Re: Linux forwarding Win XP hosts VERY slowly

[Alistair Tonner <Alistair@nerdnet.ca>]

On April 30, 2005 01:41 pm, Dave Cinege wrote:
> I've built an advanced rotuign appliance, and I'm having 2 outstanding
> problems, that I'm being to think are related to the linux ip/netfilter
> stack, choking on XP traffic (possiblity XP-SP2) hosts that are on the LAN.
> I'm running 2.4.30 at the moment.
>
> The 2 problems I'm seeing:
>
> 1) Forwarded traffic (most notably web) is VERY slow with XP clients.
>
> Example: Saw this last 2 nights ago: Appliance has a linksys Wifi bridge
> attached to a NIC. Customer browses through the appliance to the Linksys
> config page. It moves like molasses. He browse to the local Zope hosted
> made page. Slow as hell. I unplug his machine, and plug my linux laptop
> into same switch port. Linksys and Zope pages load adn reload instantly.
> Plug his machine in....slow again.
>
> 2) Zope serves user interface pages for the appliance. Zope has been
> locking solid for no apparent reason, but only when and Windows host is
> attached. The trick is SOME windows machine don't seem to cause a problem.
> Example:
> I worked with a unit for 3 days using a customers XP desktop. Not a hiccup.
> My partner came in and attached to the network and starting connect to our
> appliance with his XP laptop. Within 15 minutes Zope was hung.
>

	I would strongly suspect the XP box has a b0rken TCP stack happening.  One 
thing that some windows systems will do is flat out ignore the TCP MTU/window 
size settings on the network, especially if you've a) set them up for modem 
dialup b) installed anything that is supposed to automatically improve your 
internet speed c) hard wired (EVER) the MTU settings.  I had a win2k box that 
had this sort of issue once, and even though it was at that time set to use 
default settings for MTU/max recieve window and the like, I had to completely 
uninstall the tcp stack, the network card driver, all modem bits etc and 
reinstall em from scratch to get it to behave normally.  For the record, 
Ethereal dumps of the communications CLEARLY show that the windows box is 
using bad MTU settings and bad TCP window sizes, if this is the case.

I *still* believe that there are settings left on that box (still in use these 
days) that cause issues periodically.  Cant wait to get it out of service 
later in May.

	Hmm ... Grant T has the same drift (darn ... mail filters are busy tonight -- 
must be lots of spam in this round ... took Grants mail 6 minutes to get into 
the box after yours....)

	Alistair Tonner

> I'm really lost. ANY ideas out there?