Chapter 24 Configuring QoS

Understanding QoS

Note Effective with Cisco IOS Release 15.2(2)SNI, the lower limit of the committed burst size (bc) is 1 ms.

Class-Based Shaping

Class-based shaping uses the shape average policy-map class configuration command to limit the rate of data transmission as the number of bits per second to be used for the committed information rate for a class of traffic. The router supports separate queues for three classes of traffic. The fourth queue is always the default queue for class class-default, unclassified traffic.

Note In the Cisco ASR 901 router, configuring traffic shaping automatically sets the minimum bandwidth guarantee or committed information rate (CIR) of the queue to the same value as the PIR.

This example shows how to configure traffic shaping for outgoing traffic on a gigabitethernet port so that outclass1, outclass2, and outclass3 get a maximum of 50, 20, and 10 Mbps, respectively, of the available port bandwidth. The class class-defaultat a minimum gets the remaining bandwidth.

Router(config)# policy-map out-policy

Router(config-pmap)# class classout1

Router(config-pmap-c)# shape average 50000000

Router(config-pmap-c)# exit

Router(config-pmap)# class classout2

Router(config-pmap-c)# shape average 20000000

Router(config-pmap-c)# exit

Router(config-pmap)# class classout3

Router(config-pmap-c)# shape average 10000000

Router(config-pmap-c)# exit

Router(config-pmap)# exit

Router(config)# interface gigabitethernet 0/1

Router(config-if)#service-policy output out-policy

Router(config-if)# exit

Port Shaping

To configure port shaping (a transmit port shaper), create a policy map that contains only a default class, and use the shape average command to specify the maximum bandwidth for a port.

This example shows how to configure a policy map that shapes a port to the out-policypolicy map configured in the previous example. The command is used to create a child policy to the parent:

to 90 Mbps, allocated according service-policypolicy map class

Router(config)# policy-map out-policy-parent

Router(config-pmap)# class class-default

Router(config-pmap-c)# shape average 90000000

Router(config-pmap-c)#service-policy out-policy

Router(config-pmap-c)# exit

Router(config-pmap)# exit

Router(config)# interface gigabitethernet0/1

Router(config-if)#service-policy output out-policy-parent

Router(config-if)# exit

Parent-Child Hierarchy

The router also supports parent policy levels and child policy levels for traffic shaping. The QoS parent-child structure is used for specific purposes where a child policy is referenced in a parent policy to provide additional control of a specific traffic type.

 

Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide

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Cisco Systems A9014CFD manual 24-20, Routerconfig# policy-map out-policy-parent