Oct 12, 2016

How To Fix Slow SSTP RRAS VPN on a Citrix XenServer Virtual Server

Ever since moving to Windows 10 and Windows 2012 R2 we've seen a serious drop in performance when using SSTP (Secure Socket Tunneling Protocol) on our Windows 10 machines. After weeks and weeks of troubleshooting, we believe we have the issue narrowed down to some NIC and registry settings on the RRAS (Routing and remote Access).

NOTE: This is for virtual servers that run on Citrix XenServer. Some of these things may be different in your environment...

The first thing you need to do is go into the device properties of you NIC and select the configure button. Under the Advanced tab disable all of the "offload" settings.

The next thing you need to do is make the following registry changes:
  • Set DWORD value EnableTCPA=0 in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
  • Set DWORD value DisableTaskOffload=1 in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
  • Set DWORD values TcpAckFrequency=1 under every interface GUID under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces
  • Reboot 
After doing all of that we saw a significant performance increase in file transfer speed and general network performance.

Give it a try, and let us know in the comments if it worked for you or not. If not, let us know what you had to do differently!

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