TCP Tuning
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Linux Tunables

Raising Network Limits on Linux Systems for 2.1.100 or greater

Linux only allows you to use 15 bits of the TCP window field. This means that you
have to multiply everything by 2, or recompile the kernel without this limitation.

Tuning a Running System

There is no sysctl application for changing kernel values. You can change the
kernel values with an editor like VI.

Tuning the Default and Maximum Size

Edit the files listed below to change kernel values.
Table 4–4 AIX TCP Parameters (using no command)
Parameter Model Default
Value Recommended Value
rfc1323 /etc/rc.net 01
sb_max /etc/rc.net 65,536 1,31,072
tcp_mssdflt /etc/rc.net 512 1,024
ipqmaxlen /etc/rc.net 50 100
tcp_sendspace /etc/rc.net 16,384 65,536
tcp_recvspace /etc/rc.net 16,384 65,536
xmt_que_size /etc/rc.net 30 150
See Also: Tuning at Compile Time
Table 4–5 Linux TCP Parameters
Filename Details
/proc/sys/net/core/rmem_default Default Receive Window
/proc/sys/net/core/rmem_max Maximum Receive Window
/proc/sys/net/core/wmem_default Default Send Window
/proc/sys/net/core/wmem_max Maximum Send Window