I realized the sshd installed onto ubuntu server 12.04 LTS does not have session timeout, once login via ssh user can stay in the remote console for unlimited amount of time.
I checked the configuration file in
/etc/ssh/sshd_config and realized there is no parameter for session time out, I used
man sshd_config and realized there is actually this parameter:
ClientAliveInterval Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a message through the encrypted channel to request a response from the client. The default is 0, indicating that these messages will not be sent to the client. This option applies to protocol version 2 only.
I may have to add this manually and restart the sshd.
#Session timeout ClientAliveInterval 600