For allowing a simple and reliable differentiation of UEs behind a GW from an AF side a method for providing access of an User End device (UE) to a service provided by an Application Function (AF) within a network structure is claimed, wherein the UE is authenticated by a Gateway (GW) to which the UE is attached and which provides access to the AF via a Broadband Access Network (BB Access Network). The method is characterized in that the GW informs a state database (SDB) on service flow requests to or from the authenticated UE towards the AF, that the GW additionally sends NAT (Network Address Translation) or NAPT (Network Address and Port Translation) binding information of a respective NAT or NAPT binding created by the GW regarding the authenticated UE and a respective service flow request to the SDB and that the SDB sends the NAT or NAPT binding information or an UE identifier to the AF, so that the AF—after having received the service flow request from the GW—can correlate the authenticated UE with the service flow request. Further an according network structure is claimed, preferably for carrying out the above mentioned method.