EC2 instance SSH timeout prevention – keep SSH sessions alive

Question

After some times the server disconnects me with the error:

packet_write_wait: Connection to 52.211.168.17 port 22: Broken pipe

I use the default Unix SSH client (Ubuntu 16.04). On the server side (Ubuntu 16.04), I configured ~/.ssh/config:

ServerAliveInterval 120

and /etc/ssh/sshd_config:

ClientAliveInterval 120
ClientAliveCountMax 720

I restarted the SSH service and server, but the changes didn't take effect. Can it be Amazon specific? How can I resolve it?