It provides a low bounded queueing delay service in the Internet. The service is best-effort, and requires no additional charging or usage control. Its goal is to help applications with stringent real time constraints, such as interactive audio. With ABE, it is not required to police how much traffic uses the low delay capability, the service being designed to operate equally well in all traffic scenarios. Every best effort packet is tagged as either green or blue .
Green packets receive a low, bounded queueing delay.
To ensure blue packets do not suffer as a result, green flows receive less throughput during bouts of congestion. Green and blue were chosen because they are primary colours of equal value, with neither having priority over the other. Green is picked for low-delay because it is the go signal on a traffic light. For example, one application that would likely benefit from ABE would be IP Telephony . Blue traffic seeks to minimise overall transfer time, but does not care so much about individual packet delays.