sysctl.conf

# Configuration file for runtime kernel parameters.
# See sysctl.conf(5) for more information.

# Protection from SYN flood attack.
net.ipv4.tcp_syncookies = 1

# See evil packets in your logs.
#net.ipv4.conf.all.log_martians = 1

# Disable packet forwarding.
net.ipv4.ip_forward = 0
net.ipv6.conf.all.forwarding = 0

# Tweak those values to alter disk syncing and swap behavior.
#vm.vfs_cache_pressure = 100
#vm.laptop_mode = 0
#vm.swappiness = 60

# Tweak how the flow of kernel messages is throttled.
#kernel.printk_ratelimit_burst = 10
#kernel.printk_ratelimit = 5

# --------------------------------------------------------------------
# The following allow the server to handle lots of connection requests
# --------------------------------------------------------------------

# Increase number of incoming connections that can queue up
# before dropping
net.core.somaxconn = 5000

# Handle SYN floods
net.ipv4.tcp_max_syn_backlog = 1280

# Increase the length of the network device input queue
net.core.netdev_max_backlog = 5000

# Increase system file descriptor limit. Generally, set this to 64 * R, where
# R is the amount of RAM in MB your box has (minus a buffer?)
# (Per-process limit is set in /etc/security/limits.conf)
fs.file-max = 65536

# Widen the port range used for outgoing connections
net.ipv4.ip_local_port_range = 10152 65535 

# --------------------------------------------------------------------
# The following allow the server to handle lots of connection churn
# --------------------------------------------------------------------

# Disconnect dead TCP connections after 1 minute
net.ipv4.tcp_keepalive_time = 60

# Wait a maximum of 5 * 2 = 10 seconds in the TIME_WAIT state after a FIN, to handle
# any remaining packets in the network. 
net.ipv4.netfilter.ip_conntrack_tcp_timeout_time_wait = 5

# Timeout broken connections faster (amount of time to wait for FIN)
net.ipv4.tcp_fin_timeout = 60

# Let the networking stack reuse TIME_WAIT connections when it thinks it's safe to do so
# net.ipv4.tcp_tw_reuse = 1

# Determines the wait time between isAlive interval probes (reduce from 75 sec to 15)
net.ipv4.tcp_keepalive_intvl = 15

# Determines the number of probes before timing out (reduce from 9 sec to 5 sec)
net.ipv4.tcp_keepalive_probes = 5

# -------------------------------------------------------------