enable Packetization Layer Path MTU Discovery (PLPMTUD) as per RFC4821 in vanilla
it improves MTU path discovery as it
resolves many of the robustness problems of the classical techniques since it does not depend on the delivery of ICMP messages.
It is most beneficial whit device MTU set to support jumbo frames (> 1500)
patch "/etc/sysctl.conf" with
net.ipv4.tcp_mtu_probing = 1