  Service Function Chaining (SFC) is a crucial technology for future Internet.
It aims to overcome the limitation of current deployment models which is rigid
and static. Application of this technology relies on algorithms that can
optimally mapping SFC to substrate network. This category of algorithms is
referred as "Service Function Chaining Resource Allocation (SFC-RA)" algorithms
or "VNF placement (VNFP)" algorithms. This paper presents a survey of current
researches in SFC-RA algorithms. After presenting the formulation and related
problems, several variants of SFC-RA problem are summarized. At last, we
discussed several future research directions.
