AF TestingCurrent Status and Perspectives

Octavio MedinaJulio Orozco

ENSTB / IRISATF-NGN meetingSouthampton, UK

18/04/2002

• What has been done:– Calibration of WRED

– Calibration of TCM for TCP

• What has been tested:– BW distribution among UDP flows– BW distribution among TCP aggregates– BW distribution TCP vs. UDP

• What has been simulated– Individual TCP behavior– Aggregation– 2 level marking

Current Status

Current Status What’s missing

• Until now, testing has focused in observing BW sharing among flows.– BW sharing under congestion not only depends on

marking, but also on TCP behavior.– Difficult to imagine a large-scale service based on

AF capacities.

• AF offers priority-based packet drop in case of congestion.– Transport protocols don’t know how to take advantage

of that.

– A PHB for applications?

AF-Based Services

• A service proposal may be imagined for CBR sources.– UDP multimedia flows– Shaped TCP aggregates ?

• Tests & simulations for the CBR specific case can be specified.– Focus on Assured Bandwidth, forget BW sharing.

– Concentrate on multi-layer multimedia needs?

Perspectives

• Interest for an IP+ service has decreased– AF benefits are only seen under congestion.

– Congestion not as frequent as before.

• AF may be an alternative for LBE– Compare complexity to WRR.

– Drawbacks related to delay.

• Can AF improve ECN?

• Any other possible use of AF?

Perspectives