Service Function Graph Design and Mapping for NFV with Priority Dependence

Network Function Virtualization (NFV) explores the virtualization technologies to offer Network-as-a- Service (NaaS) through connected virtual network functions. The network operations that were previously performed by specialized hardware are consolidated as software-based virtual network functions (VNFs). These VNFs can be implemented in the telecom clouds with high volume servers, switches and storage. With the NFV orchestration, a service function graph (SFG) can be built to provide network services. In this paper, we study how to efficiently construct the SFG from a set of VNF requests and map the SFG onto the substrate network while considering the priority dependence between the VNFs. We define the problem of service function graph design and mapping (SFG_PD) and propose an SFG_PD mapping with dependent directional acyclic graph (SFG_DAG) algorithm. The proposed SFG_DAG algorithm can jointly construct the VNFs graph and map VNFs onto the substrate network while minimizing the bandwidth consumption in the substrate network. Our simulation and analysis show that accommodating the VNFs based on the requested bandwidth yields the best performance in terms of the total bandwidth consumption.