Re: ssh communication issue

On Fri, Jan 06, 2006 at 05:05:29PM -0500, Larry Irwin wrote:
> -Hopefully this is the right list-
> Our ssh connections work fine on all our servers when we connect via 
> the -local- network.
> But, when we ssh from the -internet-, there are long pauses where i/o is 
> not displayed/echoed to the screen on our Debian servers.
> We experience 10 to 30 second pauses after a screen or 2 of display on 
> Debian Etch kernel 2.6.12, SSH-2.0-OpenSSH_4.2p1 Debian-5.
> We have same issue, with slightly shorter pauses, on a Debian Sarge kernel 
> 2.4.18, OpenSSH_3.4p1 Debian 1:3.4p1-1.woody.3.
> We do not experience the problem on a SCO OS5 3.2v5.0.5 kernel, 
> OpenSSH_2.2.0p1
> Also, if we ssh to SCO first, then locally ssh to Debian, the pauses do not 
> occur...
> So it definitely has nothing to do with the network or infrastructure or 
> the load on any server, etc.
> It is something to do with either Debian or OpenSSH and only is triggered 
> when the IP source IP is outside the LAN.
> Does anyone know what might me contributing to the screen IO issue?

It's possibly an MTU issue which comes good when Path MTU Discovery
kicks in.  Read http://www.snailbook.com/faq/mtu-mismatch.auto.html and
try setting the MTU of the problem machine to 576 to see if the problem
goes away.

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.