Complex Number Management in Multi-Vendor UC Solutions
January 5, 2023
Guest Blog Post from Kevin Kieller, EnableUC
Number management refers to ordering, tracking, provisioning, decommissioning, and managing the inventory of DIDs (direct inward dial numbers), which some carriers call TNs (telephone numbers), and extensions.
Any unified communications or collaboration system that provides inbound or outbound calling needs to manage numbers to connect to the PSTN (public switched telephone network). Extensions are assigned internally, effectively representing private numbers, typically 3, 4, or 5 digits in length. The use of private extensions led to legacy on-prem phone systems being referred to as PBXs (private branch exchanges).
Number management is not “sexy”, it does not involve artificial intelligence, blockchain, or 5G; however, effective number management is critical to providing a quality user experience.
Number Management Can Be Easy
For small organizations with limited turnover, keeping track of which DID or extension is assigned to whom, can be done using a simple spreadsheet.
Moderate Number Management
As both the number of users and user turnover increases, so too does the demand on tracking numbers accurately. Besides the volume of changes, additional administrators are assigned to cope with the load and the numbers themselves are often configured across more than on PBX systems.
At some point, tracking DIDs or extensions using a spreadsheet becomes unwieldy or impractical. The more numbers you are trying to track, the greater the chance of error.
Aging Numbers
When an employee exits an organization, it is customary to “age” the DID or extension before assigning it to another new employee. The idea is to avoid callers making calls to a specific person who is no longer at that number.
At the macro level, numbers are reassigned frequently. For example, nearly 100,000 mobile phone numbers are reassigned every day.
Telecom providers typically reassign numbers within 90 days from when they become deactivated, but there is no specific time limit or rule. In area codes with high demand for recycled numbers, the reassignment will occur quicker.
Telecom administrators within organizations, typically choose to “age” a number for 60 to 90 days before re-assigning.
Reserving Numbers
Larger organizations may reserve blocks of numbers ahead of a project or onboarding a group of new employees.
Carriers in turn request blocks of numbers from NANPA (The North American Numbering Plan Administrator) or CNA (Canadian Numbering Administrator) within North America. These numbering plan administrators release numbers in blocks of 10,000, although they may be split across multiple telecom providers in 1,000-number groupings.
How Reserving Blocks of Numbers Helps
If you know you are going to onboard 100 interns for the Fall semester, you might reserve a block of 100 numbers from your carrier in August. This way the DIDs are assigned to your SIP trunk ahead of time; no need to scramble, or port numbers. A better day-one user experience.
By requesting a block of numbers, if they are in a contiguous range, it makes it easier to direct all the temporarily unassigned numbers to a main switchboard operator or to a standard message.
For example, in Microsoft Teams you can use PowerShell to play an audio file if someone calls any number within a range of numbers.
The contiguous range helps again at the end of the semester when you can more easily “unassign” and direct the entire block of numbers again to an audio file. You might choose to alternate between blocks of numbers to support different groups of interns between semesters.
Further, a contiguous block of numbers may be more aesthetically pleasing and/or easier to remember for customers or individuals within the organization that interact with multiple people from the same group. Albeit, the increasing use of “click to call” most often mitigates the vanity value associated with numbers ranges, excepting a primary contact number that initiates a range, ending in multiple repeated digits (often zeroes).
Dealing with Complex Number Management
As organization size grows so too does the complexity of number management.
However, the most complex number challenge falls to service providers, who enable telecom services for multiple customers, often across multiple UCaaS solutions.
While multiple number management tools can meet the needs of large organizations, few tools can support the demanding, and customized needs, of service providers.
I recently became acquainted with a tool that deals with even the most complex number management situations: VOSS Automate.
VOSS Automate provides much more than number management; however, for the purpose of this article, I will focus specifically on the number management capabilities: Number Inventory, Number Range Management, Cooling & Reservation, Auditing Number Inventory.
More Steak than Sizzle
VOSS Automate is designed to be a powerhouse; it does not have the most elegant user interface or the fanciest number inventory graphs.
What VOSS Automate does have, and this is critical for service providers, is the ability for several administrators to manage an entire estate of numbers, across multiple customers and customer sites, using a hierarchy.
For any of the number management functions, you can select the scope from the defined hierarchy.

The hierarchy control allows you to apply any search or operation to your entire number inventory, a specific customer, or a specific customer location. This significantly improves process efficiency for service providers.

Number Inventory
With VOSS Automate the number inventory can exist at different hierarchical levels aligned to users, services, and the devices’ assigned numbers, which are typically at a site level. The number inventory allows you to view and manage numbers at the specified hierarchy level. You can track numbers to see how they’re used in the system.
If you choose to automate user or device provisioning, or allow customers access to a self-service portal, only contextually valid numbers will be available for each operation.
Number Cooling and Reservation
“Number cooling” is the terminology VOSS uses to describe the automatic aging of numbers after service delete to prevent immediate reuse of a number. This feature can be enabled at any level of the hierarchy, allowing a service provider to manage this at a customer or site level.
During the cooling period, the number can’t be reused until either the cooling period has elapsed, or until a service provider administrator has manually removed the number from the cooling group. Once a number is removed from the cooling group, it is reintroduced into the pool of available numbers for allocation to a user, phone, device, etc.

Number Range Management
Allows blocks of numbers to be reserved, unreserved, added or removed from a cooling group.
Number Inventory Audit
This feature allows a service provider to audit the number inventory and make sure that the status and usage of each number aligns to the devices or services configured with the matching numbers. The audit function creates new numbers for devices or services that don’t already exist, and updates existing number entries to ensure the Status and Usage fields reflect the correct information.
Most often the audit function is run at a customer level.
Number Management Recommendations
- If you are an organization with under 200 users and annual turnover less than 20% (i.e., onboarding 40 users and offboarding 40 users per year), start by using a spreadsheet template.
- If you are a medium or large organization, consider investing in a basic number management solution. (You can try to save a few dollars by just using a spreadsheet although the investment of labor to manage 1000+ users often exceeds the cost of an effective number management solution.)
- If you are a large organization in a business with a high percentage of change year-over-year (e.g. an educational institution), or you have specialized requirements, investigate more advanced number management systems, and more extensive automation platforms such as VOSS Automate.
- If you are a service provider, investigate VOSS Automate to make number management, and potentially your entire managed service process, more efficient.
To learn more about number management and other benefits of UC automation management, you are invited to register for a webinar I will be participating in, on January 31, 2023, on “The Real World is Messy: How to Embrace Microsoft Teams Phone in a Multi-Vendor UC Estate”.