This command allows device and file system control functions to be transferred transparently from client to server.
| Setup Words Encoding =========================== | Description ========================================= | 
| ULONG FunctionCode; | NT device or file system control code | 
| USHORT Fid; | Handle for io or fs control. Unless bit0 of isflags is set. | 
| BOOLEAN IsFsctl; | Indicates whether the command is a device control (FALSE) or a file system control (TRUE). | 
| UCHAR IsFlags; | bit0 - command is to be applied to share root handle. Share must be a DFS share. | 
| Data Block Encoding =========================== | Description ========================================= | 
| Data[ TotalDataCount ] | Passed to the Fsctl or Ioctl | 
| Server Response ================================== | Description ================================== | 
| SetupCount | 1 | 
| Setup[0] | Length of information returned by io or fs control | 
| DataCount | Length of information returned by io or fs control | 
| Data[ DataCount ] | The results of the io or fs control |