topic Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly in Archived Posts

Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Wed, 17 Nov 2021 16:30:57 GMT

I have the Xiaomi 11T Pro on an EE monthly SIM. All works great except for Wi-Fi calling.

Wi-Fi calling will connect back to EE servers but at exactly 50 minutes (that time span must mean something to someone technical) since connecting it drops the connection. The phone reconnects itself after 10 or 15 seconds, only to drop again 50 minutes later.

I can monitor this on my router in real time and see the connection on port 4500 to EE drop at the point it starts exchanging ISAKMP packets for CREATE_CHILD_SA.

The same SIM in other Android devices will connect to Wi-Fi calling for tens of hours. I've a second device connected to EE and can watch that remain connected whilst the Xiaomi drops.

Suffice to say if I'm on a call at that 50 minute boundary the call drops.

I had a similar issue with a Pixel 2 XL started dropping the connection every 25 minutes exactly which was eventually fixed by EE.

I would be very grateful if this could be passed to someone in the tech team perhaps. I can provide packet capture logs if that helps. Of course it may well be a problem with the Xiaomi. I'm probably not alone with this issue with these devices but most people will just think it is a random drop without realising it is always on 50 minute boundaries.

Many thanks.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

Northerner — Wed, 17 Nov 2021 21:44:51 GMT

Hi @PhilipL

I would suggest posting on the Xiaomi forums for help

https://xiaomi.eu/community/

Thanks

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

EssexBoyEE — Wed, 17 Nov 2021 21:54:24 GMT

Check your Battery Savings Settings or any Apps you have related to save Battery, also check, although probably unrelated if it's exactly 50mins, that your phone Signal isn't jumping between 5G / 4G or even 3G, or switch off 5G off on the Phone, is it still the same.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Thu, 18 Nov 2021 08:34:42 GMT

@Northerner Thanks, and I've added a post there to see if they modify any of the related code from the stock ROM to see if it is worth trying (requires unlocking as the ROMS are no official and they aren't Xiaomi).

I've raised a ticket in the device itself but had, rather unsurprisingly, have yet to get a response. As I had exactly the same issue (but 25 minute drops and not 50) start on a Pixel device which then got fixed by some changes at EEs side, I thought it was worth raising the issue here.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Thu, 18 Nov 2021 09:37:37 GMT

@EssexBoyEE Yes I've checked out the battery settings. However this happens when the device is plugged in and charging (when battery management is not in play), and it happens in airplane mode (so no mobile signal at all). I've also continually pinged the phone and no packets are lost over that 50 minute boundary to suggest it is a connectivity problem over Wi-Fi.

It seems to be at the point the established VPN used by Wi-Fi calling needs to refresh the connection/security keys, and at that point it fails.

I've tried looking in the Android logs of the phone but it doesn't show any information to what the error is at that 50 minute mark, all it shows is an event from a qualcomm driver saying the connection is down, and then the logs are just full of IMS closing messages and then IMS messages about creating a new connection, and the 50 minute cycle continues.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Wed, 24 Nov 2021 08:27:18 GMT

Just to add to this in case anyone is having a similar issue and wonders if trying a different ROM would help. I've wiped and tried the Global ROM from Xiaomi and that has exactly the same issue of disconnecting every 50 minutes.

I've also raised this with Xiaomi but no response after a couple of weeks.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

James_B — Wed, 24 Nov 2021 08:34:41 GMT

Hi @PhilipL,

I'd recommend getting in touch with Customer Care so our Tech Gurus can run through some diagnostics with you and raise a support ticket from their end if needed.

They'll be happy to help. 🙂

James

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Wed, 24 Nov 2021 09:48:13 GMT

@James_B Many thanks, have been on chat but they said as they don't sell these phones they can't do a lot and I should be grateful it works for 50 minute stints 🙂

They have reset some network settings and I received a text message to say reboot the phone so we'll see if that has done anything.

I had a Pixel 2 XL that would disconnect every 25 minutes after it had been working for some time okay on EE, which I raised with tech and eventually it was fixed from EEs side, and this new one happens to be 50 minutes, coincidentally 25 x 2. I'm fortunate as I've got a router where I can easily filter and see the ongoing VPN connection on port 4500 and so see it is dropping every 50 minutes, however most people with the same issue will just chalk it up to Wi-Fi calling being unreliable, which is a shame as when it is working without such issues it is pretty good.

We will see how it goes, perhaps a technician will notice in the logs there are a number of devices dropping regularly and then connecting back up and a fix will be implemented.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

James_B — Wed, 24 Nov 2021 09:57:08 GMT

No problem @PhilipL

Please keep us updated.

James

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Wed, 24 Nov 2021 10:24:18 GMT

Just a quick update, the reset network settings I received did not fix the issue, with a drop again at exactly 50 minutes.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

James_B — Wed, 24 Nov 2021 10:55:40 GMT

Thanks for letting us know @PhilipL

Please get back in touch with Customer Care so our Tech Gurus can escalate this for you.

James

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Wed, 24 Nov 2021 11:10:48 GMT

@James_B They said because it isn't a device they sell or sold they wouldn't be able to look into it, and the resetting of the network settings on my account was just a finger in the air lets give it a go type of thing.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

James_B — Wed, 24 Nov 2021 11:39:33 GMT

Hi @PhilipL,

It sounds like they think it's a software issue, rather than network. I'd recommend contacting the manufacturer directly for support.

James

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Fri, 24 Dec 2021 15:37:00 GMT

So I've been doing some debugging and investigation into this 50 minute drop, this possibly affects a lot of devices using standard Qualcomm supplied modem configuration binaries as I've seen the same settings in many modem.bin files for different manufacturers on Qualcomm phones.

The issue is the settings in the /modem_pr/mcfg/configs/mcfg_sw/generic/EU/EE/Commercial mcfg_sw.mbn file, this has various configuration settings but the ones in question are in the XML for <IWLAN_S2B_CONFIG>.

There are two elements in this XML file called <esp_rekey_time> and <ikev2_sa_rekey_timer>, the esp_rekey_timer is set to 3000 seconds for soft and 3600 for hard. Now 3000 seconds is 50 minutes!

At the 50 minute mark the initial keys are exchanged for new ones, this is failing, I think because no group or hash algorithms are in this configuration file (they are in other carrier configuration settings).

A work around I have tested is to simply set these timeout values both to soft:64800/hard:64900 (as seen in other operator config files, e.g. Vodafone), this means the initial keys will last around 45 days, in other words under normal usage the Wi-Fi calling VPN will never get to that age as the connection is dropped and reset on moving around and leaving the Wi-Fi network, but now it will no longer drop every 50 minutes as it never attempts to 'rekey' and so fail. However to implement these changes requires a rooted device and a Qualcomm PST debug port enabled, along with the Qualcomm PST software.

I hope this information can be fed back to the network team who may be able to get Qualcomm to update their standard operator settings, either using the large timeout value or fixing the issue why the rekey fails.

At least now I have VoWiFi working and not dropping.

Re: Xiaomi 11T Pro - Wi-Fi calling disconnects every 50 minutes exactly

PhilipL — Sun, 26 Dec 2021 10:29:52 GMT

Just an update to previous post. My calculation on extending the seconds to a larger value was wrong, as its not 50 days but just 18 hours before it times out! So the VPN Wi-Fi calling connection dropped after 18 hours, but considerably better than 50 minutes.

So I've gone back to his and have now successfully added in the missing settings, so when it times out the keys are successfully renewed as intended and the connection remains up.

For some reason EE have quite short time outs between creating new keys compared to other operators which all seem to be > 18 hours. I suspect the rekey values might be quite low as EE was one of the first operators to get Wi-Fi calling and perhaps these were early test configurations that got added as standard to Android that have never been updated?