An efficient adaptive offset mechanism to reduce burst losses in OBS networks

Optical burst switching (OBS) is a new optical switching paradigm where traffic can be switched and groomed at a lower level compared to optical circuit switching (OCS). Although research in OBS networks has evolved from theoretical investigations to proof-of-concept demonstrations, several key issues need to be investigated further before OBS prototypes can clearly outperformed OCS networks. While the burst loss rate is often used as the main performance parameter in OBS networks, burst losses come from two sources, contention and insufficient offset time (IOT) due to deflection routing. In this paper, we investigate further the assignment of the offsets and propose an adaptive offset determination that depends on both the bandwidth utilization of the links and nodes traversed by the bursts and some measurement of the burst losses due to insufficient offset time. Numerical results demonstrate that our approach is effective in reducing the network burst drop rate through a reduction of the burst losses due to insufficient offset time. Moreover, it proves to lead to a highly stable IOT burst drop even for dynamic traffic and can be easily controlled, so as to find the equilibrium between the IOT and contention burst drops leading to the minimum burst drop rate