Fix RDP sessions freezing or black screen at logon

Several causes for this issue exist, most famously the Windows 10 version 1809 & Windows 11 version 22H2 feature updates.

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Fix 1

This disables use of UDP on the client, forcing a TCP connection.

1. In the client’s registry, go to
   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\Client
2. Create a new DWORD value named fClientDisableUDP with data of 1
3. Reboot the client

1. In the client’s registry, go to
   HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services\Client
2. Create a new DWORD value named fClientDisableUDP with data of 1
3. Reboot the client

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Fix 2

This disables URCP (Universal Rate Control Protocol) on the server.

1. In the server’s registry (or session hosts if in a farm), go to
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Terminal Server Client
2. Create a new DWORD value named UseURCP with data of 0
3. Reboot the server or session host

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See also:

• https://serverfault.com/questions/945591/rdp-over-udp-failing-on-windows-10-1809-with-reduced-mtu-links
• https://itcalls.net/windows-10-version-1809-black-screen-when-connecting-rdp-to-server-2019/
• https://answers.microsoft.com/en-us/windows/forum/all/issues-with-remote-desktop-on-windows-11-after/2f0b90c8-9549-46bb-bede-41c2d3990380