Configuring SBC Edge for Lync E911 with PSAP Callback Number

In this section:

Overview

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

Topology

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:

topology

Scenario

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.

Configuration

Configuring Lync

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:

Verify SBC Edge Added to Topology

Voice Routing

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:

Run Commands

On the Microsoft Lync 2010 Front End Server, launch Microsoft Lync Server Control Panel and configure the Location Policy as shown below:

Configure Location Policy

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:

Configure Associated Normalization Rules

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:

Configure Voice Policy

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:

Verify Relevant Call Route

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:

Lync 2010 Setup

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.

Transformation Table
The wizard creates the following transformation table entry for 911 calls in the outbound direction which are directed to PSAP number as shown below:

Transformation Table

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:

SIP to ISDN Call Route Entry

SIP Profile

The wizard creates the following SIP Profile configured with the ELIN Identifier and PIDF-LO enabled as shown below:

SIP Profile

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):

Emergency Services Configuration

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:

Callback Number Pool

Verification

Lync User Makes a 911 Call

Lync User +1(510)250-2001 dials +911.
Call is routed to the Sonus SBC 1000/2000.
The Sonus SBC 1000/2000 transforms the called party number +911 to the PSAP number 6228 and sends it out to the PSTN.
When the 911 Operator 6228 answers the call, parties go on-hook and terminate the call.

The relevant SIP INVITE message for above call setup is as shown below:

SIP INVITE Message

The Sonus SBC 1000/2000 sends out this INVITE message to PSTN as a ISDN SETUP message as shown below:

INVITE Message Sent Out

Sonus SBC 1000/2000 WebUI > Settings - Call Status Table (in navigation pane) lists the relevant Emergency Call as shown below:

Call Status Table

911 Operator Performs Callback on Previous Call

911 Operator PSAP number 6228 performs a callback to Emergency Callback Number 2020.
SBC Edge Receives the ISDN SETUP message
SBC Edge finds an entry in Callback Status Table for Callback Number 2020 with the relevant Calling Number +1(510)250-2001
SBC Edge routes the call to Lync, and Lync reaches out to the original calling party +1(510)250-2001

The relevant ISDN SETUP message for above call setup, as shown below:

ISDN SETUP Message

SBC Edge Lookup finds the relevant entry in Callback Status Table, as shown below:

Callback Status Table

Sonus SBC 1000/2000 routes the call and send a S_SIP INVITE_ message to the Lync Server, as shown below:

Send INVITE Message to Lync Server

SBC Edge Call Status Table logs this call well, as shown below: