A novel delay-bounded traffic conditioner for optical edge switches

Optical packet switched (OPS) networks provide very limited contention resolution resources such as fibre delay lines (FDLs) and wavelength converters. Effective use of these resources in minimising contention losses within the all-optical core requires conditioning of traffic aggregates by the optical edge switches. Traditional rate-based shapers such as the leaky-bucket fail to provide acceptable delay performance for real-time traffic aggregates: this paper therefore explores novel conditioning mechanisms for OPS networks transporting traffic aggregates with time constraints. Using as a theoretical basis a known off-line optimum smoother for stored video traffic, we develop an on-line variable-rate conditioner that approximates the off-line optimum, and requires O(1) amortised computation per packet arrival, making it amenable to efficient hardware implementation at the high data rates required by optical edge switches. We also demonstrate via simulation of short and long range dependent traffic that our conditioner allows losses in the optical core to be reduced by orders of magnitude at the expense of a bounded and relatively low increase in end-to-end delays. We believe that our conditioner can deliver significant performance benefits when employed at the edge of an all-optical network.