A method for providing a network service, NS, satisfying a requested availability of a network slice, wherein a network slice instance, NSI, is a concatenation of one or more NS instances and the NS instance is a composition of a plurality of virtual network function, VNF, instances, the method comprising: - obtaining at least one VNF descriptor, VNFD, for a VNF composing the NS, the VNFD being associated with at least one absolute availability value guaranteed according to at least one deployment flavor, DF, wherein the VNFD comprises a plurality of DFs and wherein information concerning an absolute availability value, A VNF-DF is associated to each DF; - obtaining an availability value of a network function virtualization infrastructure, NFVI, on which the VNF is to be deployed; - determining a minimum availability value for a NS instance of the NS greater than a target availability; - selecting a VNF DF and redundancy model, RM, for the VNF DF such that the product of the absolute availability value A VNF-DF of the VNF DF, taking into account the selected RM, and of the availability value of the NFVI is greater than or equal to the minimum availability value for the NS instance; and - instantiating the NS instance by instantiating at least one VNF instance according to the at least one selected VNF DF and corresponding RM; wherein the availability value of the NS instance is greater than a requested availability of the NSI; wherein an availability value of the NSI is calculated as a product of the availability values of the plurality of NS instances in the NSI; wherein the VNFD comprises a plurality of DFs and wherein information concerning which DFs of the VNF are designed to be used for VNF level redundancy is associated to each DF; wherein information concerning a redundancy capability for each DF of the VNF that is designed to be used for VNF redundancy is associated to each DF; and wherein information concerning communication needs of redundant VNF instances is associated to each DF. - obtaining at least one VNF descriptor, VNFD, for a VNF composing the NS, the VNFD being associated with at least one absolute availability value guaranteed according to at least one deployment flavor, DF, wherein the VNFD comprises a plurality of DFs and wherein information concerning an absolute availability value, A VNF-DF is associated to each DF; - obtaining an availability value of a network function virtualization infrastructure, NFVI, on which the VNF is to be deployed; - determining a minimum availability value for a NS instance of the NS greater than a target availability; - selecting a VNF DF and redundancy model, RM, for the VNF DF such that the product of the absolute availability value A VNF-DF of the VNF DF, taking into account the selected RM, and of the availability value of the NFVI is greater than or equal to the minimum availability value for the NS instance; and - instantiating the NS instance by instantiating at least one VNF instance according to the at least one selected VNF DF and corresponding RM; wherein the availability value of the NS instance is greater than a requested availability of the NSI; wherein an availability value of the NSI is calculated as a product of the availability values of the plurality of NS instances in the NSI; wherein the VNFD comprises a plurality of DFs and wherein information concerning which DFs of the VNF are designed to be used for VNF level redundancy is associated to each DF; wherein information concerning a redundancy capability for each DF of the VNF that is designed to be used for VNF redundancy is associated to each DF; and wherein information concerning communication needs of redundant VNF instances is associated to each DF. wherein the availability value of the NS instance is greater than a requested availability of the NSI; wherein an availability value of the NSI is calculated as a product of the availability values of the plurality of NS instances in the NSI; wherein the VNFD comprises a plurality of DFs and wherein information concerning which DFs of the VNF are designed to be used for VNF level redundancy is associated to each DF; wherein information concerning a redundancy capability for each DF of the VNF that is designed to be used for VNF redundancy is associated to each DF; and wherein information concerning communication needs of redundant VNF instances is associated to each DF.