How long does it take that the network detects a dead IP connection?

Roland Baldin

Hi guys,

I made some test to the automatic release of IP addresses by the network.

With the “Tuino096 - Quectel BG96” I attached to the network with the following AT commands:

AT+CGDCONT=1,“IP”,“cdp.iot.t-mobile.nl”
AT+COPS=1,2,“26201”,9
AT+CGPADDR
+CGPADDR: 1,10.0.4.102

As a Telekom employee I am in the lucky situation that I can check the IP status of the device via some monitoring systems. Of cause I could see that the my device with its IMEI and IMSI got assigned the IP address 10.0.4.102.

After this I just unplucked my device from power and checked the IP connection status of the IMEI.
It took about ca. 2 hours the DCD of the network recognized that the device is dead and release the IP address to be used again by other devices.
I repeated this test a few times and I could reproduce the 2 hours.

BUT if I power up the device after I swiched it off and attach it bag to the network the network detects the same IMEI and IMSI requires a new IP. By this the provious IP is released immediately and a new IP is assigned to the device.

Hope this info helps you a bit to get a better understanding what is going on in the network.

Cheers, Roland

Wessam

Dear Roalnd,

thanks for making a test scenario of DCD function, but let me explain my scenario on EC21-E TE-A connected to UMTS&LTE EVB Kit and using Telekom SIM card. after registering on the Network and activate the PPP connection then i get DCD on, after that i disconnected the Antenna and wait for 24 hours the DCD remain On.

Best Regards
Wessam

Stefan de Lange

@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.