According to some keepalive settings should be changed to improve reliability - it will enable keep alive functionality (checking if the connection is established and valid) and, by decreasing times and interval - will make detection of broken connections faster.

# sysctl -w net.ipv4.tcp_keepalive_time="60"
net.ipv4.tcp_keepalive_time = 60
# sysctl -w net.ipv4.tcp_keepalive_probes="3"
net.ipv4.tcp_keepalive_probes = 3
# sysctl -w net.ipv4.tcp_keepalive_intvl="90"
net.ipv4.tcp_keepalive_intvl = 90