This article is to describe the necessary configuration steps for SBC Edge Emergency Services for Lync E911 - PSAP Callback
Public Safety Answering Point (PSAP) Callback is an important SBC Edge feature supporting 911/E911. In the LYNC E911 architecture, the Emergency Location Identification Number (ELIN) number is the PSAP call back number that the emergency service operator can call to reach the original 911 caller. This article explains how to configure the SBC Edge for E911 Calback functionality in a LYNC deployment.
Best Practice Use Case
In this best practice example, we will be configuring a SBC Edge node for the Lync E911 with a PSAP callback number in following topology:
- Be sure that the SBC Edge is defined and configured in the Microsoft Lync Server 2010 Topology and Control Panel.
- Complete the 911 specific settings in Microsoft Lync Server 2010 Control Panel.
- Configure the SBC Edge node as a gateway in Microsoft Lync Server 2010 - SBC EdgeGateway - PSTN topology:
- With Lync E911 enabled
- With Emergency Callback Number as 2020.
- With PSAP Number as 2020.
- Have Lync Client make a successful E911 call
- Verify the call is successful
- Have Lync Client make a E911 call, then disconnect before the 911 Operator answers the call.
- Verify that 911 Operator can make a successful callback to the PSAP Callback number
- Verify that SBC Edge redirects the PSAP callback call to the Lync client who initiated the E911 call.
Verify that SBC Edge is added to Microsoft Lync Server 2010 Topology and Control Panel as directed by Microsoft Lync Server 2010 Deployment Guides and it appears correctly in Microsoft Lync Server 2010 Control Panel as shown below:
On the Microsoft Lync 2010 Front End Server, launch Lync Server Management Shell and run the following commands to enable "PDIFLOSupport" and to create a Location Information Server (LIS) Subnet as shown below:
On the Microsoft Lync 2010 Front End Server, launch Microsoft Lync Server Control Panel and configure the Location Policy as shown below:
On the Microsoft Lync 2010 Front End Server, launch Microsoft Lync Server Control Panel and configure the Associated Normalization Rules with 911 dialing as shown below:
On the Microsoft Lync 2010 Front End Server, launch Microsoft Lync Server Control Panel and configure the Voice Policy with 911 route as shown below:
On the Microsoft Lync 2010 Front End Server, launch Microsoft Lync Server Control Panel and verify that relevant Call Route contains the 911 pattern match as shown below:
Configuring SBC Edge
Lync 2010 Setup
- Launch your preferred explorer and logon to SBC Edge WebUI.
- Click the Tasks tab.
- In the left navigation menu, click* Lync 2010 Setup* (in the Microsoft UC Setup section).
Fill-in the setup fields and click Apply as shown in below example:
E911 Specific Settings on SBC Edge
Upon a successful Lync 2010 Setup run, wizard will create your SBC Edge node for the minimum required settings for SIP to ISDN and ISDN to SIP calls. In addition, Emergency Service will be enabled and relevant configuration will be set. In this section, we will only verify the Emergency Service related configuration fields settings.
The wizard creates the following transformation table entry for 911 calls in the outbound direction which are directed to PSAP number as shown below:
SIP to ISDN Call Route Entry
The wizard creates the following SIP to ISDN Call Route Entry for 911 calls in the outbound direction which are directed to relevant ISDN Signaling Group as shown below:
The wizard creates the following SIP Profile configured with the ELIN Identifier and PIDF-LO enabled as shown below:
Emergency Services Configuration
The wizard creates the Emergency Services configured with 24 hours Call Status Duration (default) as shown below (note that this is a 1 through 24 hour configurable item):
Callback Number Pool
Make sure that the Callback Number Pool is created with the Callback number (2020 in this example) and with the PSAP number (6228 in this example) as shown below:
Lync User Makes a 911 Call
- Lync User
- Call is routed to the Sonus SBC 1000/2000.
- The Sonus SBC 1000/2000 transforms the called party number
+911to the PSAP number
6228and sends it out to the PSTN.
- When the 911 Operator
6228answers the call, parties go on-hook and terminate the call.
The relevant SIP INVITE message for above call setup is as shown below:
The Sonus SBC 1000/2000 sends out this INVITE message to PSTN as a ISDN SETUP message as shown below:
Sonus SBC 1000/2000 WebUI > Settings - Call Status Table (in navigation pane) lists the relevant Emergency Call as shown below:
911 Operator Performs Callback on Previous Call
- 911 Operator PSAP number
6228performs a callback to Emergency Callback Number
- SBC Edge Receives the ISDN SETUP message
- SBC Edge finds an entry in Callback Status Table for Callback Number
2020with the relevant Calling Number
- SBC Edge routes the call to Lync, and Lync reaches out to the original calling party
The relevant ISDN SETUP message for above call setup, as shown below:
SBC Edge Lookup finds the relevant entry in Callback Status Table, as shown below:
Sonus SBC 1000/2000 routes the call and send a S_SIP INVITE_ message to the Lync Server, as shown below:
SBC Edge Call Status Table logs this call well, as shown below:
Emergency Calls in Alarm View
Every time an Emergency 911 call or PSAP callback call is received on the SBC Edge, SBC Edge throws an alarm with its relevant information as shown below: