#
# /etc/sysctl.conf - Configuration file for setting system variables
# See /etc/sysctl.d/ for additional system variables.
# See sysctl.conf (5) for information.
#

#kernel.domainname = example.com

# Uncomment the following to stop low-level messages on console
#kernel.printk = 3 4 1 3

##############################################################3
# Functions previously found in netbase
#

# Uncomment the next two lines to enable Spoof protection (reverse-path filter)
# Turn on Source Address Verification in all interfaces to
# prevent some spoofing attacks
#net.ipv4.conf.default.rp_filter=1
#net.ipv4.conf.all.rp_filter=1

# Uncomment the next line to enable TCP/IP SYN cookies
# See http://lwn.net/Articles/277146/
# Note: This may impact IPv6 TCP sessions too
#net.ipv4.tcp_syncookies=1

# Uncomment the next line to enable packet forwarding for IPv4
#net.ipv4.ip_forward=1

# Uncomment the next line to enable packet forwarding for IPv6
#  Enabling this option disables Stateless Address Autoconfiguration
#  based on Router Advertisements for this host
#net.ipv6.conf.all.forwarding=1


###################################################################
# Additional settings - these settings can improve the network
# security of the host and prevent against some network attacks
# including spoofing attacks and man in the middle attacks through
# redirection. Some network environments, however, require that these
# settings are disabled so review and enable them as needed.
#
# Do not accept ICMP redirects (prevent MITM attacks)
#net.ipv4.conf.all.accept_redirects = 0
#net.ipv6.conf.all.accept_redirects = 0
# _or_
# Accept ICMP redirects only for gateways listed in our default
# gateway list (enabled by default)
# net.ipv4.conf.all.secure_redirects = 1
#
# Do not send ICMP redirects (we are not a router)
#net.ipv4.conf.all.send_redirects = 0
#
# Do not accept IP source route packets (we are not a router)
#net.ipv4.conf.all.accept_source_route = 0
#net.ipv6.conf.all.accept_source_route = 0
#
# Log Martian Packets
#net.ipv4.conf.all.log_martians = 1
#

###################################################################
# Magic system request Key
# 0=disable, 1=enable all
# Debian kernels have this set to 0 (disable the key)
# See https://www.kernel.org/doc/Documentation/sysrq.txt
# for what other values do
#kernel.sysrq=1

###################################################################
# Protected links
#
# Protects against creating or following links under certain conditions
# Debian kernels have both set to 1 (restricted) 
# See https://www.kernel.org/doc/Documentation/sysctl/fs.txt
#fs.protected_hardlinks=0
#fs.protected_symlinks=0

###################################################################
# Improving performance
# Virtual memory
# Consensus is that setting vm.dirty_ratio to 10% of RAM is a sane value if RAM is say 1 GB (so 10% is 100 MB). But if the machine has much more RAM, say 16 GB (10% is 1.6 # GB), the percentage may be out of proportion as it becomes several seconds of writeback on spinning disks. A more sane value in this case may be 3 (3% of 16 GB is #approximately 491 MB).

vm.swappiness=10
vm.dirty_ratio=10
vm.dirty_background_ratio=5
vm.vfs_cache_pressure=50
vm.dirty_background_bytes=4194304
vm.dirty_bytes=4194304

# Networking
# Increasing the size of the receive queue.
net.core.netdev_max_backlog=100000
net.core.netdev_budget=50000
net.core.netdev_budget_usecs=5000
#
# Increase the maximum connections default 128
net.core.somaxconn=1024
#
# Increase the memory dedicated to the network interfaces
net.core.rmem_default=1048576
net.core.rmem_max=16777216
net.core.wmem_default=1048576
net.core.wmem_max=16777216
net.core.optmem_max=65536
net.ipv4.tcp_rmem=4096 1048576 2097152
net.ipv4.tcp_wmem=4096 65536 16777216
#
# increase the default 4096 UDP limits
net.ipv4.udp_rmem_min=8192
net.ipv4.udp_wmem_min=8192
#
# Enable TCP Fast Open
net.ipv4.tcp_fastopen=3
#
# Tweak the pending connection handling
net.ipv4.tcp_max_syn_backlog=30000
net.ipv4.tcp_max_tw_buckets=2000000
net.ipv4.tcp_tw_reuse=1
net.ipv4.tcp_fin_timeout=10
net.ipv4.tcp_slow_start_after_idle=0
#
# Change TCP keepalive parameters
net.ipv4.tcp_keepalive_time=60
net.ipv4.tcp_keepalive_intvl=10
net.ipv4.tcp_keepalive_probes=6
#
# Enable MTU probing
net.ipv4.tcp_mtu_probing=1
#
# TCP Timestamps
net.ipv4.tcp_timestamps=0
#
# TCP/IP stack hardening
# TCP SYN cookie protection
net.ipv4.tcp_syncookies=1
#
# TCP rfc1337
net.ipv4.tcp_rfc1337=1
#
# Reverse path filtering
net.ipv4.conf.default.rp_filter=1
net.ipv4.conf.all.rp_filter=1
#
# Log martian packets
net.ipv4.conf.default.log_martians=1
net.ipv4.conf.all.log_martians=1
#
# Disable ICMP redirecting
net.ipv4.conf.all.accept_redirects=0
net.ipv4.conf.default.accept_redirects=0
net.ipv4.conf.all.secure_redirects=0
net.ipv4.conf.default.secure_redirects=0
net.ipv6.conf.all.accept_redirects=0
net.ipv6.conf.default.accept_redirects=0
#
# disable ICMP redirect sending when on a non router
net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.default.send_redirects=0
#
# Enable Ignoring to ICMP Request
net.ipv4.icmp_echo_ignore_all=1

 
Source : https://wiki.archlinux.org/index.php/Sysctl