This paper studies the virtual topology design and reconfiguration problem of virtual private networks (VPNs) over all-optical WDM networks. We formulate the problem as an Integer Programming problem with objectives to maximize the network throughput, and to minimize the average end-to-end propagation delay, and to minimize the reconfiguration cost. Load balancing and alternate routing are considered in order to increase the network throughput. A balanced alternate routing algorithm (BARA) is also proposed to obtain approximate optimal solutions to the formulated problem. To make the problem computationally tractable, we assume wavelength converters at network nodes and approximately divide the optimization process into two relatively independent stages: route computing and lightpath routing. To improve the computational efficiency, a genetic algorithm is used in BARA. The effectiveness of BARA is shown through simulation results.
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