Analysis of packet discarding policies in high-speed networks

Selective discarding policies, as a means for congestion avoidance, are studied and compared to non-discarding policies. The partial message discard policy discards the packets of the tails of corrupted messages. An improvement to this policy is the early message discard that drops entire messages and not just message-tails. A common performance measure of the network elements is the effective throughput which measures the utilization of the network links but which neglects the application altogether. We adopt a new performance measure, goodput, which reflects the utilization of the network from the application's point of view and thus better describes the network behavior. We develop and analyze a model for systems which employ discarding policies. The analysis shows a remarkable performance improvement when any message-based discarding policy is applied, and that the early message discard policy performs better, especially under high loads. We compute the optimal parameter setting for maximum goodput at different input loads and investigate the performance sensitivity to these parameters.