The new telecommunication networks scenario is characterised by a very rapid increase of the volume of traffic, and also very variable and unpredictable traffic demands. In this context, all-optical packet switching is emerging as the most promising technology for covering such new requirements. In this paper, we deal with the performance analysis of an optical packet switch with a feedback delay line buffer configuration. The network mode operation is slotted and the case of a realistic traffic model (i.e., variable-length packets modelled by self-similar traffic) fitted into trains of fixed-size slots is considered. Results from contention resolution performed by using both the time and the wavelength domains show that they must be exploited as combined tools in order to obtain good node performance.