View source for TCP-Tuning

= TCP Performance =

This page describes how to enhance the performance of data transfers. It mainly focus on the optimization of the Linux kernel parameters.

== Kernel parameters ==

The following are important for TCP tuning:
* <code>net.ipv4.tcp_rmem</code>
* <code>net.ipv4.tcp_wmem</code>
* <code>net.core.rmem_default</code>
* <code>net.core.wmem_default</code>
* <code>net.core.rmem_max</code>
* <code>net.core.wmem_max</code>
* <code>net.ipv4.tcp_dsack</code>
* <code>net.ipv4.tcp_sack</code>
* <code>net.ipv4.tcp_timestamps</code>
* <code>net.core.netdev_max_backlog</code>

They can be modified with:
* Quattor ;
* YAIM ;
* Manually by modifying the <code>/etc/sysctl.conf</code> file.


== Recommended values ==

* <code>net.ipv4.tcp_rmem = 131072 1048576 2097152</code>
* <code>net.ipv4.tcp_wmem = 131072 1048576 2097152</code>
* <code>net.core.rmem_default = 1048576</code>
* <code>net.core.wmem_default = 1048576</code>
* <code>net.core.rmem_max = 2097152</code>
* <code>net.core.wmem_max = 2097152</code>
* <code>net.ipv4.tcp_dsack = 0</code>
* <code>net.ipv4.tcp_sack = 0</code>
* <code>net.ipv4.tcp_timestamps = 0</code>
* <code>net.core.netdev_max_backlog = 10000</code>


== External links ==
* http://fasterdata.es.net/
* http://monalisa.cern.ch/FDT/documentation_syssettings.html
* http://indico.cern.ch/contributionDisplay.py?sessionId=31&amp;contribId=55&amp;confId=61917
* http://www.psc.edu/networking/projects/tcptune/
* http://onlamp.com/pub/a/onlamp/2005/11/17/tcp_tuning.html
* http://en.wikipedia.org/wiki/TCP_tuning