samba - Oct 2001 - Collisions

We're using samba across a 10MBit ethernet and seem to get collisions on the
hub when reading files, no matter how quiet the traffic.  I can only think
that the smbd is beginning its reply before the request is fully finished.
Anyone know whether this is the case and whther I can tune anything to stop
it happening?

The collisions are probably caused by the client sending ACKs to confirm
receipt of data.  Collisions are a normal part of Ethernet communication, I
wouldn't worry about it unless they are very severe.  

A solution would be to use a switch rather than a hub.  A switch will allow
two-way (Full-Duplex) communication between your server and client,
eliminating the collision problem.

Ernie

-----Original Message-----
From: Steve Carter [mailto:Steve.Carter@tradepartners.com]
Sent: Monday, October 01, 2001 10:17 AM
To: Samba List (E-mail)
Subject: Collisions


We're using samba across a 10MBit ethernet and seem to get collisions on the
hub when reading files, no matter how quiet the traffic.  I can only think
that the smbd is beginning its reply before the request is fully finished.
Anyone know whether this is the case and whther I can tune anything to stop
it happening?

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I should have been more specific.  My intent was only to suggest to Steve
that some collisions are normal and not a significant cause for alarm. If
the situation is causing network slowdowns, then he may need to begin a more
serious investigation of the problem.

Client ACKs are a product of the 802.3 Ethernet protocol spec and are
implemented in the protocol stack.  In Ethernet communication, the client
will send an acknowledgement (ACK) for each window of data received.  This
is how the server knows whether or not to retransmit data due to an error or
loss.  As session time increases the transmission window should lengthen to
an appropriate degree, reducing the number of ACKs and the subsequent
collision rate.   

You are absolutely correct in saying physical layer issues can and often do
cause an excessive level of collisions.  Verifying the systems are running
half-duplex is also a very good idea.  Just keep in mind that Layer 1 issues
are not the only cause for network collisions.

A good example of this (Quick Search with TechNet) is 
http://support.microsoft.com/support/kb/articles/q169/7/89.asp

I appreciate the response and hope anyone with additional input steps
forward.

Thanks,
Ernie



-----Original Message-----
From: Peter Hicks [mailto:pwh@poggs.co.uk]
Sent: Monday, October 01, 2001 10:58 AM
To: Correale, Ernest
Cc: 'Steve Carter'; Samba List (E-mail); cc@poggs.co.uk
Subject: RE: Collisions


Ernest,

The underlying cause of Ethernet collisions is not the application, it is
the
physical network.

I agree, move to a switched environment at full duplex, but also check your
cables and that all clients on a hub are working at half duplex.


Peter.


On Mon, 1 Oct 2001, Correale, Ernest wrote:
> The collisions are probably caused by the client sending ACKs to confirm
> receipt of data.  Collisions are a normal part of Ethernet communication,
I
> wouldn't worry about it unless they are very severe.
>
> A solution would be to use a switch rather than a hub.  A switch will
allow
> two-way (Full-Duplex) communication between your server and client,
> eliminating the collision problem.
>
> Ernie
>
> -----Original Message-----
> From: Steve Carter [mailto:Steve.Carter@tradepartners.com]
> Sent: Monday, October 01, 2001 10:17 AM
> To: Samba List (E-mail)
> Subject: Collisions
>
>
> We're using samba across a 10MBit ethernet and seem to get collisions
on
the
> hub when reading files, no matter how quiet the traffic.  I can only think
> that the smbd is beginning its reply before the request is fully finished.
> Anyone know whether this is the case and whther I can tune anything to
stop
> it happening?
>
> --
> To unsubscribe from this list go to the following URL and read the
> instructions:  http://lists.samba.org/mailman/listinfo/samba
>
> --
> To unsubscribe from this list go to the following URL and read the
> instructions:  http://lists.samba.org/mailman/listinfo/samba
>

Hi,

I'm very new to network administration and especially Samba
configuration, and I have a very simple question. I just inherited the
Net Admin responsibility for our small startup company and we have only
10 machines on the network. All windows except the server and my laptop
which both run Linux.

I installed the latest Samba the server from the source files, compiled,
and everything went perfectly well that I was impressed. I wrote the
very simple smb.conf as suggested and when I typed \\Maggie on a Windows
workstation DOS prompt, the share appeared immediately like magic.

So I tested by transferring a lot of files, big and small, just to make
sure that it worked. And it worked. But during the transfer process, I
noticed that on my hub, the "Collision" LED was flashing very fast and
constantly. All my files transferred fast, no problem at all, and my
question might be stupid especially that I don't have a problem. Is it
normal that the collision LED flashes during files transfer?

Thanks!

Jean-Francois Pelletier