Two-rate, three-color marker

The two-rate, three-color marker (TrTCM) meters an IP packet stream and marks its packets either green, yellow, or red.

There are four main parameters in a dual-rate traffic contract. CIR, CBS, PIR, and EBS.

Marking is based on CIR. Packets are marked:

Green - if it does not exceed the CIR
Yellow - if it exceeds the CIR
Red - if it exceeds the peak information rate (PIR)

The TrTCM is useful for ingress policing of a service, where a peak rate needs to be enforced separately from a committed rate.

Implementation

A dual-rate traffic contract supplies customers with two sending rates but only guarantees the smaller one. In case of congestion in the network, it discards traffic that exceeds the committed rate more aggressively and signals the customer to slow down to the committed rate. This principle was first widely implemented in Frame-Relay networks, but could be easily replicated using any packet-switching technology. There are four main parameters in a dual-rate traffic contract.