In case of high latency link, a too small initcwnd could degrade performance, as it may take a while for throughput to increase to its maximum.

Increasing initcwnd could mitigate this a bit.

Major CDNs are also using a custom initcwnd for better performance.

I used a script from serverfault, did some minor changes, and put it into /etc/network/if-up.d/initcwnd to persist the change:

#!/bin/bash
set -e

DEFAULT_ROUTE=`ip route | grep "^default" | head -1`
if [ ! -z "$DEFAULT_ROUTE" ]; then
    ip route change $DEFAULT_ROUTE initcwnd 64
fi

Don’t forget to chmod +x it to make it executable.

The change could be verified by:

# ip route show
default via 10.0.0.1 dev eth0  initcwnd 64