Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Thu, 4 May 2006 15:23:11 +0200 (CEST)
From: Bernhard Fischer <>
Subject: Re: TCP-Tuning

Am Do 04.05.2006 15:05 schrieb Solar Designer <>:

> 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:

I'm connected to an cisco-router with an E3 interface (10Mbit) to the
internet, so i would say it's not an MTU problem to the outgoing
interface (because I do have perfect bandwidth on the local machine, but
not if it's acting as gateway)

> [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.

all interfaces are using an MTU of 1500

additionaly i played with mii-diag and tried different settings on the
LAN-interface (10, 100, FD, HD) without meaningfull differences

> 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.

that's it.

> > 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...

it's realy not specific to Owl ... but I'm running out of help

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.