n 100 k to 100 million subscribers and beyond. It is the decoupling of the application logic from the data that enables a very efficient scalability of the ngHLR. The ngHLR supports an open standard interface based on DAP/LDAP (v3). 6 The interface provides a number of provisioning methods and can integrate with interface compliant provisioning systems. There are no proprietary features in the ngHLR provisioning interface. CORBA Clients or SOAP/XML (define is the OSS section) interface can be used in the provisioning system infrastructure by which provisioning application can communicate to the ngHLR. 8.2.5.1.2 Benefits ngHLR provides a number of benefits which in turn reduce OPEX and CAPEX. Some key benefits are: One single subscriber database for GSM, UMTS, HSPA which eliminates the need for purchasing additional platforms. One subscriber database will accelerate the introduction of new services. Less ngHLR sites means less OpEx. No proprietary interface means no vendor dependency for operators. 8.2.5.2 3GPP GAA Authentication A number of applications share a need for mutual authentication between the clients and servers. The authentication is necessary in order for users to gain access to various services offered by the networks. Today's networks employ costly and ineffective application-specific authentication mechanisms. To cater for this need and shortcoming 3GPP has specified a structure called Generic Authentication Architecture (GAA) in TR 33.919 [18]. The TR 33.919 gives an overview of the different mechanisms that mobile applications can rely upon for authentication between server and client (i.e., the UE). Additionally it provides guidelines related to the use of GAA and to the choice of authentication mechanism in a given situation and for a given application. Figure 8.15 provides the overview of inter-relation of GAA building blocks. The heart of GAA consists of Generic Bootstrapping Architecture (GBA) and certificates. The GBA core specifications are described in TS 33.220 [19], TS 24.109 [20] and 