Cost and Latency Customized SFC Deployment in Hybrid VNF and PNF Environment

The SFC deployment problem has proved to be NP-hard and has attracted great research interests. At present, most existing studies focus on deploying SFC through virtual network functions (VNFs) and few studies involve hybrid VNF and physical network function (PNF) environment. However, in the transition to a comprehensive network function virtualization (NFV) network, hybrid VNF and PNF environment is possible and important. Currently, VNF and PNF both play an important role in today's cloud networks. PNF is far superior in processing speed, but VNF has advantages in flexibility and cost. Using VNF or PNF alone may not meet user needs, affecting user experience and system performance. Hence, this paper studies the SFC deployment problem in hybrid VNF and PNF environment. A cost and latency customized dynamic SFC deployment (CL-SFCD) scheme is proposed. Instead of giving priority to the PNF or the VNF roughly, the CL-SFCD scheme maps network functions to VNFs or PNFs according to the SFC requester's personalized demands to satisfy the demands of different users. It aims to minimize the weighted value of total cost and latency. The CL-SFCD scheme is formulated as a mixed integer linear programming (MILP) model for exact results. Heuristic algorithms are developed to provide an approximate optimal solution in large-scale cloud networks. Numerical results show that the CL-SFCD scheme achieves performance that balances cost and latency based on user requirements than the VNF-only,VNF-GA, and PNF-only deployment schemes.