 to collect data from the cloud infrastructure for session tracing. Examples of protocols required for session tracing include signaling protocols such as SIP, HTTP, H.248, and diameter and media/messag- ing protocols such as real-time transport protocol (RTP), message session relay protocol (MSRP). 14.2.1.1.4 Infrastructure as a Service The infrastructure as a service (IaaS) layer provides the cloud infrastructure or network functions virtualization infrastructure (NFVI) (referred to as AIC in Chapter 4), which comprises the physi- cal hardware and operating environment. Separate physical storage servers are also provided along with the compute nodes. The computing resources, for example, CPU and memory are abstracted by Building the Network of the Future the hypervisor layer. The hypervisor layer makes virtual resources available for deploying virtual- ized applications. The hypervisor that will be used for the SDSF is an OpenStack supported KVM hypervisor. The hypervisor abstracts the physical resources in the form of VMs. VMs are indepen- dent of each other and offer dedicated virtual resources to the virtualized applications. Applications along with tools can be loaded onto the VMs and executed in support of a virtualization project. Refer to Chapter 4 for the IaaS, which is provided by the NFVI. 14.2.1.2 Virtual Service Control Loop Framework The virtual services control loop framework enables on-demand rapid and reliable instantiation of real-time services on a cloud infrastructure. It supports near real-time correlation of events for policy-based advanced elasticity and auto recovery. The framework includes instantiating the ser- vice components and the connectivity required to all virtual and physical components of the service. The framework enables pivoting to an operational paradigm where services can be automatically scaled as well as recovered from software and hardware failures. The virtual service control loop framework aligns with the Open Network Automation Platform (ONAP) framework (discussed in