How can I change the TCP/IP tuning parameters?

All TCP/IP tuning parameters are located under the /proc/sys/net/ directory. For example, here is a list of the most important tuning parameters, along with a short description of their meaning:

1. /proc/sys/net/core/rmem_max – Maximum TCP Receive Window.
2. /proc/sys/net/core/wmem_max – Maximum TCP Send Window.
3. /proc/sys/net/ipv4/tcp_timestamps – Timestamp ( RFC 1323) add 12 bytes to the TCP headers.
4. /proc/sys/net/ipv4/tcp_sack – TCP selective acknowledgments.
5. /proc/sys/net/ipv4/tcp_window_scaling – support for large TCP Windows (RFC 1323). Needs to be set to 1 if the Max TCP Window is over 65535.
6. mem_default = Default Receive Window.
7. rmem_max = Maximum Receive Window.
8. wmem_default = Default Send Window.
9. wmem_max = Maximum Send Window.

Everything under /proc is volatile, so any changes made are lost after a reboot.

Applying TCP/IP Parameters at System Boot:

Place the following code in /etc/rc.local so that they get applied on the system while booting:

echo 256960 > /proc/sys/net/core/rmem_default

echo 256960 > /proc/sys/net/core/rmem_max

echo 256960 > /proc/sys/net/core/wmem_default

echo 256960 > /proc/sys/net/core/wmem_max



echo 0 > /proc/sys/net/ipv4/tcp_timestamps

echo 1 > /proc/sys/net/ipv4/tcp_sack

echo 1 > /proc/sys/net/ipv4/tcp_window_scaling

The TCP/IP parameters are self-explanatory. It is setting up the TCP Window to 256960, disabling timestamps (to avoid 12 byte
headers overhead), and enabling tcp window scaling and selective acknowledgments.

Change the values above as desired, depending on the internet connection and maximum bandwidth/latency.

Note :Above values can be used but are just a part of example.

Another method to reapply the values upon boot is to include the following in the /etc/sysctl.conf file.

net.core.rmem_default = 256960

net.core.rmem_max = 256960

net.core.wmem_default = 256960

net.core.wmem_max = 256960



net.ipv4.tcp_timestamps = 0

net.ipv4.tcp_sack =1

net.ipv4.tcp_window_scaling = 1

contributed by Kaustabh Chaudhari

Red Hat’s customer service and support teams receive technical support questions from users all over the world. Red Hat technicians add the questions and answers to Red Hat Knowledgebase on a daily basis. Access to Red Hat Knowledgebase is free. Every month, Red Hat Magazine offers a preview into the Red Hat Knowledgebase by highlighting some of the most recent entries.

This entry was posted by The editorial team on Thursday, January 25th, 2007 at 2:00 am and is filed under tips and tricks . You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

 

原文地址: http://magazine.redhat.com/2007/01/25/how-can-i-change-the-tcpip-tuning-parameters/