If you are using WCAT to stress test your IIS application you can use the logfiles of IIS to create the UBR file that WCAT uses with the help of Logparser:

logparser file:.SamplesTemplateFileswcat.sql -tpl:.SamplesTemplateFileswcat.tpl

This creates a stresstest.ubr

You can tweak the SQL file…

Start WCAT Controller with:

wcctl.exe -z stresstest.ubr -n Server -a Server

And the WCAT Client with:

clientloop.cmd Controller

Source

http://www.iis.net/default.aspx?tabid=2&subtabid=26&i=5
http://www.iis.net/downloads/default.aspx?tabid=34&g=6&i=1466