When an emergency call is made from within the internal corporate network, Lotus Sametime Unified Telephony's built-in E911 (Enhanced 911) support provides the capability to forward the call to the gateway served by the appropriate PSAP (Public Safety Answering Point) jurisdiction. By conveying location identifiers registered in the PSAP's ALI (Automatic Location Identification) database, it enables the PSAP operator to retrieve information about the caller's geographical location and place a response call to either the originator of the emergency call or a designated on-site destination.
Lotus Sametime Unified Telephony's Emergency Calling service is applicable to most Emergency regulatory requirements for enterprise systems. For example, the location identification number and callback numbers are provisionable numbers up to 25 digits in length.
The E911 application is embedded in Lotus Sametime Unified Telephony's generic software and is referred to as Emergency Calling
table. Since this application is embedded, there is no separate server and there is no additional cost for implementing the E911 functionality. Performance is directly tied to the resiliency of the system and the remote gateways in the enterprise network.
Lotus Sametime Unified Telephony can support the routing and correct user location reporting for E911 calls made by its users when located on the corporate network.
It is not possible to determine the correct location for endpoints not connected within the corporate network.
When an emergency number is dialled by a device/client, the E911 service looks up an ELIN (Enhanced Location Identification Number) associated with the subscriber's location and the correct route to the PSAP. The ELIN has previously been registered with the PSAP with additional information.
The location can be derived from
the subscriber's DNNote:
can be used for non-mobile subscribers
the subscriber's IP subnet or IP address
typically used for mobile subscribers attached to Lotus Sametime Unified Telephony without intermediate SBC
the subscriber's Location Domain
since Lotus Sametime Unified Telephony 126.96.36.199 the preferred solution for subscribers behind SBCs
As a prerequisite, mobile user agents have to be provisioned for DHCP!
Source Location-based Translation and Routing
The routing of calls in Lotus Sametime Unified Telephony is generally fixed by the subscriber's assigned PNP (Private Numbering Plan). Regardless of the subscriber's physical location - within an office/branch, from a hotel connection or even from home - whenever there is IP connectivity to Lotus Sametime Unified Telephony, the subscriber can authenticate against the system and is bound to the same PNP. Unless exceptions are enforced by other processes or external applications, dialled numbers are always translated in the same way and the resulting calls are routed to the same destinations.
An Emergency Calling implementation obviously requires such an exception: otherwise, emergency dialling could easily result in accessing emergency services that are far from the subscriber's current geographical location.
The emergency call routing is implemented as an extension of the standard PNP number translation:
- depending on the caller's geographical location, a different "route" suffix is appended to the Emergency code (Destination Type: Service; Service: Emergency) configured in the PNP or GNP
- the suffixed Emergency code is retranslated.
The resulting number must route to the appropriate gateway to reach the PSAP.
As mentioned above, the corporate network has to be structured in a way that allows to derive a subscriber's location from its current IP address or location domain.
This permits the traditional PNP-based routing strategies to be used for standard calls, while invoking a more robust, location-based routing strategy when emergency services are required.
Emergency Call ProcessingParent topic: User Telephony
When a subscriber dials an emergency number (typically 911or 112) from within the corporate network, Lotus Sametime Unified Telephony uses the subscriber's current IP address to lookup the associated Emergency Calling data for this subscriber. It retreives an ELIN (Location Information Number) and the Route number for egress to the gateway of the calling user's PSAP (Public Safety Answering Point) jurisdiction.
Direct Return Call from Emergency Center
Lotus Sametime Unified Telephony supports a callback mechanism that allows return calls to be placed from a PSAP (Public Safety Answering Point) directly to the device which placed the emergency call in case the call was interrupted. This works no matter to which callback number the delivered LIN (Location Identification Number) is mapped in the ALI (Automatic Location Identification) database and even with lines that are not provisioned for DID (Direct Inward Dialling). For Return Call from PSAP a special ring tone and display is generated.
Emergency Calling Table
To enable the built-in Emergency Call capability, each BG (Business Group) is provisioned with an Emergency Calling
table that is provisioned using Telephony Control Server Assistant.
The LIN (Location Identification Identifier) conveyed with an emergency call is used by the PSAP (Public Safety Answering Point) to query the ALI (Automatic Location Identification) database for important related data, such as location and callback number.
Subscriber Location Identification
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