Enhancement of an optical burst switch with shared electronic buffers

Future data networks face an energy consumption challenge: traffic grows exponentially, but the energy cost per bit in electronic routers and switches does not decrease so fast. All-optical switching techniques have not delivered a solution to this problem: despite their requiring fewer energetically-costly optical-to-electronic conversions, they suffer from poor contention handling even at low network loads, thus needing heavy overprovisioning, which negates the energy savings achieved in the first place. This contention issue largely stems from the lack of sufficiently-mature optical buffers. Thus a proposition of hybrid switch architecture supplementing optical switching with an electronic buffer. We analyze such a hybrid switch in terms of loss probability and sustainable load. Simulations and an Engset-type analytical model both find significant performance improvements for relatively few electronic ports to/from the buffer. The highest gains are shown when few channels are available per destination. Moreover, we note that traffic re-emitted from the buffer is a major cause of unnecessary buffering and secondary collisions. An adjustment to the re-emission policy is found to mitigate such collisions and offer slight gains on the sustainable load.