Policing And Marking Overview - Cisco Catalyst 2960 series Configuration Manual

Information About QoS
You can configure a default class by using the class class-default policy-map configuration command.
Unclassified traffic (traffic specified in the other traffic classes configured on the policy-map) is treated as
default traffic.
You create and name a policy map by using the policy-map global configuration command. When you enter
this command, the switch enters the policy-map configuration mode. In this mode, you specify the actions to
take on a specific traffic class by using the class, trust, or set policy-map configuration and policy-map class
configuration commands.
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.

Policing and Marking Overview

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.
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. 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. After you configure the policy map and policing actions, attach
the policy to a port by using the service-policy interface configuration command.
Related Topics
Ingress Port Activity
Class Maps
Policy Maps
Configuring a QoS Policy, on page 584
Classifying, Policing, and Marking Traffic on Physical Ports by Using Policy Maps, on page 597
Classifying, Policing, and Marking Traffic on SVIs by Using Hierarchical Policy Maps
Classifying, Policing, and Marking Traffic by Using Aggregate Policers, on page 601
Physical Port Policing
In policy maps on physical ports, you can create the following 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.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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