# Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and
# sysctl.conf(5) for more details.

# Controls IP packet forwarding
net.ipv4.ip_forward = 0

# Controls source route verification
#net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.all.rp_filter = 2

# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0

# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 0

# Controls whether core dumps will append the PID to the core filename.
# Useful for debugging multi-threaded applications.
kernel.core_uses_pid = 1

# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1

# Disable netfilter on bridges.
#net.bridge.bridge-nf-call-ip6tables = 0
#net.bridge.bridge-nf-call-iptables = 0
#net.bridge.bridge-nf-call-arptables = 0

# Controls the default maxmimum size of a mesage queue
kernel.msgmnb = 65536

# Controls the maximum size of a message, in bytes
kernel.msgmax = 65536

# Controls the maximum shared segment size, in bytes
kernel.shmmax = 68719476736

# Controls the maximum number of shared memory segments, in pages
kernel.shmall = 4294967296

kernel.sem = 250 32000 100 128
fs.file-max = 131072

# Disable IPv6
#net.ipv6.conf.default.disable_ipv6 = 1
#net.ipv6.conf.all.disable_ipv6 = 1

###
### TUNING NETWORK PERFORMANCE ###
###

# For high-bandwidth low-latency networks, use 'htcp' congestion control
# Do a 'modprobe tcp_htcp' first
net.ipv4.tcp_congestion_control = htcp

# For servers with tcp-heavy workloads, enable 'fq' queue management scheduler (kernel > 3.12)
#net.core.default_qdisc = fq

# Turn on the tcp_window_scaling
net.ipv4.tcp_window_scaling = 1

# Increase the maximum total buffer-space allocatable
# This is measured in units of pages (4096 bytes)
net.ipv4.tcp_mem = 65536 131072 262144
net.ipv4.udp_mem = 65536 131072 262144

# Increase the read-buffer space allocatable
net.ipv4.tcp_rmem = 8192 87380 16777216
net.ipv4.udp_rmem_min = 16384
net.core.rmem_default = 131072
net.core.rmem_max = 16777216

# Increase the write-buffer-space allocatable
net.ipv4.tcp_wmem = 8192 65536 16777216
net.ipv4.udp_wmem_min = 16384
net.core.wmem_default = 131072
net.core.wmem_max = 16777216

# Increase number of incoming connections
net.core.somaxconn = 65535

# Increase number of incoming connections backlog
net.core.netdev_max_backlog = 65536
net.core.dev_weight = 64

# allow more SYN requests to be queued
net.ipv4.tcp_max_syn_backlog = 65536

# Increase the maximum amount of option memory buffers
net.core.optmem_max = 65536

# Increase the maximum number of skb-heads to be cached
#net.core.hot_list_length = 1024

# Increase the tcp-time-wait buckets pool size to prevent simple DOS attacks
net.ipv4.tcp_max_tw_buckets = 1440000

# try to reuse time-wait connections, but don't recycle them if using a LB (can break clients behind NAT)
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1

# Limit number of orphans, each orphan can eat up to 16M (max wmem) of unswappable memory
net.ipv4.tcp_max_orphans = 16384
net.ipv4.tcp_orphan_retries = 0

# Increase the maximum memory used to reassemble IP fragments
net.ipv4.ipfrag_high_thresh = 512000
net.ipv4.ipfrag_low_thresh = 446464

# don't cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1

# Increase RPC slots
#sunrpc.tcp_slot_table_entries = 32
#sunrpc.udp_slot_table_entries = 32

# Increase size of RPC datagram queue length
net.unix.max_dgram_qlen = 50

# Don't allow the arp table to become bigger than this
net.ipv4.neigh.default.gc_thresh3 = 2048

# Tell the gc when to become aggressive with arp table cleaning.
# Adjust this based on size of the LAN. 1024 is suitable for most /24 networks
net.ipv4.neigh.default.gc_thresh2 = 1024

# Adjust where the gc will leave arp table alone - set to 32.
net.ipv4.neigh.default.gc_thresh1 = 32

# Adjust to arp table gc to clean-up more often
net.ipv4.neigh.default.gc_interval = 30

# Increase TCP queue length
net.ipv4.neigh.default.proxy_qlen = 96
net.ipv4.neigh.default.unres_qlen = 6

# Enable Explicit Congestion Notification (RFC 3168), disable it if it doesn't work for you
#net.ipv4.tcp_ecn = 1
#net.ipv4.tcp_reordering = 3

# How many times to retry killing an alive TCP connection
#net.ipv4.tcp_retries2 = 15
#net.ipv4.tcp_retries1 = 3

# Avoid falling back to slow start after a connection goes idle
# keeps our cwnd large with the keep alive connections (kernel > 3.6)
#net.ipv4.tcp_slow_start_after_idle = 0

# Allow the TCP fastopen flag to be used, beware some firewalls do not like TFO! (kernel > 3.7)
#net.ipv4.tcp_fastopen = 3

# This will enusre that immediatly subsequent connections use the new values
net.ipv4.route.flush = 1
#net.ipv6.route.flush = 1

# SACKs (Selective Acknowledgments) are an optimisation to TCP which in normal scenarios improves considerably performance. In Gigabit networks with no traffic competition these have the opposite effect. To improve performance they should be turned off by:
#net.ipv4.tcp_sack = 0
# Reduce keepalive interval
net.ipv4.tcp_keepalive_intvl = 15
net.ipv4.tcp_keepalive_probes = 5
net.ipv4.tcp_fin_timeout = 15

# as many local socket ports as we can get
net.ipv4.ip_local_port_range = 11000 65535

# Increase connection track limits and bucket size
net.netfilter.nf_conntrack_max = 1048576
#net.netfilter.nf_conntrack_buckets = 131072 # See /etc/rc.local
net.netfilter.nf_conntrack_generic_timeout = 120
net.netfilter.nf_conntrack_tcp_timeout_established = 54000

net.ipv4.tcp_timestamps = 0

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1