Re: Extending the mobile-broadband-provider-info database

[Marcel Holtmann <marcel holtmann org>]

Hi Dan,

> > >>> As long as the attributes we add aren't required, it should be fine to
> > >>> add them.  See the balance check stuff that was added a while ago; that
> > >>> was added in a compatible manner and existing tools simply ignore the
> > >>> new attributes.
> > >>>
> > >> About the existing information there. I see it is mobile network 
> > >> identifiers, but I haven't seen that Network manager exploit this to 
> > >> automatically select or propose the correct network settings. Is this 
> > >> not implemented yet?
> > > It's done in the client applications like nm-applet and
> > > nm-connection-editor and the KDE bits, which create the actual
> > > configuration and display stuff like signal and network names.  NM
> > > simply passes the mobile broadband specific configuration along to
> > > ModemManager, but isn't itself involved at all with the carrier/APN
> > > selection.  nm-applet also makes use of the database to pull out a
> > > carrier name based on MCC/MNC/SID if the modem doesn't one.
> > 
> > Okay, I just haven't seen it happen in nm-applet. I always have had to
> > select country and then operator/subscription.
> 
> nm-applet doesn't yet pull the operator MCC/MNC out of the sim (and in
> fact, lots of devices don't allow this for some reason, nothing to do
> with the SIM, but the device).  But nm-applet *does* use the database
> for the selection dialog you're talking about, and it uses the database
> for dispalying the operator name in the menu if the device doesn't
> provide one.  It also uses it to show the CDMA operator name (based on
> SID) if you're using a CDMA device.  So quite a few things at the
> moment.

actually all devices allow you to read the MCC/MNC from the SIM card.
The MCC is the first 3 bytes of your IMSI. And the MNC follows the MCC.
The only tricky part is that the MNC can be 2 or 3 digits. And to know
what it actually is, you need to read the MNC length from the SIM card.
You do need proper EF reading for that.

The only problem is that you need to tweak the EF reading for some older
devices since it seems that it has not been tested enough for the data
dongles. Most likely that is a Qualcomm problem since we only saw issue
with it on old dongles using Qualcomm chips and thus most likely their
AT command implementation.

Using the database for displaying the operator name is also wrong. At
least for GSM. You need to use the SPN value from the SIM card for this.
In addition you need to let the firmware handle NITZ updates. Operator
names can change on the fly and can be changed by the network.

That is another reason why having the SPN values also in the database.
That way we can correctly identify MNVO which just share MCC/MNC with
the actual network operator.

Some devices have special AT commands for reading the SPN, but you can
access it via EF from the SIM card as well.

Regards

Marcel