chnology interface. Thus, service providers or operators can choose to register their subscribers to the v-CSCF in networks that also support CAMEL, just as in GSM today. However, when the visited network does not support CAMEL or the capabilities to support a given service, then it will be possible to provide call control in the h-CSCF. This would mean that either the user is registered with the h-CSCF directly, or if the user is regis- tered in the v-CSCF, then the v-CSCF will be capable of forwarding the call set up re- quest to the h-CSCF. The latter will also apply to service providers or operators that choose to have all of their subscribers (including roamers) supported by the h-CSCF. 9.8.1.1 Implementation Options of the VHE/OSA Figure 9.16 illustrates the main components to realize the Virtual Home Environment (VHE). Notice that the applications servers need a set of enablers and management. Applications Appl. Appl. Server Server Service Appl. Appl. Business Appl. Network Server Support Appl. Server Server Management Systems/ Monitoring Manager Personal Service Management IP-Infrastructure Integration (backbone) Manager Portal User Profile System Directory Configuration Billing Manager System Service Enablers Charging Notification Application Support Servers Support Support Service Capability Servers CAMEL Access Bearers Internet Network Access Network Figure 9.16 IP based service network overview and its relation to core and access networks. The two key options to follow include: Personalization Subscribers can customize their own service set and its corre- sponding interaction. Transparency Subscribers can see seamlessly the same service features across network boundaries and between terminals regardless of their location. To further illustrate the implementation, we can divide the IP-infrastructure service network into functional areas as illustrated in Figure 9.17. Clearly we have the service enablers as shown in Figure 9.16, then personal service management, service network management, and applicati