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 in order to determine the appropriate outcome. Based on the traffic flow's outcome, the meter selects a subsequent action. Subsequent actions might include to send the packet to another action or to return 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, which uses a two-token bucket metering scheme

• tswtclmt, which 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 to a green, yellow or red outcome.

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