Network function virtualization (NFV) envisions the use of cloud computing and virtualization technology to reduce costs and innovate network services. However, this paradigm shift poses the question whether NFV will be able to fulfill the strict performance and dependability objectives required by regulations and customers. Thus, we propose a dependability benchmark to support NFV providers at making informed decisions about which virtualization, management, and application-level solutions can achieve the best dependability. We define in detail the use cases, measures, and faults to be injected. Moreover, we present a benchmarking case study on two alternative, production-grade virtualization solutions, namely VMware ESXi/vSphere (hypervisor-based) and Linux/Docker (container-based), on which we deploy an NFV-oriented IMS system. Despite the promise of higher performance and manageability, our experiments suggest that the container-based configuration can be less dependable than the hypervisor-based one, and point out which faults NFV designers should address to improve dependability.