ESM Error Code 50: type ipv4 only allowed (NRF91 Asset Tracker)

[Dominic]

Hi 

I am a bit stuck on this one. 

Hardware: NRF91 Thingy, NRF91 DK

Firmware: Asset Tracker with latest MFW v1.3.5

I have been connecting with 1oT SIM using NRF91Thingy and DK perfectly for the last 4 months - and it is usually the O2 cell tower (LTE-M Roaming) as there is no other tower nearby. I left it attached and logging on October 22nd 2023 and a few hours later disconnected, I have not been able to connect since. Every time I connect, or use AT+COPS it attaches then immediately detached with ESM 50 code - (PDN type IPv4 only allowed). I have contacted 1oT and they haven't reported anything with O2 network.

Modem trace as follows:

%CESQ: 32,1,16,2
+CEREG: 2,"02D0","07F87C78",7
+CSCON: 1
%CESQ: 33,1,9,1
%CESQ: 33,1,14,2
[00:00:01.534,149] <inf> app_event_manager: DATA_EVT_CONFIG_INIT
[00:00:01.935,821] <inf> app_event_manager: MODEM_EVT_LTE_CELL_UPDATE
+CGEV: ME PDN ACT 0,0
+CNEC_ESM: 50,0              <------- Error Code
%MDMEV: SEARCH STATUS 2
+CEREG: 5,"02D0","07F87C78",7,,,"11100000","11100000"
+CGEV: NW DETACH             <------- Detach
+CGEV: ME PDN DEACT 0
+CEREG: 2
%CESQ: 35,1,19,2

I have never seen this issue before and nothing has changed in the firmware since I started logging started. 1oT assume its hardware/firmware related - and suggested I changed the PDN context to use IPv4 only, same result. I also switched to IPv6, it gives a EMM 15 error in that case. We can connect to Vodafone just fine, but it is quite low signal, either way O2 has always been the closest and the best to connect to. 

Has anyone had similar issues? 

[Dominic]

an update to this, I have Wireshark installed and I am now reviewing the modem traces. I had it all wrong, it's not the network detaching the NRF91, but the NRF91 is requesting a detach!

NAS EPS session management messages: Activate default EPS bearer context request (0xc1)

NAS EPS session management messages: Activate default EPS bearer context accept (0xc2)

DLInformationTransfer, Ciphered message  <<---- Not sure what this is

NAS EPS Mobility Management Message Type: Detach request (0x45)

NAS EPS Mobility Management Message Type: Detach accept (0x46)

Cause: No Suitable Cells In tracking area (15)

Duration about 1second! 

So NRF91 is detaching for some reason, I don't know if that ciphered message has anything to do with it, for some reason it doesn't think that cell is suitable anymore. I need to dig more to why, 

Thanks for anyone following...

[Dominic]

Looks like there is a similar question/issue here:  Can't add dev kit to nRF cloud 

I have my trace here for more debug. 

Summary:

• We have been able to connect to O2/Telefonica via iBasis/1oT SIMs up until 22nd October 2023
• After that,  our devices attach with PDN request (IPv4 only) , all gets accepted by the cell, then the NRF91 requests a detach almost immediately with EMM 15 (No suitable cells in the tracking area). This cell has been suitable in the past. 
• This happened to all our devices and dev kits in separate locations.  
• Around October 22nd, I noticed that the status from O2 said there was a problem with a cell in my area, but then that cleared to OK.  
• We can still attach to Vodafone on the same SIMs no problem. 
• Happens on mfw 1.3.4 and mfw 1.3.5, on NRF91.Thingy,  DK, and our own hardware. Using SLM, Asset Tracker v2, and our own firmware. 
• This appears to happen in the modem firmware, because we see no other messages in the debug logs other than the unsolicited messages we get back about the detach. 

I will keep digging while I wait for some help. 

Many thanks

3568.trace-2023-10-28T15-41-10.945Z.mtrace  

[JONATHAN LL]

Hi,

I would recommend that you contact O2 and ask about their policy on rooming SIM cards, they have recently introduces some changes that effect roaming. 

Regards,
Jonathan

[Dominic]

I’ve already contacted 1oT who provide our SIMs and they said they were not aware of any changes or issues, they told me to “restart the device” lol. Just to note this is also happening in the iBasis SIMs that come with the DKs and thingys. 

Are you able to share what changes that O2 have made and any links to this information? I’ve searched everywhere for any information on changes to their network. 

However, if you look at the modem trace, it’s not the network that’s detaching the modem, the modem is detaching itself. The LTE is fully accepting the attach and providing all the APN details, IP addresses, etc. Is there something in the the trace that’s suggesting roaming isn’t allowed, because we have devices with UBLOX modules that are roaming fine in the O2 network.

I will keep pushing 1ot for more information, but if there is something in the traces that I gives a reason I and share with them. Also if your can give me the  links to what O2 have changed that would be much appreciated. 

thanks  

[Dominic]

I’ve found one linked in post that suggest that O2 have shutdown their LTE network for roaming. 

this is not good news, but I imagine it’s a problem for iBasis sims too?