Fix it on Linux by enabling BBR TCP congestion control.

  cat << EOF >> /etc/sysctl.conf
  net.core.default_qdisc=fq
  net.ipv4.tcp_congestion_control=bbr
  EOF
  sudo sysctl -p

1. You will need a recent kernel.

2. net.ipv4.tcp_congestion_control=bbr applies to IPv6 too.

3. You must set the queuing discipline to fq or it won't work.