LRO (Last Routing Option)

The LRO (Last Routing Option) is sent by the VPC to the Call Server/Routing Proxy and provides the Call Server/Routing Proxy with a “last chance” destination for the call. The LRO may be the Contingency Routing Number (CRN), which is a 24x7 PSAP emergency number, or it may contain a routing number associated with a national or default call center. The content of the LRO will depend on the condition that resulted in the providing of the LRO. Ultimately the usage of LRO routing data for call delivery is based on logic internal to the Call Server/Routing Proxy.

NENA 08-001, NENA Interim VoIP Architecture for Enhanced 9-1-1 Services (i2) (Archived)