TFTP downloads failing after WDS update KB4503267

Question

_{Tuesday, July 16, 2019 9:09 AM}

KB4503267 is meant to fix problems with TFTP downloads with Variable Window = true, but over here it is causing those problems, for downloads with Variable Window = false.

This is on Server 2016.

We are using in-house designed ARM CPU devices booting from the network. They are built up around a Digi ConnectCore 7U module running an image built on Digi's own Net+OS. The boot loader is a minimal Net+OS build that just downloads a larger image to RAM and starts it, by rebooting to that RAM image.

We have been using these devices with different TFTP servers for more than 10 years, and they have always worked fine.

Now they suddenly start booting flaky (guesstimate: about 1 boot attempt in 3 to 5 fails) and I have dozens of these in event log:

Applications and Services Logs \ Microsoft \ Windows \ Deployment-Services-Diagnostics \ Admin

Event ID = 4101

The Following Client failed TFTP Download: 

Client IP: 10.11.19.150
Filename: image.bin
ErrorCode: 644
File Size: 1002330
Client Port: 18000
Server Port: 59082
Variable Window: false

Before the update was installed I had on average less than one of these events per month, now I have dozens per day.

All replies (7)

_{Tuesday, July 16, 2019 11:35 AM}

Not a solution, but a workaround, because it was urgent:

I disabled WDS and installed the old third party TFTP server service we used in earlier versions of Windows. It's something I found on Sourceforge long ago, been using it from Windows 2000 on, it still works under Server 2016.

_{Wednesday, July 17, 2019 6:54 AM}

Hi,

Based on my research, you could try the method below:

Open Windows Deployment Services console / Right-click your WDS server in the left pane and open Properties

then Open tab “TFTP” and  uncheck “Enable Variable Windows Extension”

Restart your WDS server.

Hope these can help you.

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_{Wednesday, July 17, 2019 2:18 PM}

Thanks, but no success :(

I didn't have the user interface option because only the WDS transport server role was installed and not  the deployment server role, the console didn't detect WDS on my server, but I found this registry setting:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WDSServer\Providers\WDSTFTP

REG_DWORD value EnableVariableWindowExtension was set to 1. I changed it to 0 and restarted the WDS service, but the problem remained.

There are two more options, EnableBufferSharing and EnablePortSharing. I haven't tried turning those off yet. I'm updating a test server to try that, but that one is so slow and has been neglected for so long that it took all day so far to download and install a year's worth of updates.

_{Thursday, July 18, 2019 6:42 AM}

Tested with all three options disabled now, still no success.

_{Thursday, July 18, 2019 8:40 AM}

Hi,

Please install the latest updates KB4507459 and try the method again.

Best Regards,

Farena

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_{Thursday, July 18, 2019 9:30 AM}

Hi Farena, thanks again for your time.

The KB article you linked to says the update can be obtained from Windows Update / Microsoft Update, but do all editions of Server 2016 get it automatically?

The affected systems are running Server 2016 Embedded, and I do not see it appear yet. The current version reported by winver is Windows Server 2016 Standard 1607, OS build 14393.3025. Check for updates says the system is up to date.

-- edit --

I downloaded the standalone installers for both updates mentioned on the KB4507459 page.

windows10.0-kb4509091-x64_1e1039047044a1f632562cd65df3ce6b77804018.msu
windows10.0-kb4507459-x64_67d347cdf1933c9da47f7e6f96424ce89debce41.msu

The filenames say windows10, but I used the server 2016 links. Both of them say they do not apply to this system.

Could it matter that these are embedded systems? Still Server 2016 Standard 1607 build 14393.3025, installed from Server 2016 Embedded installation media, and activated with a key received from the same distributor.
The Product ID is 00377-020100-33108-AAOEM.

_{Thursday, July 18, 2019 9:35 AM}

Hello,

There is similar issue on Windows Server 2012 R2 after KB4507448 update. There are dozen of messages in Event log like this one:

Applications and Services Logs \ Microsoft \ Windows \ Deployment-Services-Diagnostics \ Admin

Event ID = 4101

The Following Client failed TFTP Download: 

Client IP: 192.168.100.102
Filename: boot\x64\bootmgr.exe
ErrorCode: 644
File Size: 641880
Client Port: 2073
Server Port: 61036Variable Window: false

Workaround with EnableVariableWindowExtension is not working this time.