4.4 NG9-1-1 PSAPs, EIDO, Additional Data & Transitional Elements
Key Takeaways
- An NG9-1-1 PSAP receives SIP calls from the ESRP with location (PIDF-LO) and links to Additional Data, and NENA's NG9-1-1 PSAP requirements document (NENA-REQ-001) describes the functions it should support.
- The Emergency Incident Data Object (EIDO, NENA-STA-021) is a standard JSON structure for sharing incident information among PSAPs, CAD systems, and responders, building on the APCO/NENA EIDD standard.
- Every i3 emergency call carries Call-Info links to at least the ProviderInfo and ServiceInfo Additional Data blocks; an Additional Data Repository (ADR) returns data for those links, and an Identity Searchable ADR (IS-ADR) can be searched by the caller's identity.
- Transitional elements bridge legacy and NG9-1-1 systems: the Location Database (LDB) holds ALI-style records usable by NG elements, and the LSRG, LNG, and LPG interconnect legacy selective routers, originating networks, and PSAPs.
- The Spatial Interface provisions GIS data to the ECRF and LVF, the Forest Guide and DNS help locate services, and NG-SEC (NENA-STA-040) with the PSAP Credentialing Agency (PCA) secures the whole architecture.
4.4 NG9-1-1 PSAPs, EIDO, Additional Data & Transitional Elements
Quick Answer: The NG9-1-1 framework in the ENP Body of Knowledge goes beyond routing and location. An NG9-1-1 PSAP receives SIP calls from the ESRP carrying location (PIDF-LO) and links to Additional Data, and NENA's NG9-1-1 PSAP requirements document (NENA-REQ-001) describes what it should support. The Emergency Incident Data Object (EIDO, NENA-STA-021) shares incident details among PSAPs, CAD systems, and responders. The Spatial Interface (SI) provisions GIS data, while the Forest Guide and DNS help elements find each other. During transition, the Location Database (LDB) and the LSRG, LNG, and LPG gateways connect legacy and NG systems. Additional Data Repositories (ADRs) and Identity Searchable ADRs (IS-ADRs) supply data about the call, caller, and location (NENA-STA-012), and NG-SEC (NENA-STA-040) with the PSAP Credentialing Agency (PCA) secures the architecture.
1. Key NG9-1-1 Terms
| Term | Meaning |
|---|---|
| i3 | NENA's architecture standard for NG9-1-1 (NENA-STA-010) |
| ESInet | The managed IP network that carries NG9-1-1 traffic (3.1) |
| NGCS (Next Generation Core Services) | The set of services that process 9-1-1 calls on the ESInet, such as the ESRP, ECRF, LVF, BCF, logging, and policy functions |
| Functional Element (FE) | A defined i3 component with standard interfaces, such as the ESRP or ECRF |
| ESRP and PRF | The Emergency Services Routing Proxy routes calls, applying rules in the Policy Routing Function (3.3 and 4.2) |
| PIDF-LO | The standard XML object that carries caller location (4.1) |
| Additional Data | Standardized information about the call, the caller, or the location that supplements location |
| EIDO | The standard object for exchanging incident information |
| LNG, LPG, LSRG | Gateways connecting legacy networks, legacy PSAPs, and legacy selective routers to NGCS (4.3) |
IP Networking Essentials
NG9-1-1 runs on standard internet protocols: IP for addressing and routing, DNS to translate names into addresses and help locate services, SIP for call signaling, RTP for media, HTTPS web services for data exchange, TLS for encryption and authentication, and NTP for time synchronization (7.3). Understanding these basics helps PSAP managers work with IT staff, vendors, and ESInet providers.
2. The NG9-1-1 PSAP
An NG9-1-1 PSAP is built to accept calls and data natively over IP:
- Call delivery: The ESRP delivers a SIP call carrying the caller's location (by value or by reference) and Call-Info header fields that point to Additional Data.
- Multimedia: Voice, real-time text, message-based text, and (as policy allows) video and images.
- Location and data retrieval: Call handling equipment displays location, dereferences location URIs when needed, and retrieves Additional Data from ADRs.
- Status to the network: The PSAP reports its state (for example, normal, overloaded, or closed) and queue status so ESRPs can apply routing policy and send calls elsewhere when necessary.
- Transfers and conferencing: Transfers commonly bring the receiving agency into a conference (bridge), so location and Additional Data can follow the call.
- Logging: Signaling, media, and events are recorded through the Logging Service (7.3).
NENA-REQ-001 (NG9-1-1 PSAP Requirements) lists functional requirements for these capabilities, and NENA-STA-010 defines the interfaces. PSAPs whose equipment is not yet IP-capable connect through a Legacy PSAP Gateway (LPG).
3. The Emergency Incident Data Object (EIDO)
- What it is: A standard JSON data structure, defined in NENA-STA-021, that describes an emergency incident: incident identifiers, linked calls, location, incident type, notes, responding units, and status.
- Where it came from: It builds on the APCO/NENA Emergency Incident Data Document (EIDD) standard (APCO/NENA 2.105.1-2017), and NENA-STA-024 defines how EIDOs are conveyed between systems.
- Why it matters: When a call is transferred or an incident is shared across agencies, the EIDO carries the incident details with it, reducing re-questioning and re-typing. It also supports CAD-to-CAD exchange and logging (7.2).
4. Spatial Interface, Forest Guide, and DNS
- Spatial Interface (SI): The functional element that takes authoritative GIS data from 9-1-1 authorities and provisions it to the ECRF, LVF, and mapping systems, applying validation so bad data does not reach live routing (8.3).
- Forest Guide: Knows which ECRFs are authoritative for which geographic areas, so an ECRF that receives a query outside its coverage can find the right one. A National Forest Guide lets different ESInets route to each other (4.2).
- Domain Name System (DNS): Resolves the names of ESInet elements and services to addresses. Because nearly every NG9-1-1 interaction starts with a name lookup, DNS needs the same redundancy and security as the call path itself.
5. Transitional Elements
| Element | Role During Transition |
|---|---|
| Location Database (LDB) | Holds ALI-style records (including shell records used to reach wireless MPCs/GMLCs and VoIP positioning centers) in a form that NG9-1-1 elements can use, supporting ECRF-based routing and NG9-1-1-capable CPE before originating networks provide location from their own LIS |
| Legacy Network Gateway (LNG) | Converts calls from legacy (TDM) originating networks into SIP with location for the ESInet |
| Legacy PSAP Gateway (LPG) | Converts NG9-1-1 calls into a form that legacy PSAP equipment can receive, including emulated ALI queries |
| Legacy Selective Router Gateway (LSRG) | Connects legacy selective routers with NGCS, so calls and transfers can move between areas still on E9-1-1 and areas already on NG9-1-1 |
As originating service providers deliver calls natively in SIP with PIDF-LO and Additional Data, the need for the LDB and gateways declines.
6. Additional Data: ADR and IS-ADR
NENA-STA-012 standardizes three kinds of Additional Data:
- Data about the call: the service provider, the type of service, the device, and subscriber information.
- Data about the caller: for example, medical or accessibility information the caller has chosen to share.
- Data about the location: for example, building information, floor plans, or on-site hazards.
How Additional Data Travels
- Every i3 emergency call must include at least two Call-Info header fields whose URIs resolve to Additional Data, and the required blocks are ProviderInfo and ServiceInfo. Together with the PIDF-LO, these give the PSAP at least the information legacy ALI provided.
- A URI can point to a block carried in the body of the SIP message, or to an external source.
- An Additional Data Repository (ADR) is the database that answers those external URIs, returning the Additional Data block in response to an HTTPS request.
Identity Searchable ADR (IS-ADR)
Some Additional Data is held by an organization that is not in the call path, such as a service that stores a caller's medical profile. An IS-ADR lets authorized agencies and elements search by the caller's identity (a SIP or tel URI) to find that data. Because a potential caller can choose where to store their information, there may be several IS-ADRs, listed in a registry, and agencies query them all. Access requires credentials traceable to the PCA, and privacy rules limit who can see the data.
7. NG-SEC and the PSAP Credentialing Agency
- NG-SEC (NENA-STA-040.2-2024) sets security requirements for NG9-1-1 entities (9.1).
- The PSAP Credentialing Agency (PCA) is the root of the public safety PKI; its certificates authenticate elements, agencies, and ADR queries (3.2 and 9.1).
- The Border Control Function (BCF) protects the ESInet edge (3.2).
8. Operational Traps & ENP Exam Watch
- ADR vs. IS-ADR: An ADR answers a URI supplied with the call; an IS-ADR can be searched by the caller's identity when the data holder is outside the call path.
- Minimum Additional Data: ProviderInfo and ServiceInfo are the required Additional Data blocks on every i3 call.
- EIDO vs. EIDD: The EIDD is the APCO/NENA conceptual standard; the EIDO (NENA-STA-021) is the JSON implementation used in NG9-1-1.
- LDB Is Transitional: The LDB bridges legacy ALI data into NG9-1-1 and fades as providers deliver location natively.
- The SI Protects Routing: GIS data reaches the ECRF and LVF through the Spatial Interface, not by direct edits to live routing data.
In NENA i3, what does an Identity Searchable Additional Data Repository (IS-ADR) provide that a standard ADR lookup does not?
Which NENA standard defines the Emergency Incident Data Object (EIDO), and what is it used for?
What is the role of the Location Database (LDB) during the transition to NG9-1-1?