A next-generation network utilizes a three-tier, cascading fault approach
to providing emergency stand-alone (ESA) switching in a circuit-to-packet
(C2P) network. Calls that are placed to destination numbers which are
connected to the same local network device are completed even when
connectivity with a community network level has been interrupted, while
calls that are placed to destination numbers which are connected to the
same community are completed even when connectivity with a gateway media
controller has been interrupted.