Regulation of TCP Flow in Heterogeneous Networks Using Packet Discarding Schemes

Flow control in heterogeneous networks requires careful planning, especially in the case of TCP over ATM, because TCP and ATM each protocol has a different flow control mechanism. The early packet discard scheme (EPD) is commonly used with ATM's unspecified bit rate service (UBR). This thesis presents an improvement to EPD called single packet discard scheme (SPD). The new scheme drops a packet early in the congestion state, so TCP can slow down its rate before the congestion becomes more serious, which can lead to buffer overflow and packets loss. With the SPD scheme, the end-to-end goodput (effective throughput) to input ratio is improved so that a more efficient use of the bandwidth can be reached. If less bandwidth is wasted due to congestion, the preserved bandwidth can be used by other applications and result in a better overall bandwidth utilization. For a configuration used in exploring the goodput performance affected by the SPD scheme, our preliminary result shows an average of 13% improvement for the overall goodput measurement. Thesis Supervisor: Kai-Yeung (Sunny) Siu Title: Assistant Professor of Mechanical Engineering