Re: 2.6.9 tcp problems

[Mark Watts]

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> Stephen Hemminger wrote:
> > On Mon, 29 Nov 2004 13:03:34 -0500
> >
> > kernel <kernel@xxxxxxxxxxxx> wrote:
> >> I've run into a problem with 2.6.(8.1,9) after installing a secondary
> >> firewall. When I try to pull data through the original firewall
> >> (mail, http, ssh), it stops after approx. 260k. Running ethereal
> >> tells me "A segment before the frame was lost" followed by a bunch
> >> of  "This is a TCP duplicate ack" when using ssh. All 2.4.x machines
> >> and windows clients work fine. I built 2.4.28 and it works fine from
> >> my machine. I also fiddled with tcp_ecn and that didn't fix it
> >> either. I don't have any problems communicating to "local" machines.
> >> I've attached the tcpdump output from an scp attempt. NIC is a 3Com
> >> Corporation 3c905B.
> >
> > What kind of firewall?  There are firewalls that are too stupid and don't
> > understand TCP window scaling.
>
> It's a fortigate 60.  We put our secure web servers behind a netscreen 5
> firewall which plugs into the fortigate and that's when the problems
> started.  I remember reading some stuff on lkm about recent tcp changes
> but I couldn't remember exactly what it was. Thanks for reminding me !
>
> Here is how it's layed out now
> secure_web_servers->netscreen->fortigate->rest_of_network
>

Not sure if this helps:

I have a pair of Dell PowerEdge 1750's (running Mandrake 9.2/2.4.22) plugged 
directly into a Netscreen 5GT and they do not exhibit this behaviour.

Network cards are bcm5700 series.

/proc/sys/net/ipv4/tcp_window_scaling is set to '1'

Mark.

- -- 
Mark Watts
Senior Systems Engineer
QinetiQ Trusted Information Management
Trusted Solutions and Services group
GPG Public Key ID: 455420ED

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