[plug] Smb Network Probs. MTU???

[Denis Brown]

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?

> 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?

> 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?

> The workstation is Knoppix 3.2 (C'T)
Any chance of trying with other than Knoppix (like a genuine Debian, for
instance?)   Yes, I know Knoppix *is* Debian under the hood, but they
might have done something interesting with smb.

> 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!

> This slow down also occurs using smbclient to copy files. In a normal
> smbmount|smbclient session I can cd to the directory and then i can
> possibly copy a few bytes before traffic halts. Looking at the output of
> ifconfig and observing the network graph in gnome the packets get further
> and further apart and ifconfig logs an error each time a line shows on the
> graph (showing activity)
>
Starting to sound to me like a hardware issue -- noise on the cable?
Faulty switch/hub/whatever?   Faulty NIC?   But then you say NFS is fine.
What version of SaMBa?   Or is part of this smb connectivity, kernel smb?

You're not using encryption for the smb are you?   I've had interesting
times when getting Windows and Linux to talk using scp and sftp... traffic
flows like treacle on a cold day.   Lin-Lin no worries.

HTH,
Denis