Package-based services are affected by different network parameters and conditions that can deteriorate the quality of the transmitted services, especially those that are provided in real time. In this paper, result of an undergraduate research project, the bases for the construction of a QoS model are defined for a video call on an IMS network, specifying the most adequate parameters to estimate its QoS, the infrastructure used, and the tests developed. The results indicate the possibility of improving the QoS by applying the horizontal scaling technique over the IMS Core of the network since, in the vertical scalability, no major improvements were observed when increasing the physical resources of the virtual machines where the Core IMS was installed. Also, the bandwidth that complies the conditions of the quality parameters such as packet loss, delay, and jitter, to provide a good quality video call service is 640 kbps.