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

[Richard Sharpe]

On Mon, 3 Nov 2003, Jeremy Allison wrote:

> 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.
> 
> This is one of those numbers that W2K uses that seems
> to cause their redirector to do different things if
> it's changed. I can't get to my HP mail right now
> but hopefully Don will chime up with the background.

OK, I will try to do more experimentation today. I tried with W2K SP4 last 
night on a 100Mbps link, and it behaved correctly, AFAICS, with max xmit 
set to 65535. However, I am willing to believe that MS have done something 
silly with SP5 or 6.

Regards
-----
Richard Sharpe, rsharpe[at]ns.aus.com, rsharpe[at]samba.org, 
sharpe[at]ethereal.com, http://www.richardsharpe.com