[plug] Smb Network Probs. MTU???

[Tim White]

At 09:19 08/06/2004 +0800, you wrote:
>On Mon, 7 Jun 2004, Tim White wrote:
> > When attempting to transfer files over smb the packets slow down to a halt
> > with the time between packets doubling each time.
> >
>Has this only just started happening or has it been a feature since
>day-one?

Yep

> > The MTU of eth0 is 1500
> > and when set to 100 smb finally works (as much as I can see.)
>An MTU of 100 is way small in my experience.   1500 sounds better.   Do
>you have any intermediate boxes (switch? router? another Lin/Win box?)
>between the two target machines for which slow-down occurs?

No in between boxes. Trying to browse the net with a MTU of 100 is terrible.

> > This slow down doesn't occur for Internet traffic only for smb. Both net
> > and smb traffic are from the windows gateway to my workstation. Last time
> > this was a problem it also effected FTP. NFS traffic between my debian
> > server and my workstation is fine.
> >
>Server = Debian woody
>Workstation = Knoppix 3.2
>therefore, any reason not to simply continue with NFS rather than use SMB?

To clarify.
Gateway = Windows 2k
Server = Deb
Workstation = Knoppix
The samba problems are between the gateway and workstation. All the 
Internet also comes through there.

> > If anybody knows a fix for this other than MTU then please tell me. Does a
> > lower MTU slow down other traffic? Also how can I set the MTU to be
> > permanently 100.
>Not sure you'd want to (set it low).   IIRC the MTU defines the packet
>size so if you're sending a huge volume of data, setting a small MTU value
>increases the overhead thanks to the higher proportion of packet headers.
>Gurus please correct this if the thinking is wrong!

I don't want to change it permanently to 100 but if there is a way to do it 
for samba then cool. I will look at updating to Samba 3 some time soon.
On a side note, I just copied from the Linux machine to the windows machine 
(Doing all operations from the windows machine) and a 10Mb file copied in a 
under a minute and 108Mb in 7 minutes with a continues flow of traffic. 
Trying to send a 10Mb file back from the windows machine resulted in the 
same problem. On the windows machine I got an error about the path being to 
deep even though the share was \\linmedia\hda4\ and i was copying to the 
root of the share. The file name is a valid name and under 8 chars. But 
when I look at the Linux box the file is there with the correct size, but 
invalid data. (There was very little traffic as well. Could this be samba 
preparing a place for the file on the hdd and then copying in the file as 
it receives it but failing and leaving a file that spans unknown data?)
Also none of the problems are present when I boot the workstation into 
Windows (XP or 2k.) Looking at a ssh session (spewing out /dev/urandom [1]) 
the traffic seems to be confined to smb.
Tim
[1] During this process apart from the title of putty changing constantly 
it appears to have opened winamp with the last music file loaded. Can putty 
do? Or is it windows interpretting ASCII codes like you could do in DOS to 
display fancy prompts?

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