while replaying the recorded script can give some errors like-Error: Failed to get window size, wrong format.etc ..,

Unable to detect client version.
Warning: Extension CitrixClientImpl.dll reports error -1 on call to function ExtPerThreadInitialize
Error: Vuser failed to initialize extension CitrixClientImpl.dll in load runner

By using the Citrix protocol we can perform  the load testing in load runner

BestPractice for Citrix applications:

1. You can use "HTTP" and "Citirix" protocol together in load runner.
2. Try to keep windows in full screen mode.

Some time while replaying the recorded script can give some error too.like 

"Error: Failed to get window size, wrong format.

Unable to detect client version.

Warning: Extension CitrixClientImpl.dll reports error -1 on call to
function ExtPerThreadInitialize

Error: Vuser failed to initialize extension CitrixClientImpl.dll"

Solution:

1. Save the script after recording.
2. Go to Script directory and look for "default.cfg” file
3. Open the file into edit mode
4. Add below mentioned code in file and save it

[CITRIX]
DesktopColors=32
Colors=True Color (24 bit)
Enctyption=128 Bit
Window=1024 x 768
Latency=Use Server Default
Compression=1
Cache=0
Queue=0
Sound=Use Server Default
BitmapSyncLevel=Exact
[CommandArguments]
[ModemSpeed]
CustomModemSpeed=
EnableModemSpeed=0
EnableCustomModemSpeed=0
ModemSpeed=14400
[TIMEOUT]
Connect=180
Waiting=60
Typing=150
[FILTERS]
IncludeFiltersInList=
FilterType=0
[AED]
TempAedFile=NO_APP_AT_AED

5. Replay your script.