On Fairness of ATM UBR Service in Carrying Heterogeneous Internet Traffic

Fairness of the UBR service has been evaluated recently in the context of homogeneous Internet traffic where all sources implement TCP congestion control algorithm. In this study, we evaluate the fairness of various flavors of the ATM UBR service in the heterogeneous environment where both TCP and UDP traffic share the same buffer. Although the fair buffer allocation (FBA) is known to be very fair for homogeneous TCP environment, our results suggest that none of the UBR flavors, including FBA, performs well on the fairness scale; UDP sources grab more bandwidth than TCP sources. The fairness for the simulated network was below 50% of the optimal situation even with FBA.