Where are the spool files stored for network printers?

Hi, there:

I know when I print a document like word by a local printer, I can see the
windows will save the temporary two spool files in the defaultSpoolDirectory
(C:\windows\system32\spool\Printers) and delete them after print job
finished. But if I use network printer with the same default path, I can't
see any spool file shown in this folder. Why? Where are the files saved?

Please help!

Thanks in advance,

Wei