Increase the Speed of PXE Boot/TFTP When Using SCCM Distribution Point

If you’re looking to improve the performance (quite significantly in my experience) of Trivial File Transfer Protocol/TFTP (in other words to improve the download speed of your SCCM boot images to your clients from the DP) you can add some registry keys on the server hosting the PXE-enabled Distribution Point to achieve this.

The two keys required (and the values I suggest using) are:

New-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\SMS\DP" -Name RamDiskTFTPBlockSize -PropertyType DWord -Value "16384"
New-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\SMS\DP" -Name RamDiskTFTPWindowSize -PropertyType DWord -Value "8"

Once the keys have been added, restart the “Windows Deployment Service Server” service and that’s you finished. 🙂

One caveat with this change is that it can also adversely affect performance and in some cases even break PXE altogether (as I found out with my Hyper-V 2012 R2 VM’s – VM’s stopped working completely while physical hardware zipped along like shit off a stick) so some tweaking of the values may be required depending on your environment. Basically one size does not fit all with this change.

Can’t find any proper information on SCCM CB but it looks like this is a supported change from looking at this TechNet post: link

UPDATE 30/09/2016 – some much better detail and testing results for this TFTP optimisation provided by Jörgen Nilsson on the excellent website – link

/ JC

This entry was posted in SCCM 2012 R2, SCCM Current Branch and tagged , , , . Bookmark the permalink.

4 Responses to Increase the Speed of PXE Boot/TFTP When Using SCCM Distribution Point

  1. Fred S says:

    didn’t seem to make a difference for us

    strangely in this link:

    it references HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\PXE as the path, not \DP. PXE is a nonexistent key in our infrastructure

  2. jonconwayuk says:

    Hi – I think this will depend on which version of SCCM you are using.

    I am using the very latest RTM version which is 5.00.8412.1000 and I have a ‘DP’ key in the registry rather than a ‘PXE’ key (You can check the version by looking at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS ‘Full Version’).

    Older versions have the PXE key in the registry. I don’t have time to attach a screenshot (I’m on my out to get drunk) but the following post has details of the same keys and shows the ‘DP’ key rather than the ‘PXE’ one in the screenshots –

    If you have the ‘PXE’ key in the registry then create the keys I have described there instead – pretty sure these registry settings have been around since SCCM 2007 (not 100% sure but I think I remember using them in the distant past) and I can assure you that in most environments they do make a huge difference. Don’t forget to restart the WDS service or alternatively reboot the server after making the changes for them to take effect.

  3. Fred S says:

    Hey and thanks for the quick response! We are on 5.0.8412.1307. The DP has the correct “DP” key. I have added the properties per the commands in your blog entry, and restarted both WDS on the DP, and then the DP server itself, but speed is same. Hmm… will have to keep investigating

  4. jonconwayuk says:

    Hey Fred – updated my post with links to another blog post with much better detail/testing. Also added a caveat about this change being unique to each environment – might need some tweaking to get the best performance.

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