Kernel tuning for long fat networks

lfn-tcp-cfg.sh

#!/bin/bash

# lfn-tcp-cfg.sh - tune kernel params for better throughput in high-latency situations.
#
#   note that these settings don't persist past a reboot

# SEA <-> ORD has 55-60ms RTT. Assume nominal 65ms and 500mbps available bandwidth
# BDP = B/s * RTT(s)
#     = 500mbps * 65ms
#     = 3.6MB (3,611,111 B) : w/ 1475B MTU, ~2450 packets
#        ^^^^ need to ensure that the kernel can keep this much data in flight

# increase global socket buffer size limits
sudo sysctl -w net.core.rmem_max=16777216
sudo sysctl -w net.core.wmem_max=16777216

# expand TCP socket (R/W) buffer sizes. ("minBytes defaultBytes maxBytes")
sudo sysctl -w net.ipv4.tcp_wmem="16384 4194304 16777216" 
sudo sysctl -w net.ipv4.tcp_rmem="16384 4194304 16777216" 

# increase max queue length, affects traffic IN. (eg, received by NIC prior to kernel)
echo 4000 | sudo tee /proc/sys/net/core/netdev_max_backlog 

# increase transmit queue size. 
sudo ifconfig eth0 txqueuelen 8000 

# flush cached path-discovery settings so these tweaks take effect reliably.
echo 1 | sudo tee  /proc/sys/net/ipv4/route/flush