Esmaeil Kik Maleki - Faculty of Electrical Engineering Sheikhbahaee University, Isfahan, Iran,
Ghasem Mirjaliliy - Faculty of Electrical and Computer Engineering Yazd University, Yazd, Iran

Voice-over-IP (VoIP) services offer a cheap alternative to the traditional mobile operators to make voice calls. In this paper, we present a comprehensive method for step by step implementation of VoIP services on data networks. This method includes five steps. After determining the requirements of QoS and call distribution features, we should be analyzing network conditions. In this article, we provide a set of qualitative and quantitative criteria to evaluate the network quality of service. The quantity criterions are packet loss ratio and delay that evaluate with new method. On the other hand, in order to calculate the call capacity of the network based on qualitative analysis , Extended_E-model is used. Extended_E-model estimates the Mean Opinion Score (MOS) rate of the voice quality using the measured networkquantities. As a case study, we consider the simulation of an enterprise network connects two branches of the organization. We used the OPNET modeler and MATLAB to simulate the quality and quantity criterions in order to assess the given network.

Voice over IP, Quality of Service, The quantitative and qualitative analysis, Packet loss ratio, Delay ,Mean Opinion Score (MOS), Extended_E-model