Can't change the tcp congestion control algorithm

Question

So, I have a computer networking lab tomorrow which requires me to set my computers TCP congestion control algorithm to reno. It's cubic by default. I understand it should be done like this from root:

echo reno > /proc/sys/net/ipv4/tcp_congestion_control

However, after restarting my computer the tcp_congestion_control algorithm is again cubic. Looking at tcp_available_congestion_control and tcp_allowed_congestion_control, both cubic and reno are there. I'm running Ubuntu 16.04 Linux 4.4.0-128-generic.

Answer 1

Run, with root privileges:

sysctl net.ipv4.tcp_congestion_control=reno

If this doesn't work, change /etc/sysctl.conf appending the line:

net.ipv4.tcp_congestion_control=reno

To it. This file contains kernel parameters that are changed with sysctl after you boot your computer.