IP Telephony has been adopted to replace the traditional circuit switch networks in various environments. Government Emergency Telephony Service (GETS) is one of the critical services currently provided in the traditional circuit switch network. GETS supports personnel from different organizations performing their critical missions including Incidence Response and Prevention, National Security, and Emergency Preparedness. Because of the convergent infrastructure for both voice and data, how to provide GETS over IP is one of the challenges for IP Telephony to prove its flexibility and strength for large-scale critical services. In this study, we explore many aspects for providing IPbased GETS, such as availability, security, interoperability, and reliability. Based on IP Multimedia Subsystem (IMS) architecture, the requirements along with some analyses and recommendations are outlined to meet the strict demands for GETS in different convergent paradigms.