Voice over Internet Protocol (VoIP) is a form of voice communication that uses audio data to transmit voice signals to the end user. VoIP is one of the most important technologies in the world of communication. Most of the research survey of Voice over IP security mainly discussed about the security issues like denial of service, service abuse, implementation bugs and miss configurations, numerous threats and vulnerabilities present in VoIP systems. But in terms of providing good services through VoIP doesn't considered in previous researches and there is no effective methodology to provide effective QoS over VoIP. In this paper, the authors are proposing a new methodology which concentrates on all the security issues to provide effective QoS in VoIP.