  Queueing-network models are developed for enhanced and next-generation 911
(E911 and NG911) systems, which capture both their cyber-components
(communications, data-processing) and physical-world-elements (call takers,
vehicle dispatch). The models encompass both the call-processing and dispatch
functions of 911, and can represent the interdependencies between multiple
PSAPs enabled by NG911. An instantiation of the model for a future NG911 system
for Charlotte, North Carolina, is developed and used to assess performance
metrics. Representation of cyber-threats (e.g. Distributed Denial-of-Service
attacks) within the queueing-network model is undertaken. Based on these
representations, the model is used for analysis of holistic threat impacts, as
a step toward risk and vulnerability assessment for future emergency response
systems.
