SMB Keep-alive.

Christopher R.Hertel crh at
Tue May 14 21:26:02 GMT 2002

On Wed, May 15, 2002 at 10:07:07AM +1000, Tim Potter wrote:
> On Tue, May 14, 2002 at 03:10:00PM -0500, Christopher R. Hertel wrote:
> > I have not seen SMB Keep-Alive used except in a few odd instances in
> > which it is used to trick Windows into behaving properly.
> > 
> > Does anyone know if SMB Keep-Alive is actually used in practice?
> Doesn't smbclient have to respond to keepalives or else the connection
> dies?

Ethereal (the version I'm using, at least--I have not had time to update
lately and it is a bit out of date) reports these packets as "NBSS
Continuation Messages" and does *not* break down the fields properly.  I
am running 0.8.17.

What I see in the traces is that the server (Samba, in this case) sends a
keep-alive message every 6 minutes, and the client responds with a TCP
ACK.  No NBT-level reply is generated... but that's what I expect, based
on my reading of the RFCs.  Since it's a TCP connection, the NBT
keep-alive just keeps the TPC session going.

I have seen Samba send the keep-alives, but I haven't *yet* seen Windows
do it.  I've got two Windows boxes set up right now, one with a share
mapped from the other.  I've got tcpdump going on a spare 486 in the
basement, and I'll look at the capture tomorrow.

Chris -)-----

Samba Team --     -)-----   Christopher R. Hertel
jCIFS Team --   -)-----   ubiqx development, uninq.
ubiqx Team --     -)-----   crh at
OnLineBook --    -)-----   crh at

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