Acquiring a Location
Topic Last Modified: 2012-06-06
In a Lync Server 2013 E9-1-1 deployment, each internally-connected Lync or Lync Phone Edition client actively acquires its own location. After SIP registration, the client furnishes all the network connectivity information that it knows about itself it in a location request to the Location Information service, which is a web service backed by a replicated SQL Server database. Each central site pool has a Location Information service, which uses the network information to query its records for a matching location. If there is a match, the Location Information service returns a location to the client. If there is not a match, the user may be prompted to enter a location manually (depending on location policy settings). The location data are transmitted back to the client in an Internet Engineering Task Force (IETF) standardized XML format called Presence Information Data Format Location Object (PIDF-LO).
The Lync Server client includes the PIDF-LO data as part of an emergency call, and this data is used by the E9-1-1 service provider to determine the appropriate PSAP and route the call to that PSAP along with the correct ESQK, which allows the PSAP dispatcher to obtain the caller’s location.
The following diagram shows how a Lync Server client acquires a location (except for the third-party client MAC address–based location method):
For a client to acquire a location, the following steps must take place:
The administrator populates the Location Information service database with the network wiremap (tables that map various types of network addresses to corresponding Emergency Response Locations (ERLs)).
If you use a SIP trunk E9-1-1 service provider, the administrator validates the civic address portions of the ERLs against a Master Street Address Guide (MSAG) database maintained by the E9-1-1 service provider. If you use an ELIN gateway, the administrator ensures that the PSTN carrier uploads the ELINs to the Automatic Location Identification (ALI) database.
During registration or whenever a network change occurs, an internally-connected client sends a location request that contains the client's discovered network addresses to the Location Information service.
The Location Information service queries its published records for a location, and, if a match is found, returns the ERL to the client in PIDF-LO format.