Video based Screen Sharing for Skype for Business Server

Video-based Screen Sharing (VbSS) in Skype For Business Server 2015 is now available for download: Skype for Business Server 2015 Cumulative Update KB3061064. VbSS is included with Skype for Business Server 2019.

Video-based Screen Sharing, or VbSS, grew out of Lync screen-sharing. The difference between VbSS and traditional screen-sharing has to do with the underlying protocols used, and what they excel at. Screen-sharing uses the remote desktop protocol (RDP), which is great at creating thousands of 1-to-1 sessions between people's computers. Newer technology, VbSS, makes use of User Datagram Protocol (UDP).

Skype for Business Server wanted to improve people's one-to-one, and their one-to-many (multi-party) conversations and meeting experiences. VbSS makes use of the media platform which relies on UDP as the underlying protocol. Its goal is to improve your video start times, the viewing quality of what you're watching (especially if what you're watching is moving fast), and reliability overall.

Part of the goal of improving screen-sharing is that transitions between VbSS and RDP are as seamless as possible when they occur. Since VbSS is an update to underlying technology that is used in screen sharing for Skype for Business Server, it may be difficult to detect which technology you're using unless you're looking at SIP details in the network traffic, or you're sharing content that is fast moving or 3-D. If for example, your workplace has numerous legacy clients, RDP is still available as a failsafe to your meetings and conversations. Skype for Business Server uses internal logic to decide which of the two methods (VbSS or traditional screen-sharing) to apply when clients connect. RDP can, and will, be substituted for VbSS when the situation calls for it, so that your viewing experience isn't interrupted.

Planning

VbSS pros and cons

Switching to VbSS aims to make three key improvements:

1. Make screen-sharing (up to 5%) more reliable compared to RDP alone.

2. Make the session setup and video experience faster compared to RDP alone (setup in half the time, with a 6:1 improvement in frames-per-second).

3. Works better than RDP in low bandwidth conditions, even when sharing high motion content, such as 3-D graphics.

Keep in mind that these numbers rely on the health and proper performance tuning of your network, and may involve networks external to your own, if your clients are on mobile devices.

You should be aware that some fidelity/crispness of your shared content is traded for reliability, speed, and efficiency. In most cases this isn't readily visible to users.

Ports and protocols

Required server ports

Server role	Service name	Port or port range	Protocol	Notes
Front End Servers	Skype for Business Server Application Sharing service	5065	TCP	Used for incoming SIP listening requests for application sharing.
Front End Servers	Skype for Business Server Application Sharing service	49152-65535	TCP/UDP	Media port range used for application sharing.

Required client ports

Component	Port range	Protocol	Notes
Clients	1024-65535	TCP/UDP	Application sharing.

If QoS is enabled for the following media ports and VbSS is also enabled, during a conference that includes desktop sharing the AS MCU uses the video port settings shown in bold below for the screen share traffic.

Important

These settings are a special case, and these exact settings must be used when implementing both of these features. This overrides other recommended settings in the documentation for QoS. For application sharing you will also need to specify ASMCUSVC.exe in the QoS GPO in addition to defining these port values.

Application Server QoS/VbSS required settings

Property	Port value	Protocol
AudioPortStart	49152	UDP
AudioPortCount	8348	UDP
VideoPortStart	57501	UDP
VideoPortCount	8034	UDP
AppSharingPortStart	40803	TCP
AppSharingPortCount	8348	TCP

Capacity planning

Each Front End Server running Skype for Business Server 2015 Cumulative Update 2 (CU2) or later supports up to 375 participants for screen sharing using RDP (though only 250 per meeting). This capacity doesn't change post-CU3, when VbSS is introduced and used.

That being said, we've done performance and stress testing in our lab, and the following measurements should also be considered regarding your own deployment (depending on usage).

Assuming:

• You're using Skype for Business Server 2015 CU2 or later in your deployment.

• All the users in your Skype for Business Server environment have screen resolutions higher than 1920x1080.

At full capacity (which as noted above, is 375 screen sharing participants per Front End Server in total, though only 250 per meeting), your Front End Server may be utilizing ~89% of the 1-Gigabit of network card. This is because the existing screen sharing technology in Skype for Business Server CU2 (RDP) transmits the on-screen content at the native resolution of the presenter's PC. So with higher screen resolutions factored in, you may already be experiencing network bottlenecks for screen sharing with Skype for Business Server 2015 CU2.

To mitigate this, one or more of the following options may be helpful:

• Upgrade your Front End Server from a 1 Gigabit network card to a 10-Gigabit Ethernet card.

• Increase the number of Front End Servers to load-balance traffic.

• Limit the bandwidth (bitrate) used for VbSS and RDP by putting a cap on the maximum bandwidth used by either channels.

Individual networks and the content being shared influence the numbers in this table. Test to establish baselines for your network or networks.

1080p Content	RDP Average	RDP Peak	VbSS Average	VbSS Peak
PPT	200 kbps	12 mbps	100 kbps	3 mbps
CAD	3 mbps	7 mbps	1 mbps	3 mbps
Video	5 mbps	7 mbps	1.3 mbps	2.2 mbps

Network bandwidth requirements for media traffic

The VbSS bandwidth is:

Video codec	Resolution and aspect ratio	Maximum video payload bit rate (Kbps)	Minimum video payload bit rate (Kbps)
H.264	1920x1080 (16:9) (The aspect ratio depends on the sharer's monitor resolution, and may not always be 16:9)	4000	1500

Clients and servers support

Video-based Screen Sharing requires Skype for Business Server 2015 CU3 or later, and a current version of the supporting clients listed in Mobile client feature comparison for Skype for Business and Meetings support.

There are situations where screen-sharing transitions to RDP, like these:

• If your account is hosted in an environment where the ASMCU doesn't meet the minimum build that supports VbSS.
• If someone who uses an older version of the Skype for Business client joins your session, for example anyone using any Windows client version that is lower than 16.0.6330.1000 for click-to-run installations or 16.0.4401.1000 for MSI installations, Skype for Business Room System V1 Devices, or Skype for Business Mobile Apps.
• If a user is sharing from the Skype for Business Web App.
• If someone is using Skype for Business on Mac and not is homed on Skype for Business Online or Skype for Business Server 2015 with the July 2018 cumulative update (or later).
• If someone starts any Program/Windows Sharing.
• If someone starts recording the session.
• If someone invokes Remote Screen Control during the session.
• Meetings with more than 250 participants (where VbSS isn't currently supported).

Once the session transitions to RDP, it won't transition back to VbSS. Again, the transition from VbSS is meant to be seamless, and, with hope, won't be easy to detect in most situations.

Note

It's not supported to block, or attempt to block, transition from VbSS to RDP in Skype for Business screen-sharing.

Enabling, disabling, and configuring VbSS

The great thing is, once you've installed the Skype for Business Server 2015 Cumulative Update 3 (CU3) or later, all your users will be enabled for 1-to-1 and multi-party VbSS by default. This may be problematic for you if you have a reason to not have this functionality enabled for all your users. In that case, you're able to use these steps to disable users (the enable users steps follow):

How to disable users from using VbSS

• You can assign a user policy that doesn't allow VbSS to any users who shouldn't be using VbSS by running this cmdlet in the Skype for Business Management Console (replace [PolicyName] with the policy you're doing this for):

  Set-CsConferencingPolicy -Identity [PolicyName] -ApplicationSharingMode RDP
  

• You also can update the global conferencing policy, which affects all users without an assigned policy:

  Set-CsConferencingPolicy -ApplicationSharingMode RDP
  

  For more information on this command, see Set-CsConferencingPolicy.

• If you need to turn off VbSS completely, you can run this command:

  Set-CsMediaConfiguration -EnableVideoBasedSharing $false
  

  For more information on this command, see Set-CsMediaConfiguration.

Note

In a multiparty Skype for Business meeting, all client endpoints will respect the policy setting for the meeting organizer.

How to enable users to use VbSS

• You can assign a specific user policy that allows VbSS to any users who need to be using VbSS by running this cmdlet in the Skype for Business Management Console (replace [PolicyName] with the policy you're doing this for):

  Set-CsConferencingPolicy -Identity [PolicyName] -ApplicationSharingMode VideoWithFallback
  

• You also can update the global conferencing policy, which affects all users without an assigned policy:

  Set-CsConferencingPolicy -ApplicationSharingMode VideoWithFallback
  

  For more information on this command, see Set-CsConferencingPolicy.

• If you need to turn VbSS back on after turning it off (it's on by default), you can run this command:

  Set-CsMediaConfiguration -EnableVideoBasedSharing $true
  

  For more information on this command, see Set-CsMediaConfiguration.

Note

In a multi-party Skype for Business meeting, all client endpoints will respect the policy setting for the meeting organizer.

See also

Skype for Business Server 2015 Cumulative Update KB3061064

Video-based screen-sharing (VBSS) is available in Skype for Business Server 2015