SAMBA digest 1775

[Stephen L Arnold]

When the world was young, Adam Snodgrass carved some runes like 
this:

> Date: Mon, 10 Aug 1998 19:06:07 -0400
> Subject: Failure to execute programs from a mapped drive letter on a samba
 
> I have a strange situation.  I have a Linux machine running samba
> 1.9.18p8, serving a mix of NT Workstation 4.0 and Windows 95 clients.  In
> general, things have worked flawlessly, with one exception: none of the
> clients are able to execute programs stored on these shares.  Full reading
> and writing to the shares is possible; and even though I cannot see how it
> would be relevant, the execute bits are set to all files.  I can provide
> needed portions of my smb.conf file as needed.  Any suggestions or
> comments are most welcome.

It may have something to do with your TCP/IP settings on the client 
machines (or maybe not :-), specifically RWIN.  I don't have any NT 
experience myself, but my win95 clients were barfing (both browsing 
and launching even simple apps) at first, until I played with some 
of the client settings.  In the samba docs (Speed.txt, tuning 
stuff) they talk about "slow" client problems relating to the 
client settings for MTU, MSS, RWIN, etc.  At first I didn't think 
it related to my browsing problem (but I guess no performance at 
all could be considered a performance problem, if you stretch it) 
but it turned out that my clients (all clients have modems as our 
only access to the outside world right now) which had been tweaked 
for good DUN performance were not working with the samba stuff.

By good DUN performance, I mean the TCP/IP settings had been 
added/set in the registry.  Normally, win95 has no settings except 
MTU=1500 (a default buried somewhere in the code) which is usually 
okay for a LAN, however, it sucks for dialup stuff.  If you want to 
tweak your DUN settings, you need to add all the relevant 
keys/values to that disaster-waiting-to-happen (otherwise known as 
the windows registry).  This is easily done, either by hand (if you 
know where & what to do) or with a number of utilities (a good free 
one is MTUSpeed):

http://www.mjs.u-net.com/mtuspeed.htm

and the settings, etc, are described at:

http://dspace.dial.pipex.com/mreeves/tips.htm

To make a long story even longer, you need to check whether the 
RWIN value is set in the registry, and then try adjusting (either 
up or down).  RWIN=3072 appears to be the threshold value 
(according to the slow client stuff in the samba docs).  In my 
case, the default settings were fine for DUN performance, but I had 
to bump up RWIN to get samba working.  Original settings:

MaxMTU=576
MSS=536 (MTU-40 bytes)
RWIN=4xMSS=2144

New samba-friendly settings:

RWIN=8xMSS=4288

Now, not only does browsing work fine, but simple win32 apps 
installed on the share work fine too.  I can't help you with more 
bloated apps like M$ Orifice (noun: a mouth or vent opening into 
which you toss time and dollars) but there are some tips in the 
samba docs.

According to the slow client stuff mentioned in the docs, some 
people had to lower RWIN below 3072 for good performance (while I 
had to raise it above that value).  It may be somewhat 
hardware/speed dependent; I have fast clients (PII-266s) talking to 
a slow server (486-100) so your mileage may vary.

Let me know if this helps at all.

Regards, Steve Arnold


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Stephen L. Arnold                               Systems Engineer
ENSCO Inc.                        email:  arnold.steve at ensco.com
P.O. Box 5488                         www:  http://www.ensco.com
Vandenberg AFB, CA  93437             voice: 805.734.8232 x68838
                                               fax: 805.734.4779
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