TCP and UDP performance for Internet over optical packet-switched networks

Optical packet-switched (OPS) network is a strong candidate for the future Optical Internet. In this paper, we study packet aggregation and deflection routing as employed in OPS networks on the performance of upper layer Internet protocols represented by TCP and UDP. Regarding packet aggregation schemes, we study no aggregation, mixed-flow aggregation, and per-flow aggregation. Our results show that for both TCP and UDP, mixed-flow aggregation achieves the highest throughput, and per-flow aggregation significantly decreases the fairness at large aggregation intervals. Both aggregation schemes increase UDP delay jitter. Regarding deflection routing, we show that deflection routing significantly improves TCP throughput in spite of the out-of-order packet delivery. However, the congestion of the deflection path significantly affects the improvement that can be achieved. UDP throughput does not suffer from out-of-order packet delivery, and hence its throughput improvement by deflection routing can be even more prominent. The larger the deflection cost (delay difference between the deflection path and the shortest path) is, the larger UDP delay jitter results. Deflection cost, however, does not affect the throughput and fairness very much for both TCP and UDP.