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RE: SSH Tunneling and TCP_NODELAY


Well, more like "It works fine when ssh is not in the loop", but I have a
suspicion that it has to do with the OpenSSH port in Cygwin.  It is hard to
tell at this time...  It has something to do with port forwarding and TCP
buffering at the kernel level.

Brian

--- "lhall@pop.ma.ultranet.com" <lhall@pop.ma.ultranet.com> wrote:
> So this is a Cygwin issue and not a ssh issue (i.e. you're saying
> it works fine if the Cygwin ssh isn't in the loop)?
> 
> Larry
> 
> Original Message:
> -----------------
> From: Brian Genisio briangenisio@yahoo.com
> Date: Tue, 29 Oct 2002 14:06:37 -0800 (PST)
> To: cygwin@cygwin.com
> Subject: SSH Tunneling and TCP_NODELAY
> 
> 
> Hi all,
> 
> I am using SSH port forwarding on a linux sshd from the Cygwin ssh.  Both
> sides
> have version OpenSSH 3.4p1.  There is no problem with my tunneling, as I
> have
> been using many (about 10) port forwards (server and local) for quite some
> time
> now.
> 
> A new application has been introduced to my mix that uses the network to
> send
> control messages at about 30 times per second.  These messages are small
> (4-12
> bytes), but sent at a frequent rate.
> 
> If port forwarding is NOT used, the control stream is working well.  BUT,
> if I
> send the control string through the SSH tunnel, it gets sent as bursts...
> for
> example, the receiving application wukk get no data for 5 frames, and the
> 6th
> frame will get all 6 frames.
> 
> This makes for a jerky control of the software.  My control program has
> TCP_NODELAY set in it's ouput socket which is why it works properly.  I
> _thought_ that openssh starting at version 3.1 had TCP_NODELAY set on it's
> forwarded ports (my debug outputs tell me so).  None the less, the bursting
> (which I believe is a cacheing at some point) still happens.
> 
> My question:
> 
> Is there something about the Cygwin version of SSH where TCP_NODELAY doesnt
> work properly, or it is a stub function?  Can anyone think of a reason this
> is
> happening?
> 
> Thanks,
> Brian
> 
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