Lync 2013 Call Forwarding Integration to an ITSP

This document outlines the steps required to ensure that calls forwarded from Lync 2013 to the ITSP contain a phone number that the ITSP will accept.

The Original Problem

As some SIP Trunk providers require that calls originate from the number range the ITSP has assigned to the customer, it is necessary to ensure that all calls from SBC to the ITSP have a FROM, DIVERSION or P-Asserted-Identity (PAI) number which is from the ITSP-assigned range.  For instance, if the carrier has assigned a customer 574-1000 to 574-9999, the calling number, diversion, or PAI for any SBC --> ITSP call must fall within that range.

However, calls that are forwarded by Lync 2013 back to the SIP Trunk contain the calling number (FROM header) of the original calling number rather than the Lync 2013 number.  In this case, the ITSP refuses to route the call because the calling number is that of the original caller, not an ITSP-assigned number.

The following call flow diagram depicts the scenario where the call forwarded by Lync 2013 does not have History-Info

Call Forwarded by Lync 2013

Configuration Details

Configuration Overview

Configure Lync 2013 Server to supply History-Info on forwarded calls, then use the SBC to convert the number in the History-Info header to a SIP header the ITSP will accept for calling authorization.

The following call flow diagram shows a Lync Server configured to supply History-Info on forwarded calls:

Lync Server Configured

Lync 2013 Required Configuration

The Lync Server Trunk Configuration must be configured to supply History-Info on forwarded calls

To enable Lync Server to Send History-Info, navigate to "Voice Routing", "Trunk Configuration" and check the "Enable forward call history" option

Trunk Configuration

SBC 1000-2000 Configuration

The SBC can be configured to supply Diversion, From, and/or PAI headers to the ITSP.  Use the sections below to provide the desired header.

Diversion header

The SBC will automatically map Lync's History-Info header into a Diversion header when sending the call to the ITSP.  No other configuration is required in order to send a Diversion Header to the ITSP.

Modifying the outgoing Diversion Header number is achieved by simply making an entry in the Transformation Table.   The Transformation Entry below removes the +1 from the Diversion Header.

Modify Outgoing Diversion Header Number

From header

The incoming History-Info header is automatically mapped into the SBC's transformation table Redirecting Number IE.  To send the History-Info number as the From (calling) number, add the entry below to the appropriate transformation table.

Set the Calling Number using History-Info:

Set Calling Number

P-Asserted-Identity (PAI) header

A SIP Message Manipulation (SMM) permits setting the PAI number using the History-Info number.  Several steps are required:

1. In the transformation table, set SG User Value 1 IE from the Redirecting Number IE.
2. Create a SMM Rule to insert SG User Value 1 into the PAI header.
3. Add the SMM Rule to the ITSP Signaling Group.

Step 1:  Transformation Table Configuration

• In the transformation table, set SG User Value 1 IE from the Redirecting Number IE

  Transformation Table Configuration

  

Step 2:  SIP Message Manipulation Configuration

• Create a SMM Rule to set the URI User (the PAI number) in the P-Asserted-Id header.

  Create SMM Rule

  
   

   

• Configure the Add/Edit to retrieve the number from SG User Value 1.

  Configure Add/Edit

  

Step 3:  Add the SMM Rule to the ITSP Signaling Group

• Add the newly created SMM Rule to the Outbound Message Manipulation section of the ITSP Signaling Group.

  Add SMM Rule

  

Additional Information