IP telephony is not a new service; most companies use it because of its benefits in terms of cost and functionality. However, in most cases, IP telephony channels for transporting voice are not used in a dedicated manner but, instead, voice is carried along with the data packets and is principally in such cases that difficulties are presented in service quality. According to the ITU (International Telecommunication Union) standards, there are parameters that affect the QoS (Quality of Service) in VoIP (VoIP) and during the development of this research these parameters were studied and the results of the simulation of some of them were analyzed