Voice has been traditionally carried by the circuit-switched PSTN. In VoIP, voice is packetized into IP packets and carried over the Internet. Several computer-to-computer VoIP systems (e.g., Google Talk and Skype) offer free voice service nationally and internationally. It’s likely that voice service on newer smartphones will be solely on VoIP. Therefore, VoIP is having a profound impact on the PSTN/cellular systems, as it seems to be slowly killing traditional voice over the PSTN and probably over the cellular system. Will the legendary PSTN be phased out?