 Logic (DNSaaS) (DBaaS) Security IP Interconnect Carriers Media/ Dynamic User Security Association DB Mediation Routing Control ITF DB (DBaaS) (DBaaS) DB (DBaaS) (DNSaaS) (DBaaS) FIGURE 14.5 Decomposition of network functions (example). 14.2.1.1.2 Shared Network Services While the virtual service framework drives instantiating VNFs on a per-service basis, there are some common service VNFs that need to be instantiated for use by all services. These common service VNFs make up the shared network services (SNS) layer of the SDSF. The pre-instantiated common services/VNFs are exposed for use by other services via reference APIs (e.g., RESTful API to retrieve/update customer profile information from the subscriber database). They can be used by the service provider as well as third-party services. Included in this layer are 1. IP carrier interconnect, which a telecom operator would set up with other carriers indepen- dently of the services. 2. Routing logic. 3. Routing databases and local copies of industry databases or interfaces to those databases. 4. Customer profile database that can be used by all services to retrieve and update customer- profile information. This is a scalable cloud-based database that can be used to mine cus- tomer-specific information to provide value-added services. 5. Mediation function and database that are used by services to send call detail record (CDR) information. Besides providing data for billing purposes, this database serves as the basis for information used for correlation and analysis to detect certain faults. 6. Regulatory service that interfaces with the government regulatory systems. 7. Common Domain Name Server (DNS) instantiated and used for inter-VNF communica- tion and for communication from devices external to the network. 14.2.1.1.3 Network Platform as a Service The network platform as a service (NPaaS) layer exposes a set of common cloud services that can be used by real-time services. It enables use of a common set of technologies that can be instantiated and managed 