Two emerging architectural paradigms, i.e., Software Defined Networking (SDN)
and Network Function Virtualization (NFV), enable the deployment and management
of Service Function Chains (SFCs). A SFC is an ordered sequence of abstract
Service Functions (SFs), e.g., firewalls, VPN-gateways,traffic monitors, that
packets have to traverse in the route from source to destination. While this
appealing solution offers significant advantages in terms of flexibility, it
also introduces new challenges such as the correct configuration and ordering
of SFs in the chain to satisfy overall security requirements. This paper
presents a formal model conceived to enable the verification of correct policy
enforcements in SFCs. Software tools based on the model can then be designed to
cope with unwanted network behaviors (e.g., security flaws) deriving from
incorrect interactions of SFs in the same SFC
