To Burst or Circuit Switch?

We develop, analyze and then numerically compare performance models of a fast-adapting and centrally controlled form of optical circuit switching (OCS) with a conservative form of optical burst switching (OBS). For the first time, we consider a unified model comprising both: edge buffers at which arriving packets are aggregated and enqueued according to a vacation-type service discipline with nondeterministic set-up times, together with a core network comprising switches arbitrarily interconnected via fibers to allow transmission of packets from an edge buffer to their desired egress point through use of a dynamic signaling process to establish a lightpath, and in the case of OCS, also acknowledge its establishment. As such, edge buffers dynamically issue requests for wavelength capacity via a two or one-way reservation signaling process. Previously analyzed models of OCS and OBS have either been for a stand-alone edge buffer or a core network without edge buffering. We compare OCS with OBS in terms of packet blocking probability due to edge buffer overflow and blocking at switches in the case of OBS; mean packet queueing delay at edge buffers; and, wavelength capacity utilization. Also for the first time, we derive the exact blocking probability for a multi-hop stand-alone OBS route, assuming Kleinrock´s independence, which is not simply a matter of summing the stationary distribution of an appropriate Markov process over all blocking states, as shown to be the case for an OCS route.