Some time ago I thought of ways to optimize my Linux Servers network performanceand I googled around I found few interesting websites which give me the idea of some of the basic sysctl variables used for optimizing the GNU/Linux Network stack. Here are the variables themselves and some good example:
values.net.ipv4.ip_forward = 0 ( Turn off IP Forwarding )
net.ipv4.conf.default.rp_filter = 1
( Control Source route verification )
net.ipv4.conf.default.accept_redirects = 0
( Disable ICMP redirects )
net.ipv4.conf.all.accept_redirects = 0 ( same as above )
net.ipv4.conf.default.accept_source_route = 0
( Disable IP source routing )
net.ipv4.conf.all.accept_source_route = 0
( - || - )net.ipv4.tcp_fin_timeout = 40
( Decrease FIN timeout ) - Useful on busy/high load
serversnet.ipv4.tcp_keepalive_time = 4000 ( keepalive tcp timeout )
net.core.rmem_default = 786426 - Receive memory stack size ( a good idea to increase it if your server receives big files )
net.ipv4.tcp_rmem = "4096 87380 4194304"
net.core.wmem_default = 8388608 ( Reserved Memory per connection )
net.core.wmem_max = 8388608
net.core.optmem_max = 40960
( maximum amount of option memory buffers )
# like a homework investigate by yourself what the variables below stand for 
net.ipv4.tcp_max_tw_buckets = 360000
net.ipv4.tcp_reordering = 5
net.core.hot_list_length = 256
net.core.netdev_max_backlog = 1024
The above sysctl.conf is natively created to run on Debian and on other distributions like CentOS, Fedora Slackware some values might either require slight modifications.
Hope this helps and gives you some idea of how network optimization in Linux is usually done. Happy tweakening !
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