Dynamic routing and wavelength assignment with optical bypass using ring embeddings ?
We consider routing and wavelength assignment in ring, torus, and tree topologies with the twin objectives of minimizing wavelength usage and maximizing optical bypass. The P P -port dynamic traffic assumption is used, which allows each node to send and receive at most P P calls. For rings we show that ?PN/4? ? P N / 4 ? wavelengths are necessary and sufficient, and provide a four-hub ring architecture that requires only half of these wavelengths to be locally processed. We extend this approach to develop RWA and bypass algorithms for both tori and trees by embedding virtual rings within these topologies and applying the ring algorithms. For an RC R  C torus, we embed R+C R + C rings onto the torus and provide an approach to RWA and banding based on solving disjoint RWA/banding problems for each ring. Our RWA algorithm is more wavelength efficient than any currently known algorithm and uses the minimum number of wavelengths for R?2C R ? 2 C . Our subsequent banding algorithm allows half of these wavelengths to bypass all but 4R 4 R hub nodes. Finally, we give a RWA for trees that embeds a single virtual ring and uses the ring to obtain a RWA that requires no more than ?PN/2? ? P N / 2 ? total wavelengths; this figure is shown to be optimal for balanced binary trees. A banding algorithm follows that allows half these wavelengths to bypass all non-hub nodes.
routing and wavelength assignment bypass wdm optical networks waveband switching