Cloud, Hybrid, or On Premise? Where’s the Skype for Business PBX?


I’ve recently taken an interest in the many different voice deployment options available with Skype for Business.  Traditionally this would mean an on premise deployment with on premise PSTN breakout however in recent years cloud based pbx functionality has become a reality, although at this point in time, not all deployment types are created equal. Depending on what feature set is required Skype for Business may be deployed on premise, hybrid, or online.  Some of the deciding factors when choosing which deployment model that will suit your needs best are what call control and features are required, and does your Office 365 tenant provide PSTN calling services.

Voice deployment options include

  • On Premise Enterprise Voice
  • Cloud PBX with PSTN Calling Services
  • Cloud PBX with On Premise PSTN Connectivity that include a couple of variations
    • Skype for Business Cloud Connector Edition
    • Existing On Premise Deployment

Some basic questions that can help decide on what deployment solution is best for you include

  1. Is an advanced call control feature such as response groups required?  If so then these accounts must be homed on premise.
  2. Is the Office 365 deployment in a region that offers PSTN calling?  Not all regions currently support this feature, including Australia.
Basic vs Advanced Call Control 

Because on premise and online feature parity does not currently exist it’s extremely important to have user accounts homed in the correct location.  Whilst basic call control is possible on premise and in the cloud only an on premise deployment can cater for advanced call control and full Skype for Business feature set.  Some of the differences include –

Basic Call Control (On premise & online)

  • Call Initiation/Call Answering
  • Call Forwarding/Simultaneous Ring
  • Call Hold/Call Retrieve
  • Call Delegation
  • Call On Behalf

Advanced Call Control (On premise only)

  • Response Groups
  • Call Pickup Groups
  • Call Park
  • Auto Attendant

Deployment Options

On Premise 

All Skype for Business server roles are deployed on premise.  This may include standard or enterprise edition servers with on premise PSTN connectivity.  This is the only option that should be considered if advanced call control is required for all accounts.  In addition to advanced call control an on premise deployment caters for additional functionality such as PIN authentication, common area phones, and privates lines.

In Summary

  • All Skype for Business server roles deployed on premise
  • Users homed on premise
  • All Skype for Business features and call control available
  • PSTN connectivity is located on premise
Cloud PBX with PSTN Calling Services

Full cloud deployment utilising Office 365 and Skype for Business Online.  Users are homed in the cloud with basic call control, and through an additional add-in PSTN connectivity is provided by Microsoft.  This option is appealing if no on premise deployment is required.  Keep in mind some of the limitations include

  • Only basic call control functionality and limited feature set is available.
  • Availability restricted to US, Puerto Rico, and UK
  • PSTN connectivity provided by Microsoft.  Do not expect to be able to route calls via on premise PSTN.
Cloud PBX with On Premise PSTN Connectivity – Skype for Business Cloud Connector Edition 

This deployment option should be considered if not all Skype for Business features including advanced call control is required.  This is a hybrid deployment with all Skype for Business accounts located in the cloud whilst PSTN connectivity is provided on premise.   On premise a minimal Skype for Business topology is deployment called cloud connector edition that consists of a CMS role, Edge, and Mediation component.  This option will suit if

  • All users will be located in the cloud
  • Advanced call control features not required
  • No existing on premise Lync or Skype for Business deployment
  • Want to continue using existing carrier
  • PSTN Calling services not available in Office 365 region
Cloud PBX with On Premise PSTN Connectivity – Existing On Premise Deployment 

This deployment option should be considered if an existing on premise deployment including PSTN connectivity is currently in use and you’d like to migrate some or all accounts to the cloud.  The on premise deployment is stretched to include Office 365 and  accounts can be enabled in either environment.  Accounts homed on premise still have the full feature set whilst cloud based accounts do not and this should still be the main consideration on where you’ll place each account.  This may be the ideal solution if only the basic feature set is required for all or some accounts, or if you’d like to dip your toes into the cloud pbx environment for testing purposes.   This deployment may consist of

  • Users located on premise and in the cloud
  • Hybrid deployment consisting of an on premise deployment and Office 365.
  • Accounts requiring full functionality homed on premise
  • Accounts requiring basic functionality homed in the cloud
  • PSTN calls route via on premise and where PSTN calling services not available
So what’s the answer? 

I think there’s a small number of questions that help decide how you will deploy Skype for Business

  1. Do I require advanced call control and all features available with a Skype for Business deployment for all accounts?  If yes then you’d want to deploy both Skype for Business and PSTN connectivity on premise
  2. Is PSTN calling services available in my region?  If no then there is no other choice than to have an on premise or hybrid deployment.   Accounts could be located either on premise or in the cloud depending on required functionality and PSTN connectivity would be provided on premise.
  3. Is this a new Skype for Business deployment and do I only require basic functionality?  If yes and you reside in a region providing PSTN calling then all services can be located in the cloud.  If PSTN calling services do not exist in your region then a hybrid deployment with cloud connector edition would suit.

For more information on what features are available when accounts are enabled in the cloud visit –