Windows 10 has been nicknamed “the last version of Windows ever”, as it follows a model called Windows as a Service: a new way of building, deploying, and servicing Windows.

Under this paradigm, Microsoft is tackling two key customer challenges:

  1. Forklift and lengthy projects for OS version upgrades.
  2. Selective patching of the OS, resulting in platform fragmentation. This in turn was the basis for many compatibility issues and system anomalies related to Windows Updates, probably causing headaches in their Support and Testing organizations.

While you should always reference Microsoft websites for the latest information related to Windows 10, I am going to summarize the relevant information so you can see what this means for your XenDesktop site. Let’s start with the new way Microsoft is updating Windows 10.

Windows 10 Servicing (aka Updates)

There are two very distinct types of updates designed to solve those customer challenges: Feature Updates and Quality Updates.

  1. Feature Updates correspond to “new versions” of Windows 10, like 1507 (aka RTM), 1511 (aka November), 1607 (aka Anniversary), 1703 (aka Creators) and 1709 (aka Fall Creators). These are the release vehicles for new features, similar to Citrix Current Release strategy. The version numbers correspond the Year/Month of the release.
  2. Quality Updates are designed to enable admins to receive a Cumulative (and superseding) update on Patch Tuesday (generally), containing both security and non-security fixes (like driver updates, Office updates, etc.) No new features are introduced.

How does the Admin get those updates? There are four ways, called “Servicing Tools”:

Windows Update, Windows Update for Business (WUB), Windows Server Update Service (WSUS) and System Center Configuration Manager (SSCM).
I’m assuming you either use WSUS or SCCM since Windows Update or Windows Update for Business are typically used by SMB companies.

Servicing Channels (aka Servicing Branches)

To align with this new method of servicing feature and quality updates, Microsoft introduced the concept of three servicing branches to allow customers to designate how often their devices are updated: Current Branch (CB), Current Branch for Business (CBB) and Long Term Servicing Branch (LTSB).

In April 2017, Microsoft announced that from 1703 onwards, new Windows 10 versions will be out in a Semi-Annual cadence, aligning with the way Office 365 ProPlus is serviced. The good news for the admin is that this cadence will run like clockwork, and predictability makes IT people happy.
However, there is one other key change – the lifespan of each new version is now exactly 18 months; no more 60-day grace periods at the end of CBBs like we had in 1507/1511/1607.In addition, in July 2017 Microsoft CB/CBB/LTSB terms were updated to Semi-Annual Channel Targeted, Semi-Annual Channel (SAC) and Long Term Servicing Channel (LTSC).

Let’s describe the three possible Servicing tracks available:

  1. Windows Insider Program (WIP): Rapid pre-release for Testing. Not for Production.
    For example, this is the version Citrix would begin the development efforts on.
  2. Semi-Annual Channel (SAC): every March and September, there will be a new version of Windows 10 – 1709, 1803, 1809, 1903, etc. These releases will be supported for 18 months.When these Builds come out, they will be known as SAC-Targeted, which are designed for Organizations to begin their Piloting process and it is also how consumers running Windows 10 Home edition get updated. After about four months and four Patch Tuesdays (could be even three months as it happened with 1703), Microsoft will likely promote it to SAC for broad deployment. Therefore SAC is declared around July and January of every year.
    For example, 1709 would become SAC (broad) in January 2018. 1803 would become SAC (broad) in July 2018. SAC is the officially “blessed for broad” release for Enterprises, though it is up to the Enterprise itself to decide. SAC releases will be the version Citrix initially supports for broad adoption.
  3. Long Term Servicing Channel (new name for the old LTSB): Available only in Windows 10 Enterprise, LTSC is designed for “specialized systems” (such as PCs that control medical equipment, point-of-sale systems, and ATMs) and other systems requiring long-term stability.

Please note that SAC-Targeted and SAC (or CB and CBB) only differ by the way they defer updates. They are the same OS just at different points in time.
In contrast, LTSC is a separate SKU/Edition and a different OS (no Edge, no Cortana, etc.). There are currently only two LTSBs, based on v1507 and v1607. The next LTSC is expected in 2019.

(Download Link for the Excel sheet)

Finally, we have all the information to tackle the big question:

How do Microsoft Servicing Channels align with XenDesktop VDA support?

All that follows applies to the VDA only, not Citrix Receiver. For Citrix Receiver info, see CTX224843.

Windows Insider Program

We validate our VDAs against the WIP Builds and SUVP Program patches preview, thanks to our rock-star Third Party Validation department in Bangalore.

For example, 7.15 (let’s call this 7.N) and 7.N+1 are currently being validated with all the 1709 tech-preview Builds.
The same will happen for “7.N+2” and 1803.
These are a few examples of what our Third Party Validation department tests:

Launch of Apps and Desktops Install Services Audio Redirection
Client Drive Mapping RTOP for Skype Session Reliability
Clipboard Session Recording Multi-stream/Multiport
Time Zone Re-direction HTML5 Receiver USB Redirection
Printer Mapping Citrix Director Local App Access
Authentication Flash Redirection Smart Card

We will document all of our findings related to Windows Insider Builds in a CTX Article (CTX224843).

Semi-Annual Channel Targeted (SAC-Targeted)

Citrix will only provide configuration support for a Windows 10 SAC-Targeted with XenDesktop.  During the SAC-Targeted phase the Windows 10 release is still subject to multiple hotfix changes that could impact the overall performance of basic XenDesktop functionality such as app launch.

For example, our CR after 7.15 (let’s call it 7.N+1 for simplicity, scheduled in Q4) will fall exactly in the middle of 1709 SAC-Targeted phase. Therefore, we will support 1709 SAC-Targeted on 7.N+1 only if the Service Request is opened because of a configuration issue.

In other words, we will eventually fix the issue (if it is not configuration-related) but it might require you either wait for the SAC (broad, so we can work with Microsoft and give them time to create the patch) or upgrade to the next XenDesktop CR.

Once 1709 becomes SAC (broad) around January 2018, we might state that 7.N+1 supports that version and list all the known issues in a CTX article, pending on how our internal testing goes, but I recommend then to jump into the next CR which has been tested on 1709 for longer (via the Windows Insider Program and the entire SAC-Targeted Channel).
If you are on 7.15 LTSR, then the vehicle we will use if changes are required will be the Cumulative Updates (CU).

So, the next XenDesktop CR (7.N+2) scheduled for Q1 2018 will fully support 1709 SAC (broad).

Having said that, Citrix will go above and beyond to claim day-one support of a new SAC-T Windows 10 version with our latest CR at that time (or LTSR).
For example support of 7.15 (released in August 2017) with 1709 SAC-T (released in October 2017). But if something went wrong, we will document it in CTX229052. We will then work with Microsoft to get things fixed asap via a Patch Tuesday before SAC-T is declared Broad.

Semi-Annual Channel

Citrix plans to fully support SAC (broad), including code changes (a.k.a Maintenance).
Any Windows 10 that becomes SAC (broad) will be officially supported in a XenDesktop release that shipped after the SAC declaration.
For example, 7.15 (released in August) supports 1703 SAC (broad) released in July.

A XenDesktop release that is shipped before a Windows 10 version became SAC is not “forward compatible” automatically.
For example, 7.14.1 released in May supports 1703 when it became SAC (broad) in July, with caveats:
Customers will need to validate (CTX223074) there are no known issues already addressed with a newer VDA version if available (like 7.15).

What we want to prevent is a situation like this one: based on CEIP Data for 1703, I can see that many Customers are installing XenDesktop CRs that pre-date the 1703 version. Engineering has never tested 7.11/7.12 with 1703 SAC for obvious reasons (was not available; 7.13 + 1703 received some testing via Windows Insider Builds).
The first SAC-Targeted version we had a real chance to test was 7.14.1, and that is the first version you should be testing/piloting.

Long Term Service Channel (LTSC)

Citrix strongly recommends that if you run LTSC (previously LTSB), you should plan on adopting a XenDesktop Long Term Service Release (LTSR), since the combination of Microsoft LTSC with Citrix LTSR gives you the longest product lifecycle and the greatest amount of predictability.

Windows 10 Upgrades

So the last topic I want to cover is the upgrade from one Windows 10 version to the next.
Do I need to uninstall my VDA, upgrade the OS, and reinstall all the Citrix Software?
All our findings are documented in the following CTX Articles:

 From↓\To→ 1507 1511 1607 1703
1507 n/a n/a CTX216312 CTX223074
1511 n/a n/a CTX216312 CTX223074
1607 n/a n/a n/a CTX223074

Our parent CTX Article for anything Windows 10 CTX224843.

Final words:

Our position up to now has been to not support CBs. After working with Microsoft to align our release strategy, we decided Citrix should be part of the piloting process together with our Customers, and have now expanded our coverage to include SAC-Targeted. Very likely, our lifecycle will evolve towards one objective: making it easier for you to adopt newer technologies from both Citrix and Microsoft at the same time on a united path.

Change is the only constant in Agile releases!

Full Disclaimer: Any reference to a XenDesktop version or release date is purely tentative and for clarity only.
Citrix does not commit to any release date stated in this blog.