Acknowledgment bucket scheme for regulating TCP flow over ATM

Abstract

The available bit rate (ABR) service has been developed to support data traffic over ATM networks and provide end-to-end congestion control at the ATM layer. However, as most data applications today are only connected to ATM via legacy networks, simulation results in past ATM Forum contributions suggest that ABR may still cause congestion at network edges and cannot provide adequate flow control on an end-to-end basis. In this paper, we propose a new efficient scheme for regulating TCP traffic over ATM networks with the goal of minimizing the network-edge buffer requirement while maximizing TCP goodput. The key idea underlying our scheme is to match the TCP source rate to the ABR explicit rate by controlling the flow of TCP acknowledgments at network edges. We present analytical and simulation results to show that our scheme has negligible buffer requirement, yet offers similar goodput performance as that with infinite buffer. Moreover, our scheme is transparent to the TCP layer and requires no modification in the ATM network except at the network edge.