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Understanding Ribbon Connect for Microsoft Teams Direct Routing

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Image: Yanawut Suntornkij -
Ribbon Communications last year released Ribbon Connect, a cloud-based service that facilitates a rapid, yet flexible hybrid telephony scenario in which telephony users can connect to both a PBX and Microsoft Teams Phone System.
This differs from call forking, which all Microsoft Teams-compatible session border controllers (SBC) support. Ribbon Connect provides a capability to easily transfer calls between PBX and Teams users as well as providing Teams telephony presence status to the PBX.
Before I dive into the technical details, let me explain two rationales for what Ribbon is doing here:
  1. Many organizations still owe money on a PBX equipment lease, or they may not have fully depreciated their purchase; consequently, they can’t eliminate the PBX or prefer not to. Or, perhaps an organization is anticipating a business event, like a planned move, that makes it challenging to invest resources to aggressively migrate to Teams.
  2. Integration with enterprise resource planning systems, customer relationship management systems, contact centers, or specialty equipment (emergency services, medical systems, paging, etc.) are critical to an organization's mission, employee health, or customer experience, so the PBX must remain in place. These critical services may not function appropriately if some users are on Teams and others on a legacy PBX because traditional integration options, like splitting incoming calls (aka SIP Forking) and call transfers aren’t seamless enough.
It becomes hard for organizations with these characteristics to use direct routing when some people are still tethered to the PBX, others want to move to Teams, and everyone needs voice calling interoperability in addition to emergency services. To understand what Ribbon has done with Ribbon Connect, let’s first review traditional direct routing scenarios, followed by how Ribbon Connect enables direct routing.
Traditional Direct Routing Scenarios
Microsoft Teams requires an SBC for connectivity to the PSTN. Most SBCs have tools to help customers integrate other communications systems with Teams (call routing tools, SIP Forking, analog ports, PRI ports, etc.). Most companies deploying direct routing will use one of the SBC scenarios illustrated below to connect Microsoft Teams Phone System to the PSTN (and potentially to their PBX).

In the left image’s scenario, an on-premises SBC is deployed, and the Direct Routing SIP trunks connect directly to the SBC. Calls are routed through the SBC, with some going to the PBX or contact center and others going to Teams users. This deployment can be termed a hybrid deployment because calls go to either a PBX, or Teams, or both (with call forking). This scenario is fully supported by Microsoft Teams Direct Routing. Note, however, that if a call goes to someone tethered to the PBX, there’s no easy way to transfer the call to someone connected to Teams —and vice versa. Furthermore, hunt groups programmed in the PBX or Teams are completely separate, making them difficult to use if some people in the hunt group are tethered to the PBX and others in the group have migrated to Teams.

In the right image, the SBC is hosted in a public cloud and shows a complete migration to the Microsoft Teams Phone System with Direct Routing. In this scenario, no PBX integration even exists. The SIP trunks connect to an SBC located in either the service provider’s network or a Public Cloud like Amazon Web Services or Azure. The SBC then interfaces with Microsoft Teams Phone System hosted in the Azure cloud. This scenario is also fully supported by Microsoft. But, since it’s a cloud-to-cloud deployment, deployment option offers no support for organizations that must keep a PBX in the mix for one reason or another.
The Ribbon Connect Architecture
As illustrated below, Ribbon Connect for Microsoft Teams Direct Routing is a different kind of service. The first thing you’ll notice is that the Direct Routing SIP trunks from the service provider are still connected to the organization’s PBX. A key concept for Ribbon Connect is that all PSTN calls still traverse the PBX.
The solution includes an SBC in Ribbon’s cloud, but it also has other integration services as part of the offer. It’s a pure cloud service, meaning there’s no hardware or software to purchase, and it’s priced using a per user per month operating expense model.

Ribbon Connect provides a configuration portal where organizations enter all of the configuration information, including the brand and software revision of the PBX, the PBX’s IP address, and the SIP credentials for every Microsoft Teams user who needs PSTN connectivity. Ribbon Connect then registers each Teams user as a SIP softphone user on the PBX and does media and signaling translation between the PBX and Teams.

When a particular user receives a call, the PBX can fork the call to both a hard phone connected to the PBX and to a user’s Microsoft Teams client via the Ribbon Connect service. When the person answers the call, (on the phone connected to the PBX, or on a Teams client or device) the call remains anchored in the PBX, which allows for some interesting presence scenarios.
If a user picks up the call on their Teams client, all PBX users will see that the user is in a call, and all MS Teams users will see that the person is in a call. Likewise, if a Teams user makes a call to the PSTN, other Teams users and PBX users can see that the person’s phone is “off hook,” and presence works correctly on both sides. The only time presence is inaccurate is when a user answers on a phone connected to the PBX; in this case, the Teams users won’t see that the person is in a call.
Perhaps more importantly than the presence information is the ability to call and transfer calls between users connected to the PBX and Microsoft Teams users. If someone on the PBX needs to call a Teams user (internal call), they can still dial the user’s extension. Conversely, if a Teams user must call the help desk, security, or another familiar internal number, these calls will work seamlessly. Calls can also be transferred between phones connected to the PBX and phones/clients on Microsoft Teams. This means that a live receptionist on the PBX can transfer a call to a Teams user exactly as before, even though the call may ring a user’s Teams desktop or mobile client thousands of miles away. One caveat, however, is that Microsoft Teams users who wish to transfer calls from their client back to a PBX user must use a “star command” to transfer the call to a PBX-tethered device.
Hunt groups also work because the PBX anchors the call and knows everyone in the hunt group's extension. When a call is sent to the hunt group, the PBX seamlessly forks the call to ring both a person’s PBX-tethered phone (if they have one) and the person’s softphone device, which is really Ribbon Connect, and Ribbon Connect sends the call to the person’s Microsoft Teams Phone System, which in turn rings the person’s Teams clients or phones. Users in a hunt group can answer on any device.
The Key Takeaway
Ribbon Connect provides a practical way for organizations that still require PBX telephony capabilities to migrate some or all of their employees to Microsoft Teams while maintaining use of the PBX. A scenario like this enables an effective migration strategy for organizations that still have PBX assets to depreciate and use, as well as those with telephony-centric business processes that require communications between users connected to the PBX, Teams, or both.
Ribbon Communications has also created tools to auto-configure the Microsoft Teams Phone System environment based on the parameters programmed into Ribbon Connect. A PBX administrator must enable forking in the PBX so that calls are properly routed to Ribbon Connect and Teams.
Ribbon Connect is available through Ribbon partners and offered as a service for a monthly fee per user. There is no lower limit as to the number of people that can subscribe to the service, so an organization can start with as few as one Microsoft Teams test user and gradually increase the number of Teams users from there.

Learn more about Microsoft Teams Direct Routing at Enterprise Connect this September in Orlando, Fla. Register with promo code NJAL200 and receive $200 off your registration.