Fig. 4. Number of reallocations vs. mean requested number of slots per
over time. The aim of these algorithms is to minimize the
number of WSSs, placed at the input ports of speciﬁc network
nodes, required to mitigate the crosstalk effect, and thus the
spread of an attack, as well as to minimize the required light-
path reallocations between different trafﬁc scenarios. Thus,
the proposed technique reduces both the network capex and
opex, by minimizing the required number of WSSs and the
number of lightpath reallocations upon variations in the trafﬁc
demand. Performance results demonstrate the effectiveness of
the heuristic algorithm in terms of computational time, as
the proposed heuristic performs close to the results of the
mathematical formulation, while outperforming the complete
Future works will explore decomposition techniques for
the mathematical formulation so as to address larger network
problems. In addition, online reconﬁgurability of the network
with samples from the distributions of the connections will be
This work has been partially supported by the European
Union’s Horizon 2020 research and innovation programme
under grant agreement No 739551 (KIOS CoE) and from the
Government of the Republic of Cyprus through the Directorate
General for European Programmes, Coordination and Devel-
opment. It was also partially supported by the Cyprus Research
and Innovation Foundation under project CULTURE/AWARD-
YR/0418/0014. This article is based upon work from COST
Action CA15127 (Resilient communication services protecting
end-user applications from disaster-based failures RECODIS)
supported by COST (European Cooperation in Science and
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