Summary: This checklist explains the core technical design elements of Teams Direct Routing and why each one has long-term operational impact. At scale, these decisions stop being architectural preferences and become daily realities that affect call quality, incident response, compliance, and cost.
The shift to cloud collaboration reduced friction in meetings and messaging, but enterprise voice did not simplify in the same way. Voice systems stayed complex because call delivery still has to work under failure conditions and within regulatory constraints.
Teams Direct Routing sits at the center of that complexity. It moves responsibility for carrier selection, call routing, SBC placement, and security decisions out of Microsoft’s managed service and into the enterprise environment. Those choices directly affect how Teams voice behaves when usage increases, how issues are resolved, and how difficult change becomes later.
This checklist is designed to make those decisions visible. It helps IT and voice teams evaluate the technical and operational choices behind their Teams Direct Routing deployment, identify where risk is already embedded, and understand which design elements will matter most as scale, regulation, and complexity increase.
1. Architecture placement in Teams Direct Routing
Centralized vs distributed designs
✅ Checklist item: Confirm where SBCs and carrier interconnects are placed.
This is the foundation of any Teams Direct Routing design. SBC location determines media paths, latency, failure domains, and how outages propagate.
- Centralized Teams Direct Routing architecture
This anchors SBCs and carrier connections in one or two core locations. The model simplifies governance and accelerates initial deployment. For single-region or low-scale environments, it can be effective.
At enterprise scale, centralized designs introduce structural risk. Media must travel long distances for remote users, increasing latency and packet loss. When a core site or interconnect degrades, call quality issues affect all users, not just those near the failure. - Distributed Teams Direct Routing architecture
This approach places SBCs closer to users, typically at a regional or country level, which shortens media paths and improves call quality. When issues occur, failures are contained within a region instead of affecting the entire organization.
The trade-off is increased complexity. Distributed designs require additional SBC instances, more detailed routing logic, and consistent testing practices. For real-time voice traffic, those trade-offs are often justified because distance and failure isolation directly affect user experience and service stability.
What good looks like:
- Media paths align with user geography
- Failures are contained to regions
- Latency is predictable under load
Operational warning signs:
- Call quality complaints cluster in remote regions
- Packet loss or jitter appears during peak hours despite healthy WAN links
- Global incidents originate from a single SBC or carrier
- Manual rerouting is required during outages
If these signals appear, the Teams Direct Routing architecture is likely over-centralized.
2. SBC Ownership in Teams Direct Routing
Managed SBC vs Customer-owned SBC
✅ Checklist item: Confirm who owns SBC operations and accountability.
SBC ownership defines where responsibility sits during normal operations and during failure. This is often underestimated during Teams Direct Routing design.
- A customer-owned SBC model gives full control. Configuration, upgrades, certificates, integrations, and troubleshooting remain in-house. This suits organizations with deep voice expertise, regulatory constraints, or strict change control.
It also concentrates risk. SBC platforms require constant attention. Microsoft certification updates, carrier changes, and security patches do not align to business schedules. When incidents occur, recovery depends entirely on internal availability and expertise. - A managed SBC model shifts day-to-day operational responsibility to a provider. The enterprise retains architectural intent but reduces exposure to platform maintenance, certification drift, and cross-region incidents.
The difference becomes most visible during outages. Voice failures require immediate response. Managed models reduce recovery time by ensuring continuous ownership of SBC health and interoperability.
What good looks like:
- Clear ownership during incidents
- Predictable change management
- Certification and patching handled proactively
Metrics that expose risk:
- Increasing mean time to recovery for voice incidents
- Frequent after-hours escalations
- Emergency changes driven by certification or security gaps
- Reliance on a small number of specialists
3. Carrier strategy in Teams Direct Routing
Single-carrier vs Multi-carrier designs
✅ Checklist item: Confirm carrier dependency and failover capability.
Carrier strategy is where Teams Direct Routing design meets resilience. It determines whether outages are survivable or service-ending.
- A single-carrier design simplifies contracts, routing, and testing. It often looks sufficient during pilots and early production.
At scale, this model becomes fragile because carrier outages, interconnect degradation, and regulatory changes all require rapid response. When all calls depend on a single provider, even minor failures can escalate into widespread service disruption. - A multi-carrier Teams Direct Routing design builds redundancy into the platform. Calls can fail over automatically. Regions can use in-country carriers to meet regulatory and quality requirements. Enterprises gain leverage and optionality.
The cost is increased complexity, as routing logic must be precise, testing must be continuous, and operational discipline becomes mandatory to keep the environment stable.
Teams Direct Routing supports both models. It does not protect enterprises from the consequences of choosing simplicity over resilience.
What good looks like:
- Automatic failover between carriers
- Regional carrier alignment
- Minimal manual intervention during outages
Operational risk indicators:
- Emergency number porting during incidents
- Manual rerouting to restore service
- Regions failing regulatory or quality standards
- Limited leverage during renewals
If carrier failure equals service outage, resilience is insufficient.
4. Security and compliance in Teams Direct Routing
✅ Checklist item: Validate how security and compliance are enforced by design.
Voice introduces a distinct threat surface, and Teams Direct Routing design choices directly affect how exposed the environment is to fraud, toll abuse, and denial-of-service attacks.
SBC placement determines which systems are exposed to the public network, while media flow design controls where call data is processed and stored. Poorly designed environments depend on exceptions and workarounds, whereas well-designed Teams Direct Routing deployments enforce security controls through standard call flows.
Compliance requirements further increase complexity because call recording, monitoring, lawful intercept, and data sovereignty obligations vary by country and by industry. Teams Direct Routing either supports these requirements through its architecture or makes compliance difficult to enforce consistently.
Audits and real-world incidents tend to surface these design weaknesses quickly, often after the environment is already in production.
Be clear on Microsoft responsibility boundaries:
→ Microsoft does not manage carrier interconnects.
→ Microsoft does not troubleshoot SBC-level media failures.
→ Microsoft does not enforce regional compliance.
→ Microsoft does not design carrier failover.
Teams Direct Routing succeeds or fails in the space between Teams and the PSTN.
What good looks like:
- Compliance enforced without exceptions
- Media paths aligned to data residency rules
- SBC exposure minimized and protected
5. Change readiness in Teams Direct Routing
✅ Checklist item: Test whether the design can absorb change without re-architecture.
Most Teams Direct Routing environments are designed for stability. Enterprises rarely experience it as change is constant. Mergers introduce new carriers and numbering plans. Expansion pushes Teams into countries without native Microsoft calling options. Compliance requirements evolve. Microsoft certification models change.
Test your design against real scenarios
- Adding a second Teams tenant with overlapping numbers
- Deploying Teams Direct Routing in unsupported countries
- Replacing a carrier with limited notice
- Expanding call recording to new regions
Designs that tightly couple Teams, SBCs, and carriers accumulate technical debt. Designs that separate concerns absorb disruption.
Final pressure test for Teams Direct Routing
Use the questions below to assess operational risk in a Teams Direct Routing environment. Each question highlights a design decision that often looks acceptable during deployment but becomes critical during incidents or periods of change.
Can a single carrier outage impact all users?
If one carrier failure can disrupt service across regions, the design has a large impact range. Teams Direct Routing should limit the scope of carrier failures wherever possible. Outages should remain regional, not enterprise-wide.
Can routing logic change without SBC redeployment?
Routing changes are inevitable. If even minor adjustments require SBC rebuilds or service disruption, operational agility is limited. Well-designed Teams Direct Routing environments allow routing updates without re-architecting the platform.
Is recovery dependent on one team or region?
Voice incidents rarely respect business hours. If recovery depends on a single team or geographic location, response times will suffer. Teams Direct Routing designs should support distributed ownership and clear escalation paths.
Are compliance controls enforced by default?
Compliance should not rely on manual steps or exceptions. Call recording, data residency, and monitoring requirements should be enforced automatically through the Teams Direct Routing architecture. If controls are optional, risk increases over time.
Are changes tested outside live incidents?
Changes should be validated through routine testing, not during outages. Teams Direct Routing environments that lack regular testing tend to surface defects when pressure is highest.
If any of these questions cannot be answered clearly, the Teams Direct Routing design already carries operational risk.
Teams Direct Routing is often treated as a feature of Microsoft Teams. In practice, it becomes the operating model for enterprise voice once the platform is in production.
Decisions around architecture placement, SBC ownership, and carrier strategy shape how Teams voice performs under load, how resilient it is during outages, and how quickly service can be restored. These choices also determine how much ongoing effort is required to keep the environment secure, compliant, and adaptable to change.
Architecture diagrams show how a solution is intended to work. Day-to-day operations show how it actually behaves. Gaps between the two are where most long-term Teams Direct Routing issues emerge.
When Teams voice fails, the impact is rarely limited to technology. It affects users, support teams, and business operations.
If you want to assess whether your Teams Direct Routing design is built for scale, resilience, and change, speak with our Teams voice experts. We can help you evaluate your current architecture and identify the design approach that best fits your operational and regulatory requirements.
