Speaking of MTU mismatches, don't forget that if you're using a PPPoE DSL line to adjust your MTU.
Geoff
Sent from my BlackBerry wireless handheld.
-----Original Message----- From: "Ross S. W. Walker" rwalker@medallion.com
Date: Mon, 10 Sep 2007 16:35:59 To:"CentOS mailing list" centos@centos.org Subject: RE: [CentOS] Performance of CentOS as a NAT gateway
Bart Schaefer wrote:
On 9/9/07, Barry Brimer lists@brimer.org wrote:
Maybe it is time for some kernel networking tuning.
After doing a bit of research:
http://www.acc.umu.se/~maswan/linux-netperf.txt http://wwwx.cs.unc.edu/~sparkst/howto/network_tuning.php http://proj.sunet.se/E2E/tcptune.html http://www.linuxguruz.com/iptables/howto/2.4routing-13.html http://www-didc.lbl.gov/TCP-tuning/linux.html
I ended up with this:
net.core.rmem_default = 873800 net.core.wmem_default = 655360 net.core.rmem_max = 8738000 net.core.wmem_max = 6553600 net.ipv4.tcp_rmem = 8192 873800 8738000 net.ipv4.tcp_wmem = 4096 655360 6553600 net.ipv4.tcp_mem = 195584 873800 8738000
(The first number in tcp_mem is the original default.)
Plus:
ifconfig eth0 txqueuelen 1000 ifconfig eth1 txqueuelen 1000
Unfortunately so far this doesn't seem to have made any difference. We've had a load peak going since early this morning and the traffic looks exactly like it did last week.
The only way your going to know for absolute sure where the bottleneck exists is to do a wireshark/tcpdump trace simultaneously on both sides.
Then with that information you will know where the bottleneck is and armed with that you can start exploring why there is a bottleneck there.
Off the top of my head, there could be a IP MTU mismatch somewhere and with ICMP disabled this would cause a blackhole for some full packet traffic.
-Ross
______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.
_______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos