Voice plays a different role than other collaboration services in enterprise environments. Failures are immediate, highly visible, and difficult to work around.
As Microsoft Teams continues to replace legacy phone systems, the quality of an organization’s voice experience increasingly depends on its Microsoft Teams Direct Routing Partners. Reliability, coverage, and compliance are shaped by that choice.
This guide outlines a practical checklist for evaluating Direct Routing partners, grounded in how Teams voice operates at scale. The focus is on deployment realities, operational risk, and long-term sustainability.
Direct Routing is one of the ways enterprises can connect Microsoft Teams to the public phone network without making Microsoft the carrier.
In practical terms, MS Teams Direct Routing turns Teams into the calling interface while a third-party provider handles PSTN connectivity. Calls flow from Teams to a certified Session Border Controller (SBC), then out to local and international networks. Inbound calls follow the same path in reverse.
It sits alongside two other Microsoft options:
Microsoft Calling Plans
Microsoft acts as the carrier and provides numbers directly. Simple, but limited in geographic reach.
Operator Connect
Approved carriers integrate directly into the Teams Admin Center for simplified provisioning.
Direct Routing offers the most flexibility because enterprises retain control over carriers, routing, and architecture. That flexibility is also why poor design choices surface quickly and publicly.
View our Complete Guide to Direct Routing here >>
Choosing a Direct Routing partner is ultimately a risk decision, not a feature comparison.
Voice failures escalate faster than almost any other IT issue:
A misrouted emergency call becomes a compliance incident
A delayed number port stalls a regional office launch
A PSTN outage during earnings calls triggers executive escalation
Global enterprises feel this pressure first. Microsoft’s native calling coverage spans a limited set of countries. Most organizations operate well beyond that footprint, including markets with strict regulatory controls.
This is where Microsoft Teams Direct Routing partners diverge. Some operate carrier-grade infrastructure with local licenses. Others rely on multi-layer resellers. On paper, both look global. In production, only one behaves that way.
The sections below outline the core criteria enterprises use to assess Direct Routing partners across deployment, operations, and long-term viability.
Microsoft certification is a signal of how closely a provider is aligned with Teams voice at both a technical and operational level.
For enterprise telephony, this goes well beyond basic interoperability. Microsoft partner credentials reflect sustained investment in Teams voice, validated solution design, and a proven track record delivering calling services at scale.
One of the most meaningful credentials to look for is Microsoft’s Advanced Specialization in Calling for Microsoft Teams. This designation confirms that a provider has demonstrated deep expertise in Teams Phone architecture, security, deployment, and ongoing operations. Pure IP holds this specialization, indicating that its Teams voice solutions have been assessed and validated directly by Microsoft.
Operator Connect certification is another important marker if you are taking a mix and match approach with Operator Connect and Direct Routing. Operator Connect providers integrate directly into Microsoft’s cloud through approved peering arrangements, rather than routing calls over the public internet. Direct cloud peering improves call quality, reduces latency, and simplifies administration by allowing numbers and services to be managed natively within the Teams Admin Center. It also strengthens escalation paths, since Microsoft has direct visibility into the operator’s environment.
When evaluating Microsoft integration, focus on whether the provider offers:
Operator Connect certification with direct cloud peering into Microsoft
Native management within the Teams Admin Center for users and numbers
Clear alignment with the Teams Phone roadmap, including new calling features and updates
Beyond formal certifications, experience matters. Teams voice is operationally complex, and providers with long-standing Microsoft relationships tend to navigate platform changes, service incidents, and feature rollouts more effectively. Look for evidence of certified Microsoft engineers within the provider’s team and a history of delivering Teams voice services across multiple enterprise environments.
SBC architecture has a direct impact on call quality, resilience, and operational overhead.
Session Border Controllers sit at the heart of Direct Routing, controlling how calls are secured, routed, and connected between Teams and the PSTN. How they are deployed and managed matters long before users notice problems.
There are two primary architectural models:
Customer-managed SBCs, hosted on-premises or in customer-controlled cloud infrastructure
Provider-managed SBC-as-a-Service, operated and maintained by the voice provider
Customer-managed SBCs offer maximum control but require in-house expertise for patching, certificate management, redundancy design, and security hardening. This model can work well for organizations with existing voice engineering teams, but it adds operational burden over time.
Provider-managed models shift that responsibility to specialists. Providers such as Pure IP operate cloud-native, geo-redundant SBC platforms built specifically for Teams voice, removing the need for customers to deploy or maintain SBC infrastructure themselves.
When assessing SBC architecture, key questions include:
Where are SBCs physically hosted, and how close are they to users?
Is media kept local to reduce latency and improve call quality?
How is redundancy handled across regions and data centers?
What happens to active calls if a region or cloud zone fails?
Most enterprises end up running hybrid models in practice. Operator Connect in core countries, Direct Routing elsewhere, and legacy PBXs integrated during transition periods. A capable provider should support this mixed reality without forcing architectural redesigns or introducing unnecessary complexity as the environment evolves.
Global coverage claims only matter when they hold up country by country. Enterprises should ask for a detailed, country-level view of full PSTN replacement, not a headline number. “Supported” can mean very different things depending on local regulation, licensing, and network ownership.
At a minimum, confirm that coverage includes the following in every required country.
Local number availability
Local numbers are often a regulatory requirement, not a convenience. In many countries, employees must present a local caller ID to place or receive calls, and customers are far less likely to answer international numbers. Lack of local numbering can block adoption, break customer-facing workflows, and, in some regions, prevent legal operation altogether.
Inbound and outbound calling
Some providers support outbound-only calling or limited inbound services through partner networks. This creates uneven user experiences and complicates call routing and reporting. Full PSTN replacement requires reliable inbound and outbound calling with predictable quality, routing, and failover behavior.
Number portability
The ability to retain existing numbers is critical during migrations. In many countries, number porting is slow, highly regulated, and dependent on local documentation. If porting is not supported, organizations may be forced to change published numbers, disrupt customer contact points, or delay go-live dates. Porting capability and experience directly affect migration risk.
Emergency services
Emergency calling is one of the most common failure points in global voice deployments. Support must include correct routing to local emergency services and, where required, transmission of accurate location information. This is not uniform across countries, and gaps here create serious safety and compliance risks.
Top-tier providers operate licensed infrastructure in dozens of countries and extend coverage further through tightly controlled partnerships. The distinction matters. Providers with owned or directly licensed networks typically have more predictable timelines, clearer accountability, and fewer handoffs when issues arise.
Operational maturity shows up when something breaks, not when contracts are signed.
SLAs only matter if they reflect how voice services are run day to day. A 99.99 percent SLA still allows close to an hour of downtime per year. More importantly, many SLAs measure only network availability, not end-to-end call success. Calls can fail while the network is technically “up,” leaving users impacted with no breach on paper.
Mature providers design for failure. They monitor call quality, signaling, media paths, and regional performance continuously, not just core infrastructure. They detect degradation before users report it and act before it escalates.
When assessing operational maturity, look beyond headline SLA numbers and focus on:
A true global NOC with 24/7 coverage and voice-specific expertise
Proactive monitoring of call quality metrics, not just link status
Clear ownership for incidents that span Microsoft, carriers, and local networks
Defined escalation paths with guaranteed response and resolution targets
Pay close attention to how incidents are handled across vendors. In a Teams voice environment, issues often sit between Microsoft, the SBC layer, and the PSTN. Providers with mature operations take ownership of that complexity rather than pushing responsibility back to the customer.
Pilots are the best place to test this. Raise tickets during evaluation. Ask detailed questions. Track response times, clarity of communication, and follow-through. How a provider behaves before go-live is usually an accurate preview of how they will perform when the environment is under pressure.
Compliance is not a feature of Teams voice. It is a shared responsibility that can easily fall through the gaps.
Emergency calling is the most visible example. It must work everywhere the organization operates. E911 in the US. 112 across Europe. Local equivalents elsewhere. That requires accurate, continuously maintained location data and correct routing to local emergency authorities. In global environments, this is rarely uniform and frequently underestimated.
Beyond emergency services, voice compliance extends into security, data handling, and regulatory auditability. This is where provider credentials and controls matter.
Clear responsibility boundaries are essential:
Microsoft provides the collaboration platform and core cloud infrastructure
The voice provider is responsible for regulatory compliance, call routing, numbering, and PSTN obligations
For enterprises in regulated industries, security certifications are a key indicator of maturity. Providers like Pure IP emphasize formal standards such as ISO 27001 and SOC 2 because they demonstrate audited controls around information security, access management, incident response, and operational governance.
These certifications matter in practice:
ISO 27001 indicates a structured, audited information security management system covering people, processes, and technology
SOC 2 provides assurance around how customer data is handled, monitored, and protected over time, particularly relevant for cloud-delivered voice services
For many organizations, compliance also includes requirements for call recording, data residency, and lawful intercept. These capabilities vary significantly by country and must be supported in a way that aligns with local regulation, not just platform capability.
If you operate in finance, healthcare, or the public sector, do not assume that Microsoft coverage extends to voice compliance by default. Ask explicitly where Microsoft responsibility ends and where the provider’s begins. Ask how certifications are maintained, how audits are handled, and how compliance is enforced across all regions in scope.
In global voice, security gaps rarely announce themselves early. They surface during audits, incidents, or regulatory reviews, when remediation is slow and expensive.
Migration is where Teams voice strategies succeed or fail in practice.
Number porting introduces regulatory friction. Legacy PBXs often remain in place longer than expected. Timelines slip as dependencies surface. At the same time, user expectations move quickly once Teams calling is announced internally. These pressures tend to converge during migration, not design.
Providers with real migration experience plan for this complexity rather than treating onboarding as a provisioning exercise. Pure IP approaches Teams voice migrations as structured programs, built around controlled phases rather than single cutover events.
Effective migration support typically includes:
Pilot groups before broad rollout, allowing call quality, routing, and user experience to be validated in production conditions
Phased deployment by country or region, aligned to local porting rules and regulatory timelines
Parallel operation of legacy and Teams voice environments, reducing risk while critical numbers and workflows are transitioned
This approach matters most in global environments, where porting timelines, documentation requirements, and emergency calling rules vary significantly by country. Attempting a single global cutover often leads to stalled launches, fragmented user experiences, and prolonged coexistence under pressure.
Change management is part of the technical outcome. Users adapt quickly to new interfaces. They are far less tolerant of missed calls, unreachable numbers, or inconsistent behavior during transition. Migration support that accounts for this reality reduces disruption and builds confidence in Teams voice from day one.
Support quality determines how survivable incidents feel.
Look beyond “24/7 support” and ask how support actually operates:
Who owns escalation across vendors?
Are alerts proactive or reactive?
Do you get visibility through dashboards and reports?
Providers like Pure IP emphasize single-point accountability because finger-pointing wastes time during outages. Transparency matters as much as availability.
| Evaluation area | What to validate | Why it matters |
|
Microsoft Certification |
Certified SBCs, Operator Connect status | Affects escalation paths and interoperability |
| SBC Architecture | Geo-redundancy, media locality | Determines call quality and resilience |
| PSTN Coverage | Country-level detail, porting support | Prevents rollout delays and compliance gaps |
| SLAs & Operations | True service SLAs, NOC coverage | Indicates real-world reliability |
| Compliance | Emergency calling, ISO standards | Reduces regulatory and legal risk |
| Migration Support | Porting, hybrid models | Minimizes disruption during transition |
| Support Model | 24/7 ownership, dashboards | Shortens incident resolution time |
The checklist above reflects the areas that consistently shape long-term outcomes. Microsoft alignment through certifications and Operator Connect. Architecture designed for resilience. PSTN coverage that works country by country. Operational maturity that holds up during incidents. Compliance that stands up to audit. Migration support that reduces risk. Ongoing support with clear ownership.
Together, these factors determine whether Teams voice remains stable as usage grows and requirements change. For most organizations, Teams is no longer an overlay on legacy telephony. It has become the primary voice platform, with expectations around reliability, governance, and scale that match that role.
Many enterprises are also planning beyond initial deployment. Mobile integration, call quality analytics, and deeper visibility into performance are increasingly part of long-term roadmaps.
Providers that invest in these capabilities tend to adapt more smoothly as the Teams platform evolves.
If you are evaluating Direct Routing providers, Pure IP offers an approach grounded in Microsoft-validated credentials, global PSTN coverage, and operational experience delivering Teams voice at scale. From Direct Routing and Operator Connect design through migration and ongoing support, Pure IP helps organizations build voice environments that are stable today and ready to evolve.
Speak with Pure IP about your Teams voice strategy, or explore our Direct Routing and migration services to see how these principles apply in real deployments.