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Re: [LARTC] Conntrack table full and Heavy p2p loaded traffic manager ..

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Subject: Re: [LARTC] Conntrack table full and Heavy p2p loaded traffic manager ...
From: Luciano Ruete <luciano@lugmen.org.ar>
Date: Sat, 24 Feb 2007 22:37:33 -0300
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On Friday 23 February 2007 16:28, Sébastien CRAMATTE wrote:
> Hello
>
> I've setuped a bridge with l7-filter and ipp2p.  We have every day  + or
> -  between 10Mbits and 30 Mbits P2P traffic from + or - 450 customers.
> When traffic  increase. I've got this kind of error message :
>
> Feb 23 14:26:19 gestor1 kernel: printk: 38 messages suppressed.
> Feb 23 14:26:19 gestor1 kernel: ip_conntrack: table full, dropping packet.
>
> The server is  celeron pentium 4 based 3Ghz + 512Mb ram
> Does anyone could suggest me what are the best value for
>
> net.ipv4.netfilter.ip_conntrack_max
> net.ipv4.netfilter.ip_conntrack_tcp_timeout_established

leave the timeouts as is, and focus on the conntrack_max,
lnstat command is your friend, will help to find the magic numbers:

lnstat -f ip_conntrack -i 1 -c 1 

this will tell you the number of entries used in real time, so you can put a 
very large value in ip_conntrack_max and monitor with lnstat and crontab like 
this:
*/5 *    * * *    root  date >> /var/log/conntrack_watchdog.log; lnstat -f 
ip_conntrack -i 1 -c 1 >> /var/log/conntrack_watchdog.log

After a couple of days you are ready to put the perfect number for you 
personal enviroment.

Each conntrack entrie is about 350bytes from non-swappable kernel memory, so 
you can make your maths to know how much RAM is consumed.

> Might be I can tune other kernel value ?

yes, in large setups is recommended to change the conntrack hash table size:
modrobe ip_conntrack hashsize=xxx

to avoid to have a large ammount of entries in the same bucket, this can have 
performmance issues, you can check your acctual hash table size looking at 
dmesg.


-- 
Luciano
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