max xmit default to 0x4104 (16644). Why ...

Christopher R. Hertel crh at
Mon Nov 3 04:03:07 GMT 2003


I don't have a direct answer but I do have some interesting notes.  Read 
through this section:

There's an E'mail from Conrad in there.  He also found some very odd
limits when talking to different Windows systems.

The number you gave does more than just ring a bell.  In my book I have it
as 16611 (0x40E3) for W2K SP6.  Note, though, that my number is the echo 
size (if I recall correctly) not the total xmit size.  The difference is 
33 bytes (which sounds about right).  Anyway, above that size the W2K 
system would close the TCP connection.  Ouch.

My memory is vague on this one, but I tested against W2K SP6 using
SMB_COM_ECHO.  It's a very easy test to set up (a few lines of code).

Chris -)-----

On Sun, Nov 02, 2003 at 08:28:44PM -0800, Richard Sharpe wrote:
> Hi,
> In tracking down a benchmarking problem, I discovered the following:
>         /* Was 65535 (0xFFFF). 0x4101 matches W2K and causes major speed 
> 	   improvements... */
>         /* Discovered by 2 days of pain by Don McCall @ HP :-). */
>         Globals.max_xmit = 0x4104;
> This causes me major problems and I was wondering why the previous value 
> (of 65535) caused problems with Win2K.
> I have not yet tested with Win2K and my testing has been confined to using 
> cifs_bm, but it also seems unlikely to be a problem on the surface. This 
> is the setting of the max amount data that Samba is capable of writing in 
> one go. If Windows does not like it, it is free to use a smaller size in 
> read(&X) requests if it likes to.
> I wonder if anyone (Don McCall?) has a capture of this behavior so we can 
> see what exactly is going on?
> Regards
> -----
> Richard Sharpe, rsharpe[at], rsharpe[at], 
> sharpe[at],

"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team --     -)-----   Christopher R. Hertel
jCIFS Team --   -)-----   ubiqx development, uninq.
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