re is limited and failure of any one site in this model will not result in loss of service or degradation of service to an entire region. Virtual Zone subscriber Failure of Overflow Home to "Overflow" growth in NW Virtual Zone impacts NW Virtual Zone subscribers only VNFs for VoLTE Central HSS Subscriber data available to all virtual zones Virtual Zones for capacity augmentation and avoiding nationwide disasters Capacity exists in Central Virtual Zone. FIGURE 14.7 Virtual zones. Building the Network of the Future 14.3 PIVOT TO SDN/NFV: METHODOLOGY, PROCESS, SKILLS Delivering services using SDN/NFV requires a change in mindset, methodology, processes, a pivot of skills as well as cross-organizational alignment to deliver on the promise of virtualization for ser- vice platforms. A significant emphasis on training and educational sessions for SDN/NFV, ONAP, and change in methodology and processes is required to enable a scalable model for designing and implementing virtualized services. 14.3.1 SERVICE CREATION SDN/NFV enables creating and rolling out services quickly. The ONAP service design and cre- ation environment (covered in Chapter 7) supports the specification of real-time services in near real-time. It provides the ability to specify custom parameters and policies for service instantia- tion within the cloud. The service designer can make specific selections from the VNF, SNS, and NPaaS services. These are all represented in catalogs that are available to the service designer to create services that form the basis of a "service catalog." End-to-end services are created using resources from the various catalogs and are exposed as "product catalogs" to external customers/ service designers based on policies that determine combinations of services and resources that have been certified and can be used to create a product. The service templates contain details of a service including its chaining logic, business policies, engineering rules, installation recipes, service poli- cies, dimensioning of virtual resourc