Virtual Network Function Placement Method for Evolving Network Slices based on Salience

Network function virtualization (NFV) technology enables us to deploy a distinct network slice composed of various virtualized network functions (VNFs) required for a given service, such as video on demand (VoD) and Internet-of-things (IoT). As a result, application service providers (ASPs) can easily deploy and provide their services to end users (EUs) by leasing resources formed as network slices. However, as the user population or the network traffic volume fluctuates, the capacity of network slices has to be adjusted dynamically. It requires to take decision about placing NFs in appropriate locations so that the quality of services (QoS), such as transmission or processing latency is guaranteed while optimally utilizing the reserved resources. One can address the above challenge by solving an optimization problem such as integer linear programming. However, the optimization problem takes much time to solve. In this paper, we propose a network function placement algorithm based on salience, which is one of characteristic metrics of links in graphs. Our objectives are two folds: keeping the slice reconstruction cost low, and avoiding the cases of QoS degradation. The simulation results show that our scheme performs equally well for different sizes of slices (i.e., the number of EUs). When slices are reconstructed with our scheme in a 200-node network, we found that the network reconfiguration costs are low and almost the same value for various sizes of slices.