oredundancy for virtualized IMS service platforms. capacity exists. As an example, a deployment may include two virtual zones containing three core sites each and five or six access sites. With this, the geographic deployment of the core sites in each zone follows N + K geo-resiliency where n = 2 and k This configuration can potentially result in a 30% capital expenditure savings over a 1+1 georesiliency strategy. Implementation of a nation- wide subscriber database system eliminates the need for regional deployments. Figure 14.16 shows the change to this configuration as an example. Based on an analysis of performance and latency needs for the VoLTE service, a minimum of five sites are needed to meet latency requirements but this does not meet reliability requirements. A minimum of six sites must be deployed to meet reli- ability as well as latency requirements. Placement or location of the sites is key to meeting the latency requirements. Each site with access network functions distributes new call requests (registration mes- sages) to all three core sites in its georesiliency zone. Under failure of one core site, the other two core sites can handle the load. Each core site operates at 66% capacity under sunny day scenario. Under failure of one site, the remaining two core sites operate at 80% capacity. Virtualized SBCs round-robin requests to the three core sites in its georesiliency zone. With the hybrid implementation of VNFs and PNFs, each core site would use the geographically closest sites for access to the PNFs. 14.4.1.5 Performance The IMS signaling and media VNFs have special requirements for real-time response times and low latencies. A combination of service-level agreement (SLA) constraints defined in service templates and cloud orchestration mechanisms to enable them are used to meet these performance require- ments for virtualized network functions. The cloud is expected to support guaranteed minimal latency of handling signaling messages (e.g., 20 ms), low latency and jitter, and guaranteed high 