Packet Pacing in Short Buffer Optical Packet Switched Networks

In the absence of a cost-effective technology for storing optical signals, emerging optical packet switched (OPS) networks are expected to have severely limited buffering capability. This paper investigates the resulting impact on end-to-end loss and throughput, and proposes that the optical edge switches “pace” packets into the OPS core to improve performance without adversely affecting end-to-end delays. In this context, our contributions are three-fold. We first evaluate the impact of short buffers on the performance of real-time and TCP traffic. This helps us identify short-time-scale burstiness as the major contributor to performance degradation, so we propose that the optical edge switches pace the transmission of packets into the OPS core while respecting their delay-constraints. Our second contribution develops algorithms of poly-logarithmic complexity that can perform optimal real-time pacing of high data rate traffic. Lastly, we show via simulations of a realistic network carrying real-time traffic that pacing can significantly reduce losses at the expense of a bounded increase in end-to-end delay. The loss-delay trade-off mechanism provided by pacing can help achieve desired OPS network performance.