Availability Modeling and Evaluation of a Network Service Deployed via NFV

The Network Function Virtualization (NFV) has been conceived as an enabler of novel network infrastructures and services that can be deployed by combining virtualized network elements. In particular, NFV is suited to boost the deployment flexibility of Service Function Chains (SFCs). In this paper, we address an availability evaluation of a chain of network nodes implementing a SFC managed by the Virtualized Infrastructure Manager (VIM), responsible for handling and controlling the system resources. A double-layer model is adopted, where Reliability Block Diagram describes the high-level dependencies among the architecture components, and Stochastic Reward Networks model the probabilistic behavior of each component. In particular, a steady-state availability analysis is carried out to characterize the minimal configuration of the overall system guaranteeing the so-called “five nines” requirement, along with a sensitivity analysis to evaluate the system robustness with respect to variations of some key parameters.