| Summary: | The sub-tree-based optical multicasting scheme provides a spectrum-efficient approach to providing emerging multicast services in optical data center networks. Moreover, multicast services are usually replicated and maintained in multiple geographically distributed data centers to improve its access efficiency and reliability. Therefore, the source data centers of all constructed sub-trees for a multicast demand are not confined to a common data center and can be independently determined by the requested distribution. In this paper, we study the problem of multicast service provisions while leveraging multicast service backups among multiple geographically distributed data centers. A novel distributed sub-tree-based optical multicasting (DST-OM) scheme is proposed. An integer linear program model is developed for the DST-OM scheme with the aim of minimizing the total spectrum consumption of all multicast demands in elastic optical data center networks. We also define the minimum spectrum sub-tree (MSST) problem for the DST-OM scheme. Two modulation-level-aware heuristic algorithms are developed to address the MSST problem. Numerical results show that the DST-OM scheme achieves higher spectrum efficiency and lower blocking probability than the conventional common source sub-tree-based optical multicasting scheme and the single-tree-based optical multicasting scheme.
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