Modem-/NetworkManager support for modems not using PPP

[Marius Kotsbak <marius kotsbak gmail com>]

Hi!

There seems to be now quite a bit of modems appearing now that does not
support the old method of using PPP protocol on the same tty device as
the AT commands are sent, or it is not recommended for higher HSPA+ and
LTE modems because of performance limitations of the PPP/tty layer.
Those devices typically accept AT commands at one interface and use
another interface for the network traffic (including first a DHCP query).

One example is the Samsung GT-B3730 I'm currently developing drivers for:

https://github.com/mkotsbak/Samsung-GT-B3730-linux-driver

It seems to be the same case for LG VL600 4G (LTE):

http://ubuntuforums.org/showpost.php?p=10589647&postcount=17

https://github.com/balrog-kun/LG-VL600-utils

The Ericsson Mobile Broadband Modules (I have an F5521gw based modem)
seems to offer both the old ACM ports and support USB WCM / CDC NCM /
CDC Ethernet protocols for higher performance:

http://www.thinkwiki.org/wiki/Ericsson_F3507g_Mobile_Broadband_Module#Connecting_to_the_net_via_CDC_Ethernet_interface

http://sourceforge.net/apps/mediawiki/mbm/index.php?title=MBM#Prerequisites

http://cateee.net/lkddb/web-lkddb/USB_NET_CDC_NCM.html

I wonder if support for this has been implemented or thought about in
Modem-/NetworkManager. We probably need a flag for a modem manager
module to tell that it does not use PPP and require to get IP address
using DHCP instead.

Else those devices benefit from the code in modem manager (and should be
classified as such to the user as well), like the PIN unlocking, signal
strength (typically found on the same device as dialling happened, since
network traffic flow on a separate interface)  etc. The configuration
tab for PPP could be hidden for those devices. For devices offering
multiple ways to connect, the modem manager module should probably find
the best performing according to the available kernel modules and use
that method.

--
Marius Kotsbak