x introduced the Chaos Monkey (Bennett and Tseitlin, 2012) fault insertion tool for cloud applications, and made it available in open source for other users. Tools of this type are useful for ensuring that faults can be detected and the system can recover quickly. Maintaining high availability, reliability, and resiliency relies on a continuous cycle of measure- ment and improvement. ONAP is ideally positioned to assist in this regard using ONAP's data col- lection, analytics and events (DCAE) and associated microservices as described in Chapter 7. DCAE affords the opportunity to gather data from many sources that can be correlated and analyzed using advanced analytics and visualization techniques. DCAE metrics are processed by microservices to Architecting the Network Cloud for High Availability proactively detect anomalies, failures, and capacity exhaust. Microservices may be part of a closed loop that is used to automatically mitigate issues, such as by rebooting a VM, re-initiating failed virtualized network functions (VNFs) or spinning up new VNFs. In cases where an issue cannot be automatically resolved, the control loop should notify a network operator via ticketing or alarms SO that the operator can intervene to resolve the issue. The centralized repository in DCAE also offers rich opportunities for data mining and analysis using advanced visualization capabilities such as RCloud (RCloud, 2016) that are made available to users as microservices. 5.4 PUTTING IT ALL TOGETHER: VF CLASSIFICATION AND EXAMPLES This section ties together all the previous material by categorizing different types of VFs and the availability that can be expected. VFs can be classified into the following categories: No site failover, no local redundancy. These VFs are typically associated with transport and network functions, where end users physically terminate their access at a single site. Examples include access routers and line-termination devices. Applications in this cat- egory must maintain state and have very demanding synch