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Business communication has evolved dramatically over the past two decades. Traditional desk phones and isolated PBX systems have steadily given way to cloud-based collaboration platforms that support voice, video, messaging and meetings in a single environment. Today’s workforce is no longer confined to a physical office. Such as remote work, hybrid teams and global operations demand flexible, always-available communication tools.
This shift has made Unified Communications (UC) a strategic priority for modern organisations. UC enables employees to collaborate seamlessly across devices, locations and communication channels while improving productivity and operational efficiency. At the centre of this transformation is Microsoft Teams, which has become a leading collaboration platform for businesses worldwide. However, to fully replace legacy phone systems and enable enterprise-grade external calling, Teams must integrate with the public telephone network. This is where SIP trunking and Microsoft Teams Direct Routing play a critical role.
In this blog, we explore what SIP trunking is, how Microsoft Teams Direct Routing works and why integrating SIP trunks with Teams goes far beyond voice. Thus, supporting a comprehensive unified communications strategy.
SIP (Session Initiation Protocol) is a signalling protocol used to establish, manage and terminate real-time communication sessions over IP networks. These sessions can include voice calls, video conferencing, messaging and multimedia communication. SIP trunking replaces traditional analogue or ISDN phone lines with an internet-based connection to the public switched telephone network (PSTN). Instead of physical phone lines organisations use SIP trunks to route calls over their existing data network.
With SIP trunking, businesses connect their phone system. Whether on-premises or cloud-based to a SIP service provider, enabling inbound and outbound calls using IP technology rather than legacy telecom infrastructure.
SIP trunking delivers several advantages that make it ideal for modern enterprises:
Businesses can add or remove call channels as needed without installing new physical lines.
SIP enables high-quality audio and simultaneous call handling.
Lower call rates, especially for long-distance and international calls, compared to traditional telephony.
Numbers can be provisioned in different regions without physical presence.
These benefits make SIP trunking a foundational component of cloud-based communications and UC environments.
Microsoft Teams has become a central hub for collaboration, but native PSTN calling requires either Microsoft Calling Plans or Direct Routing. For organisations seeking greater flexibility, control and cost optimisation, Direct Routing is often the preferred option.
Direct Routing allows businesses to connect Microsoft Teams directly to their chosen SIP trunk provider using certified Session Border Controllers (SBCs). This approach bypasses Microsoft Calling Plans while still enabling Teams users to make and receive external calls.
It is particularly suited for organisations with existing telephony contracts, regulatory requirements or complex call routing needs that demand customisation.
At the heart of Direct Routing is the SBC, which acts as a secure gateway between Microsoft’s cloud and the traditional telephone network. The SBC ensures compatibility, security and quality of service while managing call signalling and media flow. From a technical perspective, calls initiated from Teams are routed through the SBC to the SIP trunk and inbound PSTN calls follow the reverse path. This architecture enables seamless interoperability between cloud collaboration tools and carrier-grade telephony.
While Teams offers strong collaboration capabilities out of the box, integrating SIP trunks unlocks its full potential as an enterprise communication platform. This integration transforms Teams from a collaboration tool into a complete business phone system.
With SIP trunk integration, Teams becomes the single interface for all communication needs. Users no longer need separate desk phones or softphone applications, as calling is fully embedded into their daily collaboration workflows. This approach simplifies adoption while preserving existing telephony investments and business processes.
From a financial standpoint, SIP trunking offers granular control over voice spending. Rather than paying for calling plans for every user, organisations pay based on concurrent call usage, making it ideal for shared or hybrid workforces. Additionally, businesses retain autonomy over how calls are routed, monitored and reported, which is critical for compliance and operational visibility.
SIP is often perceived as a voice-only protocol, but its capabilities extend far beyond traditional calling. In a unified communications environment, SIP serves as a foundational technology that enables real-time interaction across multiple channels.
Unified Communications brings together various communication modes into a cohesive experience. Instead of fragmented tools for calls, meetings and messaging, UC allows users to communicate and collaborate within a single platform. This unified approach improves responsiveness, reduces delays and enhances overall workplace productivity.
SIP is designed to establish and manage real-time sessions of all types—not just voice. It supports multimedia signalling, presence updates and session control, making it a natural fit for UC platforms like Microsoft Teams. When SIP trunking is integrated with Teams, external voice communication becomes a native extension of Teams’ collaboration environment rather than a separate system.
A SIP-enabled Teams environment also enhances integration with third-party business applications. Voice interactions can be tied directly to workflows, customer records and analytics systems. This creates a data-driven communication ecosystem where voice becomes part of the broader digital business process.
Understanding the technical architecture behind SIP trunking and Teams Direct Routing is essential for designing a reliable and secure deployment. Each component plays a specific role in ensuring call quality, availability and compliance.
A standard Direct Routing setup includes tightly integrated cloud and network elements that work together to deliver seamless communication.
Deploying Direct Routing is not just about connectivity. Itt requires thoughtful planning to ensure long-term stability and scalability. Organisations must consider redundancy, security and interoperability from the outset. Best-practice deployments also account for future growth, multi-site expansion and coexistence with legacy systems.
The true value of SIP trunking with Teams Direct Routing is realised in day-to-day business operations. From employee productivity to organisational resilience, the benefits extend well beyond technical improvements.
Teams-enabled calling empowers employees to stay connected regardless of location or device. Whether working from home, the office or on the move, users have consistent access to all communication tools.
Centralising communications within Teams simplifies IT management and reduces overhead. With fewer systems to maintain, organisations can simplify operations and respond faster to changing business needs.
Business continuity is an importantl concern in today’s unpredictable environment. Teams’ cloud-based architecture, combined with resilient SIP trunking, ensures communication remains available during outages or disruptions.
Technology alone does not guarantee a successful deployment. The experience, technical expertise and ongoing support provided by your service partner play a critical role in ensuring a smooth Microsoft Teams Direct Routing implementation. From initial assessment to post-deployment optimisation, the right partner helps organisations avoid common pitfalls such as misconfigured SBCs, poor call quality or licensing mismatches.
A Microsoft-certified partner brings validated expertise, access to Microsoft best practices and proven deployment frameworks for Teams Direct Routing. Partners like Wavetel understand both Microsoft’s cloud ecosystem and carrier-grade voice requirements, ensuring reliable interoperability, regulatory compliance and optimal performance across enterprise environments.
End-to-end support covers every stage of the journey from assessing existing telephony infrastructure and planning number porting, to advising on the correct Microsoft 365 and Teams Phone licences. Ongoing services include SBC configuration, monitoring, troubleshooting, optimisation and proactive support to keep communications running smoothly as business needs evolve.
A successful Microsoft Teams Direct Routing deployment depends on careful preparation across licensing, connectivity, security and testing. Taking a structured implementation approach helps reduce technical risk, avoids service disruption and ensures that the solution performs reliably from day one. Proper planning also allows organisations to align voice services with business continuity, compliance and future scalability requirements.
This checklist outlines the key areas that should be reviewed and validated before going live. Each step plays an important role in ensuring seamless call handling, consistent user experience and long-term operational stability.
Organisations must confirm that the appropriate Microsoft 365 and Teams Phone licences are assigned to users who require PSTN calling. This includes validating compatibility between existing subscriptions and Teams Phone System features to avoid gaps in functionality.
SIP trunks must be provisioned with the correct number capacity, concurrent call channels and geographic coverage. Number porting, inbound routing, outbound call policies and failover paths should be defined in advance to ensure uninterrupted service.
The Session Border Controller must be configured and certified for Microsoft Teams interoperability. This includes setting up secure SIP signalling, media handling, codec support and routing rules to ensure reliable communication between Teams and the PSTN.
A comprehensive security review should be conducted to validate encryption, firewall rules and access controls. End-to-end test call flows both inbound and outbound must be performed to confirm call quality, emergency calling functionality and failover behaviour.
Integrating SIP trunking with Microsoft Teams Direct Routing is more than a telephony upgrade. It is a strategic step toward a modern unified communications environment. By combining flexible SIP connectivity with Teams’ powerful collaboration features, organisations can centralise communication, reduce costs and support a mobile, digital workforce.
SIP’s ability to extend beyond voice makes it a critical enabler of UC, helping businesses unify calling, meetings, messaging and collaboration within a single platform. If you are planning to modernise your business communications, Wavetel can help you design, deploy and manage a secure Microsoft Teams Direct Routing solution with enterprise-grade SIP trunking.
Contact Wavetel’s experts today to explore your options, receive implementation guidance or request a free assessment to build a scalable unified communications strategy.
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