A emergency call service mechanism on SIP Internet telephony system

Today the world is undergoing a massive shift from the traditional PSTN to all-IP-based Internet telephony, implying an eventual replacement of the PSTN with VoIP sooner or later. However FCC's decision to "require VoIP service providers to supply E911 capabilities to their customers" imposes legal controls. Internet telephony users have an expectation to be able to initiate a request for help in case of an emergency. Unfortunately, the existing mechanisms to support emergency calls that have evolved within the PSTN, are not appropriate to handle evolving IP-based telephony service. In this paper, we suggest mechanism for emergency calls placed by the public using SIP-based VoIP system.