Cisco Systems A9014CFD manual Unconditional Priority Policing, 24-16

Chapter 24 Configuring QoS

Understanding QoS

The following is a sample configuration of policing ingress traffic over cross connect EVC.

Router(config)# interface GigabitEthernet0/3

Router(config-if)#service instance 22 ethernet

Router(config-if-svr)# encapsulation dot1q 22

Router(config-if-svr)#rewrite ingress tag pop 1 symmetric

Router(config-if-svr)#xconnect 1.1.1.1 100 encapsulation mpls

Router(config-if-svr)#service-policy input policy1

Router(config-if-svr)# exit

You can use the conform-actionand exceed-actionpolicy-map class configuration commands or the conform-actionand exceed-actionpolicy-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 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.

After you create a table map, configure a policy-map policer to use the table map.

Note In Cisco ASR 901, the from–type action in the table map must be cos.

To configure multiple actions in a class, you can enter multiple conform or exceed action entries in policy-map class police configuration mode, as in this example:

Router(config)# policy-map map1

Router(config-pmap)# class class1

Router(config-pmap-c)# police 100000 500000

Router(config-pmap-c-police)#conform-action set-cos-transmit 4

Router(config-pmap-c-police)#conform-action set-qos-transmit 4

Router(config-pmap-c-police)#exceed-action set-cos-transmit 2

Router(config-pmap-c-police)#exceed-action set-qos-transmit 2

Router(config-pmap-c-police)# exit

Router(config-pmap-c)# exit

Router(config-pmap)# exit

Unconditional Priority Policing

Priority policing applies only to output policy maps. You can use the priority policy-map class configuration command in an output policy map to designate a low-latency path, or class-based priority queuing, for a specific traffic class. With strict priority queuing, the packets in the priority queue are scheduled and sent until the queue is empty, at the expense of other queues. Excessive use of high-priority queuing can create congestion for lower priority traffic.

To eliminate this congestion, you can use priority with implicit policer (priority policing) to reduce the bandwidth used by the priority queue and allocate traffic rates on other queues. Priority with police is the only form of policing supported in output policy maps.

Note You cannot configure a policer committed burst size for an unconditional priority policer. Any configured burst size is ignored.

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
24-16	OL-23826-09