A method for interfacing a network entity (NE) in a software defined network (SDN) and a virtual network function (VNF) by acquiring information about said VNF, calling for said VNF using a function table (FT1; FT2) stored in the NE storing multiple function entries (FE1,..., FEm,..., FEn), each function entry referring to a different virtual network function (VNF1, ..., VNF1m), and each function entry (FEm) containing at least the following information: €¢ a first pointer (P1 in p_vnfInputParams) for acquiring input parameters required by the VFN; €¢ a second pointer (P2 in p_vnf0utputParams) for providing output execution results to the NE; €¢ a third pointer (P3 in p_vnfPacketParams) for accessing the current data packet in order that the called VNF processes said data packet.