This policy setting allows you to specify the time interval between keepalive packets. The value is specified in seconds. ...

"This policy setting allows you to specify the time interval between keepalive packets. The value is specified in seconds. You can specify a value of up to 604800 seconds.  If you do not define this policy setting, the default value is 0 (zero), which allows the device to detect the optimal time interval and use it.  If you specify 0 seconds, the device detects the optimal keepalive time interval and uses it.  Note: Setting the value too low causes increased data traffic and decreased battery life on the device. If the value that is too high, the Mobile VPN can become disconnected, which then requires reconnections."