Fog computing is conceiving an Internet where general purpose compute is ubiquitous, in turn this is providing new infrastructures for Network Functions Virtualisation (NFV). However, current NFV designs focus on the Cloud, resulting in broken and suboptimal deployments when deploying to the Fog. Through a case study with preliminary results, this paper presents the e ectiveness of Siren: a new prototype platform designed as a tool to deploy and manage Virtual Network Functions in Fog environments.