Enterprises replacing their on-premise telephone system(s) with cloud solutions are faced with some fundamental differences in the two platforms and how they operate. These differences often require rethinking how certain services, delivered today on the on-premise system, will need to be delivered (or supported) tomorrow on the cloud solution. Early on in the planning/migration process, we have discussions with our clients to address some of the key areas of differences in order to raise awareness and reach consensus on how best to accommodate the changes that will come with a migration to Unified Communications as a Service ( UCaaS). In this article we are going to look at the subject of direct inward dialing (DID) numbers and dial plans.
In many cases, enterprises have historically owned (large) sequential blocks of numbers and assigned individual numbers to current or future users. These blocks are necessary to maintain an orderly internal dial plan. In most cases there are many unused numbers that serve as “spares.” Often, “spare” DIDs vastly outnumber the “used” DID numbers by hundreds or even thousands scattered across the DID blocks. Sequential blocks are often an important part of a dial plan, which is itself an important component in the design and set-up of on-premises telephone systems. In most dial plans, stripping off DID digits to be left with the last 3, 4, or 5 digits gave the users their internal extension number as well as a consistent leading digit. Steering codes (e.g., 1, 2, 3 digits) could be designed to identify a site’s location and appended to the user’s extension number, thus allowing for a coordinated internal dialing plan.
Enter today’s world of UCaaS: domestic (external) calling is fundamentally based on 10-digit dialing whereas Internal calling is heavily accomplished using a soft client where one enters a name – or chooses from a contact list - or clicks on a user’s name or icon. Similar to the use of mobile devices where much of the dialing is done by selecting from a contact list, the actual number being dialed sits behind the user’s name (or icon) that is selected. This method of internal calling essentially make the actual (extension) number to be dialed irrelevant to the user.
That's only the first way UCaaS calling is different from the planning and execution of an on-premises dial plan. When many organizations plan to migrate to the cloud, they presume they will move all their DID numbers to their UCaaS provider – assigning active licenses to their “users” and paying a negligible or nominal fee to keep their “spare” numbers on hand.
However, it's important to be aware that retaining spare numbers at a nominal cost is typically not the case with UCaaS. Providers often charge from $1.00 to $6.00 per month per spare number, in addition to possible one-time charges to port the number to their platform. Additionally, many providers have severe limitations on the quantity of spare numbers that can even be brought over and held in reserve.
So how do UCaaS providers address adding new users? Typically, they will assign new users with a 10-digit number pulled from the provider’s pool of available numbers based on what the customer desires (generally based on the location/area code of the user’s location). This typically results in assigning new users an exchange that is different than the DID sequence the organization had previously been using – and in some cases may even be a different area code. If this causes concern, we typically recommend our clients carefully estimate the number of spare numbers they think they will need in the near term (approximately one year) and select a limited quantity from their blocks to move to the provider - and pay for - as “spares.” After those numbers are exhausted, it is understood that the enterprise will be adding subsequent numbers from their UCaaS provider’s pool of numbers, and those subsequent numbers will likely be totally different from their previous DID sequences.
To summarize: an on-premise dial plan relied on sequential blocks of numbers to help identify steering codes for identifying site locations and coordinating internal department telephone assignments, and there were often leftover numbers in the block for future growth. By contrast, a UCaaS-based plan doesn't have a structured number scheme behind it and it can be costly to forecast how many numbers might be needed for future growth.
that will affect their spend, design, and user acceptance. Carrying over large amounts of spare DID’s is generally to be avoided when moving to UCaaS. Understanding how and why the change to UCaaS affects internal communications helps clarify why maintaining large sequential DID blocks is generally not advisable. Understanding this allows IT/Telecom to prepare management and staff for the upcoming changes resulting from a move to UCaaS - and will prepare them for what will be abandoned as part of the move away from the legacy premise-based telephony.