Effectiveness of SIP messages on SIP server

Voice over Internet Protocol (Voice over IP, VoIP) is one of a family of communication protocols, and transmission technologies. It is used for delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks. Session Initiation Protocol (SIP) is a signaling protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP). There are several DoS attacks by which we can disturb SIP server. In this paper, more importance has been given to DoS attack by flooding of different SIP-messages. A little work is done to analyze the performance of SIP server and quality of ongoing VoIP calls under DoS attacks. We show the utilization of CPU and memory during the multiple simultaneous calls. We have done our study using a customized analysis tool that has the ability to synthesize and launch flooding of different SIP messages. We define the performance metrics to measure the quality of VoIP calls under DoS attack. We have developed some programs and integrated them in a real SIP test bed environment to measure the performance of SIP server and quality of VoIP calls under DoS attack. Our measurements show that a standard SIP server can be easily overloaded by simple call requests. It also shows that simple call request can degrade quality of ongoing calls.