Why do we need to set the APN manually for certain providers?

Scott Lemon slemon at twilio.com
Mon Nov 7 15:26:36 UTC 2022


I hadn't realized that you had this list:

>> There is also an open source database we maintain in

>> https://gitlab.gnome.org/GNOME/mobile-broadband-provider-info but
>> which also has the same problems, it lacks a lot of latest updates
>> even from major carriers.

It appears that you are matching on the MCC and MNC?  Are you using this
from the prefix of the IMSI?

If so, what do you do to match for MVNOs that share IMSIs from the same
IMSI Sponsors?

With Android they also support a richer matching algorithm that includes
things like the MVNO Type and Value
that can then be read from the SIM to differentiate - for example the
Service Provider Name (SPI).

Do you support anything like this in this file format?

Scott C. Lemon
Principal IoT Solutions Engineer


Mobile: +1 (801) 336-4476
Email:   slemon at twilio.com

On Mon, Nov 7, 2022 at 8:53 AM Aleksander Morgado <aleksandermj at chromium.org>

> Hey,
> > My company produces a device with the Sierra EM7565 Modem and we have
> encountered problems related to the APN setting. (A collegue of mine sent a
> message into this list a week ago and has received kind help by Aleksander
> Morgado whom I'd like to thank.)
> >
> > We observed the following:
> >
> > * When using a German Vodafone SIM card in Germany, 3GPP registration
> remains at `idle`.
> > * When using a German O2 SIM card in Germany, 3GPP registration advances
> to `home` instantly.
> > * With the Vodafone SIM card, only after running `qmicli -d
> /dev/cdc-wdm0 -p --wds-modify-profile="3gpp,1,apn=web.vodafone.de,username=,password="`,
> ModemManager can connect and registration advances to `home`.
> > * In contrast to that, when using the Vodafone SIM card in one of our
> private smartphones, no manual APN setting was necessary.
> >
> That is because Vodafone DE requires a specific set of APN settings
> during *registration* (initial EPS bearer settings, a.k.a. attach
> APN). If the modem doesn't provide the exact settings required, the
> operator may reject the registration to the network (so will remain in
> idle).
> > I'm trying to understand why our device ran into the issues described
> while 3rd party smartphones do not.
> >
> > I searched the internet for a bit and learned that Google is maintaining
> a list linking the network carriers with APNs. Is this the correct way to
> go? Does everyone producing GSM enabled devices (that is, us too) need to
> equip their devices with that list as a lookup table? Does that list work
> with Roaming, too? I guess an alternative would be to prompt the user for
> the APN, like in the old times. But still, if APNs need to be set
> explicitely then I don't understand why it worked with O2 instantly.
> >
> It worked in O2 because operators may decide to not be strict in the
> initial APN requirements. Passing the empty APN during registration
> would allow the modem to say "I want to register, I don't know what
> APN settings should I use" and the network would then say "nevermind,
> you can register, here are the APN settings that should be considered
> during registration". There are nicer cases even, e.g. with Movistar
> Spain I can request whatever APN I want as initial, and it will work
> (for now it does work, that is).
> Google and other big manufacturers keep their own lists of APNs to
> autodetect what should be using. This is a huge task, and not even
> Google has "the latest and greatest", the list changes continuously.
> There is also an open source database we maintain in
> https://urldefense.com/v3/__https://gitlab.gnome.org/GNOME/mobile-broadband-provider-info__;!!NCc8flgU!evTK7uUD76LF1mTFCb2pd-4DyYWVxMc8a2kp8lNeu8rJ4eVscqlootuJ1601WU3CgkiMMTEhUDLVsnSiJ6M-2Xw$
> but
> which also has the same problems, it lacks a lot of latest updates
> even from major carriers. For modems in the US, there are also
> carrier-certified firmwares that come with predefined settings,
> including custom APN settings required.
> --
> Aleksander
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