I. Introduction
Today, network and telco providers are benefiting from the Service Function Chaining (SFC) paradigm, which allows to easily create and deploy novel services through a series (namely, a chain) of concatenated network components [1], [2]. They are often designed by exploiting softwarized technologies such as virtualization, microservices, containerized environments, that provide a flexible and handy habitat for diverse telco frameworks [3], [4]. Among such frameworks we focus on the IP Multimedia Subsystem (IMS), which, embracing the service chaining concept, has been elected both by standardization groups [5] and by the industry world [6], [7] as the ideal intermediary between legacy networks and 5G-based solutions.