Im using Amazon Linux, [davea@mymachine ~]$ uname -aLinux mymachine.mydomein.org 4.4.35-45.83.amzn1.x86_64 #1 SMP Wed Jul 27 22:37:49 UTC 2016 x86_64 x86_64 x86_64 GNU/LinuxIn my /etc/ssh/sshd_config, I have no value set for ServerAliveInterval.  In this answer  What options `ServerAliveInterval` and `ClientAliveInterval` in sshd_config exactly do? , they say Setting a value of 0 (the default) will disable these features so your connection could drop if it is idle for too long.  What does that mean?  In precise terms, what is the default amount of time the connection will stay alive if this parameter is committed?  Assume that I have set a value of 1000000000000 on the client side.
What is default value of ServerAliveInterval?
ssh;configuration;sshd;timeout
The value for ServerAliveInterval means that if no data has been received from the server within this time then send a NULL message to the server.Similarly, ClientAliveInterval means that if no data has been received from the client within this time then send a NULL message to the client.The default values are typically 0 which means these functions are disabled.The main use of this is to prevent intermediate routers and firewalls from thinking a session is idle, and dropping it.  It has no real impact on an ssh server, itself.For example, many home NATting routers will drop idle sessions after a period of time (the exact time depends on your router; I've seen values from 1 hour to over 21 days).  By setting the ServerAliveInterval you fake out this idle timeout in the router by making sure there's always some traffic within the router interval.