Novell eDirectory 8.8 Troubleshooting Guide - NetIQ

These parameters are available in /proc/sys/net/ipv4/ directory.
• tcp_keepalive_time: Determines the frequency of sending the TCP keepalive packets to keep a
connection alive if it is currently unused. This value is used only when keepalive is enabled.
The tcp_keepalive_time takes an integer value in seconds. The default value is 7200 seconds or
2 hours. This holds good for most of the hosts and does not require many network resources. If
you set this value to low, it engages your network resources with unnecessary traffic.
• tcp_keepalive_probes: Determines the frequency of sending TCP keepalive probes before
deciding a broken connection.
The tcp_keepalive_probes takes an integer value, recommended less than 50 depending on
your tcp_keepalive_time and the tcp_keepalive_interval values. The default is to set to 9 probes
before informing the application of the broken connection.
• tcp_keepalive_intvl: Determines the duration for a reply for each keepalive probe. This value
is important to calculate the time before your connection has a keepalive death.
The tcp_keepalive_intvl takes an integer value, the default is 75 seconds. So, 9 probes with 75
seconds each will take approximately 11 minutes. The default values of the
tcp_keepalive_probes and tcp_keepalive_intvl variables can be used to evaluate the default
time before the connection is timed out because of keepalive.
novdocx (en) 22 June 2009
Modify these three parameters in a way that the change does not generate a lot of extra network
traffic and still solves the problem. A sample modification could be as follows (a 3-minute detection
time):
• tcp_keepalive_time set -120
• tcp_keepalive_probes - 3
• tcp_keepalive_intvl - 20
NOTE: Be careful with the parameter settings and avoid setting the already valid connections.
The settings take effect immediately after the files are modified. You need not restart any services.
However, the settings are valid for the current session only. Once the server is re-booted, the settings
revert to the default settings.
To make the setting permanent (even after a reboot), do the following:
Add the following entries in /etc/sysctl.conf.
• net.ipv4.tcp_keepalive_time=120
• net.ipv4.tcp_keepalive_probes=3
• net.ipv4.tcp_keepalive_intvl=20
We recommend these settings only if all the clients and servers are connected through LAN.
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