TL;DR: Two Teams-on-VDI changes are converging: VMSS is already in Public Preview today as the successor to VBSS in the new VDI solution for Teams (Microsoft Learn - Screen sharing), and Microsoft eCDN is now included in Teams core license. This post previews the guidance our Support for Mission Critical (SfMC) Cloud Solution Architects (CSAs) are already walking customers through - because the cost of finding these issues in production is always higher than finding them in a pilot.
Audience: Mission Critical customers running Microsoft Teams on virtualized desktop platforms (Citrix, AVD, Windows 365, VMware/Omnissa Horizon).
TL;DR: Two Teams-on-VDI changes are converging: VMSS is already in Public Preview today as the successor to VBSS in the new VDI solution for Teams (Microsoft Learn - Screen sharing), and Microsoft eCDN is now included in Teams core license. This post previews the guidance our Support for Mission Critical (SfMC) Cloud Solution Architects (CSAs) are already walking customers through - because the cost of finding these issues in production is always higher than finding them in a pilot.
Why we’re flagging this now
SfMC exists to get ahead of changes like these. The SfMC CSA role is built on a simple principle: be a trusted advisor embedded alongside the customer team, not a reactive support line. SfMC CSAs work hand-in-hand with platform, network, security and service-ownership teams to build a deep “know-me” picture of the customer - their gold-image strategy, their VDI vendors, their peering topology, their CAB cadence, the history of what was tried and what didn’t stick. That context is the reason a readiness review lands in weeks, not months: your SfMC CSA isn’t starting from zero, they’re starting from knowing the estate.
Goodbye VBSS, hello VMSS - and it’s here now
Teams on VDI has used Video Based Screen Sharing (VBSS) for years - an efficient, encoded video stream for screen shares. That approach is being replaced by Virtual Machine Screen Sharing (VMSS) as part of Microsoft’s New VDI solution for Teams.
This isn’t a future roadmap item - VMSS is available in Public Preview today across Azure Virtual Desktop, Windows 365, Citrix and Amazon WorkSpaces, with Omnissa following. Microsoft’s guidance and support matrix is live on Microsoft Learn: New VDI solution for Teams - Screen sharing. If you have users on a pilot ring on VDI, you can light this up now, simply by activating Public Preview for them.
Spot the screen sharing stream no longer being offloaded to client side slimcoreSupport depends on three things moving together: the Teams client on the session host, the virtualization vendor’s optimization component (Citrix HDX / AVD Multimedia Redirection / VMware-Omnissa Media Optimization), and the endpoint client (Windows App, Citrix Workspace App, Horizon Client). Where any one of those lags, screen share quietly falls back to a lesser modality - users don’t raise tickets, they just tolerate worse quality.
Because VMSS is already in preview, there’s a real window to get this right before it becomes the default path. On Mission Critical engagements, SfMC CSAs are already sitting with customer teams on VMSS readiness reviews: confirming client and plugin versions across the gold-image estate, rebuilding CQD dashboards so the baseline survives the cutover, and flagging any inline network appliance that still assumes the old VBSS flow. The “know-me” picture the SfMC CSA has built up makes that work fast - they already know which plugin versions the desktop team is running and which CAB window the next image refresh lands in.
Microsoft eCDN is now in the core Teams license
Microsoft eCDN - previously a paid add-on - is now included in the Microsoft Teams core license. It’s a WebRTC-based peer-to-peer mesh that offloads large-scale town halls and live events from the corporate WAN by peering video between clients on the same site.
If the business case for the add-on never cleared, that objection is gone. But “included” doesn’t mean “working”. The failure mode we see is consistent: customers enable eCDN because “it’s free now”, but the peering never works - because the client-to-client path is blocked by security controls nobody remembers adding. The town hall runs, the WAN still saturates, the CIO asks why the thing that was supposed to fix it didn’t.
Example eCDN portal dashboardThe VDI infrastructure question
Both changes elevate something that has always mattered but rarely been tested: VDI-to-VDI network reachability. The new Teams client needs to talk to Microsoft 365 media endpoints (usually already open) and to other VDI instances on the same site for eCDN peering.
That second requirement is where customers are consistently caught out. Most VDI builds treat each session host as an island - east-west traffic between session hosts is blocked by NSG, hypervisor firewall, or micro-segmentation policy, because it was never needed. With eCDN in the box, it is now needed - and the blocks are often in places the virtualization team doesn’t own.
This is where working hand-in-hand with the customer team pays off. The SfMC CSA convenes the platform, network, and security owners, translates the platform change into each team’s language, and makes sure nothing falls through the gaps between them. The specific hostnames, IP ranges, UDP/TCP port requirements, and peering-group configuration are all on Microsoft Learn (links below) - the hard work is operationalizing them against your estate, and that’s the work your SfMC CSA is built to drive.
If two or more of these apply to your estate, book the conversation with your SfMC CSA now:
- Client version sprawl - multiple Teams versions in flight across gold images, or a long tail of unpatched Citrix Workspace App / Windows App / Horizon Client.
- Missing or partial CQD data - gaps in building/subnet mapping, “unknown” network location for a meaningful share of streams, dashboards still filtered on legacy VBSS modality tags.
- Recent east-west firewall changes - new micro-segmentation rollout, zero-trust project, or NSG rule consolidation in the last 12 months.
- Recent live-event pain - WAN saturation, buffering, or join failures on the last town hall.
- No eCDN subnet map, or a map that predates your current site/subnet topology.
- Proxy or TLS-inspection changes forcing Teams media through an inspection device rather than bypassing it.
- VPN full-tunnel without eCDN VPN exclusion.
- Upcoming large broadcast in the next 90 days.
Closing thought
VMSS is in Public Preview today and eCDN is already in your Teams license. The window to pilot, validate and harden is open right now - and it closes the moment either of these becomes the default path for your users.
That’s what Support for Mission Critical is built for: Cloud Solution Architects working shoulder-to-shoulder with your team as trusted advisors, investing the time to genuinely know your estate - your platforms, your people, your change windows, your risks - so that when a shift like VMSS or eCDN arrives, the remediation plan is already half-written. Not a ticket-shop. A partnership.
If you’re running Teams on VDI at scale and you haven’t had the VMSS + eCDN conversation with your SfMC CSA yet - that’s the next call to book.
References
- New VDI solution for Teams - Screen sharing (VMSS, Public Preview) - https://learn.microsoft.com/en-us/microsoftteams/vdi-2#screen-sharing
- New VDI solution for Teams (overview) - https://learn.microsoft.com/en-us/microsoftteams/vdi-2
- Microsoft Teams for VDI - install requirements - https://learn.microsoft.com/en-us/microsoftteams/teams-client-vdi-requirements-deploy
- Microsoft eCDN networking requirements - https://learn.microsoft.com/en-us/ecdn/technical-documentation/network-requirements
- eCDN peering groups and restrictions - https://learn.microsoft.com/en-us/ecdn/how-to/set-up-peering-groups
- Microsoft 365 URLs and IP address ranges - https://learn.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges
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