TCP selective acknowledgments and UBR drop policies to improve ATM-UBR performance over terrestrial and satellite networks

We study the performance of selective acknowledgements (SACK) with TCP over the ATM-UBR service category. We examine various unspecified bit rate (UBR) drop policies, TCP mechanisms and network configurations to recommend optimal parameters for TCP over UBR. We discuss various TCP congestion control mechanisms compare their performance for LANs and WANs. We describe the effect of satellite delays on TCP performance over UBR and present simulation results for LANs, WANs and satellite networks. SACK TCP improves the performance of TCP over UBR, especially for large delay networks. Intelligent drop policies at the switches are an important factor for good performance in local area networks.