Availability Assessment of IP Multimedia Subsystem in an NFV-based Environment

Network Function Virtualization (NFV) is considered one of the most influencing concepts in modern telecommunication frameworks, since it has the merit of transposing (and adapting) the virtualization paradigms from the computer world to the networking context. An instance of NFV is known as a Virtual Network Function (VNF), and represents a virtualized abstraction of a network element such as a router, a firewall, a load balancer, deployed in a virtualized environment. Actually, complex infrastructures, such as IP Multimedia Subsystem (IMS), a framework in charge of providing advanced multimedia services, can benefit of a virtualized deployment by implementing its constitutive elements as VNFs. The resulting architecture is a vIMS that, in this work, is characterized in terms of availability. More specifically, relying on a failure/repair model of a generic vIMS entity (modeled as a three-layer structure composed of hardware, hypervisor and software), we propose an availability assessment of the whole system by means of Stochastic Reward Networks framework.