Rethinking Shared PSTN
What is compelling me to draft this note?
To share... the future? (I wish I was so clairvoyant)
How about to send up a flare... to draw attention to an unfolding vision from the field, as interpreted from the few large enterprise Telecom Leaders that I have the pleasure of working with.
... on the topic of: Evolving PSTN services
Preface:
As a self-proclaimed Old Phone Guy, I understand the full-circle journey of extension-dialing on Centrex (one of the original, enterprise, cloud PBX platforms), to where we are today... but I do not romanticize dialing '9' to get an outside line and I do not get nostalgic about supporting the CDR audits for departmental charge-backs related to metered calling (badge of honor to those who supported this). And so, I won't dare further to insult your intelligence with another old-phone-guy version of the glory days.
But, full-circle it is, so here we are: Cloud PBX users without a Direct Inward Dialable number, sharing a PSTN service (with other employees) to make external calls.
To be fair, contemporary PBX platforms today have always offered the ability for a user to dial an external number, without that user having their own, dedicated, DID number. It really is nothing new. But this discussion involves Microsoft, which has historically chartered every part of their licensing entitlements into a per-user model. In other words, in Microsoft's world, the concept of sharing entitlements (at least this particular entitlement) is new, and it's called "Teams Shared Calling"
Not interested in the context? Skip to bottom before leaving.
The grinding start:
Migrating enterprise communication services
The requirements involve not only moving users but also moving PSTN/external calling services to the new platform.
Consider that when lighting up a user's licensed entitlement to use Teams as a Phone System, there is still another requirement to enable that user with an entitlement to access external PSTN services, with a supported PSTN Connectivity option.
In other words, until recently, a Microsoft Calling Plan license or 3rd party PSTN service has been required to allow external calling - per user - and everybody who might need to make a phone call is essentially incurring a per-user operational expense.
Another way it's viewed: a per-DID operational expense.
And so, during the customer's due diligence assessment of their current telephony estate, pre-migration, the notion surfaces of auditing.
You hear these questions: "Do we need all these numbers? Are people using them? Are external callers calling our employees on these numbers? Can we reduce the number of DIDs
All warranted questions. Especially now that phone calls are not so common. It's hard to focus the project activities squarely on the platform migration when the migration opens an opportunity to clean up technical debt. The distraction = 'we can get rid of unused DIDs and unnecessary operational expenses!'
And so, number management is typically the gate opener to this topic of rethinking PSTN.
Now fast forward with Microsoft's development of Shared Calling (and some of Microsoft's other innovative PSTN options):
What appears to be unfolding is a realization (a vision) that involves a two-pronged approach to remove DID overhead while also adding enterprise, outbound-calling capabilities...
Roadmap options
What are the Microsoft tools, exactly, that enterprise telecom leaders are putting in their road maps?
On one hand:
For those employees who clearly need a DID number, these personas need to be empowered to make & receive calls at their convenience:
On the other hand:
For those employees who do not need a DID number... but still may have a requirement to make an outbound call:
What does the provisioning road map look like right now?
Teams Phone Mobile (for employees who need a DID) is a no-brainer... enterprise retains ownership of the number, ease of use for the user, benefits all around. In Europe, this seems to be all the hotness; EMEA enterprises are eating this up and it's becoming status quo.
But in the United States, it's too early to tell where this trend is going. While not true everywhere, U.S. enterprises generally have a hard time getting out of their own way with any clear policy (or desire) to equip their employees as 'mobile-first', so the inertia of Teams Phone Mobile remains in a state of perplexed pensiveness.
So Teams Phone Mobile aside (another article for another day), currently (at least from what I can see), the top-of-mind consideration right now for U.S. based enterprise Telecom Managers appears to be Teams Shared Calling.
Despite their interest in this solution, when turning to operators for a PSTN solution to their Shared Calling vision, Telecom Managers are learning that their preferred operators are not prepared to support it.*
(*fully acknowledging that Microsoft does have a handful of partner operators that are supporting Shared Calling, today. You are the few.)
It seems that the industry-norm for operators is to offer 'per DID' billing models. Having 10 or 10,000 users behind one Shared Calling number simply breaks this model.
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And for operators offering 'per concurrent call' billing models, when a customer moves their heavy-external-calling users to Teams Phone Mobile (from the landline operator to a mobile operator), the Erlang calculation to support the anticipatedly lower number of concurrent calls doesn't add up to the same amount of bandwidth requirements.
It's not just a marginal adjustment; enterprise Telecom managers are exploring significant reductions in their PSTN landline overhead.
The struggle is real...
There must be some very tense conversations happening in the strategy rooms of landline PSTN operators...
For PSTN operators with only per-DID billing models, it's simple: Customers will find something else. Operators relying exclusively on the per-DID model will need an alternative. And fast.
For PSTN operators with concurrent call billing models...
Will a concurrent call model still work with Shared calling when the expected usage is so low, but the potential dynamic load could be so high?
Think of an Erlang calculation where (say), of 10,000 users, only a handful are making external calls; so few calls that they are only generating 2 hours of call traffic per hour. Okay, no problem; the landline operator can scale their existing service down to the anticipated per-concurrent call rate. It's a significant reduction, but at least not a total loss. Now, is this bandwidth/concurrency reduction going to work if...
If there was some event (natural disaster / civic surprise / HR announcement / etc), and suddenly many of the 10,000 users are trying to call home, or call an Uber, or call for more dire help... what happens to that reduced concurrent-call commitment? Will it handle the burst?
Concurrent call models usually allow for bursts, but traditionally only marginal bursts (e.g., 10-20%). What happens when there is an event that generates a 1000% burst? Does it break the model?
If the demand peaks and the design doesn't support everyone's external call attempt, is the business okay with the liability of a solution that knowingly blocks an employee's ability to make their external call (esp. if it's an emergency call)?
On the other hand, to accommodate the potential burst-demand that an employee base may put on a concurrent call trunk, does it make sense to pay for that maximum burst capacity year-round, just as an insurance policy, when the day-to-day average usage is so low?
Microsoft is offering, with their own Pay-As-You-Go option, a path forward with no limit to the number of users behind a single Shared Calling number, and no indication of any burst limit. And, in a shift from an all-you-can-call billing model to an old-school method, they are accounting for PSTN costs through metered usage (Product = Communication Credits).
Is Shared Calling with Communication Credits a harbinger of a trend back to metered usage?
Questions being asked...
Telecom Leaders are interested in Shared Calling. Given the ubiquitous presence of Teams found in most enterprises and the ability to have a Teams-to-Teams call without PSTN services, telecom teams are not finding evidence of usage that warrants each user have their own DID number.
And with the enterprise IT trend over the last three decades ("no more need for detailed Telecom Expense Management (charge-backs) because PSTN is now just another IT service rolled into the larger cost of doing IT business"), it means that Telecom Leaders today are not overly concerned with auditing metered usage
They are academically interested in Microsoft's Shared Calling (with Communications Credits) model and the cost benefits that it brings to their budget. But while academically interested, there is either still a relationship-affinity to their preferred Tel-Co partner, or a preference (or some need) to deploy with a 3rd party Tel-Co partner.
Unfortunately, as mentioned earlier, Telecom Leaders are learning that their preferred Tel-Co partners are not supporting Shared Calling.
So the questions arise...
How will operators adapt to accommodate the cost benefits of Shared calling?
Will operators drastically increase (or offer limitless) dynamic burst tolerances?
Will there be a movement to meter Shared Calling minutes?
What are the pivots planned, to build/market/deliver/support a Shared Calling model?
What would that billing model look like?
Who all is getting out in front and leading with a Shared Calling PSTN solution?
Next steps
Granted, even with all of this context, there are plenty of details not called out that need considering, but the takeaway is this:
Enterprise Telecom Leaders are synchronously expressing noticeable interest (and even committed intent) to move away from per-DID, landline billing models, to models where shared PSTN is supported.
So... the flare is up. Notes from the field for the taking.
If:
...you are a PSTN operator, the industry wants to hear about where you lead with Direct Routing and Operator Connect solutions for Teams Shared Calling scenarios.
...you are project team setting out on a migration to Teams Phone, then consider that Shared Calling is more than a mere feature; it is a catalyst to reshape your PSTN strategy and timing-wise it should be one of the first topics of discussion in your project.
...you have already migrated to Teams Phone, then consider a Shared Calling research & roadmap project
...you have nothing to do with your company's IT/Telecom domain, please consider sending this link to your favorite Telecom person, with the code phrase "saw this and was thinking of you. :)"
Join Microsoft tomorrow, April 16th, to learn more:
Copilot Principal Technical Specialist @ Microsoft
10moScott, great article! You are a Telephony legend. Well done!