New Teams optimization for VDI now Generally Available in Citrix environment

Today Microsoft is pleased to announce that our collaboration with Citrix on the new Teams optimization architecture based on the Slimcore media engine has reached 100% availability.
This is a major milestone for both companies, solidifying Microsoft Teams as a mission-critical application in Citrix DaaS and Citrix Virtual Apps and Desktops.

Microsoft’s collaboration with Citrix goes back to over a decade, from the good ole’ days of the Lync Optimization Pack, evolving to Skype for Business and culminating into Teams.
In this blog, I want to summarize all the info you will need as an Admin to shift gears in 2025 and start rolling out the new solution, bringing dozens of new features, improved performance, quality and reliability.

I call this the 4-3-2-1 approach, a tactical and strategical breakdown of the deployment (and yes, I take this from soccer!)

The 4 Components

The new optimization (currently available on Windows endpoints only) relies on these components, which operate in unison to deliver the new user experience.

1. Virtual Channel: our solution relies on 3 custom virtual channels hence it is critical you whitelist/allow them in Citrix Studio (machine-wide policy). This is a one-time configuration but easily missed by IT Admins.
2. Plugin: the brains behind the operation – this is a small DLL (220 KB) that is installed on the same folder as CWA and is responsible for the client-side virtual channel establishment and subsequent downloading of the new media engine, SlimCore. There are multiple ways you can deploy the plugin: CWA installer, Global App Config Service, Plugin Download Manager -ideal for BYOD- and even via Intune/SCCM. Check CTX691425 for more info.
3. New Teams: make sure you are on the latest version (24295.605.3225.8804, and client version 24110115722, as seen in Settings > About Teams). This is not only critical for the feature to work, but it will play a vital role in the future because the media engine (SlimCore) will be auto updated based on the version of Teams in the VDA
4. SlimCore: the heart of the solution. This is essentially the same media engine that native Teams desktop client for Windows uses, carved out as a ~50 MB MSIX package and kept up to date by the plugin, without user or admin intervention. Whenever Teams is updated, SlimCore will get updated.

The list is in increasing order of importance – once you take care of the Studio policy and plugins are deployed, you are halfway there.

Plugins are not designed to be upgraded every month – Microsoft will make every effort to not modify them, and they are backwards and forward compatible with Teams and SlimCore versions.

Having said that, there will be scenarios where a new plugin is needed (a new feature that required a modification, a security / CVE fix, or simply an end-of-support timeline reached for old plugins).

If #1 and #2 are met, new Teams will try to open the virtual channel in the background, while you are still optimized with the old WebRTC stack (“Citrix HDX Media Optimized”, as seen in Settings > About Teams).

If successful, it will instruct the Plugin to download (also in the background) a specific version of SlimCore from Microsoft’s public CDN.

The next time the user restart Teams, it will be optimized with the new stack (“Citrix Slimcore Media Optimized, as seen in Settings > About Teams).

The 3 Recommendations

There are three main recommendations we always make to VDI customers that are starting the rollout of the new optimization

1. Update cadence of the components
2. Policies
3. Network

It is imperative you craft an internal strategy/process that can keep Teams up to date – older versions are out of support after 90 days (clock starts ticking from the moment there is a newer version), and by extension so is SlimCore on the endpoint/thin clients.

A healthy update cycle will guarantee you are getting all the fixes and improvements that Microsoft releases continuously, while also delivering the best reliability and performance.

Both Teams and SlimCore are MSIX packages, hence governed by a certain set of GPOs/AppLocker/WDAC policies that allow/prohibit MSIX provisioning (see here).

A single Teams Admin Center PowerShell policy can enable/disable the new optimization for your entire ORG, so you can then target specific user groups progressively.

Lastly, make sure you have a conversation with your Networking team about the new solution, the importance of allowing UDP traffic and direct egress at the branch office.

We laid out the IP requirements here – and tell them you come bearing gifts: Quality of Service can now be applied to Teams traffic at the endpoint/thin client based on UDP source ports.

The 2 Systems

After you start the rollout, it is time to focus on the progression.

1. Monitoring and Preventive Maintenance
2. Reactive Maintenance

A balanced approach, combining both preventive and reactive strategies, ensures that VDI systems with Microsoft Teams run efficiently, security risks are minimized, and the organization can swiftly address any unexpected challenges.

In order to give Admins visibility, we have revamped Teams Admin Center, Call Quality Dashboard and PowerBI VDI templates to expose all the necessary information about ongoing calls, past meetings and trends/monthly reports.

If you don’t have access to these portals, make sure you engage with your Teams Admin counterpart and get the proper RBAC that matches your profile.

For example, with CQD you could create custom reports like this:
“Show me Poor Appsharing sessions by Total Stream Count for Last Month AND where one of the participants was optimized with SlimCore”.

We have documented extensively around troubleshooting, exposing information on a variety of logs, Event Viewer entries, known issues and (very soon, look for MC Post MC923415) in the Teams UI itself!

The 1 Goal for the New Optimization

A delightful User Experience is Microsoft’s and IT Admins’ number one goal.
We have added dozens of new features (full list here) that almost close the gap between a VDI and native Teams.

Our monitoring tools can give you unprecedented details on the meeting and endpoint performance (CPU, Wifi signal, Peripherals used, etc).

Soon we’ll be updating the Teams UI with a tooltip that indicates to the user if they are optimized with WebRTC or optimized with the new SlimCore stack.

We made drastic improvements in call set up times, meeting join reliability, codecs and overall quality.

An IT Admin that understands the 4 components,  implements the 3 recommendations and adopts the 2 systems as part of their strategy is fully equipped to deliver the best Teams user experience possible in a virtual desktop.

Happy holidays – from the entire VDI group here at Microsoft Teams!