Testing Lync LBR with Polycom VVX Business Media Phones

Location Based Routing (LBR) was introduced in the Lync2013 Feb 2013 CU making it possible to restrict the routing of calls between VoIP endpoints and PSTN endpoints based on the location of the parties in the call. Location-Based Routing is part of the Lync Server 2013 Enterprise Voice infrastructure and when enabled, allows Lync to enforce call authorization rules on whether calls can be routed to PBX or PSTN endpoints based on the Lync caller’s geographic location. This helps to enforce PSTN Toll-Bypass in countries where regulations prohibit it. Even with least cost routing enabled, the location based routing policies will take precedence. This article walks briefly through the setup and configuration of LBR and tests it against the Polycom VVX family of Lync IP Phones.

In this lab, we use a standard edition Lync server configured with an Asterisk PBX to simulate a PSTN connection. The diagram of this setup is shown below:

As shown in the diagram, we have the same Lync user Edina that is logged into a Polycom VVX400 and VVX600 phone running the latest UCS firmware. The VVX400 phone is in the same subnet as the Lync SE server and the Asterisk PBX. The VVX600 is in a different subnet. When we configure the SIP Trunk to Asterisk to enable LBR, it is expected that the VVX400 will be able to reach the X-Lite softphone at ext3001, which simulates a local user calling a local PSTN gateway, In contrast, the same user when travelling to a different country with a different IP subnet on the VVX600 trying to call the same X-Lite softphone ext3001, the call will be blocked to prevent PSTN Toll-Bypass.

Configuring the SIP Trunk to Asterisk
As mentioned we are using Asterisk v11.14 to emulate a PSTN gateway. Asterisk can be downloaded here and in this lab I'm running the 64-bit version of AsteriskNOW 6.12 on Windows Server 2012 Hyper-V. The steps to configure an Asterisk server and create the SIP Trunk to Lync was covered in this article back in Sep 2012 and therefore won't be repeated here. Although the article was written for AsteriskNOW2.0, much of the same concepts still apply in the new version with only minor changes to get a basic SIP trunk working with the necessary inbound/outbound routes. We also won't be covering in detail the steps to configure Enterprise Voice in Lync as there are already much guidance available publicly.

Instead, in this section we focus on the LBR configuration itself. As a starting point, we first create the Trunk using Topology Builder:

The PSTN Gateway associated with this trunk is the Asterisk PBX. We use TCP 5060 for the listening port on Asterisk as well as the listening port on the mediation server which in this case is just the Lync SE server. Note that the default TCP listening port on Lync mediation server is 5068, not 5060 so this must be changed on the mediation server properties otherwise Topology Builder will not allow us to configure the Trunk to use 5060.

On the Asterisk side, we configure the SIP Trunk to use TCP 5060 next hop to the Lync FE. This can be seen on the diagram on the right. Note the parameters need to be entered in the PEER Details box as shown and the USER Details should be left blank.

In the inbound Routes we configure Asterisk to ring the extension 3001 so that the X-Lite phone registered to this extension will ring when Lync clients make a call through this trunk

On the asterisk console, we can see the SIP Peer shows status of Lync as OK :

To enable users to use this route, we make sure there's a Voice Route "AXAPSTNRoute" that corresponds to this PSTN Gateway and assign the route for all users in the "Global" Voice Policy with PSTNUsage "Local" :

To make sure the trunk and route works, we test calling extension 3001 from both VVX phones and see that the call goes through for both cases. This is the case of least cost routing where LBR is not yet enabled.

Configuring and Enabling LBR
First we need to create a new VoiceRoutingPolicy that specifies the PstnUsage that uses the gateway. In this lab the cmdlet to do this is

New-CsVoiceRoutingPolicy -Identity "AXALBR" -PstnUsages "Local"

Then we enable the Global voice policy to PreventPSTNTollBypass using the cmdlet:

Set-CSVoicePolicy -Identity "Global" -PreventPSTNTollBypass $true

Next we proceed to enable LBR on the network site and trunk in AXATower which has the subnet 10.222.208/24 using the cmdlet:

Set-CsNetworkSite -Identity "SG AXA Tower" -EnableLocationBasedRouting $true -VoiceRoutingPolicy "AXALBR"

The Trunk Configuration also needs to be modified to enable LBR for the Network Site using the cmdlet:

Set-CsTrunkConfiguration -Identity Global -EnableLocationRestriction $true -NetworkSiteID "SG AXA Tower"

Finally we enable LBR for the global routing configuration:

Set-CsRoutingConfiguration -EnableLocationBasedRouting $true

This sequence of cmdlets are shown below:

Testing LBR
For this test, we have two Polycom VVX phones signed in with the same Lync account as Edina. The VVX410 is on the same subnet as the PSTNGatway as shown below. As expected calls to the X-Lite softphone at x3001 goes through successfully:

Looking at the SIP trace, we see the call gets routed via the Asterisk PSTN Gateway to reach the X-Lite softphone x3001:

The VVX600 is on a different subnet as the PSTNGatway as shown below. As expected calls to the X-Lite softphone at x3001 DOES NOT go through successfully:

From the SIP Trace we see that the call cannot route via the PSTN Gateway because LBR is enabled: