The MIT-SUNDRY-NONSTANDARD extension was developed at MIT and does not have a standard, or specification, on the ftp.x.org machine. This extension handles miscellaneous erroneous protocol requests from X11R3 and earlier clients. It provides a request that turns on bug-compatibility mode so that certain erroneous requests are handled or turns off bug-compatibility mode so that an error for erroneous requests is returned. The extension also provides a request that gets the current state of the mode.
This extension can be dynamically turned on or off with xset, or at server startup with openwin. See the xset(1) and openwin(1) man pages, specifically the -bc option, for more information.