ABSTRACT: This document provides the requirements for the functions and interfaces that need to be supported at the Emergency Services Routing Proxy (ESRP). The ESRP is defined as the routing proxy that is authorized by an appropriate emergency services authority to accept and route emergency calls on their behalf.

The ESRP plays a special role in the National Emergency Number Association (NENA) i3 architecture as the routing proxy that is present in an Emergency Services IP Network (ESInet). The NENA architecture assumes the existence of an ESInet that is separate (either physically or logically from the general IP-based network used for non-emergency applications. The ESRP provides routing needed for emergency calls within the ESInet.

The requirements in this document address the functions that need to be supported by the ESRP. The ESRP is expected to accept incoming emergency session requests, query for routing information, apply any specified policies to determine alternate routing, and use this information to route the emergency session request to the next ESRP or Public Safety Answering Point (PSAP).

This document also addresses the signaling interfaces and processes that must be supported by the ESRP. The ESRP provides call routing and routing query functions and it needs interfaces to support these functions. This document also provides operations, performance, and security guidelines for the ESRP.

Issue 3 includes the following:

• Support for call queues
• Routing to PSAP administrative lines
• Details regarding retrieval of location information when a location reference is received (location de-reference)
• Additional details for the Policy Routing Function (PRF).