Cisco Systems A9014CFD manual Policing, 24-14

Chapter 24 Configuring QoS

Understanding QoS

•Cos to Qos-group

•Qos-group to mpls experimental topmost

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.

Policing

After a packet is classified, you can use policing as shown in Figure 24-5to 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 the “Unconditional Priority Policing” section on page 24-16.

Figure 24-5

Receive

Policing of Classified Packets
			Packets that conform		Queuing,
	Classify		to the committed		scheduling,
			information rate (CIR)		and shaping
			Packets that exceed
			the CIR
		An exceed-action at this
				Drop
		point results in dropped				141153
		or reclassified packets.

This section contains the following topics:

•Individual Policing, page 24-15

•Unconditional Priority Policing, page 24-16

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
24-14	OL-23826-09