Monday, June 24, 2013

Location-Based Routing without Inbound Call Restrictions

The February 2013 Update for Lync Server 2013 (CU1) added location-based routing to the Lync Enterprise Voice featureset. As described on Technet and various other blogs, location-based routing was designed to function in countries where routing calls over the WAN is not allowed.

Countries like India apparently have rather strict telecom laws saying any calls that exit the country must exit via the PSTN.  For instance, imagine your company has a Lync deployment in India and Canada.  As I understand it, if a user sitting in India wanted to call a Canadian PSTN number, it couldn't save on international toll charges by routing the call to Canada via the corporate WAN and exit to the PSTN via the Canadian Lync deployment. The converse situation would also not be allowed.  Whether this is because India wants the international toll charge revenue or for monitoring purposes, I don't know.

Prior to Lync 2013 CU1, companies faced with these requirements would be OK when users never moved from their assigned location.  For instance, if a Canadian user never went to the India office, and the India users always stayed in India, they would never run afoul of the rules. If a Canadian user did travel to India, their Canadian voice policy would still apply (unless the administrator moved the user temporarily to the India Lync server).  Their calls would route over the WAN to the Canadian Lync server, which is not allowed by India telecom rules.

Location-based routing was obviously added to Lync to deal with the "India problem".  You can see this in the Technet documentation on how to setup location-based routing.  All the examples use India, and if you follow the documentation explicitly, you will have an India telecom compliant Lync deployment.  If our hypothetical Canadian user travels to the India office, their calls will use the India Lync deployment, rather than use the WAN for least cost routing.  Inbound calls to the Canadian user's Canadian phone number will go to voicemail, because letting him take the call via the WAN would run afoul of the India dial rules.

So, this got me thinking. What if we want to setup location-based routing, but not worry about whether or not inbound calls can route over the WAN?  I can think of many situations where location-based routing is desirable. Any place where you have lots of mobile people going to different offices can benefit from location-based routing, especially in environments where bandwidth back to the user's home pool is lacking.

Luckily, I'm working on a Lync 2013 deployment that has that exact scenario in mind. The company has many mobile users who travel to far-flung offices with poor WAN conditions.  I wanted to see if we could implement location-based routing for this company, but without the restrictions on inbound call routing imposed if you follow the Technet documentation to the letter.

The documentation has you setting up all your sites and subnets, and then running the following commands (as per

  1. New-CSVoiceRoutingPolicy to create the routing policies and the PSTN usages assigned to it
  2. Set-CSNetworkSite to enable location-based routing for the site via -EnableLocationBasedRouting:$TRUE, and to assign the previously created voice routing policy
  3. Set-CSTrunkConfiguration to assign network sites and enable routing restrictions on the PSTN trunk, using -EnableLocationRestriction:$TRUE.
  4. Set-CSVoicePolicy to enable location-based routing for the users assigned to that policy, using -PreventPSTNTollBypass:$TRUE

We setup location-based routing as per the documentation with only ONE key difference...we didn't enable location-based routing on the trunks as per the examples given.  When running Set-CSTrunkConfiguration, we left out the -EnableLocationRestriction:$TRUE setting.

Technet's documentation on this particular setting seems to indicate not setting -EnableLocationRestriction to $TRUE would make location-based routing not work. In actual fact, this is the setting that stops inbound PSTN calls from working while a user is at a site where call routing restrictions apply (like India).

The setting that I THOUGHT would have allowed inbound calls across the WAN to work was Set-CSVoicePolicy -PreventPSTNTollBypass:$FALSE.  This setting is actually the one that controls which users will get location-based routing applied to them.  Setting it to false disables location-based routing for the users of that voice policy, as indicated by the wording on the location-based routing setup page. It does not actually prevent PSTN calls from reaching users over the WAN, as the Technet documentation on the command indicates.

We've tested this setup and it works as we had hoped it would. When users go to remote sites, their outbound calls use the local PSTN egress point, but inbound calls to their PSTN phone number still routes to them properly.

So, in conclusion, if you want to enable location-based routing without inbound call restrictions, don't use Set-CSTrunkConfiguration -EnableLocationRestriction:$TRUE, or conversely, use Set-CSTrunkConfiguration -EnableLocationRestriction:$FALSE if you've already set it to $TRUE.

1 comment:

  1. Hi Ken,

    Nice job going into this and explaining the fine points that TechNet missed. I put this in place for our India office and it seems to work. However, when they start a conference and add external parties, the conference fails. The diagnostic reason is 12004 "user is not authorized to call the specified number or none of the routes have a valid gateway configured". The conference MCU is located at the main site stateside. Any ideas? Thanks,