Voice over Internet Protocol (VoIP) phone systems are common telephony technologies for multimedia sessions and voice communication over sophisticated networks of Internet Protocol (IP), for example over Internet. These VoIP phone systems are becoming a common sight of communication protocols in enterprises. In comparison to its conventional counterpart, PSTN, Voice over IP is capable to offer many advantages. For businesses, it offers a highly verstile breadth of servives and features, highly quality audio communication, easy-to-manage services, and reduced cost for distant calls.