t should address the shift from highly reliable hardware to shared commercial off the shelf hardware of sufficient quality 5. The design should meet the real-time response requirements 6. The design should be incrementally and horizontally scalable 7. Transition to a cloud-based design should be transparent to the end user 8. Support for runtime BSS/OSS capabilities should be integrated 9. Relevant security compliance requirements must continue to be supported The following principles are applied to the overall implementation. 14.4.1.3.1 Decomposition of Functions As stated earlier, decomposition of PNFs into granular VNFs is a key principle applied to virtualize IMS service platforms. The decomposition of the IMS network functions is illustrated with a few examples: The SBC is decomposed into signaling access, media access, interworking (IWF), and audio transcoding VNFs to enable more efficient use of resources. The media server is decomposed into the media signaling, media processing, audio trans- coding and video transcoding VNFs to enable more efficient use of resources. The operations, administration, and management (OA&M) functions are separated from the network functions. The load-balancing function is separated from the SBC and I/S-CSCF network functions to allow elasticity. The HSS is decomposed into HSS-FE (front-end) and HSS-BE (back-end) VNFs. The evo- lution of the HSS-BE is to use a scalable cloud-based database provided by the NPaaS layer. 14.4.1.3.2 Decoupling of Subscriber Data Subscriber data are separated from the VoLTE AS and S-CSCF for better scalability and reliability. The evolution of the application subscriber database is to use a scalable cloud-based database pro- vided by the NPaaS layer. 14.4.1.3.3 Decoupling of Long-Lived State Stable session and registration data are separated from the S-CSCF for a better user experience and minimization of registration storms. A state persistence database that can host stable session data that are accessible across georedundant sites is introduced. 