A new model for allocating resources to scheduled lightpath demands

Recent research has clearly established that holding-time-aware routing-and-wavelength-assignment (RWA) schemes lead to significant improvements in resource utilization for scheduled traffic. Two different models have been proposed for scheduled traffic in the literature - (i) the fixed window model, where the setup and the teardown times of the scheduled demands are known in advance and (ii) the sliding window model, where a demand can be allocated anytime within a larger time-window. In this paper, we introduce a new model, the segmented sliding window model, where a demand may be decomposed into two or more components and each component can be sent separately. We present an integer linear program (ILP) formulation for resource allocation under the proposed segmented sliding window model and show that both the fixed and the traditional sliding window models can be treated as a special case of our generalized segmented sliding window model. We consider networks both with and without wavelength converters, and include the option of path protection for each lightpath. For larger networks, we also present a heuristic algorithm for allocating resources. Finally, we show through simulations that our approach leads to significantly higher throughput, even compared to the recent holding-time-aware RWA schemes, which have already been shown to outperform holding-time-unaware models. (C) 2011 Elsevier B.V. All rights reserved.