ESRP (Emergency Service Routing Proxy)

An i3 functional element which is a SIP proxy server that selects the next hop routing within the ESInet based on location and policy. There is an ESRP on the edge of the ESInet. There is usually an ESRP at the entrance to an NG9-1-1 PSAP. There may be one or more intermediate ESRPs between them.
 * Originating ESRP: The first routing element  within the NGCS (NG9-1-1 Core Services). It receives calls from the BCF at the edge of the ESInet.
 * Terminating ESRP: The last ESRP for a call in NGCS.