Energy Efficiency of Voice-over-IP Systems

Voice-over-IP (VoIP) systems are increasingly prevalent in our lives. These systems come in a wide variety of flavors such as desktop-based software applications (e.g., Skype [26]), systems that replace public switched telephony network (PSTN) as the primary line voice service (e.g., Vonage [29]), and more recently, VoIP over smart phones. In November 2010, the number of concurrent VoIP users on Skype exceeded 25million [2]. A study estimates that as of February 2010, there are approximately 110million VoIP hard phone subscribers in the world [11]. Another study estimates that the number of mobile VoIP users will exceed 100million by 2012 [15]. With such a large existing user base of VoIP and expected user growth, and with constantly increasing costs of energy, we ask ourselves what is the energy efficiency of these systems. To answer that question, we gather information about existing VoIP systems and architectures, build energy models for these systems, and evaluate their power consumption and relative energy efficiency through analysis and a series of experiments. The core function of a VoIP system is to provide mechanisms for storing and locating the network addresses of user agents and for establishing voice and video