LIS

Introduction

• This interface responds to standard-compliant HELD requests to return the latest location in standard XML schemas per the NENA i3 architecture.
• It retrieves a Location Object using the HELD (HTTP-Enabled Location Delivery) Protocol according to IETF RFC 5985.
• Location objects are in the format of PIDF-LOs, Presence Information Data Format Location Objects (RFC 5139).
• This interface is for use by authorized public-safety entities, to pull location data for emergency calls

LIS Standards Info

At its core, a LIS HELD interface is simply a webserver that responds to HTTP requests with XML. This is extensively defined in a set of IETF RFCs, which also specify the XML schemas defining the data formats for passing information back and forth.

• HELD
  • RFC 5985
• Device URIs in HELD
  • RFC 6155
• Location Conveyance in SIP Signaling
  • RFC 6442
  • RFC 6753
• PIDF-LO
  • RFC 4119
  • RFC 5139
  • RFC 7459
• Additional Data Links
  • RFC 7852 Section 6.2
• Circle and radius in geodetic responses
  • http://www.opengis.net/pidflo/1.0
  • http://www.opengis.net/gml
• Schemas for all are aggregated here

These documents contain all the information needed to build a HELD client conformant to the standards (or have references to other RFCs that contain missing information).

Implementation

The recommended i3 mechanism is to pass dereferencing URIs around in SIP signaling. For the purposes of over-the-top integration using these mechanisms, RapidSOS proposes the following:

1. Query the LIS with HELD with the caller’s identity (phone number) to retrieve location information
2. Repeat LIS location queries periodically for the duration of the call

Limitations/Caveats

Some caveats should be kept in mind when considering using the i3 mechanisms:

• LIS location de-referencing will only return the latest location available at the time of the query, and not the entire location history stored by RapidSOS

Authentication Options
This interface is authenticated via basic authentication POST /oauth/token

Additional Considerations
Additional information for consideration for LIS - (NENA i3 Location Information Server) includes the following:

• Does not support OAuth2.0
• Does not receive text-to-911 data
• Does not receive Z coordinate data
• RSOS does not provide location data for landlines
• Devices must be iOS12+ or Android 4.0+ to provide location. Microsoft and Blackberry devices do not send location data
• The partner must have the caller ID to query the API per spec requirements POST /location