Hi Dan,

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No, I was thinking of having two full devices, a data channel and a
control channel for devices that really talk AT commands natively.

If the hardware does it great, however for things like a 3G modem you
have the problem that the PPP is over the AT command channel which may
itself be multiplexed. And the muxing in question is *ugly* - sort of
HDLC and LAP-B done wrong.

Well, yes, but we would really like a separate control channel, so we
can query parameters like signal strength, while we do PPP over the data
channel.

we don't want PPP at all. It is just plain stupid and a total braindead
idea. Non of the GSM/UMTS networks talk PPP over the air interface or
actually anywhere in their stack. The PPP is just between the host OS
and the card. It is a pointless encapsulation of IP packets that comes
from the POTS stuff where PPP over a telephone line made sense.

Feel free to convince all the hardware vendors to move over to that
model.  Many of them are, but there are still *boatloads* of devices
that do PPP.  It'll be at least 3 or 4 years before you can even think
about ignoring PPP entirely.

This is totally a firmware thing and not something under our control at
all.  Either the vendor implements a non-PPP data channel, or they
don't.  We have to live with that, or ignore devices that use PPP.  Most
of the devices out there use PPP.  Maybe 80 or 90%.

I know that and it is sad. It is also sad that a firmware upgrade could
bring most cards away from PPP, but besides Option I haven't seen it
from anybody.

The only reason vendors ditched PPP was that it was too much overhead to
achieve full speed on HSDPA 7.2 networks.  Guess how many operators have
actually deployed HSDPA 7.2?  Count them on your hands.  Yes, over the
next year or two we'll see a lot more HSDPA 7.2-capable networks, and
that means more devices will show up that ditch PPP.  But at the moment,
PPP can't be ignored.

Actually HSDPA 7.2 is deployed more than you think. At least in Europe
the base stations in the big cities are 7.2 capable. Some of them even
with proper HSUPA support. It is impressive what you can get through
these networks.

The next problem is that not all vendors implement the non-PPP data
channel using cdc-ether, or provide specs/drivers for that channel.  So
just because a vendor ditches PPP doesn't automatically mean it's better
for Linux and a driver is available.

The CDC Ethernet support of the Ericsson MBM cards is kinda a nice idea.
You get proper IFF_LOWER_UP and can just run DHCP on it. I am not such a
big fan of the DHCP part, but it is the same for WiMAX, so I assume that
is what they will be settling for. Nice would to have just plain and
simple IPv6 on UMTS networks.

Regards

Marcel