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From: craig@mstr.hgc.edu (craig chaiken)
Newsgroups: comp.dcom.lans,comp.sys.ibm.pc.misc
Subject: MSDOS 3.x Network Redirection
Message-ID: <584@mstr.hgc.edu>
Date: 10 Oct 90 17:42:52 GMT
Sender: news@mstr.hgc.edu
Reply-To: craig@mstr.hgc.edu (craig chaiken)
Followup-To: comp.dcom.lans
Organization: The Hartford Graduate Center, Hartford CT.
Lines: 21

A recent PC Magazine article by Ray Duncan indicated that MSDOS 3.x
has the undocumented network hooks, or network redirection functions.
These function supposedly permit important LAN software products
by companies such as Novell, Microsoft, and IBM to transparently
access files on non-FAT based (non-DOS compatible) file systems.

*** Warning, this part gets technical ***

By tracing through the IBMDOS.COM, I was able to determine that all
disk related INT 21H calls hook into INT 2FH, passing 11H in AH and
00H through 26H in AL.  The values in AL seem to correspond to
disk related INT 21H calls.  The CPU registers used by INT 2FH are
very different from the ones used by INT 21H.  Without documentation,
using INT 2FH will require many hours of reverse engineering.

My question is, "Does anyone have any documentation describing how
parameters are passed to and from the network redirector, INT 2FH
function 11H?"  I will post any information that I receive.

Craig Chaiken (Author of M&T Books' "Blueprint of a LAN")
craig@mstr.hgc.edu