Abstract: Voice over Internet Protocol (VoIP) shares the network resources with the regular Internet traffic, and is susceptible to the existing security holes of the Internet. Moreover, given that voice communication is time sensitive and uses a suite of inter-acting protocols, VoIP exposes new forms of vulnerabilities to malicious attacks The VOIP services in developed countries because of the existence of technologies i.e. 3G, 4G and LTE. VOIP is the main issue in developing countries because of the absence of these technologies as several main telecommunication companies are stressing on combining their system with VOIP technologies for providing the enjoyment of these less expensive services to the users. The PLRT technique is proposed for DDos Attack Detection and prevention

Keywords: VoIP, PSJA, PLRT.