# Default: cubic
net.ipv4.tcp_congestion_control=htcp

# CoDel (Default: pfifo_fast)
# https://lwn.net/Articles/616241/
net.core.default_qdisc=fq_codel

# Default: 32768 60999
net.ipv4.ip_local_port_range=1025 65535

# TCP window scaling tries to avoid saturating the network adapter with
# incoming packets.
net.ipv4.tcp_window_scaling = 1

# If enabled, assume that no receipt of a window-scaling option means that 
# the remote TCP is broken and treats the window as a signed quantity.  If 
# disabled, assume that the remote TCP is not broken even if we do not 
# receive a window scaling option from it.
net.ipv4.tcp_workaround_signed_windows = 1

# RFC 1337, TIME-WAIT Assassination Hazards in TCP, a fix written in 1992
# for some theoretically-possible failure modes for TCP connections. To 
# this day this RFC still has people confused if it negatively impacts
# performance or not or is supported by any decent router. Murphy's Law is
# that the only router that it would even have trouble with, is most likely
# your own.
net.ipv4.tcp_rfc1337 = 1

# TCP SACK and FACK refer to options found in RFC 2018 and are also
# documented back to Linux Kernel 2.6.17 with an experimental "TCP-Peach"
# set of functions. These are meant to get you your data without excessive
# losses.
net.ipv4.tcp_sack = 1
net.ipv4.tcp_fack = 1

# RFC 2923 IPv6 uses PMTU by default to avoid segmenting packets at the
# router level, but its optional for IPv4. PMTU is meant to inform routers
# of the best packet sizes to use between links, but its a common admin
# practice to block ICMP ports that allow pinging, thus breaking this
# mechanism. Linux tries to use it, and so do I: if you have problems, you
# have a problem router, and can change the "no" setting to 1. "MTU probing"
# is also a part of this: 1 means try, and 0 means don't.
net.ipv4.ip_no_pmtu_disc = 0
net.ipv4.tcp_mtu_probing = 1

# Don't ignore ICMP
net.ipv4.icmp_echo_ignore_all=0
net.ipv4.icmp_echo_ignore_broadcasts=0

# Netflix 2014 EC2 sysctl tweaks
# http://www.slideshare.net/AmazonWebServices/pfc306-performance-tuning-amazon-ec2-instances-aws-reinvent-2014
net.core.somaxconn=1000
net.core.netdev_max_backlog=5000
net.core.rmem_max=16777216
net.core.wmem_max=16777216
net.ipv4.tcp_wmem=4096 12582912 16777216
net.ipv4.tcp_rmem=4096 12582912 16777216
net.ipv4.tcp_max_syn_backlog=8096
net.ipv4.tcp_slow_start_after_idle=0
net.ipv4.tcp_tw_reuse=1