Viv SharmaStart with the calls the business must handle and the support model it can sustain. My default evaluation would shortlist Operator Connect for standard cloud calling and assess Direct Routing where specific integration or routing requirements justify it. That is a design starting point, not a universal winner.
The decision table
| Decision area | Operator Connect | Direct Routing | What to validate |
|---|---|---|---|
| PSTN connection | Participating certified operator integrates with Teams. | A certified SBC connects the selected carrier to Teams. | Country coverage and supported service. |
| Infrastructure ownership | Operator manages the PSTN infrastructure. | Customer, integrator or managed provider operates the SBC solution. | Named owner for patching, certificates and incidents. |
| Typical fit | Standard calling with simpler administration. | Advanced routing, PBX or analogue integration. | Demonstrate the actual call flows. |
| Commercial assessment | Operator service, calling usage, porting and support. | Carrier service plus SBC, hosting and management costs. | Compare a like-for-like three-year cost. |
| Resilience assessment | Review operator commitments and recovery process. | Review SBC, trunk and network design with the delivery provider. | Test failures; do not infer resilience from the product name. |
| Change governance | Coordinate provider changes and Teams configuration. | Coordinate carrier, SBC, routing and Teams changes. | Document escalation and rollback ownership. |
The connection and ownership distinctions follow Microsoft’s PSTN guidance. The validation column and cost considerations are my recommended evaluation criteria. Direct Routing does not require an on-premises SBC: a managed service can operate it. [1]
Where Operator Connect fits
Operator Connect avoids running your own SBC infrastructure and lets administrators manage users and numbers through Teams. Check Teams Phone licensing, TeamsOnly mode and provider availability in every required region. The operator owns number provisioning, porting and PSTN support; Microsoft retains responsibility for its Teams services. [2]
I would ask the operator to demonstrate number delivery, porting coordination, incident escalation and management of emergency addresses. Ask who owns a failed inbound call when the Teams service appears healthy, and how the provider supplies evidence for a joint investigation.
Where Direct Routing fits
Direct Routing is appropriate when retaining a carrier, integrating third-party telephony or implementing advanced routing matters. It requires a supported SBC and the relevant Teams and Teams Phone licensing. The architecture must account for the SBC’s DNS name, trusted certificates and supported connectivity. [3]
Make the additional control valuable. Require a concrete business dependency before adding another routing layer. Include certificate renewal, software maintenance, monitoring, configuration backup and after-hours escalation in the service definition, even when a provider operates the platform.
A combined design can be valid
Both options can coexist in the same tenant. A common pattern is Operator Connect for PSTN calling with Direct Routing for specific PBX or specialist destinations. Keep routing policies narrowly scoped and review number patterns. Broad global voice-routing policies can unintentionally send other users’ calls to Direct Routing. [3] [5]
Plan the migration as a service change
- Discover: inventory numbers, users, queues, auto attendants, opening hours, reception workflows, recording dependencies and legacy devices.
- Design: choose the PSTN model per requirement; document licences, ownership, emergency calling and support boundaries.
- Pilot: test inbound and outbound calls, transfers, caller ID, DTMF, voicemail and after-hours handling.
- Cut over: agree the porting window, communications and recovery options with both providers. A number port is not an instant rollback switch.
- Stabilise: compare call quality, failed calls and support demand with the baseline before retiring old services.
Operator Connect onboarding includes enabling the operator and assigning numbers after the operator supplies them. Emergency-address administration depends on the operator. Coordinate any emergency-call validation through its approved process. [4]
My architecture recommendation
Use a scored decision covering coverage, legacy dependencies, operational ownership, resilience, cost and exit arrangements. Separate Teams application features from PSTN connectivity: neither option alone resolves a badly designed queue, an unsupported peripheral or missing service ownership. Select the simplest design that meets the documented business requirements and can be supported through an incident.
Microsoft references
- Microsoft Teams PSTN connectivity options
- Plan for Operator Connect
- Plan Direct Routing
- Configure Operator Connect
- Direct Routing voice routing configuration
Sources checked 1 October 2026. September coverage ends 30 September 2026. Product availability, preview status and requirements can change; validate the current guidance and tenant before rollout.