Cisco ME 3400G-2CS Software Guide - Page 553

Understanding QoS Chapter 30 Configuring QoS Marking This example shows how to use the priority with police commands to configure out-class1 as the priority queue, with traffic going to the queue limited to 20,000,000 bps so that the priority queue never uses more than that. Traffic above that rate is dropped. This allows other traffic queues to receive some port bandwidth, in this case a minimum bandwidth guarantee of 500,000 and 200,000 kbps. The class class-default queue gets the remaining port bandwidth. Switch(config)# policy-map policy1 Switch(config-pmap)# class out-class1 Switch(config-pmap-c)# priority Switch(config-pmap-c)# police 200000000 Switch(config-pmap-c)# exit Switch(config-pmap)# class out-class2 Switch(config-pmap-c)# bandwidth 500000 Switch(config-pmap-c)# exit Switch(config-pmap)# class out-class3 Switch(config-pmap-c)# bandwidth 200000 Switch(config-pmap-c)# exit Switch(config-pmap)# exit Switch(config)# interface gigabitethernet0/1 Switch(config-if)# service-policy output policy1 Switch(config-if)# exit You can use packet marking in input policy maps to set or modify the attributes for traffic belonging to a specific class. After network traffic is organized into classes, you use marking to identify certain traffic types for unique handling. For example, you can change the CoS value in a class or set IP DSCP or IP precedence values for a specific type of traffic. These new values are then used to determine how the traffic should be treated. You can also use marking to assign traffic to a QoS group within the switch. Traffic marking is typically performed on a specific traffic type at the ingress port. The marking action can cause the CoS, DSCP, or precedence bits to be rewritten or left unchanged, depending on the configuration. This can increase or decrease the priority of a packet through the system. The marking function can use information from the policing function or directly from the classification function. You can specify and mark traffic by using the set commands in a policy map for all supported QoS markings (CoS, IP DSCP, IP precedence, and QoS groups). A set command unconditionally marks the packets that match a specific class. You then attach the policy map to an interface as an input policy map. Note When you configure a set qos-group command in an input policy map, you cannot configure other set operations in the same class (such as set dscp, set cos, or set precedence). You can also mark traffic by using the set command with table maps.Table maps list specific traffic attributes and maps (or converts) them to another attribute. A table map establishes a to-from relationship for the attribute and defines the change to be made. Note When you use a table map in an input policy map, the protocol type of the from-type action in the table map must be the same as the protocol type of the associated classification. For example, if a class map represents an IP classification, the from-type action in the table map must be either dscp or precedence. If the class map represents a non-IP classification, the from-type action in the table map must be cos. After you create a table map, you configure a policy map to use the table map. See the "Congestion Management and Scheduling" section on page 30-18. 30-16 Cisco ME 3400 Ethernet Access Switch Software Configuration Guide 78-17058-01