Tuning operating systems and network settings

Network tuning can reduce Transmission Control Protocol (TCP) stack delay by changing connection settings and can improve throughput by changing TCP buffers.

Operating systems

A Windows system needs the least tuning while a Solaris system needs the most tuning. The following information pertains to each system specified, and might improve WebSphere® eXtreme Scale performance. You should tune according to your network and application load.

Windows

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\
Tcpip\Parameters
MaxFreeTcbs = dword:00011940
MaxHashTableSize = dword:00010000
MaxUserPort = dword:0000fffe
TcpTimedWaitDelay = dword:0000001e

Solaris

ndd -set /dev/tcp tcp_time_wait_interval 60000
fndd -set /dev/tcp tcp_keepalive_interval 15000
ndd -set /dev/tcp tcp_fin_wait_2_flush_interval 67500
ndd -set /dev/tcp tcp_conn_req_max_q 16384
ndd -set /dev/tcp tcp_conn_req_max_q0 16384
ndd -set /dev/tcp tcp_xmit_hiwat 400000
ndd -set /dev/tcp tcp_recv_hiwat 400000
ndd -set /dev/tcp tcp_cwnd_max 2097152
ndd -set /dev/tcp tcp_ip_abort_interval 20000
ndd -set /dev/tcp tcp_rexmit_interval_initial 4000
ndd -set /dev/tcp tcp_rexmit_interval_max 10000
ndd -set /dev/tcp tcp_rexmit_interval_min 3000
ndd -set /dev/tcp tcp_max_buf 4194304

AIX®

/usr/sbin/no -o tcp_sendspace=65536
/usr/sbin/no -o tcp_recvspace=65536
/usr/sbin/no -o udp_sendspace=65536
/usr/sbin/no -o udp_recvspace=65536
/usr/sbin/no -o somaxconn=10000
/usr/sbin/no -o tcp_nodelayack=1
/usr/sbin/no –o tcp_keepinit=40
/usr/sbin/no –o tcp_keepintvl=10

LINUX

sysctl -w net.ipv4.tcp_timestamps=0 
sysctl -w net.ipv4.tcp_tw_reuse=1 
sysctl -w net.ipv4.tcp_tw_recycle=1 
sysctl -w net.ipv4.tcp_fin_timeout=30 
sysctl -w net.ipv4.tcp_keepalive_time=1800 
sysctl -w net.ipv4.tcp_rmem="4096 87380 8388608" 
sysctl -w net.ipv4.tcp_wmem="4096 87380 8388608" 
sysctl -w net.ipv4.tcp_max_syn_backlog=4096 

HP-UX

ndd -set /dev/tcp tcp_ip_abort_cinterval 20000