A framework for 911 service in a PBX LAN

In the public switched telephone network (PSTN), 911 (emergency) services are handled by a dedicated, point-to-point analog network infrastructure. In contrast, 911 in IP telephony is constrained by IP´s flat addressing scheme and dynamic IP address assignment, best-effort service model and inherent dynamicity in network topology connectivity. To serve crucial E911 needs of accurate assistance dispatch with callback facility in IP telephony, the existing model from analog telephony is not applicable. We investigate ways of resolving location information of an IP telephony 911 caller and propose a novel approach to convey geographic location information parameters of connected hosts by extending the DHCP protocol. The case scenario of voice over IP (VoIP) in local area networks (LAN) is used as the basis for our approach and specifically, University of Missouri Kansas City´s (UMKC) VoIP network has been considered for possible deployment of this approach.