Delay-aware Service Function Chain Provisioning with VNF Instance Sharing

Network Functions Virtualization (NFV) offers enhanced programmability and cost-efficiency by replacing hardware middleboxes with versatile Virtual Network Functions (VNFs) on commodity servers. Key challenges in NFV orchestration involve economically placing VNFs and chaining them to meet the requirements of the Service Function Chains (SFCs). Additionally, depending on the VNF functionality, some VNFs may be shared or may not be shared among SFCs. Many existing studies have overlooked the potential benefits of placing shareable VNFs on high centrality nodes, which can boost re-usability and increase SFC acceptance ratios. Vertical scaling of VNF resources, rather than over-allocating for shareable VNF instances, can address resource under-utilization for future SFC admissions. This paper introduces a mechanism for SFC placement, considering both VNF reuse and vertical scalability when deploying SFC requests in the network. The proposed mechanism demonstrates significant improvements in SFC acceptance ratios compared to two baseline schemes, SPH-BC and SPH-VS, as well as a state-of-the-art scheme, SMA-VAA.