Drop Policy Combined with Multiple Edge Thresholds in TCP over OBS Networks

In this paper, we proposed a novel Burst Drop Policy based on Hop Number Factor (HNF) in the core nodes of TCP over OBS networks, which is combined with Multiple Thresholds in the edge nodes. The proposed drop policy, HNF, takes the retransmission cost into account, and gives the burst with the larger Hop Number Factor the higher priority in the contention. On the other hand, for the retransmission is not always effective, multiple Edge Thresholds, Retransmission Number Threshold (RNT), Traffic load Threshold (TlT) and Total hop Threshold (ThT), are proposed to limit the unnecessary retransmission in the OBS layer. If any of the thresholds is exceeded, the retransmission will be handed over to the upper layer, the TCP layer, which will be more cost-effective. The simulation results show that the combined mechanism can reduce the burst loss rate, decrease the round trip time and improve the throughput of TCP over OBS networks significantly.