Queueing analysis of optical and electronic combined buffer for optical packet switches

Optical packet switching provides high-speed and energy-efficient packet forwarding. Fiber delay line (FDL)-based buffer is one practical solution to avoid packet contention in optical packet switches. However, the FDL buffer suffers from scalability problems, and thus, cannot accommodate a large volume of network traffic at a time. An optical and electronic combined (OE) buffer architecture alleviates the scalability issues. This architecture uses supplementary electronic RAM buffers when the traffic volume increases. We then propose an analytical model of the OE buffer to estimate the blocking probability and the average delay. We find that complex OE combined model can be simply modeled by combination of an existing analytic model of the FDL buffer and an M/M/1/K queueing system. Comparing analytical results with packet-level simulation results, we demonstrate that our analytical results display characteristics similar to the simulation results. This analysis enables to determine appropriate setting of the OE buffer such as the buffer size and use policy.