Scheduling algorithms make a great impact on the performance of input queueing switches.From Internet traffic characteristics

it is pointed out that short packets should be guaranteed higher priority and lower delay in scheduling algorithms.In general packet-mode scheduling

short packets suffer from long waiting time due to the continuous transferring of cells of long packets.To solve this problem

we study the low-complexity preemptive packet-mode scheduling and propose the algorithm called preemptive short packets first (P-SPF).P-SPF improves the TCP performance by means of the fact that round-trip delays of TCP flows are greatly reduced.Both the analysis in queueing theory and the simulation results with respect to a real traffic model show that P-SPF can achieve almost zero average packet waiting time for short packets

while keeping a high overall throughput up to 94%.