On the Risk-aware Connection Defragmentation in OCS-based Data-center Networks

The dynamic traffic changes in an optical circuit switching based data-center network (ODCN) can make the utilization of its optical connections fragmented, degrading the efficiency of service provisioning in the ODCN. Consequently, connection defragmentation becomes imperative. However, consolidating traffic onto fewer connections may unilaterally add the risk of bandwidth contention and undermine ODCNs’ robustness against unexpected traffic bursts. To address this issue, we propose risk-aware connection defragmentation (RA-cDF), which explores the topology flexibility of ODCN to consolidate traffic such that the active optical connections through optical circuit switching (OCS) switches can be minimized together with the risk of future bandwidth contention on remaining connections. We formulate a mixed integer linear programming (MILP) model to address the RA-cDF problem exactly, followed by a heuristic to solve it time-efficiently. Extensive simulations confirm the effectiveness of our proposals.