Knowledge base - Posts tagged with: networking

Network Stack TCP tuning

These changes should go into /etc/sysctl.conf

The default maximum for buffers allocated to TCP are totally insane. While the most optimal numbers need to be calculated for specific environments the following settings are a good start:

net.core.rmem_max = 16777216
net.core.wmem_max = 16777216

Increase Linux auto-tuning TCP buffer limits:

net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216

Use robust congestion control:

net.ipv4.tcp_congestion_control=htcp

Don't cache ssthresh from previous connection - well, duh:

net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1

Pretend we always have a gigabit ethernet, even if we only have fast ethernet:

net.core.netdev_max_backlog = 2500


Interface Transmit Queue Size

The default setting is idiotic. Change it to something sane:

Routing Table Cleanup

While 169.254.0.0/16 route shows up only on machine with multiple NICs it has no place on the systems at all. Get rid of the annoying Zero Configuartion crap by adding the following lines to /etc/sysconf/network:

NOZEROCONF=yes