@Roalnd-Baldin

The 2 hours is probably related to the 3GPP TAU timer, if it expires the device is implicitly released from the network I believe. Which is bad if you have a device that wants to sleep for more than 2 hours. So usually you set this value to whatever is the greatest the network accepts. You can run AT+CEREG=5, AT+CEREG? and check the returned values. It will tell you the timers that are used.

@Wessam Hi, have a look to https://forum.iotcreators.com/topic/626/how-long-does-it-take-that-the-network-detects-a-dead-ip-connection. Maybe it contains some info you are interested in.

Regards, Roland