Optimizing an OBS scheduler buffer

• Authors: Andrew Zalesky
• Venue: valuetools '06 Proceedings of the 1st international conference on Performance evaluation methodolgies and tools
• Year: 2006

We dimension a buffer in which headers are enqueued during times an OBS scheduler is overwhelmed. Too large a buffer requires a prolonged offset period to counterbalance longer per-hop worst-case header queueing delays, resulting in reduced throughput and increased packet loss due to edge buffer overflow. While too small a buffer cannot absorb enough variability in the header arrival process, resulting in increased burst lost due to a greater number of headers arriving to find a full buffer. For the first time, we develop and analyze a unified OBS model comprising a set of homogeneous and independent edge buffers that feed bursts to a stand-alone link and their headers to a scheduler. Packets arrive at each edge buffer and are assembled into bursts, after which they are transmitted on a wavelength channel if their corresponding headers are successfully processed. To enable a tractable analysis, we invoke an independence and Poisson assumption that permits decoupling of our model into its three constituent sub-models. Simulation is used to gauge the error incurred in invoking these assumptions. We demonstrate that an optimal buffer size may exist and depends on the number of packets comprising a burst and the size of an edge buffer.