There is described a method for providing a Virtualized Network Function ( VNF ) according to Network Service ( NS ) requirements . The method comprises selecting an on - boarded VNF descriptor ( VNFD ) from a VNF catalogue , configuring parameters of the selected on - boarded VNFD according to the requirements of the NS and instantiating a VNF according to the configured on - boarded VNFD . There is also described a method for providing a Network Service ( NS ) . The method comprises selecting an on - boarded NS Descriptor ( NSD ) from an NS catalogue , modifying NSD information of the selected on - boarded NSD and instantiat ing the NS according to the modified on - boarded NSD .