Understanding the Updated Microsoft Teams Dialing Mechanism

23 Oct Understanding the Updated Microsoft Teams Dialing Mechanism

Understanding the Updated Microsoft Teams Dialing Mechanism

In the ever-evolving landscape of digital communication, changes are inevitable. One such significant change has been introduced by Microsoft Teams regarding how dialed phone numbers are matched to users. This update stems from a previous issue where some users with Direct Routing plans were unable to receive Public Switched Telephone Network (PSTN) inbound calls. Microsoft announced this change under the communication reference MC487014, initially published on December 17, 2022, and updated on August 30, 2023. This blog post aims to explain these changes in detail and offer guidance on what you need to do to prepare.

The Problem: Inability to Receive PSTN Calls

Before delving into the new changes, let’s understand the issue that prompted this update. Users with Direct Routing plans were experiencing difficulties in receiving PSTN inbound calls. Microsoft identified that a feature allowing extension numbers had been disabled, leading to the problem. As a temporary solution, Microsoft re-enabled the feature and advised users to follow guidelines detailed under MC487014 to prevent recurrence.

The Update: Reverse Number Lookup (RNL) Changes

What Is Reverse Number Lookup?

Reverse Number Lookup (RNL) is a feature that enables Microsoft Teams to match incoming or dialed phone numbers with the user accounts configured with similar numbers. You can refer the below screenshot

The Scope of Changes

The changes primarily apply to users with assigned phone numbers with extensions. The formats can vary, as mentioned below:

• Where the last several digits of the base number are also added as the extension. E.g., +14025557334;ext=334
• Where both the base number and extension are unique for each user. E.g., +14025557253;ext=3111 and +14025556567;ext=3112
• Where the base number is common, and the extension is unique for each user. E.g., +14025557000;ext=111 and +14025557000;ext=112

Timeline: This change began rolling out in mid-September 2023 and is expected to be complete by late October 2023.

Impact On Your Organization

The Previous Mechanism

Under the previous mechanism, Microsoft Teams performed a somewhat flexible match:

• If a call was made to +14025557334;ext=334, Teams would find the user configured with the phone number +14025557334;ext=334.
• If a call was made to the base number +14025557334 without any user configured with that exact number, Teams would still match it with the user having the extension, e.g., +14025557334;ext=334.

The New Mechanism

The updated mechanism focuses on exact string matching. So, if a call is made to +14025557334, Teams will not match it to a user unless the full phone number, including the extension, is configured for a user.

Preparing for the Change

Tenant Dial Plans

Ensure that your tenant dial plans include normalization rules that translate abbreviated dial strings to the full phone number configured on users. For example, a pattern like ^(\d{3})$ and Translation +14025557$1;ext=$1 would serve this purpose.

Session Border Controllers

Verify that any phone number manipulation or translation rules used on your Direct Routing Session Border Controller are capable of translating to the full phone number configured on your users.

The aim of these changes is to make phone number matching more accurate, thereby improving the overall user experience. Although these updates might require some adjustments, especially if your organization uses extensions, they are designed to ensure that your communications are as precise and effective as possible.

Further Reading

Create and manage dial plans (https://learn.microsoft.com/en-us/microsoftteams/create-and-manage-dial-plans)

Translate phone numbers to an alternate format (https://learn.microsoft.com/en-us/microsoftteams/direct-routing-translate-numbers)

By understanding and proactively responding to these updates, you can ensure a smoother transition and better user experience for your Microsoft Teams environment.

End.