In this post I want to show you a solution for an issue with screen sharing in an environment where a proxy is used for Skype for Business.
If you are using a Proxy in a bigger Environment for Skype for Business (not recommended from Microsoft) you may have seen the issue, that the Sharing of content is not smooth. Thats because Microsoft have changed the Way of Sharing from the Server side. Until September 2016 they have used RDP which is working over TCP. Now they use VBSS (Video Based Screen Sharing) which is working only with UDP. Since the most Proxy Server are not able to handle UDP Traffic there is a fallback and they use VBSS over TCP. This is causing the time lag.
So the best solution is to bypass the Skype for Business traffic. But in some Companies it is not possible or not allowed. So the only workaround is to force RDP from Client Side.
With this Registry Key you can force RDP for Screensharing in Skype for Business Conferences (not peer to peer connections)
reg add HKLM\SOFTWARE\Wow6432Node\Microsoft\Office\16.0\Lync /v EnableConferenceScreenSharingOverVideo /t REG_DWORD /d 0 /f
It is important to know, that the Conference will use RDP if one of the Clients is not able to use VBSS.
In this article you can find additional Information from Microsoft: