Through network function virtualization (NFV), telecom providers aim to flexibly re-use generic-purpose hardware to provide services on-demand and in an agile way. Service function chaining is becoming the preferred model to describe the characteristics of the packet-processing network functions which, together, form these services. NFV allows for network function embedding freedom, creating new dynamics between providers and the users requesting services. Users want this freedom to optimise the performance of their requested services, while providers aim to optimise their resource cost with it. This trade-off is heavily influenced by how the available infrastructure is exposed to the users. In this paper, we present an infrastructure abstraction model for network, compute and storage resources that exposes the infrastructure in an abstracted manner. We use this abstraction to propose a solution for the placement freedom trade-off problem by studying its relation with metrics that capture both the user's and the provider's aspects. We conclude with a heuristic that determines the right abstraction for particular scenarios.