Product Documentation


Aug 14, 2017

For access to this version of  the RealTime Optimization Pack features, upgrade your Skype for Business 2015 to the June 2016 PU (15.0.4833.1001) or subsequent PU or your Optimization Pack 1.x to this version.

Optimization Pack 2.x to this version

Optimization Pack supports flexible upgrade from earlier 2.x Optimization Pack versions to this version. To upgrade from previous Optimization Pack 2.x versions to this version, be aware of the following considerations:

  • To upgrade the Optimization Pack to this version, upgrade Skype for Business 2015 to minimum Product Update 15.0.4833.1001 or Skype for Business 2016 to minimum Product Update 16.0.7341.2032 (for Click-to-Run).
  • You can upgrade RealTime Connector from a previous 2.x to this version without immediately upgrading the RealTime Media Engine 2.x on the endpoints. You must update the RealTime Media Engine eventually to receive all the new features and fixes to known issues. This information applies to major, minor, and patch releases.
  • You can upgrade the RealTime Connector and Skype for Business independently:
    • Upgrade the previous RealTime Connector 2.x to this version, and then upgrade Skype for Business 2015 to at least June 2016 Product Update 15.0.4833.1001. For Skype for Business 2016, you must upgrade to minimum Product Update 16.0.7341.2032.


    • Upgrade Skype for Business 2015 to the June 2016 Product Update or subsequent Product Update. Then upgrade the RealTime Connector 2.0.x or 2.1 to this version. For Skype for Business 2016, you must upgrade to minimum Product Update 16.0.7341.2032.
  • When doing a staged upgrade for a minor or major release (for example, from 2.0 to this version), upgrade RealTime Connector first, before RealTime Media Engine. Otherwise, you get fallback behavior rather than optimized behavior.
  • Upgrades to a patch release (for example, 2.x to 2.x.100) can be done in either order.


If you are upgrading from 1.x, you must upgrade both RealTime Connector and RealTime Media Engine to retain optimized operation.

Upgrade requirement for Linux

If you are running the 32-bit Citrix Receiver for Linux and 32-bit RealTime Media Engine on 64-bit systems, you can use the 32-bit RealTime Media Engine package to upgrade.

If you want a 64-bit RealTime Media Engine, first uninstall both 32-bit Citrix Receiver for Linux and 32-bit RealTime Media Engine. Then install the 64-bit Citrix Receiver for Linux, version 13.2 or later and 64-bit RealTime Media Engine

Optimization Pack 1.x to 2.x

During 2015, Citrix and Microsoft co-developed a new architecture for delivering Skype for Business in virtualized environments. This new architecture provides smooth upgrades from one 2.x release to the next. It does so by allowing customers to upgrade the RealTime Connector on the XenApp and XenDesktop servers before upgrading the RealTime Media Engine on all user devices. But upgrading from the original 1.x to 2.x is more challenging because 1.x versions of the RealTime Media Engine aren't compatible with the RealTime Connector 2.x. Therefore, during the interval between upgrading the RealTime Connector and upgrading the RealTime Media Engine on user devices, optimized delivery of the Skype for Business client isn't possible.

For the smoothest possible upgrade, we recommend using Electronic Software Delivery mechanisms to update the RealTime Connector and the RealTime Media Engine on user devices. Execute the upgrades as close to simultaneously as possible. To manage server load if some users require Skype for Business audio-video services while a major version mismatch exists between RealTime Connector and RealTime Media Engine, the RealTime Connector provides fallback controls (introduced in the 2.1 release). These controls enable administrators to configure whether to deny audio-video service totally until the RealTime Media Engine is upgraded to 2.x, permit only audio, or permit both audio and video. Server-side video processing has the greatest impact on CPU usage and server scalability.

Microsoft Lync VDI plug-in migration to Optimization Pack

Citrix and Microsoft collaborated on a "version 2" architecture for delivering the Skype for Business client from XenApp and XenDesktop. This collaboration culminated in the HDX RealTime Optimization Pack 2.0 release in December 2015 and a corresponding update to the Skype for Business client. Previously, Microsoft promoted a "version 1" solution consisting of a Citrix Receiver for Windows plug-in called the VDI plug-in.

The Lync 2013 client version 15.0.4859.1002 (released in September 2016) includes an enhancement to support co-residency of the Lync VDI plug-in with HDX RealTime Media Engine 2.2. This enhancement assists migration. The migration procedure:

  1. Apply all the latest updates for the Lync/Skype for Business client on the XenDesktop server and for the Lync VDI plug-in on the users Windows devices. Migration support is available only with the latest updates for both components. Ensure that the client is running in Skype for Business UI mode. This version of the Optimization Pack supports only this mode.
  2. Deploy this version of the RealTime Media Engine on the endpoints in parallel with the Lync VDI plug-in. At this point, the Lync VDI plug-in is still used for audio/video calls.
  3. Deploy the RealTime Connector for Skype for Business on the XenDesktop server. At this point, the system switches to using the Optimization Pack for audio/video calls.
  4. Uninstall the Lync VDI plug-in from the Windows devices.