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Comprehensive E911 protection requires proper configuration of and integration with all call servers, PBXs and gateways on the network.
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There are two key requirements for E911 - the ten-digit number (ANI/ELIN) that is out-pulsed by the PBX/call server and the Automatic Location Identification data record (ALI/ERL) that is stored in the regional database. For E911 to work, three things need to happen to tie these two components together.
- 1) The PBX/Call Server must be configured to out-pulse the proper ten-digit (ANI/ELIN) number of the 911 caller. This is usually the DID number of the caller.
- 2) Local ISDN-PRI or CAMA trunks must be implemented to send the ANI/ELIN over the Public Switched Telephone Network (PSTN) to the local Public Safety Answering Point (PSAP).
- 3) The regional ALI database must be populated with the ALI records that contain the detailed location information associated to each ANI/ELIN.
When 911 is dialed, the 911 dispatcher at the local PSAP receives the ANI/ELIN, which accesses the regional ALI database to pull up the detailed ALI record defining the exact address and location of the caller.
For purposes of illustration, here is a diagram of how an E911 call is handled when placed from a traditional PBX/Call Server-based phone system equipped with RedSky's E911 Manager.
IP telephony poses some new challenges for location identification. Users can move their phones from place to place or register on an IP phone to access the network. Like traditional phone systems, the key components -- ANI/ELIN and ALI/ERL -- of the E911 system are still required to process the 911 call. However, the question becomes, how can the new location of the user be captured in real time as the IP phone changes locations and is registered on the network?
To support location identification of IP phones on the network, a real-time read/write interface with the call servers is required. This interface serves to capture specific information about the user at the time of registration and then update the call server with the proper ten-digit number for 911 calling. Administrators can choose to define the user's location by the port and network device or by network region.
Currently, only RedSky offers this capability through Network Discovery, a feature available for E911 Manager. This real-time E911 location information management solution is designed to work specifically with IP telephony systems.
Here's how it works: When an IP phone plugs into the network and registers with the call server, E911 Manager is notified. Using Network Discovery, E911 Manager searches the network to find specific information about the location of the IP phone on the network, and associates the phone to an Emergency Response Location (ERL) and ELIN. E911 Manager then updates the call server with the new ELIN so that if 911 is dialed, the call server will out-pulse the correct ELIN which will trigger the correct ALI record at the PSAP.
Many organizations are implementing IP telephony to support branch offices and virtual workers who may be in remote locations. These decentralized workers introduce new challenges for an organization managing E911 including; 1) how to capture the location of these users if they change locations and 2) how to deliver an emergency call to the right PSAP that has responsibility for the caller.
RedSky is helping to solve this issue by working with the leading network infrastructure providers to implement the NENA i2 architecture. NENA i2 provides a method to route a 911 call anywhere in the country using the existing 911 tandem router network that is maintained by the ILECs. In the NENA i2 architecture, RedSky E911 solutions track and find the location of an IP phone and in this role, we function as a Location Information Server (LIS) for the enterprise communications system.
E911 Manager tracks phone movement on the network in real-time through Network Discovery, our new Softphone Location Determination Application (SLDA), or through a web-interface whereby the user proactively designates their location. E911 Manager then updates the VoIP Positioning Center (VPC) so that 911 calls for these users will be routed to the local Public Safety Answering Point (PSAP) serving the user.
The VPC maintains a location database of all phones in the enterprise, whether they are at HQ or in any of the remote offices. When a phone in the branch dials 911, it is sent to the call server at HQ. The call server outputs a unique ELIN that is associated with the location of the caller to the VPC. The VPC retrieves the location record for the ELIN and applies routing instructions for the call to be routed to the local CO and E911 tandem router serving the location of the caller. The VPC delivers the call and also sends the ALI record of the caller to the regional ALI database accessed by the local PSAP. When the call arrives at the PSAP, the location data is displayed on the dispatcher’s screen. This entire process takes place in about 1 second. RedSky’s E911 Manager with LIS plays a critical role in this process by capturing the location information for users as they log on to the network and updating the VPC database with the new location record.
Here's how it works: Users operating from branch offices are designated in the call server as nomadic for 911. When teh user logs on to the network, RedSky LIS prompts the user to designate his/her location. Upon verification with a third-party partner that the location is valid with the Master Street Address Guide (MSAG), RedSky LIS updates the VPC wtih the new location record. 911 calls from this location are configured in the call server to be routed to the VPC and on to the local PSAP serving the caller. Accurate location information is displayed on the local 911 dispatcher's screen.
