Service Function Chain Graph Transformation for Enhanced Resource Efficiency in NFV

Service Function Chain (SFC) embedding optimization is crucial for the resource efficiency of Network Function Virtualization infrastructures (NFVI). Nevertheless, high utilization and/or fragmentation levels of a NFVI can significantly restrict the feasible solution space of any SFC embedding method, leading to inefficient SFC placements, or even inhibit SFC embedding. To rectify this problem, we stress on the need for SFC graph transformation (SFC-GT), i.e., explore the potential of SFC graph expansion prior to its embedding. SFC-GT aims at decomposing virtualized network functions (VNFs) into multiple instances with lower resource demands, facilitating their placement onto the NFVI. In this respect, we discuss the trade-off between embedding flexibility and complexity, in the context of SFC-GT. We formulate SFC-GT as a multi-objective optimization problem and design a mixed-integer linear program (MILP) to tackle it. Our simulation results demonstrate notable resource efficiency gains when SFC-GT is utilized prior to SFC embedding.