[X2go-dev] High Performance SSH/SCP - HPN-SSH

Erik Auerswald auerswald at fg-networking.de
Mon Jun 28 14:28:56 CEST 2010

Hello John,

On Mon, Jun 28, 2010 at 07:47:47AM -0400, John A. Sullivan III wrote:
> On Mon, 2010-06-28 at 09:30 +0200, Erik Auerswald wrote:
> > On Mon, Jun 28, 2010 at 06:55:56AM +0000, cougarmaster wrote:
> > >    Was reading about how to increase SSH performance and I came across this.
> > > [...]
> > > Also in there is a link to tuning network performance too just wanted
> > > to see if it would be of any help.
> > 
> > This is the standard network performance tuning found everywhere. This is
> > interesting for a saturated server, but will not solve any fundamental
> > speed issues.
> >
> I have been wondering if it will help with resilience.  We are having
> problems where, if the Internet connection starts dropping packets,
> recovery of the X2Go client is much slower than recovery of other
> applications such as web browsing.

Web browsing will start new TCP connections (not for every fetched URL
as back in the day, but still), while SSH uses just one connection. Thus
you might have the combination of TCP slow start with several competing
TCP connections (web browsing, file sharing, ...). As long as data
is available to send (e.g. a screen update of X2Go), TCP will try to
increase the send window, which might result in packet loss and slow
the stream down again.

You could try with a different congestion control algorithm for the ssh
session or with quality of service settings (end-to-end or at least at the
choke point, which might be the client side internet router).

>  We have tried playing with
> ClientAliveInterval and ClientAliveCountMax but that has not helped.

This would only help to keep the session alive, but not to speed up

Dipl.-Inform. Erik Auerswald                http://www.fg-networking.de/
auerswald at fg-networking.de Tel: +49-631-4149988-0 Fax: +49-631-4149988-9

Gesellschaft für Fundamental Generic Networking mbH
Geschäftsführung: Volker Bauer, Jörg Mayer
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