Design of wavelength converting switches for optical burst switching

Optical burst switching (OBS) is an experimental network technology that enables the construction of very high-capacity routers, using optical data paths and electronic control. In this paper, we study wavelength converting switches using tunable lasers and wavelength grating routers, that are suitable for use in OBS systems and evaluate their performance. We show how the routing problem for these switches can be formulated as a combinatorial puzzle or game, in which the design of the game board corresponds to the pattern of permutation used at the input sections of the switch. We use this to show how the permutation pattern affects the performance of the switch, and to facilitate the design of permutation patterns that yield the best performance. We give upper bounds on the number of different wavelength channels that can be routed through such switches (regardless of the permutation pattern), and show that for 2 x 2 switches, there is a simple permutation pattern that achieves these bounds. For larger switches, randomized permutation patterns produce the best results. We study the performance of optical burst switches using wavelength converting switches based on several different permutation patterns. We also present a novel routing algorithm called the most available wavelength assignment and evaluate its benefits in improving the switch throughput. Our results show that for a typical configuration, the switch with the best permutation pattern has more than 87% of the throughput of a fully nonblocking switch.