On TCP performance in ATM networks with per-VC early packet discard mechanisms

Both available bit rate (ABR) service and unspecified bit rate (UBR) service with early packet discard (EPD) schemes have been considered for supporting data applications in ATM networks. Since the transmission control protocol (TCP) is perhaps the most widely used transport layer protocol in existing data networks, the performance of TCP over ATM using ABR and UBR services with EPD schemes is of great interest to ATM equipment vendors and service providers. With regard to this interesting issue, we demonstrate in earlier work [1] some simulation results, which show that (1) with UBR service and EPD schemes, TCP suffers significant performance degradation in terms of fairness and requires a relatively large switch buffer even with a small number of active virtual connections over a LAN configuration, and (2) for the same set of network configurations and with ABR service, TCP achieves good performance in terms of fairness and link utilization, and requires relatively small switch buffer. In this paper, we extend our work [1] by studying the performance of TCP over UBR service where EPD schemes are improved by using per-VC accounting and per-VC queueing techniques. In particular, our simulation results show that in a LAN environment, per-VC based EPD schemes can significantly improve the performance of TCP over UBR service in terms of fairness.