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Windows 10 Bits Reportedly Clogging Bandwidths on Some Networks

• By Kurt Mackie
• 08/07/2015

Recent media reports have been citing bandwidth hits from Windows 10 updates, even when PC upgrades weren't scheduled.

The bandwidth hits can be equivalent to about 3GB coming down the network pipe to some machines. Windows 10 uses a new peer-to-peer patching system that downloads OS updates into a cache on a few PCs in a network. This "Windows Update Delivery Optimization" approach is turned on by default for all Windows 10 editions and is designed to reduce bandwidth loads in a network.

However, it might have been thought that the Windows Update Delivery Optimization system would help speed updates after Windows 10 was installed, but it seems to be in effect beforehand. It's hard to say, as there doesn't appear to be much documentation about the feature. According to a Microsoft spokesperson, "Windows Update Delivery Optimization is a feature only available on Windows 10."

However, Microsoft is delivering the Windows 10 bits in advance to those users that have Windows Update turned on. Here's how the spokesperson described it:

For those who have chosen to receive automatic updates through Windows Update, we help customers prepare their devices for Windows 10 by downloading the files necessary for future installation. This results in a better upgrade experience and ensures the customer’s device has the latest software. This is an industry practice that reduces time for installation and ensures device readiness. For organizations, IT professionals can manage and control downloads on their networks.

Microsoft is ushering in a new "Windows as a service" world with Windows 10. Updates arrive when they are ready. The company has warned in its specs that Windows 10 is a 3GB download and that some devices with limited drive space might need to clear up some space to receive upgrades. Descriptions about potential network bandwidths affects, though, don't seem to be available.

However, a report by TechRepublic found at least one case where machines not scheduled to get the Windows 10 update were getting "between 2GB and 3GB" worth of files. The files are stored in a hidden folder called "$Windows-BT," according to the report. Since the machines were domain joined in this case, they weren't eligible for Microsoft's free update to Windows 10, but they apparently were still getting the bits, which was slowing down network performance, according to that report.

Possibly, the report just represents an anomaly. A search of Microsoft's community pages showed just one complaint of a slowdown, which was associated with a wireless network. However, the Patchmanagement.org community forum on Thursday was abuzz with reports of the hidden BT folder appearing on machines not scheduled get Windows 10 upgrades.

A Register story claimed that Windows 10 bits are hitting Windows 7 machines that are domain joined but it's happening in the cases when Windows Server Update Services (WSUS) isn't used to manage patches. WSUS is typically used by larger organizations with lots of machines to manage. The story pointed to a Microsoft support page indicating that two July updates need to be installed to block the Windows 10 updates via Group Policy.

A Hacker News story described the Windows Update Delivery Optimization approach as "Stealing Your Bandwidth." However, an article by Computerworld's Gregg Keizer described it as just affecting the upload portion of a network's bandwidth and not affecting download portion. Microsoft hasn't yet formally documented the Windows Update Delivery Optimization scheme, which is described as the "DoSvc" service, according to Keizer's story.

"Windows Update Delivery Optimization utilizes only a limited portion of unused or idle upload bandwidth," according to the Microsoft spokesperson.

Microsoft did publish this short FAQ page on the Windows Update Delivery Optimization approach. It includes a description of how to turn it off by changing some settings in the client OS. It also may be possible to disable it via a registry change, according to Microsoft's community forum. But that's all about turning it off after the Windows 10 bits are delivered, not stopping the bits in the first place.

Windows 10 update notifications arrive at eligible Windows 7 and Window 8.1 machines due to the presence of update KB3035583 on systems, which is otherwise known as the "Get Windows 10" app, but domain-joined machines aren't supposed to see this notice. Possibly, the bits might be stopped from arriving by uninstalling and hiding this update, but one Patchmanagement.org forum participant reported that his systems were still getting the Windows 10 BT folders installed even when using Enterprise editions of Windows 7 and Windows 8.1 without KB3035583 installed.

The mystery continues, but it seems some IT pros are getting surprised by Windows 10's arrival, even without scheduling for it.