class configuration command.
•
Aggregate—QoS applies the bandwidth limits specified in an aggregate policer cumulatively to all
matched traffic flows. You configure this type of policer by specifying the aggregate policer name
within a policy map by using the
police aggregate
policy-map class configuration command. You
