Author: Jason Sloan | Senior Cloud Consultant and Teams Voice Lead
In some countries and regions, it is illegal to bypass the Public Switched Telephone Network (PSTN) provider to lower long-distance calling costs.
Though illegal, some individuals still utilize a toll bypass, which diverts calls from PTSN to Internet Protocol (IP) networks, where the call runs at no charge. To prevent a toll bypass, it is important to utilize Location Based Routing.
Throughout this article, learn more about Location Based Routing and how it is implemented within Microsoft.
What is Location Based Routing?
Location Based Routing (‘LBR’), at its core, is a feature that prevents toll bypass. It ensures that long distance calls go in and out of the PTSN through a local carrier and adheres to the specific users' regulations.
Microsoft’s Location Based Routing Feature
The Location Based Routing feature from a Microsoft standpoint was first released with Lync Server 2013 and has now since been carried over to Microsoft Teams.
If you have experience deploying LBR in the Lync Server and Skype for Business days, you will see similarities with Microsoft Teams as the same “logic,” we will call it, is used with Teams. That logic is nothing more than simply identifying users and SBCs (Session Border Controllers) locations via IP addressing and applying policies to such.
To learn more about LBR and calling scenarios that apply and do not apply to LBR users, visit the following Microsoft doc's site: https://docs.microsoft.com/en-us/microsoftteams/location-based-routing-plan
This article also assumes you understand Direct Routing. If not, please review this document as well: https://docs.microsoft.com/en-us/microsoftteams/direct-routing-landing-page
Location Based Routing in Action
Now, let’s get an understanding of LBR from the perspective of a few illustrations.
In the first illustration, we show that User 1 or User 2 is trying to call the US. You can see the signaling of the user tells Teams “Try and use the SBC in the United States to make a call to Chicago.”
This would be against regulation as you tried to enter the PSTN local to Chicago, rather than out the local PSTN in New Delhi. This is considered “Toll Bypass.”
The second illustration shows the appropriate path, in which it tells Teams “If you want to call the US, you need to go out your local gateway, through the PSTN then into Chicago.” This meets regulation and ensure tolls are going to be collected within India.
The third illustration simply shows how all calls should traverse the PSTN within the user’s respective locations. Each location needs its own PSTN Gateway/SBC connected to the PSTN.
So now that we understand LBR, logically, the next question is...how do we set it up?
Setting up Location Based Routing
Out of the gate, it’s important to define the following requirements:
The Site within the Region
Network Subnet at each site
Trust external internet IP address for each site
The PSTN Gateways/SBCs in each site
*Any PBX’s that may be required to ensure Teams users can call PBX users, such as Cisco
Users in each site
Voice Routing Policies
Now, let’s look at the fictitious scenario box detailing our setup in India, which is a heavily regulated country for LBR. The scenario box ensures traffic flows how we expect in illustration 3 shown above. **Image is clickable to expand
Once those requirements are gathered, you can begin configuring the sites and users for LBR. Inside of the scenario box are associated commands that should be run to set up LBR based on requirements. To summarize, here are the steps
Gather all the requirements
Configure PSTN Usages
Configure Online Voice Routing Policies for each site
Enable LBR for each network site
Enable LBR for each gateway/SBC
Grant the CsOnlineVoiceRoutingPolicy to users that must have LBR applied
Also, grant this to any user who roams to India or an LBR configured site
Enable the AllowCallingPreventTollBypass flag within the Teams Calling Policy for LBR Users
This also includes any roaming users
When users are enabled for LBR travel to sites enabled for LBR, the LBR enabled site takes precedents and forces calls through the local SBC
*If you have a required connection to a PBX for internal calling, you should have a separate Teams Registered FQDN/IP or separate SBC connecting to that PBX. In this scenario, you DO NOT apply LBR to that registered SBC. In the documented scenario above, NDPBX.contoso.com represents this SBC connecting to a Cisco System in New Delhi as illustrated below: