Tom Talks Microsoft Teams and Microsoft 365 news and opinions

Know The 5 Types of Hybrid for Skype for Business and Microsoft Teams

“Hybrid” is possibly the most overused word in our Microsoft world. It means everything and nothing. I often cringe when people talk about their topology as “hybrid” without defining it further, I even try to ban using “hybrid” without any context at Modality :-).

So why am I not a fan? Many different Skype for Business and now Microsoft Teams topologies are referred to as hybrid with quite different functionality. Beyond Microsoft UC “hybrid” is also used in Exchange, SharePoint and other workloads. So here is a quick breakdown of the different types of Skype for Business and Microsoft Teams “hybrid” and what I believe is the correct name to use to refer to them (IMHO).

If you have 100% SfBS and Exchange UM On-premises, or 100% SfBO/Microsoft Teams and Microsoft PSTN Calling plans, you are not hybrid, and things are nice and easy. For the uninitiated “hybrid” means some workload(s) on customer premises (or hosted by a partner) and some workloads in Microsoft Office 365. Here are the 5 types:


EXO UM: Skype for Business Server and Exchange Online Unified Messaging


In this scenario, all users are homed on-premises on Skype for Business Server, but their voicemail is routed via an Edge server to Exchange Online Unified Messaging, which “answers” the call, records the message and puts it in an Exchange Online User Mailbox.

Where this makes sense?

  • I have some/all my mailboxes in Exchange Online but have Skype for Business Server
  • Exchange Online UM can be used for any SFBS Users in any topology with SFBS. SFBO/Teams users always use Azure Cloud Voicemail.

Blog: Configuring Skype for Business Server with Exchange Online Unified Messaging

Side note, you used to be able to connect third-party IP PBX’s to Exchange Online Unified Messaging, but this has now been depreciated.


Split Domain: Skype for Business Server and Skype for Business Online for the same SIP Domain(s)


In this scenario, Skype for Business Server and Skype for Business Online are set up to work together in the same topology, users can be homed either on Skype for Business server or Skype for Business Online, with the same SIP domain, and can communicate seamlessly.

Where this makes sense?

  • I want to have some users homed in Office 365 to reduce SfBS Server/take advantage of cloud scale/Cloud PSTN Audio Conferencing/Cloud Evergreen service
  • I have some requirement for users to be on SfBS, compliance call recording, specific application integrations, response group use cases, Survivable Branch Appliances
  • I get the benefits of the cloud where it makes sense, and all the features of SfBS, but also all the complexity of running both.
  • Supports a gradual migration from SfBS to SfBO

“Split domain” does not define where PSTN (telephony) is connected or even which features/modalities are enabled in SfBS and SfBO, so whenever someone says they are split domain there are some follow-up questions/options

  • SfBS users can only consume user PSTN connectivity and PSTN conferencing connectivity via SFBS, likely on-premises gateways and SIP or ISDN connectivity
  • SFBO users can consume user PSTN connectivity via Microsoft user PSTN Calling Plans in Office 365 or via the SfBS servers (see On-Premises Call Handling)
  • SFBO users can only consume PSTN Conferencing via Microsoft Audio Conferencing or a certified third-party Audio Conferencing Provider (ACP)


OPCH: On-Premises Call Handling


A bit of a Microsoft insider phrase. This is specifically a setup for SFBO users routing their user PSTN calls via SfBS. Therefore it’s a configuration option when you have a Split domain setup. Indeed you may set up a Split domain and have 100% of your users on SFBO with OPCH; it’s technically still split domain.

The acronym is saying users calls are handed via SfBS On-Premises

Where does this make sense?

  • I already have an investment in SfBS On-Premises with PSTN Gateways but want to move users to the cloud for their main services and conferencing
  • I want to use SFBO with PSTN connectivity in a country Microsoft PSTN Calling Plans do not service and already have SFBS somewhere in my global topology
  • If there are any SfBS (or Lync 2013) in a customers topology, this is the only option to “Bring their own user telephony/own carrier” to SfBO users. CCE cannot be used alongside SfBS.
  • Requires SfBS servers to be licenced.

This is only for routing user PSTN connections, Cloud PSTN Conferencing and Cloud Auto Attendants/Hunt Groups require numbers from Microsoft (you can potentially 1:1 forward to from your PSTN numbers to Microsoft numbers)


CCE: Cloud Connector Edition


In this scenario, 100% of users are on SfBO, but a specific appliance, the “cloud connector edition” allows the customer to connect their own PSTN carrier for user numbers to SfBO. Cloud Connector Edition can be installed on a commodity server or can be bought in an appliance from AudioCodes or Sonus.

Where does this make sense?

  • I want SfBO but want to bring my own PSTN carrier
  • I have no requirement in my topology for SfBS
  • CCE itself requires no additional licence beyond having an active SFBO user licence, but if you deploy your own on a commodity windows server you do need to licence Windows Datacenter Edition

CCE cannot be used if there is any SfBS or Lync 2013 in a customers topology, so cannot be used alongside any SfBS or Split domain.


Microsoft Teams Direct Routing

AKA names while in development: Hybrid Voice Connectivity, Bring Your Own Trunk (BYOT), Direct Connection For Microsoft Teams


Still a roadmap item. So there is limited public information available and a few names floating around. What has been shared is that this will allow customers to “bring their own user PSTN” for Microsoft Teams users. It will use certified Session Border Controllers from Ribbon (previously called Sonus) and AudioCodes which will connect directly to the Microsoft Teams cloud service. It will not require a windows server(s) like CCE.

Where does this make sense?

  • I am using Microsoft Teams and want to bring my own user PSTN connectivity


  • This can be deployed alongside other SfBS/SFBO/CCE topologies
  • AudioCodes and Sonus have confirmed CCE appliances will also be able to work in this model
  • This is only for Microsoft Teams, not SfBO
  • Currently on the roadmap for Q2 2018 (end of July)
  • Since SBC’s can connect directly to the service, I would anticipate Telco’s offering this as a service with no need for a customer to have an on-premises SBC


So hopefully you are now armed with the different types of “hybrid” and can explain the differences.

Thanks to this document from Microsoft for the graphics I adapted: Plan your Skype for Business hybrid deployment

Any questions welcome


About the author

Tom Arbuthnot

A Microsoft MVP and Microsoft Certified Master, Tom Arbuthnot is Principal Solutions Architect at Microsoft Collaboration specialists Modality Systems.

Tom stays up to date with industry developments and shares news and his opinions on his blog, Microsoft Teams Podcast and email list. He is a regular speaker at events around the world.


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Tom Talks Microsoft Teams and Microsoft 365 news and opinions