ng the data users are sending, placing data transmission gaps, or even delivering to users' handsets that do not allow tethering without additional subscription to the service. The 3GPP in the Release-10 version has defined advanced and explicit features for IPv6 prefix delegation (see Section 4.4.6). When the prefix delegation is in use, the 3GPP network also 'acknowledges' the fact that the UE is providing routing services, and thus connectivity services, for other devices. Calling that setup Split-UE no longer makes much sense (as the UE is no longer 'split'), but an official term for the UE that supports Dynamic Host Configuration Protocol version 6 (DHCPv6) Requesting Router (RR) role has not yet been decided. 2.7 Subscription Management Databases and Other Backend Systems We have now examined almost all of the network elements in the GPRS and EPS network architectures. It is time for an overview of the different registers in the 3GPP system. These include the HLR and Authentication Center (AuC), the HSS, and the EIR. Finally, we will have a quick look at the other backend systems not shown in the 3GPP architecture pictures, but that are nevertheless vital for a 3GPP network deployment to work. 2.7.1 Home Location Register and Authentication Center The Home Location Register (HLR) is a GPRS network element, which is in the GPRS architecture upto 3GPP Release-4, when it is replaced by the HSS. However, the HLR Basics of the 3GPP Technologies is a subset of the HSS, and sometimes, confusingly, also referred to in the specifications also beyond the Release-4. However, it can also be seen as the part of the HSS that is responsible for the data network connectivity services in GPRS and EPS. The HLR is the database that stores information about the subscriber. It includes infor- mation that is relatively static, including security, authentication, authorization, and service provisioning information. In addition, the HLR stores more dynamic information related to, for example, mobility management - for instance, HL