On the Performance of ATM-UBR with Early Selective Packet Discard

We investigate the performance of the Early Packet Discard(EPD) and the Early Selective Packet Discard(ESPD) scheme that we have previously proposed[12]. In an e ort to reduce the complexity while maintaining good performance, we pick out two special cases of ESPD and compare their performance with that of EPD. For performance evaluation purposes, the e ective throughput and fairness index was determined through a simulation study. We observed that ESPD scheme improves e ective throughput over EPD by up to 16% with our network model. We also found that ESPD is more e ective in alleviating TCP's unfairness among connections which have di erent roundtrip times. A major factor causing throughput degradation of EPD was determined to be the synchronization of TCP windows.