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Message-ID: <20060504130538.GA16590@openwall.com>
Date: Thu, 4 May 2006 17:05:38 +0400
From: Solar Designer <solar@...nwall.com>
To: owl-users@...ts.openwall.com
Subject: Re: TCP-Tuning
On Thu, May 04, 2006 at 01:07:18PM +0200, Bernhard Fischer wrote:
> - transfering 10MB of data within 10 seconds
>
> so far, so good!
>
> 2. scenario: gateway
> - two lan-interfaces (WAN: 10Mbit, LAN: 100Mbit)
> - transfering 10MB of data through the gateway within 122 seconds ?!?
What you describe sounds like a problem with path MTU discovery, perhaps
related to your ADSL modem (is one involved?) or your ISP.
The documentation for rp-pppoe suggests setting CLAMPMSS=1412 in
pppoe.conf - so just do that if you're using this package. Otherwise,
you can try adding:
[0:0] -A FORWARD -p tcp --syn -j TCPMSS --set-mss 1412
to /etc/sysconfig/iptables on the gateway. Alternatively, you can try
reducing the interface MTU on all hosts in your LAN to 1452.
This is kind of "TCP anti-tuning" - these settings are not optimal - but
they should work around the problem - if it is in fact MTU-related.
> How do i have to configure both lan-interfaces for best throughput?
That's not what you need. What you have is not just suboptimal
throughput. Things just aren't working right.
> When i look at the traffic-statistiks, there is a gap of 200ms silence
> followed by 300ms transmission. Why?
I've provided a guess above. If it doesn't help, you'll need to post
excerpts of tcpdump output which demonstrate the periods of silence.
Hope this helps and does not annoy other owl-users too much - although
it's not specific to Owl...
--
Alexander Peslyak <solar at openwall.com>
GPG key ID: B35D3598 fp: 6429 0D7E F130 C13E C929 6447 73C3 A290 B35D 3598
http://www.openwall.com - bringing security into open computing environments
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