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. In an effort to reduce the complexity while maintaining a good performance, we pick two special cases of the ESPD and compare their performance with that of the EPD. For performance evaluation purposes, the effective throughput and fairness index of these schemes were determined through a simulation study. We observed that the ESPD scheme improves the effective throughput over the EPD by up to 16% with our network model. We also found that ESPD is more effective in alleviating the TCP's unfairness among connections which have different roundtrip times. A major factor causing throughput degradation of the EPD was determined to be the synchronization of TCP windows.