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Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!cwjcc!gatech!purdue!decwrl!decvax!eagle_snax!geoff
From: geoff@eagle_snax.UUCP ( R.H. coast near the top)
Newsgroups: comp.protocols.tcp-ip.ibmpc,comp.protocols.nfs
Subject: Re: public domain support for Sun NFS standard
Message-ID: <435@eagle_snax.UUCP>
Date: 19 Dec 88 14:58:21 GMT
References: <493*andchan@ccu.UManitoba.CA> <8812161645.AA10438@monk.proteon.com>
Reply-To: garnold@Sun.Com (Geoff Arnold @ Sun ECD - R.H. coast near the top)
Organization: Sun Microsystems - East Coast Division
Lines: 64

In article <8812161645.AA10438@monk.proteon.com> jas@proteon.com ("John A. Shriver") writes:
>The lack of a public domain PC NFS has very little to do with the
>issues of NFS/RPC/UDP/IP/...  It has to do with the fact that the
>interface to the MS-DOS redirector is essentially a highly-guarded
>trade secret of Microsoft, available only if you sign up as a
>MS-Networks OEM.  This is not cheap, last I knew you had to pay by the
>year.  There are people who have sucessfully reverse-engineered this
>interface (eg. Locus), but they consider it highly valuable
>information, and also sell it for a pretty penny.
>

Actually, there are two ways to implement a redirector under (on top of?)
DOS. [And no, I'm not giving away any valuable secrets: anybody with
a copy of IBM's PC Watch or a good debugger could figure this out in a
moment.] The first, employed by Locus and (by derivation) PC-NFS emulates
the DOS system call interface itself by intercepting int21 and a bunch of
additional hooks. A definition of this interface has been published in the
DOS Technical Reference and other sources; what makes the task hard (and 
why people guard their implementations jealously) is the fact that the
definition is incomplete (there are a couple of critical undocumented
calls) and the semantics are inadequately described (e.g. under what
circumstances does DOS zero out the rest of a buffer following an incomplete
read?).

The second way to build a redirector is to intercept the internal
int2f multiplex interface used by DOS itself. This is the interface
used by the Microsoft redirector for which they charge the big bucks:
it has been successfully reverse-engineered, but since the interface
is modified at major DOS releases any implementors will be kept busy
just staying up to date.

>I have no idea what would happen if someone did the reverse
>engineering and then put the results in the public domain.  Lawsuits?

I don't see why there should be any lawsuit. However, the level of effort is
such that a successful implementation would become a very valuable
asset, and the lure of profit, etc. etc. 

In addition to PC-NFS, I know of three ongoing efforts to develop PC
DOS NFS clients. One (Beame & Whiteside's BW-NFS) was discussed in this
newgroup a few months back. The others are still under wraps. As the
architect of PC-NFS, I wish them well, with just a touch of pity: after
shipping PC-NFS for two and a half years, we are still encountering
subtle nuances within DOS which we need to emulate. I know just how
busy - and frustrated - they're all going to be!

>Oh yes, it would not be hard to make a PC do NFS file service.

stan@lbl-csam.arpa (See-Mong Tan) has done a nice job in developing
a server at Lawrence Berkeley Laboratory, and as he mentioned in
<1485@helios.ee.lbl.gov> LBL and Sun are discussing its possible
distribution. 

>Unfortunately, a PC, it's BIOS, and DOS offer pretty abysmal file
>performance, so it would not be a good file server.  (Interrupts off
>during disk I/O does not help the NFS side of things.)

Absolutely - give me a Sun 4/280 with a couple of Super Eagles
any day :-)
-- 
Geoff Arnold, Sun Microsystems Inc.  +--------------------------------------+ 
PC Dist. Sys. Group (home of PC-NFS) |When you're fresh out of lawyers, you |
UUCP: {hplabs,decwrl...}!sun!garnold |don't know how good it's going to feel|
ARPA: garnold@sun.com                +--------------------------------------+