Strategies and algorithms for routing both unicast and multicast paths in WDM networks

This paper introduces the concept of the multicast optical path in WDM netw orks, and treats the strategies and the algorithms, which allow the routing of plural multicast paths together with unicast paths. This analysis was m otivated by the possibility of exploit the optical layer facilities in the transport network, to carry distributive services, such as video channels ( e.g. CATV), without the need of dedicated transmission networks. The strate gies and algorithms reported in this paper arise from a generalisation of t hose ones, which have been previously reported in literature. They are wave length path (WP: which does not make use of wavelength conversion), virtual wavelength path (VWP: which make full use of wavelength conversion), and p artial virtual wavelength path (PVWP: making a parsimonious use of waveleng th conversion). The analysis shows the characteristics and performance of t hose strategies and algorithms considering, as a figure of merit, either th e number of wavelengths or the system scale (dimensions of the optical node s), and compare one to each other in order to point oat advantages and disa dvantages. The main result is that multicast optical paths can favourably b e accommodated in a WDM network, and the strategy we propose, making a pars imonious use of wavelength conversion, allows the lowest system scale to be obtained with a very low number of wavelength converters.