The IP Multimedia Subsystem (IMS) is a core element of Next Generation Networks (NGNs), which aim at offering users feature-rich and QoS-enabled high-speed multimedia services. With the widespread usage of cloud computing, network function virtualization has emerged as a way to cloudify and virtualize networking resources. However, the complexity of cloud-based virtualized networks requires accurate and efficient monitoring of resources, in order to detect problems and oversee the network's operation. Few monitoring approaches and tools have been proposed in the literature. However, none ...