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 –

Lync 2013 & Skype for Business side by side deployment

If an environment has an existing Lync deployment a number of options exist to introduce Skype for Business Server –

  • In place upgrade
  • Side by side deployment

In place upgrade provides a method to upgrade existing Lync 2013 servers so they become Skype for Business servers.  By doing so less work is required than a side by side deployment as no need exists to deploy a new environment from scratch.

Side by side deployment contains existing Lync 2013 environment and introduces Skype for Business Servers.  This method requires additional resources and time to deploy, migration of accounts and other items such as CMS, response groups, etc and then decommission the legacy environment.

This raises the question why would anyone want to do a side by side deployment when in place saves time?  There’s a number of reasons including

  • Risk adverse to upgrading production environment where failure could cause system disruption impacting staff.  You may have a single pool (or server) or you’re worried no pool pairing during the upgrade is too great a risk.
  • Existing deployment uses Windows Server 2008 R2.  Whilst in place upgrade will work with this server version it’s time to move on.
  • Existing telephony environment utilises RCC (remote call control).  Skype for Business server does not support RCC so those requiring this feature need to remain homed on Lync 2013.
  • Server, DNS, and certificates names reference Lync 2013 environment.  (OK, cosmetic only however I’d find this annoying!)

This article will not describe a full migration as it is only concerned with adding Skype for Business Server into a Lync 2013 environment.  The goal is to have enabled accounts on both systems able to view presence, send IMs, and share desktops.

Adding a Skype for Business Standard Edition Pool

Install prerequisites.  
Using powershell install required Windows features
Add-WindowsFeature NET-Framework-Core, RSAT-ADDS, Windows-Identity-Foundation, Web-Server, Web-Static-Content, Web-Default-Doc, Web-Http-Errors, Web-Dir-Browsing, Web-Asp-Net, Web-Net-Ext, Web-ISAPI-Ext, Web-ISAPI-Filter, Web-Http-Logging, Web-Log-Libraries, Web-Request-Monitor, Web-Http-Tracing, Web-Basic-Auth, Web-Windows-Auth, Web-Client-Auth, Web-Filtering, Web-Stat-Compression, Web-Dyn-Compression, NET-WCF-HTTP-Activation45, Web-Asp-Net45, Web-Mgmt-Tools, Web-Scripting-Tools, Web-Mgmt-Compat, Server-Media-Foundation, BITS

Create File Share
Create directory, share, and ensure correct permissions.  This lab environment will utilise a share on the local c drive of the Skype for Business server.  Microsoft recommend DFS as it provides high availability.

  1. Create directory
  2. Right click directory > properties > sharing > advanced sharing > share this folder
  3. Permissions > Add an administrator account with full control, change, read permission.

Install Administration Tool
From Skype for Business setup media run installation.

  • Installs Microsoft Visual C++ 2013.
  • Ability to have setup connect to internet to download and install updates.
  • This lab environment will install Skype for Business to default location
  • Lync 2013 is already installed Active Directory requires no further preparation
  1. Accept license terms
  2. Select Install Administrative Tools.  These tools include Topology builder.

DNS Records
As this is a simplified Std Edition deployment only a small number of DNS records were required (both records resolve to Lync 2013 standard edition server) –

  • A Record – sip.nomoredeskphone.local
  • SRV record – _sipinternaltls._tcp.nomoredeskphone.local

Topology Builder
This is where the fun begins! Defining topology.

  1. Run Topology Builder and download initial topology.  This contains the existing Lync 2013 deployment and now additional Skype for Business container.
  2. Expand Skype for Business Server > Skype for Business Server 2015
  3. Right click Standard Edition Front End Servers > New Front End Pool > Next
  4. Enter FQDN of server to add.  E.g. skype.nomoredeskphone.local.  Ensure this matches the DNS FQDN of the server otherwise server installation fails.
  5. Select components to install on front end server.  Whilst not required I am going to add enterprise voice as I intend on using it at a later stage.
  6. Select Collate Mediation Server
  7. No Edge server required for this lab.  For any production environment I recommend configuring the internal pool prior to attempting edge deployment.
  8. Accept SQL Express default installation options.
  9. Enter file share details.  Ensure directory, share, and permissions prior to this step.
  10. For this lab I have kept the base URL as is.  This would be modified in a production environment to represent the URL exposed by a reverse proxy however I do not intent to deploy external connectivity.
  11. This lab will not require Office Web Apps server therefore it is not selected
  12. A basic Skype for Business Server topology is ready to be published
  13. Select Action > Topology > Publish…
  14. Topology Builder proceeds to publish topology
  15. Take note of results when publishing complete as this screen may display errors.  Additional information may be displayed such as next steps ‘to-do list’ as per example below.
  16. Open to-do list for additional instructions

    Note – Remove Lync 2013 topology builder.  From this point onwards the topology should only be updated using Skype for Business topology builder

Skype for Business Standard Edition Installation

Local Configuration Store Installation

  1. Open Skype for Business deployment wizard
  2. Install or Update Skype for Business Server System
  3. Install local configuration store > Run
  4. Retreive directly from CMS store > Next
  5. Finish

Set or Remove Skype for Business Server Components

  1. Setup or Remove Skype for Business Components > Run
  2. On first screen select Next
  3. Finish


  1. Request, Install, or Assign Certificates > Run
  2. Select Default Certificate > Request
  3. Select CA and select sip domain(s).  Will be using standard web server certificate template for this request > Next
  4. Review Certificate details > Next
  5. When request is complete select Next
  6. Assign this certificate is selected by default > Next
  7. Certificate is assigned > Next
  8. Review summary of certificate to assign > Next
  9. Next
  10. Select next on certificiate assignment summary
  11. Finish

There is no need to assign an OAuth certificate as this was created during the initial Lync install, is still valid, and automatically replicates between servers.

Start Services
Unlike Lync 2013 the deployment wizard will not start services and this is performed using powershell.


  1. Open powershell and run the following command



  1. When prompted enter pool fqdn



Initial startup takes a few minutes.   This completes how to add Skype for Business into a Lync 2013 environment however work isn’t complete as accounts and other things such as CMS, response groups still need to be migrated.  More on those items later.