Joint defragmentation of optical spectrum and IT resources in elastic optical datacenter interconnections

With its agile spectrum management in the optical layer, the flexible-grid elastic optical network can become a promising physical infrastructure to efficiently support the highly dynamic traffic in future datacenter interconnections (DCIs). While the resulting elastic optical DCIs (EO-DCIs) need to serve requests that not only require bandwidth resources on fiber links but also require multidimensional IT resources in the DCs, multidimensional resource fragmentation can occur during dynamic network operations and deteriorate the network performance. To address this issue, this paper investigates the problem of joint defragmentation (DF) for the spectrum and IT resources in EO-DCIs. Specifically, we reoptimize the allocations of multidimensional resources jointly with complexity-controlled network reconfigurations. For the DFoperation, we first study the request selection process and propose a joint selection strategy that can perform the spectrum- and IT-oriented selections adaptively according to the network status. Then, we formulate a mixed integer linear programming model and design several heuristics to tackle the problem of network reconfiguration in the joint DF. The proposed algorithms are evaluated with extensive simulations. Simulation results demonstrate that the proposed joint DF algorithms can significantly reduce the blocking probability in EO-DCIs by consolidating the spectrum and IT resource usages effectively.