Optical networks are leaving the labs and becoming a reality. Despite the current crisis of the telecom industry, the dependence of society on communication networks for information exchange, medicine, education, data transfer, commerce, and many other endeavours dominates our everyday life. High capacity links are required by the large Internet traffic demand, and optical networks remain one of the most promising technologies for meeting these needs. WDM systems are today widely deployed, thanks to low-cost at extreme data rates and high reliability of optical components, such as optical amplifiers and fixed/tunable filters and transceivers. Access and metropolitan area networks are increasingly based on optical technologies to overcome the electronic bottleneck at the network edge. Traditional multi-layer architectures, such as the widely deployed IP/ATM/SDH protocol stack, are increasingly based on WDM transport; further efforts are sought to move at the optical layer more of the functionalities available today in higher protocol layers. New components and subsystems for very high-speed optical networks offer new design opportunities to network operators and designers. The trends towards dynamically configurable all-optical network infrastructures open up a wide range of new network engineering and design choices, which must face issues such as interoperability and unified control and management. Next Generation Optical Network Design and Modelling contains the papers presented at the Sixth Working Conference on Optical Network Design and Modelling, which was sponsored by the International Federation for Information Processing (IFIP) and held in February 2002 at Politecnico di Torino, Italy. With contributions from researchers, network operators and manufacturers from Europe, America and Asia, this volume provides a comprehensive snapshot of the current state of the art in optical networking.