A network entity (NE1; NE2) comprising means for acquiring information about a virtual network function and means for calling it; characterized in that said means for calling for it comprise: - a function table (FT1; FT2) for storing multiple function entries (FE1,..., FEm,..., FEn), each function entry having a number (VNF_Number) referring to a different virtual network function (VNF1,..., VNF1m), so that said virtual network function can be called by means of said function entry, and each function entry (FEm) containing at least the following information: • a first pointer (P1 in p_vnfInputParams) that enables the network entity (NE1; NE2) to pass input parameters to a currently called virtual network function (VNF1m; VNF2m); • a second pointer (P2 in p_vnfOutputParams) that enables the network entity (NE1; NE2) to retrieve output parameters from a currently called virtual network function (VNF1m; VNF2m), said output parameters resulting of the processing of a current data packet; • a third pointer (P3 in p_vnfPacketParams) that enables the network entity (NE1; NE2) to pass the current data packet content and related information to the currently called virtual network function (VNF1m; VNF2m); - three internal metadata placeholders for respectively storing at least the following information: • first information (in metaInputParams) that enables the network entity (NE1; NE2) to pass, to the currently called virtual network function (VNF1 m; VNF2m), input parameter values of said current virtual network function (VNF1 m; VNF2m), such that this latter can modify said current data packet content according to said input parameters; • second information (in metaOutputParams) that enables the network entity (NE1; NE2) to retrieve output parameters from the currently called virtual network function (VNF1m; VNF2m); • third information (in metaPacketParams) that comprise characteristics of the current data packet; - means for receiving said three pointers (P1, P2, P3) from a software defined network controller. - a function table (FT1; FT2) for storing multiple function entries (FE1,..., FEm,..., FEn), each function entry having a number (VNF_Number) referring to a different virtual network function (VNF1,..., VNF1m), so that said virtual network function can be called by means of said function entry, and each function entry (FEm) containing at least the following information: • a first pointer (P1 in p_vnfInputParams) that enables the network entity (NE1; NE2) to pass input parameters to a currently called virtual network function (VNF1m; VNF2m); • a second pointer (P2 in p_vnfOutputParams) that enables the network entity (NE1; NE2) to retrieve output parameters from a currently called virtual network function (VNF1m; VNF2m), said output parameters resulting of the processing of a current data packet; • a third pointer (P3 in p_vnfPacketParams) that enables the network entity (NE1; NE2) to pass the current data packet content and related information to the currently called virtual network function (VNF1m; VNF2m); • a first pointer (P1 in p_vnfInputParams) that enables the network entity (NE1; NE2) to pass input parameters to a currently called virtual network function (VNF1m; VNF2m); • a second pointer (P2 in p_vnfOutputParams) that enables the network entity (NE1; NE2) to retrieve output parameters from a currently called virtual network function (VNF1m; VNF2m), said output parameters resulting of the processing of a current data packet; • a third pointer (P3 in p_vnfPacketParams) that enables the network entity (NE1; NE2) to pass the current data packet content and related information to the currently called virtual network function (VNF1m; VNF2m); - three internal metadata placeholders for respectively storing at least the following information: • first information (in metaInputParams) that enables the network entity (NE1; NE2) to pass, to the currently called virtual network function (VNF1 m; VNF2m), input parameter values of said current virtual network function (VNF1 m; VNF2m), such that this latter can modify said current data packet content according to said input parameters; • second information (in metaOutputParams) that enables the network entity (NE1; NE2) to retrieve output parameters from the currently called virtual network function (VNF1m; VNF2m); • third information (in metaPacketParams) that comprise characteristics of the current data packet; • first information (in metaInputParams) that enables the network entity (NE1; NE2) to pass, to the currently called virtual network function (VNF1 m; VNF2m), input parameter values of said current virtual network function (VNF1 m; VNF2m), such that this latter can modify said current data packet content according to said input parameters; • second information (in metaOutputParams) that enables the network entity (NE1; NE2) to retrieve output parameters from the currently called virtual network function (VNF1m; VNF2m); • third information (in metaPacketParams) that comprise characteristics of the current data packet; - means for receiving said three pointers (P1, P2, P3) from a software defined network controller.