Emergency Services Routing Number. This is a unique number assigned to an emergency call in voice peering for routing

the call to the correct PSAP and querying the IPS about the emergency call. For IEN Voice, the ESRN can

be assigned to an ESSID/ESN combination, so  when a call comes in from peering, it will be routed to the PSAP

appropriately. For VoIP, the ESRN is the routing number that represents the selective router.