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Title
How To: Improve Performance to a Virtual Desktop VDI Session -
Description
When connecting to a VDI over a slow connection users report that the performance on the VDI is degraded, or sessions are disconnected often.
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Cause
This can sometimes be caused if the Maximum Transmission Unit (MTU) of the VDI is being fragmented. As RDP packets cannot be fragmented this can lead to poor performance and disconnections.
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Resolution
To verify that the above may be the cause of this issue perform the following:
*Disclaimer – Quest does not provide support for problems that arise from improper modification of the Operating System and the below steps are for informational purposes only. For additional information on the MTU contact Microsoft for assistance.
- Install a Network Analyzer on the Client Workstation (For Example: Wireshark)
- Capture the traffic that occurs when the user has a connection going to the VDI
- If you see any [TCP segment of a reassembled PDU] messages this May (not always) indicate fragmentation.
- If the frame (bytes on the wire) is larger than the MTU however fragmentation may be the issue.
- Disconnect from the VDI session and close any network analyzer software
- Open a Command Prompt from the users workstation
- Enter the following command (Without the “”)
“ping –l 1514 –f VDIHOSTNAME”
- Where the –l is the length of the bytes on wireshark
- Where the –f will prevent it from being fragmented
- Where the VDIHOSTNAME is the name of your VDI
- Is the ping successful? If not, keep lowering the –l value until the ping is successful.
- Once you have the –l value that is successful, change the MTU on the VDI and restart the VDI
- After restarting the VDI, attempt to connect from the Workstation to see if performance has improved.
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Additional Information
https://social.technet.microsoft.com/Forums/windowsserver/en-US/ab950c6e-847a-4f51-bc15-b9f54793787c/mtu-remote-desktop-services-random-disconnects?forum=winserverTS http://en.community.dell.com/techcenter/virtualization/vworkspace/b/vworkspace-blog/archive/2011/06/14/mtu-size-mismatch-a-major-cause-of-disconnections http://www.gossamer-threads.com/lists/cisco/nsp/110209