Network Function Virtualization (NFV) aims at bringing the
benefits of virtualization to network middleboxes (routers, firewalls, Intrusion Detection Systems, . . . ). In the last few years the NFV use-case,
initially hampered by the poor performance of traditional virtualized I/O and network stacks, has prompted the design of several frameworks,
all trying to provide a fast network for VMs and/or containers. These
solutions share many common ideas, but also differ in performance, flexibility, portability, amount of specialized hardware required and/or software to be rewritten, attention to energy consumption issues, and so
on. In this survey we focus on the NFV data-path, as opposed to the
orthogonal control-path. We define a set of desirable features for NFV
data-paths and use them to compare a selection of the most promising
and/or widely used NFV frameworks. No single solution is optimal for
all the features, so our survey may prompt for further research in this
area.