How to Plan Forwarding Behavior

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Before You Begin

Before determining forwarding behavior, you should have defined classes and filters for the QoS policy. Though you often use the meter with the marker to control traffic, you can use the marker alone to define a forwarding behavior.

Review the classes that you have created thus far and the priorities that you have assigned to each class.
Not all traffic classes need to be marked.
Assign the EF per-hop behavior to the class with the highest priority.
The EF PHB guarantees that packets with the EF DSCP 46 (101110) are released onto the network before packets with any AF PHBs. Use the EF PHB for your highest-priority traffic. For more information about EF, refer to Expedited Forwarding (EF) PHB.
Assign forwarding behaviors to classes that have traffic to be metered.
Assign DS codepoints to the remaining classes in agreement with the priorities that you have assigned to the classes.

Example 2-3 QoS Policy for a Games Application

The following shows a portion of a QoS policy. This policy defines a class for a popular games application that generates a high level of traffic.

Class	Priority	Filter	Selector	Rate	Forwarding?
`games_app`	9	`games_in`	`sport 6080`	N/A	N/A
`games_app`	9	`games_out`	`dport 6081`	meter=`tokenmt` committed rate=5000000 committed burst =5000000 peak rate =10000000 peak burst=15000000 green precedence=continue processing yellow precedence=mark yellow PHB red precedence=drop	green =AF31 yellow=AF42 red=drop

The forwarding behaviors assign low-priority DSCPs to games_app traffic that conforms to its committed rate or is under the peak rate. When games_app traffic exceeds peak rate, the QoS policy indicates that packets from games_app are to be dropped. All AF codepoints are listed in Table 6–2.