Meter (tokenmt and tswtclmt) Overview

In the Diffserv model, the meter tracks the transmission rate of traffic flows on a per-class basis. The meter evaluates how much the actual rate of the flow conforms to the configured rates to determine the appropriate outcome. Based on the traffic flow's outcome, the meter selects a subsequent action. Subsequent actions might include sending the packet to another action or returning the packet to the network without further processing.

The IPQoS meters determine whether a network flow conforms to the transmission rate that is defined for its class in the QoS policy. IPQoS includes two metering modules:

• tokenmt – Uses a two-token bucket metering scheme

• tswtclmt – Uses a time-sliding window metering scheme

Both metering modules recognize three outcomes: red, yellow, and green. You define the actions to be taken for each outcome in the parameters red_action_name, yellow_action_name, and green_action_name.

In addition, you can configure tokenmt to be color aware. A color-aware metering instance uses the packet's size, DSCP, traffic rate, and configured parameters to determine the outcome. The meter uses the DSCP to map the packet's outcome to a green, yellow, or red.

For information on defining parameters for the IPQoS meters, refer to How to Plan Flow Control.