Software Rejuvenation for Higher Levels of VoIP Availability and Mean Time To Failure

Recently, Voice over Internet Protocol (VoIP) has become an evolutionary technology in the communication area. Despite its innovative nature, VoIP faces some problems such as resource degradation on the server supporting the system. In this paper a VoIP system consisting of the main parts that can affect the VoIP service such as SIP servers, routers, ISP internet service provider, firewalls and finally the electrical power is studied. To counteract the aforementioned problems concerning servers we propose to adopt software rejuvenation. Rejuvenation is a proactive technique that can be periodically adopted to prevent software failures. Our main aim is to determine how. VoIP availability and reliability can be affected by rejuvenation. Continuous Time Markov Chain (CTMC) is used to model system's function while asymptotic availability and Mean Time To Failure (MTTF) when rejuvenation is performed are determined. Moreover we are interested on the optimal rejuvenation policy that improves system's performance.