[ALUG] Re: Re: Re: TCP Problem *NOT* routing (was: Wierd routing/DNS problem)

[cl at isbd.net]

On Fri, Oct 06, 2006 at 09:40:09AM +0100, Brett Parker wrote:
> On Fri, Oct 06, 2006 at 09:33:06AM +0100, cl at isbd.net wrote:
> > On Fri, Oct 06, 2006 at 09:10:33AM +0100, Brett Parker wrote:
> > > On Fri, Oct 06, 2006 at 08:46:40AM +0100, cl at isbd.net wrote:
> > > > Do ping and traceroute use UDP?  If so it would seem that UDP is
> > > > working OK but that TCP isn't.
> > > 
> > > Ping is ICMP, traceroute is UDP, grab tcptraceroute... if that doesn't
> > > work then you've got a TCP problem, this is *not* routing, though, as
> > > ICMP and UDP can traverse, this limits it to a firewall, and I'd assume
> > > that it's your gateway device.
> > > 
> > The gateway is a router, already in use by two or three other systems
> > on the network with no problems.  That was my first thought in fact so
> > I checked that the router firewall setup was the same for the new
> > Linux box as for the other systems - it is.
> 
> OK - alarm bells just went off in my head... just a simple, really easy
> question here... is this a 2.6.17 kernel? If so, can you try the
> following:
>         echo 0 > /proc/sys/net/ipv4/tcp_window_scaling
> 
It's a 2.6.18 kernel (rc5 I think), but the above *does* fix the
problem - what arcane art is that?!   :-)

Brilliant, thanks.

> If your networking then works, I know what the problem is... if not,
> then there's something else at play here ;)
> 
I'm expecting this sort of problem really, I'm pushing the edge of
drivers available in Linux which is why I'm using a 2.6.18 kernel, the
SuSE 10.2 alpha (it'll be beta very soon I think) was one of the few
that has the drivers I want in it.

-- 
Chris Green (chris at halon.org.uk)