Survivable gradual upgrade of SCF edges for communication-intensive workflows in Elastic Optical Inter-Datacenter Networks

Geo-distributed computing requires geo-distributed Datacenters (DC)s to be interconnected through high-speed optical edges for Inter-Datacenter (Inter-DC) communication. Backbone optical networks are evolving towards Elastic Optical Network (EON) and, more recently, Space Division Multiplexing-Elastic Optical Network (SDM-EON) to support the exponential growth of Inter-DC traffic. However, upgrading all network edges to Multi Core Fiber (MCF) will incur huge CAPEX. Therefore, it is imperative to identify a subset of edges for upgrading to MCF to improve Elastic Optical Inter-Datacenter Network (EODCN) performance in terms of communication delay. This enables a trade-off between cost-efficiency and network performance. We propose to form a virtual spanning tree across geo-distributed DC. This ensures a single path between two DCs, thereby eliminating path uncertainties and redundant routing delays. Further, we append chords to the virtual spanning tree to ensure every node is at least two connected, thus ensuring survivability. To carry out virtual tree embedding on physical tree topology, we adopt graph theoretic approach. We explore three centrality metrics, namely edge-betweenness, edge-closeness, and edge-eigenvector, to select a set of important edges for upgrade under the influence of an increasing number of DCs in the network. Simulation results demonstrate that the proposed upgrade strategy reduces Communication to Computation Ratio (CCR) by 79%, 54%, and 41% with three, four, and five geo-distributed DC configurations compared to Single Core Fiber (SCF) network. Techno-economic analysis shows that our proposed hybrid network provides a trade-off between upgrade cost and CCR. It improves CCR by 41.66% while reducing the cost of full MCF upgrade by 45%. Thus, substantial improvements can be achieved through a cost-effective gradual network upgrade.