n; notifies the home domain of initial user's access (includes, e.g. CSCF signalling transport address, user ID, etc.; needs further study); may cache access related information (e.g. terminal IP address(es) where the user may be reached, etc.). AH (Address Handling) analysis, translation, modification if required, address portability, mapping of alias addresses; may do temporary address handling for inter-network routing. The UMTS Network and Radio Access Technology 9.3.2 Home Subscriber Server (HSS) The Home Subscriber Server (HSS) serves as the master database for a given user. It contains the subscription related information, to support the network entities actually handling calls/sessions, e.g. it could provide support for the call control servers to com- plete routing/roaming procedures by solving authentication, authorization, naming/ addressing resolution, location dependencies, etc. The HSS holds the following user related information: user identification, numbering, addressing and security information (i.e. network access control information for authentication and authorisation); user location information at inter-system level; the HSS handles the user registra- tion, and stores inter-system location information, etc.; the user profile (services, service specific information. etc.). Based on the above information, the HSS also supports the CC/SM entities of the dif- ferent control systems (CS domain control, PS domain control, IP multimedia control, etc.) offered by a service provider or an operator. HSS (HLR / UMS) Subscription Location information information ....... MSC Server GMSC Server R-SGW Figure 9.7 A generic HSS structure and basic interfaces. The HSS can integrate heterogeneous information, and enable enhanced features in the CN for offering to the application and services domain while hiding the heterogeneity, (see Figure 9.7). The main HSS functionality includes: user control functions required by the IM CN subsystem; the subset of the HLR functionality required by the PS domain; and the CS