Some various thoughts on PPP

["Ulrik Mikaelsson" <ulrik mikaelsson gmail com>]

Hi,

First, the mandatory "great product"-line. It really is, your work is
most apprreciated.

Second, I would like to share some thoughts that arrived after
fiddleing with a 3g datacards during the last couple of days.

It all started with me getting a HSDPA high-speed 3g data card from a
friend to try out this monday. While the card itself worked like a
charm, we're planning to purchase some of these and use for a bunch of
users with varying skills in Linux. It's pretty vital to us to have a
simple click-n-connect feature, and so far I've found no such thing
for 3g under Linux. For us, we'll probably solve our immediate need
through a simple connect-script on the desktop of each machine, but as
a more permanent solution, is started looking at extending
NetworkManager with these capabilities.

I immediately discovered the pptp/ppp plugin, (which for some reason
is limited to only pptp by default in Ubuntu Feisty?), and found it to
be rather close to my functional needs. However, i were a bit puzzled
by the approach to hook up PPP-connections under the VPN framework.

While I realize that this is the result of a natural evolution from
the pptp-plugin first being a plain VPN-solution, I started thinking a
little on how exactly I would like it to be solved. Here's what I've
worked up so far, please dig in with your immediate feedback and let's
see what we can iron out.

* PPP-connections should be visualized pretty much like any
connection. For HSDPA and GPRS-connections, signal strength could be
visualized just like the signal strength in wifi-connections.

* PPP-connections should not be automatic fallback-connections, at
least not by default. Many forms of PPP is still charged either by
bandwidth or by connection-time, thus should be a manual choice.

* Some PPP-connections will be only be available when certain hardware
is plugged in, such as a PCMCIA datacard, or an USB-modem.
NetworkManager should be aware of this.

* All PPP-connections require some kind of configuration. In some
cases, the configuration will be dynamic and not possible to determine
before actually trying. For instance PIN-code won't be possible to
forsee without actually asking the card. Also, PIN-code is tied to the
SIM-card, not the datacard, so coupling with the device-identifier is
dangerous. (3 failed attempts and the SIM is locked)
 * Here one thought hit me, most distributions have some kind of
built-in support for network-configuration. Re-using this
configuration, if possible, would avoid duplicating some effort. Also,
I see many bug-report complaining about the lack of support for static
IP:s. There might be an opportunity here.

* There are many kinds of PPP-connections; (not counting PPTP, which
is a VPN-connection and not a base-connection)
 - Plain modem connections, with built-in or hot-attached modems
 - GPRS-connections
  + Through a cellphones, where the mobile unlocks the SIM, connected
either through USB or Bluetooth
  + Through modems, both USB and PCMCIA, here the computer needs to
deal with PIN-codes
  - PPPoE (not sure about how these work, perhaps more tied into the
Ethernet-devices than PPP)

There are a LOT of things to consider with regards to all this, and I
suspect that's why no one have dared to open this can of worms yet.
However, I think at least the GPRS-connections are crucial to make
NetworkManager the swiss army-knife of roadwarriors it's designed to
be.

Please jump in with your thoughts and ideas. I'm planning to attempt
hacking some of this together, but I'd like to get some feedback
first, to ensure I'm right on track. Also, if you're hacking on
something related, please let me know so we don't waste a lot of good
effort.

Regards
/ Ulrik