TCP memory is calculated automatically based on system memory; you can find the actual values by typing the following commands:
root@bright-OptiPlex-980:/proc/sys/net/ipv4# cat tcp_mem
193518 258025 387036
The default and maximum amount for the receive socket memory:
root@bright-OptiPlex-980:/proc/sys/net/core# cat rmem_default
126976
root@bright-OptiPlex-980:/proc/sys/net/core# cat rmem_max
131071
The default and maximum amount for the send socket memory:
root@bright-OptiPlex-980:/proc/sys/net/core# cat wmem_default
126976
root@bright-OptiPlex-980:/proc/sys/net/core# cat wmem_max
131071
The maximum amount of option memory buffers:
root@bright-OptiPlex-980:/proc/sys/net/core# cat optmem_max
20480
Setting
echo 'net.core.wmem_max=12582912' >> /etc/sysctl.conf
echo 'net.core.rmem_max=12582912' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_rmem= 10240 87380 12582912' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_wmem= 10240 87380 12582912' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_window_scaling = 1' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_timestamps = 1' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_sack = 1' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_no_metrics_save = 1' >> /etc/sysctl.conf
echo 'net.core.netdev_max_backlog = 5000' >> /etc/sysctl.conf
sysctl -p
Setting
echo 'net.core.wmem_max=12582912' >> /etc/sysctl.conf
echo 'net.core.rmem_max=12582912' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_rmem= 10240 87380 12582912' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_wmem= 10240 87380 12582912' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_window_scaling = 1' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_timestamps = 1' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_sack = 1' >> /etc/sysctl.conf
echo 'net.ipv4.tcp_no_metrics_save = 1' >> /etc/sysctl.conf
echo 'net.core.netdev_max_backlog = 5000' >> /etc/sysctl.conf
sysctl -p