High Availability Direct Routing – the Key to Adding Telephony to Microsoft Teams

16 Mar 2021

With more than 650,000 US businesses using Office 365, and over 115 million daily Teams users, Microsoft is well-positioned to maintain its long-standing desktop dominance. While no challenger poses an existential threat here, Microsoft is vulnerable in the broader collaboration space, where these two offerings do not represent a complete solution. As standalone solutions, Office 365 and Teams are market leaders, but for collaboration, telephony is the third leg, and this is where Microsoft can be vulnerable.

Telephony has never been native to Microsoft’s portfolio, but it has always been foundational to Unified Communications platforms, and that’s the cohort Teams is largely competing against. All of the strong UC players have native telephony integration, and there are two basic camps here. First would be the PBX vendors, for whom UC was the successor offering, and second would be the cloud players who started out with hosted VoIP, and now provide full-fledged UCaaS.

Telephony remains central to both types of players, all of whom are growing their UC business at a pace comparable to Teams. Microsoft can maintain a strong market position with Teams, but given the competitive landscape, a tighter integration with telephony is needed. Telephony still has value as a standalone application, but when integrated with Teams, the platform becomes a more complete collaboration solution.

Two Paths to Telephony with Teams – Calling Plans and Direct Routing

Microsoft Calling Plans are serviceable, but cannot match the telephony capabilities of Microsoft’s UC competitors – especially in terms of limited geographic coverage – creating risk both for end customers and Microsoft. Direct Routing has emerged as a better telephony option, not just in terms of features and value, but also for providing high availability and network resilience from the cloud.

Many verticals require this, not just for everyday communications, but for business continuity and responsiveness to customers or patients, whether it be for healthcare, financial services, government agencies, travel services, etc. Aside from providing global coverage, Direct Routing is appealing because it allows end customers to keep their existing carrier contracts, otherwise known as BYOC – Bring Your Own Connectivity.

For all of these scenarios, the business decision to go with Teams will very much be tied to their confidence in Microsoft’s ability to support telephony. Businesses have long been accustomed to having on-premise call control, and don’t want to risk that with cloud-based telephony – no matter how good the other applications in Teams are. Add to that the need to support distributed workforces, especially during the pandemic, and it should be clear why it’s so important to have enterprise-grade telephony from the cloud.

Direct Routing requires a session border controller (SBC), but that alone does not ensure high availability telephony with Teams. Nor does having a reliable ISP for network connectivity, or even multiple providers for redundancy. While this form of connectivity will keep your data networks running, it does not determine connectivity uptime for cloud telephony. Much like the early days of VoIP, when media gateways provided PSTN failover support for network outages, a similar capability is now needed for connecting cloud telephony to the PSTN.

Cloud platforms like Azure, Google and Amazon are subject to occasional outages, and without the right architecture, Direct Routing for Teams will lose call control when that happens. Not only is this a worst-case scenario, but it would confirm the worst fears of any enterprise apprehensive about using Teams with call control being solely in the cloud.

Direct Routing Needs Both an SBC and an SBA

The right architecture to mitigate this would complement the SBC with an SBA – survivable branch appliance. Being embedded in the SBC, the SBA would provide on-premise call control to enable PSTN connectivity in the event of a cloud outage or lost cloud connection where Teams is being deployed. With that architecture, enterprises get high availability telephony with Teams, along with network resilience to support PSTN access.

Whether considering Internet connectivity for your data network, or cloud connectivity for Teams, neither will have 100% uptime, and when it comes to telephony, neither can match the reliability of the PSTN. For enterprises that don’t want to compromise that when going to Teams, they’re going to need an architecture that includes SBAs.

However, this isn’t a simple checkbox item where the SBA is plug-and-play with the SBC. They must be fully interoperable for critical telephony elements such as E911 for emergency services (albeit without dynamic tracking when in survivable mode), and Local Media Optimization to keep voice traffic localized to the Teams client - rather than traversing the Internet where the media becomes more vulnerable to quality impairments and security threats.

Choosing a Direct Routing Partner

One of the inherent challenges for using Direct Routing with Teams is the complexity in setting it up and managing it. Calling Plans may be simpler – and thus more appealing to IT – but they fall far short of what Direct Routing can provide, presuming they’re properly deployed. This is where the choice of a Direct Routing partner is important for Teams compatibility, as well as ensuring the right architecture for high availability telephony and seamless deployment.

Few vendors can match AudioCodes on this front, having partnered with Microsoft for SBCs going back to OCS 2007. They have been updated with every Microsoft iteration ever since, right up to the present with Skype for Business and Teams. The AudioCodes SBA is embedded within the line of Mediant gateways/SBCs – both 800 and 1000 series – all Microsoft certified, providing an integrated architecture purpose-built to support high availability telephony.



AudioCodes may not be the only SBC option for supporting Direct Routing with Teams, but with its long history and Microsoft certifications, this would be a very on-target choice for both enterprises and channel partners to consider. The key here for decision-makers is to go with the solution that best addresses the problem set. If the objective is to provide high availability telephony for Teams, then you need to consider AudioCodes, as their architecture based on embedding an SBA within their SBC is designed for that precise purpose.



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